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MF2294 Streambank Revetment

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MF2294 Streambank Revetment Outdated Publication, for historical use. CAUTION: Recommendations in this publication may be obsolete. Kansas State University Agricultural Experiment Station and Cooperative Extension Service Kansas State University, Division of Biology Kansas Cooperative Fish and Wildlife Research Unit U.S. Environmental Protection Agency Kansas Department of Wildlife & Parks STREAMBANK REVETMENT 1 Outdated Publication, for historical use. CAUTION: Recommendations in this publication may be obsolete. Introduction Streambank erosion is a naturally occurring process in streams and rivers throughout the United States. Accelerated streambank erosion occurs when natural events or human activities cause a higher than expected amount of erosion, and is typically a result of reduced or eliminated riparian (streamside) vegetation. The removal of riparian vegetation is the primary factor influenc- ing streambank stability. Historically, channel straightening (channelization) was the primary method used to control streambank erosion. However, since the 1970s, riparian and in-stream habitat restoration by natural or artificial meth- ods has grown in popularity because channel- ization typically caused problems, such as ero- sion and flooding dowstream. Natural resource agencies throughout the Midwest have been using tree revetments as one type of streambank stabilization structure. What are tree revetments? Tree revetments are a series of trees laid in the stream along the eroding bank. They are de- signed to reduce water velocity, increase siltation within the trees, and reduce slumping of the streambank. Tree revetments are not designed to permanently stabilize eroding streambanks. They should stabilize the streambank until other stabi- lization techniques, such as tree plantings in the riparian area become established. Tree revet- ments are not designed to fix problems at a watershed level. Tree revetments should only be used if good land management practices are applied in the watershed, for example fencing riparian areas from cattle use, maintaining buffer strips between streams and row crops, or terrac- ing highly erodible row-crop fields. 2 Outdated Publication, for historical use. CAUTION: Recommendations in this publication may be obsolete. How are tree revetments constructed? Tree revetments are constructed by anchoring finely branched trees, like eastern red cedar at the bottom of an unstable streambank. Installation starts at the downstream end of the eroded bank—at a point where the bank is stable. Each tree is placed into the stream with the cut end pointing upstream. Trees are overlapped approxi- mately one-third and are anchored twice using a Duck- bill Anchor. Construction continues until the entire eroded surface is covered and the tree revetment is secured at a stable point upstream. What did this research document? KINGS CREEK 18 The purpose of this research was to determine 16 Sample in 1994 prior to tree revetment installation at tree revetment locations. what effects tree revetments had on erosion and 14 Sample in 1996 deposition within a stream, and how these pro- 12 cesses influenced stream fishes and aquatic 10 insects. The study was conducted on Kings Creek 8 6 (Riley County) and West Creek (Greenwood 4 County), Kansas from 1994 through 1996. Revet- 2 ment sites were chosen in conjunction with the HEIGHT OF STREAMBANK (FEET) 0 0 10203040506070 Kansas Forest Service, Kansas State University DISTANCE (FEET) Agricultural Experiment Station and Cooperative Extension Service and Kansas Department of ■ The control sites all had well-developed Wildlife and Parks. Each revetment site was riparian corridors, as shown in the photo compared to two control sites, one upstream and above. There was little change in the one downstream from the tree revetment loca- channel cross-section at the controls sites tion. While the controls had similar cross-sections from 1994 to 1996, as shown by the to the tree revetment sites, they were different representative cross-section in the graph. because they had well-developed riparian corri- dors. Therefore, if similar results were found among the controls and tree revetment sites, it was concluded that the tree revetments were functioning similar to a stable streambank with a well-developed riparian corridor. 3 Outdated Publication, for historical use. CAUTION: Recommendations in this publication may be obsolete. WEST CREEK (PRE-TREE REVETMENT INSTALLATION) WEST CREEK 30 30 Pre-Tree Revetment (Winter ‘94) 25 25 Post-Tree Revetment (Spring ‘96) 20 20 15 15 Tree Revetment 10 10 5 5 HEIGHT OF STREAMBANK (FEET) HEIGHT OF STREAMBANK (FEET) 0 0 0 102030405060 0 102030405060 DISTANCE (FEET) DISTANCE (FEET) ■ The tree revetment sites lacked a riparian ■ After tree revetment installation, banks corridor and had accelerated erosion became more gradual and the main problems, as shown in the photo above. channel of the stream was moved away The corresponding graph shows the from the eroding bank, protecting the eroding outside bend at 26 feet in height. streambank from excessive erosion. The corresponding graph illustrates how the slope of the eroding streambank decreased, and how silt increased within the tree revetment. 4 Outdated Publication, for historical use. CAUTION: Recommendations in this publication may be obsolete. KINGS CREEK Downstream Control 15 Tree Revetment Upstream Control 12 9 6 3 NUMBER OF FISH SPECIES 0 WINTER ‘94 SPRING ‘95 SUMMER ‘95 FALL ‘95 SPRING ‘96 PRE TREE REVETMENT POST TREE REVETMENT SAMPLES SAMPLE WEST CREEK Downstream Control 25 Tree Revetment Upstream Control 20 15 10 5 NUMBER OF FISH SPECIES 0 WINTER ‘94 SPRING ‘95 SUMMER ‘95 SPRING ‘96 PRE TREE REVETMENT POST TREE REVETMENT SAMPLES SAMPLE ■ The number of fish species present at ■ Central stoneroller (top photo) were the Kings Creek and West Creek was not most abundant fish present in Kings related to the establishment of the tree Creek. Central stonerollers are common in revetments. This is evident by the lack of streams through eastern Kansas. Central a distinct pattern in number of fish stonerollers feed primarily on algae and species present among the controls and micro-organisms associated with the tree revetment location. streambottom. Central stonerollers only get 6 to 8 inches long. ■ Orangespotted sunfish were the most abundant fish present in West Creek. Orangespotted sunfish are in the same family of fish as bluegill and crappie, and usually feed on small aquatic insects and other fish. Orangespotted sunfish do not grow much larger than 6 inches. 5 Outdated Publication, for historical use. CAUTION: Recommendations in this publication may be obsolete. KINGS CREEK Downstream Control WEST CREEK Downstream Control 35 Tree Revetment 10 Tree Revetment Upstream Control Upstream Control 30 8 25 6 20 15 4 10 2 5 CATCH OF CENTRAL STONEROLLERS 0 CATCH OF ORANGESPOTTED SUNFISH 0 WINTER ‘94 SPRING ‘95 SUMMER ‘95 FALL ‘95 SPRING ‘96 WINTER ‘94 SPRING ‘95 SUMMER ‘95 SPRING ‘96 PRE TREE PRE TREE REVETMENT POST TREE REVETMENT SAMPLES REVETMENT POST TREE REVETMENT SAMPLES SAMPLE SAMPLE KINGS CREEK Downstream Control WEST CREEK Downstream Control Tree Revetment Tree Revetment Upstream Control Upstream Control 3.0 2.0 2.5 1.5 2.0 1.5 1.0 1.0 0.5 0.5 0.0 0.0 WINTER ‘94 SPRING ‘95 SUMMER ‘95 FALL ‘95 SPRING ‘96 WINTER ‘94 SPRING ‘95 SUMMER ‘95 SPRING ‘96 PRE TREE PRE TREE AVERAGE LENGTH (IN.) OF CENTRAL STONEROLLERS REVETMENT POST TREE REVETMENT SAMPLES REVETMENT POST TREE REVETMENT SAMPLES SAMPLE AVERAGE LENGTH (IN.) OF ORANGESPOTTED SUNFISH SAMPLE ■ Catch of central stoneroller declined ■ Catch of orangespotted sunfish declined slightly after installation of the tree at all locations after installation of the revetment at the tree revetment and tree revetment. Similar to catch of central upstream control locations. Thus, it is stonerollers in Kings Creek, catch of likely that catch of central stonerollers orangespotted sunfish was not influenced was influenced by a factor other than the by the tree revetment. Average length of tree revetment. Average length of central orangespotted sunfish remained similar at stonerollers remained similar at all all locations before and after installation of locations before and after installation of the tree revetment. the tree revetment. 6 Outdated Publication, for historical use. CAUTION: Recommendations in this publication may be obsolete. KINGS CREEK Downstream Control KINGS CREEK Downstream Control 0.8 Tree Revetment 2.0 Tree Revetment Upstream Control Upstream Control 0.7 0.6 1.5 0.5 0.4 1.0 0.3 SILTATION (OZ.) 0.2 0.5 0.1 0.0 0.0 DIVERSITY INDEX FOR AQUATIC INSECTS WINTER ‘94 SPRING ‘95 SUMMER ‘95 FALL ‘95 SPRING ‘96 WINTER ‘94 SPRING ‘95 SUMMER ‘95 FALL ‘95 SPRING ‘96 PRE TREE PRE TREE REVETMENT POST TREE REVETMENT SAMPLES REVETMENT POST TREE REVETMENT SAMPLES SAMPLE SAMPLE WEST CREEK Downstream Control WEST CREEK Downstream Control Tree Revetment Tree Revetment Upstream Control Upstream Control 0.8 1.0 0.7 0.8 0.6 0.5 0.6 0.4 0.3 0.4 0.2 SILTATION (OZ.) 0.2 0.1 0.0 0.0 DIVERSITY INDEX FOR AQUATIC INSECTS WINTER ‘94 SPRING ‘95 SUMMER ‘95 SPRING ‘96 WINTER ‘94 SPRING ‘95 SUMMER ‘95 SPRING ‘96 PRE TREE PRE TREE REVETMENT POST TREE REVETMENT SAMPLES REVETMENT POST TREE REVETMENT SAMPLES SAMPLE SAMPLE ■ Diversity of aquatic insects was variable ■ The amount of siltation within Kings in Kings Creek and West Creek, but was Creek (left) was generally lower at all not related to the tree revetment. Overall, locations after installation of the tree the tree revetments had no effect on the revetment. Conversely, siltation increased diversity of aquatic insects present. in West Creek at the tree revetment location after installation. This is likely caused by the tree revetments trapping sediment. Sediment trapping did not occur on Kings Creek because the tree revetment was slightly above the water level during normal flow. 7 Outdated Publication, for historical use. CAUTION: Recommendations in this publication may be obsolete. Summary Will tree revetments stop erosion? Yes, results from this study have shown that localized streambank Control locations had well-established riparian corridors and erosion can be reduced by tree revetments.
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