Shuichi Kure

A STUDY ON NEW DETEMINATION METHOD OF DAM RESERVOIR DISCHARGE FOR FLOOD CONTROL CAPACITY IMPROVEMENT OF EXISTING DAM RESERVOIR

A new method of flood control by gate operation based on runoff characteristics of a basin is proposed in this paper. This method is based on an anticipatory release approach and the idea that there is no risk in reducing reservoir levels if the amount of anticipatory release is equal to the amount of inflow which will flow into the dam for certain from the rainfall that has already fallen. In this method, rainfall prediction or weather forecasting will not be necessary for flood control. The amount of anticipatory release will be calculated by the real time inflow into the reservoir or accumulated rainfall. And reservoir levels will certainly be restored to there former condition, because the amount of discharge is based on the area under the recession part of the hydrograph.

STUDIES ON TEMPORAL CHARACTERISTICS OF RAINFALL

The purpose of this study is to elucidate temporal characteristics of rainfall intensity averaged at different time intervals. Using AMeDAS 10min rainfall product, the features of 10min and 1h rainfalls on Kanto area were examined. It was found out that, on average, the maximum rainfall intensities of 10min series are between 1.5 to 2.0 times of the corresponding 1h rainfall amount. The frequency distributions of 10min rainfall intensity in each 1h intensity range could be modeled as a gamma distribution. The properties of thunderstorm and non-thunderstorm rainfall were compared in plain and mountainous areas. For thunderstorm-rainfalls, the higher 1h rainfalls in plain areas are characterized by larger 10min intensities compared with those of mountainous areas. The non-thunderstorm rainfall does not show such a difference.