FEMA-165

MAY 1989

A luvial Fans:Hazards and Management

I---C -11~4- 411r, - -

- f~~~~~~~~

Aerial view of the Magnesia Spring Canyon alluvial fan flood of July 1979, which caused over$7 million in damage, and one death

FEDERAL EMERGENCY MANAGEMENT AGENCYFederal Insurance Administration

Office of Loss ReductionFebruary 1989

ALLUVIAL FAN HAZARDS dI THE UNITED STATES

Flood hazards in the American West are often greatly under-estimated due to the dry conditions, lack of rainfall and ab-sence of defined watercourses. Ironically, western floods arequite severe and powerful, exhibiting unpredictable flow pathsand high velocities that usually occur with little advancewarning time. These floodscan cause considerable erosion insome areas while depositing large amounts of sediment anddebris in others.

With rapid growth continuing throughout the West (particularlyin many major metropolitan areas) hillside building sites havebecome more popular as the supply of prime developable landbecomes depleted. This has resulted in an increasing amountof development occurring in floodplain areas called alluvialfans.

within participating communities to purchase insurance tocover flood losses affecting structures and their contents.

- Figure 1.Dense developmenton alluvialfansin theSouthMountaln area of Phoenix,Arizona. Note the numerous branching channels.

Alluvial fans are triangular orfan-shaped, gently-sloping land-forms which typify the floodplain management dilemma facingmany western states today: fans provide attractive develop-ment sites due to their commanding views and good localdrainage, yet harbor all the severe flood hazards whichendanger arid western communities.

Development pressure on alluvial fan areas is intensifying,creating a critical need to provide guidance to communities,developers and citizens on how to safely accommodate growthwhile protecting life and property from flood hazards. Toaddress this need, the Federal Emergency ManagementAgency (FEMA) has designed this brochure to increase aware-ness of alluvial fan flood hazards, and to provide generalguidance on the techniques and strategies for minimizinglosses from these hazards when building and developing.FEMA is the agency which administers the National FloodInsurance Program (NFIP), which enables property owners

Figure 2.Damaged homes on a fan In Ocotillo Wells, California, which lies in easternSan Diego County. Tropical Storm Kathleen caused extensive floodingSeptember9-11, 1976, there andthroughout Riverside andimperialcoun-ties to the north and east. The channel braiding shown in the photo istypical of alluvial fan flooding, and thus Itis difficult to predlct the locationof floodflows.

Where Are Alluvial Fans Found?

In the United States, alluvial fans are typically found along thebase of mountain fronts in the western states of California,Arizona, Nevada, Colorado, Utah, Idaho, New Mexico, Wyo-ming, Montana, Oregon and Washington. Here, the infrequentbut intense storms typical of arid and semi-arid climatescombined with abrupt changes in topography create the nec-

1

IN I a 06 M -, t I IM i ON I WHIEN, 0 I WI A

-� � Cd

essary conditions forfan formation. Differences in climate andgeology have produced mostly active fans in regions such asNevada and California, and inactive fans in southern Arizona.Active fans exhibit braided channels and erratic flowpathstypical of ayoungfanformation. Fans in southern Arizonatendto exhibit more predictable channels and flood paths due totheir geologically older setting. It has been estimated that 15to 25 percent of the arid West is covered by fans.

How Are Alluvial Fans Formed?

Alluvial fans build up over the course of geologic time throughthis general sequence:

1. Rock and soil are eroded from the mountain watershed;

2. These sediments are transported through stream chan-nels via storm-generated floodwaters;

3. The floodflow which has been confined in mountainravines emerges onto the wide, flat valley slope, andprogressively loses velocity while depositing sedimentas it travels downf an.

The sediment deposits are generally narrow and steep at thehead of the valley, broadening as they spread out onto thevalley floorin awedge or conical shape. The natural processesresponsible for fan formation have frequently been observedto occur in a specific sequence and range of location along thelength of the fan. For the sake of illustration, these processeswill be presented in a generalized fashion to portray theformation of the "idealized" alluvial fan. In reality however,wide variations in the physical characteristics of each fansystem affect the actual location, extent and severity of theseflood processes. Variations occur between areas exhibitingdifferences in climate and geology, as well as among fanswithin the same valley.

FORMATION OF AN "IDEALIZED"

ALLUVIAL FAN

1. Streamrflow from intense rainstormsemanates from the confined channel of amountain canyon and proceeds onto therelatively flat valley below. The canyonoutlet forms the APEX of the fan, whichrepresents the point of highest elevation onthe fan.

2. Flow leaving the apex spreads onto theuppermost portion of the alluvialfan surfacevia a single high-velocity channel. Thissingular channel will either follow a pre-existing path cut from past flood events,possibly deepening the channel in a proc-ess called entrenchment, or cut a new pathdownslope. Flood hazards in this CHAN-NELIZED ZONE of the upper fan regioncan be severe due to the high velocity offlow, the presence of debris from the wa-tershed, and the unpredictable location offlowpaths.

3. As the single channelflow encountersthe flatterslope ofthemid-fan area, it widens and becomes shallower, losing veloc-ity and depositing sediment and debris. Materials that becomedeposited into previously-cut channels can backfill the oldstreambeds, leading to the abrupt development of new chan-nels in a process called avulsion. The erosion/deposition proc-esses include channel braiding, where singular flows split andrejoin as channels are alternately cut and filled with sediment.These BRAIDED ZONE processes occur erratically, creatingrandom, unpredictable flow patterns.

4. Toward the base of the fan, called the TOE, watervelocitiesare further reduced as the fan surface becomes more uniform,its slope flattens and water infiltrates the soil surface. In thisportion of the fan, SHEET FLOW (shallow, overland flow) iscommon, though flow velocities may remain high. Adjacentfans which have formed along mountain fronts tend to con-verge near their bases, producing alluvial APRONS, or zonesof coalescence.

2

1. APEX

4. SHEET FLOWZONE

fgure 3

How Are Alluvial Fans Identified?

The gentle, imperceptible slopes and extensive size of manyfans can sometimes make their identification in the fielddifficult. As a result, many homeowners do not realize that thepanoramic views of the valley below are due to their elevatedlocation on an alluvial fan. The initial identification of thepresence and extent of fans within the community is therefore

Figure 4.This U.S. Geological Survey topographic quadrangle map has been en-hanced to show the concentric contour pattern typical of alluvial fans.Depicted here are two alluvial fans In Wenatchee, Washington.

best accomplished through the use of topographic maps oraerial photos. Topographic maps (such as those produced bythe U.S. Geological Survey) reveal concentric semicircularcontours that bow downslope, as shown on the figure above.The use of soil survey maps (such as those developed by theSoil Conservation Service) can also indicate the presence ofalluvial (water-transported) soils which often comprise fanformations. In confirming the location and extent of alluvialfans, the final detailed interpretation of maps, air photos andfield data should be made by a professional geologist, hydrolo-gist, and/or engineer.

What Are The Flood Hazards Associated With AlluvialFans?

Alluvial fan floods do not exhibit the more predictable behaviorand well-defined boundaries normally found in most riverinefloods. The behavior and path of flood water in any individualflood event as it proceeds from the apex to the toe is a directresult of the flood processes previously illustrated. Theseprocesses vary as a function of the flow's sediment contentand velocity, the fan's slope, soil and vegetative cover, andtypes and amount of fan development.

Alluvial fan flows are subject to lateral migration and suddenrelocation during the course of a flood, and may not even followthe same path in subsequent floods; in any flood event,however, a part of the fan will always be subject to flocdhazards. Thus, it is generally not appropriate to utilize thelocation of past flow paths in the prediction of future hazards.The full range of hazards that may be encountered on fansinclude:

* high-velocity flow (as high as 15-30 feet per second),producing significant hydrodynamic forces (pressureagainst buildings caused by the movement of flowingwater)

* erosion/scour (to depths of several feet)

* deposition of sediment and debris (depths of 15-20 feethave been observed)

* debris flows/impact forces

* mudflows

* inundation, producing hydrostatic/buoyant forces (pres-sure against buildings caused by standing water)

* flash flooding (little, if any, warning times)

An often-overlooked "hazard" is the tendency to underesti-mate boththe potential and severity of alluvialfanflood events.The infrequent rainfall, gently-sloping terrain, and often longtime spans between successive floods contributeto asense ofcomplacency regarding the existence of possible flood haz-ards. Though the intense rainstorms which produce fan floodsoccur randomly, they nevertheless can develop very rapidly atany time, and can recur with any frequency.

3

I 3 � W-10

Figure 5.High-velocity flows battered homes in Ocotillo Wells, Californiaduring the September 1976 flood caused by Tropical Storm Kath-leen.

Figure 6.Fast-moving floodwaters caused scour, erosionand structural damage to numerous RanchoMirage, Califomia homesin September 1976andin July 1979.

Figure 7Large volumes of sediment can be deposited by floodwaterduring the course of an alluvial fan flood event.

4

"am

Figure 8.Four successive days of flooding in August 1982 caused debris and waterdamage In Ouray, Colorado. Thirty-five homes and businesses were dam-aged, andnumerousbridges weredestroyed. Shown here is debris depositedby Portland Croek. (Courtesy of Dave Vince, City of Ouray)

Figure 9.Inundation of homes by shallow flooding cancause extensive interior damage.

5

>�VdtZ' .•+;y,.Qtc�--$� V � V-" � VV ,�'��4'k�VVŽ' '%-ts -A-� �i � V -. -* j �- � � �-&�>i � I�&%�3P�%VTh4 � �

A Word About Debris Hazards ...

In the case of geologically younger, or active fans, the naturalprocesses which, over time, formed the fan continue to actupon its surface in a somewhat random fashion. Thus, theentire fan surface represents a potential site for flood, sedi-ment and debris deposition and scour, and is a dangerouslocation upon which to build.

In geologically older regions, alluvial fan processes tend tofollow more predictable patterns, and floodflows may remainwithin defined channels as theydischarge downslope. Fans orportions of fans which are no longer subject to these flows areconsidered inactive, and may be regarded as less hazardousconstruction sites.

Regardless of whether a fan is active, inactive, or both, thereis always some degree of unpredictability of the flood hazardon all fans.

Debris flows can result from the presence of a large percent-age (up to 70-90% of flow by weight) of fine sediment such assilt and clay in steeply-flowing floodwaters. This enables themuddy flow to transport sand, gravel, boulders, and dislodgedtimber and brush from the mountain watershed onto a fan'ssurface. Conditions favoring the formation of debris flows are:avail able unconsolidated silt, clay and larger rock in the basinwatershed (due to minimal vegetation), heavy or sustainedrainfall in the basin, and the presence of steep basin and fanslopes. Fans which have been created from repeated debrisflow activity are called debris fans, and are composed ofdeposits of rock, soil and vegetation from the upstream water-shed. Debris fans are found in areas where mountain systemsare subject to tectonic forces of uplift. Colorado, Utah, Wyo-ming, Montana, and parts of California, Nevada and Arizonacontain the bulk of debris fans and flows.

Figure 10.Development on a debris fan in Georgetown, Colorada Note the structures'proximity to the steep mountain slope above. (Courtesyof the Colorado Geological Survey)

6

Active vs. Inactive Fans

Figure 11.Debris flow damage In Glenwood Springs, Colorado in July 1977. Propertydamage to homes andpublic facilities and cleanup costs totalled approxi-mately $2 million. (Courtesy of the Colorado Geological Survey)

Figure 12.Boulders several feet in diameter may be transported by sediment-laden flood flows. This debris was deposited south of Sierra Vista,Arizona in June 1988 following heavy rains in the Huachuca Moun-tains.

Figure 13.This small debris basin was constructed In 1984 on Cascade Creek inOuray, Colorado after several instances where debris blocked thechannel and worsened flooding conditions. The basin allows debris tosettle out of moving floodwaters. (Courtesy of Dave Vince, City ofOuray)

7

-g~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~I~ m- E !

MANAGING DEVELOPMENT ON ALLUVIAL FANS

It must be stressed that any development activity sus-tained on the active portion of an alluvial fan disrupts andalters the natural flood processes which perpetuate Itsformation, and subjects any structure situated on the fanto unpredictable, erratic hazards during flood events.Furthermore, any new construction can redirectflood anddebris flow to adjacent properties and thereby increaseflood hazards In other areas. A comprehensive approachis therefore needed to manage development on fan areassuch that the entire fan's natural flood processes andresulting hazards are taken Into account. The develop-ment and implementation of a comprehensive approachis best handled on the local government level throughplanning, zoning and building permit processes. Throughthese processes, future development can be planned andits effects on flood hazards adequately addressed.

How Should a Community Manage Development on Allu-vial Fans?

A comprehensive or master planning approach to managinggrowth on an alluvial fan considers fan conditions from apextotoe while guidingfuture developmentinacoordinated manner.The keystone of this planning process is the community'sselection of flood/debris hazard management tools. Thechoice of tools will depend upon the nature and location of thehazards, and the location, timing, size and density of existingand future development. These tools can be structural (lev-ees, basins, channels) or nonstructural (zoning, public acqui-sition, subdivision regulations, building standards). The fanmanagement plan may be incorporated as aseparate elementwithin the community's existing comprehensive plan, or maystand alone as a separate document. The planning processincorporates the following steps:

should be mapped, as should the location of previous andpotential debris flow paths. If the community has had its alluvialfan areas studied and mapped while preparing its FloodInsurance Rate Map (FIRM), some of this data may already beavailable. The FIRM will delineate the flood having a onepercent chance of occurring in any given year (the 100-yearflood), which can serve as the basis of more detailed hazardanalysis and mapping.

2. PLAN FUTURE DEVELOPMENT. Identify the areas of thefan which require immediate flood protection, taking intoaccountthe location and density of existing development. Es-tablish the location, timing, and amount of future developmentin light of the delineated hazards. Development in the mosthazardous portions of the fan should be restricted.

3. CHOOSE FLOOD MITIGATION TOOLS. Analyze therange of flood management/control tools available in consid-eration of identified hazards, present and planned density andlocation of development, cost to locality, and public accep-tance. This is accomplished through the establishment ofcommunity goals, and through coordination among localgovernment officials, planners, engineers, residents, and thedevelopment community. The most widely-used alluvial fanflood management tools are presented in the next table.

4. ENFORCE REGULATIONS. Ensure the effective applica-tion and operation of the selected flood management tools byadopting and enforcing regulatory controls:

a. Zoning ordinances, subdivision regulations and openspace/land acquisition plans can be used to prohibit orotherwise limit growth in high hazard areas, and wouldallow the safe passage of flood waters;

1. IDENTIFY THE HAZARDS. Using qualified geologists,hydrologists and engineers, conduct a detailed study of indi-vidual watershed and fan characteristics in orderto determinethe severity and location of hazards to be expected on eachfan. Where appropriate, active and inactive portions of the fan

b. Building codes can help ensure safe residential con-struction;

c. Maintenance/inspection requirements can help guaran-tee the effective operation of structural flood controlmeasures;

5. EDUCATE CITIZENS. Communities should initiate publicawareness programs on alluvial fan hazards, install floodwarning systems (where practical), and encourage the pur-chase of federal flood insurance.

This comprehensive planning approach Is most effectivewhen implemented as early as possible during fan devel-opment. A community can then exercise maximum con-trol over future desired density levels and have the mostflexible choice of flood management tools. It Is also bestutilized on a multi-community or regional scale, espe-cially when multiple fans occupy range-fronts which mayspan several jurisdictions.

8

ALLUVIAL FAN FLOOD MAMAGEMENTTOOLS

(Based on Size and Density of PlannedDevelopment)

Whole Fan Protection

Levees

Channels

* Detention basins

* Debris basins/fences/deflectors/dams

Design Considerations: Whole-fan protection includes large-scale structural measures appropriate for use on extensively-developed fans, and which are most cost-effective in high-density situations. Structures must be designed to interceptupstream watershed flow and debris at the apex and totransportwater and sediment around the entire urbanized fan.Structures must be designed to withstand scour, erosion,sediment deposition, hydrostatic forces, impact and hydrody-namicforces, and high flow velocities. Continual maintenanceis essential for optimal operation, and can be costly. Thesestructures are most often funded through federal and statesources, but can also be financed through special regionaldistricts, local governments, or developers.

Subdivision or Localized Protection

* Drop structures to reduce flow velocity

* Debris fences

* Local dikes, channels

* Site plans to convey flow

* Street design/alignment to convey flow

* Elevation on armored fill

Design Considerations: These are smaller-scale measuresthat can be used throughout moderate-density fans to safelytrap debris, and to route water and sediment around orthroughindividual residential developments. Protection elements mustprevent formation of new flow paths and/or the relocation ofexisting paths; flood control structures must resist high veloci-ties, erosion, deposition, hydrodynamicand hydrostaticforces.The most effective strategy includes a combination of ele-ments; the entire protection plan must be coordinated withother similarly-scaled efforts to avoid adverse impacts toadjacent property. These measures can be financed privatelyby developers.

Figure 15.Shown here is the channelization of Flamingo Wash adjacent to newconstruction near Las Vegas, Nevada. Gabions (rock-filled baskets en-closed with wire mesh) help stabilize the channel sideslopes. Wallsprovide some additional flood protection.

Figure 14.This concrete channel was designed to carry floodwater downslope inPalm Desert, California. -

9

E- _1m . t - 4m&IA- --h :tSingle Lot/Structure Protection

* Elevation on properly designed foundations (piles, col-umns or armored fill)

* Floodwalls and berms

* Reinforcement of uphill walls, windows and doors againstdebris impact

Design Considerations: These measures are most cost-effectively implemented at low development densities, butshould be considered for all structures on fans. Owners ofexisting structures should consider retrofitting their homes toprotect against future flood hazards; new lots should beplanned with adequate open space to accommodate flowpaths. Velocity/scour, sedimentation and debris impact mustbe addressed in the design of elevated foundations and offloodwalls. Floodwalls should not be solely relied upon forprotection, but as a supplement to elevated foundations.These measures are usually financed by the homeowner.

Figure 16.This home in Palm Desert, California has been elevated on till. Utilities(shown against the left side of the house) have also been raised tominimize potential flood damage.

The choice of the appropriate measure(s) will ultimately de-pend upon the community's development plan and the leveland extent of protection desired.

What Factors Should Be Considered When Building On ASingle Lot?

It is recommended that single lot development only proceedwithin the framework of a comprehensive plan for the alluvialfan, which has identified the fan's flood hazards, designrequirements for the safe construction of individual sites, andhow each site would fit into a coordinated approach. If such acomprehensive plan has not been developed, then the follow-ing general steps should be undertaken to minimize thepotential flood risk for any proposed structure:

1. AVOID THE MOST HAZARDOUS AREAS OF THEFAN.

2. Consult with local planning, building, and engineeringofficials to discuss the potential hazards specific to thesite, regulations in effect which would specify methodsof construction, and any permits required for building ina flood hazard area.

3. Using the expertise of local engineers, determine thedepth and velocity of the 100-year flood flow whichwould affectthe site, including the possible effects of anydebris hazards. -, 6 -r!gS

4. ELEVATETHE @

STRUCTUREso that the low-estfloor(includ-ing basement)isat orprefera-bly above) thedeterminedflood depth.The most effec-tive methods ofelevating struc-turesonfans areto use piles or -I

columns, or toelevate on ar--________mored fill.

5. Flood walls canalso be used to Figure 17.

divert flow Thishomeis underconstruction on an activealluvialfan below the McDowellMountainsin

around elevated Scottsdale, Arizona.structureswhere expected flood flows are of minimal depth andvelocity, wherethere is no potential for debris hazards orincreased damage to adjacent structures.

6. Avoid the placement of windows and doors on the uphillside of the structure to keep debris and flood water fromentering the building. If such openings must be used,theyshould bereinforcedtostrengthenresistanceagainstdebris and hydrodynamic forces.

10

Fill:SINGLE STRUCTURE PROTECTION

Piles, Columns, or Posts:

* Minimize the structure's exposure to flood hazards

* Eliminate obstructions to natural flow paths

* Do not significantly affect flood flow hydraulics

* Size and number of piles must be adequate to providestructural support to building; must be embedded tosufficient depth, and be adequately anchored to both thestructure and to subsoil/bedrock to withstand scour anderosion

Figure 18.A home elevated on columns, Illustrating how the area below the first floorshould be limited to parking, access, or storage. Utilities and mechanicalequipment should also be elevated above ground at least to the depthindicated on the FIRM.

* Should only be used in low to moderate velocity/depthconditions

* Must be armored above and below grade to withstandscour, erosion, and debris impact and to protect thestructure's foundation

* Should be oriented parallel to expected flood flow toreduce debris damage, to avoid defledting flow to adja-cent or downstream property, and to minimize obstruc-tion to flow

* Can be landscaped

Figure 19.This home has been elevatedon earth fiiandlandscaped. The vegetationhelps to stabilize the fill to protect It from erosion.

Floodwalls or Berms:

* Should only be used in very low velocities/depths (sheetflow velocity of less than 5 feet per second/depth of lessthan 3 feet); should only be used near toe of fan or wherelarge sedimentation and debris loads are not likely

* Should be able to resist erosion at base and below grade

* Should be oriented to avoid diversion of hazards toadjacent or down stream property

* Can be effective when used as supplemental protectionfor elevated structures

Since flood hazards threatening an individual site on an alluvialfan are highly unpredictable, the methods used to safeguard astructure will depend upon conditions unique to the location ofthe site itself. It is therefore imperative to consult closely withlocal engineering experts to determine the site's particularphysical conditions and expected flood and debris hazards.

Figure 20.Floodwalls, such as this example In Phoenix, Arizona, should be con-structed parallel to the expected flow direction to minimize the diversionof hazards onto adjacent property.

MEMEM

-1"

10 1* X

How Does the P/PIP Address Development On AlluvialFans?

The NFIP identifies alluvial fan hazards on FIRMs as Zone AOand provides information on flood depths and velocities. AOzones are Special Flood Hazards Areas (SFHA) subject toinundation by 1 00-year sheet-type flow, which are sometimesassociated with high velocities. If the community's FIRMidentifies AO zones with depths and velocities, constructionwithin those alluvial fan areas are subjectto certain regulations(in addition to those which apply to all SFHA's) found inChapter 44 of the Code of Federal Regulations, Part 60.3:

* Elevate lowest floor (including basement) above thehighest adjacent grade to at least as high as the depthnumber specified on the FIRM. (It is recommended,however, thatthe depth of flow assumed for a particularsite should take into consideration local topographicanomalies when determining the elevation of any floodprotection measure.) Mechanical and utility equipmentmust also be placed above the depth of flooding.

* Provide adequate drainage paths around structures onslopes, to guide floodwater around and away fromproposed structures. Do not deflect floodflow ontoadjacent properties.

As part of the FIRM revision process, FEMA will review thedevelopment plans submitted by owners of projects whorequest the removal of their property from the SFHA. Toensure thatthese projects are in fact protected from alluvialfanflood hazards, FEMA's review criteria require that the con-struction include elements which: do not cause the distur-bance of natural flood processes on the fan; allow forthe safecollection, passage, and disposal of flood-related water, sedi-ment and debris without negative impact to adjacent property;

address erosion, scour, deposition, impact and hydrostaticforces; provide that the design and maintenance of projectelements be coordinated with the local jurisdiction and/oragency responsible for flood control within the community.

With knowledge of local conditions and inthe interestof safety,state and community officials may set higher standards forconstruction in f loodplain areas. As with all f looding situations,FEMA encourages local jurisdictions to adopt floodplainmanagement measures which are more tailored to thecommunity's particular flood problems. This is especiallyimportant for communities prone to alluvial fan flood hazards,where each fan presents a unique set of flood conditions.

It should be noted that the provisions of Section 60.3 areminimum requirements; buildings constructed according tothese rules alone will not provide adequate protection againsthigh velocities ordebris loads unless additional measures areundertaken.

The unique qualities of each fan formation and its attendanthazards requires individualstudy andstrategicplanning usingthe guidance of government officials, engineers, hydrologists,and geologists. It is hoped that this publication has offeredsufficient information regarding the importance of guidingdevelopment on alluvial fans to provide the impetus for localknowledge and expertise. Intensified commitment to offsetcurrentandfuture flood losses on fans willgreatly complementthe work of professional groups and public agencies as theybegin to develop management and construction standards forthese special arid west flood hazards.

12

Figure 21.Portion of a Flood Insurance Rate Map (FIRM) panel for unincorporatedSan Diego County, California showing areas subject to 100-year foodhazards on the Henderson Canyon alluvial fan.

Figure 22.Flooding hit the community of Borrego Springs near the base of theHenderson Canyon alluvial fan In northeastern San Diego County whenTropical Storm Doreen crossed the area in 1977. This photo facessouthward across Montezuma Road, and shows the large amounts ofsediment deposited during this flood. The location of this damage isshown in the FIRM, Figure 21. In consideration of the frequency of floodevents andthe potential for developmentin the larger Borrego Valley area,a flood management plan is being finalized bySan Diego Countywhich willprescribe structural and nonstructural flood control measures for alluvialfans in the county.

13

APPENDIX A

For Further Information:

For information pertaining to hazard identification mapping and floodplain management, contact the Natural and TechnologicalHazards Division of the appropriate FEMA Regional Office, or the state NFIP coordinators listed below:

FEMA REGIONAL OFFICES

Region VI: (Arkansas, Louisiana, New Mexico, Oklahoma,Texas)Federal Regional CenterRoom 206800 N. Loop 288Denton, TX 76201-3698(817) 898-9127

Region Vil: (Colorado, Montana, N. Dakota, S. Dakota, Utah,Wyoming)Federal Regional CenterBuilding 710P.O. Box 25267Denver, CO 80225-0267(303) 235-4830

Region IX: (Arizona, California, Hawaii, Nevada)Building 105Presidio of San FranciscoSan Francisco, CA 94129(415) 923-7175

Region X: (Alaska, Idaho, Oregon, Washington)Federal Regional Center130 228th Street, SouthwestBothell, WA 98021-9796(206) 487-4682

NFIP STATE COORDINATORS

ARIZONAArizona Department of Water ResourcesEngineering Division15 South 15th AvenuePhoenix, AZ 85007

Ms. Terri Miller(602) 255-1566

CALIFORNIACalifornia Department of Water ResourcesP.O. Box 942836Sacramento, CA 94236-0001

Mr. A. Jean Brown(916) 445-6249

COLORADOColorado Water Conservation BoardState Centennial Building, Room 7211313 Sherman StreetDenver, CO 80203

Mr. Brian Hyde(303) 866-3441

IDAHOIdaho Department of Water ResourcesEngineering Division1301 N. OrchardBoise, ID 83706

Mr. Lotwick Reese(208) 334-7887

MONTANAMontana Department of Natural Resources and ConservationFloodplain Management Section1520 East 6th AvenueHelena, MT 59620

Mr. John Hamill(406) 444-6646

NEVADANevada Division of Emergency Management2525 South CarsonCapitol ComplexCarson City, NV 89710

(702) 885-4240

NEW MEXICONew Mexico State Engineer's OfficeDesign and Construction SectionBataan Memorial BuildingSanta Fe, NM 87503

Mr. Don Lopez(505) 827-6140

OREGONOregon Department of Land Conservation and Development1175 Court Street, N.E.Salem, OR 97310

Mr. Jim Kennedy(503) 378-2332

UTAHUtah Office of Comprehensive Emergency Management1543 Sunnyside AvenueSalt Lake City, UT 84108-0100

(801) 533-5271

WASHINGTONWashington Department of EcologyShorelands and Coastal Zone Management ProgramMail Stop PV1 1Olympia, WA 98504

WYOMINGWyoming Emergency Management AgencyP.O. Box 1709Cheyenne, WY 82003

Mr. Grant Sorenson(307) 777-7566

Mr. Jerry Louthain(206) 459-6791

16

V � � 4�r�A�

APPENDIIX B

FEMA Publications:

The following publications are free of charge and can beobtained by writing to:

Federal Emergency Management AgencyP.O. Box 70274Washington, D.C. 20024ATTENTION: Publications

FEMA-13, Flood Emergency and Residential Repair Hand-book-Outlines for the homeowner actions that can be takenbefore and after a flood to help reduce damage and speedrepairs.

FEMA-15, Design Guidelines for Flood Damage Reduc-tion-General information on flooding and how to properlydesign and build in floodplain areas.

FEMA-54, Elevated Residential Structures-Properdesignand construction methods for elevated buildings.

FEMA-1 14, Design Manual for Retrofitting Flood-proneResidential Structures-Presents floodproofing techniquesthat can be used for existing residential structures.

ACKNOWLEDG EMENTS

The Office of Loss Reduction wishes to thank the following fortheir information, advice and photographic materials usedduring the preparation of this publication:

Arizona Department of Water ResourcesAssociation of State Floodplain ManagersCalifornia Department of TransportationCochise County, Arizona Department of Public WorksColorado Water Conservation BoardColorado Geological SurveyFederal Emergency Management Agency-Federal

Insurance Administration-Oftice of Risk AssessmentFederal Emergency Management Agency-Natural

and Technological Hazards Division-Regions 6, 8, 9,and 10

Michael Baker, Jr. EngineersCity of Ouray, ColoradoPima County, Arizona Transportation and Flood

Control DistrictSan Diego County, California Flood Control DistrictTudor Engineering Company

FEMA-1 16, Reducing Losses In High Risk Flood HazardAreas: A Guidebook for Local Officials-A guidebook tohelp local governments improve theirfloodplain managementprograms for high risk flood hazard areas.

FIA-2, Questions and Answers on the National FloodInsurance Program-This pamphlet is intended to acquaintthe public with the National Flood Insurance Program. it isdesigned for readers who do not need a detailed history orrefined technical or legal explanations, but do need a basicunderstanding of the Program and the answers to somefrequently asked questions.

FIA-14, Guide to Flood Insurance Rate Maps-This guidewill help you read and understand a Flood Insurance Rate Map(FIRM). It contains illustrations and a step-by-step example ofhow to use a FIRM.