Mitigating Flood Losses Using Real-time Forecasting in India

Devastating floods in Indian cities are increasing. In 2015, the flood in Chennai claimed 500 lives, displaced one million people, and generated a $3 billion loss for the city.

According to an EOS article, the degree of damage and loss has prompted the government to reach out to scientists to develop a weather forecasting system.

The article says that Chennai’s vulnerability to flooding is due to its topography – it is a coastal city with many rivers and an upstream catchment area that allows the waters to flow during heavy rains.

Flooding forecasting system

Launched in 2019, scientists from the government and research institutes have gathered to work on Chennai’s flood forecasting system.

Leading the effort is Subimal Ghosh, a professor of civil engineering at the Indian Institute of Technology Bombay. He says, “We generated 800 scenarios of flood and tide conditions,” Ghosh said. “When the model receives a weather forecast from the National Centre for Medium-Range Weather Forecasting, it will search and find the closest scenario. If there is a chance of flood, the model will predict the vulnerable sites for the next 3 days.”

Sisir Kumar Dash, a scientist at the National Centre for Coastal Research (NCCR) in Chennai and responsible for operating the model, says that “We analyze daily rainfall data, and if there is a probability of inundation, the model is run, and alerts are sent to the state disaster management department.”

A flood forecasting system in another Indian city of Bengaluru, formerly Bangalore, has had some successes.

Describing the city’s forecasting system, P. Mujumdar, a professor of civil engineering at IISc and who led the work, says that “short-duration rainfall forecasts from various weather agencies were combined with our hydrology model (which has high-resolution digital elevation maps of the city) and information on drainage systems and lakes. Real-time rainfall data are obtained through a network of 100 automatic rain gauges and 25 water level sensors set up on stormwater drains at various flood-vulnerable areas across Bengaluru. The model, however, is unable to make reliable predictions if the rainfall is sudden and didn’t appear in the forecast”.

However, Raj Bhagat Palanichamy, manager at the Sustainable Cities initiative of the World Resources Institute, takes another view of predictive technology.

For Palanichamy, “A good model is not about the tech or visualization that come with it; instead, it’s “about the ability to help in the decisionmaking process, which hasn’t been successfully demonstrated in India.”

Mujumdar adds that climate change and urbanisation are making short-duration, high-intensity floods occur more frequently in Indian cities, and predictive models should be developed for all cities.

Predictive models like the flooding forecasting systems in India effectively warn people about the impending risks to help them prepare that can significantly reduce loss and damages.

However, while predictive models can alert people to protect them from flooding in India, this is not enough to reduce its impact nor prevent its occurrence.

Local governments can do other actions to mitigate floods and reduce their impact on the city’s residents, assets, and infrastructures.

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PHOTO CREDIT: Chennai City by SlowPhoton – Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=84161890