Friends of the Cacapon

Riverbanks - How to Stabilize and Repair Them

 


Riverbanks - How to Stabilize and Repair Them


A major key to protect your river property is to maintain, stabilize, and repair your riverbank. This river edge is the bulwark that holds in the soil and prevents your property from washing away. It is an essential part of the whole ecosystem.

If your riverbank has been scoured bare of vegetation by floods or drifting ice packs and dislodged debris floating down the river, you are causing problems to yourself and to the river. The worst problem for the river in the lower reaches of the Cacapon is sediment dis­persing and settling of small particles of soil washing from your banks and settling into the river, smothering spawn­ing beds of fish, killing aquatic organisms, and ruining good water quality.

What are the causes of your bank erosion?

•Determining why your stream or river bank is in a dis­tressed condition of erosion or of collapsing, is an essential step in your plan of action. Here are some causes of stream bank deterioration:

•Mowing grasses at the edge of your bank; cutting down trees, or removing other vegetation.

•Permitting intense running games such as volleyball or soccer—activities that compact the soil and destroy plants.

•Allowing cattle to trample the banks as they seek water.

•Improper bulldozing a cut in the bank to provide a boat access or using heavy machinery to cut steps down to the river.

•Parking cars and trucks too close to top of the bank.

•Permitting all terrain vehicles (ATVs) to tear up the bank.

•And of course, heavy flooding, floating ice or uprooted trees and debris that scour your banks.

Stabilize your riverbank

Vegetation is an excellent bank stabilizer, and you should make every effort to keep existing trees, shrubs, flowers, and grasses intact. These plants hold the soil in place with their root structures, as well as provide shade and habitat for fish and wildlife.

If your bank is in good condition, maintain it and for­tify it by planting patches of low-growing groundcover plants such as wild strawberry, cinquefoil, gill-over-the ground and native clovers; or taller plants such as jewelweed and milkweed; native shrubs such as buttonbush and pussy willow; understory trees such as pawpaw, redbud, and dogwood; and canopy trees such as river wil­low, river birch, sycamore, oak.

 

Repair patches of your bank

After a storm or flood, check your bank to see if you have any eroded spots that need repair. Review the damage to determine which technique will work best. Some methods maintain the qualities of a natural setting; oth­ers will need more complex preparation and advice from riverbank experts. Before any heavy stream bank or chan­nel work can be started, you must contact the Division of Natural Resources and obtain both a Federal 404 per­mit from the Army Corps of Engineers and a State 401 permit.

•Grasses. You may want to repair the bare spots as fast as possible. For rapid but temporary repair of minor eroding patches, plant fast-growing grasses such as Ken­tucky fescue, switch grass and bluestem. These grasses quickly develop a root system that can hold in the soil until you can plant sturdier kinds of plants or take more complex repair measures.

• Live tree stakes. Living woody cuttings river trees such as willows or alders are capable of quickly taking root along your stream bank. They require minimum ef­fort to set out, and are most useful on stream banks of moderate slope and where erosion is light. The cuttings, about 2 to 2 1/2 inches long, and '1/2 to 1 in diameter, should be fresh and have at least two bud scars near the top for sprouting branches. They must be kept moist in a shaded area and placed in the soil within 24 hours of being cut. Use an iron bar to poke a hole in the bank and gently tamp in the cut branches, with bud scars at top, at right angles to the slope.

•Straw matting. Temporary repair can be achieved by covering the bare bank spots with commercial straw matting, held in place with lightweight netting that degrades over time in sunlight. Heavier netting maintains better erosion control with prominent ridges that trap sediment from the river and provide a base for plants to take root. Another option is to put down a cellulose mix matting impregnated with seeds that germinate and hold down the soil.

 

For more serious and heavier repair work:

•Live fascines (bundles of live branches) Living fascines are sausage-like bundles of live branch cuttings of fast-growing river trees like river birch. Cut them about 15 to 20 inches long, and wire them together in bundles 6 to 8 inches in diameter. Place them in shallow trenches you have scooped out in rows ascending the eroded bank. Then hammer living stakes through them, and cover them all with soil. Twigs from the living fascines should pro­trude above the soil. These fascines collect sediment and are very effective stabilization installation once rooting is established. They should be installed during the dor­mant season (November to March).

•Branch packings. Alternating layers of live willow branches and soil can be incorporated into a washed-out scoured stream bank. You can place them even where the water is running fast and moderately deep. Branches above the waterline take root to form a permanent in­stallation while those below the waterline provide initial stability. Considerable labor is required for this work, but the installation produces an immediate barrier, redi­recting the flow of water away from the scoured-out area.

•Live cribwall. This "crib" is a rectangular framework of logs, rocks, and woody cuttings that can protect an eroding stream bank, especially along the outside bends of main channels where river currents are running strong. The log framework provides immediate protection from erosion and as the woody cuttings grow, the installation achieves a natural appearance.

•Stones for heavier repair.

 

•Dry stone walls. Dry stone walls can be built by hand on vertical banks where space is limited. These walls are best as structural protection for steep eroding banks along small to medium sized streams near buildings, bridges, or roads. Extensive hard labor and skill is required.

 

•Stone riprap. This is a bank of carefully placed loose rocks along the banks of a stream. Unlike stone walls, riprap covers the banks with layers of stone at an angle that follows the natural slope of the stream bank. Place about 6 inches of stone and gravel over the eroded bank, and over this carefully place layers of stone by hand. The total thickness of the stones should be at least two feet, and extend at least 12 inches below the low water level. To ensure more durable installation, place willow cut­tings or seedlings into the joints above the water line. Use an iron bar to force a space between the rocks, fill in with soil and the cuttings. Cuttings should be placed during the dormant season (November to March); seed­lings may be planted in early spring or late fall.

 

• Gabions. For seriously eroded banks, you may want to consider gabions. A gabion is a squarish chickenwire or hogwire basket, usually 3 by 3 by 3 feet, or bigger, filled with broken or crushed stones. A series of these gabions can be banked and linked together to form a flexible permeable structure that protects the bank from further erosion, especially caused by floods. As river sediments become caught in the interstices between the stones, enough soil collects to sustain vegetation.