This seemingly benign substance can be a potent killer, capable of clogging the gills of aquatic animals, smothering fish fry, mussels, and aquatic insects, reducing concentrations of oxygen in streams, transporting toxic chemicals into lakes and rivers, and destroying essential habitats for numerous species. Twenty-six years after passage of the Clean Water Act, sediment pollution remains the primary cause of stream degradation in North Carolina. Today, more than 3,000 miles of streams in the state are polluted by sediment. The leading causes of sediment pollution are agriculture, municipal development, logging, and mining. The report offers a set of recommendations that include both regulatory and nonregulatory tools to address the problem.
Agriculture generates sediment pollution in several ways.
Plowing exposes the soil and increases its susceptibility to erosion, while drainage ditches facilitate the movement of dirt-laden runoff into streams and rivers. Clearing the natural vegetation along a streamside can lead to streambank destabilization and severe erosion. Cattle can also destroy vegetation along streambanks, leading to erosion. In the case of Christmas tree farming, soil erosion can occur during site preparation, when the ground is disturbed prior to planting the seedlings, or during harvest, when the trees are cut and removed, The construction of roads to access Christmas tree farms also contributes to soil erosion. Municipal development leads to sediment pollution by increasing the amount of paved or impervious surfaces, such as roads and parking lots, in a watershed.