A significant concern in any developed area is stormwater runoff impact of the nearby waterbodies. Along roadways and parking lots, runoff is often channeled into drains and pipes, which often outlet into a stream or a lake. Impervious surfaces such as roads, rooftops and asphalt parking areas do not allow water from precipitation or snowmelt to infiltrate into the ground. As the water flows across these impervious surfaces, it can collect sediment, phosphorus, de-icing materials (sand and salt), petrochemicals and other pollutants.
Roadside ditches also contribute to stormwater runoff issues when improperly installed or poorly maintained. A poor roadside ditch can contribute to increased stormwater runoff velocity leading to increased erosion and sedimentation. During warmer months, runoff can also be significantly warmer than the stream’s water, causing thermal pollution affecting the stream’s aquatic communities.
These stormwater discharges are a major contributor to sedimentation/delta formation issues in the lake, and can also have significant negative impacts to a stream’s aquatic community.
Calcium from road salt (if calcium chloride is used as a de-icing agent) can create habitats at the mouths of streams suitable towards zebra mussel colonization. Phosphorus transportation by sediments may create multiple problems including the eutrophication of waterbodies, causing reductions in water quality and habitat for aquatic plants and animals.
As land gets developed, typically more water runs off the land into nearby streams, often very quickly following a precipitation event. This large volume of water entering a stream in a short period of time can cause an overwidening of the stream channel in order to accommodate the increased volume of water. These channel widening processes occur through accelerated streambank erosion, and ultimately more downstream deposition (deltas).