Multivariate indicator-based flood hazard mapping using primary drivers of coastal flood for India

Area of Science:

• Environmental Science
• Climate Change Adaptation
• Coastal Management

Background:

• Coastal regions are vital economic hubs but face escalating threats from compound hazards like cyclones, storm surges, and extreme rainfall.
• The Intergovernmental Panel on Climate Change (IPCC) highlights the need for assessing coastal hazards as multi-driver compound events.
• India's extensive coastline (∼11,098 km) is particularly vulnerable, necessitating a comprehensive hazard assessment.

Purpose of the Study:

• To conduct a multi-driver coastal flood hazard assessment across India's coastal districts.
• To compare different objective weighting methods (equal weighting, entropy-based, PCA-based) within the TOPSIS framework.
• To identify key hazard drivers and high-risk regions for targeted mitigation planning.

Main Methods:

• Employed an indicator-based approach using the Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS).
• Utilized three objective weight estimation methods: equal weighting, statistical entropy-based weighting, and Principal Component Analysis (PCA)-based weighting.
• Key indicators included cyclone frequency, storm surge, wind speed, tidal range, and extreme precipitation exceedance probability.

Main Results:

• Entropy-based weighting highlighted cyclone frequency, while PCA-based weighting offered a balanced assessment.
• PCA-weighted TOPSIS provided a more conservative hazard perspective compared to entropy-weighted TOPSIS.
• North-eastern and North-western coastal districts were identified as highly hazard-prone, with Odisha and West Bengal showing consistently high levels.

Conclusions:

• Findings reveal distinct hazard drivers across regions: cyclones dominate the Bay of Bengal coast, while rainfall and tides impact Gujarat and Maharashtra.
• Kerala and Tamil Nadu generally exhibited lower hazard levels.
• The study provides a scientific foundation for developing region-specific flood mitigation strategies and optimizing resource allocation for coastal resilience.