Stormwater management pond
||It has been suggested that this article be merged into Retention basin. (Discuss) Proposed since February 2013.|
|This article does not cite any references or sources. (November 2008)|
A stormwater management pond is an artificial pond that is designed to collect and retain urban stormwater. They are frequently built into urban areas in North America to also retain sediments and other materials.
In urban areas, impervious surfaces (roofs, roads) reduce the time spent by rainfall before entering into the stormwater drainage system. If left unchecked, this will cause widespread flooding downstream. The function of a stormwater pond is to contain this surge and release it slowly. This slow release mitigates the size and intensity of storm-induced flooding on downstream receiving waters. Stormwater ponds also collect suspended sediments, which are often found in high concentrations in stormwater water due to upstream construction and sand applications to roadways.
At its simplest, a stormwater pond can be constructed by creating a dam across a drain or stream at a convenient valley, with a restricted diameter outlet pipe through the dam. Normal flows are carried through the pipe, but heavy flows back up and the water behind the dam is choked back. Over the following few days, the level subsides. If the lake fills to capacity, then it will begin to spill over. This is often enough for a small housing development.
For aesthetic and safety reasons, the system can be designed so that there is a permanent lake. A lake with an equivalent area of 1000 by 1000 metres rises by one metre will hold a million cubic metres of water. Typically such a lake would have an outer earth bank of 1 metre, then a leisure path, then a 10 cm inner bank to the steady state level.