Integrating UAV‐Based Topographic and Geomorphic Analysis for the Development of River Rehabilitation Plans in Semi‐Urban Settings

Abstract

ABSTRACTSeveral rivers across the world face multiple threats from natural as well as human‐induced alterations in hydrology and morphology over time. Researchers have proposed several measures to instigate a healthier response by river rehabilitation or rejuvenation (depending on the condition of the river) to mitigate the impacts of causal factors. Investigating the causal factors of degradation is highly dependent on historical data, the availability of which depends on multiple considerations and is sometimes difficult to obtain, especially for a small river. A range of rehabilitation options have been explored by researchers among which geomorphology‐based approaches have gained importance as they are based on process‐based understanding and aim to reconstruct the river form for improving the river status. This paper introduces a novel method that uses very high‐resolution UAV data to analyze the topography and geomorphology of a small monsoon‐fed Sakri River in Central India. We aim to understand the anthropogenic factors responsible for its degradation with a particular focus on siltation and propose a river rejuvenation plan by creating the baseline data. The Sakri River supports 23 villages and a small town called Kawardha. The river presently has scanty surface flow and is unable to sustain the community. We mapped the entire river course using a UAV and identified 118 problematic sites, including 68 interventions along the 50 km stretch of the river. We have identified siltation as the primary problem at most sites caused by poorly designed interventions and a reduction in flow. We divided the river into 17 reaches and classified them into different states of criticality based on the identified problems and accumulated sediment volume behind the interventions. We have estimated a sizable volume of siltation within the 17 reaches as 0.5 million m3. Our analysis led to the development of a process response system that describes the various factors responsible for the degradation of the Sakri River and has important implications for designing mitigation strategies. Our recommendations for remedial measures are based on careful evaluation of the efficacy of each intervention and we have suggested their renovation or removal. We have also suggested reach‐specific solutions such as canal lining, river training, channel alignment, and river bank protection to be implemented.