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 @ d_derrick@r2d-eng.com

Enjoy the information!!

NAP TIME FOR CLEOPHUS !!!