Estimation of surface roughness in aird alluvial fan using SAR data

The geomorphic features of alluvial fans in arid and semi-arid areas can contain vast amounts of information for the study of paleoclimatic and paleoenvironmental changes. Taking the Shule River Alluvial Fan (SRAF) as study area, the research of surface roughness estimation, one of the important geomorphic features of the arid and semi-arid alluvial fans, was carried out by using Radarsat-2 polarimetric synthetic aperture radar (SAR) data in this paper. A modified roughness inversion model was developed to solve the roughness overvalued problem when the conventional models are used in arid surface of alluvial fans directly. In this model, the dielectric constant of the gravels exposed in the surface, instead of the moisture, becomes a more important influencing factor on backscattering coefficients. After comparing the results retrieved from the conventional and modified roughness invention models, the correlation coefficient increases from 0.68 to 0.85, and the absolute difference between the inversion and field measured value reduces obviously. As a result, the proposed model improves the accuracy effectively and is suitable for the roughness parameter inversion in the arid surface of alluvial fans.