Advancements in stormwater management and geomorphology suggest that regional detention offers numerous flood control and water quality benefits. Many local municipalities require on-site detention to reduce the impacts of downstream flooding which can result from the increase in impervious surfaces associated with commercial and residential site development. Based on numerous design parameters, on-site detention captures a predetermined quantity of water, and releases the volume over a designated period to storm systems in the immediate area. The basins can be a dry-design, where the entire volume is released for discharge, or of the wet-type, where a base level of water is retained in the designed structure. Wet structures are often utilized as an aquatic enhancement to the designated development.
Regional detention facilities are often located adjacent to moderate sized streams within the 2-year design floodplain. The detention basin creates a large footprint of shallow water, dissipating flood energies while contributing to sustainable stream stability. Dependent upon available acreage and watershed size, regional detention can capture and detain extremely large storm volumes, even in excess of the 100-year design storm. In some applications, storm flow is piped direct to the detention facility. In other applications, grass lined retention swales are connected to wetland forebays, which release water into the regional basin. Numerous alternatives can be proposed based on site specific limitations.
Most regional detention facilities are also designed to create water quality benefits. The use of wetland species of grasses, wildflowers, trees and shrubs recreates valuable habitat, biodiversity, and a sustainable biotic mechanism to utilize excessive nutrient loads commonly found in association with land development. Trails and park amenities are often constructed in conjunction with wetland enhancement.
Project Examples
Rodrock Lake Detention Project, South Johnson County, Kansas
Plum Creek Stormwater Improvements Project, St. Peters, Missouri |
