The Bitterroot River - protecting the river, fish habitat and homes - Part One: projects

Rip-rap on a faliing bank of the BItterroot
Photo by Merle Ann Loman

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Rip-rap series index

• Introduction and index
  You are reading Part One - projects

• Part Two: basic information about permitting
  

• Part Three: public comment and questions
  

• Part Four: some things you can do
  

• Slideshow of related photos

The four bank stabilization (rip-rap) installations sites discussed in this article are in various stages. The first two are in progress and fairly new in design and construction. The third is similar to the first two except it is not a high bank -- it is a long flat flood plain area. It was constructed last summer and the vegetation has yet to fill in. The fourth installation site is of "old-time" design and has been completed for about a year and a half. All of the stabilization projects are being done to protect the landowners’ assets.

The purpose of the first two installation sites is to protect the landowners’ houses along the banks of the ever changing Bitterroot River. The houses were built on very high banks-- you might call them cliffs – and are in danger of falling into the river. The loose gravels and soils that make up much of these banks are being rapidly eroded causing severe slough-off of rock and gravels and all kinds of plant material including large trees. The scope of these installations is quite large and requires a significant amount of rock, wood debris and gravel to be displaced from one area of the flood plain and then replaced at the bottom of the erosion (toe of the stream bank) in an effort to prevent water from eating away these unstable banks. A backhoe is used to move the material, reduce the steepness of the bank and build up a “flood plain” area that will include vegetation. Small dikes are built just inside the waters’ edge to “break or brake” the energy of the river as it moves down the bank. Both installations are pro-active in reestablishing native, healthy vegetation along the waters’ edge. There is a natural fabric-like material securing live plant material and cuttings such as trimmed cottonwood, willow, aspen and grasses. Stout stakes and some rock help hold the fabric in place. The hope is that the roots will grow deep and securely hold the bank thereby reducing erosion. The test of whether or not these projects will be successful, only time will tell.

The third installation site, Double Fork Ranch, was a bank stabilization using rock and wood as fill, topping with finer material, adding riparian plant stock and grasses, laying the fabric-like material and securing with stakes. The bank is along a fairly flat field or flood plain. No buildings were threatened. See photos in the slideshow.

The fourth installation site, Krengel, looked and was “old-time” bank stabilization. In an attempt to protect the real estate, they used massive amounts of very large rock. There was no fine material added and no native vegetation had been planted or encouraged. The most significant vegetation was an invasive weed, mullein http://en.wikipedia.org/wiki/Mullein which does not have enough of a root system to keep soil in place when erosion takes place. This project was permitted for less than 100 feet of bank stabilization and the final project resulted in at least 500 feet of “rock armored bank.”

Merle’s SmugMug photo site – More river and rip-rap in their original format/resolution. Incudes photos of four rip-rap installations and portions of the middle Bitterroot River.

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