Author(s): Muto Yasunori, Murata Yuki, Miyoshi Manabu, Tamura Takao
Linked Author(s): Yasunori Muto
Keywords: Retarding effect, paddy fields, inundation simulation, land-use change, roughness coefficient
Abstract: Retarding capacity of wetland paddy fields was evaluated using a commercial inundation simulation software, AFREL, based on 2-D shallow flow model for both surface and channel flows. Effects of several land-use change, such as housing land development, rice cropping abandonment and river improvement works, on the capacity were also examined. Sensitivity analysis for the roughness coefficient was carried out and the best set of the coefficients was validated with the inundation records in Typhoon 1511, July 2015. The simulation results successfully illustrated temporal variations of the inundated area and its depth distributions. When about 30% of the wetland are changed to develop houses, the maximum flooded volume reduces about 90% of the present situation, mainly due to raising land elevation for housing. When rice cropping abandonment arises alternatively, the maximum flooded volume does not change so much, probably due to slightly change of roughness coefficient from 0. 06 to 0. 05. When the river and irrigation channels are enlarged, reduction of the maximum flooded volume is about 89% of the present situation, similar to the housing development. Responses of the wetland against rainfalls with different return periods are also studied and the results show that the effect of land-use change is somewhat different under the rainfall with an extreme long return period like over 100 years from that in less precipitation magnitudes. The housing land development, nevertheless, is effective in retarding inundation area, mainly by raising land elevation for housing
Year: 2017