Flood management practice in northern California

This paper describes flood management practices in northern California and how operations are adjusted to fit the seasonal flood threat. The risk of a large flood is seasonal; the region is most vulnerable during the November through March rainy season. Rivers can rise from low flow levels to damaging floods within one to three days. Some measure of the size of the threat can be gained from the design flow of the lower Sacramento River floodway system, which is 17 300 m3 s−1. Flood management strategy in California is a multipronged approach, depending on the area and the local geography. One element is designating areas or zones subject to flooding and restricting development therein. Another important element consists of physical works, levees, floodways, and flood storage behind dams in foothill reservoirs. Flood warning, including flood forecasts and notification of people at risk, is part of the strategy, as well as providing technical advice and assistance in flood fighting once high water arrives.