SEDCAD™ 4 r r for Windows® 95/98/NT/2000/Me/XP

. ,-.

,.... ,.... ,.... r ,....

Design Manual And

User's Guide

1: :'J" '! '."- '---:;;:-;;-'I " j' c'.

'~~~7?"~~:ii,~: . , .. ,.:' 1' ....

"'1" <""

Dr. Richard C. Warner University ofKentucky

Biosystems and Agricultural Engineering Department Cooperative Extension Service

Ms. Pamela J. Schwab Civil Software Design

Mr. Dennis J. Marshall, AlA

2

Information in chis document is subjecr ro change without notice. Names and data used in examples are ficririous unless orherwise no red. The SEDeAD'"" sorrware has been copyrighred by Pamela]. Schwab, and rhe SEDCAD Design Manual and User', Guide has been copyrighred by Richard C. Warner, «.al., wirh all rights resc:cved. The software described in (his manual is furnished un­dee a license agreement oc nondisclosure agreement. A condirion of insralling [he software is your agreement ro [he written license agreemenr, displayed dur­ing che installation procedure. Your righrs ro license che SEDeAD program are limired [Q rhose expressly provided in che written license agreement. Uncier copyright laws, neirher [he documenration flor the software may be copied, phmocopied. reproduced, rranslated, oc reduced ro any electronic medium oc machine readable form, in whole or in part, without the prior written consenr of rhe author(s).

SEDCAD 4 for Windows Design Manual and User's Guide Copyrighr © 1998. Richard C. Warner, Pamela]. Schwab, and Dennis]. Mar­shall. AH righrs reserved.

SEDCAD 4 for Windows (compurer sofrware) Copyrighr © 1998-2010. Pamela]. Schwab. AlI righrs reserved

SEDCAD is a U.S. rrademark ofCivil Sofrware Design.

Microsoft Windows is a U.S. registered trademark ofMicrosoft 'Corporarion.

Civil Sorrware Design, Augusr 1998

2nd prinring - Ocrober 1998

3rd prinring - Augusr 1999

4rh prinring - April 2001

5rh prinring - ]anuary 2004

6rh prinring - November 2006

7th prinring - December 2008

8th prinring - Seprember 2010

r r

r r

,.....

3

Contents

Acknowledgemenrs ................ ................................... .... ...... ...... 9

What's New? ......... ........................................ ..... 11 Installing SEDCAD 4 ........................................ 13

Lost Hardware Locks .............................................................. 13 !nstallation Troubleshooting ... ......................................... ....... 13 UninstaIling SEDCAD 4 ...... ............................ ...................... 14 Software Copying .................. ................................................. 14

How to Contact Us ............................................ 15 SEDCAD Update Version Support Policy .................... ... ..... .. : 16 Year 2000 (Y2K) Compliance Statement .................... ............ 16

How to Use Help ......... ............................. ... ...... 17 Peogram Navigation .................................. .. .... ..... ........ ........ ... 17 Table Navigation ......... ... ........................................................ 17

Getting Started ................... ............................... 19 File Menu ............... ..... ..... ...................................................... 19 Preferences .. .... ................. ............. ........... .... ... ........................ 20 Main Screen .. ......... ...... ............................. ....... .......... .... ..... ... 20

General Tab ...... ..... .......................... ........................... .. .. 20 Designer box ........ ............................. .. ............... .... .. 20 Peoject Title box ..... ........................... .. ............. .... .... 20 Cornmeors box ...................................................... 0 • • 20 Last Modified box ...... ... ....... ...... ........... .... .. ............ . 21

Design Tab ............. ....................................................... . 21 Resulrs Tab ........... ......... ...................... ... . , ...................... 21

Storm Information ........................ ..................... 23 Sroem Information .... .... .......................................... ..... .. .... .... 23 Storm Type ..... .............................. ..... .... .. ......... ..... ................. 23

NRCS Disrcibution Determination .. ......... .... ................. 23 49 pt or 241 pt NRCS Distribution - A Comparison ...... 24

Historical Perspective ............ ..... ..... .. ................. ... ... . 24 Peak Flow Considerations .................. ....................... 24 Implications of Distribution Selection ...................... 24 Effect of Distribution on Size of Control Strucrurc:s .. 25

Culven Design Assessment ............ ................... . 25 What does it all mean? ...................................... 26

Channel Design Assessmenr .............. .... ..... .. .... ........ 27 Pond Design Analysis ..... ............... ............ ............ ... 27

User-defined Rainfall Distribution ........... .... ................... 28 Input Storm Even!. ...... .... ............. ... ................. ........... ... 28

4 Design Storm ............................................... .. ......... ....... .. ...... 29 Rainfall Deprh ... ..................................................................... 29 Graph Storm .... .... ..... .............. .. ... ............. ... ... ... ....... ............. 30 R Srorm ...... ............ ...................... ............. ......... ....... ...... ....... 31

Sedimentology ................................................... 33 Particle Size Distribucion ... ...... .... ...................................... ... 0 •• 33

Input Oprions ................ ...................... .......................... 33 Creare New burten ................................................... 33 Open Existing burron ............................................... 33 Add % Finer burton .......... ...... .................... ............. 33 Chango % Finer Name burton ......... ........................ 33 Graph burron ................. ............... .. ........ ... .... .......... 34

Partide Size Grid ............................................................ 34 Specific Graviry ........................................................ 34 Submerged Bulk Specific Graviry ............. ................. 34 Cornmenrs ........ ......... ........ ........ ...... ............ .... .. .. .... 35

Partiele Size Disrriburion Laboratory Analysis ........ .. ....... 35 ....,1 Partide Size Classificarion ..................... .... .............................. 36 Toral Sedimenr and Serrleable Solids ..................... .................. 36

Networking ........................................................ 39 Srrucrure Nerworking ............................................. ................ 39 Suuaure Linkage ..................................................... .............. 39 Srrucrure Numbering Example .................. ............................. 40

Inpur of Srrucrure Nerwork .............. .............................. 41 ....,1

Subwatershed Information .............. ........ .... ....... 43 Suhwarershed Hydrology Inpur Informarion ........................... 43

Subwarershed Area ......................................................... 43 Time of Concentrarian ........... ...... ............ ................. .. ... 43 Muskingum Routing ............ ............... .... ................. .... .. 44

Rouring Calculator ........ ... ............... ..... ............. ...... :45 Curve Number ............................................................... 45

Hydrologic Soil Group ........ ...... .. ............................. 46 Unir Hydrograph Response Shape ....... ........................... 47

TR-55 Emulator .......................... ............................ 47 Hydrograph and/or Sedimenrgraph Graph Burton .......... ....... .48

Hydrograph ..... .. ......... .................................................... 48 Sedimenrgraph ............................................................... 48

Subwarershed Sedimentology Input Informarion .................... 48 ....,1

Erodibiliry (K) factor ...................................................... 49 Texrural Triangle ........................... .. .. ....................... 49 Wischmcicr Nomograph .......................................... 50

LS Factor ........................................................................ 50 L Facror .................................................................... 50

-'

5 Representative Slope Length - L ..... .. ................ 50 L for a Concave Slope ........................ ............... 51 L foe Transirions to Concentrated Flow ............. 52 L forTypical Slope Lengths ............................... 52 L Factor Accuracy and Sensitivity ...................... 52

S Factor .................................................................... 52 Representative Slope - S .................................... 53

C Factor ......................................................................... 53 C Factor tables in SEDCAD 4 .................................. 53 Canopy Elfects ......................................................... 53 Surface Cover Elfects ................................................ 53 Soil Surface Roughness ............................................. 54

P Factor .......... .... ........ ............ ........................................ 54

Structure Design ................................................ 55 Structure Types .............. ....................... ................................. . 55

PONO DESIGN .................... ... .... .. .... .. ............................ 57 Elevation - Area ...................................................................... 57

Stage Increment .............................................................. 58 Pond Spillways ........................................................................ 58

Pond Spillways, Orop Inlet ............................................. 59 Pond Spillway, Straight Pipe ........................................... 59 Pond Spillway, Perforated Riser ....................................... 60 Pond Spillway, Weirs ...................................................... 60

Broad-crested Weir .......... ... .. .................................... 60 Sharp-crested Weir .............................. ..................... 61 Sidc-contracting Weir ....... ..... ................................... 61 V-notch Weir ............................................................ 61

Pond Spillway, Siphons ................................................... 61 Fixed Siphons .......................... ..... .............. .............. 61 Floating Siphon ........... ............... ................. ............. 62

Pond Spillways, Emergency Spillway .............................. 62 Estimating Inirial Pond Spillway Elevations

and the Top ofOam ............................................. 62 Estimating rhe erest Length of an

Emergency Spillway ............................................. 63 Bottom Width and Sideslope Sizing

for Emergency Spillways ....................................... 63 Pond Spillways, User-defined ............................ .............. 63

Pond Sedimentology ............................................................... 64 Sediment Storage .......... .................................................. 64

Do Nat Reset Zero Stage .......................................... 64 R Annual Method .................................................... 64 Disturbed Acres Method ......................................... 65 Contributing Acres Methad ...................................... 65

6 Inflow Sediment Tons Mernod ... ... ... ........................ 65 User-dcfined Sedimenr Storage .. ........ ........... .... ........ 65

Dead Space .... ....... ......... ... ....... ........ ......... .... .. .... .. .... ...... 65

PON O D ESIGN EXAMPLE .. .. .. ... .......... . . . . . . ... .. . ... . .. . . . ....... .. 66 Problem Statemenr .................. .. .............. .. .... ... .... ...... .. ...... .... 66

Storm Input ........ ..... ..... .. ... ........ .......... .. .......... .............. 66 Partide Size Distribuuon ......... .... ...... ........... .................. 66 Networking .. .............. ........ ............................................ 67 Subwatershed Information .... ...... ... ..... ....... .... ........... ...... 67

Subwatershed Hydrology Inpu" ... .............. .............. 67 Subwatershed Sedimentology Inpu" ........................ 70 Graphs ... ........ ......... .... .............. ....... ................. ....... 7 1 Structure #1 SWS Report ......................................... 71

Pond Inpu!5: Hydrology .. ... .. ... ..... ......................... .... ..... 72 Elevation-Area ........... ..... .............. ..... ............. ...... .... 72 Elevation-Diseharge .... ... .. ........ .... ... .. .................. ... .. 72

Pond ¡npu,,: Sedimentology ..... ... .... ................ ............... 73 Results and Discussion ............... ..... ........... .. ...... .. .. ..... ... 73

Conrrasring Permanent Pool and Passive Dewatering ... ... ........ 74 Additional A1ternative Design ..... ........ ..... ........ .............. . 75

SILT FENCE DESIGN .. .. ................ .... . . .......... . . . . . ......... ..... 76 Silt Fenee Design Example ............... ............ .. ... .. ........ ............ 76

Storm Input ..................... ...... ... .... ... .. .... ........................ 77 Parricle Size Distribution ............. ...... ........... ..... ...... .. ..... 77 Networking ................... ..... .. ... ..... ... ....... ........ ...... ... ....... 77 Subwatershed Informauon .............. .. .............. ............... . 77

Subwatershed Hydrology and Sedimentology Inpu" 78 Graphs .. ..... ................................ ..... ................. .... .... 80

Silt Fence Design Paramerers ............ .......... ... .. .......... .......... ... 80 Silt Fence Flow Rate .. ................. .. ..... ........... .................. 80 Silt Fence Width Along rhe Contour ..... ........... .. ... ......... 80 Silt Fenee Heighr ................ .............. .. .......... ....... ........... 81 Silt Fence Upgradienr Land Slope ........ ......... ........... ....... 81 Silt Fence Tie-back Distante ..... ..................... ............. .... 81 Silt Fence Addirional Weirs ........ ... ... ... .... .. ....... ... .... .. .. .... 81 Silr Fence Design Resul" .. ............. ...... ......... ............. .. ... 82 Silt Fence Design wirh Dedicared Sedimenr Srorage ........ 83

GRASS FILTER D ESIGN .. ......... . ..... ........... . . ... ..... ....... .. . . ... 84 Grass Filrer D esign Example .. .. .... .... .. .... ..... ................. .. .. ....... 84

Networking .. .. ... .. .......... .............................. ..... ......... .... . 84 Grass Filter Design ¡nputs ........ .. ......... ................... ....... . 85

Grass Filree Roughness Coefficien.r ........................... 85 Grass Hydraulie Spacing .. ......................................... 86 Grass Stiffness Factor .... ....... .... .. ....... ... ............... ...... 86

7 Grass Height ....... ............. .................................. ...... 86 Grass Filter Infiltratian Rate ..................................... 86 Grass Filter Dimensions .................................... ....... 86

Grass Filter Design Results ............................................. 87 Grass Filter Reports .................................................. 88

Structure Summary: ..... ...... . .............. ................ 88 Silt Fence Reports: ............. ............................... 88 Grass Filter Reports: ...................................... .... 89

CHECK DAM DESIGN . ..... .... .. ......... . . . . . .. .....•...........••...... 90 Check Dam Design Example ................ ... ............................... 90

Storm Input ............................ ............................... .... .... 90 Partic1e Size Distribution ............. ................................... 91 N etworking .................................................................... 91 Subwatershed Information ............ ................................. 91

Subwatershed Hydrology and Sedimelltology Inputs 92 Check Dam Design Inputs ............................................. 93 Porous Rock Check Dam Design Results ........................ 93

CHANNEL DESIGN .. ............. . .. . ...................................... 94 ,- Channel Shape ...................................... ................................. 94

Freeboard ........................ ........... .......................................... .. 94 - NONERODlBLE CHANNEL DESIGN ..... . .... . ... . . . .................. 95 Nonerodible Channel Example ........... ............................... ..... 95

ERODlBl.E CHANNEL DESIGN ......... . ..... . . . ....... . ...... ..... ..... 96

- Erodible Channel Example ........................................ ............. 96

VEGETATED CHANNEL DESIGN . .......... .............. . ....... . .... . 98 Rerardance Class .......................... ... ....................................... . 98 Vegerated Channel Stability Analysis ............................ .......... 99 Vegetated Channel Capacity Analysis ...................................... 99 Vegetated Channel Example ........................................... ........ 99

ROCK RIPRAP CHANNEL DESIGN ......... . ................. ...... . . 101 Simons/OSM Method ................................ .......................... 101

Ripr.p Channel Example - Simons/OSM .......... ..... ...... 102 PADER Method ................................................................... 102

Riprap Channel Example - PADER .............................. 103

CULVERT DESIGN ............... . ......................... . ... . . . ........ . 104 Culvert/Str.ight Pipe Flow Regimes ............. ...... ... .......... ...... 104 Culvert Design Example ............................ ............ ............... 105

Culvert Design .......................................................... .. . 105

PLUNGE POOL DESIGN .... .. ..... . ... .......... ... .......... .. ......... 108 PI unge Pool Design Example ................................................ 108

Reports ...... ...... ...... .. ........ .. ..... ... ........... .. ......... 111 Report Vie\ver ............. ............ _ .. .............. ...... ..... ................ 112

8

Troubleshooting ................................ .... ... ........ 115 Installation Questions .. ... ...................... ........... .. .. ................. 115 Prinüng Questions ................... ... .. .. ...................................... 116

Appendix - Maps ......... ....................... ...... ..... 117 I SOERODENT (R ANNUAL) MAr OF EASTERN U.S ........... 117 IsoERoDENT (R ANNUAL) MAr OF WESTERN U.S ......... 118 IsoERoDENT (R ANNUAL) MAp OF CAIlFORNIA ............. 119 ISOERODENT (R ANNUAL) MAr OF OREGON AND

WASHINGTON .................................. .. ................... . .. 120

References ......................... ...... .............. ........... 121

--

--

9

Acknowledgements We continually Icarn from oue lisees. Through OUT rechnica1 support program cf one-on-one consultation and shon courses, you provide liS with yOlle

requirements nceded ca salve more diverse and complex problems. SEDeAD version 4 for Windows 95 and NT (SEDCAD 4) was designed to meet your needs of increased productivity and ease Df use. Allhough ir is perhaps unusual to acknowledge sofrware lisers , ir is each of you who has taken me time to caH US, who shared ideas oc real-world problems. who needed more capabilidesi ir

is you rhar ereared rhe form of version 4. We appreeiare and thank you for yOlle advice and extensive feedback.

Government agencies mar design and review stormwater, eros ion and sediment

control programs have beeo essential to providing insights te regulatory needs. The Omee of Surfaee Mining (OSM) Western, Mid-eonrinenral and Eastern Coordination Centecs have becn acrive parricipants in rhe design and review of program capabilities. They have been especially instrumental in providing guidance in the format of output options thar facilitare a thorough and rapid review of permits. The Technical Information Processing System (TIPS) of m e Offiee of Surfaee Mining has beeo espeeially helpful in providing us wim rhe opportunity to tesr Beta vc:rsions of SEDeAD 4 through in-house short courses. OSM provides SEDCAD to me 24 states wirh primacy under rhe Surfaee Mining Control and Reclamatioo Aet of 1977 (SMCRA) for use in permir review and in the design of Abandoned Mine Lands (AML) reclama­tion projecrs and remediarion plans for bond forfeitUJ;e sires. OSM uses SEDCAD ro review permit applieations from indust~y. OSM also urilizes SEDCAD in prepara tia n of Cumulative Hydrologie Impaet Assessmenrs (CHIA's) ro determine me eumulative hydrologie effeers of multiple mining operarions on adjacent lands and warersheds during and a&er mining.

Consultants, indusrry and government agencies are using SEDCAD to design and evaluate stormwarer, erosion and scdiment control sysrems for highways, utiliries, residentiaI and commercial developmenrs. wasre disposal facilities, silviculture operarions and in rhe dcvelopment of environmental impacr assessments as mandated by the National Environmenral Policy Aer (NEPA) . Feedback from rhis wide diversity of users and applicarions has enabled us tú

furrner our development of SEDeAD 4 ro cncompass cross-fertilization of

ideas generared by our users.

Dr. Bruce Wilson has provided us wirh rhe framework equarions and numer­ous algorirnms thar he developed while ar rhe Universiry of Kenrucky. We are

always grareful ro Bruee for his insighrs inro sediment control proeesses and

especially his pioneering research in predicring [he performance of sedimenr basins.

Dr. Benjamin C. Dysart JII continues to be Richard's mentor. Ben's insighes on how ro view aspccrs of rhe world, ehereby creating rhe opportuniry for

10 constructive change, are again gratefulIy acknowledged. Through Richard,

Ben's counscl and influence continues ro expand and has posirively touched rhe lives ofPam, Derrnís, and many ofRichard's current and former srudents.

Qur spouses, Beth and Chuck, and oue children Stephen, Brian, and Lauren,

conrinually pur our lives in perspective. SEDeAD 4 js only one of our drearos .

-

-

11

WHAT'S N EW?

Welcome to SEDCAD 4 for Windows!

Whatwe did ...

• Prograrnmed foc speed utilizing a 32-bit processor

• Re-derived equauons and wrote new algorirnms

• Stripped all code to basic equations

• Created the foundarían foc rapid future developments

Results ...

Windows 95 and NT program

• PulIy implements Windows 95 and NT using standards of graphical user interface (GUI) design

• Use ofWindows printer drivers provides sophisticated report and extensive graphing capabilities

Networlcing is virtually unlimitedand unrestricted

• "Junction and branch" nomenclature is no longer used

• Structures can be placed at any location and in any sequence

• Large mines, subdivisions and landfilIs can be modeled in a single dynamic mn

Dynamic design mode implemented • The calculations are always running in background fiode

• Once subwatershed parameters are entered, the peak flow, peak sediment concentration, hydrograph and sedimentgraph are irnmediately available ro design the structure

Addidelete/change Structures and Subwatersheds with a click

• Structures can be inserted anywhere

• The impact of alternative structures can be readily evaluated

Rapid Full Sereen Editing

• Simply point-and-click to move ro the desired input screen

Silt Fence designs

• Determine the ,ediment trap efliciency and effiuent concentration

NRCS (SCS) TR-55 emulator

• Emulate the TR-55 unir hydrograph and obrain a peak flow which closely matches TR-55

12 Graphical viewing and outputs

• Zoom in capabilicy on all graphics

• Print graphics using Windows printer drivers

• Save graphic file (.bmp, .eps, .wmf)

... And much more!

• Extensive Help rabies, figures and guidance

• New 'e hcrocs' and mining spoi! erodibility 'K hctors'

• Curve Num~r tables available with a click

• Semicircular ~nd circular nonerodible channcls

• Save and fecall erodiblc parride size distributions

• Save and recalI utilines

• SEDeAD 4 Repon Viewer

All of this and the (opcional) SEDeAD-AutoeAD interface!

We hope you enjoy lhe program!

--

13

INSTALLING SEDeAD 4

To install SEDCAD 4 for Windows, use lhe SETUP.EXE program on lhe CD or disk #l.

• Plug lhe hardware lock inlO lhe parallel port on your computer. A printer may lhen be plugged inlO me lock. Be sure no' 'o plug me lock into a serial port! The end wilh ,he prongs on ,he lock (male) will go lO

thc computer.

• Start Windows 95 oc NT. As a precauaon. shut clown anyapplications rhar may be currently running.

• losen rhe CD into rhe drive on your system. • If you have Aurorun enabled on youe system, che setup routine should

automatically srart afier a few moments. If ir does nor, select "Run" from lhe "Slart" menu. Entet "D:\SETUP" in ,he dialog box (teplace D: wi,h yoUt CD-ROM drive) and click OK.

Follow rhe instructions 00 rhe screen ro verify where ro install rhe programo You will need lO restart your computer afrer loading SEDCAD 4.

The first ,ime you run SED CAD 4, ,he program will ask you for your setial number. This is located on the sticker on rhe CD sleeve. Once this number is enrered, ir should Dor be needed again unless you install the software Doto

anorher machine. Be sure ro keep rhe CD. serial number, and hardware lock(s) in a safe place!

Lost Hardware Locks Lost hardware lock(s) are replaced a' ,he additional copy ptice, applicable at rhe time of arder. Ir is therefore very important that you keep track of the hardware locks issued with your purchase.

Installation Troubleshooting If, after you install the program, the computer does not recognize the hardware lock, it is usually a network drive that has conflicted with the installation. To remedy, do me foIlowing:

• Remove the local machine from the network by logging off (this is ,emporaryJ).

• Select "Run" from ,he "S'art" burton. Type into lhe dialog box: C:\SEDCAD4IHWKEY\SETUP IQ4 and click OK.

14 • This should being up che Senrinel Deivee Serup Progeam window. Pull

clown [he FuncrÍons menu, dick on "Insral! Sentinel Driver".

• The program will derecr what operating system yOil are running. Ir wíU ask foe the appropeiate path. The path will be either: C:\SEDCAD4\HWKEY\WIN_95 (Windows 95) Oe C:\SEDCAD4\HWKEY\Wm_NT\l386 (Windows NT) (assuming C: is che hard deive lerrer, aod SEDCAD4 is che subdireetory oame)

• Cliek 00 OK ro load the driver. You should get a message iodicaciog the driver was installed and thar yOil should restart yOU! system.

Uninstalling SEDCAD 4 To uoiostall SEDCAD 4 for Wiodows, use the Add/Remove ieoo 00 the Control Panel. From (he Seart ButtDO on the Desktop, go ro Setúngs>Control Panel. Double-cliek 00 d,e Add/Remove Programs icono Cliek 00 SEDCAD 4 [rom [he lower list, then press Remove.

All SEDCAD 4 progeams aod registry serriogs will be removed. Geoerated files aod folders (e.g. *.se4 aod *.srp) are not removed.

If, duriog the Uninstall, you eeeeive che message that a particular file (usually a * .dll) is llor used by omer programs and should you remove, yOil may answer safely "No to All", ro keep che file io the System folder. This does oot affeet youe machine at aH. If yOil choose ro rernove [he file, yOU! machine will probably funcrion fine, bue [hefe is a chance char if sorne orher program char is nor registered in [he Windows registry uses [he file, [har program would become unusable and would need [O be installed again.

Software Copying Unauchorized eopying of software is iIlegal.

No marter how easy it is to .copy a file from a diskette OI CD-ROM to yOlle PC, no manee how infrequendy you plan ro use the software, no mattee if you promise to buy ir afteI yOll try ir out, no mattee how good yOllr imentions -

unauthorized copying of software is íllegal.

Who is Responsible?

If you make an unauchoeized (illegal) copy of a software applieatioo, you are considered personally eesponsible for any damages. This peesonalliability could eosr you $25,000 or moee foe eaeh iilegal eopy you make aod for e.eh time you use the copy_

. --

-

15

How IO CONIACI Us We strive to develop a continuing relationship between our clients and our­selves. Your input and advice is very important to uso Many of OUt enhance­ments directly address youe needs foc more capabilities, ease of use, and further ineceases in productivity.

SEDCAD is one of the very few software packages where you actua!ly talk ro the developers when you cal! for assistance. Since 1987, we have been for­tunare to help thousands of callers with a wide variety of applications. We believe that we also can help you with ene-on-ane consultation.

Tú mast efficiendy use your time we recornmend thar you use chis guide in contacting che program developers.

• Website: www.mysedcad.com Start hefe foc most of yoU! needs. The sire has information, download­able updates and arder forms, FAQ's and contact information .

• Pam Schwab, Civil Software Design P.O. Box 706, Ames, IA 50010 Phone and FAX: (515) 292-4115

email: pschwab@mysedcad.com • Ordering SEDCAD 4 for Windows • Pelee Informatian • Accounts/Billing • Promotiona! Literature • Windows questions • Suspect Erroes • Hardware questions

• Rlchard Warner Biosystems and Agricultural Engineering, Universiry of Kentucky 128 Agricultura! Engineering Building Lexingron, KY 40546-0276 Phone: (859) 257-3000 ext. 217 (oflice) FAX: (859) 257-5671 email: rwarner@mysedcad.com and/or rwarner@bae.uky.edu

• Overview of SEDeAD 4 capabilities • Orre-on-ane consultation • Description Df methodologies • New application requirements • Reference materials

• Short Course Scheduling • Eroded particle size analyses and questions

16

• Dennis MarshaU 2725 Nonh Anthony Fort Wayne. IN 46805 Phone: (219) 373-1945 email: marshald@ipfW.cdu

• SEDCAD4 - AutoCAD Interface Questions • AutoCAD File Transfers

SEDCAD Update Version Support Policy In excess of95% of our users upgrade within 6 monms of me release date of a ncw version. Upgrades significantly ¡nerease case of use. add subsrantial ¡neceases in capabilities, and vastly ¡nereases productivity. AH users are encouraged ro rake advantage of these features.

To bcucr serve Que clienrs Que policy is [Q supporr me newes[ release. SEDCAD version 3 suppon (primarily free disk swaps and/or reset codes) will be discontinued 6 months afrer the release ofSEDCAD 4 for Windows 95 and NT.

Year 2000 (Y2K) Compliance Statement SEDCAD 4 for Windows is compliant with the year 2000. It has been

tested under Windows 95 & Windows NT 4.0 with a system date greater than 12/31/1999. No pan of this product uses the hardware or system date for any purpose, other than for display or informational purposes. Where a date is displayed, it is displayed with the full century (i.e. 01/0112000).

-

-

--

17

How TO USE HELP

Extensive Help rabIes, figures. and guidance have beeo entcred ioto SEDeAD 4. There are several ways to view topies of interest:

• Click che Contents tah to browse by category

• Click rhe Index tah ro see a list of index enteies: either type rhe word

you're looking foc oc scrotl through the lis!

• Click me Find [ah ro search foc words oc phrases [har may be contained

in a Help topic

Program Navigation To move from box to box in chis program, you use standard Windows naviga­cion rechniques. Generally, the TAB key will move ro [he next field, oc you may always left-click on the desired field with che mouse.

Table Navigation The following shortcut keys work when navigating rabIes (e.g. Partide Size, Stage-Arca-Capacity, etc.):

To move ro:

... next column

.. .las! column

... rhe previous colurno

... the first colurnn on current row

... the next row 00 current colurno

... the tast row aod tast colurno

... (he curreot colurnn in previous row

... (he first colurnn io the first row

Press:

TAB, or RlGHT ARROW END SHIFT + TAB, or LEFT ARROW HOME DOWNARROW CTRL+END UPARROW CTRL+HOME

18 --'

-'

-'

-'

--'

-'

-'

-'

--'

.....1

-'

~

-~

---....1

..-

~

-'

--'

.....1

--'

-'

-'

-'

-'

--'

-' ~

-"

.....1

~

'-'

'-'

19

GETTING STARTED

When you sran SEDCAD 4, me Maio Screen wiU be (he ¡nitial startup screen. Ir contains all dIe menus and cornmands nceded [O ruo a programo

The first time you ruo (he program, it is a good idea to go to [he FilelPreferences menu. and enter (he default informatioo foc design storms and direcrory locaricos. The defauJts may be overridden in the program, as weII.

Te evaluare a design storm and structure ncrwork, everything necessary foe resul" will he entered from tbe Design Tah. Storm information, eroded

partide siZe distributioos, structure networking, and watershed and strucrure design parameters will aH he accessed from tbe D esign Tah.

File Menu New Project

Open Project ... Save

Save As ...

ReportView

Preferences

receor files

Exit

Clear aH work in progress. No filename is specified. Retrieve fIle from disk

Save current informatioo ro rhe file currently specmed. If no file is specified, this acts the same as Save ru. Save file ro disk under a new filen ame.

Print a saved report using the SEDeAD Report Viewer program

View and change program preferences

List of [he 4 mos[ recently accessed files

Close and exit program

20

Preferences Ger ro [he preference screen by pressing FilejPreferences. The screen allow5 default values ro be specified.

• Defaulr storm type, distribu­tion, and associated rainfalI depchs

• Default file locations

• Change Designer lisr • Defaule measurement sysrem

• Defaulr company information for display on caver page

Main Screen This screen is yOlle majn poinr of navigarion through rhe programo There are a series of pull-down menus at me rop. and also (he main index rabs.

General Tab This (ab holds general adminisrrative information .

Designer box • type in yOlle name, oc

------------------------p",,.,> ~ ..

~c-= ; "'" '··_·r--, ..!: ¡ ,-~ ,

'-~..!rí1- ) _. ,

-. ...-... =.~~ ---..J

~!~:'l'_ ' __ , __ "!-":-. '

• click on che drop-down button and pick ic from che Jisr

Once you have encered your name, ir will auromaricalJy be added ro che drop­down Iisr for all future runs,

Project Title box Anything emered hece will appear as che citle on che caver page of che reporto

Comments box DecaiJed comments may be made here, These will also appear on che cover page of che report,

---

Informational yellow background boxes - boxes with a yellow back­ground are not editable or changeable. They contain information that has either been calculated or determined from somewhere else.

21

For example. che file Dame is shown when [he current run infarmarion has beeo saved to a file. The file Dame can be entered anytime during (he entry of input data. To save to a file, c1ick 00 (he FilelSave As menu located at (he upper left of che screen.

You may also open an existing file by clicking FilelOpen or one of the filenames from [he recen t files lise.

The ftlename will chen appear in che box.

Last Modified box This box shows lhe dale and lime thal the file was lasl modified.

Design Tab The Design Tab is where you launch mast of youe design screens. There are three (3) main areas:

• Stoem Informarion

• Sedimentology

• Structure Networking and Design

Results Tab

The Results Tab is where you will formar and view youe reports.

22

-

-

23

STORM INFORMATION

Storm Information This is where you en ter rhe design storm for rhe runo If you have specified values in the preferences screen, youe derault values will automatically be entered.

Storm Type Click on me drop down bunon ro obtain a listing of available rypes of rainfal! distributions. Thc geographic bounds ror rhe Natural Resources Conservarían Service (NRCS), (formerly Soil Conservation Service, SCS) are shown:

The NRCS Srorm Type Distriburions are considered very conservative - ¡.c. the peak flow predicnons based on these Type Distribunons will be higher man almost any actual measured storm.

Two other options are available - User-defined distribution and rainfall evento

NRCS Distribution Determination A very simplified description of the memodology 10 determine NRCS distribu­rioos follows:

Assume rbar the incremental rainfall values are known for 10 years of storms throughout the applicable regioo Df a Type Distribution. Fer example, foc rhe Type II distribunon data would be available from par" or a11 of 40-plus states.

The enrire record is scanned to determine rhe highest 3-minutc rainfall intensiry. Similarly ,he highest 5, 10, 15, 30 minute values are determined for the entire geographical area. Also. the highest 1, 2, 3 ... hour rainfall intensi~ ties are Usted. These obscrved highest intensities are rhen placed in a rainfall

24 distrihution by putting me most incense value at a given temporallocation of che design storm, then proceeding to place che next highest ooto the right, aod theo 00 the left, chen 00 (he righr, ctc. irm¡ililiHII!

Uo 2 , I • \O .2 " •• :11 2l' :o 1 I

-.... 1 i ,

49 pt or 241 pt NRCS Distribution - A Comparison

Historical Perspective Mast regulations specify a design srocm. such as a 10 year-24 hour storm. These regulations do not specify the required desigo distribution. SEDCAD 4 enables the usee ro specify various NRCS Type distributions oc enter a user~ defioed distributioo based 00 analysis of rainfall data for a geographical region. Additiooally, SED CAD 4 provides [Wo options for fitting a NRCS distribu­[ion, namely 49 poine and 241 paim disuibutions. The 49 point distribution is traditionally used io textbooks and is used in SEDCAD versioo 3.1. The SCS used the 49 point method io the 1975 versioo ofTR-55, aod appeared 10

change to the 241 point distributioo with the 1986 TR-55 versioo. lo 1986, NRCS distciburions appear co have beeo curve-firred ro provide data at 0.1 hOllr increments, whereas, che 49 poine distrihution uses 0.5 houe incremenrs. Both the 49 point and the 241 point disrributioos contain idenncal data poinrs at 0.5 hour incremems. The only difference between rhese twa disrribuoons is mar for rhe 49 p.aim distriburion. a linear interpolation between 0.5 hour values was applied and for the 241 poim distribution curve fitting was used.

Peak Flow Considerations The rype af distrihurion selected and rhe choice of number of points used in fitting a disrriburion affects rhe peak flow. Using rhe 241 point distriburion will result in a higher peak flow than usiog the 49 point distributioo. Other factors that affect peak flow are curve number. time of concentrarion and the shape of the dimensiooless unit hydrograph. SEDCAD 4 provides fout dimensionless unir hydrograph shapes ro enable rhe user to moce c10sely account foc the hydrologic response of a subwatershed. Obviously. when dilfcrcnt parametcrs are sclected and dilfcrcm distributions or fit of di5tribu~ rions are chosen and diEFerent peak flows resulto rhe usee must decide which parameters oc distribution selections are most appropriate for a given applica p

tion.

Implications of Distribution Selection Ar firsr a user may assumc rhar the 0.1 hour rime increment more c10sely captures the rainfall intensiry and is rherefore more accurate. Oc it.could be assumed that whatever distribucion, oc pacameters, creacing rhe highest peak

25 flow is mast conservative and rherefore will provide [he highest leve! of protection. The usee is cautioned ro al50 consider me made! being used, rhe design storm frequency. gcomorphology of natural streams and the liability foc downstream fIooding when selecring a disrribution oc distribution fit.

Natural srreams Oow a~ bankfull at a recurrence of berween 1.5 and 2 ycars (Rosgen, 1996). Any storm with a reeurrenee interval gre.ter than 1.5 to 2 years will tempor.rily inundare the floodplain. A 10 ye.r-24 hour design storm will flow ¡mo the floodplain. be temporarily sroced, and then flow back ro me stream. The temporary storage significantly attenuates [he peak flow. With models sueh as HEC-2 or WSPRO, which require extensive surveyed input data of the longitudinal profile of che stream and Dumemus cross­sections of che stream and adjacent floodplain, ir would be appropriate ro use the 241 poinc distribution fir. The higher prediered peak flow of rhe 241 poinc fit. which occurs for approximately 6 minutes, is accounted for in [hese models through modeling rhe floodplain and baekwarer effeces.

Models sueh as SEDCAD 4, TR-55 and HEC-I use simplified rouring tcchniques mar do nor require such an exrensive srrcam inpur dacabase as rhe HEC-2 programo These simplified stteam routing reehniques are eomplercly juscified for mese cypes of modds. Since these models do noc account for floodplain srorage, use of me 24 1 point distribucion will resulr in an overdesigll of natural channels for storms with recurren ce intervals greater than 1.5 ro 2 years. This overdesign is based on a 6 minute interval when the highest peak flow occurs.

Effect of Distribution on Size of Control Structures

Culvert Design Assessment The design of eulvem has traditionally been aecomplished by passing rhe peak flow without completing a backw3ter anaIysis, which would require surveying che up-gradient ponded area of the culvert. The headwater-discharge relation­ship is esrablished for • specified eulvert invert, rype, lengrh, slope, and taiIwater condirion. From rhese input data. a culvert pipe is sized. Tradirional culvert design disregards the up-geadient stage-storage relationship. Again. if a comprehensive backwater analysis is ro be complered. and the usee is taking credit for me attenuation of peak Oow using the suge-srorage relationship of rhe ponded up-gradient storage area then the 241 paint distribution is appropriate. If rhe standard culvert procedures are employed rhe 49 paint procedure is recommended.

Example: A eomparison of rhe 49 point and me 241 poinr NRCS Type II distriburions for a 10 acre disturbed watershed is discussed herein. Precipitation values are for Chicagd, IL. The 10 year-24 hourType II disttibution is used wirh a rainfall deprh of 4.0 inches. The curve number is 86, che time of concentra­rion is 0.13 hrs, and rhe dimensionless unir hydrograph shape is Fast.

26 Culvert Assessment The peak dischacge foc the 49 point and 241 point distributions is 22.88 cfs and 32.09 cfs, rcspectively. The associated culverts are 24 and 30 ¡nehes, rcspcctive1y. Culvert design was analyzed without backwatcr srorage consider­atians, which is (he standard practice foc mos[ applicarions. The 241 point distcibution genecated a peak flow about 9 cfs highec than the 49 point distribution. Viewing the hydrograph for the 241 poioe distribution ir can be seco rhar discharge excceds 22.88 cfs foc 22 minutes.

Now ler us consider accounting for [he srage-storage effecr up-gradienr of a 24 inch culvert foc me 241 point distcibution. This will contrase the 49 point standard culvcrt design with the 241 point backwater culverr designo The ponded acea is assumed to inccease from 40 by 40 fe at elevation 650 fe ro 80 by 80 fe at 655 fe elevation. The pond structuce was used foc this analysis. Results show tha[ me Peak In was 32.09 cfs, and the Peak Out was 23.26 cfs. This is very similar to [he standard culvert anaIysis used in che 49 pojDt distribution resultiog in 22.88 cfs being discharged rhrough a 24 inch culvert. Thus rhe results are equivalent.

Conrrasring further, ler us consider whether the 30 inch culvert would be selecred anyway based on the 241 point disrriburion. Again backwarer is accounted for using rhe pond rourine. The results show a Peak In of32.09 cfs and Peak Out of 27.07 cfs. Thus, rhe difference in selecring a 30 inch versus a 24 inch culvert is an inccease in discharge of3.81 cfs (16 %). The backwatec associated with [he 24 inch aud 30 inch culverts is 3.76 fe and 3.07 ft, respectivdy. The rradeoffs become apparenr. The 241 poinr disrribution results in a 30 inch culvert, based on standard culvert design memodology. If this is selected in contrasr ro a 24 inch culvert, the headwarer is reduced by 0.69 ft and the discharge is increased by 16 percent. Also, culvert cost is a consideracion.

Another point ro be consideced is that a 24 inch and 30 inch culvert can discharge 26.90 cfs and 40.05 cfs a[ 4.5 fe headwatec, cespectively. The dewatecing time foc the entice flow ro pass through me 24 in eh and 30 inch culvert is 19 and 14.5 minutes, respectively. The length oftime mat the culvert is dischacging aboye 23 cfs is 3.5 and 10 minutes foc the 24 inch and 30 inch pipe, cespcctive\y.

What does it all mean? The tradeoffs between a 24 inch and a 30 inch culvert for {he peak discharge of32.09 cfs resulring from the 241 poinr distriburion being selected and

backwatec being analyzed ace:

1. The 30 inch culvert costs more 2. Dischacge is highec by 16% foc the 30 inch pipe 3. Discharge aboye 23 cfs will exir {he 30 inch culvert for 3 times longer

than for (he 24 inch culvert

27 AH of [hese ¡tems are considered ro be negatives in thar cosr is higher and downstream flooding is poremially increased and sustained foc a looger period oftime.

Advantages of the larger culvert are:

1. The f10w eapacity at 4.5 ft headwater is greater by 13 cE; than for the 24 ineh pipe

2. Headwater is less by 0.7 ft 3. The entire storm is diseharged abollt 5 minutes faster for the 30 ineh

culvert

The conclusion, foc (his situadon, is thar (he choice of rhe 49 point oc the 241 paint distribution is essentially inconsequenrial, unless COS! oc parcodal downstream flooding is a major concern.

Channel Design Assessment For the same 10 ac disturbed w3tcrshed, a channel anaIysis was completcd. Again. the peak f10w for the 49 point and the 241 point distributions is 22.88 and 32.09 efs. respective/y. Channe/s analyzed are

l . a 2 ft wide. 2: 1 sideslope concrete ehanne/ on a 2% slope 2. an 8 & wide, 3: 1 sideslope eanhen channel transporting sedimenr

laden water on a 1 % slope 3. a grass w:ltcrway. 8 ft wide, 3: 1 sideslopes and a 2% channel d ope

The resulr is that all ehanne/s are stable as design for both peak flows and the only ehange is an inereased ehanne! depth of abollt 0.1 to 0.1 5 ft for the 49 point versus the 241 point distribution.

Again the conclusion is [har 00 coosequeorial chaoge io chanoel design occurred duc te the choice of distribution, and that a 1.2 to 1.8 ¡nch difFerence io channel depth is withio construction specifications for channels.

Pond Design Analysis A similar analysis was conducted foc a pond receiving runoff from a 50 ac watershed. The differcnce in embankment height foc me [W O diffecenr distriburions is Iess rhan 0.2 ft.

28

User-defined Rainfall Distribution This selection is locared undee rhe Seoem Type aptioo.

For a given geographical regian, sorne SEDeAD usees have developed storm

---¡¡¡;¡;; type distributions based on actual rainfall data for me region. Usually about 30 years of incremental rainfaU data

~ .... ~ . ~ is needed ro condller 5uch an anaJysis. The henefir of .,..= I ~ I~ conducting mis type of analysis is mar me storm rype ! .... ::¡ _ :=;.~ distribution is specific to (har regian. From very limired

~ .~:~~~m~~_-_·~.;t5 observations by the SEDeAD authors, the resulting - JI" a<eoo distribution is Iess intense [han the NRSC Type distribution

I :: -~:-::.:.:i~~-.-.:!il thar was formulated foc a much larger geographic area. The

~ _. _ m· :::'< resule is a lower predicted peak flow value foc a given design --"~ ~~~n:":"'r stoem frequency and durarian than predicrcd using che ·..1Lf :; -/ NRCS distribution .

.

To enter a user-defined distriburion, enter

• [he distribution name

• the accumulated dimensionless depths foc each one half-haur time

incremento The final emry corresponding ro [he 24 hOllr mark should be 1.00.

The user-defined disrcibution will now appear as a selecrion when me Stoem Type drop-down button is c1icked for fu,"re runs.

Input Storm Event This selection is located ondee [he Srorm Type oprion.

To eorer a srofm evenr, entee [he

• accumulated rime (real time, in hOlles)

• accumulated rainfaU depth (real deprh, in inches)

for me storm being modeled.

The Rainfall Eveor apdon is very useful foc research rhar is being conducted [O assess rhe predicrive capabili­

ties ofSEDCAD. The predicred vs. observed

hydrographs can be evaluated. A single parameter sensiriviry analysis can be conducred ro determine (he best fir of observed values vs. runoff volume, predicted peak flow, or a com­

plete hydrograph.

AddirionaUy, the NRCS (SCS) Curve Number (CN) can be determined for the accua! storm event based on measured runaff volume. With enough srorms from a warershed with a constan[ land use, rhe SEDCAD user can ascertain an average eN for rhar land use. For example. rhe CN associated wirh a graded

29 spoil can be determined foc a series of storms and a representative eN can be selecred foc future designs. Similarly, this same type of analysis can be conducted foc a 3% vegetated crown of a landfill, a desert pavement in semi­arid areas, oc agricultura! pasrure lands.

The RainfaJl Event aprian is very useful 'w avoid oc conducr lidgation in caurt proceedings. Assume mar [he incremental rainfall was recorded foc an actual storm (on-sire oc at a nearby aieporr) and a mining company, cornmercial development. landftll, etc. is involved in licigation because of downstream flooding. The SEDeAD user can show the pre-development peak flow and compare mar value with me during construction peak flow, with controls such as sediment hasins in place. and show thar flooding would have been warse during pre-development conditions. Líkewise, a downstrcam entiry couId prove mat an ineffective stormwater control plan was the cause of flooding and sue for damages.

Design Storm The design srorm is descrihed hy frequency (recurrence interval) (years) and stoem duratíon (houes). Yon can choose from a líst of aften used dcsign storms hy clicking on the drop-down hunon and then choosing the desired design storm. You may also designate a different sterm frequency and durarion by choosing "Orher" sroero selecciono You will have the opportuniry to specifjr rhe frequency and duration, and ir will auromarically he added to rhe list of dcsign srorms foe furure design options.

Nore thar you can designare the Design storrn as a default oprion using prefeeences.

Rainfall Depth Infoemation on srorm depths associated with a specified frequency and duration may be found in several references:

• Eastern U .S. - Hershfield, D. M. 1961. Rainfall frequency atlas of the

United States foe durations from 30 minutes to 24 hours and retuen periods from 1 te 100 years. U.S. Department of Commerce, Weamer Bureau Tcchnica! Paper No. 40. Washingron, D.e. (out of print). These maps are located in the Appendix .

• Western U.S. - Miller, ).E, R. H. Fredcrick, and R.). Tracey. 1973.

Precipitation-frequency atlas of the Western United 5tates. U.5. Deparrmenr of Commerce, Nationa! Weather Service, NOAA Atlas 2, Silver Springs, MD.

Volumc 1 Volume II Volumc III

Montana Wyoming Colorado

30 Volume IV New Merico VolumeV Idaho VolumeVI Utah Volume VII Nevada Volume VIII Arizona Volume IX Washington Volume X Oregon VolumeXI California

• A1aska - U.S. Department ofCommerce. 1963. Probable Maximum Precipitation and Rainfall-Frequency Data for A1aska. U.S. Deparnnent ofCornmerce. Nacional Oceanic and Atmospheric Admistration Technical Paper No. 40, Washingron, D.C.

• Eastern and Central U.S. - Frederick, R. H ., V. A. Myers and E. P. Auciello. 1977. Five ro 60 minute precipitarían Frequency for me Eastern and Central Unired States. U.S. Departmenr of Commerce, National Oceanic and Atmospheric Admistration Technical Memoran­dum NWS HYDRO-35, Washington, D.C.

• Probable Maximum Precipitation (PMP) arnounts have been published

in the U.S. Narional Wearher Service Hydromereorological Reports (1943-1984) .

Graph Storm This visual display wiU show rhe intensiry of various Type Distributions. The steepest segment of me accumulated curve creates [he peak flow. Ir is reCOffi­

mended thar rhe user view alternative Type curves ro see [he diEferences among each distribution.

Comparison belween Type 11 and Type 111 Distributions

.. .. ..

The Incremental Rainfall option provides a display in 0.05 hour increments. From this display rhe construcrion of a storm distribution can be readily seen. Again it is recornmended that you contrast various Type Disrributions using rhe incremental mode selection and pay particular anenrion ro rhe difrerent rainfall intensiries associared wirh each distribution. The duration of various design storms can also be observed.

-

-

31 '~~~~----~~~----------.

~s~_~._~o~-.~_IIt~~l l ",,--c--,--,--c- 1

i:: ¡¡ , ! J ", :...;..,.¡",¡._ ......... .w...J !

00;-""; , elDl11(I&ItI:m~1>I 1 ____ .. ___________ T-~~~ _________ J

Comparison between Type If and Type 111 Distributions

R Storm The R-storm value is used in [he pond sediment stoeage R-annual calcularion method. In chis method, [he required sediment storage is determined as a function of me R-storm, average anoual R, and number of years of sediment storage desired. See R-annuaJ method foc a more detailed explanaríon of (his procedure.

R-storm is based on che rainfaJl quantiry and stoem distrihution speci fied in me Srorm Type, Design Stotm and Rainfall Depm input values, and is calculated using the updated equarion by Brown and Fostet (1987) which ¡neludes more data foc ¡es developmenr ::l nd h;¡ s ;¡ hetter functionaJ form at low intensities (Renard, K. G., er. al, 1997).

32

-

33

SEDIMENTOLOGY

The sedimentology oprioD burton is functional when ir is checked. Otherwise only hydtologic cakulations will be preformed. To eorer partic1e size distribuüons [he sedimen­tology buttoo must be rurned on.

Particle Size Distribution Eroded partide size distributions (EPSDs) should be entered whenever significant changes in soil (oc spoil) texture are faund. For example, the A­horizon and B oc e-harilOn soil textures may be quite different since the lower horizon soils may have significantly higher day contents. Similarly, ffeshly placed spoi! and weathered spoi! in the Appalachian coa! mining areas may have significantly different EPSDs. Another EPSD might be entered for a soi! used foc reclamarían thar is essentially a composite of diffeceor soil horizons oc differenr soil textures.

Input Options

Create New button This is used to ¡npU[ a new eroded particle size disrciburion foc a particular project oc IDearían. You will be prompted foc:

• a filename and locadon ro save the EPSD

• a Dame foc che first percent finer disrcibution

The file will be saved with a ".pfn" exrension.

Open Existing button This will open a dialog box allowing the specification of any previously-saved partide size distribution file. When the file is chosen, the data will be ftlled in the parricle size grid.

Add % Finer button This allows the addition of a EPSD, corresponding ro the current particle sizes. Note that all particle size distributions in any one file must have me same mm sizes, while the percent finer values differentiates bet:\veen the distributions.

34 Change % Finer Name button Since [he % Finer Name is used in the cest of the program as list-box choices and rcpons, ir is important mar each distribution be clearly labcled. If you need ro change [he label fOI a disrribution, you click chis burton.

Graph button This will show a graph Df all particle size distributions entered in the current file.

P~S!zé:~)' Xfiner

Particle Size Grid ~

Enter me eroded particle sizes, in mm, and me corresponding percent finer distribution. The mm sizes will normally correspond to standard sieve sizes. For [he finer sediment size fraction. mm sizes usually correspond ro [he standard procedures associated wich pipette oc hydrometer procedures.

Standard rabie navigation applies ro this grid. Ofeen, ir is easier ro enter all mm sizes by using [he clown arrow, then moving ro [he next colurnn. To enrer rhe percent finer disrribution, use the clown arrow.

Specific Gravity The specific gravity of sands. silrs and clays normally ranges from 2.61 ro 2.67. In rhe case of eroded soils, aggregares commonly occur and are very stable umil dispersed. Soil aggregates consist of day and silr size partieles chemically and/ or physically bonded rogerher. As such. air is entrained between rhe bonded particles. Depending on rhe size of the aggregate, the specific gravity ranges from approximarely 1.6 ro 1.8 gm/cc. A representative specific gravity for a soil mar has individual sand, silr and day size particles, and soil aggregares is abour 2.5. This is rhe defaulr value used in SEDCAD.

Submerged Bulk Specific Gravity This parameter is used in rnodeling particle settling in the Irnhoff cone. As a sercling soil particle approaches the bottom of an Irnhoff cone, the water contained between previously deposited partieles musr be displaced. The submerged bulk specific gravity is a function of me deposited sediment size distribution. It is assumed thar rhe majority of sand sizes have been deposired

within up gradienr sedimenr controIs. It is further assumed rhar a significant portion of day parrides will llot settle within rhe one hour time-frame of me Irnhoff cone test. Therefore me bulk submerged specific graviry is based on a mixture of particles rhar contain a small fraction of sand, a relatively small fracrion of day and a significant percentage of silt. Based on these assump­rions, rhe [ange of bulk submerged specific graviry is froro approximately 1.05 ro 1.35 gmlcc. A defaulr value of 1.25 is used in SEDCAD.

35 Comments The EPSD will ofren contain sand, silt and clay-size particles. With respect to

the performance of sediment control structures 5uch as filter fabric feoces, sedimenr traps, sediment basins, etc., me mest important range of sediment sizes is from medium silr (0.031-0.016 mm) ro very fine silr (0.008-0.004 mm). The sand and coarse silt size fractions will ofren be substantially deposited within a sediment control structure. The dar fracrien will substan­tiaUy pass through sediment control structures, unless natural oc artificial floccularion occurs. With this in mind, ir should be realized that rhe etoded percent finer values of (he sand and day fraedon are flor as critical as thar cf (he silt fracrion.

The exception ro [his is if a small sediment trap receives a high inflow gener­ated from a large storm. In (his case, a fracrien of [he coarse silt and very fine sand may pass through me sediment control.

SEDCAD is a rather unique model in that it tracks the change in partide size distribution as sediment-Iaden flow proceeds from the slope where it originates ro the subwatershed outlet, routed ro a structure, passes through a sediment control structure, and finally down-gradient. Changes io PSDs will occur mrough deposition while being comed, as a fuoction of the performance of sediment controls, and as different PSDs are combined from various subwatersheds.

The change in PSD (and therefore the performance of sediment controls) can be readily seeo through two sediment basios operating in series. The up­gradient basin may have a sediment trap efficiency of 85%, whereas the second basio trap efficiency may be reduced ro 30% sioce the more readily deposited sediment partides have previously beeo removed by the fics! basio.

Be cautioned that simplified methods, such as tables and charts or simple programs (which only predict the independent performance of individual sediment contcols) wiII yield erroneous results when applied ro sediment controls in series.

Partiele Size Distribution Laboratory Analysis The EPSD is normally determined from a laborarory experiment using a rainfall simularor. Thece is not an ASTM oc ASAE standard. A representative composite soil (oc spoil) is placed in an expanded metal pan. The soil should be air-dried but nor ground and no dispersing agent should be used. The pan

is placed on abour a 9% slope. A rainf.Ul simularor is used ro produce the requiced rainfall intensity and dcop size distribution mimicking the highest 1-hour rainfal1 intensity of the specified Type storm distciburion foc me specified design srorm. The sediment-Iaden runoffis comed ro a series of standard sieves. Water passing the lowest sieve (u5uallya 200-mesh sieve) is retained in

36 a bucker foc further processing. Afree rainfall is completed, me sediment

remaining in rhe sieves is lighrly washed from sieve ro sieve, paying particular attenrion ro rhe sediment remaining on the 200-mesh sjeve. A representarive sample is collected from me bucket containing (he fine ffaenan sedimenr (passing the 200-mesh sieve), and is furrher processed by using a piperre, hydromerer oc partide size anaIyzer ro find me percent finer cf various silt and day 5ize parricles. No dispersing agent should be used on me sample, to maintain and mimic conditions cf eroded soils.

To determine rhe required l-hour storm intensity foc a 10 year-24 houe, 4.2-ioch, Type II distribution, eoree me values ioto rhe Storm Informarion secrion of SEDCAD. Click on Graph Storm burton. Move approximare!y !á-hollr to each side of rhe inflection point cf me storm (occuring near 12-hours for a Type 11). Ar 12.5 hallrs the accumula,ed rainfull is abou, 3.1 inches and for 11.5 hOllrs the accumulated rainfall is about 1.2 inches. Therefare ,he highest 1-hollr intensity is abour 1.9 inches per hour. This value should be used ro perform the rainfall simulator experimento The run time should be between 12 [O 1 hOllr.

Particle Size Classification Size. in mm Class Description 16.00 - 8.00 Medium grave! 8.00 - 4.00 Fine grave! 4.00 - 2.00 Very fine grave! 2.00 - 1.00 Very coarse sand 1. 00 - 0.5 O Coarse sand 0.50 - 0.25 Medium sand 0.25 - 0.125 Fine sand 0.125 - 0.062 Very find sand 0.062 - 0.031 Coarse silt 0.031 - 0.016 Medium silt 0.016 - 0.008 Fine sil, 0.008 - 0.004 Very fine silt 0.004 - 0.002 Coarse clay 0.002 - 0.001 Medillm clay 0.001 - 0.0005 Fine clay 0.0005 - 0.00024 Very fine clay

Total Sediment and Settleable Solids Several different sediment values are outpur ro meet various user needs. Tans of sediment in and out of the basin are provided ro determine the overall pond efficiency and [O understand [he toral sediment loading of the down-gradient

waterbody. Sediment concentrations are provided as both peak and volume

weighted.

~

~

-'

37 Sedimenr concentrations are given fae total sediment and settleahle solids. Toral sedimenr is determined by evaporating water from (he sample and weighing (he remaining sedimenL SettleabIe solids are determincd in (he laboratory using an Irnhoff cone. Thc ane litee sample is allowed ro setde foc one hour and (he quantity of settleable solids is rcad from the scale 00 the Imhoff cone. In SEDeAD 4, settleable solids are determined from a math­emarical representarion' of [he Imhoff cone and Stoke's law.

Potenrial fluvial impacr can he determined from [hese various parameters. For example, a large portion of total sediment load oould potentially be deposited in a large down-gradient reservoir and partially reduce its efficiency foe recreational, water suppIy, oc vacious mulriple uses. Setdeahle solids are important foc determining me potencial impacr of deposition on spawning areas which can also degrade potemial foad sources. The totaJ sediment load (which should primarily consist of fines, silts and days) directlyaffects the turhidity, light penetration, and [he ahílity of a stream to perform its various functions. Sediment concentrauon and durarion are mosr imporrant in assessing me impacr on fish and aquatic ¡nvertebrares.

38

--

39

NETWORKING

There are no restrictions in nerworking structures with regard ro number of structures or spatial placement.

1)

Structure Networking Informacioo to be enrered is [he

• structurc cype

• structure Iinkage

• Muskingum routing parameters (ro nexc structure)

• structure description. useful in ourput claricy

Structures can be entered by c1icking che Add 5tructure buttoo, oc optionally may be imponed from ,he SED-ACAD interface.

The necworking of structures begins wich numbering each structure. The numbering of stcuctures is a usee preference and can be done any way char che usee is mase cornfortable with. We recornmend numbering from che upmost gradient structure clown to the confluence of two streams and then continuing [he numbering sequence at che up-gradienr section of the adjacent stream. Stcucrures can be added or deleted. Structures can be readily changed, e.g. from an erodible channel to a grass-warerway. Only one srructUre can be routed ro rhe toral watershed outlet, rhe outler being designared as O (zero), The only requiremenrs are rhar the mosr down-gradient strucrure musr be roured ro rhe O outler, and rhere can be only one O outler.

We recommend thar rhe user fiests sketch the loearion of structures and label them by structure number and type.

Structure Linkage Linkage among structures is accomplished by designaring rhar water flows from structure number X ro structure number Y. Y is rhe target structure. The flow from one oc more srructures mar discharge ro a single down-gradient structure.

40 Example 1 Sr[ucrure 1 flows ro structure 4, scructure 2 flows ro 4, and structure 4 flows to ,he ouder (O) is -a vaJid networking

C·

Slrá.:;tUle'Twe HuD Nu' N~I

TilÍ$ Struclute

~

4

(lIowslnío! S\JUCÍtlIe # . ,~, 4 ~, 4

"" o

option. In chis case, structure 3 was once in the networking and since beeo de1eted. Srrucrure numbers are automatically assigned sequentially as struc­

tutes are added, and deleted from [he list if me structure is deleted.

Hint: whenever possible, try to simply ehange a strueture type (by pulling down the list 011 the right hand edge and ehoosing the new type) imtcad of deleting it pennanently. Deletíng structures reduces the total nttmber ofstructures availab/e to the run, new subwatershed information w¡li need to be added, and overal! networkillg may be compromised unless rechecked carefolly.

Every stcucture must have a designated down-gradienr rarget structure. The target structure is [he nexr srructure irnrnediately down-gradient of me previous srructure.

Example 2 fu anorher example of linking srructures, assume mar two channels convey runoff ro a common culvert which discharges to a down-gradient channe! rhar eonveys rhe diseharge ro a pondo We can designare eaeh of rhe ehannels as Strueture 1 and 2 (SI and S2), rhe eulverr as S3 rhe down-gradient ehannel and pond as S4 and 55, respeerively. To link, SI flows to 53; 52 flow to S3, S3 flows to S4 and S4 flows t~ S5 whieh flows to rhe ouder (O).

Structure Numbering Example This schematic shows one way to number the structures. The only requiremenr is mat the most down-gradient srructure be routed ro the O labeled srruerure. AlI srructures ro be designed musr be numbered.

As shown, rhe diseharge from

• Srrueture 1 (S 1 - erodible channe!) flows ro Structure 2 (52 - pond sediment rrap)

510 MJlL

• 5tructures 2 and 3 (52 - pond and 53 - erodible channe!) both f10w to

5tructure 4 (54 - culvert)

• 5tructure 4 (54 - culvert) f10ws to 5tructure 5 (S5 - riprap channe!)

• Structure 5 (S5 - riprap channel) f10ws to Structure 6 (S6 - pond

sediment basin)

• 5tructure 6 (56 - pond) f10ws to Structure 7 (S7 - pi unge pool)

• Structure 8 (S8 - grassed waterway channcl) f10ws to Structure 9 (59 -

culvert)

• Structure 7 (S7 - plunge pool) and Structure 9 (S9 - culvert) f10w to

Structure 10 (S 1 O - nul!)

41

• Structure 10 (510 - nul!) exits the watershed, designated with a O (zero)

Channel - efodib!e -----pOñd ------ ----~_._------,---

Cllanne!- erodible --'-~-----cUiveít -·-"----·

-- ------- -------

Networking Screen

Input of Structure Network The Networking Screen shows the entry of structore linkages. Ir is highly recornmended thar [he SEDCAD 4 user initially draw a schematic of [he problem and labe! all structures.

Hint: An easy method to input information quickly is first to add alJ structures (using the "Add Strueture" button far eaeh struetu,,), and "leet the strueture type far eaeh strueture. Next, cliek on the "fows into" strueture number area, jil! in the "jlows into" linkage nttmber, thm use Ihe Sli-~N~

down arrow to proceed to the next strucure. {f o!.s Then ji!! in the ''Deseription'' eolumn, # DA":., again using the down arrow key to navigate to the next lineo The last information to enter is any "Routing" to n ex! structure.

C!ick on the Routing edit button to en ter in thtse va/ues.

These linkages can also be viewed wirh the "Show Linkages" burron.

4' # II~

1I1O NtiI

" '""

42

43

SUBWATERSHED INFORMATION

AJI ¡nformario" foc watersheds and detailed structure paramerers are ¡oPO[ in me design secciono The desigo sequence, fOI each structure, is ro enter (he hydrograph and sedimentgraph inputs for all contributing subwatersheds, and theo emee (he detailed structure ¡"pues.

The screen auromarically defaults ro [he lowesr numbered structure (usually SI) and 10 hydrology inputs for a watershed. Click on Add SWS (Subwatershed) and the hydrology (and sedimentology) input records appear wi th SWS 1 en tered.

Subwatershed Hydrology Input Information

For each subwa[ershed, (SWS) data is needed for the:

• area

• time of concemration

• K and X roming to (he structure (oprional)

• NRCS (SCS) Curve Number (CN)

• selection of a dimensionless unir hydrograph shape

Subwatershed Area The area of (he sHbwarershed is simply enteced a&er being calculated by using a planimeter, from a surveying oc earchwork package. digitized using SEDCAD-AuIOCAD, or it may be automatically entered using the SEDCAD­AutoCAD input programo

Time of Concentration The time of concentracion is used to determine how long ir rakes runoff from the tntirr SWS to reach the outlet of the SWS. To determine this, the hydrau­lically longest flow path is needed. Normally [he time of concentrarion consisrs of an overland flow componenr and a channel flow component. Overland flow is calcula[ed by [he NRCS (SCS) upland curve method (NRCS, 1975). Channe! flow can be estimared using the equa[ions deve!oped for large gullies, diversions and low flowing srreams (category 8 in the Rouring Calcula­ror) or full bank flow in srreams (category 9), or using Manning's equation to determine a time.

44 Time of concentrauon affects peak flow and hydrograph shape. Ir does flor efrece runoff volume. A larger time of concentration results in a lower peak flow.

Time of concentration is Dor used ro determine time from me subwatershed outlet ro me structure, unless che suhwatershed outler is located at me suuc­ture. It is striccly determined within (he SWS boundary. To roure from me SWS ouclet ro [he down-gradient structure. use dte Muskingum Rouring paramerers.

Muskingum Routing Muskingum routing is used te route flow from an up-gradient to a down­gradient location. Ir is used foc:

• rouring hetween stfuctures

• routing from a subwatecshed oudet (Q irs structure, when me ourlet of a subwatershed is nO( located at me structure

Rouung is completed from [he outkt of che up-gradient structure ro me Otltltl

of me down-gradienc suuc[Ure. Musk..ingum couting is the vehicle used to

anenuare a hydrograph while ir is being spatiaUy transferred. The Muskingum paramerers are K and X. K accounts foc me time ir takes ro proceed from an up-graclient ro a down-gradienr location. Muskingum K roerefore equates ro rhe toral hydraulic routing time beLWcen structuces oc rhe time from me auder of a subwarershed ro a srcucrurc. Muskingum X is functionally relared tO me average srream reach velociry and accaunts for me a[[enuarion of me hydrograph sueh rhar X = (0.5 V)/(1.7 + V).

The hydrograph comed along a srream is attenuated due to the flow resistance along the stream bed and banks. Attenuation can be viewed as a spreading out of rhe hydrograph, rhereby lowering rhe peak flow. }" Muskingum K inereases and as Muskingum X approaches zero, hydrogcaph attenuation incceases rhereby furrher redueing rhe peak flow during rouring.

The Muskingum couting parametecs can be estimated using [wo derived equations in SEDCAD 4. The fir,r caregory (referred ro as 8 in rhe Routing Calcularor) is for large guJlies and smaJl meams. The veloeiry-slope relarion­ship is V = 3 x square root ofS(%). It is generally applicable ro steams flowing about 2/3 to 1 ft deep. Examples of ehannels where category 8 is applicable are:

• a parabolie guJly on a 1 % slope flowing about 1 ft deep and eonveying

10 cEs • a 7 fr wide trapezoidal ehannel' with a graveJly ro small eobble bed,

eonveying 15 cEs along a 1 % gradient at a flow deprh of 2/3 ft

• a 20 ft wide trapezoidal ehannel with 2: 1 side slopes, a 1 % bed slope and eonveying 40 efs at a flow depth of 2/3 ft

45

• a trapezoidal channd with 4: I side slopes conveying 80 cfs ar 2/3 fr deprh on a 3 ro 4% slope

The second category (designared 9 in the Rouring Calcularor), is for channds flowing generally 4 to 5 fr deep, i.e. near bank full. The velociry slope relationship is V = 9 x square roor ofS(%). Examples of rhe rype of mearn rhar would be modded by caregory 9 are:

• a trapezoidal channd wirh a bonom widrh of 25 fr and 3: 1 sideslopes that conveys 1800 cfs a10ng a 2% bed gradienr at a deprh of 4 fr

• a trapezoidal channel with a 4% bed slope and a bonom width of 10 fr and 3:1 sideslopes conveying 2500cfs ar 18.3 fps ar a depth of5 fr

These two categories are applicable [O a wide range of channel configurations. Generally caregory 8 should be used for meams flowing about a foot deep eonveying a discharge of lOro 100 cfs, whereas caregory 9 should be used for streams flowing at bank full conveying substantial discharge quantities.

If rhe SEDeAD 4 user would like ro determine an exact salution foc Muskingum roudng parameters, SECAD 4 channel utilities can be used ro determine rhe velociry. Wirh knowledge abour rhe srrearn length and velociry, rime is calculared which is equated ro Muskingum K, and Muskingum X =

(0.5 V)/(1.7 + V).

Routing Calculator Use of the calculator 1S straight forward. The calcularar 1S used foc both time of concentrarion determinarían, and foc Muskingum rauriog determinanoo.

For examplc, a5SUffiC thar a stream reach is 4000 fe long and rhe e1evation difference is 80 ft. Nso assume that the flow depth is expected ro be about 1 ft deep. Muskingum Rouring parameters are desired. Click on Add a Flow Path and sdecr category 8. Tab ro the Vertical column and enter 80. Tab again ro the Horizontal colurno aod enter 4000. Press the Tab or Enrer key, and me results ofK = 0.262 hours and X = 0.357 appear. Click on OK and rhese answers are entered into the spread sheet. Similarly, the Siope columo couid have been used instead ofVertical. The siope is often used when an actual channel design is being evaluared.

The routine checks for 2 of 3 categories (in the order of Slope, Vertical, and Horizontal), and calculates the remaining one.

Curve Number The NRCS (SCS) Curve Number (CN) is used 10 calculate runoff. CN is a function ofland use and hydrologic soil group. The tables

• Runoff Curve Numbers for Urban Areas

• Runoff Curve Numbers for Cultivated Agricultural Lands

46

• Runoff Curve Numbers foc Orher Agricultural Lands

• Runoff Curve Numbers foe Arid and Semiaeid Rangelands

provide Curve Numbee as a funcrion ofland use and Hydro!ogic Soil Group (HSG).

A highee CN will geneeale a highee eunoff vo!ume and a higher peak flow.

Hydrologic Soil Group Definicion of scs Hyruologic SoH Geoups:

A These soHs have a high infiltralion raleo Theyare chiefly deep, well­drained sands or gravels. (Low runoff pOlencial) . (> 0.30 in/he)

B These soi!s have a moderale infiltracion rale when lhoroughly wel. They are chiefly moderarely deep. well-drained soils of moderately fine te

moderarely coarse lexlure. (0.15 - 0.30 in/he)

e These soils have a slow infiltrarion cate when wet. They are chiear modeealely deep, well-drained soUs of modeealelr fine lO moderalely coarse rexruee. (0.05 - 0.15 in/hr)

D These soils have a very slow infilrrarion rateo They are chidly ciar soils wirh a high swelling pOlemial, soils wirh a permanently high waler rabIe, soiJs.with a dar pan ar Oc oeae me surface and shallow soiIs over nearly impervious marerials. (High runoff pOlencial). (O - 0.05 in/he)

The NRCS has classified more lhan 4,000 soi! seeies inlO foue HSG's according ro eheie minimum infilrcarion rate foc approximarely saturated bace soil condilions (NRCS, 1986).

The county soil survey willliS! soi! series foe all soils in lhe county. Hydrologic soils groups are givcn as a function of soil texture and corrcsponding infiltra­lion eale foe diS!uebed and uncompacled soi!s in Table ritled NRCS Hydro­logic Soil Groups. (NRCS, 1986; and Beakensiek, el. al.. 1977.).

In selecting an HSG, consideration should be given ro compacrion by heavy equipmenr. Depending on rhe soil moisrure eomem, eanh-moving equipmenr may eompaet a soillayer resulting in redueed infiltration. Where eompaetion is evidenr, an ¡nerease in rhe HSG from, e.g. B to e, may be appropriare.

Unit Hydrograph Response Shape The unit hydrograph merhodology is used in SEDCAD. A double triangle dimensionless unit hydrograph shape (DUHS) is used. The usee has a choice among lheee DUHS, and a TR55 Emulaloe. Having lhree DUHS provides the model user wirh rhe opponunity to obtain a refined" prediction of the S!oem hydrograph. The faS! DUHS should be used foe ueban aeeas and a¡-eas where a rapid hydrologic response is amicipared such as dismrbed soils rhar

-

r­r-

r­r­r-

47 have beco subjected te cempacaoo by heavy equipmenr and foc desert paverncnt. The medium UHS is appropriate foc pastuce land, land in row erops, small grajn and legumes. pasrures with less man 50% ground cover and semi-arid mountain brush mixture and sagebrush with a grass understory and 30% or less ground cover. The slow DUHS was developed foc heavi ly foresled areas with thick ground residue covering greatee than 75% of (he surface. It is also applicable lo areas mal have a high infillralion rale and a delayed hydro­logic response such as meadow land that is marntained in continuous grass and mowed for hay and pasrure land wich grealer lhan 75% ground cover.

The difference in peak flow berween me fasl and medium DUH is relalively small whereas lhe difference in peak flow berween che medium and slow DUH is much greater. A slow DUH shape will substantially decrease the peak flow to reflect che delayed runoff response of heavily forestcd areas with a thick layer of detritus.

TR-55 Emulator To provide the user wich che capability of approximaling lhe NRCS TR-55 (1986) hydrograph peaks and runoff volumes, che TR-55 emulator was developed. The TR-55 emulator uses a single triangle dimensionless unil hydrograph shape, whereas me NRCSTR-55 program uses a single gamma fuocaoo type curve. Use oE me single triangle in SEDCAD 4 creares a higher peak flow of about 2 to 8 pereent above lhat of the NRCS TR-55 programo

For example, consider a 10 yr-24 hr NRCS Type II storm of 4.2 inches. a curve number of 86, rhe following comparison is made:

10 Acres, Tc=0.35 hrs 100 Acres, T c=O.5 hes

NRCS TR-55 TR-55 emulator (1986) Program

134 cfs 226 cfs

241 pt resolution 144 cfs 239 c&

Using

Of course the runoff volume is identical between rhe two methods, since only ~ the curve number influences the runoff volume.

~

r­r-

ü ~

Hydrograph and/or Sedimentgraph Graph -' Button ~

Hydrograph This bunDn will display the hydrograph(s) for set of subwatershed(s) corre­sponding ro che current structure. A combined total hydrograph is also shown, however, chis combined hydrograph is only foc the current contributing subwatersheds irnmediately down-gradient of the previous structurc. It does llor indude any flow from the previous structure. Far the combined hydrograph reaching a stcucrure, click me hydrograph buceon on me structure design screen.

Sedimentgraph

This button will display tbe sedimentgraphs(s) for the current subwatersheds. A combined rotal is llor shown as a view oprian, since sedimentgraphs are llor additive che way hydrographs arc. After a sedimenrgraph is created ar a subwatershed, ir is men [ouced and added to rhe combined upstream sedimentgraph. Each subwatershed sedimentgraph is combined with me rotal, as flow continues downstream. To view a combined total sedimentgraph, click the sedimentgraph burton on the structure design screen.

Subwatershed Sedimentology Input Information

Sedimentology data is only entered if me Sedimentology opdon on the Maio Design Tab has been turned on. The quantity of sediment eroded and rransported to rhe ouder of a subwatershed is derermined by tbe peak f1ow, tulloff volume, soil erodibility, representative slope lengtb and gradient, rhe rype of soil cover, and control practices such as terraces, eOntour furrows, aod strips of vegerarion. The peak f10w and tunoff volume are calculared in the hydrology routine. For each subwatershed, data is entered for me:

• soi! erodibility - K factor

• representative slope length - L

• representative slope - S

• type of soi! cover - e factor

• control praetices - P factor

• Qne of the input eroded parricle size distributions

49 Erodibility (K) factor

A soil's sllsceptibility to eros ion ís derermined by irs resistan ce to detachment by rainfall and flowing water.

The factors thar efrece a soil 's resistance to erosion are me size of [he soil parricle, aggregation, oc bonding, of soil particles by organic material. fercaus. aluminum oc silica oxides and infiltradon capacity. Cearse to medium sands have a high infiltrarion rate, low runoff potencial and are easily detached but relatively large. The K for eoarse textured soils ranges from 0.05 to 0.2. Clays have a low infiltration rate, high runoff potential and are diffieult ro detaeh due ro being aggregated. The K for fine-textured soils ranges from 0.05 ro 0.15. Medium-textured soils, such as a silt loam, have moderare infiltraríon cates, moderare runoff potential and are moderately susceptible to particle detaehment. K-values range from 0.25 ro 0.45. Soils with a high pereentage of silt size particles are especially susceptible ro erosiono K values for high silr eontent soils range from 0.45 to as mueh as 0.65 (Weesies, 1998).

The rexrural rriangle can be used ro classify soils in me United States Depart· rnent of Agricultural (USDA) system. The percent sand, silr and clay are for the parent soil.

Soil K-faerors can ofren be found in NRCS soil surveys published for eaeh county. Sorne publications have K-faetors as a function of soil horizon, Le .. various depths.

Textural Triangle Two texrural triangles are shown here. The first shows the textural triangle used to classify soils in the United States Department of Agrieultural (USDA) sysrern. The percent sand, silr and clay are for rhe parent soil.

The seeond shows the Unified Soil Classifieation System (USCS) superim­posed onto the USDA textural triangle.

, ... ... a ......... ¡

50 Wischmeier Nomograph The nomograph can be used ro determine approximare K-values foc subsoil and spoíl. The input> are: pereenr silr and very fine sand (0.05 ro 0.10 mm). percenr sand minus very fine sand (0.10 ro 2.0 mm), perceor organic material, soil structure, and permeability. Informarion on soil structure can be readily obtained from a soil scientist. Permeability ranges from very slow ro rapid.

(Wischmeier. W.H .• eL al .• 1978)

LS Factor The effeer of ropography on erosion is derermined mrough me LS-fueror. The LS-factor is calculated from [he represenr3tive length, L, and (he representa­rive slope. S. SEDeAD 4 uses rhe Modified Universal Soil Loss Equarion (MUSLE) wim the addition of the new S-fuctor developed for the Revised USLE. MUSLE enables the user to calculare the soi/loss from a subwatershed based on USLE parameters. volume of runoff and peak f1ow.

L Factor L factor equals l fot the standatd plot length of72 .6 fr. Lis grearer for longer 510pc lengths and less than one foc shorcer lengrhs.

Representative Slope Length - L Definition: The represenrarive 510pe lengrh is [he distance from me origin cf overland flow to a location a10ng the slope where either the gradient decre.ses to the extent

that transpon capacity ís reduced enabling deposition or where overland Ilow becomes concenrcated in a defined channel.

r

Typieal slope lengths (Dissmeyer and Foster, 1980).

• Slope A - If undisrurbed forest soi! above does not yield surfaee runoff. the tap cf 510pe starts with edge cf undisrurbed focest soil and extends downslope to windrow jf runoff is concemrated by windrow.

51

• 510pe B - PoiO[ cf erigin cf runoff lO windrow ir runoff is concentrated bywindrow.

• 510pe e -From windrow to flow concentration poinr. • 510pe D - Point Df erigin cf runoff ro road [har concentrares runoff • 510pe E - Prom road ro flood plaio where deposition would occur. • Slope F - On nose of hill, from point to origin of runoff ro flood plain

where deposirion would occur. • Slope G - Point of origin of runoff to slight depression where runoff

would concentrare.

(Renard, K.G., er. al., 1997)

L for a Concave Slope A rule-of-thumb foc derermining che length, L. on a concave 510pe is char ir can be assumed [har depasieion begins where (he gradient is one-half cf che average gradient foc che concave slope. For example. assume a concave slope decreases &om 18 ro 2 percem. The average gradient is 10 percem and one­half of this is 5 peceent. The representative slope lengrb is from the origin of overland flow ro where me slopc: gradient is 5 percent. For flatter concave

. slopes, thece may be no deposition and the representative slope length will be

the entire length of the slope. For example, a eoncave slope decreases from 6 to 2 peceent. The avecage gradient is 4 peceent and one-half of tbis is 2 perccnt. Since me end of the slope is 2 percent. no significant deposition is expeeted (Sehroeder, 1998).

52

L for Transitions to Concentrated Flow The rransirion from overland flow ro concenrrated flow in a defined channel is anothee determination of 510pe length. For a head-of-hollow filI constructed on a 2:1 (H:V) slope with benches loeated every 25 ft vertieally the representa­tive slope lcngth is 50 ft. Simílady for a landfill with benehes loeated every 25 ft vertieally on a 4: 1 slope the representative slope length is 100 ft. For disturbed area that dfaios ¡nto a perimeter oc eDad diteh the representative slope length is from the origin of ovedand flow to the diteh.

L for Typical Slope Lengths For undisturbed watershed conditions overland flow usually concentrares imo ehanneJs in less than 400 ft although sorne slope lengrhs can reaeh 1000 ft. Under earth disturban ce activiries and during redamation ir is pDssible ro ereate long slope lengths. SEDeAD 4 limits the user to 1000 ft for a represen­rarive 510pe length. The usee is cautioned mar 510pe length is ofren overesti­mated using USGS ropographic maps since ir is difficult ro ascertain the location depositional oc concentrated areas from a 20-fr cootour map (Schroeder, 1998). Examples of reptesentative lengths are íllustrated.

L Factor Accuracy and Sensitivity L factor accuracy The best estimates of soilloss are for slope lengths tanging ftom 50 to 300 ft which is the range for experimental data. Aeeuracy is somewhat reduce for slope lengths ranging from 20 to 50 ft and ftom 300 to 600 ft. Aeeuracy for slope lengths grearer than 600 ft is mose likely lower sinee relationships for these lengths are extrapolated beyond the data base (Sehroeder, 1998).

L-factor sensitivity Differenees in slope lengrh estimares of 10 pereent are quite acceptable since chis is nor a very sensirive paramerer, especially for flaner slopes, eompared ro the representative slope gradicnt, S-factor (Sehroeder, 1998).

S Factor The S factor is usually easier to ascertain than rhe L factor. A representarive slope gradient, S, should be selected based on the topography of the subwarershed. Under dynamicalIy changing earrh discurbance condirions an average condicion should be estimated. Accuracy is best foc slopes between 3 and 20 perccnt, which is the predominant data base. Accucacy dcercases for gradients between 1 and 3 percent and from 20 to 35 percent. For slope gradients gcearer than 35 percent very litde data exises and equations have been extrapolated.

-

-

53 Representative Slope • S The representative 510pe is che typical oc representative gradient assocÍated with [he representative L foe overland flow foc each subwatershed.

C Factor The e factor represents the ¡nfluence cf cover material on or jusr beneath (he surfaee of the soil. A C-faetor of 1 ,epresents the base line eondition of a plot

maintained in a clean-tilled, continuous fallow sta te. The e-factor accounts foc canopy. surface cover (such as residue, grasses. weeds, mulches) , ::md surbce roughness.

C Factor tables in SEDCAD 4: • Typical C Factors Reponed in the Literatu,e

• C Factors fo, Meehanically P,epared Woodland Si,es

• e Factors foc Permanent Pasture. Rangeland, Idle Land, and Grazed

Woodland

• C Factors for Undisturbed Woodland

• e Factors foc Rack Covers

• e Facrocs foc Mulch Undee Constructíon Conditions

• e Factors foc Bare Soils Undee Construcrion Conditions

Canopy Effects Canopy represenrs planrs mar in~ercept raindrops. reducing fall velocicy and hence erosion, but these plams do not significandy effect surface runof[ The effect of canopy can readily be seen in the C Factors for Permanem Pasture, Raogeland, Idle Land and Grazed Woodland table. Considering only !he eanopy cover as a funetion of fall height, for a given pereent canopy, e.g. 75 % and foc zeco percent ground cover, as the faH heighr increases from 0.5 to 4 m rhe C-factor ¡ncreases trom 0.17 to 0.36. The shorter canopy vegetarion is abour twice as effective as the taller trees in reducing erosiono This reflects that the raindrop faH velocity is faster from being shed froro me tree canopy than ir is from !he mueh shorter heigh, of the tal1 weeds or short brush.

Suñace Cover Effects Surface cover is material attached ro rhe soil thar intercepts raindrops and delays runoff. It ineludes all types of marerials such as grasses, srraw mulch,

and cornrnercial products.

The key elemenr is thar surface materials muse be somehow held in place by roors, cornmercial tacifiers, netting, erc. such rhar marerials are nor removed by runoff or wind. The exteDr of contact berween the surface material and me soíl is a critical elemento If a straw mulch oc exceJsior mat is placed on a soil

54 surface rhar is rough and has small rilIs, ir will be less effecrive chan when placed on a smoother soil surface because runoff will flow between che soil and the mulch.

The C Factors for Permanent Pasture, Rangeland, ¡die Land, and Grazed Woodland rabIe ¡Ilustrares che effecr of surface cover. Far che no canopy condition che effectiveness cf grass as an erosion control material can be viewed. The e facror changes from 0.20 foc 20% ground cover ro 0.003 at 95-100% ground cover.

The rabIe of e Values foc Mulch Under Construction Conditions illustrares che effectiveness of straw mulch and me combinarian of straw mulch with rack

fragmenrs on che surface as a function of slope gradient and fill oc stripped copsoil and subsoils. As che quantity of straw mulch ineceases, che e value dcereases. For example e values foc a 6% slope eonsisting of a fill slope oc

placed topsoil decrease ttom .29 to .18 to .07 for \>2, 1 and 2 tons straw mulch, ccspeetively. This rabIe also shows rhar rhe effecriveness of straw mulch is slightly reduced as the slope gradient inereases. Also ilIusrrated is thar stcaw placed on a cut slope (srripped copsoil) is more effecrive rhan on a fill slope (placed topsoi1). This is because the cut slope is assumed to eontain the roor srructure of rhe removed vegetation within rhe soil matrix rhereby resisring erosion o

Soil Surface Roughness As given in rhe C Values for Bare Soils at Consrrucrion Sires rabIe ir can be seen thar a fiH slope is more prone ro erosion than a cur slope. The fill slope consisrs of relatively loose soils that have not had an opporruniry [Q consolidare or aggeegare. A cm slope is viewed as a more compacted soil and is more resistanr ro erosiono This is especially true for a cut slope where only the surface vegetation has been removed leaving the root srcucture of the grasses which hold the soil in pace and resist erosion (Kuenstlee, 1998).

P Factor The P factor aeeounts foe specific supporr pracriees such as conroucing. terracing. and deposition at the base segmenr of a eoncave slope. Ir also accounts foc sedimenr control barriers such as grass buffer srrips. straw bales, grave! or filter barriers, and stiff-grass hedges (Wende, 1998). A P value of 1.0 is rhe default value when no control practices are utilized.

For SEDCAD 4, the mode! user is encoueaged to explore RUSLE version 1.06,

which is due to be eeleased in f.1I1998 by me Office ofSurface Mining,

Wesrern Regional Coordinaring Centec, Office ofTechnology Transfer. Denver, CO. This RUSLE program was specifically deve!oped foe mining and con­struction. The publication will be enritled "Guidelines foc che Use of che

Rcvised Universal Soil Loss Equation (RUS LE) on Mined Lands, Construction Sires, and Reclaimed Lands".

-

-

r r

55

STRUCTURE DESIGN

Structure design is done dynamically, ¡.c., once rhe contributing watershed

data is entered, SEDCAD runs in a background mode and automatically calculares and routes hydrographs aild sedimentgraphs ro rhe structure. For channels and culverts. the peak flow is automatically cntcfcd as a structure design input. Alternative structure design scenarios are rhen invesrigared until an acceptable design is achieved. Thcn subwatershed information is entered foc the next structure and rhe process is repeated until rhe enrice design of a stormwater, erosion and sediment comrol system ís completed.

The dynamic nature Df rhe design process will change rhe way you work. We have experienced large inereases in producrivity.

Structure Types N u11 S,ruc'ure The Null structure is used to output data at a specified location. It can also be used as a place-holder whece alternative control structures can be substituted foc the Null structuce. This enables the user tú determine the effectiveness of alternative controls, at a specific location. versus having no control.

Pond The Pond structure rype can be used for a sediment basin, oc retention basin if only hydrology is being used, a sediment trap, and an elongated sediment contcol such as a terrace oc bench with a controlled outlet.

Sil, Fente A silt fence (oc filter fabcic fence) is a structure thar is located in series on the flow path of a slope oc at rhe lowec section of a slope. In series, it reduces the slope lengrh, L, in ,he RUSLE algorirhm. A silr fence creares backwater,

thereby reducing transport capaciry and enabling sediment deposition of

eroded particles.

Graso Filter A gcass filter is a vegetated filtec. Ir is only listed as an option when sedimen­

tology is enabled.

Poraos Rock Check D.m

The check dam is a porous rock check dam !ocated in a channel.

Nonerodible Channel The nonerodible channel is simply solved using Manning's equation and the continuiry equation. Ir is used foc concrete channels and cornmercial channel protection products. such as gabions, concrete blocks, etc.

56 Erodible Channel A ehanne! eonsisting of bare soil or spoil is mode!ed as an erodible ehanne!. The limiting permissíble velocity mechad is used mar accornmodates [he design of channels conveying bath cIear and sediment-laden water. Various cornmercial produces rhar base their design on a specified critical velocity can be designed using rhis algorirhm. Erodible ehanncls are often designed ro convey sediment-Iaden water to sediment controls.

Vegetated Channel A vegetated channel is a grass waterway. Ir is used ro permanently stabilize areas during the final phase of reclamarían oc site deve1opment. Designs are based on channel stabiliry and capacity requirements.

Riprap Channel Rack ripeap is used to stabilize a channel conveying a large quantity of runoff 00 sreeper slopes. It may be a temporary oc permanent channel stabilization merhod.

Culvett Sizing Culverts are used ro convey runoff benearh roads. The culvert design rourine sizes the pipe based on headwater, tailwarer, pipe characrerisrics, and peak flow requiremenrs.

Plungc Pool A plunge pool is ofren used ro dissipate enetgy at the down gtadient ourler of a pipe ro avoid deve!oping a seout hole.

-

57

Pond Design A sediment basm is one of [he mon common sediment control methods used [O reduce peak flow to oeae pre-devclopment flow conditions. reduce [he sediment load, and reduce total and setdeable sedimellt concentrarion emanat~

ing from a disrurbed sire. The sediment hasin romine is also applicable ro estimating me effecciveness of sediment traps.

The effectiveness of a sediment hasin is a function of me shape of me inflow hydrograph and sedigraph, size and depth of me permanent pool, length to width ratio of the basin, che inflow partide size distribution, and che type and loeadon of discharge devices.

The primary funccions of a sediment basio are to reduce rhe peak flow and [he dischatged sediment load. A good dcsign basis is to reduce the peak f10w

discharged froro rhe basin during development ro below rhe pre-development levd. Various sediment srandards exisrs. Mining and sorne land developments have the standard to reduce the peak setrleable solids concentration generated by me 10 yr-24 hr design storm to 0.50 mili or 1m. Other regulations require an 80% sediment trap efficiency.

There are two basic inputs needed in the pond routine: (1) to determine storage from an elevation-area rclationshipj and (2) a stage-discharge relation­ship. The elevation (stage)-capacity relationship is determined from user input of elevation-area foc rhe pondo The overall stage-discharge relationship is determined from the combined stage-discharge relationship for all individual spilIways and is used for routing me inflow hydrograph through the pondo

Input parameters are:

• pond elevation-area

• spiIIway e1evation-discharge (for each spiIIway)

• a dedica red volume for sedimenr srorage (six alternative methods)

• pond dead space (short-circuiting)

Elevation - Area The screen shows the two primary input categories. capacity and discharge. and me inflow design ¡nputs for discharge and sediment concentrations. Click on Capacity and entee the elevatíon-area values. from the bottom of the pond

to the topo

Notice that pond capacity values are automatically calculated. Once the SEDeAD 4 user gains experience in the design of ponds, thcsc values will provide information on [he associated height of the embankment needed to

meet vuious emueor reglllations.

58 00 chis screen is where a desired Stage Increment may be entered, and [he rabIe ro view (inpur oc calculared elevacion-area values). The Input rabie is used ro enter additional elevacion ~area values. The Calculare rabIe provides calculated elevarion-area values foc (he specified srage incremento The calcu­lated values also provide irnmediate pond design guidance ro me experienced user. Click 00 calcuJarc lO obrain incremental elevarion capaciry values. C lick 00 graph [O view me eJevarion-capacicy relarionship.

If rhe SED-ACAD interfaeed is used, simply enrer rhe top width of the dam, fronr and hack sideslopes and meo dick on [he elevation contour of one side of the dam. Nexr click on rhe orher side of the centerline of rhe dam and the

embankment volume and elevarion-areas will be drawn and automarically calculated.

Once (he user draws (he centerline and rop width of me embankment, and front and back sideslopes the area foe each selected elevation can be digitized or the SEDCAD-AutoCAD interface program can be used. These are input inco SEDeAD 4, and rhe elevarion-capaciry relationship for the pond is derer­minecl.

Stage Increment The pond stage increment is used ro specify [he reponing increment foc rhe pond capacicy. Since side slopes of excavared ponds are relacively consrant only a few inputs are required into (he elevarion-area rabie. For non-excavated

ponds, more &equent elevations are recommended te berree determine rhe elevation-capacity relationship.

The srage increment default value is 0.5 fr. which works well for dam heighrs of 15 10 30 fr. For dams aboor 10 fr in heighr, a stage incremenr of 0.25 is suggested.

Pond Spillways There are 9 principal spillways oprions, an Emergency Spillway, and an oprioll ro input your own elevation-discharge values available 00 (he Pond Discharge screen. The primary principal spillways are:

• Drop Inlet

• Straight Pipe (exacdy like a cu}vcn, execpt pipe ruameter is input)

• Perforared Riser (a drop inler wirh perforarions)

• 4 rypes of weirs (Broad-crested, Sharp-crested, Side Contracring, and V­

norch)

• 2 rypes of siphons (Fixed Siphon and Floaring Siphon)

The three primary principal spillways are a drop inlet, straight pipe and a

perforared riser. The drop inler and the straighr pipe have tradirionally been

-

-

-

59 rhe mast popular principal spillways. More recently, we have been reCOffi- .

mending consideration of rhe perforated ciser and rhe combination of a straight pipe with a siphon tube. Both rhe perforated riser and rhe combina­don spillway provide che added advanrages of a passive oc conrrolled dewater­ing system.

Pond Spillways, Drop Inlet Inputs for the drop inlet are:

• diamerer of rhe riser

• height (length) of the riser

• barrel diamerer

• length of the barre!

• barrel slope

• Manning's n of rhe barrel

• elevation of (he top of (he cirop ¡nlet ciser

The design discharge is determined from rhe minimum flow associated with rhe discharge equations of weir flow, orifice flow, and pipe flow. Pipe flow is based on {he elevacion difference between rhe water stage and rhe outlet. Head drop from (he top of rhe riser is determined from me riser heighr, barrel lengrh, and barrel slope. Note rhat two drop inlers can hav.e idenrical inler elevations bur one may be located nearer rhe embankmenr rhan rhe orher, such

mar me riser heighrs of rhe two drop inlers may differ.

Pond Spillway, Straight Pipe The algorithms ro determine me elevation-diseharge relarionship for rhe straighr pipe are identieal ro those of rhe eulvert rourine, exeept rhar a pipe size is specified. The eulvert routine determines rhe minimum size tequiremenr for specified design parameters. Input paramerers for the Straight Pipe spillway

are:

• pipe diamerer

• pipe length

• pipe slope

• Manning's n of the pipe

• ¡nven elevaríon

• entranee loss eoefficient

• tailwater deprh

r~ H~

I

1---___ . Le'.t¡lh _ -------J

C ... lv"rt Nomenclalure '

60 Pond Spillway, Perforated Riser

Design mputs foc che perforared ciser are nearly identical ro thase of rhe Drap loler, exeept thar round holes are added at specified elevacions. The number of holes at all specified elev3rions muse be constant, e.g. 4 holes per e1evaríon .

The size of holes is speeificd 00 rhe e1eya,ioo-diseharge rabIe by c1iekiog a' rhe input lacatian foc each e1evarian where holes are needed and cyping in che hole ¿¡ameree, in loches.

Perforated tisees are used foc passive dewatering. Several states require mar che portian of che permaneor pool mar is ro be dewatered muse be achieved in 2 ro 7 days.

The rule-of-,humb ,har wc use is ,har 60% of ,he dewa,ered yolume should be eomple'cd io 24 hours. aod ,ha, the remaioiog yolume ro be dewatered should occur in che next 48 ro 72 houes. The reasoning is thar a convecrive storm can Qccur rhe next afternoon oc evening, chus che requiremenr foc 60% dewatering io 24 hours. A frontal srorm usuaUy oeeurs 00 more frequendy man 72 ro 96 houes, chus the remaining dewarering should occuc during chis time. The tradeoff considers:

• slower dewarering (O achieve better sediment trap efficiency and lower

sediment concentradon during dewarcring

• [he need ro have storage capaciry prior [O me nexc seoem ro achieve

grearer retemion cf che IlCX[ inflow hydrograph. and chus berree ~ediment trap efficiency of (he nexc seoem eveDe

Pond Spillway, Weirs ...., Input foc all weirs is simply che weir e1evation and weir length oc notch angle. .......

SEDeAD· WEIR CONFIGURArtONS

Sharp Cresle:d Wafr Sida Contraded WelC'

~ (Must be vcnlilaled)

Broad CreSled WeIr

Broad-crested Weir

Sometimes a single spiUway will he used and modeled as a hroad­crested weir. This algorithm is a1so useful in me desigo of me ouder of a pluoge pool eoergy dissiparer.

Ir should be nored mar [hece is a difference bctwcen a broad-

.~ eres red weir and che emergency spillway a1gorithms. The

elevation-discharge relationship foc che broad-crested weir ís simply [hat discharge is direcrly proportional to the weir coefficient. weir length, and headwater; whereas [he emergency spillway coutine generates backwa[er curves based 00 the resistaoce ro flow aloog ,he cootrol (Jeyel) secrioo of the spiUway.

--

---

61 For a short ccest length, an emergency spillway elevation-discharge will be similar ro thar of me broad-cresred weie, but foe longer lengrhs the emergency spillway discharge will he less rh.n rh.r of rhe bro.d-cresred weir.

Sharp-crested Weir A sharp-cresred weir is primarily used in channels and foc flow measurements. Ir is also used as a flow splitter.

Side-contracting Weir A side-contracting weie simply has vertical sidewalls.

V-notch Weir The V-norch is ofren 90·.

Pond Spillway, Siphons ¡npurs for hom me flXed and floa<ing siphon are idenrical. The floa<ing siphon skims just below me surface of me pond water, whereas che fixed siphon ¡oler elevarion IS specified by me desigo professionaJ. Design paramcrcrs are crest, ¡olet and ouclet elevarion and pipe djametec. length and Mano¡og's n.

The rhree mase important desigo parameters are che ccest elevarion, ¡oler elevarion and the pipe d¡ameree. As the water levd in a pond is rising, no discharge will occur until the cresr elevarion of me siphon is ceached. There­fore, if the ccest is located relarively high. smaller stOfms may not raise the pond water elevation to a leveI that facilitates dischacge through the siphon. The siphon inlet obviously defines were dewatering stops. Pipe diameter is rhe conrrolling mechanisrn foc discharge rate.

Siphons are used ro provide dther a passive or active dewatering capabilities. Siphons are recornmended and have the same benefirs as orhec dewarering devices. To operare passively, the pipe oudet is open, and ro operare actively a valve is manually operated. Benefits of an active siphon are that me water qualiry can be te.ned prior ro discharging. For example, storrn warer remaining in me pond helow rhe primary spillway (drop inler or straighr pipe) can be treated for iron, manganese, pH, heavy rncrals, nurrieors, oc ro flocculare fines, etc. Once the required water qualiry is achieved, the valve is opened allowing a conrrolled release.

Fi~ed Siphons Our most receor design philosophy is to use two siphon rubes. The crest of the larger djametec sipholl is located 2 ro 3 fr below the primary spillway and ¡ts inlet is 3 ft above the sedimenr srocage elevarían. The smaller siphon crest is loc.red 4 ro 5 fr below rhe primary spillway and its inler is only .5 to 1 fr above rhe sediment storage e1evatíon. The lower (smaller) siphon is used for smaller

62 sroems and to slowly dew3rer [he remaining volume frOID medium ro large storms, whereas (he higher (larger) siphon passively dew3tcrs medium to large seoems at a higher ratc.

Floating .Siphon The floating siphon functions like the flXed siphon except that the inlet maintains a constant elevation below [he surface of [he water (usualIy 9 ro 12 ioches), thereby always discharging [he cleanest water. Research has Dor beco complered ro accouO[ foc (he entite benefir of a floariog siphon. Ir IS modeled very similarly ro che flXed siphon.

Pond Spillways, Emergency Spillway In the emergency spillway algorithm, backwater is determined from the height of water within the pond discharging through the emergency spillway. Required inputs are:

• elevation of [he iovere oc ccest (ho([oro of me emergency spilJway)

• ctest length (lengrh of (he control oc level section in rhe direcrion of flow)

• botrom width, and right and left sideslopes of the emergency spillway channel

Estimating Initial Pond Spillway Elevations and the Top ofDam To determine che intial estimare of che emergency spillway location, mulriply the runoff volurnc by 0.75. View the calculated capacities from the Elevation· Arca screen, and note where 75% of the runoff volume would OCCUf.

The top of dam should provide 2 ft of freeboard. The flow rhrough the emergency spillway is often 0.5 to 1 ft deep such that the top of dam should be berween 2 and 3 ft aboye the emergency spillway.

The principal spillway is expeered ro be 1 to 3 ft be/ow the emergency spillway for many dcsigns.

Pond Design Example For the Pond Design Example, ,he runoff volume from the eombined dis­turhed and undiSlurbed SWS's is 3.83 ae-fr. This can be obtained from the Slrueture #1 SWS repon or from ,he SWS eombined hydrograph view. Mul,iplying 3.83 times 0.75 results in 2.87 ae-ft. Looking at the ealculated elevations, norice rhar the 2.87 capaciry is available at an elevation between 2534 and 2534.5. Sinee rhis is juSI an approximation method, se/eC! 2534 fór the initiallocation of the emcrgency spil1way.

--

--

Addiog 2.5 fee, 'o ,he emergeocy spillway IDeario n results in the top of dam a' 2536.5. Make rhe ioirial selection foc me principal spillway 3 ft below ,he emergeocy spillway, ar elevarioo 2531.

Estimating the Crest Length of an Emergency Spillway The erest leogrh eao be estima red by usiog ,his rule-of-thumb:

• crest length approximarely equals embankment width + 5 times rhe difference in elevation betwecn (he rop of clam and (he ¡overt of (he emergency spillway

63

For ,he Pood Desigo Example, rhe embankmeor wid,h is 15 fr aod the elevation difference i5 3 ft. Therefore rhe first estimare of (he crest length is 15 + (5 X 3) = 30 fr.

BoHom Width and Sideslope Sizing for Emergency Spillways The borrom wid,h aod sideslopes of rhe emergeocy spillway are based 00 a tradeoffbetween the potenrial foe catasrrophic failure ofrhe embankrnent and rhe cost of an emergency spillway. We usually recornmend an over-design of (he emergency spillway to provide additional protection againsr a catastrophic F.tilure.

Our recornmendation is ro assume thar rhe principal spil1way(s) are clogged and the emergeocy spillway must pass ,he 100 yr-24 hr desigo storm wi,h ooe foar of freeboard. This may seem drasric to sorne design professionals. but it adds only a very marginal incremental cost to the enrire projecr and provides a needed element of safety.

Pond Spillways, User-defined Al,hough SEDeAD 4 .eeommod.,es 10 spillway eoofigura,ioos ,here are always situations that the design professional encounters rhar are nor direccly covered by SEDeAD 4. For these siruarions. elevations and associated discharge values can be directly entered.

64

Pond Sedimentology

Sediment Storage SEDCAD 4 internally redefines the zero stage (lowest input elevation of the pond) ro correspond ro (he rop of (he designared sedimenr storage volume. It is assumed thar a11 sedimenr thar is deposired across me elevarían designed foc

sediment storage is retained and no resuspension of sedimenr is allowed.

One implicarian of llor allowing resuspension of previously deposited sedimenr is (har (he dcsign professional needs to Ioeare spillways sufficiendy aboye me rop of (he sediment storage elevation such mar velocitÍes into (he spillway are

reIatively small. We suggest rhar a minimum two foar elevarían difference exisrs between me ¡overt of me principal spil1way and (he rop of (he sediment storage area. If a sIow passive dewatering syS[cm is employed, (he elevarian difference can be reduced ro 0.5 to 1 fr, depending upon the size and flow rate of the lowest dewatering inIet.

SED CAD 4 will check to determine if the pond capacity is adequate to store the calculated sediment load from the design storm. If the total storage capacity of me pond cannor contain the designated oc calculared sediment srorage, SEDeAD 4 ~ill nor reser me zero stage. Qtherwise, [he zero stage will be reset. If any spillways weee Iocated wirhin rhe new sediment stoeage volume, a warning message will be displayed.

There are 6 options for esrimaring rhe needed volume for sedimenr srorage:

Do Not Reset Zero Stage The Do Not Resct zero option should only be used when the user has provided sufficient sediment storage below rhe lowest elevation input in rhe elevarion­area relarionship. This option is rarely used except in specialized applicarions.

R Annual Method The average annual R method is used to determine the sediment storage needs based on the ratio of the RUSLE annual R factor to the calculated R storm

value and the rhe anuual sediment yield ro the storm sediment yield.

Since storm sediment yield is calculated, R stoem is calculated as a function of the rainfall amount and disrribution, and R annuaI is input by me user, then rhe only unknown is me annual sediment yield.

Sediment Requirement = Y * (Ss * (RalRs))

where Y=number of years, Ss=predicted storm sediment yield, Ra=R annual, and Rs=R storrn. Y and Ra are input values.

r

r

65 Dislurbed Acres Melhod This sediment storage volume methad is based on using a rule-of-rhumb, such as 0.125 ae-f, of sedirnent storage per acre disturbed. When ,he SEDeAD 4 usee checks (har a subwatershed is disturbed (in (he subwatershed input sereen) , then aJl of ,hose des igna,ed disturbed areas, up-gradien, of a sediment

control structure hut down-gradient of che previous sedimenr control struc­ture, are added together and (his cummulative area is multiplied by (he specified rule-of-thumb fac'or.

Contributing Acres Method This methad is similar [O me Disturbed Acres mechad, but (he total contribut­ing area (regardless of disturbed status oc any up-gradient sediment control) is used instead of only me designated disturbed areas.

Inflow Sediment Tons Method This mechad i5 only used in coal mining in Kentucky. A multiplier of 0.000883 is me default valuc, and is multiplied with the inflow sediment tonnage.

User-defined Sediment Storage The user simply enters the ac-ft of pond storage to be dedicated to sediment srorage. The easiest way ro use this is to review the calculared clevarion-area­capacity rabIe and nore ar what elevarion sedimenr will be removed from me sedimenr basin. Enter me corresponding ac-ft of srorage.

Dead Space Dead space refers ro the volume of a pond rhat does Dor signifjcandy contrib­ute to mixing. For a pond with a length [O average width ratio of 2: 1 at the

principal spillway, a dead storage space of 20% is recommended. Leng,h would be defined from ,he inle, of ,he pond ro the principal spillway inlet.

Wid,h is generally perpendicular 'o ,he leng,h. For al: 1 ra,io we suggCst using 30%.

66

Pond Design Example

1"~400' 10' Con tour Intervol Sediment 8asin Design Exomple

Problem Statement The site is in (he northwesr U .S. Thc down­gradient watershed wiU remain forested while [he up-gradient warcrshed is clear-cut. A sedimcnr basin is proposed ro be buile in che lower portian Df me down-gradient water­shed in anticiparían of furrher silviculture operations. After me up-gradient watershed is reestablished, the lower watershed will be clear-cut in three secrions. The concern is

for rhe water quality of the small trout stream irnmediately down-gradient Df che sedimeor hasin. Design a sedimenr basin thar wiU effecrively reduce che sediment load for the 10 yr-24 hr design srorm. For this example the analysis will be conducted only fOI [he up-gradient disturbance.

The dcsign informadon char needs ro be enrered prior ro che dcsign of che sediment basin is che:

• • • •

Storm Input

Eroded Particle Size Distribution Nerworking

Subwarershed Information

Storm Input InformarÍon is needcd abom (he stocm distribution, i.e. Storm Type and the rainfall amount associated with (he 10 yr-24 he design storm. The Storm Type is an NRCS

Type II distribution. Referring to the NOAA atlas, the rainfall amount for the 10 yr-24 hr storm is 3.2 inches. We suggest the NRCS 49 pr Disrribution.

Particle Size Distribution The eroded particle size distribution is input by first selecting (he sedimentol­ogy option buc(on. Click (he Particle Size Distribution burton, then the Creare New hurton. Prior to entering (he data, (he filen ame and first distcibution label will be prompted for. Enter the following data:

,.....

Filename (exampJe): Westt'rn sed basin ex Label: (asshQwn below)

Percent Finer (%) Percent Finer (%) Partiele Size (mm) Subsoi[

4 100 2 90.0 I 78.2

0.5 68.5 0.25 63.4

0.125 53.4 0.063 44.3 0.031 36.6 0.016 28.7 0.008 20.6 0.004 14.4 0.002 6.6 0.001 O

Networking

Topsoil 100 91.6 80.4 72.1 65.2 54.1 46.0 39.8 29.2 18 .2 II.! 4.2 O

67

Networking for mis example is suaightforward - simply cliek on the Network­ing bunoo, [hen click me Add a Structure bunoo, and selecr a Pondo Since only one structure is used, structure #1 auromatically flows ro che outlet (designated as zero) and no Muskingum rouring between structures 1S nceded.

Subwatershed Information

Two subwatersheds are specified foc (his example. as shown in (he figure. SWSl is assumed ro he cIear-cut such thar all cimber i5 removed, 20% residual cover remains on the foresr floor with stumps left in place, and numerous random surface depressions 2 to 6 ioches deep exis to SWS2 is undisrucbed foresto

Subwatershed Hydrology Inputs Area SWSl: area is 16.7 ac. The area can be determined from various methods. software paekages, or wi,h ,he SEDCAD - AutoCAD (SC-AC) interface. SWS2: area equals 61.7 ae.

Time of Concentrabon SWSl: the hydraulically longest flow path is es timated to be 480 ft of overland flow and ehanne! flow lengrh of abour 700 fe. The vertieal e!evarion differenee for me overland llow segment is 70 ft, and the vertical drop is also 70 ft for me stream flow pa,h. Flow path 1: To enter this information and determine the time of concentra­tion, cliek the edit button, cliek Add a Flow Pam button, seleet Nearly Bare ... , entee 70 under Vertical Distance. cIick or tab to Horizontal Distance and

68

Te Chcnnel Ao_, --1ffitf

Ao"

enter 480. The slope, overland flow velociry and incremental time of concentration are displayed afrer tabbing or pressing the enter key. The slope, overland flow velocity, and time of concentration foe

rhe overland flow portian are 14.58%,3.81 fps and 0.035 hours, respeerive!y. Flow pam 2: Next aeeount for the ehanne! flow portian cf [he time of

concentration. Click on Add a Flow Parh bunon, selecr Gully, diversion ... , tab over and enter 70 for [he vertical elevation drop,

tab and enter 700 foc me horizontal distan ce, and then [ab to view [he

incremental and total time

fe Chann.el 1'10"

IM " 400' 10' Co~tO<Jr l"terw:al SublOOte.-shcd Te ond Ro~til'lg

(,.)

of concentration foc SWSl. The resulting time of concentration is 0.055

hOlles.

SWS2: [he time of concentration flow path consisrs cf an overland flow

category of heavily forested land with a vertical drop of about 60 ft and a

hocizontal flow distan ce of about 280 ft. At ficst eonsidecation, one may figure a longer flow path but ir is difficult ro see small gullies on a scale of 400 ft pec ¡nch. The ncxt flow patb is #8 foc a vertical drop of about 80 ft and a horizon­tal distance of abour 400 ft. This is followed by a vertical drop along me main s[ream of 50 ft with a horizontal dis[ance of 1100 ft; using category 8.

69 Category 8 is recommcnded foe mast channel situations, since (he vc10ciries associated with category 9 are only representarive of streams with ver}' efficienr How conveyance. The rime of concentration is 0.126 hOlles.

Muskingum Routing SWS 1: Routing from the oudet of SWS 1 to SI is needed since the oudet of [he subwatershed is llor at the structure. To accomplish [his click on [he edit bunan foe rouring from subwatershed. click on rhe calculator, click on Add Flow Path. Selecr #8, enter 50 foc vertical and 11 50 foe horizoncal, which results in a Muskingum K of 0.051 and X ofO.393. So the hydrograph exiting SWSl will he slightly ::tttenu:ued between SWSl oudet and [he eonance ro [he pond at SI. SWS2: There is no routing needed since the oudet of SWS2 is at the inlet of SI.

Curve Number SWSl: The curve numher can be esrimared by dicking on rhe edit bunon. Select Hydrologic Soil Group B. since this is a sandy loam. Select Other Agricultura! Lands. There is no description [har exaccly Bes [he "clear-cut" land use with 20% residue and 2 to 6 ,nch random roughness. The brush, brush/weed. brush major elcment may be applicable if me residue. consiscing of cut limbs. is in contact with che soil surface. The curve number for brush is 67. Since cut limbs would not afford the same protection of me soil or sigoificantly inerease the infiltration rate a oearly bare soil condition rnay be more appropriate for this exarnple. Under the Agricultural category, fallow bare soil has a CN of 86 and under the Urban category. newly graded lands also have a eN af 86. These values are expected to be a bit too high since significant surface storage is expected io che depressions and the trirnmed limbs stilI provide sorne interception of raiofall. Depending on the coodicion of ehe clear-cut arca, a eN of perhaps berween 82 and 84 may be mase representa­tive. For this example. rype in a CN of 83. SWS2: The Curve N umber for a heavily forcsted watershed can be obtained by clicking the edit button. proceeding to Other Agricultural Lands. selecting Hydrologic Soil Group B. and then considering woods in fair oc good con di­tion with CN's of 60 and 55. respectively. The forested watershed is eonsid­ered to be between faie and good coodition so a eN of 57 is used for rhis example.

Unit Hydrograph Shape SWSl: The dimensionless unit hydrograph shape is expecred to be fast due to the land use previously described. Sinee the time af concenteation is less than

0.126 hours the unit hydrograph methad will not be used - instead the instantaneous runoff procedure is employed. Thus. the unit hydrograph seleeted is noc used in calcularing che storm hydrograph for SWS's with a time of concentradon ofless [han 0.126 hours. SWS2: The dimensionless unit hydrograph shape is cansidered to be slow

70 which simulares [he high infiltrarÍon rate, storage and rdease of runoff in che dctritus and inrerflow which is characteristic of heavily forested warersheds.

Subwatershed Sedimentology Inputs K Factor SWSI and SWS2: An estima<e of the K factor (soil erodibility) can be obrained by clicking on ¡ts edir burton and selecring me row concaining sandy loam which yields a K factor ofO.24.

Representative Leogrh and 510pe The represematÍve SWS length and corresponding slope gradient can be estimared by viewing [he flow of runoff at severallocations within che SWS. The lISey is cautioned that the longest Jlow path should not be used. A representa­tive length is needed. The applicable definition to keep in miod in determin­ing che represcntarive lengrh is (he disrance from che origin of overland flow ro where concenrrated Row oc where significant deposition Decurs. There are sorne opporrunities foe significanr deposition in a landscape rhar has approxi~ mately 20% ground litter. A1so it should be kept in miod that the data base has slope lengths to about 400 fe. A longer slope length may be realized, but me slope would almosr have to be regraded or rerraces urilized. such as during surface mining redamation.

SWSI: Viewing the example figure, the representative slope length is probably between 200 and 300 fe. Enter 250 fe for RUSLE Length and 16% for the represenrarive gradient. 5WS2: gullies appear to be spaced furrher aparr then in SWS 1. But in an undisturbed SWS mar is heavily foresred, rhere are numerous opportuniries foc significanr deposirion. Since rhe e factor will be low for an undisturbed fores[ [he sclectÍon of L and S are nor especially crirical. Enter a Representative Length of 150 and a Slope of20%.

C Factor 5WSI: To estimate the C factor, c1ick the edit button, select the C factor table for Mechanically Prepared Woodland Site. Considering a site in fair condition, select Fair, no cover from the Soil and Weed Cover list. Click on the 20% Ground Cover and the Disked, raked or bedded row. A C value of 0.40 is selecred. 5WS2: the Undisturbed Forest C factor table is applicable. Select the row with 85 to 75% effective canopy, which corresponds to a 70 to 40% forest litter, yielding a C factor of 0.003.

P Factor SWSI and SWS2: accept the P factor of 1.0.

Disturbed SWSI: is flagged as disturbed, strictIy to provide ioformation for the option of using a "disturbed area" rule-of-thumb method of specifYing sediment storage for rhe sedimenr basin.

-

r r

r

r

r

7I Graphs C1ick on the Hydrograph Button. The hydrograph from SWSl routed to SI combined with the hydrograph from SWS2 yidds a peak flow of 29 .82 cfs.

Contr1butfng sws HydrO~h{l, for StructlJre' 1 ¡ __ -"ld::O':;:1 notlnelud. upstre~.!'~ _ ___ j

, 30 --.--.- - . -.~ - - .. - ... - .... - • • • Combitle<l SWSpeak f lcrwf 1

r · l · f·~'·"·H···· · ·· rI,,·.T'+L ¡ <5 10 .• ¡._ ~ .... ·:-· ·:- · -:-·{·+ - t· - t -- ¡-+ -~ .:---:--- I

o j¡ ' \~b~LJ ¡ jJj • ¡ I 9 101112 131A I5 1811,e~ ~~n~~~1

T~I ~~) j

-= ~~! , 1.«01 j

,

Structure #1 SWS Report Now go to reports and sdeet Strueture #1 SWS's. Again the peak flow is 29,82 e&. The 17.6 ae clear-eut site eontributes the majority of runoff wim a peak flow of 28.38, whereas me 6 1.7 ae forested SWS has a peak flow of only 5.53 efs, The eombined peak flow is 29.82 . This is not simply me addition of me individual peak flows, Slnce [he time to peak foe [he {wo SWS's is differenc, and SWS 1 is ro~ted ro SI attenuating the peak flow from SWS l . Runoff volunies for SWSl and SWS2 are 2.24 and 1.59 ae-ft, respeetively.

The sedimentology portion of (he ourput shows rhar almost a1l of (he sedimenr is associated wirh (he clear-cut site¡ 424.6 teos compared to [he 1.0 ton generated [rom the forested site. Similarly, che peak sediment concentration and settleable solids for the clear-eut site are 236,802 mgll and 143.42 mili , respectively.

The forested site peak sediment concentration is l.317 mg/l and settleable solids peak c:;:oncentration is 0.59 milI. The effeet of

-.,

... . ,

~.

, ,

"'. . , ,

Subwlltershed Hydrology Detall: NS Ar.. 1lg:' ... 1If .... , ..... ~ ..

~ ~:oo ~. he:) ñ: . ","l "="" '''''' ... . '" .... n= M "'~

,,, .,,'" .n. .= .000 ,.,.= • ." ,."

n .... n.., u,

Subwatershed Sedimentolol1V Detai/:

.. " L'IO "'" , , ... "' ...... w ... _ kilo""', "'" (a"",) "-~ ~~

,.., ., .. ""DO "'" .. "'" , .... , .~, ". .. 143.42 , .. " ., .. ".DO "'''' ..... , .... , '.0 L317 ." ."

~" no.D58 nl.a:J $3.31

dilution can readily be noted by viewing me pond inflow sedimem coneentra­tioo which represents the commingliog of the eilluent from both SWS's .

Also note (hat ti~e of concentradon and Muskingum SWS routing details are

located on this reporto

72 Pond Inputs: Hydrology

Elevation-Area Referring ro the example figure, an embankment has beco drawn connecting the 2520 e1evation for rhe cenrerlil1e of rhe emhankment. Also [he rop width and sideslopes are drawn. The inirial cmbankment is 20 fr high. Since chis is a first estimare of me designo 10 fr elevarions will be used.

Elevation-Discharge

•. ". , S6i.dr'¡;;n' ~:;.": T t~l JU..it~I I~:t¡~\1

.. 125201 D.OCII ' 0 000

i --=:i~~=: = ~~I -: 1~j

This example will initially employ an emergency spillway and a drop inlet.

Emergency Spillw.y 1'0 input spillway par.metets, c1ick on rhe Oischarge burron, c1ick Add, and ,e1ect an Emergency Spillway from the Iist of spillways. For rhis design example, use an emergency spillway e1evation of 2534, and a lengrh of 30 ft. The emergency spillway will usually be placed adjacent to the dam.

For rhis design example, use an initial borrom width of 8 fr, and 2: 1 side slopes.

Orop Inlet For me inirial Pond Design Example. drop ioler design parameters are:

• 24 ¡neh ciscr diamerer • 10 fr riser heighr • 18 inch barrel d¡amerer • 80 fr barre1lengrh • 2 percent barre! slope • Manning's n ofO.015 (corrugated metal spiral barre1) • iolcr elevarion of 2531 -

-

-

r

r

-

Pond Inputs: Sedimentology Sediment Storage

73

For this example. click 011 Average Annual R, then entee an R annual oE 20 and 2 years of sediment storage.

Dead Sp.ce Default to (he 20% dead spa~ vaJue, since [he length to width ratio is greater man 2:1.

Results and Discussion Once a11 input parameters have beeo cnreced 00 me Pond Design Screen, SEDCAD 4 ,ulOrnatically calculates all results.

Severa! key output parameters are displayed 00 rhe design screen. The peak flow was reduced frorn 29.82 to 17.31 e&. The pre-development peak flow was 7.03 cfs, which is abour one half rhis discharge. Sediment trap efficiency is 77.1%. Eflluent concentration forTotal Solids is 35.724 rngll. which consises of silts and days. Peak seuleable solids are 1.79 mIlI. The peak elevation of me 10 yr-24 hr desigo SIorm is 2532.32 fr.

The peak discharge should be reduced 10 pre-development conditions. Sediment trap efficiency should be increased to 80+ percent and peak emueor setdeable sediment concentration should be reduced 10 below 0.50 rnlll. A cost-effective way to try and accomplish mese objecuves is ro use passive dewatering. The simpleSl appreach is to replace me drop inlet wim a perfo­rated riser.

Change the drop inlet to a perforated riser by clicking on the Design buuon.

then click on the drop inlet pull-down triangle, and select a perforated riser (instead of the drop inlet). Riser and barrel parameters are idemical to [he drop inler parameters, and two B1. inch holes are placed every foor beginning at elevation 2527 (4 elevations' .

74 With (he perforatcd riser, (he results are changing in (he righr direcrion. Peak discharge is now 7.88 cfs which is nearly rhe same as me pre-developrnenr discharge. Peak serrleable solids has been reduced ro 0.24 rnl/I which is less [han rhe 0.50 milI standard. Trap efficiency increased from 77.1 to 81.0%. The oeher advantage is thar the peak elevation decreased frOID

2532.32 fr ro 2531.56 fr, which is a reduction of abour % fr. Thus, (he advantages of a

passive dew3tering system are evident. Peak flow, serrleable solids, and peak elevation are a1l reduced and trap efficiency is increased.

Contrasting Permanent Pool and Passive Dewatering

Using me Pond Design Example numbers:

Sediment Storage (ae-fe) Permanenr Pool (ac-ft) Permanent Pool Elev Peak Discharge (cfs) Sediment Discharge (tans) Peak Sedimenr Cone. (mgll) Peak Sedimenr Conc. (milI)

Drol! lolet 0.19 !.l8 2531 17.31 97.5

35,724 1.79

Perforated Riser 0.19 0.16 2527 7.89 80.8

46,457 0.24

24VW (mili) 1.07 O.ll Peak Elevarion 2532.32 2531.56 Trap Efficiency ('lo) 77.08 81.00 Dcwarering Time (days) 0.60 2.47

Ourpur design paramerers for bom rhe permanenr pool (drop-inler) and passive dewatering (perforated ciser) principal spillway options are shown. The

advantages of a passive dewatering system are evident. The permanent pool is rnuch smaller such rhar if an embankment were ro fail, only 0.16 ac-ft would be released versus 1.18 ac-ft in rhe drop inler siruarion. The peak discharge is

abour \2 rhar of the permanenr pool aptian. Trap efficiency is increased by nearly 4%. Peak settleable sediment effluent concentration is reduced by a

factor of7. Volume weighted average is likewise reduced. The only advantage of the permanent pool can be seen in the peak total sediment concentrarion, which is approxirnarely 36,000 rng/l for rhe permanent pool versus 46,000

-

-.

-.

--

75 rng/l foc [he passive dewarcring aprjon. This is due to me inicial dilurioo effecr cf [he rnuch larger permanent pool. The permanent pool is assumed ro consise of clcan water prior ~o [he design s[Ocm. Setdcable solids are nor as greatly affecrcd by dilurion, sincc [he faH velocity is so much greater than thar of cIay and very fine silt particles. Deposirion care facraes exceed [he dilurion effect foe settleable solids.

It should be nated rhar several interactions are being combined ro obtain [he final results. A larger permanenr pool provídes dilutioo of incorning sediment­ladeo flows. However, the larger permanent pool has disadvantages cf

releasing discharge at higher cates [han [he passive sysrcm. almost immediarely since no storage bclow [he ccest cf me principal spillway exisrs. Also, rhe permanent pool has the disadvantage of a geeater fall depth foe sediment particles ro enter (he sediment storage zone where they are assumed [O be

peemaoently trapped. These disadvantages ate manifested in a highee peak stage, higher peak discharge. lower overall scdiment trap efficiency. and higher settleable solids, peak and volume-wcighted emuent conditions. The advan­tage of the large pcrmanent pool is dilution of incoming sedimenc-Iaden water.

In contrasto the passive dewatering system has very liule dilutioo effect. but cspecially duriog early storm flows. a much shoner sediment fall depth. The disadvaotage of a much lower dilucion potential during the initial sedirncnt discharge combincd with a much lower dischaege, (i.e. through the lowest perforations, rcsults in a higher initial peak sediment concentratíon than thar af me permanent pool.

If this final point is only viewed in the perspective of actual peak values, than a very essential paim is míssed. Although me peak sediment concentrarian is higher for the passive sysrem in comparison to rhe permanent pool system, this higher value is associated wirh a very small discharge which is easily dilured upon entry into the fluvial sysrem. .

Additional Alternative Design Tradeoffi among dilution, sediment partide fall depth, as they alfect peak discharge, trap efFiciency, peak rotal sediment concentradon. peak toral sediment concentratÍon, peak and volume-weighted sertleable sediment concemrarion, etc. can be evaluated through basin parameter changes such as

storage eapacity for pcrmanent pool and sediment pool and rype, number, size, loeation, and configurarian of principal spillways.

76

Silt Fence Design A silt fence is effecrive if properly insralled and placed on the CQntaur. The ends of [he silr fence muse be instal1ed sufficiently upgradient of [he contour such rhar [he silr fence funcrions as a miniature clam and runoff i5 flor allowed

ro flow around (he edges. Obviously. if rhe silt fence is undermined, if runoff goes around rhe edges of the 5ilt fence, oc if [he silc fence is filled with sedimcm such [har runoff overfIows me fenec, ¡ts effectiveness may he significandy reduced.

Silt fence sediment trap efficiency is influenced by the peak flow, eroded particle size distrihution, slurry flow cate through [he silr fenec, and prior sediment deposition.

Silt Fence Design Example Silt Fence Example Problem Statement: A critical wetland habitat

is near a proposed highway construction projecr in [he coasta!

plains of Maryland. Sediment control is required to protect the wedand. Due ro the relatively smaU drainage

area and the clase proximity to the wedand, the use of a silr fence is suggested. The sail is classified as a sandy loam

SIL T FENCE / GRASS FIL TER EXAMPLE

and the hydrologic soil group is A. The vegetated areas consist of grass wirh

approximare 60 percenr ground cover. No orher significant vegeratian is presento Regulations require a 10 year-24 haur design storm.

The design informarion thar needs ro be enrered prior ro design af rhe silr fence is rhe:

• Storm Input • Particle Size Disrribution

• Networking • Subwarershed Informarian

----

-~

-

--

Storm Input Infarmarion is nceded foc rhe scorm rype and rhe rainfall amount associaced with (he 10 year-24 hour design stoem foc (he Maryland coastal plains area. For me coast ofMaryland, where chis project is locared. a Type 11 storm distribution is appropriate. The help screen for rhe lO year-24 hour design stoem in Maryland shows a precipitadon deprh of approximate1y 5.5 ¡Dches. We suggest the NRCS 49 pt Distribution.

Particle Size Distribution

77

The sedimentology apriao burton needs to be chosen foc any erosion oc sediment control applicarions and prior to entering eroded particle size data. Click the particle size distribution burton and then me creare new hurton. Enter rhe eroded partide size data for the subsoil at rhe site. (Refer to rhe Particle Size Distribution Laboratory Analysis procedure described in detail. If furrher assistance is nceded, picase contact Richard Warner.) Aceept [he deF.tult values for Specifie Gravit}' and Bulk Submerged Speeifie Gravit}'.

Filenarne (exarnple): MD Sandy Loam Label: (as shown b.Jow)

Percenr Finer (%) Particle Size (mm) MD Sandy Loam

4 100 2 96 I 74.6

0.5 62.8 0.25 48.4 0.125 41.2 0.063 36.2 0.031 24.2 0.0 16 18.3 0.008 16.2 0.004 0.002 0.001

Networking

12.8 10.6

O

The networking for this project is srraight forward, simply c1iek on rhe Networking bunon, meo click the Add a Struccure button, and selecr a "Silt Feoce". Sioce ooly ane structurc: is used, struccure #1 automatically flaws to the oudet (designated as zero) and no Muskingum routing is needed.

Subwatershed Informatioli Click on rhe Design burron. When the Strueture Design/Subwatershed sereen

78 appears, click the "Add SWS" burtan. The area. time of concentration, Muskingum routing parameters foc routing fram a suhwarershed outlet ro a structure, NRCS curve number, and unir hydrograph shape are input on rhis screen. Three subwatersheds are specified foc (his example. Since (he two pasrure areas are separared by disrurbed areas, these will be considered as separare subwatersheds. The inputs foc me mast upgradient subwatershed will be detailed from (his point an.

Subwatershed Hydrology and Sedimentology Inputs Enter (he following numbers for 3 subwatersheds:

Area Te Musk.K Musk. X eN UHS 0.88 0.017 0.057 0.203 49 Medium

2 2.20 0.040 0.012 0.256 77 Fast 3 1.24 0.012 o o 49 Mcdium

K Re!!. Len&th Rel!. Slo!!e !; l' PSD Disturbed 1 0.24 80.0 2.5 0.04 MD Sandy No 2 0.24 160.0 1.25 0.85 MD Sandy Yes 3 0.24 70 5 0.04 MD Sandy No

Notes:

• The warershed area is straight forvvard and can be determined from many places, or you can use the SEDCAD-AutoCAD ¡nterfaee.

• For [he time of concentrarían, me longest overland flow d¡sranee is abour 80 & and the change in elevanan is abour 2 fr. Overland flow will occur across pasruce land thar was described as having abour 60% ground cover. Click the edit bulton, click ''Add a Flow Path" bulton, selecr "Short grass pasture", enter 2 undee Vertical Distance, dick oc [ah ro Horizontal Distance and eorer 80, then click [he <COK" burtan. The time of concentrarían is 0.017 hours. The usee should be aware thar if [he time of concentrarían is less than 0.125 hours, rhen rhe unir hydrograph methodology is Dor used and instanraneous runofT is assumed.

Hint: To save input time jor small watersh~d, where the time of concentration is 1m than 0.125, simply type in 0.1 hour, and the result, will be the ,ame a, if a lower time nf concentration was calculated

• Routing from me subwatershcd outlet ro the silt fence structure is necessary. Whenever the subwatershed ouclet is not AT the structure, roucing is needed. Since all runoff is expected to be transported by

overland flow, routing will be done using the overland flow paths listed

in the calculation tableo Click on me edit bulton, men add a flow pam, selcct "Bare soil", enter a vertical drop of2 ft and a horizontal distance of 160 fi:. For the second segment of me calculations (routing mrough SWS3), add a (second) flow path, ,elect "Short grass pasture", enter 2 fi: vertical drop and 80 fi: horizontallength, and then click OK. The result is a Mu,kingum K of 0.057 hrs and X ofO.203.

-

--

--

--

----

--

--

• The curve number can readily be locared by a c1ick on ¡es edit burton.

Select Hydrologic Soil Group A as specified in the problem statement. The table Other Agricultural Lands lists pasture land. The fair condi­tion pasture land is chosen since [he problem statement specified 60% ground CQver and che Faje caregory is foc between 50 and 75% ground cover. A curve number of 49 is selected.

79

• The ¡ast cotry is che dimensionless unir hydrograph shape. A Medium response is appropriate foc pasture land in faie condicion o Note that since che rime of concentrarion is less than 0.125 hOlles [he unir hydrograph shape will not acrually be used.

Hydrology ¡npues foc the orher subwatersheds follows che same procedures. For SWS2, the disrurbed area, a curve number of77 (Drban Areas, newly graded area, HSG - A, or Cultivated Agricultural Lands, Fallow bare soil, HSG -A) is selected. A1so, the hydrograph would have to be routed from the outlet ofSWS2 to its structure (the silt fence) through SWS3 via overland Row. For SWS3. no Muskingums routing is rcquired since [he ouclcr of SWS3 is at che silt fcoce.

The subwatershed sedimentology inputs are the soil erodibility (K factor), representacive slope length, representatiye slope. coyer (C) facror, Practice (P) facror, and designation of which eroded panicle size distribution to use.

• To estimare rhe K factor (soil erodibilityL dick on its edit burtan and select sandy loaro which yidds a K factor ofO.24.

• The represenratiye length is obrained directly from the example figuce. The representatiye slope is also estimared from the example figure.

o To estimate the C factor for SWS's 1 and 3, click the edit burton, select

the e factor rabIe foc Permanent Pasture. click on percent Coyer and select 60, and select no appreciable canopy, yielding 0.042. For SWS2, select the e factor rabIe Values foc Bare Soil ar Construcrion Sires and then selecr rough graded fill , which seems ro besr describe an active consrruction sire.

o Accept the P factor default of 1.

• Since rhis is a small sire and has one predominanr soil rexture, simply select the only particle size distribution entered from the dropdown list for aH SWS's.

o SWS2 is flagged as disturbed to give us the option of using a rule-of­thumb merhod of specifying sedimenr srorage for rhe silr fence. The rule-of-thumb is usuaHy 0.1 or 0.125 ae-fr/ac disrurbed. SEDCAD 4

adds up the area upgcadicnt of eaeh struetuce when f1agged as disturbed, and multiplies that area by the user-specified rule-of-thumb value.

80

Graphs Click the hydrograph buttan. Turn off the combined hydrograph optiol1 ro view only the rhree individual hydrographs. The hydrograph shows a peak discharge of 8.87 cfs.

Contributing SW¡¡ Hy<Iroll~¡') ro, SUu<1uro • 1 ¡ _, ..... J""_~9 _t1ll.tf:'1~"f~~ ":!~~6~ftG:'1 . J

- -·-I·-·'-C""""'dSWSP •• ~ ff : : , ~ 90 el! " 1205 .... : : :¡ -.- . ,

1 5 --- - ····t - ·· ··,·--· : ; ·······~····· · · ·~- · --- - --~

- .... ,: :;)!

_:P!':': T-'~'::'~:': .. l: : ¡ : : . ~ l ' f .¡ ;

1 ' . : • ¡ __ D L' , _i ' a w ~ ~ ~ ~

T .... (ho'"

- ""', 1>' .. ,: " .!;NJ,,"

Window in around rhe 12th hour and be sure ta window slightly below the X-axis. As can be seen in me plor. peak f10w for SWSI is about 0.86 cfs and for SWS3 the peak f10w is about 1.21 cfs. Theselow peak f10ws direcdy rcAcer a curve numher of 49.

Now review [he sedimentgraph. As expected me vast majority of sediment is associared with me disturhed area.

Detailed subwatershed inputs and outputs can be viewed by c1icking on the Repon Tab 011 [he main screen, and selecting Struccuce 1 SWS(s). The peak sedirncm concenrrarion from SWS2 is abour 19,000 rng/l. This is reduced by comhining with the more dilute flows emanating from rhe pasture lands.

Silt Fence Design Parameters Click on the "SrfUcture Design" bunon [O enter rhe silt fence design screen.

Silt Fence Flow Rate The flow rare is obrained from rhe specific rnanufacrurer's technicalliterature. Usually two flow rares are listed - distilled water and slurry flow rare. The slurry flow rare is the appropriare one [O use in SEDeAD 4. The range of slurry f10w rates is berween 0.1 and about 15 gpm/sq ft. A rypical value is 0.3 gpm/sq ft, which is emered for this example,

Silt Fence Width Along the Contour The silt fence should be locared as close on rhe contouc as is reasonably possible. The widrh is nor rhe enrice lengrh of rhe fence, because tieback disrance wil1 be

-

-

calculated ánd/or overridden. The widrh is simply rhe lengrh of silt feoce installed along the conto"r. Enter 600 ft for Silt Fence Width.

Silt Fence Height Two silr fence heighrs are cornmonly used: 30 ¡Dehes and 36 ¡nches. Propee installation of a silt fence requires thar 6 ¡fiches be placed in a diteh and backfilled. Therefore, silt fence height refers to the height of fence above the grouod surface. Eoter 2.5 ft for this example feoce height.

Silt Fence Upgradient Land Slope

81

The silt fence algorirhm is based on backwater, [he flow rate, and sedimenta­rion algorithms [har dynamically account foc mixing and sercling of different size particles. The up-gradient land slope is used in conjuncrion with the silt feoce height and routiog of the ioflow hydrograph based 00 the slurry flow rateo The laod slope is "sed to derive the stage-storage relatiooship for ,he sil , feoce. Eoter 5% for ,his example. Note this is ,he same slope used for SWS3.

Silt Fence Tie-back Distance This is calcula'ed io SEDCAD 4 as a fuoctioo of the sil, feoce height aod ,he tlpgradienr I~ncl ¡¡Jope. The tie~back distance is determined by projecting a line [rom me tap of [he silt fence upgradient until ir intersecrs [he land surfaee, which is a fuoctioo of the land slope. For example, a 2.5 fr sil , feoce heigh, aod a laod slope of 5% yields a tie-back distaoce of 50 ft.

The ,ie-back distaoce ioforms the user about ,he leogth of silt feoce ,ha, should be iostalled upgradieor 'o avoid flow arouod ,he o"tside edges of the fenee as me water elevation rises to me total height of the silt fenee. The ovenide butron can be used to modify mis value. A message will appear that gives the allowable heigh, of water 00 ,he sil, feoce correspoodiog to ,he specified tie-back distaoce. That is, if the water is higher thao ,hat calcula,ed maximum height, some ruooff will flow around ,he edge of the sil, feoce.

Silt Fence Additional Weirs The use of a weir cut into a silt fenee has proven [Q be useful io Qur work. It fuoetions as an emergency spillway providing struetural relief to (he silt fence. Such weir(s) enable ,he siIr feoce 'o remaio fuoc,iooal eveo duriog large storm

eveots <ha' oormally would cause ,he feoce 'o structurally faiI. The weir is modeled as a sharp crested weir in SEDCAD 4. Rack is placed dowo-gradieo' of the weir to avoid seour (hat could undermine the sil( fenee.

When "additional weirs" is checked, the additional input needs are the number of weirs. weir depth. and weir width.

82 How Many Weirs?

Since che flow rate rhrough a weir is so great wirh respecr ro char of a silt fence, (he number of weies is flor a critical item. Placement every 100 to 300 fr seems to work out welJ at construccion sÍtes. Obviouslya weie willllot effecr [he performance of (he silr feoce until f]ow is ac[Ually discharged rhrough me weie. Even [han, sincc so much ofthe scorm volurne is derained behind me silr fcoce, a silt fence performs quite wel!. Eorce 1 foe me example.

Weir Depth

The depth of the weir is the disrance berween the rop of the silt fence and me

hottom of me \Veie. This rype cf weie is usually cut out using a knife and chen the remaining portian of (he fabeic artached to sorne 50rt of reinforcemenc such a 1 by 1, [har in turn Is auachcd ro [he siIt feoce stakes. Enrer 0.5 fr foe ,he example.

Sil, Fence Weir Wid,h

The weie width is usually determined by the spacing between silt feoce stakes. Depending on the which manufacturer is used and the installatÍon methad employed, spacing is nocmal1y between 6 and 10ft. Enter 8 ft foc chis example.

Silt Fence Design Results The sil, fence design screen immediately shows mat me peak Ilow was reduced from 8.87 lo 0.67 cfs. This is expec,ed because allllow was discharged through the silt fence. The heigh, of wa,er (peak srage) was 1.6 fr. To dewater, ir will take 0.75 days or abau[ 18 houes. Dewarering is calculated assuming only flow through the silr fence. Additional dewatering will occur as infiltra­tion.

The peak effluent sediment concentra,ion is abou, 2,200 mg/l. Thus the concentrarÍon was reduced ~,,~ ¡

• n..,RIft..,.",..,. ~ ,,··, .... ~~ ............. _------.. l from abollt 16,600 ro · 'WiJb .... ariWiI) l1Qi'ii ~ ~~ ClI.Jl' t

11 Th k 1Hi;N 1IJ ,~ I

2,200 mg. e pea ~ ...... "'" .. "", ....... "" I '~I .. " , serueable conceotration f. w ....... ,.i r-Jfti.i'r o.....m I'etJ:r ..... s.. r--u; l!l I

I p ....... _"w.o.~ ..... ~ r-r ~,_ was reduced from 11.0 to -:;¿:"IIj r---n ~ 1I_-.gn"'~ 1 ... ~. f O mili. That is, all .~ . ~;r~jd-~'~ -- t<;o~s.;; 1 lUOlI 1.1I5 f setcleable solids were ' -~..... ,," c.:.!=.1 10"'1 IUJJ i

l !¡ "~iI..I~ retained and only a !¡ " ~!t t ~I '; 511 aro ,

,l ~~~ , r.:-;- 1 portian ofthe fine soil ¡ ,.. . .-~t- l 'I',.uo.-.,tt). I!I1· · ~I

. 1 (", 1.1 ... ".."",

fraction was released 1.

through me sil, fence. The

overall sediment trap efficiency js 91.1 percent.

Graphs of inflow and outflow hydrographs and sedigraphs can be viewed by cIicking on the graph burtons, respectively.

-

. 1"""'

-

83

Silt Fence Design with Dedicated Sediment Storage There are many methods ro specify scdiment capacity. The user-defined methad wiII be illustrated for this example.

Selecr [he uscr-defined option, and (hen cnter .05 ae-fr. fu can be secn, dedicating 0.05 ae-fr te sediment storage ¡nereases (he sediment trap efficiency to 92.3% versus 91.1 %. Also me peak stage was increased ro 2.08 ft from 1.59 fr. The difference

in stage is due ro me sediment storage. The peak flow discharge was increased from 0.67 ro 1.48 cfs. Because of the higher peak discharge which occurred cacliee in (he event, dewatering lime was increased ro 0.89 days. The peak emuent concentracion

. -sir";;; • --- - . : ""-!tt¡.p.'lq): r-r¡; ¡ ~I07>,j:crt4lM J"iii]" . ,Hftojf" r--n

i.1r4sq,. ltJ j-"-!~

J .. ~~. ~.r lht<i6r , P'~<ffl "" ¡¡';:~~IT ~~. r-a:!' !oiHwaltl'* r-Tli

, _ _ 'ñ¡'-;"';'P:- ,.; ~,~ """1 • • ~C4o>oeI,' $toÍ c.-too;>Jl i l kll9.a~z_ • ~ i " r-~~Il : ... ~ lld.oW,t"";' ¡

¡ ,..,~-

¡ 1?'~~;~

decreased ftom 2,216 ro 1,968 mgll.

~~! -¡t " QUf i~

! .~~W.I, ! t~1 ..... ~~19 Ji i ,~""""' S>.¡o~ ~¡ !fe '1 lf ,~1"'~1 í"O'8i; ~-~- H , "

r-::-:::r-:-::;: r 1 ~!."t:t 1 IUIDI 1,S(8 H

~-=f1W~ ti i~~~~ 1 5.571 lOO Jj

. - U

!_~~t~, fltln _ . ___ 'MW _ 11

The SEDeAD 4 user needs to be aware that there is an inrerplay among many variables occurring in [he sedimentology algorirhms. The important variables are incremental stage-srorage. time depcndenr srage-discbarge. ¡ncrcasing or decreasing surface area of rhe silt fence wjrh various sc:enarios. changes in tbe distance betwceo various modeled sedimenr laycrs and rhe sedimenr storage elevation. i.e. panicle fall deptb. and temporal concentradon changes wirhin the 10 model sediment layers.

The interrelationship amoog these numerous remporalIy varying facrors primarily change rhe sediment trap efficiency and effiuent sediment concen­trarion. For instance, one would assume rhar as more volume is dedicared ro

sediment storage rhat rhe sediment trap efficiency would deerease. This is somerimes me case bur often times Dar so. For example. for the example

problem, if we dedicate 0.05, 0.10 and 0.15 ac-ft to sediment srorage, the trap

efficiency changes from the original 91.1 % to 92.3%, 91.7% and 89.7%,

respectively. What we see here is rhe ¡nrerplay amoog many paramerers.

84

Grass Filter Design A grass fllrer is designed to trap sedimenr mar enters by overland flow. SEDeAD 4 only mode1s [he effectiveness of a grass filter (har receives uniform overland flow. If concenrrared flow entecs the grass fiher sediment trap efficiency is greatly reduced. The concentrared flow situation is nor modeled in SEDeAD 4.

The grass filrer creares backwater. reducing the veJocity Df upgradient fIow resulring in deposition. Sedimenr laden overland flow transponed through [he grass filter is further trapped by impinging rhe grass blades. Infiltrated water within the grass filter also slighcly reduces rhe peak flow and runoff volume.

To achieve uniform overland flow, a flow spreader can be constructed. This is rather expensive and perhaps not reasonable fOI a temporary cooditian [har exis(s at a consrrucrion sire. The mos( cost effective method is to install a silt

fence upgradient of a grass filter.

The silr fence performs numerous funccions mat ¡ncrease the efficiency of a grass filter. Ir traps perhaps 80 to 95% of rhe entering sediment, reducing the impact of sediment deposition wirhin the grass filter. This reduces rhe needed lengrh of rhe grass lilter sinee the grass lilrer does not have to be designed to accommodare large quantities of sedimento It reduces the peak flow and discharges a very low flow rate uniformly rhrough the silt fenee to the grass filter. The silt fence can be viewed as a primary sediment control faciliry, whereas me grass filter can be considered as a secondary treatment faciliry working in conjunction with the silt fence. Refer ro me Silt Fence Grass Filter Dcsign Example. The gr.ss filter researeh was initiated by Tollner (1976) and advaneed by Hayes and others, 1979.

Grass Filter Design Example The Silt Fenee Design Example will be expanded by adding a grass filrer immediately downgradient of rhe silt fence. AH storm, particle size, structure networking, watershed parameters, warershed hydrology, and warershed sedimentology inpUts are dctailed in the Silt Fenee Example

The example grass filter is approximarely 70 ft in length, 600 ft wide and has an approximate slope of 4.5%. The grass ruter consists of fescue in good condition. The grass height varies from 3 to 6 inches. An average value of 4 will be used.

Networking -' A grass filter strueturc will be added to rhe silt fenee in rhe Silt Fenee Example. .....,

-'

85 If you creared rhe example file foc che silt fence example:

• open rhe silt fence cxample fil e

• click 00 me Design Tah

• c1ick on the Networking burton, meo Add a Structure

• Structure 2 will appear, and selecr a Grass Filrer

• Now che designadon of structure flowing ro anocher structure is nceded .

Highligh, ,he "To Srruerure No" for ,he sil, fenee (eurrently a "O") and ochange ir te "2"

If rou have Dor crcatcd aD examplc file foc the silt fence example and want ca run chis example, you will need ro creare the file with che parameters specified in ,he sil, fenee cxample

Grass Filter Design Inputs To design an effective grass filter, considerarion must he given ro achieving uniform and shallow overland flow ,hroughou, ,he grass fil'er. This can be most casilr achieved by combining a grass filter with aD up-gradient silr fence as is illusrrated in chis example. If rhe f]ow depth and associarcd velocicy cxeeeds a eri,ical velo<Íty. rhe grass blades will eollapse and ,he grass fil,er will funcrion likc a grass waterway. For chis condition me grass filter is assumed ro

fail and rhe trap efficiency is considered zero.

Several inputs are bascd on dctermining if this failure condician occurs. The cricieal velociry is a function of me type of grass, its condition, and the height af grass. The pulldown inpur rabies provide guidance for several grasses and growth condition. For a given grass o/pe and condition, yOil can obtain

• Roughness Coefficient

• Grass Hydraulie Spaeing

• Grass StifTness Factor

Omer input parameters are

• Grass Heighr

• Grass Fil,er Infilrration Ra,e (fune,ion of rhe soil Hydrologie Soil

Group)

• Grass Fil,er Lengrh. Wid,h. Slope

Grass Filter Roughness Coefficient

The roughness coefficienr is based on an a1gorithm of shallow f10w rhrough small ree,angular ehannels existing between blades of grass. Cliek on ,he drop

down list burron to view roughness coefficients for various grass rypes and condítions. The examplc problem statcment stated thar rhe filter consisrs of feseus .nd good eondition. Seleeting a good stand of feseue yields a roughncss

eoeffieienr of 0.0141.

86 Grass Hydraulic Spacing The hydraulic spacing is a function of [he grass species and condirion of growrh. Ir is used in determining [he hydraulics of flow rhrough [he filter. A value of 0.67 was auromatically entered when che grass rype and growrh conclítioo \Vece selected foc the Grass Filter Roughness Coefficíenr.

Grass Stiffness Factor Different grasses are more oc less resistam to bending over during flow. The sciffness factor is a [un crian of grass species and growrh condition. A value of 2 N-sq m is used foc a good stand of reseue.

Grass Height The grass heighr affecrs sediment stoeage capaciry within rhe grass filter and 1s used in derermining if a selected grass species wilI callapse as a function of me deprh of flow in eelation ro the geass height. Simply enter a grass height of 4 ¡n ches foc chis example.

Grass Filter Infiltration Rate Grass filters are ofren used to provide added proreerion of adjaeent srreams or nearby wedand areas. The soils adjaeent [O streams afien have higher iDfiltra~ rion rates [han upgradient soils. The sandy loam, foc this example. is in Hydrologic Soil Group A. The following table shows rough estimates for sready~state infilcrarion rates:

Soi' Group A B e D

I~filtration Rate > 0.30 in/hr

0.15 - 0.30 in/hr 0.05 - 0.15 in/hr o - 0.05 in/hr

Soi/ Group A: detp sand, detp 10m, aggregattd silts Soi/ Group B: shallow 10m and sandy loam Soi/ Gronp C- clay loalm, shallow sandy loams, soi/ umally high in clay Soi/ Group D: soil 01 high swellillg point, heavy p/astic clays

Enter 0.3 iph foe this example. This may be low foe f100d plain soils and may be increased depending especially on me existence of maeropores. A higher

infilrrarion rate will inerease the sediment trap efficiency.

Grass Filter Dimensions Grass Filtee Length

Length is a rather sensitive paramerer. Ir is especially critieal foc values less

rhan about 50 fr. As lengrh ineceases, sediment tcap effieiency ¡nereases and effiuent eoneentration deeceases. Enter 70 foc this example.

-

-

-

-

-

-

87 Grass Filter Width Por (his example, filtcr width corresponds wirh [he section of right-of-way being controlled by (he silt fcoce - grass filree combination. Filter widrh affecrs

the depth of flow, ,he,eby influencing velocity and ,he dep,h of flow. Enter 600 n. Grass Filler Stope From (he example schemaric, a slope of abour 4.5 % is measured. Slope influences velocity and deplh of flow.

Grass Filter Design Results Once the final entry (i.e. Grass Fil'e, Slope) is made and lhe 'ab key is pressed (oc shift-tab oc mause click), results appear. The inflow values emanating from the silt feoce are automatically passed and displayed 00 che screeo. These values are 1.48 cfs and 1,967 mgll peak sedimen' concentration. Settleable solids are zero since (he larger size sediment fraction was previously rerained by the Sill fence.

The trap effi­ciency of (he grass fIller a10ne is 93.5 pereeor. The silt feoce retained

92.3 % of lhe inflow scdiment load and [he grass filter retained

93.5 of ,he inflow from lhe Sill

6,'~W.;"Q·~· , ' rr.ieo~

fcoce. Thus the overall trap efficiency of the silt fence - grass filter sediment control syslem is 99.5%: Sill fence unlrapped sedimenl (1 - 0.923 = 0.077 [7.7%]) Grass filler untrapped sediment (1 - 0.935 = 0.065 [6.5%]) OveraU untrapped sedimenl (0.077 x 0.065 = 0.005 [0.5%]) Overall trap efficiency (1 - 0.005 = 0.995 [99.5%])

The peak discharge was allenualed to 1.19 cfs frOID 1.48 cfs. Peak emuenl concentracion was drascically reduced from 1,967 to 311 mg/l. This reduction was caused by fine size particles being retained within the grass filter and due to inft.ltrated waters.

88 Grass Filter Reports

Structure Surnrnary:

strucrure Summllry: Immedlale Ta' Puk Ta.

Cortributinl;! Cortributing Diuflirga ,~áf 5edimert

~~~ %~~ 'o>.rn. (ton) (á~)

(.011)

#1 In 4320 4.320 8.87 0.71 '.2

CUt 1.48 0.71 O., ., In 0.000 4.320 1.48 0.71 O., CUt 1.1'3 0.:33- 0.0

p,," Peak s.dimert ~ule .. ~e 24VW

(':,;íi ~i (mil)

l~.óOi! 10.97 5.57 1,9&8 0,00 0.00 1,9&7 0,00 O."

311 0.00 0.011

The conrriburing area irnmediately upgradient of each structure and [he total

contributing watershed acreage are listed. For (his example, no addirional up­gradient watersheds erisr between me silt fence and me grass fiIter. Peak discharge and total runoff volume are shown in the next columns. For me grass filece. runofFvolume decreased from 0.71 ac-ft to 0.31 ac-ft due ro the slow inflow cate and [he infiltration rate Df me grass filter. & (he inflow cate dcereases, Grass Filter Infiltration Rare, oc Grass Filter Length inecease, (he runoff volume deereases.

Tons oE sediment deerease due ro me retention of sediment by me silt fenee and rhen by .me grass filter. The peak sediment eoncenrrarion in mgll contin­ues 'o deerease from abou, 16,600 to 2,000 to 31 1 as runoff proeeeds from rhe warersheds out of the silr fence and through the grass filter. AH sertleable solids have been removed by the silt fence. Essentially [he combination silt fenee -grass filter removes almosr all of (he eroded sedimento Ir preves to be a very effeetive combination for rhis example.

Selecr "AH Strucrures" repon from the lisr. Derailed information about each structure is provided in these output rabies.

Silt Fence Reports: The silr fence inpurs are lis red as well as peak elevation, dewarering time and trap efficiency. Proeceding down ,he reporr, ,he S'age'Capaeity-Discharge Table provides the Fcnce Stage and Water 5tage and associated incremental area, capacity, diseharge and dewarering time. As can be seen, the water srage begins at 0.61 fr. Sediment srorage is provided bcnearh this stage. The arca and eapaeity a' ,he 0.61 ft leve/ are 0.17 ae and 0.05 ae-fr, respective/y.

Notice that the water stage value is reiniriated at 0.0 and thar diseharge is only allowed aboye the sediment stage. This is a slighrly conservative assumption that the dedicated sedimcnt storage volume is nor used foc srorage of runoff and therefore discharge is nor allowed below the sedimenr srorage elevarion. Note also rhar alrhough the discharge rate per unir fenee arca is eonstanr, the discharge rate sIighrly increases as elevarion is incrcased -From 0.61 to 2.0 fr due ro a proportionally grcater fcnee arca being conracted by (he water. The second pagc of the reporr shows the remaining $tage-Area-Discharge Table, followed by ,he Grass Fil,er inputs.

~

89

Grass Filter Reports: Grass filter results list che infiltrarian volume and rate, a peak flow deprh Df 0.054 io. me cri,ical prooe velociry ofO.8122 fps •• wedge loca,ioo ofO fr •• sedimeo, depm io zooe O of 0.0042 ioches and me ,rap efficieocy of me gr.ss filter. The very low flow depth .ccoun" for the overall efficiency of the filter. The prone velocity is a functlon of grass species, growth coodicion and grass height. If me actual velocity exceeds che prone velocity, [he grass is assumed lO

callapse and me trap efficiency is assumed zero. The wedge rcfees ro rhe location of me leading edge of deposired sediment thar forms a triangular edge as ir procceds clown gradient along che grass filtee 5lope. Since che vast majority of sedimcm was removed by [he silt fcoce, no significant wedge build up occured. Zone D sedimenr rcfees ro [he most down-gradieot section of che sediment depostion. A value ofO.0042 ¡Dches is insignificant.

90

Check Dam Design Porous rack check dams are used in channels to create backwater, rherefore reducing flow velocity resulting in deposition of sand-sized pardeles up­gradient of the check dam.

The algorithm for porous rack check dams is currently limited to trapezoidal channels. No credü is given foc a reduction in peak flow. The flow rate rhrough me check clam is simply a function of the effective cross-sectional area based on the porosiry of the check dam. This algorithm has only been verified based on limited data collected by USGS at oue highway construction site (Reed, 1978). A new algori thm is currently under development.

Check Dam Design Example Problem Sta,emen,:

,~

\ \ .... O.IIOOe

. "' a.Il4II

Porous Rack Check Dam Example

Storm Input

Mining exploration is being conducted in che Four Cornees area. The area disrurhed foc me dcill rig, associated equipment. and access is 0.24 ac. As shown in (he example figure, a porous rock check clam is ro be consrructed downstream of the exploration site. The design srorm 1s a 10 ye-24 he event and ,he Hydrologic Soil Group is C.

The design inforroation that needs ro be entered prior to the design of ,he porous rock check dam is ,he:

• • •

Storro Input

Partide Size Distribution

Networking

• Subwatershed Information

Information is needed for the storro type and rhe raillfall amount associared

wi,h the 10 yr-24 hr design storm for the Four Cornees area. From the Storm Type help screen, in can readily be seen ,ha, a NRCS Type 11 distribution is applicable. From the NOAA Atlas, ,he rainfall depth for the 10 yr-24 hr design storm is approximately 2.4 inches. fu always, me 49 pt Distribution 1s

recoromended.

-

-

91

Particle Size Distribution The Sedimentology oprion burron needs ro be selected prior ro entering aD

erodcd particle size disrcibution. Click [he Particle Size Disrciburion bunon, and then [he Creare New burron. Prior ro cnrering (he data, (he filen ame and ¡¡rst disttibution labe! will be ptompted fol'. Enter the following data:

Filename (example): Four Corners Label: Top,oil

Partide Size (mm) 4 2 1

0.5 0.25

0.125 0.062 0.031 0.016 0.008 0.004 0.002 0.001

Networking

Pet<:ent Finer (%) Topsoil

100 98 94 88 82 72 64 48 33 20

15.5 6

0.5

The nerworking foc mis example is quite simple since only a single sediment control struccuce is being analyzed. Click on [he Networking bunoo, (hen cliek the Add a Strueture burton, and seleet Cheek Dam. Sinee only the performance of Ofie structure is being asscssc:d, stcucturc # 1 automarically flows

ro the oudet (designared as zero) and no Muskingum routing between structures is nceded. Click OK.

Subwatershed Information Click on the Design hutton and rhen cliek on Add SWS hutton. The subwatershed area, time of concentrarion, Muskingum routing, NRCS curve numher, and unir hydrograph shape are input 00 (his screcn.

Two subwatersheds are specified foc this example. The up-gradient suhwatershcd (SWS 1) is the 0.24 ae exploratioD site, and [he down-gradient suhwatershed (SWS2) consisrs of desen shruh in fait eondition, i.e. 50 to 75%

aerial eoverage. The up-gradient suhwatershed is designed SWS l and Muskingum routing will he needed sinee SWS l's outlet is not at S 1, the porous roek cheek dam. No Muskingum routing is needed for SWS2 sinee [he outlet of SWS2 is at S l.

92 Subwatershed Hydrology and Sedimentology Inputs Enter the following numbers for 2 subwatersheds:

Area Te Ml1sk. K Musk.X eN UHS 1 0.24 0.018 0.012 0.334 91 Fas, 2 0.90 0.041 o o 81 Fas,

K ReR' Lengdl Ree. Sloee J;; r PSD Disrurbed 0.32 80.0 1.5 0.80 Topsoil No

2 0.32 250.0 3.5 0.36 Topsoil No

Notes:

• The area can be derermined from various merhods, software packages, oc with the SEDCAD - AuroCAD (SC-AC) interface.

• Time of Concentration SWSl: the longesr flow path i, esrimated to be 80 fr and me ground slope is given as 1.5%. Since (he area is disturbed, land use caregory 5 is appropriare. Overland flow is che ooly component of che time of concemrarion for SWS 1 since no channel flow is neecled. Time of concentration will generare a hyclrograph at me subwatershed Dudet

only - Muskingum rouring will route me generated hydrograph from me ourlet of SWS 1 ro SI. SWS2: the overland flow length and gradient are 250 fr and 2.8%, respecrively. Since a desert pavement is expecred, category 5 will result in a rachee fase overland flow velocity, representative of such a pave­ment ..

• Muskingum Routing Routing from the ourlet of SWS 1 ro SI is via a gulch wim a 1.3% slope and a lengrh of about 150 fr. Category 8 is selected.

• Curve Number SWS 1: oprional curve numbers can be viewed by a dick on che edit burron. Specif}> Hydrologic Soil Group C and select cultivated agricul­turallands and then select Fallow, resulting in a CN of 91. SWS2: select Arid and Semiarid Rangeland and wimin mis category select Desert Shrub ... in fair condition, resulting in a eN of 81.

o Unit Hydrograph Shape The unit hydrograph shape for both SWS 1 and SWS2 is fasr.

• K Factor The K facror (,oil erodibiliry) for both subwatersheds can be estimated by dicking on rhe edir burton and selecring loam, resulting in a K of 0.32.

• Representative Length and Slope SWS 1: representative lengm is 80 fr, representative slope is 1.5% SWS2: representative lengrh is 250 fr, representative slope is 3.5%. The 3.5% slope is me average of me 2.8 and 4.3 % slopes.

93 · e Factor

SWSl: c1ick me cdir bueron, selectTypical Values Reported in [he Literature and [hen selecr Bare Soil Loase ro 12 ¡nches, rough, yielding a C fae,or ofO.8 . SWS2: select Permanenc Pasrure, Rangland ... , selc<.:C 0% ground cover, and seleet Canopy of taJl weeds or shon brush (0.5 m tall) wíth 25% eanopyeovet. The C factor ís 0.36.

• P Factor Accept rhe P factor dcfault of l.

• PS Distribution Since chis is a srnall sire and has only ane soil texturc, simply seIecr [he only eroded pardele sizc disrcibution from [he dropdown (¡sr foc both SWS's.

Check Dam Design Inputs Two ¡nputs are required for [he porous rock check clam: check claro height and porosity. Three channel ¡npues are nceded: channel bed slope, Manning's n of me channel, and channel sideslopes.

For mis example assume mar rhe paraus rack check dam will be con­structed 3.5 tt hígh.

The porosíty of rock check dams ís expeeted tO be between 40% and 55%. Herrera (1989) determíned

~c:"H4t~tti r----E a-n ... I'...,.I;>~ l~ '~ -iioo

DlarrdaNS~J~ r'i:E ~"'..mt.n:.rm ~R~t<:li L~2.5D

porosities ranging ttom 44.2% to 46.9% for ~ inch to 1 inch diameter grave/.

Current rescarch with Appalachian mine spoil has found porosicy to be between 50% and 56% for spoil sizes between 2 and 8 inches. Enter 50% for porosity.

Channel input p.rameters are a channel bed slope of 1.3%, Manning's n of 0.040, and channel side slope of2.5: 1.

Porous Rock Check Dam Design Results

The Strucrure Summ.ty rabIe provides • summary of me performance of rhe

check dam. Peak ínflow is 1.24 cfs. Since no routing of the hydrograph is condueted for porous rock check dams, the peak outflow is a1so 1.24 cfs. This is a conservative assumption.

The overall sediment trap efficiency is 26.8% (from [he structure design derails rabie). The trap efficiency of a porous rock clam is anricipatcd ro be less than

j

94 30%. Ooly [he sand fraction is expected ro be trapped. Settleable solids were reduced from about 14.3 to 9.3 milI and total solids redueed from about 24,000 to 17,000 mg/!.

Channel Design Four types of ehannels may be modeled in SEDCAD 4:

• Nonerodible Channel • Erodible Channel • Vegetated Channel • Ripeap Channel

ChannelShape AH foue channels modeled by SED CAD 4 can be designed for a trapezoidal and a triangular shape. Add..itionally. nonerodible, erodible. and vegcrated ehannels can be designed with a paeabolie shape. Finally, nonerodible channels can accornmodate rectangular, circular and semi~circular shapes.

Freeboard Freeboard is added ro rhe channel design deprh as a safeguard against overflow­ing the channe!.

Freeboard IS nccessary foc numerous rcasaos. To predict the peak flow. several assumptions and judgments are made concerning me design s[Orm. storm disrribution, hydrograph shape, land use, soiI tex[Ure, and factoes affecting rhe time of concen.tcaüon. Also construction qualiry may vary. stream roughness may ehange due to seour or deposition of soil, growrh of vegetarian, fallen tree limbs, etc. Once Manning's roughness eoeffieient is ehanged, and especially if the initial design had a Froude Numbee neae 1.0, speeifie energy will ehange resulríng in patentially two alternaring flow depths foc a given diseharge. Designs in SEDCAD 4 assume straight ehannels so super-elevared flow (which oeeurs in ehannel bends and espeeially bends wüh a small radius of eurvature) is not caleulated but can vary the flow depth by ;> foot.

SED CAD 4 has three methods of aecouming for feeeboard :

• speciIY an additional drpth to be added to the design depth • speciIY a % o[ the design flow depth • speeify a multiplication factor times the velocity times deprh

If enteies are made foc two oe rheee of rhe methods, rhe maximum cesulring feeeboard depth is used.

-

-

95

Nonerodible Channel Design The methodology used ro salve foc flow depth is símply Mannillg's equation coupled with rhe continuity equation (Q= VA). This routine is applicable ro nonerodible materials such as concrete, asphalr, etc. This colirioe can also be used to evaluare commerciaJ products such as gabions, articulated concrete blocks, georextile filled wirh concrete, etc. To use mis routine foc cornmercial products, rhe suggested Manning's n listed in rhe rechnicalliterature provided by rhe manufacturer, is entered and the resultanr dcsign velociry is compared

ro rhe maximum permissible velocity provided in rhe manufacturer's rechoical lirerarure.

Nonerodible Channel Example The design discharge is generated based 00 des ign stoem and warershed characteristics. C hannel urilities are identieal ro those in the main design program exeept (hat the design flow is entered manually in utilities. Channel shape. slope. width, and side slopes are entered. Side slopes are horizontal to vertical. Channel materials and associated Manning's n are loeated through the TabJe Input button. or may be emered.

As an examplc. consider a permanent concrete highway diversion [hat is trapezoidal in shape. constructed 00 a 1.8% slope, and has a botrom width of 2 ft wirh 2:1 side sJopes. The design diseharge to be evaluatcd is 45 efs and a 0.5 ft freeboard is used. Emer the values in the Channe! Utility seetion.

The design veloei,y is 10.06 fps at a flow dcpth of 1.08 ft and rhe ehanne! eonstruetion depth (also aeeommodating freeboard) is 1.58 ft.

t'"--.---- ~

~ ~~Ic:l=t~

. ~IT~ .. B Sq,., l;'l L_~,, !:.~

8:lIItoDvr~flt r----roo, S~R!IIiI ·L ~ J'f¡Yi

~¡,¡-W, j~ } Tbi

~"' I _. o.ms ~ ¡#~

< '-11: r-:;;oI0moh: r-;J.V.D _.~_._--~-_._-=, -

. --- ---*-0es'll'lP.-. .... ¡

1 .... o~...t...d .... ~ 00d/I#l1

, l op ..... dII""

} *Sw~= { ~ucntd~ , f1ruóo~

'.00 ,. '" ,. .... '" OE& " 2.11 :

96

Erodible Channel Design The design rncthodology used in SEDeAD 4 is based on che limited permis­sible velocity method, which has been widely used since ¡ts introduction over 70 years ago (Fortier and Scobey, 1926).

Permissible velociry is a funcrion of che type of channel 50i1. If rhe actual design vdocity is less rhan [he permissible velocit}', che channel is :srable, ¡.e. non-erodible as designed.

A distincr advantage ro the permissible velocity mechod is thar borh dear and sedimenr ¡aden water can be modeled. CIear water is more erosive rhan sedimenr laden water since ir has a greater capacity ro transpon sedimento

The sediment laden a1gotithm should be used for channe!s that convey runoff from disturbed areas ro a sediment trap Of a sedimenr basin. Bare earthen channels receiving large quantities of sediment froro steep or highly erodible lands may not erode at al! and may be subjected to deposition. Channe! soi! type and channel slope are rhe mosr sensítive paramerers.

Erodible Channel Example Channel urilities from the maio screen will be used to ilIustrare an erodible chaonel designo

Assume thar a remporary perimeter erodible channcl is ro be designed foc a mining operarion in rhe Appalachian mounrains. The channel is ro convey runoff from a disrurbed site to a sedimenr basin. The peak flow, generared for rhe design storm and warershed charactt:ciscics, is 15.5 cfs. The channel slope is 0.8% and ir is consrrucred from spoil consisring predominanrIy of shale and sorne sandstone. The channe! is to be construcred using a D-7 dozer resulring in a bottom with of 12 ft and 2:1 side slopes. WiII this eh.nne! be stable as dcsigned?

1J.o~,ow>.t<# ~

SNw jr,.,.- ::J Sl»tr;t ¡--¡rni

WJan. .... .o«i<lIIJ j"ilOO

s.;;.,q",F!.".,·L TTcii ,11!W1 ·It rroo cl (H,'Wt

"-':J,~B ... ""'~· , M,. ............ [ .. 0.025 .---4. J,;j

.......,~¡t.<I f""'61ii" ---.J

A5 in [he nonerodible channel example, discharge, channel shape, slope, bottom width and sideslopes are entered.

.....;

ro'

ro'

r

r

97 To select the channel material and corresponding Manning's n and permissible ve1o.city, click on me Table Input button. The Limited Veloeity Sereen displays available options.

Jq..,:w-.,jL~I;

At che bottom cf thar screen, click on me Sediment-laden optian bunan and then click on "Shales and Hardpans to

~ o v r ' liI><l :

highlight and selecr rhar material. Note [har the permissihle velocity is 6 fps since this is nor an casilr eeoded material, especially when che channel is transporting significant quantities cf sedimento Note [har sands and silts are much more erodible, and therefore channels constructed from these materials are much more difficulr ro stabilizc.

Add a &eeboard of 1 n, since ir is assumed mar construction will he done withour a great dcal of surveying and the channel is expected to potentially deposit incoming sediment since the design velociry is only 2.85 fps.

The final design shows a design velocity of 2.85 fps and a construetion depth r of 1.42 ft.

r r

98

Vegetated Channel Design Vegetatcd (Ol" grass) waterways are often used ro convey hígher flows and at higher velocities [han can be accornmodated by erodible channe1s. Vegetarían inherently stabilizes [he channel soil by binding [he soil with plant foots and, foc taller grasses. bending ayer under higher flows affords additional protcctíon by rhe blanker of grass.

Vegetative channels generally onIy convey intermittent flows such as storm runoff and are llor designed to convey sustained base flow. If base flow exisrs and a grassed lined channel is desired, then a composite channel wirh a low flow channel consisting of rack, ar equivalenr material, would be appropriate.

The design cf vegctared channels is accomplished undee [W"D conclítioos, shorr grass and long grass. Shorr grass is used for Vegerared Channel Stabiliry Analysis and long grass is used for Vegerared Channel Capaciry Analysis. A Retardance Class is selccted for both stabiliry and capaciry anaIysis.

Retardance Class Experimenral work eonducted by Ree, 1949, and widely used by rhe NRCS (SeS, 1947), shows therelationship between flow resistance and the combina­tion of velociry and hydraulic radius.

!,---r-~rrrn~---r-r-rTTnTr--.

~

., A

"Jgclt~. 1 H~a~!ic Rndiu.

Consider the e retacdanee class. As dischacge is inereased from a low to a slighrly higher value, rhe Velociry x Hydraulic Radius rerm will inerease. As VR ¡neceases flow cesistance (as repcesented by Manning's n) deereases.

Assume the rerardance class ofD is selecred foc short grass condirions and rhar a B retardance class is appropriate for tall grass eonditions. fu:. discharge increases fram a relatively law value 10 a relatively high value VR increases for both retardanee classes, the roughness eoefficient decreases.

r

r

r

99

Vegetated Channel Stability Analysis Under shorr grass conditions, rhe channel is more prone ro being eroded [han during taH grass condirions. Thus, channel stability must be checked during short grass cooditiolls. During Jow discharge, thefe is significanr resistance ro flcw by the shon grass beca use ir is essentialIy very shallow flow. As discharge inereases and ,he flow depth signifieantly exeeeds ,he heigh, of the short grasses, tIcw resistance dcereases. Retardance Class of e through E (and especialIy D and E) are used foc stability analysis of vegeta red channels.

Vegetated Channel Capacity Analysis The situa,ion for 'all grass is exaedy opposi'e from ,ha, of short grass. Tall grass affords a great deal of protection ro me channel soil by laying over during high flows. Resistance during low Aew foc tall grass is high, foc medium flow resistance is srill quite high. and fIow resistance does llOr dcerease umil rhe raH grass bends over and lays on the chaooel bonom. Because rhere is more resistaoce from the taH grass thao from rhe short grass, the depth of flow fOf ,a11 grass is mueh higher ,han the dep,h of flow for short grass. Retardanee Class A through C (espeeially A and B) are used for capaeity analysis. Tall grass is used ro determine the construction depth of a vegetated chaond.

Vegetated Channel Example Chaonel urilities will be used to illustrate the design of a vegetated chaonel. A grassed waterway is ro be used for a permanent channel for a subdivision. Based on srorm, watershed, and alternative development scenarios the highesr design peak flow is expected to be 10 cfs. Due ro right-of-way limitations, the botrom width cannot exceed 8 ft and for mowing the side slopes need ro be

3: l. The chanoel slope is 2 percent and a grass mixture with retardance D for short grass and B for tall grass are ro be used. These inputs are the most cornrnonly used io designs. A 0.5 fr freeboard is ro be used. The soil is a silty day loam and is considered to be erosioo resistant.

This screen shows ioputs aod outputs for the shoet grass condition. As can be ,een rhe

design dep,h of flow is 0.52 n, velocity equals 2.01 fps and the roughness

~~' .. ~id~t j"i'[iij¡ sr.- ¡r;;;:;W ,3

sq.,.,¡t:¡: r--TciL" 2~W'dl-.m f " " ioo ~ ~~.l ffoo:'j ;HYi 5t:-:. @"3

'fT::r:@f,::IFf;v/ -~_fiB t"3W&Y.~t~~!..~l!~" ,~: , ' I" , .~I

t_<Jy~~t 1_,,, ,~~ ,....;...s }-¡~ J' f~(!; """'~~, " .. ,~~~ ,,,

J rO:SO,1t r-;- ~oi[i~' r---' , .. ViO ~ .. -,o_, - o~ "' ~, _ --_~ - _,_, ~ ,~ __ ".

100 coefficient (represenced by Manning's n) is 0,061. Let's contrast this wirh long grass conditions:

Now me flow depth is grearer, 0.96 ft versus 0.52 ft. The veloctty is lawer, 1.05 fPs versus 2.01 fPs. and rhe roughness coefficienr is higher.0.181 versus 0.061.

SIt.¡po. ,,~ :o:J ~~11ii

JIJ.2J All Df (his makes scnsc. Far [he taller grass, mere is more resistance ro flow as shown by a higher roughness coefficient, rhereby yielding a higher depth of flow and a lawee velociry. The consrruction depth is always raken from che capaciry analysis (I.46 ft for rhis example). which is rhe design depth ofO.96 plus a fteeboard of 0.5 fr.

-

r

101

Rock Riprap Channel Design There are aver a dazen procedures to determine rhe stability of a rack riprap ehannel. SED CAD 4 ptovides me uset with rwo oprions, Simons/OSM (Simons, et. al. , 1982) and PADER (Pennsylvania Oepanmenr ofEnviton­mental Resoutees, Stovet, 1990). The Simons/OSM Rock Riptap Channel Design methad uses two differenc algorirhms depending upon the Froude numbet of rhe initial design being less man Ot gtearet than 0.8. The PAOER Rack Riprap Channel Design procedure is aD iterative solution of Manning's and me cominuiry equations. with Manning's n being a function of the depth of flow and [he rack ciprap D50 size. Compadng these two merhods ro Slx orher rock ciprap design procedures shows [he Simons/OSM merhodology is mase conservative resulting in [he largesr D50 foc given design parameters.

Por borh design merhods, a mixture of several rock sizes is nceded to fil1 (he voids between [he larger rock parricles. A fileee bed stone should be slzed or alternatively, a geotextile should be selected based on th~ underlying SOll, rock ciprap size and the equivalent opening size of (he geotextile. Also, in general a 2: 1 side slope should be used for a trapezoidal rock riprap channel te obtaio an economical designo The design procedures are for rock ciprap and if othec lighter materials with a lower specific gravity are used, other design procedures should be employed.

Simons/OSM Method The solurion procedute is ro firsr solve for a mild slope and check if the Froude number is less than 0.8 . If this is true (he rock riprap design soludon is valid. If me Froude number is equal to or greatec than 0.8, the routine is tcansferred 10 rhe sreep slope memodology.

A mild slope should be viewed in a hydraulic perspecrive, meaning mar rhe Froude Dumbet is less man 1, i.e. subctirical Aow. The Simons/OSM method is more conservative than this because a mild slope is considered only foc a Froude numbet less rhan 0.8.

The mild slope merhodology is based on a procedute adopred by rhe Denvet Urban Drainage and Flood Control District as described in Sirnons. et. al. , 1982. 050 is a funcoon of rhe channel side slope, velocity and hydraulic radius.

lf rhe Froude numbet deretmined by rhe mild slope memodology is equal 10 ot

greater than 0.8 rhan the steep slope procedute is used. The ,teep slope algotirhm is based on me telationship developed by Bathutst, 1979 as reponed by Simons, el. al., 1982. Fot steep slopes, Bathurst based his developed relationships on flume studies that mimic natural mountaín streams, such mat the flow depth was about me same size as the rocks. Water \Vas nonuniform . cascading around the rocks rather than f10wing over them.

102 The design procedure can be considered cOllservative. Fifreen feer per second is considered me maximum srable velociry without having ro consider rack durability at higher flows. Ir should be nared rhar fOI rhe SimonslOSM steep slope methad, no darabase exises fOI a channel gradient less rhan 5%. There­fore foc channels wirh a Froude numher grcarer man 0.8 (steep slope method­ology) and wirh slopes less rhan 5%, a conservative approach is rakcn by lisiog a slope of 5%.

Riprap Channel Example - Simons/OSM A channe! is being designed foc a ski resart rhar is under construcrion in Colorado. For rhe 25 }'car-24 hau r design storm and rhe contriburing watersheds rhe peak Aow was detcrmined to be 73.2 cfs. A rock áprap channd

is proposed rhar is trapezoidal in shape with a 14 ft wide base, 2:1 side slopes. The channel slope is 8 percent.

The channe! utiliry ' screen shows rhar [he

050 is 6 inches for a stable channel design using [he sreep slope

algorirhm. The riprap thickness corresponds ro a Omax of7.5 inches

and the smallest rack in rhe mixture is 2 ¡nches.

PADER Method The PADER merhad is based on an iterative salurion ro me Manning's and

continuiry equarions, wirh Manning's n being a funcrion ofboth deprh of flow

and 050 of the rack riprap. For a given D50 riprap size, as the flow depth increases Manning's n decreases. The rate of decrease in Manning's n is highesr for flaws berween 0.5 and 1.5 ft and foc [he largec rack riprap sizes.

103 The PADER merhad wiIl select a D50 riprap size foc incremental velocities ro correspond ro standard rack ciprap sizes rhat can be purchased. The permis­sible velocities and corresponding D50s are:

D50 (in) Mu. Velocirv (fu')

0.75 2.5 1.5 4.5 3.0 6.5 6.0 9.0 9.0 11.5 12.0 13.0 15.0 14 .5

The maximum a1lowable velocity is 14.5 fps. The maximum DIOO .nd corresponding rack ciprap thickness has been modified from rhe values lisred in Stover, 1990, ro correspond with those derermined in rhe SimonslOSM mild slope method.

Riprap Channel Example - PADER A channel is being designed for a ski teson rhar is under construction in Colorado. Por [he 25 year-24 hour desigo srorffi and me contrihuting warersheds the peak flow was determined ro be 73.2 cfs. A rack ciprap channel is proposed [har is trapezoidal in shape wim a 14 ft wide base, 2: 1 side slopes. The channel slope is 8 petcent.

The results show a D50 of 6 inches with a maximum riprap size of 9 iD ches, which a1so corresponds to the thickness of the rack riptap. The design velocity is only 6.57 fp' and the depth of flow is 0.72 fr. Manning's n fot these condition5 15 0.048. The flow i5 5upercritical sincc [he Froude number is greater than l.

r-~~'~" ~'.~'"~'"~~-----=--~-= fliprep ChaM~

104

Culvert Design The needed culvert cliameter is derermined foc che design flow, which is calcularcd from contributing up-gradient subwatershed(s), headwater, tailwater, and pipe design characreristics of slope, length, Manning's n, and ao entran ce 1055 coefficienr.

Culvert dcsign equarions are based on [he eight possible flow regimes as illustrared in Culvert/Straight Pipe Flow Regimes. These flow regimes ¡n elude all possible combinations of submerged and non-submerged ¡oler and oudet flow conditions foc circular pipes. The algorithm enables calcularian of transirions between flow regimes.

The Culven Design Example i1Iustrates watershed inputs, culvert design pararneters and reports. The culvert design llor only provides rhe required

culverr size, bU( complete performance curves are created for the required pipe size and for one pipe size larger and srnaller.

CulvertlStraight Pipe Flow Regimes Unsubmergad Inlet Submergea IFlIet

Type 1 (auuctcor.((o~

" HW d~~'1iJ.~ - _._--... "~"

T)1l!l2 (Outlet ControQ lYPe a (Ou'Jet Control)

HW Z e~¡i~).~~

-'" ~ ; ;; AO=w;¡¡;;¿

Type 3 {Jnfet ConiroQ Typa 7 (0utItt Con\IcQ

Type4 (1nIct Con!roI)

(-

,-

-

105

Culvert Design Example Culverts may be designed in either rhe culverr utility oc in rhe main design section of SEDeAD 4. The difference between the (wo is simply thar in [he utility, the design discharge is enrered by the usee, and in [he maio program, the design discharge is calculated from rhe design stoem and up-gradient watershed characreristics.

To design a culvert foc a watershed start with storm input parameters, then click on che network butron, add a structure, select a culvert and proceed by clicking Oil the design burtan.

For example: Thc storrn inputs are entered as a 49-point fitType 11 distribution and a 10-year 24-hour storm of 4.3 ¡nches. Watershed characteristics are a 60 ac pasture

site in fair condition, hydrologic soil gtOUp e and a Medium unit hydrograph shape because ir is pasture land. The time of concentrarion for this warershed is represen red by an overland flow condition of pasrure grass (3) with a slope length of 400 n being conveyed 'o ,he culvert by a small stream (f1ow condi­tion 8) at a ,Iope of 1.5 % and a length of 1600 n. As seen in the

subwatershed ~H¡¡¡i!i¡¡¡Ji¡¡+!i!' :' 'iiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii\ design screen, the resulting time of concentrarían is 0.218 hours. A curve number of 79 with

Hydrograph Response Shape of Mediurn is applicable.

Culvert Design

'~~I ~ -;,ffj;1 ¡

.. c • •.• ,,:; •• :;._._ .. = . ..-.= ¡'~~ ';~ :~;:l í

To proceed in designing rhe culverr, click an the Srrucrure Design Butron. The culvert design screen will appear with a peak flow of 89.69 cfs. Enter a length of 60 ft and a pipe slope of 1 percent. At Manning's n, c1ick on the adjaccn, edit burtan ro view and select a Manning's n for a specified pipe. Select "corrugated metal, spiral", and the Manning's n ofO.015 is highlighted, displayed, and en tered.

Headwater is measured from the borrom of the inle! of the pipe (invert).

Headwarer may be restricted by rhe road elevarion, backwater onto an adjacenr properryor perhaps safery considerarions. A good rule-of-rhumb is to have ar leasr two feet of soil above rhe culverr ro prorecr it from being crushed. For roads thar may experience traffie containing heavy loads, rhis rhickness should be increased.

106

¡-"'" I

Cu lverl

1-- " --ler' gth-----J

Nomenclcture '

Afree gaining sorne experience with SEDeAD 4, rhe user wiIl have rhe abiliry ro estimare rhe size Df culverr associared with a givcn design peak flow. Based 011 chis, headwater should be 2 fe grearer rhan rhe estimared cu¡vert diamerer. For example, a culvert to convey 90 cfs wiII be between 42 and 54 inches. So unless orher circumstances override chis choice, headwarer should be firsr

approximated by 4 ft (for the pipe) plus 2 ft added, resulting in 6 ft. Enter 6 fr foc rhe maximum headw3rer in rbis example.

Tailwarer is measured 3t rhe pipe exir from rhe bonoID of rhe pipe. Tailw3rer conditions cornmonly accur if backwarer is created in a stream which is relarively Bar oc when a d¡(eh runs adjacem ro rhe road and conveys runoff. Tailwarer can be calculated by using one of me four channel structures available in SEDCADA. Assume zero tailwater for this example.

The eotrance loss coefficient reRects how easily flow transirions ioto rhe culverr. The mosr cornmon situarion is a culverr [har protrudes from [he road. The entrance 1055 coefficienr is 0.9 . Click on rhe edir burron adjacenr ro rhe entrance 1055 coefficienr ro view and sclecr an entrance 1055 coefficient. Click on "CMP projected from fill, no headwall".

Norice a 45 ineh diamerer culverr is required. This is based on zero cailwater and an eotrance 10ss eoefficienr ofO.9, which are rhe defaulr values.

Click on the Graph Performanee Curves bunon. The graph shows the

complete headwater - discharge relationship for the specified pipe and for one pipe size larger and smaller. This is very useful since rou can readily see if raising rhe headwarer wilI downsize che culverr ro me nexr smaHer pipe. rhereby saving moner.

From me performance curve graph, it can be seen mar me 42 ¡nch culverr

performance curve is just below [he interseccion of me design discharge -headwater lines. Thus a slighr ¡nerease in headwatcr will reduce me culverr

size. Change rhe head water from 6 fe ro 6.5 fr. The minimum culverr size is reduced ro 42 ¡nches.

-

-

-

107

CulYert Performance CU~!S'v~"Structure , 1 ¡

'" "" , '00 ~

¡; '" ,

~ ro

'" 20

Hudwaro,(tI)

Tú view outputs fo! rhis simple culverr design, click on the Report Tab and refer to rhe S[fucture Surnmary, Structure #1 Details, and Structure #1 SWS's rabies.

108

Plunge Pool Design A pi unge pool is uscd ro dissipare [he energy of water being discharged fram a pipe. Ir is usually used in conjunction wirh a culvert or a principal spil1way conveying water fram a pondo The advantage of a pI unge pool compared tú a rock ciprap apron is [har [he stored water dissipates energy rhereby reducing

the size of the plunge pool.

To design a plunge pool energy dissiparcr. informarion 1S needed abour [he culvert/pipe discharge, elevarion difference between [he pipe invert and [he water leve! in che plunge pool, depth of water flowing over [he outIet weir and elevation of [he outlet weir. The kcy design parameters are th"e size of the rock riprap plaeed in the pI unge pool and the e1evation differenee between the pipe outIet and the water leve! in che plunge pool. Both are sensirive design paramerers.

Safety is a concern in rhe design of plunge pools, especially in areas where ehildren may be presento The design depth of water in a pI unge pool should nor exceed abour 2.5 fr. Forrunarely, such a design also tends ro minimize cost.

Cost tradeoff: For a small rack riprap size, money is saved beca use the rhickness of rack 1S relarively smalI but rhe quantiry of rack is increased due ro rhe larger length, widrh and deprh of rhe plunge pool. In contrasr, for a larger rock riprap size, the thickness of rack is increased bur rhe quantity of rock may decrease since

the length, width and especially depth of the pI unge pool are deereased. The majar cost item is [he quantity of rock required. The Plunge Pool Design Example ¡Ilustrares inpurs and design rradeoffs. A rradeoff exisrs among rock riprap size, thickness of rhe rock layer, and rhe lengrh, width, and deprh of rhe

plunge pool.

Plunge Pool Design Example ut .. bo;o.o"

~ ..... ..... -Since plunge pools are

designed in conjuncrion with a diseharging pipe, the Culvert

PLUNGE POOl. EXAAlP!.E

Design Examplc will be modified for this example. and watershed inpurs are used in borh examples.

The same design starm

In the Networking sereen, entet 2 muetutes: a eulvert and a plunge pool. If yOil are using the same file as used in the culvert design example. the culvert wilI already be lisred as Structure l. Add a plunge pool as the second structure. Structure 1 (the eulvert) flows ro Strueture 2 (the plunge pool), and Strueture 2 flows ro the outlet (zero).

-

-

109 Now click on [he Design burroo . The culven subw3rcrshed informarion wilJ already be listed, assuming you are using [he culvert design cxample. If nor, pIcase review the culvert design cxample foc subwatershed ¡nfarmarion enrering the culven. .

Cliek ,he pJunge pool to highligh, tha' strue'ure. Nex' cJiek on ,he Strue,ure Design burroo, since no additional watershed exisrs.

OC~'9'1Fte .. rlI~

.AIS~;a¡.~ P<dWl#<~~

Ptd~lIoln>d~", 1 ____ ~SJ

PMbI ... t • .,dJ6!ft ~ p¡,.,W .. CemrdPd~ ¡---n¡ V.I~."""ClA!<f ll!><¡: r=i11 I

'~dJ_=;;~J

-¡

The pipe diameter from [he culvert design example is 45 inches and the pipe slope is 1 %. The 'pipe oudet elevarion is caken at the outlet of [he pipe and is assumed to be 860 ft for ,his example. The railwarer e1evation pool is assumed to be 1 ft below [he pipe outler, at 859 ft (i.e. A 1 ft cantilever exists).

The height the water flowing over [he outlet ccest is a fnnecion of [he design diseharge (89.69 efs for ,his example) and ,he sclec'ed wid,h of ,he exi, weir roc [he plunge pool. To determine [he stage-discharge relarionship foc a broad crcsted weie, go ro [he pond . utiliry .

• Enter ,he pond utility from ,he main sereen. Cliek ,he capacity bunon, which wiIl allow calculadon of [he stage-discharge relationship from O ro 4 ft a' 0.05 ft inerements. Proeeed by clieking on ,he Oiseharge bunoll, add a broad erested weir for ,he spíllway. En,er 0.01 for ,he spillway elevation . Now, the stage-discharge relationship foc various weie widrhs can be quickly evaluared. Por example, entee a 10 f[ weir width. As can be seen on ,he Oiseharge Sereen, 89.69 efs oeeurs a, abou' 2.05 ft. Henee ,his diseharge will 1I0w over a 10 f, outle' weir of the plunge pool at 2.05 ft aboye the outlet CTest elevation. The outlet ctest elevation, [oc this example, is 859 ft millOS 2.05 ft or 856.95.

Evaluate a rack riprap 050 size of 0.75 ft. The plunge poolleng,h, wídth and depth are 25.12, 23.54 and 5.93 f" respeetivcly.

The pJunge pool shape is generally tha, of an ellipse. It is suggested ,ha, once the design dimensions are calculated tha' an approximately rectangular shape

be pravided with the minimum length and depth, rhus facilitating eonstruc­tion. NRCS recornmends [har rhe excavated side slopes of rhe plunge pool be adjusted to acceptable grades [oc layout and riprap placement. For example, if a 2: 1 slope is used ,he plunge pool will basically reaeh a very narrow base.

110 Selccting a larger 050 rack riprap size (for example 1 fr)will decrease (he plunge poollengrh, widrh and deprh te 11.16, 8.85 and 2.23 fr , respecrively. This may be a beucr des ign o

Review reports enrirled Generalln formarion, $rfUcrure Summary. AH

Scrucrurc(s), and AH $r[ucrure $W$(s). The General Informaríon repon displays design storm informadon and a graphical display of ncrworking between structures.

Nore rhar rhe exir velocir)' is simply based on Q=VA (assuming full pipe Aow). This is (he case for many des ign situations. Por culverts on sreep slopes. [he culven may flow parrially full and the critical depth needs ro be calculated te

determine rhe actual cxit velocit), of rhe pipe.

-

-

--

111

RErORTS

The lisr at dl C left edge of rhe foldee shows rhe fo llowing available repons:

• Cover Page • General Infarmarion • Nenvorking • PS Disrriburion-Srructures • Strucrure Surnmary • Structure Details • Subwarershed Details • AH Reparts

A generated report may also be savcd ro a SEDeAD Repon fil e using che Save button Ibmc SaveRpr.BMP}. This will simply save the formatted report to a file ,ha, can be readily viewed (no, run) in ,he SEDCAD Report Viewer.

Generated reports are nor compatible with orher word processing packages. since [hefe is a coneero by sorne regulatory agencies that che user mar modify sorne ourpue values. However, yOil may peint out a saved repon at any time

using che Report Viewer.

To display a report. c1iek on rhe desired repor! on ,he list. The speed a' whieh the repon is generared is 90% atc!ibutable ro che printer driver used, ¡.c. a cop­af-rhe-tine heavy duty Jaser printer will be 3 to 4 rimes fas ter than a low-cost

desktop inkjer.

The printed filename and date is shown at the bottom of each page. Page numbers (beginning with 1) are displayed in the upper right-hand corner.

To navigate through the pages in a report, use the page navigation buttons at the bottom of the folder. To cnlarge or reduce the screen view, use the zoom buttons. To scroll a page, dther use the scroll bars at the bonom aod right edge of rhe view. or simply (Ieft) c1iek on rhe page and drago To print a reporto first verifjr ei,her rhe page range or a11 pages. rhen c1iek prinr.

Cover Page The title on the cover page is obtaincd from the Project Title field 00 the General Tab. Addi,ional eomments (from the Comments field) are a1so displayed. Other informatÍon, such as Designer and Company Information is shown if the fields are non-blank on rhe General Tab sereen.

General Informanon This contains the storm information and input eroded particle size distribution(s).

112 Networking The struc[ure nerworking is shown bm h in tabular form and in "graphic" fo rmo If rhe Rou ting Calculato r was used for Between Snucture Routing. rhen rhose details shoVl up in (his repon, as well.

PS Disuibution-Strucrures This repon will onl)' bt: avai lahlt: ir sedirncnrology is enabled. Thc combincd parricle size d isrciburion is shown em cring (and exiting) each structure.

Structure Surnmary

This shows a concise summary fo c rhe enrice runo Foe each structure, rhe immediarc conrriburing arca, (otal conrriburing arca, peak discharge and [O ral runoff valume is showll . If scdimentology is cnabled, rhe total sedimenr, peak sediment conccmrariol1 , peak se:: rrl eablc concentration, and 24hour volume

weighrcd average concenrrarion is a1so shown. The structures are listed in up· gradient ro down·gradienr order, Le. for any particular srructure, rhe conrribur­

ing srructure informarion will preceed ir in rhe rabIe.

Structure Details This repon is really a series of repons. Under (his caregory, (here is rhe oprion ro print/view all srructure details oc individual structure details. If yOil are imcrcsted only in a particular srrucrure and me file is large, it will be much faster if you view only rhe sr rucrure in quesrion.

Subwatershed Details This repon' is also 3 se ries uf reports. Under rhis caregory, rhere is rhe apria n ro prinr/view all subw3rershed dctails or anly individual strucrure subwarershed derails. Again , rhe repoer wiII be displayed faster if only (he strucrure ro be reviewed is selected. This repon also contains any routing paramerer derails from rhe subwatershed ouder ro the structure, rhar were used in rhe Routing Calcularor fOl" subwarersheds.

Al! Reports This wiII print all reporrs out in entirery. Depending on (he size of the fun

and rhe primer driver used, chis may cake a "long" time. We recommend thar once you have a job complered, rhat you print our AH Repom, then save the repoer ro a SED CAD Repon file ro be viewed at a latee time wirh [he:

SEDCAD Repon Viewer.

Report Viewer This is listed under the File Menu. This program simply displays and al!ows printing of a previously saved repon from rhe Main (Repon) secrion of SEDCAD 4. Ir differs from rhe Results Tab, in thar the numbers are not rerun and the resulrs are nor re-formarred, as in me Resu!rs Tab.

Navigarion through several pages is done by clicking on rhe page burtons at rhe

-

-.

-.

--

--

113 bottom of (he formo You mar al 50 enlarge or reduce rhe view with (he zoom bunons.

Tu serol!, you may either grab [he serol! bars at rhe borrom and right edge. or simply click and drag on the repon irself.

114 -' -..1

-..1

--......,

---'

--'-'

-'

-'

-'

'-'

-----'

-'

--...-

---'

'-'

---'

'-'

--'

...-

...--'

---'

-'

-'

-'

-

115

TROUBLESHOOTING

If you have trouble with SED CAD 4. please read through this section. We have teied to addrcss mose commonly asked quesrions here.

\Y/e have completed extensive testing ro disrribute an error-free program, however with any software program, (here mar be bugs encounrered. If you run joro a problem, we want to know abour ir! Please document any problem

as thoroughly as possible, and lisr events so rhat we can recreare it. This is a very imporrant step. Also, if a file is ¡nvolved, pIcase attach rhe file (.5c4 ex tension) to rhe message (a hard-copy of rhe file mar be primcd out through either rhe Windows Notepad or Wordpad applicarions). PIcase include your serial number (lisred in rhe AbOlir screen). If rOl! need ro caH us, picase refer [O me "Ho\'V ro comact us" screen for [he bes t person (O concac[.

If you are really stuck. then the best way to get help is to document the problem as [horoughly as possible and send an ernail [O:

PSchwab@compuserve.com

Also refer to me Navigation screen for informarion on Windows navigation basics.

Installation Questions f have installed !he program and rtstarud my computa. However, 1m getting Il "Semrity Kry Not Found" error, and tbe progmm won't star!. WhiZt sbould 1 do?

If, afrer you install the program, the computer does nor recognize (he hardware lock, ir is usually a network drive that has conflieted wirh rhe insrallation. To remedy. do the following:

• Remove the local maehine from me network by logging off «(his is temporary!).

• Select "Run" from the "Start" button. Type into the dialog box: C:\SEDCAD4\HWKEY\SETUP IQ4 and click OK.

• This should bring up the Sentinel Driver Setup Program window. Pull down rhe Functions menu, cliek on "InsmB Sentinel Driver".

• The program will dereet what operaring system you are running. Ir will

ask for the appropriate path. The path will be either:

C:\SEDCAD4\HWKEY\WIN_95 (Windows 95) Or C:\SEDCAD4\HWKEY\Wlfl_NT\l386 (Windows NT) (assuming C: is the hard drive letter. and SEDCAD4 is the subdirectory name)

116 • Click on OK ro load rhe driver. You should get a message indicating [he

driver \Vas installed and (har you should restarr your sysrem.

Printing Questions V?hen 1 click (}iI a teport, especially the ''Al! Reports" optiOll, the program seems to take II ver)' long time to displfl] the reporto Why?

Thc spced at which (he repon is generared is 90% attriburable to [he printcr driver uscd, i.c. a rop-of-rhe-line heavy dury laser primer will be 3 ro 4 times fas ter rhan a low-cosr deskrop inkjer.

-

117

ApPENDIX - MAPS

(f'om Rm ard, et. al., 1998)

""' Isoerodent (R Annual) Map of Eastern U.S.

!l8

Isoerodent (R Annual) Map of Western U.S.

-'

....¡

.....;

~

-.1

'-'

-------'

-'

--' ....¡

'-'

-'

-'

-'

-'

-'

-'

'-'

-'

-'

'-'

-'

-'

-'

-'

-'

-'

-'

-'

-'

-' -,

119

Isoerodent (R Annual) Map of California

-

--

---

-

120

Isoerodent (R Annual) Map of Oregon and Washington

-

--

-

-

121

REFERENCES

Brakensiek, P.L., \XI.j . Rawls and \XI. R. Hamon . 1977 . Application on an Infiltromerer Sysrcrn foc Describing Infilrrarion ineo Soils. American Sociecy of Agriculrural Engineers ~/inter Meeting, Papee No. 77-2553, ASAE Win rer Meeting, Chicago, IL

Brater, E.F. and H . W. King. 1976. Handbook of Hydraulics. McGraw-Hill , NY.

Chow, V. T. 1959. Open Channcl Hydraulics. McGraw-Hill, NY.

Chaw, V. T. (ed.) 1964 . I-Iandbook of Applied Hydrology. McGraw-Hill , NY.

Dissmeyer, G. E. and G. R. Fostcr. 198 1. Estimaring [he Cover-Management Faeme (C) in [he Universal So il Loss Equation [oc Foresr Conditions. Journal of Soil and \XIater Conservation 36(4):235-240.

Fortier, S. and F. S. Scobcy. 1926. Permiss ible Canal Velocities. Transacóons American Sociery of Civil Engineers 89:940-984.

Frederick, R. H. , V. A. Myers and E. P. Auciello. 1977 . Five-to-60 Minute Precipitarlon Frequency foc rhe Eastern and Central United States. National Oceanic and Armospheric Administrarion Technical Memorandum NWS I-IYDRO-35 , U.S. Depanment of Commerce, Washington, D. e.

Griffin, M. L.. B. j. Barfield, and R. e. Wamer. Model Studies ofme I-Iydraulic Efficiency of Sediment Ponds. Transactions American Sociery of Agricultural Engineers. 28(3):779-804. May-june, 1985.

Hayes,j. e. 1979. Evaluation ofDesign Procedures forVegetal Filtration of Sediment from Flowing Water. Unpubl. Ph.D. Dissertation, Agricultural Engineering Department. Univcrsity ofKentucky. Lexington, KY.

Hershfield, D. M. 1961. Rainfall Frequency Atlas ofthe United States. Technical Paper 40, U. S. Department of Commerce, Weather Bureau, Washington, D.e.

Hirschi, M. e. 1985. Modeling Soil Erosion with Emphasis on Steep Slopes and the Rilling Process. Unpublíshed Ph.D. Dissertauon, Agricultural Engineering Department. Universiry ofKentucky, Lexio'geoo. KY.

Hudson, R. G. 1944. Tile Engineers Manual. john Wiley & Sons, New York, NY.

Israelsen, C. E., C. G. Clyde, J. E. Fletcher, E. G. Israelsen, F. W. Haws, P. E. Parker, and E. E. Farmet. 1980. Erosion Control During Highway Construc­tion and Manual as PrincipIes and Practices. National Cooperative Highway Research Programo Report No. 221. Utah State University, Logan, UT.

122 Kuensder, W. 1998. Guidelines for [he Use of [he Revised Universal Soil Loss

Equation on lvfined LlI1ds, Consrruction Sires, and Rcclaimed Lands­Chaptcr 5 - e Factor: Cover lv1anagement. U.S. Depanment ofInrerior, Omee of SUffaee Mining, Offiee ofTechnology Transfer, Denver, CO.

Lane, E. W. 1955. Design of Stable Channels. Transactions American Society of Civil Engineers. 120: 1234-1260.

MeCool, D. K., L. e. Brown, G. R. Fo,,"r, C. K. Motehler, L. D. Meyer. 1987. Revised Slope Stcepncss Facror ror rhe Universal So11 Loss Equacion. Transac­tiol1s American Socicty oE Agricultural Engineers 30(5).

Melsaae, G. F., J. K. Mitchell, and M. e. Hirsehi. 1987. Slope Sreepness Effeer; on Soil Loss froID DisrllrbeJ Lands. Transactions American Socier)' uf Agricultural Engineers 30(4).

MerC!", L. D., e. B. JOhllSUll, ,!lId C. R. Foster. 1972. Stone and Woodehip lvlulches for Erosion Control on Construcrion Sites. Journal ofSoil and Water Conservation 27(6):264-269.

NOAA. Precipiration-frequt'llc)' AllaS of rhe \v/cstern U. S. NOAA Arias lI. Supo OfDocumems, U.S. Governmenr Printing Office, Washington, D.C.

NRCS (formerly SCS). 1947. Handbook of Channel Design for Soil and Water Conservation. SCS TP-61, NRCS, U.S. Department of Agrieulturc, Washing­ton, D.C.

NRCS (formerly SCS). 1951.Engineering Handbook, Hydraulies Seetion. U.S. Depanmenr of Agriculrure, Washington, D.C.

NRCS (formerly SCS). 1968. Hydraulics ofBroad-Crested Spillways. Technieal Release No. 39, Engineering Division, U.S. Department of Agricuhure, Washington, D.e.

NRCS (formerly SCS). 1969. Entranee Head Losses in Drop Inlet Spillways. Design Nme No. 8, Engineering Division, Design Branch, NRCS, U.S. Department of Agriculrurc, Washingron, D.C.

NRCS (formerly SCS). 1972. Hydrology Seetion 4, SCS National Engineering Handbook, U.S. Department of Agrieulture, Washington, D.e.

NRCS (formerly SCS). 1973. A Merhod for Estimating Volume and Rate of Runoff in Small Watersheds. SCS TP-149, U .S. Department of Agriculture, Washington, D.e.

NRCS (formerly SCS). 1975. Urban Hydrology for Small Watersheds. Technieal Release No. 55, NRCS, U.S. Departmcnt of Agriculture, Washington, D.e.

NRCS (formerly SCS). 1978. Water Management and Sediment Control in Urbanizing Areas. U.S. Department of Agriculture, Columbus, OH.

-

123 N RCS (formerll' SCS). 1986a. Urban H ydro!ogl' for Smal! Watersheds. Teehniea!

Release No. 55 , NRCS. U.S. Department of Agriculture, Washington, D .C.

N RCS (formerl l' SCS). 1986b. P!unge Pool Ana!l', is. Enginccring Departmen t Note No. 6, 2"' edition (2 10-VI-DN-6, 2'" ed.), U.S. Department of Agrieu!­ture, Washington, D.C.

N RCS (formerly SeS). 1988. Ponds Plan ning. Design, Construction. Agricul tural Handbook No. 590, U .S. Dcpartment uf Agriculturc. \Xlashingron, O.e.

O verton, D. E. aod E. e. Crosby. ! 979. Effws uf Con tou r Coa! Strip Mioiog 00

Stormwater Runoff and Quali ry. Repon ro U.S. D epariment ofEnergy. Dcpe. of Civil Engineering, Universit}' ofTenncsse<;:, Knoxville, TN.

Ree, \VI. O. 1949. Hydraulic Characreristics ofVegetarion foc Vegetated Waterways . . Agrieu!tura! Engineering 30 : I 84- I 87, 189 .

Reed, L. A. 1978. Effecriveness ofSedimen t~ColHro l Tcchniques Used During Highway Construction in Central Pennsylvan ia . U.5. Geologica1 Survey Water Supp!y Paper 20 54.

Renard. K. G ., G. R. Foster, G. A. Wee, ies, D. K. MeCool, and D . C. Yoder. 1997. Predicüng Soil Erosion by Water: A Guide to Conservation Planning with the Revised Universal SoiJ Loss Equation (RUSLE). U.S. Department of Agrieu!ture, Agrien!ture Handbook No. 703, Washington , D.e.

Rosgen, D. 1996. App!ied River Morpho!ogy. W i!dland Hydro!ogy Books, Pagosa Springs, CO.

Sehroeder, S. A. 1998. Guidelines for the Use of the Revised Universal Soil Loss Equation 00 Mined Lands, 'Construction Sites, and Redaimed Lands­Chapter 4 - LS Factor: HiIIs!ope, Length and Steepness. U.S. Department of Interior, Office ofSurface Mining, Office ofTechnologyTransfer. Denver, CO.

Sehwab, G. O., R. K. Frevert, K. K. Barnes, and T. W. Edminster. 1971. E!emen­tary Soil and Water Engineering. 2"' Edi tion. John Wi!ey & Sons, New Yo rk,

NY.

Sehwab, P. J. and R. e. Warner. 1989. Unpub!ished derivations.

Simons, D. 1982. Surface Mining Water Diversion Design Manua!. U.S. Depart­ment of Interior, Ofliee of Surfaee Mining, OSM/TR-8212.

Stover, M. 1990. Erosion and Sediment Pollurion Control Program Manua!.

Pennsylvaoia State Department ofEnviroomental Resourees, Bureau ofSoil

and Water conservatian, Division of Soil and Resources and Erosion Control, Harrisburg, PA.

Tollner, E. W" B. J. Barfield, e. T. Haan, and T. Y Kao. 1976. Suspended Sediment Filtration Capacity of Simulated Vegetation. Transactions American Soeiety of Agricultura! Engineers 19(4):678-682.

124 U. S. Departmenr ofCommerce, National Weather Buteau. 1963. Probable

Maxilllum Precipitarian and Rainfall-Frcqucncy Data fOI" Alasb. Technical Public,nion No. 47, Government Printing Office, Washington, D. C.

Warner, R. C. B. N. Wilson, B. J. Barfield, D. S. Logsdon, and P J. Nebgen. 1982. A Hydrolog)' aod Sedimentology Watershed Model. Part JI Users' Manual. Department of Agricultural Engineering Repon, University ofKentucky, Lexington, KY.

Warner, R. C,. M. C. Hirschi. 1983. Modeling Check Dam Trap Effiriency. American Socicry of Agricultural Engineers National Sumrner Conference, ASAE Paper No. 83-2082, Bozeman, MT.

Warner, R. C. and P. J. Schwab. 1989. Alternarive Designs ofSedirncnt Basins: Environmental and Economic Considerations. American So~iety of Agricul­tural Enginccrs Nacional Summer Conference, ASAE Papee No. 89-2020, Quebec, Callada.

\Ylarncr, R. C. 1992. Dcsign and Management of\Varcr alld Sedimcnr Conrrol Sysrcm!i, Chaprer 12.1. Sociery ofMining Engincers Mining Engineering Handbook, 2'" ed., SME, Litrleron, CO.

Warner, R. C. 1997. Mining Environmemal Handbook - Chapter 6.3.2.1: Sediment Control Sysrems. J. J. Marcus, ed., Imperial College Press, London, England.

Wendt, G. W. J 998. Guidelines for rhe Use of the Revised Universal Soil Loss Equation on Mined Lands, Construction Sices, and Reclaimed Lands­Chapter 6 - P Facwr: Support Practice. V.S. Department ofInterior, Office ofSurface Mining, Office ofTechnologyTransfer, Denver, CO.

Williams, J. R. 1975. Sedimenr Rouring for Agricultural Watersheds. Water Resources Bulletin 11(5):965-974.

Williams, J. R. 1976. Sedimenr Yield Prediction with Universal Equation Using Runoff Energy Factor. Present and Prospective Technology foc Predicting Sediment Yields and Soutces, ARS $-40, Agricultural Research Servire, U. S. Deparrment of Agriculture, Washington, D.e.

Wilson, B. N., B. J. Barfield, R. C. Warner, and 1. D. Moore. 1981. SEDIMOT 11: A Design Hydrology and Sedimentology Model for Surface Mine Land,. Proceedings 1981 Symposium on Surface Mine Hydrology, Sedimenrology, and Reclamarion, College ofEngineering, Vniversity ofKenrucky, Lexington,

KY.

Wilson, B. N., B. J. Barfield and 1. D. Moore. 1982. A Hydrology and Sedimen­rology Watershed Model. Part I Modeling Techniques. Department of Agricultural Engineering Repon, Universicy of Kentucky, Lexington, KY.

125 Wilson, B. N. 1983. Modeling Sediment Deposirioo, Resuspension, Mixing and

Bed Degradatio n in Derentio!l Pomk l}npubJishcd Ph .D. Dissertatiol1, Agricultural Engineering DCpannlCllt , Univers iry of Kellt'ucky, Lexington, KY.

Wischmeier, VI. H. 1959. A Rainfall Erosion Index for a Universal Soil Loss

Equation. Soil Seience Soeiety of Amerie. Proeeedings, Vol. 23:246-249.

\Xfischmeier, -..::tI. H . and D. D. Smith. 1965. Rainfall Erosion Losses from Crop­land East of rhe Rocky Mountains. Agriculture Handbook No. 282, U. S. Departmenr of Agriculture, Vlashingtun, D.C.

Wisehmeier, W. H., e. B. Johnson and B. V. Cross. 1971. A Soil Erodibility Nomograph fOf Farmland and Construction Sites. Journal Soil and Water Conservation 26(5): 189-193.

VI¡schmeier, W. H. 1975. Estimating rhe Soil Loss Equations Caver and Manage­ment Factor [or Undisrurbed Lands. Prcscnr and Prospective Technology for Predieting 5ediment Yields and Suurees, AR5 5-40, pp 118-125, Agricultural Research Scrvicc, U. S. DcpartJnl"llt uf Agricuhurc, \X'a.)!JiJlgton, D.C.

Wischmeier, W. H. and D. D. Smith. 1978. Predicting Rainfall Erosion Losses A Guide ro Conservation Planning. Agriculture Handbook No. 537, u. s. Oepartment of Agrieulture, Washington, O.e.

126 '-

'-'

..... --..... -'

--..,.;

..... -'

.....

..... ---..... -....., .....,

--'

. ....., ..... -'

'-J

..... '-' , '-'

--'

....,

..... --'

'-'

--..... ---' ,-~ i . r