The Corps of Engineers held a meeting recently in Livingston, Mont. to solicit public comment on a special area management plan for the Upper Yellowstone River. An important item the Corps may consider for the Yellowstone is changing its guidelines on the use of hard armor riprap to stabilize banks and prevent flooding.
Since 1995 our firm, Trout Headwaters, Inc. (THI), located south ofLivingston, Mont., has worked to develop, refine and advocate the use ofsustainable, natural, vegetative approaches to stream bank stabilization andrestoration. During that time we have installed "soft," vegetative bankstabilization and restoration treatments along the Yellowstone's banks andhave closely monitored those installations. THI has also worked under aCooperative Research Agreement (CRADA) with two U.S. Corps of Engineers ERDClabs in Vicksburg, Miss., to further refine and test different vegetativetreatments for stream bank stabilization and restoration. Among the thingswe've learned, as a result of our training, experience and practice over thelast 12 years in the Yellowstone drainage and elsewhere, is that we can getthe same performance out of reinforced vegetation as 40-inch rock riprap.Not only do carefully designed and installed vegetative treatments work,they cost less andcanbring all the ecological benefits of a naturallyrestored riparian buffer.
While hard armor can provide localized erosion control, evidence is mountingthat its use causes undesirable consequences to fish and wildlife habitatand to the long-term health of our river ecosystems. What's happened in thelast 10 years on the Yellowstone is a common scenario. When stream banks andriparian vegetation suffer as a result of humanimpacts, the lack of native,woody vegetation to hold soil causes accelerated rates of erosion. Concernsabout loss of property or damaged buildings prompt calls for immediateaction. The action most frequently taken is to slope back the eroding banksand then armor them in place with riprap. It's an expensive solution botheconomically and environmentally.
As expensive hard materials are installed, the energy of the water from oneriprapped bank is deflected and displaced to another place on the stream,causing a domino effect as the trend to riprap rolls downstream. Rockbegets more rock as landowners and municipalities try desperately to holdonto eroding soils. The cumulative result is a laterally-constrained riverrobbed of its floodplain and unable to maintain the fluvial processes thatare essential to maintaining a dynamic and healthy river ecosystem. As morevegetation is replaced with rock, floodwaters rush over banks prompting theneed for additional flood-retaining levees.
In contrast, free-flowing rivers maintain natural flow regimes, which cuecertain spawning, nesting, feeding, and migration behaviors for fish andwildlife. Certain plant species, such as cottonwoods, depend on the scourand deposition of floodwaters to create suitable germination sites. Naturalfloodplains and riparian areas with healthy vegetation are able to absorbthe force and volume of floodwaters by storing water and slowly releasing itback into the system. At the same time, plants filter water by trappingsediment and absorbing pollutants and excess nutrients, improving waterquality. Deep-rooted woody plants anchor soil, preventing bank erosion whileoverhanging branches shade the banks reducing water temperatures. Colderwater holds more life-giving oxygen. Leaves from plants are broken down byaquatic insects which, in turn, provide food for fish and other wildlife.Wild rivers provide critical habitat. Studies show that 80 percent of allwildlife species depend in some way upon riparian zones. Besides providingwater, healthy riparian zones provide shelter, food, shade, and migrationcorridors for wildlife. Migrating birds use riparian areas as stopoverareas, often following river corridors hundreds of miles.
THI encourages a Corps of Engineers plan for the Upper Yellowstonethatrestrictsthe use of concrete structures, boulders and other hard treatmentsfor the purposes of erosion control, bank stabilization and riverrestoration. We suggest that the Corpsencouragebank stabilization andrestoration activities that usenative vegetation and biodegradable,naturalmaterialsto stabilize soils and re-establish important riparianvegetation. We applaud the Corps' leadership in requesting input ona matterthat affects one of the nation'smost preciousrivers.
Jim Muth is Director of Operations for Trout Headwaters, Inc., (THI) anaquatic design/build firm based in Livingston, Mont. Muth has beenaffiliated with THI for ten years, and has served in a full-time capacitywith both operations and project management since 2003. With a lifelongappreciation for trout streams, trout habitat and water quality, Muth hasinvolved himself in trout conservation-related organizations for nearly 20years.