The digital computer program based on water balance methods and known as the Stanford Watershed Model was used to develop a long-term continuous hydrograph (1905-1963) for Morrison Creek, Sacramento County, California. By varying constants describing the physical conditions within the watershed according to the amount of urban development and channel improvement within the tributary area, a number of continuous hydrographs were developed. A set of curves was developed from these hydrographs that made possible an estimate of flood peak by frequency for any combination of percentage of area urbanized, percentage of channels improved, and tributary area. An analysis was also made of the effects of urban development on runoff volumes and on the distribution of runoff during the year. graphs on a digital computer, Tech. Rept. 36, Dept. Civil Eng. Sta•ford Univ., 1964. Crawford, N.H., and R. K. Linsley, The synthesis of continuous streamflow hydrographs on a digital computer, Tech. Rept. 12, Dept. Civil Eng. Stanford Univ., 1962. James, L. D., A time-dependent planning process for combining structural measures, land use, and flood proofing to minimize the economic cost of floods, Rept. EEP-12, Inst. Eng.-Econ. Systems, Stanford Uni•., 1964.

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Least squares can be used for estimating constants in a linear recession model from published average daily streamflows. A model with two recession constants was derived and successfully tested on a number of Kentucky streams. It can be used to estimate recession constants from daily streamflows stored on magnetic tape or punched cards without resorting to time‐consuming graphical techniques. Equations and procedures are provided for recessions represented by either one or two recession constants using both a weighted and unweighted estimation procedure. In applying the two techniques, empirical evidence indicates the simpler unweighted procedure is preferable.

A digital computer program was developed for determining the optimum combination of structural and nonstructural measures for flood control according to the criterion of economic efficiency. The program may be readily applied by any agency interested in analyzing the relative merits of structural and nonstructural measures or in more rapid economic analysis of alternative channel improvement designs. It selects the optimum combination of channel improvement, flood proofing, and land use control for each portion of the flood plain during planning stages of specified duration. The program was used to relate the optimum combination of the three measures to specific flood-plain properties. Finally, the sensitivity of the nature and the total cost of the optimum program was related for various flood-plain conditions to variation in cost of channel improvement, cost of land use control, cost of flood proofing, right-of-way value, value of the coefficient relating flood damage to flood severity, value of open space preserved in an urban area, extent of aversion to irregular timing of flood damage, discount rate, population projections, and the exclusion of alternative combinations. (Key words: Flood control; flood plains; flood proofing; land use control) INTRODUCTIOl• Whenever heavy rains or melting snow cause streamflow to exceed channel capacity, the adjacent land is inundated. A flood is nature's use of this land as a reserve waterway. However, by virtue of their fertility, flatness, and relative nearness to transportation facilities, flood plains are also used for agriculture and urban development. Men may occupy the flood plain, but nature exacts a tax in flood damage. The tax has three distinct characteristics: