Extention and Application of the Theory of Equi-Risk Line

分析了调蓄设施的防洪效能，指出当同时使用排洪和调蓄设施时，必须根据洪水的“洪峰流量“和“总径流量“的联合频率分布来评估防洪系统的洪水风险或频率，利用联合频率分布，本文导出了以排水能力和蓄水能力为横轴、纵轴的平面上洪水频率等值线的表达式设施。这个等高线被称为“等风险线”。理论分析的结果被应用于日本大坂和东京现有和计划中的蓄水池的防洪风险评估。然后，提出了城市化流域非点源污染物控制的另一种理论。有几种可供选择的方案来减少暴雨产生的非点源污染物的体积，点污染物径流到湖泊和池塘。最有效的方法之一是将洪水径流暂时储存在储存设施中，在没有降水的时期进行处理并将其释放到自然沃茨。储存-处理系统的效率通常通过模拟径流，储存，以实测降雨序列为输入，对蓄能处理系统的效率进行了研究，提出了蓄能处理系统效率的简单表达式，该表达式包含了反映流域气象特征、径流特征和设施处理能力的参数，利用AMeDAS，计算表达式中气象参数的值，并在日本地图上用等高线显示。

The efficiency of storages for flood control is analyzed.When both drainage and storage facilities are used,the risk or frequency of flooding in a flood control system must be evaluated based on the joint frequency distribution of the"peak discharge"and the"total runoff"of a flood.Using the joint frequency distribution,the autors derived an expression of the contour of frequency of flooding on a plane on which the lateral and vertical axes respectively represent capacities of a drainage and a storage facilities.This contour is called the"equi-risk line".The results of the theoretical analysis are being applied to risk evaluation in flood control,by existing and planned storages in Osaka and Tokyo,Japan.Then,another theory was presented for non-point pollutant control in urbanized basings.There are several alternative plans to reduce the volume of storm-generated non-point pollutant runoff to lakes and ponds.One of the most effective is to store flood runoff temporarily in storage facilities,and treat and release it to natural waters during periods of no precipitation.The efficiency of storage-treatment systems is usually evaluated by simulations of runoff,storage,and treatment processes with observed rainfall sequences as inputs.The authors presented a simple expression of efficiency of these storage treatment systems.These expressions have some parameters,which represent meteorological and runoff characteristics of a basin,and capacities of the facilities.Using AMeDAS,the values of the meteorological parameters in the expressions are calculated,and displayed on the maps of Japan with contour lines.