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Background: Bangladesh is known as a deltaic plain at the confluence of the Ganges, Brahmaputra and Meghna River Basins (GBM) and their tributaries. The rainfall pattern of northeastern part of Bangladesh is changing along with the discharge pattern of Surma River. In this study, the changes in precipitation of Sylhet and river discharge of Surma River and the relationship between them were investigated. The study emphasizes on the influence of climatic component (rainfall) on the hydro-characteristics of river. The time series data from 1973 to 2016 (44 years) of rainfall and river discharge of Surma River were collected and analyzed. The basic hydro-characteristics, including arithmetic mean, variability, skewness, distribution type, persistence, dependence, trend, and correlation have been studied through various statistical methods, including coefficient of variation, Mann-Kendall test, Sen's slope estimator, and Pearson's coefficient of correlation.Results: The rainfall trend shows moderate year-to year variability although there is an indication of declining rainfall trend. As with rainfall, the river discharges show moderate year to year variations that are related to the variability in rainfall. The decreasing rate is 1.53 mm for rainfall and − 1.51 m 3 /s for discharge (Mann-Kendall test). The rainfall was increasing from 1973 to 1989 but after 1990 it is reduced. The mean discharge of Surma River was 845.99 M 3 /s. The rainfall started to fall down extremely from 1990 to 2016 but before that the rainfall showed an increasing trend with modest slope. It is possible that the declining trend in rainfall observed in Sylhet is a result of climate change which causes the declining of Surma River discharge. Over these 44 years analysis, the rainfall and discharge shows a very decreasing trend and both rainfall and discharge were highly related for most of the time. Conclusion:In conclusion, it can be noticed that the rainfall in Sylhet has been reduced from the time 1973 to 2016 which directly affects the discharge of Surma River. Consequently, this result might be the indication about the effect of climatic change in the local as well as global level. which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.

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This study aims to analyze the pattern of bank erosion and simulate the physical aspects of vulnerability in the lower Meghna River, Bangladesh using remote sensing (RS) and geographic information systems (GIS). The physical factors of vulnerability were analyzed using GIS-based Structured Query Language (SQL). A questionnaire survey, GPS survey and field observation survey were conducted for collecting the primary data in the study area. The secondary data were mainly satellite image collected from the United States Geological Survey (USGS) website. Using time series Landsat images (MSS, TM and OLI-TIRS), this study analyzed 36 years of erosion and accretion process in the Mehendiganj Upazila region from 1980 to 2016. The result indicates that an enormous amount of land (4470.47 ha) was submerged by the river and average land loss rate was 124.18 ha/year. The study quantifies the number of vulnerable households beneath the present condition and how much it will be altered after a positive/negative change with the factors of vulnerability related to the households. Simulation data reveals that under the present physical condition, 43.88% of households were identified as severely vulnerable. The output of this study can be used in the classification of vulnerable households and for the improvement of the physical infrastructure development process near the erosion prone areas, also helps to mitigate environmental disaster in the developing countries.

Bangladesh is a region that is vulnerable to climate change. In this study, the influence of rainfall on river morphology and river discharges was investigated. The morphological analysis of the Surma River was carried out using GIS. Rainfall of Sylhet over 44 years(1972–2016) was analyzed. Annually 434.099 mm rainfall precipitated in Sylhet. The mean annual rainfall from 1972-to 2016 shows a little decreasing trend. 845.99 M3/s of water was discharged on average from the Surma river annually. Over these 44 years, erosion and deposition show a very decreasing rate with a very steep slope. The sinuosity index of the Surma River varies from 1.32 to 2.29. The total erosion is strongly related to annual mean rainfall (r=0.939), which greatly affects the total river erosion. 88% of erosion depends on the annual mean rainfall (r2=0.88). The r between mean annual rainfall and total deposition is 0.919, which presents a very strong positive relationship. More than 80% of the erosion can be explained by rainfall. According to the percentage of r2, about 89.8% of the variables of deposition can be explained by rainfall if other factors remain constant. The river deposition and erosion are very highly dependent on river discharge. The Surma river’s annual mean discharge and rainfall are strongly correlated (r = 0.69), which indicates that the discharge of the Surma river is highly dependent on the surrounding area’s rainfall. To conclude, it can be noted that the Sylhet rainfall decreased from 1972 to 2016, which affected the Surma river’s morphology directly due to climate change.