Nature-Based Disaster Risk Reduction of Floods in Urban Areas

Floods in urban areas have become more frequent globally, with catastrophic impacts. The cause is not only a natural event of extensive rain but is also artificial. The artificial cause of floods in urban areas can be attributed to two main factors – urban flooding and mismanagement of water resources leading to riverine flooding. Urban flooding is characterized by quicker inundation of the developed regions due to faulty city planning and development. Faster run-offs, overwhelmed drainage systems, disregard to topography and hydrology in city development, construction on reclaimed wetlands and flood plains increase urban flood vulnerability. For regular water supply to the cities, many dams and reservoirs are built upstream of the rivers flowing through the cities. With rains in the catchment, the capacities of these dams are surpassed, and water is released into the river. Unplanned water release and ill-treatment of riverfronts that can no longer harmlessly swell in urban areas lead to riverine flooding. Urban flooding and riverine flooding in urban areas could happen simultaneously, disrupting transport, life and economy. This review discusses the causes of flooding in urban areas and how to mitigate and reduce vulnerability using natural elements in urban planning, design and landscaping. Mitigation measures suggested in national and local policies are reviewed. Concepts like more Room for River, Sponge City and Green Rain Infrastructure are presented with relevant case studies. A holistic approach to flood-sensitive GIS-based city planning and design, including critical infrastructure design and flood mitigating landscape is recommended as a strategy for nature-based disaster risk reduction of flooding in urban areas.