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I , In 1997, flood walers overpowered levees on the San Joaquin, Cosufllnes, Feather, Bear and Yuba rivers, and the Sutter B.vpa.\'s, causin!: nearf.v $2 hillion in damage. 1 As towns, cities and farms grew up along the water- ways of California, the need for flood management became imperative. These rivers and streams had the power to destroy as well as nurture, In a region where earthquakes usually grab the headlines, 90 percent of all natural disasters in the state are flood related, During heavy rains, large rivers as well as smaller streams and creeks can become dangerous. In 1955, floods in northern and central California killed 67 people and caused $166 million in damage, In 1964, a savage storm struck the North Coast of California. The Eel River roared out of the mountains carrying 750,000 cubic feet per second (cfs) - average flow is 7,200 cfs - and 24 people were killed, The 1964 event was only one in a series of floods that occurred throughout the state, Property damage claims from the 1986 floods, which devastated much of central California, exceeded $1.5 billion and 14 people lost their lives, In January and March 1995, Sacramento Valley, North Coast and Central Coast creeks and rivers, and Los Angeles' flood control channels were flooded by torrential rainfall. Two years later, 48 of the state's 58 counties were declared disaster areas after the 1997 New Year's subtropical storms hit. Flood waters overpowered levees on the San Joaquin, Cosumnes, Feather, Bear and Yuba rivers and the Sutter Bypass, killing eight people, forcing the evacuation of 120,000 people and caus- ing nearly $2 billion in damage, In February 1998, there were problems with local flooding, Floods occur in the West nearly every year because of the region's diverse microclimates and geogra- phy, Attempting to control these otten devastating floods can be a daunting task. The engineering challenges alone are awesome. As Mark Twain wrote more than 100 years ago, "You cannot bar a river's path with an obstruction which it will not tear down, dance over and laugh at." Most efforts at flood management are inextricably intertwined with politics, economics and values. Historic floodplains in the West have been heavily developed for agricultural, commercial and residen- tial use, When the projects were developed, neither society nor the law dictated that the impacts on fish and wildlife, or the ramifications of developing and altering floodplains be considered, Because ot the large public-borne costs, floods affect every Californian. Yet evaluating the state's needs and managing its water supply and flood control system is highly complex. The state fluctuates between having too much or not enough water, A delicate balance between flood control and water supply operations must be struck, In addition, riparian habitat and fish and wildlife impacts must be factored into the flood management equation, Adding to the complexity is the fact that the responsibility for flood management is spread throughout a wide range of federal, state and local entities. i The purpose of flood management is 10 prevent the loss of life and minimize property damage, Two approaches are used: structural and nonstructural. The structural approach uses dams, reservoirs, levees and bypass channels to confine and direct flood flows away from people and property, Historically, it has been the preferred method of controlling flood problems in urbanized floodplains, The nonstructural method applies floodplain management principles to prevent the need for such structures. It includes mapping historic flood- plains and limiting land development within them. It also may include the intentional flooding of low-lying areas to relieve pressure - reduce the velocity and quantity of flow - farther down the waterway. A 1994 interagency report com- missioned by President Clinton examined the 1993 Mississippi floods, which caused 48 deaths and cost more than $15 billion, and recommended changing current flood management policies to reduce development in floodplains, including relocating residents from low-lying areas (see page 12), Since the 1997 New Year's floods, California's policy-makers have been debating whether limits on floodplain development or new storage projects - or a combination of both - is the optimal way to minimize flood damage. Using nonstructural measures in urbanized floodplains, however, is highly controversial and costly. This Layperson's Guide, part of a continuing series published by the Water Education Foundation, describes some major issues in flood management, explains how and why flood control projects are operated the way they are, and how the various agencies involved coordinate and share costs.