Modelling and forecasting of urban flood under changing climate and land use land cover

Abstract

Chennai is a rapidly urbanizing Indian mega-city and experiences flooding frequently. Literature state that climate change and land use change have a significant impact on the runoff generated every year, making it essential to study the historical trend and forecast changes in land use land cover (LULC) and climate to model runoff. This study considered Adyar watershed for LULC change detection, climate change analysis, and flood forecasting for 2030 and 2050 based on LULC and runoff from 2005 and 2015. A coupled hydrologic–hydraulic model (HEC-HMS and HEC-RAS) was developed to assess flooding for future LULC and climate scenarios. LULC analysis shows an increase in built-up cover by 6%. Climate analysis shows 74% probability of increase in precipitation intensity between 2015 and 2050 compared to 2015. It was observed that depth of flooding increased by 19.4% in 2030 and 60.4% in 2050 compared to 2015. This study makes a structural proposition for flood mitigation through flood carrier canals on the downstream reach of the river which flows through Chennai. The canals were found to significantly reduce overbanking, providing protection against flooding. This is the best measure for providing the highest flood reduction for the study area. HIGHLIGHTS Coupled hydrologic and hydraulic model was developed to assess flood inundation of Adyar river basin.; Terrset land change modeller was used to project future land use for 2030 and 2050.; Climate change projection for 2030 and 2050 was carried out using regional climate models.; Flood carrier canals were proposed to mitigate future flooding conditions under extreme events.; Developed mitigation measure was analysed through HEC-RAS model.;

Keywords

• chennai
• coupled hydrologic–hydraulic modelling
• flood inundation
• flood mitigation
• land use and climate change
• river adyar