How the Flood Project Protects the Community from Flooding
Flood control projects usually seek to impound water through the use of dams; increase the capacity of river channels by dredging, widening, or both; and contain high water with levees and floodwalls. The "Living River" design of the Napa Project is a new approach to Flood Control. Rather than using earlier methods that often diminished the character of natural waterways, the Napa River design maintains the natural channel depth and slope.
By employing riverbank terracing techniques, flood flows are given more room to spread horizontally into defined areas. A large area of pastureland at the downstream end of the project was purchased and returned to a wetland environment. This space is capable of holding substantial amounts of excess water. Replacing a number of old bridges that have been determined to block flows is another key ingredient of the plan. And the dry bypass channel for the oxbow area allows a shortcut for fast-moving water that historically has resisted the sharp turns required by the natural geography. The bypass will come into use only when waters rise to flood stage, keeping the oxbow of the River connected to the main channel, and preserving the habitat there. Low flood walls and levees are also required to achieve protection from the "100-year flood".