Integrated assessment of contemporary hydro-geomorphologic evolution of the Indus River Estuary, Pakistan in context to regulated fluvial regimes

Abstract The riverine ecosystem is dependent upon the supply of fresh water but the decrease in flows weakens this connection. It gradually leads to impairment of ecologic as well as geomorphologic settings of a riverine ecosystem. Keeping this in view, the present study was designed to assess the contemporary evolution of the Indus River Estuary (IRE) under forced hydrological conditions. An account of transitions in the eco-geomorphologic response of the IRE was synthesized using satellite imageries from 1972 to 2016 and interpreted with the ground observations. Due to flow regulations, an 80% decrease in average annual flow and 50% dampening of flood peaks have altered its hydrological regime. These pronounced hydrological shifts have also played a significant role in the modulation of channel morphology. Similarly, the morphological configuration of the estuary like the length and width of the channel have also increased by 11% and 29%, respectively, and the rate of erosion was more than the deposition. After experiencing significant variations in the rate of lateral migration, the channel has started creeping in a south-eastern direction dominantly since 1993, with an average rate of migration of 44 m/yr. Correspondingly, the riparian landscape has also evolved coherently with a notable competition between bare land and the vegetative cover. Trade-offs between the river hydrology, channel morphology and landscape ecology were understood with a correlation matrix and interpreted with plausible causes. It would help the policymakers to assess the overall ecological health of the IRE and contribute the experts working on designing a framework for the study of system dynamics.