Journal of Modern Science and Technology

Vol. 6. No. 1. March 2018 Issue. Pp.113-123

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Assessment of Hydro-Morphological Change of Surma-Kushiyara River System

Md. Sabbir Mostafa Khan 1* and Purnima Das2

Bangladesh stands on a thick alluvial deposit. It is the result of deltaic activity of the Ganges and the Brahmaputra. These main rivers, their tributaries and distributaries control its hydrological and morphological behavior. The morphology of a river channel is a function of a number of processes and environmental conditions, including the composition and erosion possibility of the bed and banks (e.g., sand, clay, bedrock).This study analyzes the changing trends of hydrological and morphological parameters of Surma and Kushiyara river system. The field of research is focused on rive hydrology and river morphology.

Keywords: Erosion; Deposition; Sedimentation.

1. Introduction Channel morphology is the result of mutual interactions of four broad categories ofvariables such as fluid dynamics (which include velocity, discharge, roughness and shear stress), channel characteristics or channel configuration (e.g. channel width, channel depth, channel slope, channel shape, channel pattern etc.), sediment load and Bed and bank materials (composition and character i.e. coarse, fine, medium etc.). The theory of river sedimentation and morphological processes are among the most complex and least understood phenomena in nature (Alam et al. 2007). In this case, measurement of sediment concentrations at certain location would depend of course on local flow conditions, but also on conditions upstream and on the flow history. Field surveys, with the purpose of understanding the process, would then include very large amount of information. To collect the data and analyze it would be a very costly and time-consuming task. In that respect, mathematical modeling is an alternate tool to understanding the detail physical processes in the nature. Mathematical modeling has been introduced as a tool to interpret the information provided by the field data in an integrated way. The mathematical models enable interpolation and extrapolation in space and time based on the observations from the field and on the understanding of the physical processes and their interaction to the extent that of its incorporation in the model. Various 1-D, 2-D and 3-D hydrodynamic and sediment modules are in use in water engineering sector. In this case the Analysis process includes statistical analysis of hydrological data like water level and discharge, morphological analysis by using HEC-RAS 1D model and cooperation of GIS and HEC-GeoRAS. The application of GIS and HEC-GeoRAS ______________________

1 Dr. Md. Sabbir Mostafa khan,

Professor, Department of Water Resources Engineering, Bangladesh

University of Engineering and Technology (BUET), Dhaka, Bangladesh, Email: sabbirkhanbuet@gmail.com 2

Purnima Das, Graduate Student, Department of Water Resources Engineering, Bangladesh University of Engineering and Technology (BUET), Dhaka, Bangladesh, Email: pinkiwre10@gmail.com

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helped in calculating Bank-line shifting of the study area. The Unsteady models were run for the year 2012 both for the Surma and Kushiyara river system. The Manning’s n value for Surma River was 0.03. In addition, for Kushiyara River the value was 0.013. The model is used to investigate the pattern of the cross-section. The sediment transport model was run for 2012 year and was used to investigate the pattern of the cross-section. The model shows remarkable changes in the bed level in the case of Kushiyara River and shows no such changes in the Surma River. Moreover, the model can be used for predicting the changed pattern of the cross-sections using the predicted discharge data of the Surma-Kushiyara river system. In this paper, Section 1 deals with Introduction while Section 2 focuses on Literature Review and Section 3 contains Methodology. Results and discussion are provided in Section 4 and Conclusion is in Section 5.

2. Literature Review Surma-Meghna River System is one of the three major river systems of Bangladesh. It is the longest river (669 km) system in the country. It also drains one of the world's heaviest rainfall areas (e.g. about 1,000 cm at Cherapunji, Meghalaya, India). East of Brahmaputra-Jamuna River system is Surma-Meghna River System. The Surma originates in the hills of Shillong and Meghalaya of India. The main source is Barak River, which has a considerable catchment in the ridge and valley terrain of Naga-Manipur hills bordering Myanmar. Barak-Meghna has a length of 950 km of which 340 km lies within Bangladesh. On reaching the border with Bangladesh at Amalshid in Sylhet district, Barak bifurcates to form the steep and highly flashy rivers Surma and kushiyara. Surma flows west and then southwest to Sylhet town. From there it flows northwest and west to Sunamganj town. Afterward it maintains a course southwest and then south to Markuli to meet Kushiyara. The joint flow goes upto Bhairab Bazar as the Kalni. Environmental Impact Assessment case study of Surma –Kushiyara River has been studied for this analysis. Morphological analysis of Surma- Kushiyara is a very new study. Due to great changes experienced by the river system, it has been subject to investigation and studies. Gupta(2012)described the effect of tectonics and meandering in the moderately paced avulsion of the Ganga-Bhagirathi system to the present Ganga-Padma using the Landsat program. The study revealed that gradient advantage and bend upstream of bifurcation does not result in modeled avulsion as observed in small and medium rivers and large rivers in tectonically active regions. A tectonic uplift results in a modeled avulsion period consistent with historical observations. The study also showed that backwater effect and high sediment mobility keepboth bifurcated channels active to attain an Ana branching pattern. The backwater effect was found to play an important role for sustaining the anabranch plan form of many of the largest rivers of the world by the said study. Reza (2016) expanded on the theory of the fluvial morphological characteristics of the Padma River in northwestern Bangladesh. Morphological and morpho-dynamic maps of the Padma River were prepared using remote sensing techniques. Sinuosity ratio, braided index and island percentage of the study area were estimated for the years of 1977, 1989 and 2000respectively. Outcomes of this study obtained from investigating satellite remote sensing imagery provide valuable information about the bank erosion, channel shifting of fluvial morphology of the Padma River, and recommended some protective measures. Hossain et al. (2013) assessed morphological changes of the Ganges River using satellite images. Using

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eight dry season satellite images of Landsat MSS (1973-1984), Landsat TM(1993-2003), and IRS LISS (2009), this study assessed morphological changes of the Ganges River within Bangladesh. The results indicate that both the left and the right banks of Ganges have changed significantly due to varying erosion and accretion rates that had occurred. On a whole, the left bank was more prone to accretion while the right bank to erosion. Baca (2015)described the process due to the nature of the Ganges River, integration of cultural connectivity is becoming ever more prominent. Climate change has also exposed the need for the creation and revising of trans-boundary water sharing agreements. Be it through the interference of flow due to dams, the unhealthful interaction between the river and the floodplain, or the increased variability of the river due to climate change, the river, and its management is more tumultuous than ever. The theory of the part of the old Brahmaputra River, off taking from Jamuna is located under the district of Mymensingh and partially under the district of Tangail, Jamalpur, Sherpur and Netrokona (Alam et al. 2007). Analyzing the image of part of the old Brahmaputra River among the year 1997 and 2004, it is found that Significant changed has been occurred in north east part of Mymensingh sadarupazila and less change is found in the lower part which is close to the Mymensingh town where China Bangladesh Friendship Bridge (Shambhuganj Bridge) has been constructed. Transportation of sediment is the major contributing factor of morphological changes.Rouf (2011)described the process of hydro-morphological characteristics and water quality parameters of Shitalakhya River. In this study, the variation of cross sectional area, maximum depth and top width at different sections for different period was observed and it was found that rivers show negligible shifting of channel from one bank to the other. This is the theory usedon the river Ganga at Varanasi for calculating amount of meandering in the form of change of sinuosity at two consecutive bends (Singh, SM 2014). For this purpose10 years of satellite imagery data has been analyzed of the Ganga River, using Arc GIS combined with historical data. The result shows that sinuosity varies from 1.66 to1.26 and silt deposition of two bends varies from 4.52 to 3.14 and 3.4 to 2.42 respectively. Laz (2012)described the process of Simulation of sediment transport rate at the river Jamuna and variation of bed level along the river by using a two dimensional morphological model. Non- cohesive sediment transport module of Delft 3D Flow is used for the simulation used in the study. Result shows that erosion takes place in the channel bed, the deposition mainly takes place on the adjacent char areas, and both its width and area are increased. It is also evident that the channel has beenshifted westwards of the reach due to shifting of the bank line of the river and the zones of higher velocity has higher sediment transport capacities causing more erosion. Begum (2009) described the process of the siltation observed in Mongla portand developed a hydrodynamic and a sediment model of Pasur river system using HEC-RAS. From the model it was found that, both siltation and erosion occurred in the Mongla port area and erosion was prominent at the downstream of Mongla port (near downstream of Danger Khal). Based on the study of the literature review this study will focus on the hydro morphological change of the Surma-Kushiyara River system by HEC-RAS model and GIS software.

3. Methodology For the study different sets of data named level) and topographic data as Digital Elevaup the model preprocessing GIS

DEMs are increasingly used for visual and mathematical analysis of topography landscapes and landforms, as well as comprises of a resolution of 30m x 30m. The elevation of the DEM has been measured with respect to the mean sea level. All the data in the DEM have been projected on to the Bangladesh Transverse Mercator (BTM).

Figure 2: Clipping the DEM of Sylhet Division

After taking the DEM of Bangladesh,The DEM of Sylhet is clipped from the whole DEM using the Clipping Tool in ArcToolbox. After clipping the DEM, it Raster to TIN tool is to create a Triangdoes not deviate from the input raster by more than a specified Z tolerance. It is done by using the Raster to TIN tool in the Arc Toolbox.

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For the study different sets of data named hydrologic data (discharge and water level) and topographic data as Digital Elevation Model (DEM) data were used.

GIS data was necessary.

Figure 1: Study Area

DEMs are increasingly used for visual and mathematical analysis of topography landscapes and landforms, as well as modeling of surface processes. comprises of a resolution of 30m x 30m. The elevation of the DEM has been

e mean sea level. All the data in the DEM have been projected on to the Bangladesh Transverse Mercator (BTM).

2: Clipping the DEM of Sylhet Division

Bangladesh, the Shape file of Sylhet division is superposed. The DEM of Sylhet is clipped from the whole DEM using the Clipping Tool in ArcToolbox. After clipping the DEM, it is converted to the TIN format. The purpose of the Raster to TIN tool is to create a Triangulated Irregular Network (TIN) whose surface does not deviate from the input raster by more than a specified Z tolerance. It is done by using the Raster to TIN tool in the Arc Toolbox.

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hydrologic data (discharge and water tion Model (DEM) data were used. To set

DEMs are increasingly used for visual and mathematical analysis of topography modeling of surface processes. The data

comprises of a resolution of 30m x 30m. The elevation of the DEM has been e mean sea level. All the data in the DEM have been

the Shape file of Sylhet division is superposed. The DEM of Sylhet is clipped from the whole DEM using the Clipping Tool in Arc

. The purpose of the ulated Irregular Network (TIN) whose surface

does not deviate from the input raster by more than a specified Z tolerance. It is

Figure

For the preparation of channel To create 1D geometry we used the bathymetric grid only and excluded the nearby floodplain. The goal of this section was to develop the spatial data required to generate a HEC-RAS import file with a 3sections. This extraction comprisesriver centerline, cross-sections, upstream and downstream side of the flood p

Figure 4: Drawing River CenterlineCut Lines for

For setting up an unsteady hydrodynamic model, a flow hydrograph of discharge versus time has been considered as Upstream Boundary Condition. In case of the Surma River, Kanaighat (SW266; Lat. discharge station. Flow hydrograph of the year 2013 of this station has been used as Upstream Boundary Condition. The flow hydrograph of station Sheola (SW173; Lat. 24.887°, Long. 92.190°) has been used as Upstream Boundary Condition of the Kushiyara River. Flow hydrograph of thUpstream Boundary Condition.

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ure 3: Transforming DEM to TIN

or the preparation of channel geometry, preprocessing was done in HECTo create 1D geometry we used the bathymetric grid only and excluded the nearby floodplain. The goal of this section was to develop the spatial data required to

RAS import file with a 3-D river network and defined 3sections. This extraction comprises of several steps. These are development of a

sections, riverbanks, and flow path lines as shape files of and downstream side of the flood plain respectively.

Drawing River Centerline, Bank Lines, Flow Path and Cross

Cut Lines for Surma River

For setting up an unsteady hydrodynamic model, a flow hydrograph of discharge versus time has been considered as Upstream Boundary Condition. In case of the Surma River, Kanaighat (SW266; Lat. 25.004°, Long. 92.270°) is the upstream

hydrograph of the year 2013 of this station has been used as Upstream Boundary Condition. The flow hydrograph of station Sheola (SW173; Lat. 24.887°, Long. 92.190°) has been used as Upstream Boundary Condition of the Kushiyara River. Flow hydrograph of the year 2011 of this station has been used as Upstream Boundary Condition. A stage hydrograph of water surface elevation versus

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geometry, preprocessing was done in HEC-GeoRAS. To create 1D geometry we used the bathymetric grid only and excluded the nearby floodplain. The goal of this section was to develop the spatial data required to

network and defined 3-D cross development of a

flow path lines as shape files of

Cross-Section

For setting up an unsteady hydrodynamic model, a flow hydrograph of discharge versus time has been considered as Upstream Boundary Condition. In case of the

°) is the upstream hydrograph of the year 2013 of this station has been used as

Upstream Boundary Condition. The flow hydrograph of station Sheola (SW173; Lat. 24.887°, Long. 92.190°) has been used as Upstream Boundary Condition of the

e year 2011 of this station has been used as A stage hydrograph of water surface elevation versus

time was used as the downstream boundary condition.Sunamganj Station (SW269; Lat. of the Model. Stage hydrograph of the year 2013 of Sunamganj station was used as a Downstream Boundary Condition.(SW270; Lat. 24.691°, Long. 91.390°) has been used as Downstream Boundary Condition of the Kushiyara River. Stage hydrograph of the year 2011 of this station was used as a Downstream Boundary Condition.

Figure 5: Surma River Schematic in HECRAS Geometry Editor

For Surma-Kushiyara river systemcalibrate the Kushiyaraand Surma2014 has been used to validate value of 0.030 for main channechannel of Kushiyara River have been fixed.

Figure 6:Calibration of the Kushiyara River (‘n’ value 0.013)

0.001.002.003.004.005.006.007.008.009.00

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Calibration graph of 2011 for the Kushiyara

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time was used as the downstream boundary condition. For the Surma Sunamganj Station (SW269; Lat. 25.071°, Long. 91.410°) is at the downstream end of the Model. Stage hydrograph of the year 2013 of Sunamganj station was used as a Downstream Boundary Condition. The stage hydrograph of Markuli Station (SW270; Lat. 24.691°, Long. 91.390°) has been used as Downstream Boundary

ition of the Kushiyara River. Stage hydrograph of the year 2011 of this station was used as a Downstream Boundary Condition.

River Schematic in HECRAS Geometry Editor

river system, the data of year 2011 and 2013 has been used to and Surma River respectively and the data of year 20

been used to validate Kushiyara and Surma River System0.030 for main channel of Surma river and n' value of 0.013

iver have been fixed.

Calibration of the Kushiyara River (‘n’ value 0.013)

DATE

Calibration graph of 2011 for the Kushiyara

Observed Water Level(m)

Simulated water level (m)

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For the Surma River, s at the downstream end

of the Model. Stage hydrograph of the year 2013 of Sunamganj station was used as The stage hydrograph of Markuli Station

(SW270; Lat. 24.691°, Long. 91.390°) has been used as Downstream Boundary ition of the Kushiyara River. Stage hydrograph of the year 2011 of this station

River Schematic in HECRAS Geometry Editor

been used to year 2012 and

. Finally, `n' 0.013 for main

Calibration of the Kushiyara River (‘n’ value 0.013)

Observed Water Level(m)

Simulated water level (m)

Figure 7: Calibration of the Surma River (‘n’ value 0.03)

Finally, `n' value of 0.030 for main channemain channel of Kushiyara River have been fixed.

Figure 8: Validation of the Kushiyara River (‘n’ value 0.013)

0.00

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Calibration graph of 2013 for the Surma

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Validation graph of 2012 for the Kushiyara

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Calibration of the Surma River (‘n’ value 0.03)

0.030 for main channel of Surma River and n' value ofiver have been fixed.

Validation of the Kushiyara River (‘n’ value 0.013)

DATE

Calibration graph of 2013 for the Surma

Observed Water Level (m)

Simulated Water Level (m)

DATE

Validation graph of 2012 for the Kushiyara

Observed Water Level(m)

Simulated Water level (m)

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value of 0.013 for

Validation of the Kushiyara River (‘n’ value 0.013)

Observed Water Level (m)

Simulated Water Level (m)

Observed Water Level(m)

Simulated Water level (m)

Figure 9: Validation of the Surma River (‘n’ value 0.03)

Sediment modeling is developed for selected unsteady flow data and sediment data sets required to build up this model.RAS can perform mobile bed sediment routing computations with quasiflow series data. Quasi-unsteady flow data includetemperature file. For sediment transport mechanics, HEdata. In this study, this temperaturthe year of 2012. For sediment transport analysis Selection of maxidepth, Sediment transport formulamethod are required. The observed mam. Therefore, the maximum erodible depth is set tothree boundary conditions: Rating curve, Sediment load series, In this study, equilibrium load is used as boundary condition. After defining geometry file, quasi-unsteady flow and sediment dataJanuary 2012 to 29 Decemberconsidered to show changing bed level of those river.

Figure 10: Eroding Crosssection at Kushiyara River f

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Validation graph of 2014 for the Surma

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Validation of the Surma River (‘n’ value 0.03)

Sediment modeling is developed for selected reach of Ganges Riverflow data and sediment data sets required to build up this model.

RAS can perform mobile bed sediment routing computations with quasiunsteady flow data includes boundary conditions and

temperature file. For sediment transport mechanics, HEC-RAS requires temperature this temperature was assumed as 25 degrees Celsius throughout

the year of 2012. For sediment transport analysis Selection of maximum erodibSediment transport formulas, Sediment sorting method and f

The observed maximum erosion at the thalweg is , the maximum erodible depth is set to 15 m. HEC-RAS model has

Rating curve, Sediment load series, and equilibriumIn this study, equilibrium load is used as boundary condition. After defining geometry

unsteady flow and sediment data, sediment model is simulated for 1st to 29 December 2012. Upstream and downstream stations are

considered to show changing bed level of those river.

10: Eroding Crosssection at Kushiyara River for Upstream Downstream Station

Date

Validation graph of 2014 for the Surma

Observed Water Level (m)

Simulated Water Level (m)

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f Ganges River. Quasi flow data and sediment data sets required to build up this model. HEC-

RAS can perform mobile bed sediment routing computations with quasi- unsteady boundary conditions and RAS requires temperature

Celsius throughout mum erodible

s, Sediment sorting method and fall velocity ximum erosion at the thalweg is less than 15

RAS model has and equilibrium load.

In this study, equilibrium load is used as boundary condition. After defining geometry , sediment model is simulated for 1st

Upstream and downstream stations are

or Upstream and

Observed Water Level (m)

Simulated Water Level (m)

Figure 11: Non-Eroding Crosssection at Surma river for Upstream and

The model result showed remarkable changeand bed remain unchanged for Surma

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Eroding Crosssection at Surma river for Upstream and Downstream Station

The model result showed remarkable changes in the bed level for Kushiyara Rand bed remain unchanged for Surma River.

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Eroding Crosssection at Surma river for Upstream and

in the bed level for Kushiyara River

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4. Results and Discussion Morphological change is a very complex phenomenon and plays an important role in gaining knowledge of rivers. In this study, a successful hydrodynamic and morphological model has been developed and run for Surma and kushiyara River System. Hydrodynamic model of 1D river was established for the Surma and Kushiyara Rivers. Calibration Model for Surma was done for 2013 and for Kushiyara, was done for the year 2011.It was based on the data availability of the rivers. The Calibration Models was established for Surma River for Manning’s n value of 0.03.In addition, for Kushiyara River the value was 0.013. Validation Model for Surma was done for 2014 and for Kushiyara, was done for 2014.It was also based on the data availability of the rivers. Calibration and validation of the model show good correlation between the observed and simulated data. Two unsteady models were run for 2012 year and were used to investigate the pattern of the cross-section. The sediment transport models were run for 2012 year and were used to investigate the pattern of the cross-section. The model result and observed results showed remarkable changes in the bed level of Kushiyara River and no changes in Surma River. Moreover, the model can be used for predicting the changed pattern of the cross-sections using the predicted discharge data of these rivers.

5. Conclusion In this analysis, an average 25degree Celsius temperature was used for a whole year. In practice, however, there is monthly variation of average temperature, so using the same temperature for the 1-year-run is not justifiable. To obtain esult that is more precise HEC-RAS 2-D model or DELFT-3D model can be used. Due to the lack of sediment data, an equilibrium sediment load for all the cross sections was considered. However, in nature sediment load varies according to river velocity, river width, scouring, flow disruption due to structures etc. If proper sediment load series data were available, the model result would be more realistic. The model result showed remarkable changes in the bed level for Kushiyara River and bed remain unchanged for Surma River. This type of model can be used for any other rives. Using this model, we can identify the characteristics of a specific river. This type of morphological assessment studies can give us an idea of proper river training works, constructing embankments where this type of structure is needed and future policy- making. This specific model is different because for the first time it has been constructed for Surma-Kushiyara and it identifies any characteristics required.

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N 2007, ‘Study of Morphological Change of River Old Brahmaputra and Its Social Impacts by Remote Sensing’, Geographia Technica, No.2, viewed 19 February 2017, <http://technicalgeography.org/pdf/2_2007/gt_2_2007.pdf>

Baca, EA 2015, ‘The Ganges River: Symbology, Sustainability, and The Confluence of Cultural and Fluvial Connectivity’, BSc thesis, Texas State University, San Marcos, Texas.

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Begum, M 2009, ‘Study of Siltation of Mongla Port Using HEC-RAS 4.0’,BSc thesis, Bangladesh University of Engineering and Technology, Dhaka, Bangladesh.

Gupta, N 2012, ‘Channel planform dynamics of the Ganga-Padma system, India’, PhD thesis, University of Southampton, Southampton, United Kingdom.

Laz, OU2012, ‘Morphological Assessment of a Selected Reach of Jamuna River by Using DELFT3D Model’, MSc thesis, Bangladesh University of Engineering and Technology, Dhaka, Bangladesh.

Reza, A and Islam, MT 2016, ‘Assessment of Fluvial Channel Dynamics of Padma River in Northwestern Bangladesh’, Universal Journal of Geoscience, Vol. 4, No. 2, Pp. 41-49.

Rouf, T 2011, ‘A Study on Hydro-Morphology and water quality of Shitalakha River’, BSc thesis, Bangladesh University of Engineering and Technology, Dhaka, Bangladesh.

Singh,SM 2014, ‘Morphology Changes of Ganga River over time at Varanasi’, Journal of River Engineering, Vol. .2, Issue. 2, viewed 22 February 2017, <http://www.scijour.com/page/download-KZgwhmHl2eU.artdl>