The Public Works Department provides many services related to Boise's quantity and quality of water including both flood response and drainage control.
Flooding in the City of Boise typically comes from one of two different sources:flash floodingfrom a heavy rainfall event in the Boise foothills orflooding of the Boise River. The Department's goal is to help safeguard homes and businesses by maintaining flood control structures and by working with other agencies to monitor Boise River flows.
To protect against flash flooding, the City operates and maintains several flood control structures on each of the four main foothills gulches (Stuart Gulch, Crane Gulch, Hulls Gulch and Cottonwood Creek). Most of these structures were either installed or upgraded following a major wildfire in the fall of 1996. While these facilities provide vastly improved flood protection, these will not completely protect property in an extreme flooding event.
To control Boise River flooding, the City of Boise works with the Bureau of Reclamation and the U.S. Corps of Engineers to control water flows from three dams upstream of the Boise River drainage. The dams provide irrigation water storage and flood control. Late spring is a critical time of the year for flooding. The agencies must balance the need for water storage and space reserves based upon snow pack levels, historic runoff records of snow pack, and reservoir level conditions.
The responsibility for drainage control of stormwater runoff within Boise is dispersed among several agencies. Street drainage and street drains are the responsibility of the Ada County Highway District (ACHD). Many areas of the city use flood irrigation. In those cases, responsibility for drainage lies with one of several irrigation or drainage districts or local water users associations within the city limits.
The City of Boise Public Works operates and maintains the conveyance systems for stream flows from the four main gulches in the Boise Foothills: Cottonwood Creek, Hulls Gulch, Crane Creek, and Sand Creek. The City also handles commercial development drainage plan review to ensure that storm water runoff from business sites is disposed of in an environmentally sound manner.