Assessment of gully erosion in Dashtiary Plain, Chabahar, Iran: Insights from SENTINEL-1 InSAR analysis

Gully erosion is a kind of soil erosion that is formed when surface water runoff washes away the soil along drainage lines. Most research on soil erosion has focused on other kinds of erosions (e.g. Interrill and rill erosion), and relatively few studies have been conducted on gully erosion. However, recent studies indicate that gully erosion acts as a major sediment source in some environments. Furthermore, in many cases, farmlands productivity is decreased due to the presence of gullies, and they are even turned into wastelands because of the vast gully formation. In this study, we focus on Dashtiary Plain, which is an important agricultural area and the largest plain in SE Iran. The plain has been vastly affected by gully erosion. However, no information is available about the kinematic of the study area yet. We use Sentinel-1A Synthetic Aperture Radar (SAR) data and assess ground deformation in the areas affected by gullies. 36 Sentinel-1A images from 2014 to 2017 are processed using InSAR time-series analysis, implemented in GMTSAR. Small Baseline Subset (SBAS) method is used to analyse the time series of Sentinel-1A images and their related interferograms. The result show continuous subsidence close to the locations of gullies, with the maximum velocity of 10 cm/year in line-of-sight directions. By comparing the velocity map in the gully areas and regions not affected by gullies, it is revealed that gully areas have remarkably higher subsidence rates with respect to other areas. This finding is associated to the activeness of the areas affected by gully erosion in the Dashtiary Plain.