Soil Loss Estimation and Forecast Using the USLE for Farmland in Hokkaido

Abstract

The soil loss amount was estimated by using the Universal Soil Loss Equation (USLE) for each farm field in Hokkaido, where many fields are at high risk of soil erosion because of their large size and slope. A GIS was used to calculate the soil loss amount, and methods for determining factors relevant to wide-area analyses were examined. In setting a rainfall factor, the amount of precipitation that was forecast under the Research Program on Climate Change Adaptation (RECCA) conducted by the Ministry of Education, Culture, Sports, Science and Technology of Japan was used to estimate the soil loss amount in anticipation of future climate changes. In terms of the regional characteristics of soil loss at fields without protective measures, it was confirmed that many such fields whose soil loss was forecast to exceed the annual acceptable level were located in southern Hokkaido, where steep upland fields are common. Regarding the upland fields whose soil loss was forecast to exceed the annual acceptable level even with protective measures (e.g., furrowing transversely across the slope) taken for farming management, it was suggested that measures for controlling soil loss would be necessary from the viewpoint of sustainable farmland maintenance. Additionally, it was predicted that the average amount of soil loss across Hokkaido would be 1.26 times the current level due to the increase in the rainfall factor.