Urban Flood Hazard Assessment and Management Practices in South Asia: A Review

Abstract

Urban flooding is a frequent disaster in cities. With the increasing imperviousness caused by rapid urbanization and the rising frequency and severity of extreme events caused by climate change, the hydrological status of the urban area has changed, resulting in urban floods. This study aims to identify trends and gaps and highlight potential research prospects in the field of urban flooding in South Asia. Based on an extensive literature review, this paper reviewed urban flood hazard assessment methods using hydraulic/hydrological models and urban flood management practices in South Asia. With the advancement of technology and high-resolution topographic data, hydrologic/hydraulic models such as HEC-RAS/HMS, MIKE, SWMM, etc., are increasingly used for urban flood hazard assessment. Urban flood management practices vary among countries based on existing technologies and infrastructures. In order to control urban flooding, both conventional physical structures, including drainage and embankments, as well as new innovative techniques, such as low-impact development, are implemented. Non-structural flood mitigation measures, such as improved flood warning systems, have been developed and implemented in a few cities. The major challenge in using process-based hydraulic models was the lack of high-resolution DEM and short-duration rainfall data in the region, significantly affecting the model’s simulation results and the implementation of flood management measures. Risk-informed management must be implemented immediately to reduce the adverse effects of climate change and unplanned urbanization on urban flooding. Therefore, it is crucial to encourage emergency managers and local planning authorities to consider a nature-based solution in an integrated urban planning approach to enhances urban flood resilience.

Flood Prevention Strategies for Major Rivers in Afghanistan, China, India, Pakistan, Philippines, Thailand, Vietnam using Traditional Methods and Digital Technologies

“…In South Asian cities, floods that destroy entire neighbourhoods are happening more frequently and harming more people. Climate change and unchecked urbanization are the main factors contributing to the region's elevated flood danger [4]. By precisely predicting probable flood zones through hazard mapping, the impact of flooding can be minimized.…”

Evaluating the Utility of Selected Machine Learning Models for Predicting Stormwater Levels in Small Streams

“…This situation is further aggravated by the alteration of natural waterways. In the pursuit of urban expansion and development, these waterways are often redirected or constrained, impacting their natural flow and capacity to handle floodwaters [37,38]. The result is a heightened risk of flooding, not just from the overburdened drainage systems but also from the altered waterways that can no longer accommodate sudden influxes of water.…”

WaterLog: A New Spectral Index for Mapping Aquatic Surfaces in Urban Contexts

“…In the context of urban areas, mapping WSs serves numerous purposes, including supporting policies aimed at both water resource sustainability -such as water quality monitoring [7], [8], [9], and mitigating social and environmental impacts, such as floods caused by unplanned urban growth and climate change [10], [11]. To address these impacts, managers should focus on practices and actions that make cities more resilient [12], [13].…”