Urban Floods and Suitability Analysis of Rainwater Harvesting Potential Areas in Lahore City, Pakistan

Abstract

There is a growing threat of urban flooding, particularly in Pakistan that needs attention and requires effective management strategies. The chief trigger for urban flooding is the rapid and unplanned urbanization in areas where impermeable surface inhibits rainwater diffusion and changes the natural water flow. In many developed countries, a technique of rainwater harvesting is implemented as a sustainable strategy to manage urban stormwater. Most studies and projects chiefly focused on the potential use of the Rainwater harvesting technique for water conservation in arid and semi-arid climates. In the present work, GIS and remote sensing methodologies are utilized for the suitability of rainwater harvesting structures. This study was conducted in Lahore, the second most populated city of Pakistan and the capital of Punjab. Generally, the water harvesting technique depends on topographical areas with water accumulation, where there is an availability of open spaces in the form of green areas and barren lands, rainfall, drainage network density, and rainfall distribution, particularly in the urban environment. The SRTM DEM data were used for finding high water accumulated areas, and the Landsat OLI image is used to retrieve land use information i.e. vacant land and open green spaces, existing drainage network density, and rainfall distribution. All these layers were integrated through AHP to detect the potentially suitable sites for the construction of rainwater harvesting structures. Results concluded 94 suitable sites with categorization from highly to critically suitable for the construction of rainwater harvesting structures in which 6 were highly suitable areas in Data Gunj Bakhsh Town and Ravi Town. Besides, residential areas are having a maximum site suitability percentage, followed by roads, agricultural and open spaces in the area under consideration. Considering the suitable sites, further rainwater harvesting methods can be identified in the study area to alleviate urban flooding and improve the urban environment.