Rainwater Harvesting for Urban Flood Risk Assessment: A BIM ‐ GIS Integrated Approach

ABSTRACT This research investigates the implementation of rainwater harvesting (RWH) systems using Building Information Modeling (BIM) and Geographic Information Systems (GIS) to mitigate urban flooding in Islamabad. Urban flooding, exacerbated by rapid urban expansion, inadequate drainage systems, and changing climate patterns, presents significant challenges globally, including in Islamabad. A comprehensive literature review highlights the need for sustainable water management and innovative flood risk assessment strategies. GIS‐based multi‐criteria analyses including land use, topography, soil properties, rainfall, and runoff potential were carried out, and Sector E‐11 was selected as a case study for suitable sites for the implementation of RWH. The Curve Number (CN) parameters obtained from the GIS were then used to simulate the runoff hydrographs and calculate the hydrologic performance. The resulting hydrographs were then used to design a required storage volume of 350.6 m 3 using the mass‐curve method and a 6.64 m 3 first‐flush diversion volume, both of which were fed into a shared and traceable GIS to BIM design workflow and embodied within a parametric Autodesk Revit model. The integrated system achieved an overall reduction of 26.5% in the simulated peak discharge from 0.509 to 0.374 m 3 /s, a 5‐min delay in the flood peak and a reduction of the event runoff volume of 71.6 m 3 . Rainfall analysis also suggested that the harvested rainwater from an annual rainfall of 1261 mm would be about 227 m 3 which can meet the annual water requirement of a typical domestic household to a good extent (about 86%). The study demonstrates that RWH systems effectively mitigate flood risks and enhance water security.