American Journal of Water Resources, 2018, Vol. 6, No. 2, 53-61 Available online at http://pubs.sciepub.com/ajwr/6/2/2 ©Science and Education Publishing DOI:10.12691/ajwr-6-2-2 Morphological Study of Surma River: A Geographic Investigation Syed Tawhidur Rahman*, Nusrat Jahan Koley, Shetu Akter Department of Geography and Environment, Shahjalal University of Science and Technology, Sylhet - 3114 *Corresponding author: [email protected] Abstract Surma, which is the lifeline of Sylhet region, travelling a long way from the Manipur state of India, divided at the border of Bangladesh and amongst them, one of flow northward that bestow prosperity. Commerce was flourished on the bank of the river and now-a-days, it is remaining as the livelihood center of this region. This river isn’t only important for human beings but also for biodiversity which lived in surrounding environment. So, it is needed to learn the morphological characteristics through geographical investigation to adapt with the change of river. To find out present condition, an experimental method was conducted on selected nine cross-sectional points of the Surma river. For trend analysis, selected Landsat and DEM images were purchasing from authentic sources. As well as depth and discharge data (1990 to 2014) were collected from BWDB. Remote sensing and geographic information system provide tools for quantitative and qualitative river morphological analysis. From the analysis of data, it was found out that the depth and gradient of river was high in upstream that gradually decreases towards downstream. The condition was reverse for the width. This investigation supported the theory that upper portions are highly active in the case of erosion and which particles were victimized, flows with the force of water and bit by bit deposited at the down areas. As the depth was shallow at the down part, width of the valley was comparatively higher than upper. From the trend analysis, it was obtained that depth as well as discharge rate of Surma were showed decreasing trend. The SI was respectively high at Up and low at middle part of the river. And the channel was tending to migrate on the northward. Keywords: morphology, Surma River, water discharge, geographic investigation, channel pattern. Cite This Article: Syed Tawhidur Rahman, Nusrat Jahan Koley, and Shetu Akter, “Morphological Study of Surma River: A Geographic Investigation.” American Journal of Water Resources, vol. 6, no. 2 (2018): 53-61. doi: 10.12691/ajwr-6-2-2. with the northern branch being called the Surma River and the southern the Kushiyara River. This is where the river 1. Introduction enters the Sylhet Depression (or trough) which forms the Surma Basin. The Kushiyara receives tributaries from the The Bengal delta which has formed by the combined Sylhet Hills and Tripura Hills to the south, the principal action of three major rivers including the Ganga-Padma, one from the Tripura Hills being the Manu. The Kushiyara the Brahmaputra and the Jamuna comprises 100,000Km2 is also known as the Kalni River after it is joined by a of riverine, flood plain and deltaic environment [1]. These major offshoot (distributaries) from the Surma. When the three great rivers along with other trans-boundary and Surma and the Kushiyara finally rejoin in Kishoreganj inland rivers about 230 in numbers [2]. Every year District above Bhairab Bazar, the river is known as the flooding causes severe damage to the crops and other Meghna River. The Surma passes through many haors [6]. valuable properties. Another disaster is the River bank The Surma River conveys a part of the Barak river erosion which causes tens of thousands of people discharge and the discharges of its right bank tributaries. homeless every year [3]. Surma is the longest river of At the bifurcation near Amalshid, the channel bed of the Bangladesh. The river Surma after originating from the Surma is higher than that of the Kushiyara; as a result the bifurcation of the Barak river at Amalshid runs towards inflow from the Barak River into the Surma is less. It west through Sylhet until it meets the Balui river and varies from about 40% of the Barak discharge at high collects inflow from the 56% area of the Surma basin stages to zero at the low stages [7]. which occupies most of the southern slope of Shillong Surma is the third largest river in the Meghna region Platueau and receives world’s highest rainfall [4]. The which was originated from the hilly river Barak that Surma is a meandering and dynamic river. It has travelled divided near Zakiganj upazila of Sylhet district, flows 215 km inside Bangladesh from the Indian boundary up to through Sylhet and Sunamganj district and finally fall into Sunamganj district [5]. From its source in the Manipur Meghna river. Total catchment areas are approximately Hills near Mao Songsang, the river is known as the Barak 8176 square kilometers (BUET) respectively stretched in River. At the border with Bangladesh, the river divides India and Bangladesh. American Journal of Water Resources 54 As morphological shape of Barak river started shifting after the year of 1960s, Kushiyara river received major discharge of water flow. Surma received only 20 percent water flow. Due to this fact, river bed is silted up with a consequence of decreasing the depth at a large context. Because of Surma river holding capacity of hilly rain water with turbulent flow is decreased, water surges overtop on both banks and disastrous erosion occurs in adjacent community. The most important feature of this river is its catchment area included Southern facing slope of Shillong Plateau in Meghalaya, Cherapunji, which are the wettest part of the Earth. During the period of monsoon, inflows of the river was responsible to create flash flood with peak flows that causes continual erosion and sedimentation which affect river banks stabilization, navigation, flood control, fisheries, and agriculture. Due to the action of hydraulic and geomorphological forces on river bed and banks, an alluvial river always changes its flow path and shape. So, it is important to understand the characteristics and nature of such type river. This study has been conducted to investigate the morphological features of Surma river as well as trying to build a relationship between various variables, so that easily can identified which are the most dominated items. Along with that figure out the morphological trend which may be helpful for overall management and design a framework to prevention of loss that might be occur because of chronical shifting characteristics. 2. Aim and Objectives 1. To investigate the present morphological conditions of Surma river for the selected cross-sectional areas. 2. To assess the morphological trend of Surma river. Figure 1. Surma River (Source - USGS NASA (LP DAAC), Prepared by 3. To analyze the relationships between various Author) morphological features of Surma river. Figure 2. Map of the Study Area (Source - USGS NASA (LP DAAC, Prepared by Author) 55 American Journal of Water Resources Figure 3. Framework of the Study 3. Methodology like width, depth, discharge etc. that certified about the fit of data. In order to determine the morphological characteristics, first of all the river was divided into three segments from where necessary data was collected during April 2015 to 4. Results and Discussion June 2015. First one is situated in Borodesh Bazar near Kanaighat A Physio- morphological survey that has been conducted at upazilla as an upper stream. Then Tuker bazaar area, three Stream Zone of Surma Rivers represents a partial condition which is fall under Sylhet Sadar, was selected as of the River. This paper deals with river depth, water middle portion. Third point situated between two Upazilla velocity, discharge amount and the width of the Surma River. named Sunamganj and Doarabazar. Then, each area had been divided into three categories randomly for the 4.1. Present Morphological Condition purpose of rational analysis. From those points, width and depth was measured manually as well as velocity that In this regard, general morphological characteristics of helped to evaluate the discharge of Surma river. Along this river was discussed. with that, on the basis of points location, sinuosity of the river was determined by stream gradient and sinuosity 4.1.1. Depth of Surma River calculator tool. In this regard, flow line was assessed In the downstream zone has lower depth (8.80 meter) through detrend tool that was under by River Bathymetry than the others two zones. The upper stream zone (15.27 m) Toolkit (RBT) and after that used this calculator which is is deeper than the middle stream zone (10.65 m). The average mainly based on python script. Satellite images of Landsat depth of total sampled area is 11.58 meter. This depth has - Operational Land Imager (OLI) (2015), Thematic been measured in 2015. But average depth of these three Manager (TM) (1990 and 2000) and Enhanced Thematic points was 13.86 meter that has been measured in 1993. Mapper Plus (ETM+) (2010) were available to study the These values clearly indicate that river beds of three different shifting of channel. On the time of using images, it was stream zones are going through a tremendous change. Due assured that data was georeferenced in a proper way to various sediment materials that coming from upper stream which lead to less error and better interpretation. In this zone increased the rate of deposition in the downstream contrast, ERDAS Imagine 2015 and ENVI 5.1 were used which lead to decrease the depth of river at that portion for processing satellite images. Arc Map 10.5 had been and increased the chance of inundation. From the investigation, used for analyzing river bank data.