Off-Stream Detention Design for Storm-Water Management
AbstractA detention basin is designed for storm-water quantity and quality controls. An in-stream basin is often located on a widened floodplain, whereas an off-stream basin can be part of open space in a parking lot, park, or sport field. The inflow channel associated with an off-stream basin is allowed to carry its base flow not to exceed the downstream capacity. When the inflow channel is full, the excess flood water is diverted into the off-stream basin through the side weir. During the flood recession, the equalizer conduit drains the basin flow back to the channel. In this study, the rational volumetric method was expanded from in-stream to off-stream detention design. The required off-stream detention volume is maximized by the rainfall event longer than the time of concentration of the tributary area. In comparison, the off-stream detention volume can be significantly less than an in-stream, depending on the flow-through capacity in the downstream channel. This paper presents a design procedure to...
DETENTION BASIN SIZING FOR SMALL URBAN CATCHMENTS
The Federal Aviation Administration (FAA) method for sizing small detention and retention basins is a volume-based approach that is sensitive to the release rate. In practice, such a release rate is often approximated by open channel hydraulics or culvert hydraulics. Without a consistent guideline, this practice of approximation can result in significant discrepancy or violation of the volume balance between the inflow and outflow hydrographs. In this study, a consistent procedure was developed to derive the average release from the allowable peak outflow. The required parameters for this method include peak inflow, design storm duration, and the time of concentration of the watershed. With this modification, the detention storage volume maximized by the FAA method can satisfy the volume conservation between hydrographs.
An Approximate Method for Sizing Detention Reservoirs
ABSTRACT: The detention reservoir is an effective measure for the management of storm water runoff, but random or unplanned placement may aggravate potential flood hazards. An approximate method for the sizing and placement of detention reservoirs is presented. The procedure is based upon the application of a storage estimation equation. The results show that the procedure closely approximates the results produced by the U.S. Army Corps of Engineers HEC-1 Flood Hydrograph Package in computing reservoir capacities on a hypotehtical watershed. Pending further tests, the use of the procedure is very limited, but it is an initial step to incorporating detention storage into regional storm water management plans.