A retention basin or pond retains water without any initial release during inflow. Another advantage of the detention basin is the positive means of outflow, resulting in fewer problems with long-term ponding. Because of its ability to release flow during inflow, the overall volume of storage required for a given storm event is reduced. A detention basin or pond detains water temporarily, releasing water through a pipe or channel by means of a weir, orifice, or pump. The words “pond” and “basin” are used interchangeably when used in connection with both detention and retention reservoirs. Stormwater storage reservoir types are numerous, but they essentially fit into one of two categories: detention or retention. It is important that any extended detention (retention) be supported by valid water rights that allows for retention without impacting any vested water rights on the stream system. Policy regarding detention and extended detention (retention) is found in GJMC 28.16.090 and 28.16.100. Regional and local detention facilities are more fully discussed below. Use of detention includes local detention such as in-channel or within a parking lot, and regional detention, such as a large recreational lake or reservoir and off-line detention facilities. Detention has been shown to be very beneficial in controlling flood peaks in an urbanized area. This controlled discharge rate is based on either limited downstream capacity (regional and local facilities) or on a limit on the increase in flows over predevelopment conditions (local facilities only). The main purpose of a detention basin is to store runoff and reduce peak discharge by allowing flow to be discharged later at a controlled rate, and within a reasonable time. 28.56.050 Drainage fee in lieu of detention.Ģ8.56.080 Detention for management of stormwater quality.Ģ8.56.130 Calculating storage volume available.Ģ8.56.210 Hydrologic design methods and criteria.Ģ8.56.240 Compensating detention analysis.Ģ8.56.260 Hydraulic design of outlet works.
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