Impact of River Dams on Littoral Cells Located Adjacent to the River Mouth

Kamal Nag

doi:10.12944/cwe.16.3.24

Abstract

Terrestrial sediment is a major source of sediment to all coasts. Suspended sediment is carried away by the rivers and supplied to the coast to maintain sediment budget. The construction of dams across the rivers arrest sediment behind it and affect the sediment budget of littoral cells along the coast. Reduction in sediment supply induces ecological as well as geomorphological changes along the shoreline. Coastal erosion may accelerate due to reduced sediment influx. With the growing number of cross-river dams and water diversion projects, it has become a major concern before the scientific community to measure, understand and find solutions to multi-fold geo-environmental problems that are arising out of river damming. The present study aims to find out the impact of dams on the coast. It examines how the changes in the suspended sediment supply of an Indian river impact the coast in terms of loss of area due to erosion. Temporal analysis of geomorphological changes along the shoreline in relation to sediment influx holds immense importance to coastal management essential for the sustainable life and livelihood of coastal communities. Scientific investigation into the impact of river dams on the coastal environment is likely to provide a strong ground to reconsider the way present basin development projects function. Areal changes in littoral sediment cells adjacent to the river mouth have been quantified and correlated with changes in sediment influx. Changes along the shorelines have been detected through multispectral satellite images of Landsat belonging to different dates. Image processing and quantification of changes have been performed in QGIS 3.14 “Pi” platform. Virtual raster, raster calculator, field calculator and other required tools in QGIS were used during image processing.

Highlights

Constructions of dams, reservoirs, water diversion projects etc. arrest sediment flux and decrease its supply to the coast.[1,2,3] Large rivers all over the globe are affected by dams
According to the International Commission on Large Dams (ICOLD), 45000 large dams all over the globe are obstructing the natural flow of rivers
Shifting of shorelines adjacent to the river has been detected through Landsat images for the said period of time (Table 1)

Summary

Introduction

Constructions of dams, reservoirs, water diversion projects etc. arrest sediment flux and decrease its supply to the coast.[1,2,3] Large rivers all over the globe are affected by dams. Constructions of dams, reservoirs, water diversion projects etc. Arrest sediment flux and decrease its supply to the coast.[1,2,3] Large rivers all over the globe are affected by dams. According to the International Commission on Large Dams (ICOLD), 45000 large dams all over the globe are obstructing the natural flow of rivers. Dam changes discharge volume of water and sediment and affects the entire river system. Sediments are arrested behind the dam and the coast receives reduced influx. Such reduction alters the coastal sediment budget. Impacts of reduced sediment influx may be visible near the estuary and littoral sediment cells adjacent to the river mouth. Coastal erosion, shifting of the river mouth and marine bar are geomorphological manifestations of reduced sediment influx

Methods

Results

Conclusion