Geospatial analysis and model development for specific degradation in South Korea using model tree data mining

Abstract

South Korea experiences numerous local sedimentation problems, such as landslides, upland erosion, aggradation and degradation, and flood plain sediment deposition. This has necessitated the development of a reliable and consistent approach for modeling sediment processes in the country. In this study, samples obtained from 35 gauging stations at five alluvial river basins in South Korea were used together with the modified Einstein procedure and series expansion of the modified Einstein procedure to determine the total sediment load at the sampling locations. Using two different methods, the total sediment load of majority of the 35 considered rivers were found to be typically 50–300 ton/km2·yr. A model tree data mining technique was used to develop a model for estimating the specific degradation based on certain meaningful parameters, namely, the 1) elevation at the middle relative area of the hypsometric curve [m], 2) percentage of wetland and water, 3) percentage of urban land, 4) mean annual precipitation [mm], 5) main stream length [km], and 6) watershed form factor [km2/km2]. The root mean square error of the predictions of the proposed model was found to be 55 ton/km2·yr less than those of existing statistical models. Erosion loss maps obtained by the revised universal soil loss equation (RUSLE), satellite images, and aerial photographs were also used to represent the geospatial features affecting erosion and sedimentation. The results of the geospatial analysis indicated that the transport of sediment into the alluvial rivers was affected by the wetlands located near the rivers, and also enabled clear delineation of the unique erosion features of construction sites in the urban areas. In addition, the watershed morphometric characteristics could be used to accurately represent the sediment transport. The proposed data mining methodology promises to facilitate the solution of various erosion and sedimentation problems in South Korea. The geospatial analysis procedure would also enable the understanding of spatially varied erosion and sedimentation processes under different conditions.