FLOOD DAMAGE REDUCTION BY STREAM NETWORK CONTROL.

摘要

In the past, flood protection programs concentrated on structural measures such as dams and reservoirs. In 1979, the U.S. Water Resources Council revised the "Principles and Standards" that changed the basic structure of the planning process to insure the preparation and display of a "primary nonstructural plan". While this is only a guideline, it shows the increase in interest in nonstructural water measures.This research concentrates on minimizing the cost of flood damage reduction measures, both structural and nonstructural, and on environmental quality problems based on sediment control criteria as an indicator of environmental quality. The scope is limited to plan formulation with the objective of flood damage reduction by utilizing two criteria: total cost and erosion control effectiveness.In finding the optimum mix of flood damage reduction measures, reservoirs were chosen to represent structural measures watershed management was chosen to represent nonstructural measures.Two sets of reservoirs were used in this research: the first was at every stream order junction, and the second was at points immediately upstream from the flood areas. Four cases of sediment control practices were used for watershed management.The acceleration of population growth, urbanization, and industrial expansion which began in the 1940s caused dramatic increases in environmental problems. Quality control became the most important feature of water resources management during the 1970s.The results show that after applying watershed management above the reservoirs, both sets of reservoirs were able to limit peak discharge at flood damage areas to less than channel maximum carrying capacity and the reservoir cost reductions was a function of land use changes.All four cases of sediment control practices can reduce sediment loads drastically. The percentage of reduction depends upon the practices and land use changes. Even though there are a lot of controversy about soil conservation and tillage practices. The cost of sediment control practices varied according to the practices used.The significance of the research is a demonstration of how multiobjective planning techniques can be combined with computer-based analysis to generate cost-effective flood control strategies that are environmentally responsible.