Tree Revetments

Tree revetments are cut increase bank erosion. It trees anchored at the bottom is extremely important (or toe) of unstable stream- to anchor each tree in the banks. These anchored trees revetment at the base or toe serve to slow the current of the eroding bank. This is along the bank, decreasing the point of the bank where erosion and allowing the vertical bank meets the sediment to be deposited horizontal bottom (Figure 2). within the tree branches. If the trees are anchored too Trees with many fine limbs high on the bank, the water and branches are best at may undercut the structure. slowing near-bank currents, If they are placed out in the catching sediment carried channel too far, the current in the stream, and catching Figure 1. Cedar revetment and willow stakes after 3 months. will continue to erode the slump material from the bank. bank behind the revetment. example of this would be stream For this reason, eastern redcedar Another consideration is the soil straightening (or channelization). is usually the best choice. Eastern type and texture that the anchors One indication of this situation redcedar is also more resistant to will be driven into. Sandy or rocky is when a streambank is covered decay than hardwood trees. soils will usually require a larger with trees and vegetation and is The sediment trapped in and anchor driven to a greater depth still eroding. If that is the case, behind revetments provides a while smaller anchors may be a tree revetment may not work. moist, fertile seedbed for vegetation used in heavier clay soils. The four Characteristics such as stream size, establishment. The primary purpose typical anchor types are arrowhead bank height, and flow fluctuations of a revetment is to stabilize the anchors, duckbill anchors, disc should be considered when deciding bank until trees and shrubs become anchors, and steel fenceposts. if a revetment is an appropriate established to provide permanent Since every stream is unique, practice for your site. Single-row protection (Figure 1). consult a natural resource profes- tree revetments may not be effective on extremely Designing a Tree high banks or on large $FEBS
5SFF Revetment river systems. The majority of tree revetments Tree revetments should are installed on the outside bends begin and end at points on of small to medium streams that the streambank that are $BCMF
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#BOL Some streambanks become length of an eroding bank, unstable because of past alterations the structure may be Figure 2. Cross section of tree revetment showing cedar placement of the toe of the bank. to the channel or watershed. A good ineffective and possibly Kansas Forest Service sional to determine if a tree into the toe of the bank revetment is the appropriate solution where the top portion of the to the problem. Before doing any first tree will be located. work in a stream, contact the U.S. Roll the tree into the stream Army Corps of Engineers and the and position it at the toe of Kansas Division of Water Resources the bank. While holding to see if a permit is required. the tree tightly against the bank, attach the cable to Installing a Tree the top of the tree using a Revetment cable clamp. Mark the bank Revetments can be installed where the second anchor Figure 3. Design plan for revetment with willow during any season, but late winter will be placed to hold the cuttings and a riparian buffer. and early spring are usually the best butt end and drive in the Over time, the vertical bank will times. Cedar trees placed in early anchor. Reposition the butt end of attain a more gradual slope as it summer can dry out and lose their the tree tightly against the bank and slumps and the slump material is needles before being flooded. They attach it to the anchor. Anchoring caught and held by the revetment. are most effective at trapping silt and the trees tightly against the bank This is an essential step in the sand if flooded while still green and is crucial. Move the next tree into establishment of vegetation and succulent. Timing is not so important place with its top overlapping the long-term stability. You can aid the when hardwood trees are used. Larger butt of the first tree, making sure revegetation process by planting trees are usually your best choice to not leave any gaps between the trees and shrubs and placing willow for revetments, because they will trees. Secure the cable used to stakes on the streambank (Figure 3). protect more of the bank. Cedar trees anchor the butt of the first tree to For additional information on tree 15 to 20 feet tall are an excellent the top of the second tree. Drive revetments, cost-share opportunities choice for revetments. Remember and attach a new anchor at the butt or technical assistance, contact the that a revetment should not make the end of the second tree. Continue the Kansas Forest Service, your local stream channel significantly narrower. process upstream until the entire conservation district office, K-State Generally, a revetment won’t cause bank is covered with trees. Research and Extension office, problems if all trees are anchored After construction of the tree Natural Resources Conservation tightly against the eroding bank. revetment, make a visual inspection Service office, or the Kansas Begin construction of the to make sure no gaps are left Department of Wildlife and Parks. revetment at the downstream end of between trees or between the trees the eroding streambank. Place the and the bank. Fill gaps with small References first tree at the top of the eroding cedar trees cabled to the larger ones Tree Revetments for Streambank already in place. Inspect revetments Stabilization. Missouri Department of bank, with the cut end of the tree Conservation. pointing upstream. Drive the anchor, after floods and repair any breaks with about 12 feet of cable attached, before the breaks become larger. Deborah Goard Kansas Forest Service The Kansas Department of Health and 2610 Claflin Road Environment has provided financial Manhattan, KS 66502-2798 assistance to this project through EPA (785) 532-3300 Section 319 Nonpoint Source Pollution www.kansasforests.org Control Grant #C9007405 11. Brand names appearing in this publication are for product identification purposes only. No endorsement is intended, nor is criticism implied of similar products not mentioned. Publications from Kansas State University are available on the World Wide Web at: www.oznet.ksu.edu Contents of this publication may be freely reproduced for educational purposes. All other rights reserved. In each case, credit Deborah Goard, Riparian Forest Best Management Practices: Tree Revetments, Kansas State University, August 2006. Kansas State University Agricultural Experiment Station and Cooperative Extension Service MF-2750 August 2006 K-State Research and Extension is an equal opportunity provider and employer. Issued in furtherance of Cooperative Extension Work, Acts of May 8 and June 30, 1914, as amended. Kansas State University, County Extension Councils, Extension Districts, and United States Department of Agriculture Cooperating, Fred A. Cholick, Director.