Extention and Application of the Theory of Equi-Risk Line

对水库防洪效能进行了分析。当排水和蓄水设施同时使用时，防洪系统的洪灾风险或频率必须根据洪水“洪峰流量”和“总径流”的联合频率分布进行评估。利用联合频率分布，作者推导出平面上洪水频率等值线的表达式，该等值线分别代表排水设施和蓄水设施的能力。这条等高线被称为“等风险线”。理论分析的结果被应用于防洪风险评价，大阪和东京的现有和规划中的水库。然后，对于城市化流域的面源污染物控制提出了另一种理论。有几种减少暴雨产生的面源污染物向湖泊和池塘的径流量的替代方案。最有效的方案之一是将洪水径流暂时存储在蓄水设施中，并在非降雨期将其处理并释放到自然水域。蓄水处理系统的效率通常是以观测的降雨序列为输入通过模拟径流、蓄水和处理过程来评估的。作者给出了这些蓄水处理系统的效率的简单表达式。这些表达式具有一些代表流域气象和径流特征的参数，利用AMeDAS计算公式中的气象参数值，并用等高线显示在日本地图上。

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.