Mining Gravel and Protecting Streams
flood plain, at least do it in ways that will not damage your property or your neighbor's property.
Without a doubt, the worst damage caused by gravel mining is the extensive erosion that results when the mining operation makes the slope of the stream channel steeper than it was before mining. When a stream channel is made steeper, the water flows faster; and the faster it flows, the more power it has to cause erosion. In these situations, the bottom of the stream channel erodes away first, and then the stream banks fall in and wash away.
If the gravel mine is a pit dug in the stream channel and the miner continues to take gravel over a long period of time, the erosion can move far upstream and cause extensive property damage to many streamside landowners. Because of these potential problems, gravel should never be mined deeper than the water elevation at the time of removal. If the stream channel is dry, mining should not be deeper than the elevation of the stream bottom at the site. If you don't mine too deep, the natural slope of the channel will not steepen, and the risk of serious erosion damage to neighbors will be reduced.
Gravel should never be removed from riffles because breaking up the riffle threatens channel stability and important habitats for fish and other aquatic life.
Gravel miners need to get their equipment through the stream corridor and into the stream channel, but the wooded corridor along the stream protects the waterways and, itself, needs to be protected. This forested area slows erosion, filters excess nutrients and sediments, baffles powerful flood flows and provides important habitat for aquatic and terrestrial plants and animals. It also protects the waterway from our other activities in the flood plain and watershed and keeps stream temperatures cooler with its shade.
When mining gravel, maintain an undisturbed buffer at least 50 feet wide at the top of the high bank and that extends for the length of the excavation site. Construct access points from the high bank into the channel to minimize erosion of both the access road and stream banks. Make sure you replant areas disturbed for access once excavation is complete.
It's also important to leave a 20-foot wide buffer from which mining equipment is restricted between the mined area and stream bank vegetation. Keeping mining equipment out of this area assures that the stream will