Workshop on Disaster Prevention/Mitigation Measures against Floods and Storm Surges in Bangladesh on 17-21 November, 2012, in Kyoto University, Japan Component 2: Flood disaster risk assessment and mitigation Saiful Islam Anisul Haque Institute of Water and Flood Management (IWFM) Bangladesh University of Engineer and Technology (BUET)
Activities Review of floods in Bangladesh, sources, warning and dissemination system. Flood hazard and risk mapping. Improving warning system for internal flood due to extreme rainfall events and coastal flood due to storm surge. Assistant local communities in building awareness against flooding.
Types of floods in Bangladesh Normal Reverine flood during monsoon season (June-September). Internal excess rainfall flood during monsoon season. Flash flood during pre-monsoon season (March- May) occurred mainly in the northeast pars of the country. Costal floods due to cyclonic storm surges and tides during pre-monsoon and post-monsoon (October-November).
Improving flood hazard risk maps and danger level
Riverine (monsoon) Floods Ganges-Brahmaputra-Meghna (GBM) Basins and River Network
72 hrs Advance Flood forecasting by FFWC, BWDB Maps of stations where flood forecast information are generated by FFWC A typical 48 hours flood inundation maps of Bangladesh
Flood inundation map of Bangladesh using MODIS images generate by IWFM
Flood hydrographs and water levels Water level (m, PWD) 24 20 16 12 8 4 RHWL DL RHWL DL RHWL DL (a) Flood 1988 Brahmaputra (at Bahadurabad) Ganges (at Hardinge Bridge) Meghna (at Bhairab Bazar) Water level (m, PWD) 24 20 16 12 8 4 RHWL DL RHWL DL RHWL DL (d) Flood 2007 Brahmaputra (at Bahadurabad) Ganges (at Hardinge Bridge) Meghna (at Bhairab Bazar) - 1-May 16-May 31-May 15-Jun 30-Jun 15-Jul 30-Jul 14-Aug 29-Aug 13-Sep 28-Sep - 1-May 16-May 31-May 15-Jun 30-Jun 15-Jul 30-Jul 14-Aug 29-Aug 13-Sep 28-Sep
Flood forecasting and danger levels Danger level: A stage of river for a location above which water is consider as flood. It is not clear about the basis of setting this level by BWDB. It needs to revisit to set up appropriate danger level considering the flood risks. Improving flood warnings and dissemination. Developing flood hazard and risk mapping.
Internal Flooding a major problem due to heavy rainfall events [Source: The Daily Star, http://www.thedailystar.net/story.php?nid=3883 ]
Rampura temporary pump station shows negligible impact on drainage congestion
Improving weather forecasting for heavy monsoon rainfall
Weather Research and Forecasting at BUET using WRF The Weather Research and Forecasting (WRF) Model is a meso-scale numerical weather prediction system designed to serve both operational forecasting and atmospheric research needs. Open source software developed by NCAR, USA It can be used for Real time Weather forecast Cyclone Tracking and Storm Surge prediction Seasonal forecasting Climate Change predictions
WRF Experiment Domain for Bangladesh Domain: Lat. (7 S 43 N), long. (68 112 E) Resolution: 30 meter No. of vertical levels: 27 Time Steps: 150 sec Horizontal grid scheme: Arakawa C grid Time integration scheme: the Runge-Kutta 2nd and 3rd order
Boundary Information PBL Scheme: Eta operational scheme. Radiation Scheme: RRTMG scheme. LBC and SST: NCEP/NCAR GFS forecast Microphysics: Simple ice Cumulus parameterization scheme: Kain-Fritsch scheme Soil Model: Multi-layer soil model (MODIS)
Cyclone Thane on December 2011 Thane became a Very Severe Cyclonic Storm during December 28, 2011. 3 min sustained wind speed 140 km/h (85 mph) Thane then made landfall early on December 30, on the north Tamil Nadu coast between Cuddalore and Pondicherry and rapidly weakened into a depression. Thane had left at least 46 dead in Tamil Nadu and Pondicherry.
Forecasting Cyclone Thane WRF model was able to capture Cyclone Thane. Start Time: 24 December 2011 at 6 UTC End time: 30 December at 6 UTC Time steps: 150 seconds
Real Time 5-day Non-operational Forecasting http://www.buet.ac.bd/iwfm/weather
Location-wise Forecast
Improving forecasting of storm surge for the cyclone over Bay of Bengal
Storm Surge modeling using coupling of WRF and FVCOM Finite-Volume Coastal Ocean Model is recently developed to use for generating flows. FVCOM is a prognostic, unstructured- grid, finite - volume, free- surface, threedimensional (3-D) primitive equations ocean model developed originally by Chen et al. (2003a). This model will be used to compute storm surge height by coupling WRF model.
Unstructured grid and bathymetry over the Bay of Bengal
Advanced Circulation (ADCIRC) model of NOAA predicting Storm surge of SIDR
Thank you