The 2 nd Annual Gobeshona Conference Future Changes of Flash Flood in the North East Region of Bangladesh using HEC-HMS Modeling

Transcription

1 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

2 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 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.

3 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

4 Study Area : North East Region of Bangladesh 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)

5 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,

6 Outline of the Work

7 Necessary Sources of the Study Source Resolution/Period DEM HydroSHEDS (source: 30s Stream Network L use map HydroSHEDS GlobCover (source: 30s 1:5,000,000 Soil data map FAO (source: 1000 m /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

8 Basin 22 sub basins 11 gauge stations

9 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

10 Meteorological Time Series Manual addition of- Names of rainfall station Depth weights (method of Thiessen polygon) Time weights

11 Table: Initial values of Parameters Elements Parameters Initial For all Sub basins For all Reaches Lag time, tp (hr) 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)

12 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) ing coefficient, Cp Initial (m 3 /sec) 100 Recession constant Initial Abstraction, Ia to Muskingum K (hr) Muskingum X

13 Flow ( cumec) Calibration 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 RSR PBIAS

14 Flow ( cumec) Validation Observed Simulated 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 RSR PBIAS

15 Simulated Flow ( cumec) Graphical Representation of Simulated & Observed Flow R² = Observed Flow (cumec) Year 2005

16 Simulated Flow ( cumec) Graphical Representation of Simulated & Observed Flow R² = Observed Flow (cumec) Year 2006

17 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) Jul Jun Aug 28 days earlier 32 days earlier 18 days later Changes of Flow at Bhairab Bazar

18 Flow ( cumec) Comparison of Flow Hydrograph at Bhairab Bazar Flow ( 2005) Flow (2030) Flow (2050) Flow (2080) 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

19 Changes of Flow in Netrokona Region Year 2005 Year 2030 Year 2050 Year 2080 SUBBASIN Drainage Area (KM2) (Cumec) (Cumec) (Cumec) (Cumec) W Jul Aug Aug Aug W Jul Oct Jun Jul W Jul Oct Jun Jul

20 Changes of Flow in Sylhet Region Year 2005 Year 2030 Year 2050 Year 2080 SUBBASIN Drainage Area (KM2) (Cumec) (Cumec) (Cumec) (Cumec) W Jul Jun Aug Aug W Jul Apr Jun Jun W Aug Jun Jun Aug W Jul Oct Jun Jul W Jul Apr Jun Jul

21 Changes of Flow in Sunamganj Region SUBBASIN Drainage Area (KM2) (Cumec) Year 2005 Year 2030 Year 2050 Year 2080 (Cumec) (Cumec) (Cumec) W Jul Aug Aug Aug W Jul Jun Aug Aug W Jul Aug Aug Aug W Jan Apr Apr Jan W Jul Oct Jun Jul W Jul Oct Jun Jul

22 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.

23 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

24 References AQUASTAT, Ganges-Brahmaputra-Meghna River Basin. Regional Report, Water Report 37 JRCB., 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., Evaluation Guidelines for Systematic Quantification of Accuracy in Watershed Simulations. Transactions of the ASABE, American Society of Agricultural Biological Engineers. Vol. 50(3), pp