Abstract
This paper deals with an economic assessment value on time and regional extended effects by a flood mitigation project to give more value than those, which have been calculated with a standard method in feasibility study. The time extended effect is an integrated benefit accumulated capital by flood mitigation infrastructure for long period. The regional extended effect is an integrated benefit accumulated indirect benefit by flood mitigation infrastructure in the wide area under the influence of direct flooded area. Here an old flood mitigation project on the time extended effect in the Kiso River Basin in Japan and a flood control and drainage project in Metro Manila in Philippine on the regional extended effect are studied respectively.
