A secondary problem is the relationship between stormwater runoff and sediment. As you may know, sediment is the greatest pollution problem in the world's waterways. Sediment entering the larger waterways causes filtration problems in hydro-electric turbines which help create the electricity we need, creates an added cost in producing drinking water, and in some cases, acts as a substrate for various bacterial species which have been known to cause disease in man. Sediment buildup in lakes and ponds, which act as impoundments for drinking water, decreases their capacity of these impoundment to hold water. This sediment buildup also decreases the available habitat for a variety of aquatic species which require clear streams, gravel beds, and little if any sediment deposits for their survival.
Flooding is also an issue.
Direct stormwater runoff can cause downstream flooding and streambank erosion. Water flooding basements, businesses, and property, including the loss of property due to erosion, could be, under certain conditions, a financial disaster for a property owner. In an undeveloped area, approximately 10 percent of rainwater discharges directly into streams, rivers, creeks, lakes, and oceans. The remaining 90 percent either evaporates or filters into the groundwater. Again, the more impervious surfaces in an area increases the direct runoff and decreases the percentage of water re-entering the ground water supply.