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001155 PART I: FLOODS AND FLOODPLAIN MANAGEMENT Introduction Flood losses in the United States aver- age more than $3.5 billion per year ac- cording to the U.S. Water Resources Council. Much of this damage is occur- ring along small to medium-sized streams, particularly in urbanizing metropolitan areas such as Houston, Tulsa, Chicago, St. Paul/Minneapolis, Washington, D.C., Phoenix, and so on. These smaller streams typically have few or no federal flood control works such as dams, reservoirs, and large-scale channelizing. Instead, their flood management is in the hands of countless decision-makers-private owners, public authorities, and various levels of government-who independ- ently "control" a small segment of the total watershed and floodplain of the stream in question. Each of these decision-makers, acting alone, attempts to maximize benefits to itself from de- velopment and use of its floodplains. At the same time, each may try to avoid the penalty of flooding through improvised filling, flood walls, and other means- which, however, often result in increased flood problems for neighboring areas. In summary, small stream management is a crazy quilt of conflicting policies, hap- hazard attempts to deflect floodwaters, and ultimately an overall increase in flooding and flood losses. In 1978, a team of researchers under the direction of Dr. Rutherford Platt of the University of Massachusetts con- ducted a national study to assess the ex- tent of this fragmentation of floodplain management authority and to identify means for achieving better intergovern- mental coordination. That study was sponsored by the U.S. Anny Corps of Engineers' Office of Floodplain Manage- ment Services, and it was published in 1980 under the title Intergovernmental Management of Floodplains by the Insti- tute of Behavioral Science, University of Colorado at Boulder. The present docu- ment is a condensed version of the earlier study and has been prepared under con- tract with the Federal Emergency Man- agement Agency (Training and Educa- tion) for use in short courses and train- ing sessions on natural hazard mitigation. Case studies were originally prepared by Mary Read English, Michael Grahek, George M. McMullen, Richard Paton, and Ann Patton. Ms. English provided re-write and editorial assistance. Graphics were prepared by William Nechamen, Barbara Rosander, and Katherine Price. The manuscript was typed by Judith Stark. This report is limited to consideration of floods, primarily in the context of small urbanizing watersheds. Large rivers and coastal areas are not considered here, due to their different physical and political circumstances. The various floodplain management arrangements de- scribed here, however, may well be gen- erally applicable in other situations in- volving the need for cooperation and consistency among governmental units which confront a common peril. I. THE FLOOD PROBLEM IN THE UNITED STATES Public knowledge of floods-their causes and effects-is minimal. Some people believe that the problem was solved long ago by the Anny Corps of Engineers or other federal agencies. Others believe that a "1 DO-year flood" can only happen once every hundred years. Residents of coastal barrier islands sometimes view tropical hurricanes as occasions for parties. Few people realize urbanization in the upstream portions of a small watershed can increase the depth, extent, and rapidity of flooding of downstream areas-that property never before known to flood may be inundated due to changes in upstream land use pat- terns. This short document cannot supply detailed treatment of all these topics. However, as an introduction for readers with no prior knowledge of floods, the report's first section will briefly review a flood's geographical aspects. We will then consider in more detail its governmental aspects: how floodplain management by multiple governments can work in theory and in practice. 1