The 2 nd Annual Gobeshona Conference 2016 Future Changes of Flash Flood in the North East Region of Bangladesh using HEC-HMS ing By- Shammi Haque 1*, Mutasim Billah 1, Afiya Narzis 2, A.K.M. Saiful Islam 1, G. M. Tarekul Islam 1, Mashfiqus Salehin 1 1 Instituite of Water Flood Management, Bangladesh University of Engineering Technology 2 Department of Civil Engineering, Presidency University
Abstract Bangladesh has been formed as the greatest deltaic plain at the confluence of the Ganges, Brahmaputra Meghna is highly vulnerable to flash Flood. Flash floods may occur at North East region from the surrounding hilly areas for minimum two to three times in a year. In this region, Sunamganj, Habiganj, Netrokona, Kishoreganj Brahmanbaria are highly affected by this phenomenon. Boro rice cultivation is severely interrupted during flash flooding. Cultivation of Aman rice is also hampered due to flash flood triggered heavy rainfall in this region. Hydrologic models have emerged as a basic tool for studying real processes in a watershed hydrologic system systems responding to various climatic forcing. To underst the consequences of Flash flood due to climate changes, hydrological study of GBM basin is required. In this study, as an initial project, a hydrological model of Upper Meghna river basin with drainage area of 70263 km 2 is developed using HEC-HMS. HEC-HMS is a semi-distributed hydrological model that can be used to simulate precipitation-runoff process for both event based continuous precipitation. The Statistical parameters such as NSE, PBIAS, RSR are within range for calibration validation. The model developed in the study can be used as a tool to underst the effects of human intervention changed climatic condition on flash flood in the basin area. Effects of climate changes in North East region are simulated by running the model using the future precipitation data for RCP 8.5 scenario. By using real time precipitation data from WRF model run, this basin model may use as tool for Flash Flood Forecasting purpose.
Background of the Work North East region is highly vulnerable to flash Flood Boro rice cultivation is severely interrupted during flash flooding Cultivation of Aman rice is also hampered due to heavy rainfall which usually trigger flash flood in this region. World s highest precipitation area is situated in the Meghna river basin
Study Area : North East Region of Bangladesh 35000 km 2 (43% of total area) of Uppermeghna basin contributed by Bangladesh (JRCB, 2011) Average annual rainfall 4900 mm (AQUASTAT, 2011) Average annual discharge 4600 Cumec (AQUASTAT, 2011)
Objective of the Work To setup the semi distributed hydrologic model of Upper Meghna basin in HEC-HMS. To calibrate validate the model using flow data at Bhairab Bazar station. To predict future changes in flow at Bairab Bazar To predict future changes in flow at Netrokona, Sunamganj Sylhet region for the year of 2030, 2050 2080.
Outline of the Work
Necessary Sources of the Study Source Resolution/Period DEM HydroSHEDS (source: 30s http://hydrosheds.cr.usgs.gov/index.php) Stream Network L use map HydroSHEDS GlobCover (source: http://due.esrin.esa.int/globcover/) 30s 1:5,000,000 Soil data map FAO (source: 1000 m http://www.fao.org/climatechange/54273 /en/) Precipitation BWDB & NASA 2005, 2006 BWDB 2005, 2006 Future Precipitation RCP 8.5 scenario ( name: CCSM4; Lead Research Center: National Center for Atmospheric Research) 2030, 2050, 2080
Basin 22 sub basins 11 gauge stations
CN Grid Generation L use soil data are used to generate Curve number grid for each subbasin CN (Curve Number) value ranges from 71 to 100
Meteorological Time Series Manual addition of- Names of rainfall station Depth weights (method of Thiessen polygon) Time weights
Table: Initial values of Parameters Elements Parameters Initial For all Sub basins For all Reaches Lag time, tp (hr) 18.86 ing coefficient, Cp 0.5 Initial (m 3 /sec) 10 Recession constant 0.11 Initial Abstraction, Ia 0 Muskingum K (hr) 6 Muskingum X 0.45 Performing Sensitivity Analysis we have made a ranking of parameters for Optimization. 1. ing Co-efficient,, Cp 2. Muskingum K 3. Recession Constant 4. Muskingum X 5. Lag time, tp (hr) 6. Initial Abstraction,, Ia 7. Initial (m 3 /sec)
Parameters Calibration Validation Calibration Point : Bhairab Bazar Calibration Period : 2005 Validation Period : 2006 Elements Parameters Final For all Sub basins For all Reaches Lag time, tp (hr) 91.723-98.488 ing coefficient, Cp 0.10257-0.59279 Initial (m 3 /sec) 100 Recession constant 0.83486-0.91 Initial Abstraction, Ia 0.15488 to 0.15509 Muskingum K (hr) 4.7569-81.685 Muskingum X 0.40689-0.45
Flow ( cumec) 20000 Calibration 10000 Observed Flow Simulated Flow 0 Jan-05 Feb-05 Mar-05 Apr-05 May-05 Jun-05 Jul-05 Aug-05 Sep-05 Oct-05 Nov-05 Dec-05 Time Period (Year 2005) NSE 0.652462 RSR 0.589524 PBIAS 13.69721
Flow ( cumec) 20000 Validation Observed Simulated 10000 0 Jan-06 Feb-06 Mar-06 Apr-06 May-06 Jun-06 Jul-06 Aug-06 Sep-06 Oct-06 Nov-06 Dec-06 Time Period ( year 2006) NSE 0.573603 RSR 0.652991 PBIAS 14.62274
Simulated Flow ( cumec) Graphical Representation of Simulated & Observed Flow 14000 12000 10000 8000 6000 4000 2000 0 R² = 0.9468 0 2000 4000 6000 8000 10000 12000 Observed Flow (cumec) Year 2005
Simulated Flow ( cumec) Graphical Representation of Simulated & Observed Flow 14000 12000 10000 8000 6000 4000 2000 0 R² = 0.9165 0 2000 4000 6000 8000 10000 12000 Observed Flow (cumec) Year 2006
Table: Result using precipitation data of CCSM4 model Year Total Volume of Outflow Value (MM) Percent Change (%) Outflow Value (cumec) Percent Change (%) Occurrence of Date Lag ( Days) 2030 3675.78 64.8 20701.4 84.8 3-Jul 2050 3346.46 50 17356.1 54.9 28-Jun 2080 2982.42 33.7 16007.7 42.9 18-Aug 28 days earlier 32 days earlier 18 days later Changes of Flow at Bhairab Bazar
Flow ( cumec) 25000 20000 15000 Comparison of Flow Hydrograph at Bhairab Bazar Flow ( 2005) Flow (2030) Flow (2050) Flow (2080) 10000 5000 0 1-Jan 1-Feb 1-Mar 1-Apr 1-May 1-Jun 1-Jul 1-Aug 1-Sep 1-Oct 1-Nov 1-Dec Time Period Changes of Flow at Bhairab Bazar
Changes of Flow in Netrokona Region Year 2005 Year 2030 Year 2050 Year 2080 SUBBASIN Drainage Area (KM2) (Cumec) (Cumec) (Cumec) (Cumec) W670 5589.7 1302.6 23-Jul 2186.3 4-Aug 1944.8 10-Aug 2047.7 23-Aug W720 1489.63 520.3 22-Jul 835.8 24-Oct 455.5 16-Jun 391.4 27-Jul W990 4337.7 1291.7 17-Jul 3467.6 24-Oct 1265.4 13-Jun 814.6 27-Jul
Changes of Flow in Sylhet Region Year 2005 Year 2030 Year 2050 Year 2080 SUBBASIN Drainage Area (KM2) (Cumec) (Cumec) (Cumec) (Cumec) W660 8261.8 2333.9 21-Jul 4059.2 8-Jun 3206.1 10-Aug 3201.5 24-Aug W770 1217.35 383.1 22-Jul 433.5 29-Apr 336.1 17-Jun 209.4 29-Jun W780 6215.5 1602.1 30-Aug 1522.2 18-Jun 1271.3 22-Jun 956.3 2-Aug W860 3067.1 1077.1 22-Jul 1381.5 24-Oct 873.3 16-Jun 661.8 27-Jul W1000 6502.4 1893.1 22-Jul 2086.5 29-Apr 1625.4 17-Jun 1248.7 27-Jul
Changes of Flow in Sunamganj Region SUBBASIN Drainage Area (KM2) (Cumec) Year 2005 Year 2030 Year 2050 Year 2080 (Cumec) (Cumec) (Cumec) W600 3072 513.1 21-Jul 2336.1 1-Aug 2149.1 10-Aug 2410 23-Aug W660 8261.8 2333.9 21-Jul 4059.2 8-Jun 3206.1 10-Aug 3201.5 24-Aug W670 5589.7 1302.6 23-Jul 2186.3 4-Aug 1944.8 10-Aug 2047.7 23-Aug W680 190.939 100 1-Jan 125.5 28-Apr 101.4 28-Apr 100 1-Jan W720 1489.63 520.3 22-Jul 835.8 24-Oct 455.5 16-Jun 391.4 27-Jul W860 3067.1 1077.1 22-Jul 1381.5 24-Oct 873.3 16-Jun 661.8 27-Jul
Result Summary In Netrokona, peak discharge will occur during June- October. It may hamper Aman production in this region. In Sylhet, peak discharge will occur during April- October. It may hamper Boro Aman production in this region. In Sunamganj, peak discharge will occur throughout the year. It may hamper Boro Aman production in this region. According to model result, flow at Bhairabbazar will highly increase.
Accuracy of model results or precisions may improve if we can consider- Develop precipitation Grid dataset using Radar rainfall data Parameters adjustment/calibration Long term calibration for better understing of climate change Recent data
References AQUASTAT, 2011. Ganges-Brahmaputra-Meghna River Basin. Regional Report, Water Report 37 JRCB., 2011. Basin map of the Ganges, the Brahmaputra the Meghna river. Reports by Joint Rivers Commission Bangladesh, Bangladesh. Moriasi, D. N., Arnold,.J. G., Van Liew, M. W., Bingner, R. L., Harmel, R. D. Veith, T. L., 2007. Evaluation Guidelines for Systematic Quantification of Accuracy in Watershed Simulations. Transactions of the ASABE, American Society of Agricultural Biological Engineers. Vol. 50(3), pp. 885-900.