2022 Volume 77 Issue 5 Pages I_431-I_447
Ongoing urban planning forces us to take account of disaster risks and ordinary convenience as targets. However, some regions face trade-offs between these two targets due to various conditions such as topography or industrial structure. The problem was highlighted in damaged fishery villages after the Great East Japan Earthquake: fishers who work close to the sea relocated to higher area for safety; meanwhile, they had to accept the inconvenience of long commuting. This study developed an optimal residential area model for analyzing the trade-offs between safety from tsunamis and ordinary convenience, which will be able to support the consensus-building among stakeholders. The model consists of weighted multicriteria: the total tsunami risk, the total infrastructure maintenance cost, and the total traffic time for commuting with controlling optimal allocations of population, land use, and commuting trips. Here we optimize “Reduction Potential Achievement (RPA)”: it indicates how much the respective optimal value achieved against the value (reduced potential) that the three objectives were optimized alone as a baseline. We applied the model to Kuroshio, a tsunami-prone area along the Nankai Trough in Japan, and calculated for each 500-meter mesh. According to the results with various combination patterns of the control variables, the larger the number of variables, the more concentrated residential areas became. Furthermore, sensitivity analysis results that change the weight of each criterion revealed trade-offs in which the more the tsunami risk is weighted, the more the infrastructure maintenance and traffic costs increase.
