Impact of urbanization on flooding: The Thirusoolam sub watershed – A case study

SummaryThe change in the land use pattern due to rapid urbanization adversely affects the hydrological processes in a catchment, leading to a deteriorating water environment. The increase in impervious areas disrupts the natural water balance. Reduced infiltration increases runoff and leads to higher flood peaks and volumes even for short duration low intensity rainfall. Due to their destructive effects, floods can significantly increase the expenses on mitigation efforts. The present study focuses on the Thirusoolam sub watershed, an urban watershed in Chennai. Land use changes associated with urbanization in the watershed are invariably reflected in the stream flow regime. This paper emphasizes on an integrated approach to flood management, considering the land use change into the hydrological model. Integrated Flood Management (IFM) aims to harmonize human activities and flood risks through appropriate interventions to modify the water regime, and adaptation of human behavior thereby reducing such risks. Therefore, the hydrological impacts of urbanization should be considered for effective urban planning. The outcome of the study would help in formulating policy guidelines and intervention strategies.

► The impact of urbanization due to change in land use pattern for Thirusoolam sub watershed is examined.
► Information is provided for better land use planning and control considering flood risk areas.
► Appropriate Manning’s coefficient and flow contribution from the upstream areas are taken into consideration.
► Rapid urbanization has increased the flooded area and water depth for the same amount of rainfall.