In most locations across North Carolina, a stream’s natural defense against bank erosion is vegetation. No wonder sediment is the largest type of pollution coming from urbanized areas. This erosion creates a new and much larger source of sediment, which is transported downstream. Increased runoff volume also results in increased velocity within the stream, which increases the potential for erosion of the banks and deepening of the channel. This fluctuation can saturate and loosen soil on the stream banks. Increased runoff causes the height of water in urban streams to often rise and fall more quickly during and after rainfalls. Annual rainfall in the piedmont of North Carolina is over 45 inches, with greater amounts in other areas of the state. In a 1-inch rainfall, a one-acre parking lot could produce as much as 27,000 gallons of runoff flowing to local streams. In these areas, there is less water soaking into the ground and more stormwater flowing directly to our streams. We have more homes, commercial buildings, parking lots, and roads, but fewer natural landscapes to slow down rainwater runoff. If you have also wondered why your stream bank seems to be changing rapidly, it is likely tied to the fact that North Carolina is urbanizing. Perhaps the stream is widening, threatening your property, buildings, or a road. Are storms causing chunks of land to erode from a stream on your property? Maybe the stream has started cutting deeper into the channel, creating more of a gully.
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