Linkages between land use change, flooding, and water quality in the Pallikaranai Marshland, Chennai, India

The Pallikaranai marshland, one of the last remaining natural wetlands in the Chennai Metropolitan Area, plays a crucial role in flood regulation and water quality maintenance. Rapid urbanization, land use/land cover (LULC) changes, wetland encroachment, and expansion of impervious surfaces have significantly altered its hydrological and environmental functions. This study evaluates the impact of urban land use changes and flooding on water quality in and around Pallikaranai during March 2025. Flood-prone areas were identified using historical satellite imagery and spatial analysis. LULC classification revealed the dominance of built-up areas, reduction in wetland extent, and increased impervious cover. Water quality analysis indicated elevated electrical conductivity, total dissolved solids, hardness, and sodium concentrations in flood-affected zones. Organic pollution indicators such as BOD and COD were also higher in highly urbanized and flood-prone areas. These trends suggest contamination from urban runoff, sewage intrusion, and landfill leachate during flood events. Parameters including pH, nitrate, sulphate, and iron largely remained within permissible limits. Despite this, overall water quality showed signs of stress in areas influenced by flooding and urban activities. Flooding was found to act as a major transport mechanism for pollutants across the landscape. The study highlights the need for wetland conservation, restoration of natural drainage systems, and sustainable urban planning to protect water resources in Chennai.