Comparison between a Soft and Crisp Geographic Boundary of the Soil Texture Component in Hydrologic Models

Abstract

This note is based on the generally accepted fact that soil boundaries are usually gradual rather than abrupt, and this is followed by an application of fuzzy set theory to what are already known to be diffuse boundaries. Sediment yield measurements are used to describe the control condition against which the fuzzy and conventional boundaries are assessed. In terms of the K factor, the fuzzy boundary representation showed less difference (up to 16.8%). The Nash–Sutcliff coefficient of efficiency and the root mean square error for the fuzzy boundary are 0.96 and 1.3× 10−3 , respectively, whereas those for the conventional boundary are 0.76 and 3.4× 10−3 , respectively. The estimation by the soil erosion model shows that the fuzzy representation of geographic boundary is more accurate than the conventional method. But the difference between erosion predictions using conventional boundaries and fuzzy boundaries is relatively small.