STONE KEYS WITH VEGETATION. KEY ALL STRUCTURES INTO THE BANK !!!! This includes bank protection,...
-
Upload
rosaline-daniels -
Category
Documents
-
view
216 -
download
0
Transcript of STONE KEYS WITH VEGETATION. KEY ALL STRUCTURES INTO THE BANK !!!! This includes bank protection,...
STONE KEYS WITH
VEGETATION
KEY ALL STRUCTURES INTO THE BANK !!!! This
includes bank protection, grade control, river training
structures, everything!!Cheap insurance!!
HERE ARE SOME FAILURES
THE KEY TO STABILITY IS THE KEY (stream should be on the other side of the wooden retard)
TOTAL FAILURE 2 YEARS AFTER BEING BUILT-9 Mile Run - April 2007
Flanked grade control structure. Water should be flowing over this structure, not around the end. Key way too short & not vegged.
FAILURE-US AIR FORCE ACADEMY, CO.-PIX BY DERRICK-AUG 2010
FAILURE-Looking DS @ flanked structure with massive bank erosion
FAILURE-US AIR FORCE ACADEMY, CO-PIX BY DERRICK-AUG 2010
FAILURE-Looking DS at total failure & active eroding bank. Whatever objects were put in the stream are flanked & destroyed.
TOO STUPID - LONGFELLOW CR., SEATTLE, WA-DERRICK 8-22-2012
TOO STUPID – Looking US at upstream gabion keyed inside culvert. Wrong. This key should butt up to the culvert header wall (further to right).
A bank protection project should start
& end in stable (usually depositional)
areas.
Protection starts late & ends early, resulting in erosion at
both ends of project
FEMME CREEK, ST. LOUIS AREA, MO.
A key has one main function: to connect bank protection works, or
river training structures (Rock Vanes, Bendway Weirs, etc.), or
grade control structures to the rest of the world, & not let the river
“flank” (get behind or bypass) the structures.
Keys are best built of self-adjusting (well-graded), preferably self-filtering stone. If not
self-filtering, a granular filter might be needed. Stone in the key can be the same used
as bank paving or LPSTP. Keys could be built of large blocky stone that will not adjust (not recommended) & must be choked with
smaller stone. Amount of stone in key should equal or exceed the amount of stone used per
ft in the bank protection or river training structure.
Mid-project keys (red lines) are perpendicular to high flow & connect the tie-back or LPSTP to the bank (the rest of the world)
Tie-backs (blue lines) will connect
the LPSTP to the key. The
key, sometimes
called the key root, is dug
into the bank.
20-30 degrees
Flow
Key designs for continuous bank protection.
Both the upstream &
downstream keys should be angled 20 to 30 degrees to high flow. All
stone keys are vegetated, soil-gravel-cobble
choked, & overfilled 1.5 ft high with soil
(will settle)
Downstream key
Upstream keyInner bank20-30
degreesLongitudinal Peaked Stone Toe Protection
Outer bank
On the landward end (away from the stream), all keys need to tie into roughness, or a higher
elevation, or hopefully both!! Key crest elevation can be determined by flow elevation (Q-10, Q-100, etc.) or built to top bank, or to
top bank & then a distance into the bank (termed a key root). On the Mississippi River
key roots are dug 300 ft into the bank, Red River key root is a 100 ft long. Rule of thumb
for small streams: max. bank height plus max. scour depth = key root length
The downstream key on LPSTP in Reach 11, Harland Creek, Tchula, MS., built
1993. The key is angled 20-30 degrees to dominant (high) flow so that flow
smoothly transitions & stream width smoothly expands, thus reducing the
tendency for powerful recirculation to form (return currents). In this case
deposition occurred DS of the key (bank protection for free)
Looking US on Harland Creek, Tchula, MS at smooth LPSTP (1.5 tons/ft) with correctly angled downstream key with deposition (free bank protection) right where the photographer is standing. Installed Aug 1993. Pix Derrick 1996
The key itself should be heavily vegetated so as to slow flow velocities over the key. Slow water on the overbank means less
chance of flanking. Vegetation is designed to act like a Living Dike & can be closely
spaced adventitious rooting poles, or rooted stock plants, or container plants. In some cases the length of the key can be extended with vegetation alone, or other
materials (buried anchored logs with veg).
Adventitious Living Poles of appropriate species. As the key goes up in elevation,
the pole species might have to be changed to a species preferring dryer conditions
Flow
Live Pole Planting Layout for all Keys.
All of the green lines delineate
rows of adventitious live
poles (willow, dogwood, etc.), planted deep &
dense (typically 3 poles per linear
ft.)
Downstream key
Inner bankLongitudinal Peaked Stone Toe Protection
Upstream key
The upstream key on Chenunda Creek, Wellsville NY. The key is angled 20-30 degrees to dominant (high) flow so if the thalweg of the stream meanders into the key, that key “nudges” the stream back into
alignment. Never fight nature!!
Construction 9/19/2006.
Looking US. Digging the US key at a 20 to
30 degree angle to where if the stream
meanders toward the
key, the high flow might
attack the key
Pix by Derrick
High flow
angle
Key angle
Looking US. Hoe placing
big stone (NYS DOT
heavy) in US keyway.
Medium & small stone
will be added as a choke.
Pix by Derrick
Construction 9/20/2006. Looking at angle of key to stream flow. More stone will be added & then
soil choked so the landowner can grow a lawn.
Pix by Derrick
High flow angle
Key angle
Harvesting Pole-sized Adventitious Rooting Material
for the Key
Matt Horvat with safety glasses & ear plugs cutting willows with chainsaw
CONSTRUCTION-TOLEDO OHIO PROJECTS. PIX BY KRIS PATTERSON 8-2008
Renewable resource-willow will grow back multi-stem after cutting
CONSTRUCTION-TOLEDO OHIO PROJECTS. PIX BY KRIS PATTERSON 8-2008
Poles ready to have leaves & side branches removed.
CONSTRUCTION-TOLEDO OHIO PROJECTS. PIX BY KRIS PATTERSON 8-2008
Teen volunteers cutting side branches & leaves from poles
CONSTRUCTION-TOLEDO OHIO PROJECTS. PIX BY KRIS PATTERSON 8-2008
Use stout twine to bind a set number of poles into a manageable bundle. Twine should be looped & tied at one end, then looped
& tied at the opposite end, thus providing a carrying handle
CONSTRUCTION-TOLEDO OHIO PROJECTS. PIX BY KRIS PATTERSON 8-2008
Soaking willow, half out of water, half of the pole should be submerged with butt ends underwater. Research by Dr. Doug Shields showed that soaking
Black Willow 10 days will increase root production by 2,600%, 100% flushed out, & twice as many survived. Fence is to protect from beaver browse.
CONSTRUCTION-TOLEDO OHIO PROJECTS. PIX BY KRIS PATTERSON 8-2008
Dump truck load level full of Sandbar & Streamco Willow, & Ruby Red osier dogwood, (1,500 poles total).
Pix by Derrick
MID-PROJECT KEYS FOR CONTINUOUS PROTECTION MEASURES & KEYS FOR
REDIRECTIVE TECHNIQUES, ARE ALMOST ALWAYS
ORIENTED PERPENDICULAR TO THE BANK (& roughly high flow).
A MID-PROJECT LIVING KEY ON
CHENUNDA CREEK Vegetated & soil-choked
stone key is perpendicular to high flow (& the bank)
Detail for key
Cross-section for keywayFlow
Place granular filter if not using a self-
filtering stone
Detail for key
Flow
Place Willow Poles against one or both sides of trench
Detail for key
Flow
Make sure the butt ends of poles are either in the water or in the capillary (or vadose)
zone (all the way to the bottom).
Construction 9/19/2006.
Digging a mid-project key
perpendicular to the bank.
Some veg (willow poles) in
placePix by Derrick
Place soil to cover at least the butt ends of the poles
Detail for key
Flow
Place stone in trench Detail for key
Flow
Construction 9/19/2006. Looking at key. Butt ends of willow & dogwood poles down deep. Some large stone placed.
Pix by Derrick
Choke stone with gravel-cobble (white
areas) & water in
Detail for key
Flow
Backfill and overfill with native soils, then compact (some settling
will still occur)
Detail for key
Flow
Construction 9/21/2006. Key stone is now soil-gravel choked.
Pix by Derrick
Seed
DONE
Detail for key
Flow
13 MONTHS LATER-low flow. Veg in key is robust.
Pix by Derrick 10/15/2007
2.75 YEARS LATER-Lush growth from 2 rows of live poles on mid-project key.
2 YEARS 9 MONTHS AFTER CONSTRUCTION-CHENUNDA CR.-DERRICK 6-18-09
VEGETATION IN KEY ACTING AS A LIVING DIKE ON
ONONDAGA CREEK (perpendicular to high flow)
On
ond
aga
Cre
ek @
Nic
hol
Roa
d B
rid
ge,
LaF
ayet
te, N
Y –
pro
ject
pla
nte
d 5
-15-
2007 Looking toward stream. Key vegetation is
4 ft deep. Key stone buried to right of veg.
Pix by Derrick
On
ond
aga
Cre
ek-Y
ear
2 July 10, 2008. {middle of second growing season} Key vegetation is over 7 ft tall. Willow & dogwood. Will act as a Living Dike.
Pix by Derrick
DESIGN CONSIDERATIONS FOR LPSTP KEYS • LPSTP must be deeply keyed into the bank at both the upstream and
downstream ends and at regular intervals along its entire length. Charlie Elliott’s spacing rules-of-thumb for keys in flat-sloped sand bed water bodies: 50 to 100 ft intervals on smaller streams, 1 to 2 bankfull widths on larger waterways.
• Keys at the upstream and downstream ends of LPSTP should not be at a 90 degree angle to the LPSTP structure, but at 20 to 30 degrees to HIGH FLOW.
• Keys should go far enough back into the river bank so river migration will not flank the key & the LPSTP. Analyze the meander belt width of the stream or river to determine if the key can get flanked.
• Keys should be vegetated if possible. Key length can be extended with vegetation alone in some cases.
• Volume of material per ft of key should equal or exceed the volume of material per ft in the LPSTP
• Minimum key width should be two times the D-100 of the stone used
A short 90 degree key at the US end of the stacked stone wall. With erosion US, structure failure is imminent.
TURKEY CREEK, KANSAS CITY, MO –PIX BY DERRICK-2/5/2009
This PowerPoint presentation was developed & built by Dave Derrick.
Any questions or comments, call my personal cell @ 601-218-7717, or email @ [email protected]
Enjoy the information!!
NAP TIME FOR CLEOPHUS !!!