Sediment entering stormwater degrades the quality of water for drinking, wildlife and the land surrounding streams in the following ways:

• Sediment fills up storm drains and catch basins to carry water away from roads and homes, which increases the potential for flooding.
• Water polluted with sediment becomes cloudy, preventing animals from seeing food.
• Murky water prevents natural vegetation from growing in water.
• Sediment in stream beds disrupts the natural food chain by destroying the habitat where the smallest stream organisms live and causing massive declines in fish populations.
• Sediment increases the cost of treating drinking water and can result in odor and taste problems.
• Sediment can clog fish gills, reducing resistence to disease, lowering growth rates, and affecting fish egg and larvae development.
• Nutrients transported by sediment can activate blue-green algae that release toxins and can make swimmers sick.
• Sediment deposits in rivers can alter the flow of water and reduce water depth, which makes navigation and recreational use more difficult

Source: Environmental Protection Agency