The authors illustrate how various flood control measures can be analyzed using the HEC-5C computer program. Basic principles in flood control planning and damage reduction are examined. Flood plain management measures include those designed to control hydrology and those designed to reduced susceptibility of property to damage. Hydrologic and economic relationships are examined and the affects of different types of flood control measures are presented. Of the eight control methods, levees or floodwalls were found to affect the stream's stage-discharge, stage-damage, discharge-damage, and damage frequency relationships. Diversion and flood forecasting affected these relationships the least, but all the methods affected the damage frequency. The HEC-5C program was used to develop systems which maximize net economic benefits. Given an existing system and an array of flood control measures, the strategy proceeds by computing expected annual damages for the existing system; adding any one of the flood control measures and computing expected annual damages; then subtracting expected annual damages with or without the control measure. Finally, the best measure was chosen based upon its final net benefit yield. A final added strategy recomputed costs and benefits by removing one of the control measures to determine if a better net benefit figure would be yielded. The Fall River System of California was used to illustrate how the program functions. (Author).

The goals of nonstructural flood-control planning are formulation, evaluation, selection, and implementation of a practicable management plan that provides optimal protection from the adverse effects of flooding. Many alternative flood-control measures can be dismissed by the water resources planner on the basis of judgement, but a substantial number will require detailed analysis before a suitable plan can be selected. This analysis is an iterative process, requiring input from the planar at each step. Software developed at the Hydrologic Engineering Center (HEC) allows efficient data storage in a structure-oriented data bank and provides for selective retrieval and manipulation of the data from an interactive terminal. Thus the planner is able to propose nonstructural measures and to evaluate rapidly the economic and technical feasibility of those measures in a iterative scheme that allows the required input from the planner. An application of the interactive plan evaluation software is presented. Steps in creating the data bank are defined, and use of the software for subsequent accessing and manipulating the data for plan evaluation is discussed. (Author).