Flooded Cities

Is it the Weather or a Mismanaged System?

- Ms Suruchi Bhadwal

To understand a system and its dynamics in the context of floods, nothing could be more finely expressed the way John Hewlett did 40 years ago by querying on how the entire system operates—“Where does the water go when it rains? What flow path does it take to the stream? How long does it reside in the catchment? Suruchi Bhadwal and Prasoon Singh try to find answers to these questions as they analyse the problem of urban flooding in Mumbai and other cities in India.of which about 8 million hectares are susceptible to annual flooding. These are areas in the coastal stretches and adjoining river systems that have been identified as sensitive areas and prone to the occurrence of such events.

Floods are categorized as coastal flooding and riverine flooding. It is attributed to weather conditions and change in land-use of the catchment. This includes torrential rains, cloudbursts, massive snow/glacial melt leading to floods, flash floods in mountain areas, wherein a sudden rise in water levels due to the above reasons is experienced. Degradation of land use can cause significant impact on infiltration rates leading to greater run-off and high discharge rates leading to floods in catchments. There are other factors, such as climate change that are further influencing the nature of these events through an enhanced hydrological cycle, which would increase the occurrence of such events in future time periods. An increase in the frequency of heavy precipitation events is likely to intensify in all emission scenarios. Unplanned development without adequate preparedness to handle such situations further exposes regions to the consequences of such events. Questions to grapple are to understand the cause of floods and what can be done to minimize the losses to the extent they can.