Can This Stream Be Saved?
N.C. Cooperative Extension
Area Specialized Agent, Water Resources
If you have a stream on your property in or near an urban area the odds are the stream is under stress. Urban areas have a lot of paved, built-upon, or impervious areas that prevent rain water from infiltrating the soil. When rain water fails to infiltrate it runs off and creates minor or major flash floods every time it rains. In nature, streams have lots of trees and shrubs on their banks and the streams are able to overflow their banks. When heavy rainfall enters a natural stream the water overflows the banks and enters the stream’s flood plain, where the water spreads out and slows down. Streams and rivers are supposed to come out of their banks during flood events. Flood plains are supposed to be flooded. But what happens when humans decide to build in a flood plain or they decide to ‘beautify’ the stream in their back yard by cutting down all the trees and shrubs and planting grass along the stream bank?
This stream has been straightened out and the banks have been sprayed with a herbicide to kill all vegetation. Shallow rooted grass has been planted on the land adjacent to the stream. Notice how the banks are collapsing in to the water.
In the past, when streams flooded the approach was to dig the stream or river deeper and build levees or dikes along the banks to keep the water in the stream. While this approach does provide some protection for the area alongside the banks, it also causes the water in the stream to concentrate in power and quantity and to actually cause more flooding and erosion downstream. In the stream pictured above, the banks will continue to cave in, and because the stream has been straightened, the water will cut deeper with each flood, and the banks will continue to cave in. Natural streams and rivers almost never flow in straight lines. The curves and meanders in natural streams serve to slow the speed and destructive power of flowing water and create habitat for fish and other animals. The stream pictured has undergone a total stream restoration since this photo was taken. In a total restoration, the stream banks are graded down and planted with trees and shrubs so the water can spread out into the flood plain during floods. Curves or meanders are re-created in the stream to slow the water down, and logs and large rocks are placed in the stream bed to slow the water down and to create habitat for fish and other aquatic animals.
Total stream restoration is expensive, but it is possible to perform minor repairs on eroding stream banks to prevent further damage and to protect the property of adjoining landowners. Before any work can be done on a stream it is necessary to check with the N.C. Division of Water Resources and the U.S. Army Corps of Engineers to make sure the work is legal and to check to see if any permits are needed. Streams in the Neuse and Tar River basins have 50 foot stream side buffers that are protected by law, so it is much better to seek permission to work on a stream than to do some work and find that you have violated the law.
Pictured above is a small stream bank repair being carried out on a stream in Raleigh. After checking with the N.C. Division of Water Resources to determine that a permit was not required for this project, the group graded the eroded stream bank to a 3:1 slope using picks and shovels. In the photo, coir erosion control matting is being installed over the bare soil on the stream bank. In the rear of the photo, note the short ‘sticks’ lying on the matting. These are live stakes – 18 inch sections of dormant live trees and shrubs which will be driven into the steam bank through the matting. The live stakes will form roots and sprout in the spring and form a dense cover of native trees and shrubs that can withstand heavy flooding and protect the stream bank and the land adjoining the stream.