Runoff Pond Information Page

In natural areas, rain can soak into the ground. But in urban areas, pavement and roads keep this from happening. Instead, water is collected by storm sewers and directed to creeks and streams. It may carry lots of sediment with it that can harm water quality. To solve this problem, whenever new construction takes place, contractors often must include plans for a wet pond, also called a sediment pond. [This is especially important the construction will impervious material, such as asphalt or concrete, replacing natural vegetation.] So you will often see a wet pond next to a large parking lot or a new housing development. In a parking lot, rain will wash oil from cars down to the wet pond.

Wet ponds hold runoff water from storms, but the ponds always have some water. Sediment and other pollutants settle out of the water so that when water is discharged from the pond, it does not carry these materials into a stream. Wet ponds usually contain vegetation so that the plants roots may hold the sediment and use the nutrients that are often contained in urban runoff. The ponds can also mitigate flooding in the event of a major storm and thus control impact downstream. Many of the lakes in developments are actually detention or retention wet ponds which developers have designed to look like natural bodies of water. If they are properly constructed and maintained, such ponds can be extremely effective in removing sediment and in reducing nutrients.