Geomorphological study of intertidal mudflats using RISAT-1 SAR images

The coastal zone of the Gulf of Kachchh (GoK) is well known for their large tidal range and a vast expanse of intertidal mudflats. Since monitoring of the intertidal mudflats with field observations is not feasible, the paper presents the utilization of microwave remote sensing technique with RISAT-1 dual polarized data for the geomorphological studies of intertidal mudflats. Radar measures backscattering coefficient, which depends on surface roughness parameters, where the surface roughness of intertidal mudflats are functions of sediment ripple height and space between consecutive ripples. Ripple’s height and the distance between ripples (its wavelength) are represented here as root-mean-square height (RMSH) and correlation length (CL) respectively. A semi-empirical model is used to derive RMSH using cross-polarized backscattering coefficient, and CL is calculated using inversion algorithm on a ratio of backscattering coefficient. A surface sediment type map is generated, based on the retrieved surface parameters, and validated with another sediment type map which is classified using an optical multispectral image. Error statistics are calculated for simulated and observed backscattering ratios, which indicate the general acceptability of the model in estimating the surface roughness parameters of tidal mudflats.