Impact of land use and climate change on urban flooding: a case study of Bhubaneswar city in India

Urban floods are prevalent issue in India, especially during the rainy season i.e. June to September. While rural floods are mainly caused by excessive river discharge, urban floods result from factors like rapid urbanization and climate change. As cities expand, they cover more land with impermeable surfaces, exacerbating flooding risks. This study investigates the impact of land use and climate change on urban and peri-urban areas within the Extended Bhubaneswar Development Authority zone in India. CMIP6 Global Climate model NorESM2-MM and SSP 4.5 scenario was used in this study to assess climate change effects from Historical (1985-2014) to Near Future (2015-2050), Mid Future (2051-2070) and Far Future (2071-2100). IDF curves indicate rising rainfall intensities from baseline to far-future scenarios. MOLUSCE plugin in QGIS was used to anticipate land use changes in 2050, 2070 and 2100. LULC maps from 2014 to 2100 show significant urban expansion, marked by increased built-up areas and reduced forest cover. Impervious surfaces in the Bhubaneswar Municipality Corporation are expected to rise from 51.28% to 81.12%, while in the Extended Bhubaneswar Development Authority zone, they are projected to increase from 16.37% to 34.52% by 2100. Storm Water Management Model (SWMM) estimates surface runoff, revealing a consistent rise in flow rates across return periods, indicating a high risk of urban flooding. For Flood Inundation Mapping (FIM), the Hydrologic Engineering Center's -River Analysis System (HEC-RAS) was utilized to assess flood depth and extent across near, mid, and far-future scenarios, with a consistent increase in flood-prone zones across return periods. Vulnerability assessments across various return periods identify specific areas, including various wards of Bhubaneswar as consistently vulnerable. Maximum flood depths from inundation mapping was found to be 0.752 m during the baseline period, increasing to 0.960 m in the near future, 1.08 m in the mid-future, and 1.18 m in the far future for 100 year return period. Additionally, Nuagaon, Lingipur and other areas face increasing flood risks with longer return periods. These findings offer vital insights for officials to develop targeted flood mitigation strategies and enhance resilience in vulnerable areas, crucial for safeguarding the municipality against future flood events.