High-Resolution Waterlogging Mapping Along Ghazipur Drain in Delhi: A UAV-Based Bathymetric Analysis Approach

Urban waterlogging, especially post-monsoon, exacerbates environmental, economic and public health problems in rapidly urbanizing areas. This study employed UAV-based orthophotography and bathymetric data to examine waterlogging risks along the Ghazipur Drain in Delhi, India. High-resolution Digital Elevation Models (DEMs) with a 5 cm ground sampling distance and bathymetric profiles revealed considerable drainage losses and sedimentation that reduced channel capacity by 25%. This key finding quantifies the extent of hydraulic degradation and is vital for informing infrastructural needs. A map from the study highlights approximately 1,120 settlements in the low-lying areas, including Kalyan Puri, Jafrabad, Seelampur, and Karawal Nagar, at the highest flood risk during the monsoon months due to poor drainage and a high degree of urbanization. This highlights the scale of precarious urban living and the demand for action. When combined with bathymetry, UAV data are highly beneficial for acquiring the path, elevation, and bottom features of these outflows, revealing issues such as sedimentation and obstacles. Orthophotos (pixel resolution = 0.05 m) provide detailed urban infrastructure visualizations, including drainage systems, to enable site-specific interventions, such as dredging and channel widening. These high-resolution datasets provide a strong evidence base for operational planning and resource allocation. This method emphasizes the social and economic implications of waterlogging, such as property damage, transport disruption, and growing health hazards from waterborne diseases, which profoundly impact low- to middle-income communities. As described in this study, the influence of UAV-bathymetry in urban drainage research can be considerable. This has accurately integrated data from UAVs in flood risk management activities and led to urban systems planning with a higher resilience level. This will translate into actionable insights to improve drainage infrastructure, reduce flood hazards, and increase urban resilience, which is useful information for planners and policymakers. This result confirms that UAV-bathymetry is a scalable, precise, and low-cost solution for urban waterlogging in fast-developing cities worldwide.