Flooding of the river in downtown Napa during winter storms has been common since the town was first established . Records dating from 1862 describe twenty-seven significant flooding events . Following studies made by the United States Department of the Interior in the late 1930s and early 1940s , the United States Congress authorized channel improvements on the course of the Napa River and construction of a dam on Conn Creek as part of the Flood Control Act of 1944 , however funding for the projects was never approved . The City of Napa funded and built the dam in order to create the water conservation reservoir Lake Hennessey in 1948 , however flooding continued to be a problem . A large flood in February 1986 revived public interest in finding a remedy . After a traditional plan to widen the river channel proposed by the United States Army Corps of Engineers was presented in 1995 and roundly rejected , a group of special interests called Friends of the River formed . From January 1996 until May 1997 , this coalition representing business , agricultural and environmental concerns met and achieved a consensus on a " living river " plan . Voters in the County of Napa narrowly approved an increase of .5 percent of the sales tax in a March 1998 election to fund the Napa River Flood Project . Although revenues from the increased sales tax have outpaced expectations , the project has progressed slowly . Current projections show the remaining phases of the project being completed in 2015 . On December 31 , 2005 , the Napa River again overflowed and flooded the entire downtown area and thousands of acres all over Napa County . More than 4,000 residents were evacuated and 1,000 homes were flooded or destroyed . The 2005 flood was the 23rd most serious flood of the Napa River on record since 1865 . The restoration of the Napa River has been accompanied by returning fish and wildlife to the area , such as the native beaver
flood in February 1986
Napa River flood of 1986
Napa, California