Flood Characteristics of th Haor A                                                     Fl d Ch     t i ti     f the Ha Are...
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Poster egu 2012


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Poster egu 2012

  1. 1. Flood Characteristics of th Haor A Fl d Ch t i ti f the Ha Area i B gl d h and the P t ti l I in Bangladesh d th Potential Impact of t f Climate Change Cli Ch g A. Su a a d B. A Suman1 and B Bhattacharya2 attac a ya suman_fs@y suman fs@y yahoo.com yahoo com and B Bhattacharya@unesco ihe org B.Bhattacharya@unesco ihe.org B.Bhattacharya@unesco-ihe.orgAbstract Climate Change I Cli t Ch Impacts on flooding in the Haor area t fl di i th HHaors are large saucer-shaped flood plain depressions located in the North-East region of Bangladesh During the dry season Haors are used for agriculture and saucer shaped North East Bangladesh. nduring the rainy season they are used as fisheries The hydrograph characteristics such as the rising curve gradient (K) flood m fisheries. (K), magnitude ratio (M) and time to peak Three GCMs CSIRO Mk3 5, ECHam5 and GCMs- CSIRO-Mk3.5, Table 1: Percentage of precipitation increase in(TP) are assessed for different river floods. Using these characteristics an integrated flood index is developed. The flood index indicates the relative overall severity MIROC3.2 (medres), MIROC3 2 (medres) and IPCC scenarios ( ) the B1 and A2 scenarios with different GCMs GCMs.of fl di f flooding. Th fl d i d i th hi h t i th J d k Ri The flood index is the highest in the Jaduka River (fl d i d 21) and th l (flood index d the lowest i th S t in the Someswari Ri i River (fl d i d 8) Cli t change scenarios are (flood ind 8). Climate h dex i B1 and A2 were used to construct theconstructed f t t d from th results of th the lt f three G General Ci l ti M d l (GCM ) ECh 5, CSIRO Mk3 5 and MIROC3 2 ( d ) wit th B1 and A2 IPCC scenarios f l Circulation Models (GCMs)- ECham5, CSIRO-Mk3.5 d MIROC3.2 (medres) it the ( th d i for GCM model % of precipitation increase future scenarios All of them predict an scenarios.2050 and 2090 Th pre-monsoon fl d peak di h g and water l d 2090. The p flood p k discharge d t level are predicted t i l p di t d to increase considerably. A fl d index i d id bly flood ind is developed f 2050 with th l p d for ith the B1 A2 increase in precipitation (Fig 4(a)) The (Fig. 4(a)).ppredicted hydrograph It is predicted that the flood severity will increase for most of the rivers in the Haor area . hydrograph. y g p p y area. pre-monsoon precipitation is predicted to 2050 2090 2050 2090 CSIRO-Mk3.5 CSIRO Mk3 5 5.3 3 6.6 66 8.4 84 16.4 16 4 increase considerably compared to the ECHam5 2.8 28 11.8 11 8 3.4 34 17.8 17 8 monsoon precipitation (Fig 4(b)) 4(b)). MIROC3.2(medres) ( ) 10.0 15.8 12.0 19.2Case study: RC t d Ruvubu catchment b t h t Flood Characteristics i th H Fl d Ch t i ti in the Haor areaHaor area of Bangladesh g The deeply flooded Haor area was studied using 1 D and 2 D hyd dy Th d ply fl d d H t di d i g 1-D d 2-D hydrodynamic models i th MIKE i d l in the environment. environment Rivers were modelled with a 1 D model and Haors were m 1-D modelled with a 2 D model The 1 D 2-D model. 1-D model was calibrated with respect to the water level gauge observation The flood inundation extent from g g ns. ns the 2 D model was calibrated using remote sensing images 2-D images. (a) (b) The Th results showed th t th lt h d that there are mainly t i ly two types f i typ of rivers i th d ply fl d d area. S in the deeply flooded Some Fig. 4. Fig 4 (a) Rainfall pattern of 2010 and simulated rainfall pattern of 2050 with different GCM models and the A2 scenario (b) P ipi i changes with different GCM models and the A2 scenario for 2050 d h i ( ) Precipitation h g i h diff d l d h i f 20 0 are slow response rivers with a flood response p p time of 10 to 20 days and others are quick response rivers with a flood response time of 2 to The t d Th study reveals an i l increase i peak di h in k discharge and average di h d discharge i th in the 5 days (Fig 2) (Fig. 2). major rivers i th H j i in the Haor area of B gl d h (Fig 5) Th pre-monsoon fl d peak f Bangladesh (Fig 5). The p ( ) flood p k (a) ( ) discharge d di h g and water l t level i predicted t i l is p di t d to increase considerably i comparison t th id bly in p i to the An integrated flood index was developed with monsoon peak and water level Different GCM models expect an increase in the p level. p hydrograph characteristics of the rising curve pre-monsoon pre monsoon peak water level by 0 4 m to 1 6 m in the Haor area in 2050 with the 0.4 1.6 gradient (K) flood magnitude ratio (M) and time to (K), A2 scenario Fig 6 shows comparison of flood index of 2004 and 2050 scenario. Fig. 2050. peak (TP). The flood index indicates the relative overall severity of fl di i diff ll it f flooding in different rivers (Fi t i (Fig. 3( ) (a). (b) Fig. Fig 3 (a) Flood inde of different rivers at the deeply flooded ex area for 2004 (b) De epth profile of pre-monsoon flooded Haors pre monsoon Fig.1 Fig 1 The study area. area The study shows the Haors are vulnerable to the s Fig. Fig 5 Comparison of the flood hydrograph Fig. Fig 6 Comparison flood index of 2004 pre monsoon pre-monsoon floo ods. ods Seven Haors were inundated for 2004 and a simulated hydrograph with and 2050 during the pre-m pre m monsoon 2004 flood in the deeply different GCM models for 2050 and A2The study area is the North Eastern region of North-Eastern (a) . flooded Haor are Among them f f ea. five Haors were scenario in the Surma RiverBangladesh (Fig 1) There are three types of (Fig. 1).Haors in that area: Foothill and near hill Haor Haor, inundated b a fl d d th of 1 5 t 3 3 and i d t d by flood depth f 1.5m to 3.3m d Conclusions C l iFloodplain Haor and Deeply flooded Haor Haor. flood l ity f 1.2 to 1.3 / fl d velocity of 1 2 t 1 3 m/sec (Fig 3(b)) ( (Fig. 3(b)). ( )) hot spots Bangladesh. ¾ The study identified flood risk hot-spots in the Haor area of Bangladesh The study e e The study reve ls that embankments without d ea eals that e ba k e ts b ithout discharges. ¾ All GCMs predict an increase in pre-monsoon flood peak dischargesTwelve rivers and fifteen Haors of the deeplyflooded Haor area were considered in the breaches reduced fl di g risk i th d ply b h d d flooding i k in the deeply flooded fl d d area. However, t protect th whole d ply Ho , to p t t the h l deeply Acknowledgement:study.study During the dry season farmers cultivate The research was done in collaboration with 1) Institute of Water Modelling (IWM Bangladesh) 2) Center for (IWM, Bangladesh),Boro rice in the Haor area. Pre-monsoon Pre monsoon (b) flooded Haor are it is recommended to raise the ea Environmental and Geographic Information Services (CEGIS Bangladesh) 3) Institute of Water and Flood Management (CEGIS, Management,floods ftfl d often d damage crops i th H in the Haor area. embankment he eight by 1 0 m around some 1.0 Bangladesh University of Engineering and Technology ( Bangladesh). g y g g gy g ) Fig.2: (a) Comparison of hydrograph in the Nawa River at identified Haors (Shanir Haor s Haor, Halir Haor Haor, We k W acknowledge th support of th project M h Fl dH l d the t f the j t MorphoFloodHaorHaors are used as fi h iH d fisheries d i g th wet during the t US and DS during the 2004 flood (b) Comparison of waterp i dperiod. Sonamoral Haor and Pagnar Haor) Haor). level in the Nawa River at US and DS during the 2004 flood2UNESCO-IHE Institute for Water Education, Hydroinformatics Chair Group, Westvest 7 P O Box 3015 2601 DA Delft The Neth Education Group 7, P.O. 3015, Delft, herlands www.unesco-ihe.org/hi www unesco-ihe org/hi1Patuakhali Science and Technology University Department of Agricultural Engineering Dumki Patuakhali 8602 Bangladesh gy University, y p g Engineering, Dumki, Patuakhali-8602, g g g