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This pre print has been provided for the purpose of convenient distribution of information at the convention. To defray, in part, the cost of printing, a convention price of 501 to all registrants has been established. The past-convention price, when ordered from ASCE head- quarters will be 50~ while the supply lasts. Far bulk orders (of not less than 200 copies of one pre print) please write for prices. No acceptance or endorsement by the American Society of Civil Engineers is implied; the Society is not responsible for any statement made or opinion expressed in its publications. Reprints may be made on condition that the full title, name of author, and date of preprinting by the Society are given. - L... tlV'" ~ '-0.\.1..1 AN APPROXIMATE METHOD FOR QUICK FLOOD PlAIN HAPPING ~ By Roy F. powell, I A. M. ASCE, L. Douglas James, and D. Earl Jones, Jr., 3 F. ASCE 2 M. ASeE, Introduction The flood insurance and flood plain management program in the United States is in dire need of mapped hazard information on flood plain areas. Flood plain mapping is being accelerated by additional funding to meet this need, but the process is slow and costly. This paper presents a quick, low-cost, but approximate method that can be used for rough mapping before more detailed studies are completed or in locations where more costly atudies cannot be justified. The map- ping can then be used for interim land use regulation before the de- tailed studies are completed or on a long-term basis in areas of scattered development. The method utilizes the concept that the magni- tude of floods of more ordinary frequency can be estimated more precisely than can the magnitudes of the floods of the rarer frequencies (usually the lOO-year) used for flood plain regulations to develop normalized curves for estimation of flows or stages of large floods from flows or stages of smaller ones. Flooding is popularly associated with major rivers where large areas are inundated during a flood; however, isolated floods on small streams cause much of the nation's annual flood damages. Flood hazard information is needed along these sm~ller streams as well as the larger ones for flood plain management to be effective in reducing future flood losses. The omission of flood plains along smaller streams or streams located in rural or undeveloped areas from flood plain mapping promote5 the !Civil Engineer, U. S. Army Corps of Engineers, Mobile, District, Mobile, AL 2prof., Environmental Resources Ctr., Georgia lnst. of Tech., Atlanta, GA 3Arlington. VA