STORM SURGE INUNDATION MODELLING FOR AMPHAN IN BANGLADESH PART

Abstract

During a Cyclone storm surge related forecasting and warnings in Bangladesh are provided by Bangladesh Meteorological Department (BMD) by giving forecasting and warning of the expected storm surge height during a cyclone. This forecasting does not give any forecasting regarding areas that might be inundated due to the storm surge. This study focuses on developing a storm surge inundation model using Delft3D using current state of the art in storm surge inundation modelling. This research is based on the super cyclone Amphan, which made landfall on May 20, 2020, across the Sundarbans from the west Bengal-Bangladesh coast. Its wind speed ranged from 155 to 165 kmph with gusts up to 185 kmph. At first the tide model is developed. Then after the calibration and validation of the tide model it is run using atmospheric forcing generated from the cyclone model. Cyclone model is run by using IMD and JTWC best track data of cyclone Amphan. Then calibration and validation of the cyclone model shows that the pressure field and wind filed data produced using JTWC best track data shows better R2 and NSE values as compared to IMD. Due to this reason pressure field and wind field data produced using JTWC best tack data is used to force the storm surge inundation model to simulate cyclone Amphan. Then water levels at fours BIWTA water level stations are calibrated and validated. Finally inundation scenario is also compared with two inundation maps for the validation of the inundated area produced by the storm surge inundation model. One is produced by NAWG by survey during Ampahn and another one is inundation map produced using Sentinel-1 SAR images during Amphan. There are some findings related to challenges and different aspects in different stages of storm surge modelling in a data scarce region like Bangladesh that will help researchers to help storm surge inundation related studies in future