Capturing runoff in reservoirs or basins is one of the most direct methods of flood control. In urban locations, these consist of relatively small detention ponds. While green infrastructure can significantly decrease urban flooding, where new flood control detention projects are planned and existing projects exist, they can be designed to provide multiple functions in addition to a primary flood control purpose. These additional functions can include designing projects to maximize groundwater recharge, storage of other types of water such as effluent, and to provide recreational opportunities. Multi-purpose facilities can be planned to transform what is typically a purely functional structure into an important community amenity.
Indian Bend Wash in Scottsdale, Arizona is a well-known example of an “alternative” flood control project that uses a greenbelt design rather than a channelized structure to manage stormwater. The result is an 11-mile long greenbelt with parks, playing fields, and other recreational opportunities. The project dates to the 1980s and is an innovative alternative to a cement-lined channel. Because residents opposed a tax increase to acquire lands, the City asked landowners in the wash for flood easements and shaped the wash so it could function as a flood-control channel. Although this is a very large, older project, it illustrates how flood flow can be managed through appropriate design to provide multiple community benefits.
The Kino Environmental Restoration Project (KERP) in Tucson was originally designed as a flood control detention basin. It was a bare, flat-bottomed pit that collected runoff from a diversion channel. Funding from the Pima County Regional Flood Control District and the U.S. Army Corps of Engineers allowed the detention basin to be redesigned to continue as a flood control structure while also being developed as a park with educational and recreational components, and as a showcase of the natural desert environment and Arizona’s desert riparian systems.
KERP was not designed as a recharge facility; instead, stormwater is harvested to maintain desert riparian features (ponds, wetlands and mesquite bosque), and stormwater is used for irrigation water of adjacent ball fields at the Kino Sports Complex and nearby landscaped areas at institutional facilities. Treated effluent is used to supplement irrigation needs when stormwater is unavailable.
Using harvested stormwater for irrigation of the ball fields and landscaping, instead of high-cost potable or reclaimed water, results in significant cost savings for the City, which in turn has offset the construction costs of KERP. The park also includes two miles of trails and picnic areas, and provides wildlife viewing opportunities including bird watching.
KERP continues to function as an effective flood control structure designed to reduce the peak flow of a 100-year storm. Since its construction, it has harvested over 41 million gallons of water a year, about 126 acre-feet. It is also an important recreational and aesthetic amenity for the community: numerous professional sporting events occur at the Kino Sports Complex; it functions as a location for hosted birding trips; and its trails link to a regional trail system.
Model Multi-purpose Project
Pima County Regional Flood Control District
Information about Indian Bend Wash can be found here.