Flood Mitigation Function and its Stochastic Evaluation of the Matsuzawa-ike Pond, Osaka Prefecture, Japan

Evaluation of Flood Mitigation Function of Irrigation Ponds

Abstract

For the evaluation of flood mitigation function of irrigation ponds, this paper analyses the performance of the Matsuzawa-ike pond, with its catchment area of 1.13km², during flood time, based on the records of water level in the pond and rainfall. It also gives a stochastic analysis, based on simulation using probable rainfalls at different levels and runoff model, on flood mitigation and its effect on flooding in the downstream of the pond. It clarifies; 1) the pond has decreased flood peaks by 37-98% in its overflow, for 4 cases of high flood with the maximum 10-minute rainfall intensity of 10mm and more, 2) the percentage of the mitigation is strongly influenced by the vacancy of storage capacity at the beginning of flood, 3) flood mitigation ratio in the floods with the return period of 5-200 years ranges 37 to 43% of the peak inflow, even under the condition of full water level at the beginning of flood, 4) the pond has the effect to reduce the frequency of inundation in the downstream from more than once in every year to once in 2 years