Flood Early Warning Systems

Early warning systems are an essential component of disaster risk management. Their primary purpose is to issue warnings when a threatening phenomenon is imminent or already occurring. Among different types, Flood Early Warning Systems (FEWSs) are the most common since floods occur worldwide frequently. From the year 2000 through to 2018, they accounted for about 54% of all water-related disasters (WRDs) globally, causing about 3,470 deaths and causing nearly 500 billion USDs economic losses. The probable increase in the number and degree of extreme weather prompting events such as floods makes this technology necessary for climate change adaptation.

Early warning systems, including FEWSs, comprise four closely interrelated elements: 1) assessments and knowledge of disaster risks in the area of interest, 2) local detection, monitoring, analysis, and forecasting of hazards, 3) warning dissemination and communication service, and 4) community response capabilities. This multifunctional system improves community preparedness for extreme weather-related events such as floods, in terms of both warning and increasing understanding of risks and appropriate responses, and minimizes safety and infrastructure threats. As part of the warning, the system predicts the scale, timing, location, and likely damages of the impending flood. It uses sensors to measure water levels at strategic points in local water basins or flood defences like dikes, dams, and embankments to forecast a potential flood event.

The example of Kolkata

Kolkata, India’s West Bengal state’s capital, with a population of around 14.8 million people, is regarded as one of the most flood vulnerable cities in numerous studies. It is mainly due to its high exposure to flooding under climate change projections, mostly during the monsoon season when cyclones pass through the region. Since 2000, the Kolkata Municipal Corporation (KMC), supported by the Asian Development Bank (ADB), has started to improve urban services and climate resilience. The mitigation measures include expanding sewage and drainage networks, increasing sewage treatment capacity, and improving water supply through reductions in non-revenue water, i.e., the water that is lost before reaching the customer.

Continuing the path to resilience, KMC has started the Kolkata Environment Improvement Investment Program (KEIIP), funded by the ADB’s Urban Climate Change Resilience Trust Fund (UCCRTF) since 2018. One of the components of the KEIIP is the city’s FEWS, which would be the first comprehensive city-level early warning system in India, and is schematically sketched in the figure below. It would strengthen the city’s resilience by having weather forecasts and flood models, real-time information such as key pump status, canal water levels, actual rainfall, and inundation levels, and a messaging system to provide warnings and real-time information to city officials and citizens.

References:

• D. Perera et al., “Flood Early Warning Systems: A Review of Benefits, Challenges and Prospects,” Hamilton, Canada, 2019.
• D. Perera, O. Seidou, J. Agnihotri, H. Mehmood, and M. Rasmy, “Challenges and Technical Advances in Flood Early Warning Systems (FEWSs),” in Flood Impact Mitigation and Resilience Enhancement, IntechOpen, 2020.
• ADB, “Toward Resilient Kolkata: Introducing India’s First Comprehensive City-Level Flood Forecasting and Early Warning System,” 2018.