Estimation Method of Public Cost Sharing for Drainage Facility Operation in Urbanized Low-lying Paddy Areas

Abstract

In this study, we proposed a method to calculate an appropriate cost-share rate for people in urban areas for the operational costs of drainage in agricultural facilities. To calculate this rate, we used discharge hydrographs with function fitting for design rainfall, and specific discharges in consideration of the increases in peak discharges and reductions in the time length to the peak resulting from urbanization. The proposed method was applied to the management of Nishikanbara region, one of the largest rice-growing areas in Japan. As a result, we were able to arrive at the proposition of this methodology and values for calculating appropriate cost-share rates by the people of urban-areas. When the cost-share rates was set at 1.0 per unit area for agricultural lands, we estimated the cost-share rate for people in urban areas would be in the range of 2.10 to 3.43, with an average of 2.77. In addition, we clarified that the proposed method can be applied even when there are changes in land use such as a decrease in agricultural land areas or when urbanization progresses.