Development and Evaluation of Relative Relief Based Soil Thickness Model: A Comparative Study in Hilly Terrain, South Korea

Soil thickness is a major parameter to better understand slope stability, surface erosion, groundwater storage, and vegetation growth. In this study, the main focus is the development and application of a relative relief (RR)-based spatial soil thickness model. Intensive field works were also carried out to gather ground-truthing soil thickness data using traditional drilling and excavation methods. The spatial distribution of soil thickness obtained from the RR model was validated with the results of the field measurements, and compared with the predictions derived from S and multiple linear regression (MLR) models, which are already known in the literature. In this study, we tested how raster resolutions (5, 10, 20, 30, 50, 60 and 90 m) influence the spatial prediction of soil thickness. Based on the comparison between the predicted soil thickness and the measured soil thickness, a map of 10 m resolution contributed reasonable delineation of soil thickness over the study area. A comparison of the predicted results was performed using the agreement coefficient (AC) which showed that the RR model has a better predictive ability (AC = 0.970) than the S (AC = 0.945) and MLR (AC = 0.710) soil thickness models. The results indicate that an adjustment to the soil thickness and spatial resolution can significantly improve the modelling efficiency.