soil choked stone keys with vegetation n.
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  1. SOIL-CHOKED STONE KEYS WITH VEGETATION By Dave Derrick, Potomologist & VP, River Research & Design, Inc.

  2. KEY ALL STRUCTURES INTO THE BANK !!!! This includes bank protection, grade control, river training structures, everything!!Cheap insurance!! HERE ARE SOME FAILURES

  3. THE KEY TO STABILITY IS THE KEY (stream should be on the other side of the wooden retard)

  4. Flanked grade control structure. Water should flow over the structure (blue arrow), not around the end. Key way too short, does not go up to a higher elevation, & is not vegged. Blocky stone rarely works well in this application. Key failure TOTAL FAILURE 2 YEARS AFTER BEING BUILT-9 Mile Run - April 2007

  5. Flanked grade control structure. Water should be flowing over this structure, not around the end. Key way too short & not vegged. TOTAL FAILURE 2 YEARS AFTER BEING BUILT-9 Mile Run - April 2007

  6. On the landward end (away from the stream), all keys need to go up the hill & tie into roughness (a forest). If no forest is available, one should be planted!!!

  7. FAILURE-Looking DS @ flanked structure with massive bank erosion FAILURE-US AIR FORCE ACADEMY, CO.-PIX BY DERRICK-AUG 2010

  8. FAILURE-Looking DS at total failure & active eroding bank. Whatever objects were put in the stream are flanked & destroyed. FAILURE-US AIR FORCE ACADEMY, CO-PIX BY DERRICK-AUG 2010

  9. TOO STUPID – Looking US at gabion keyed inside culvert. Wrong. This gabion should butt up to the culvert header wall (to right, red outline). TOO STUPID - LONGFELLOW CR., SEATTLE, WA-DERRICK 8-22-2012

  10. A bank protection project should start & end in stable (usually depositional) areas.

  11. FEMME CREEK, ST. LOUIS AREA, MO. Protection starts late & ends early, resulting in erosion at both ends of project

  12. 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.

  13. 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.

  14. Longitudinal Peaked Stone Toe Protection 20-30 degrees Flow Inner bank Upstream key Outer bank 20-30 degrees 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 Tie-backs (blue lines) will connect the LPSTP to the key. The key, sometimes called the key root, is dug into the bank. Mid-project keys (red lines) are perpendicular to high flow & connect the tie-back or LPSTP to the bank (the rest of the world) Key designs for continuous bank protection.

  15. 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 from Vicksburg Corps District : max. bank height plus max. scour depth = key root length

  16. 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)!!

  17. 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

  18. 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).

  19. Longitudinal Peaked Stone Toe Protection Upstream key Inner bank Flow Downstream key All of the green lines delineate rows of adventitious live poles (willow, dogwood, etc.), planted deep & dense (typically 3 poles per linear ft.) 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 Live Pole Planting Layout for all Keys.

  20. 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, it gets expensive when you do that !!

  21. 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 Key angle High flow angle

  22. Looking US. Hoe placing big stone (NYS DOT heavy) in US keyway. Medium & small stone will be added as a choke. Pix by Derrick

  23. 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

  24. Harvesting Pole-sized Adventitious Rooting Material for the Key

  25. Matt Horvat with safety glasses & ear plugs cutting willows with chainsaw CONSTRUCTION-TOLEDO OHIO PROJECTS. PIX BY KRIS PATTERSON 8-2008

  26. Renewable resource-willow will grow back multi-stem after cutting CONSTRUCTION-TOLEDO OHIO PROJECTS. PIX BY KRIS PATTERSON 8-2008

  27. Poles ready to have leaves & side branches removed. CONSTRUCTION-TOLEDO OHIO PROJECTS. PIX BY KRIS PATTERSON 8-2008

  28. Teen volunteers cutting side branches & leaves from poles CONSTRUCTION-TOLEDO OHIO PROJECTS. PIX BY KRIS PATTERSON 8-2008

  29. 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

  30. 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

  31. Dump truck load level full of Sandbar & Streamco Willow, & Ruby Red osier dogwood, (1,500 poles total). Pix by Derrick


  33. A MID-PROJECT LIVING KEY ON CHENUNDA CREEK Vegetated & soil-choked stone key is perpendicular to high flow (& the bank)

  34. Detail for key Cross-section for keyway Flow

  35. Detail for key Flow Place granular filter if not using a self-filtering stone

  36. 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).

  37. Construction 9/19/2006. Digging a mid-project key perpendicular to the bank. Some veg (willow poles) in place Pix by Derrick

  38. Detail for key Place soil to cover at least the butt ends of the poles Flow

  39. Place stone in trench Detail for key Flow

  40. Construction 9/19/2006. Looking @ key. Butt ends of willow & dogwood poles down deep. Some large stone placed, needs choke stone. Pix by Derrick

  41. Choke stone with gravel-cobble (white areas) & water in Detail for key Flow

  42. Backfill and overfill with native soils, then compact (some settling will still occur) Detail for key Flow

  43. Construction 9/21/2006. Key stone is now soil-gravel choked. Pix by Derrick

  44. Detail for key Seed Flow DONE

  45. 13 MONTHS LATER-low flow. Veg in key is robust. Pix by Derrick 10/15/2007

  46. 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

  47. VEGETATION IN KEY ACTING AS A LIVING DIKE ON ONONDAGA CREEK (Veg oriented perpendicular to high flow)

  48. Looking toward stream. Key vegetation is 4 ft deep. Key stone buried to right of veg. Onondaga Creek @ Nichol Road Bridge, LaFayette, NY – project planted 5-15-2007 Pix by Derrick

  49. July 10, 2008. {middle of second growing season} Key vegetation is over 7 ft tall. Willow & dogwood. Will act as a Living Dike. Onondaga Creek-Year 2 Pix by Derrick

  50. 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