Periodic Master Plan Updates are required by law to account for changes in land use and the construction of new flood control facilities. Project prioritization Regional Flood Control District staff work with local governments to prioritize flood control projects in each jurisdiction according to set criteria. Typical flood control projects include detention basins, channels and storm drains. A detention basin temporarily detains storm water runoff and releases it at a greatly reduced rate over an extended period of time. The basins span several acres, some covering more than 100 acres, with depths up to 60 feet.
Channels are open canals that convey floodwater through the valley.
Some of the channels pass floodwaters between 25 and 40 miles per hour. Storm drains are conduits that convey floodwater safely underground. Storm drains are constructed of reinforced concrete pipes or box structures. These concrete pipes often range up to 8-10 feet in diameter. When larger conveyance systems are needed, multiple concrete boxes, measuring up to 18 x 8 feet, may be used.