Spatiotemporal analysis of the extreme storm surge and wave events for forecasting coastal floods along the coastline of India
Abstract
The Bay of Bengal and the Arabian Sea adjoining the coastline of India are breeding grounds for depressions and tropical cyclones, with 2 to 3 cyclones making landfall every year on average. Coastal flood events caused by extreme sea levels along the coast are primarily driven by tropical cyclones and storms in the sea. As they can have catastrophic consequences on several hotspots and population in the coastal area, there is a need to devise effective strategies to forecast those events. This study presents results discerned from spatiotemporal analysis of the extreme storm surge and wave events along the coastline of India and assesses the scope for forecasting coastal floods in the area based on in-situ data. Sea level (1980-2020) and wave parameter (2011-2020) data for the study are obtained at an hourly scale from 9 tide gauge stations (TGs) operated by the Survey of India along the coastline and 7 drifting buoys managed by the Indian National Centre for Ocean Information Services (INCOIS), respectively. Harmonic analysis is initially carried out on the corrected sea-level (SL) data to separate the astronomical tide component and obtain the non-tidal residual (NTR) and skew surge (SS) component corresponding to each of the TGs. Subsequently, using state-of-the-art methods, univariate extreme value analysis using the peaks-over-threshold method is carried out for the SL, NTR, SS, and significant wave height (Hs). The contribution of extreme SS and NTR to the extreme SL near the coast is determined during different seasons for different tidal scenarios. The dependence structure between the extreme SS and NTR at nearby tide gauge stations and nearest offshore buoys is investigated using rank correlation and tail dependence coefficients. Investigation indicates a moderate inter-site lagged correlation between extreme surge (SS, NTR) and SL events and significant dependence between the extreme surge values and the corresponding daily maximum Hs. Joint return levels for surge and wave extremes are analyzed based on copulas and conditional approach, and the temporal variation of these extreme events are analyzed for the historical period. Finally, a comparative analysis is performed on the surge and wave extremes characteristics at various hotspots along India's coastline
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2022
- Bibcode:
- 2022AGUFM.H35J1263D