Spatial Variability of Ground Deformation of Coastal Regions of the Krishna Delta, East Coast of India Using SAR Interferometry

Abstract

The Deltas of the east coast of India are highly susceptible to vertical deformations due to various factors like hydrological changes, reduced sediment inflow from rivers, groundwater exploitation, hydrocarbon extraction, sea-level variations, and neotectonics. This study focuses on the LOS (Line of Sight) deformation in the Krishna Delta, India, during the years 2006–2011 and 2016–2018, observed using L- Band [Advanced Land Observation Satellite (ALOS)-1] and C-Band (Sentinel-1 A) satellite data, respectively. The displacement rates were determined through time series Interferometric Synthetic Aperture Radar (InSAR) analysis using the Small Baseline Subset (SBAS) approach. A total of 49 interferograms from ALOS-1 and 241 from Sentinel-1 A, corresponding to 19 ALOS and 70 Sentinel-1 A images, were selected based on geometrical and temporal baselines. Along the coastal region of the Krishna Delta, 25 transects were analyzed for two different periods to understand the LOS deformation rate. Among these evaluated transects, 11 showed uplift, 11 exhibited subsidence, and 2 remained stable. Transect No 12 which falls within a no-data zone due to coastal inundation yielded null results. The observed subsidence (5–6 mm/yr) was predominantly in regions associated with aquaculture activities. We hypothesize that the groundwater imbalance resulting from aquaculture activities is a prevailing factor in the observed ground deformation in this region. Various factors such as accretion, mangrove cover, and spit morphology were also explored to understand uplift in the study area. The InSAR technique demonstrated its capability for estimating land deformation, establishing it as one of the best methods in coastal delta studies.