Impacts of land use–land cover change and urbanization on flooding: A case study of Oshiwara River Basin in Mumbai, India

• Impact of LULC change & urbanization on flooding studied for an urban catchment
• LULC effect on flooding has been found by HEC-GeoHMS & HEC-HMS models.
• Flood plain & hazard maps for various flow conditions & LULC patterns developed
• Flood plain and hazard maps can be used for preparation of flood mitigation.

In the present study, the impact of land use–land cover (LULC) change and urbanization on floods are investigated for an expanding urban catchment of the Oshiwara River in Mumbai, India. For the study area, the land use change was estimated between 1966, 2001 and 2009 by using the topographic map and satellite images. The analysis of LULC change revealed that the change between 1966 and 2001 was slower than that between 2001 and 2009. The LULC analysis revealed a 74.84% increase in the built up area with a 42.8% decrease in open spaces between the years 1966 and 2009, with substantial increase in urbanization. The impact of LULC on flood hydrograph for different return periods was ascertained by using the HEC-GeoHMS and HEC-HMS models. In the past 43 years, the increase in peak runoff and runoff volume is marginally varied by 3.0% and 4.45% for the 100-year return period and 10.4% and 12.2% for the 2-year return period respectively, although the built-up area increased by 74.84%. The flood inundation area is increased by 5.61% for the 100-year return period and 6.04% for the 10-year return period between the same time period. The results showed that lower return periods led to a maximum change in peak discharge/volume of runoff compared to higher return periods for change in land use conditions. Further, a flood hazard analysis has been carried out and it showed that the area in highly hazardous zone is increased by 64.29% as compared to less hazardous zone where it is decreased by 32.14%. Overall, the total flood hazard area is increased by 22.27%. The developed flood plain and flood hazard maps can be used by the local Municipal body to prepare flood mitigation and early evacuation management plans during floods and as a criteria for insurance of any property by insurance organizations.