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    HYDRO-MORPHOLOGICAL ANALYSIS OF TEESTA RIVER USING HISTORICAL DATA AND FLOOD INUNDATION MAPPING USING HEC-RAS 2D MODEL
    (2023-02) ALI, MALIHA; ISLAM, RAFIA
    Bangladesh is situated at the most downstream region of the GBM basin where the major three rivers meet. Only 7 percent of the basin area lies within Bangladesh. Most of the water flowing through Bangladesh is beyond the nation’s control. Besides, owing to flat lowlying geological formation, Bangladesh is a very flood prone country where flood stays for longer period. In the northwest region Teesta is a flashy river in nature for which the water level of river Teesta shows several peaks during the monsoon both at Dalia and Kaunia. During the monsoon, Teesta River overflow its banks. For this severe flooding is caused multiple times by Teesta River during monsoon in Bangladesh. Besides, Teesta is a morphologically active river which shows significant shifting of bankline and change in width over the years resulting from erosion and deposition. Therefore, the study is carried out to understand the hydrological and morphological nature of Teesta River and the flood characteristics of the river using mathematical model. For hydrological analysis, water level hydrograph for Dalia, Kaliganj and Kaunia stations and Discharge hydrograph at Dalia Station is prepared using historical data of daily water level and discharge from 2000-2022 year. Besides flood frequency analysis is also done using Gumbel’s distribution to determine the maximum discharge and water level for a return period of 50 and 100 years. For morphological analysis, planform analysis is done using satellite image to evaluate the bank line shifting and amount of erosion-deposition of both banks of Teesta River for the period 2000-2022. Cross section analysis is done to determine the changes in width of the river and thalweg movement over the year using cross section data from left bank of the river. As a part of the study, flood inundation maps were generated for monsoon season of 2020 using HEC-RAS 2D model. Later, the model generated map is also compared with Satellite based inundation map prepared by FFWC of BWDB. HEC-RAS 2D model is developed and calibrated for the year of 2020 August-September and validated for the year of 2013 August-October with a manning’s roughness n=0.032. Lastly, the model is simulated to generate flood inundation map for Teesta River of 2020 flood to compare it with the actual scenario to understand the model performance.
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    HYDRODYNAMIC AND MORPHOLOGICAL STUDY OF PADMA RIVER USING DELFT 3D
    (2023-02) MURSHIDA, MALIHA; KHATUN, SOMAIYA
    Due to the tendency for erosion and deposition, the Padma, which was once thought to be a mostly meandering stream, is now transitioning into a braided system. In order to determine the Padma River's optimal hydrodynamic and morphological behavior, it is necessary to do morphological analysis. In the process of this research, a two-dimensional model of the river Padma was constructed with the help of Delft3D for the purposes of analyzing the hydrodynamic and morphological behavior of the Padma River in Naria Upazila. The data on water level, discharge, sediment and bathymetry are gathered from BWDB. Time series discharge data is utilized as the upstream boundary and water level data as the downstream boundary for hydrodynamic and morphological computation. The model is simulated for the monsoon season of the year 2021 with Bilaspur Bazar as the upper-southern boundary and Islampur functioning as the lowersouthern boundary. The accuracy of the model is calibrated by comparing it to the water level that was actually present at Mawa in June of 2021. After the calibration process is complete, the model is evaluated at the same location during the months of September of the following year (2021). Once they have been calibrated and validated, the variation of hydrodynamic properties is investigated, including changes in velocity and discharge as well as variations in water level. Then, the morphological characteristics, such as the rate of sediment transport and cumulative erosion/deposition at vulnerable sections, are evaluated. Results show that in September, the velocity is observed to be at its highest around the river's lower middle and narrow parts. It is observed that the velocity of the river and the rate of sediment movement are highly correlated. When the critical high discharge and water level were used, the velocity was greater than the unsteady model simulation, where the monsoon data of 2021 was used. So, the erosion and deposition was greater for steady case
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    EROSION-ACCRETION ANALYSIS OF A TIDAL REACH OF THE MEGHNA ESTUARY
    (2024-03) HRIDITA, NAFISA NURAEEN; ELMA, SAJIDA FATIMA
    The Meghna Estuary, situated in Bangladesh, is renowned for its dynamic morphological characteristics, influenced by sedimentation from the GangesBrahmaputra-Meghna Delta and intense tidal currents. This research delves into the erosion-accretion dynamics within the Meghna Estuary, particularly focusing on the reach between Urir Char and Char Elahi. Through a comprehensive study utilizing remote sensing, GIS analysis, and field surveys, this research aims to assess morphological changes and sediment transport patterns over thirty years. The study reveals significant erosion-accretion fluctuations, with accretion rates exceeding erosion rates, leading to the formation of new landmasses and alterations in the estuarine landscape. The image analysis results revealed that over the past thirty years (1993-2023), the study area experienced a total erosion of 1422.86 ha and 3658.47 of accretion. Analysis of sediment concentration profiles indicates a sediment surplus system, characterized by accretion-prone areas. The findings underscore the critical role of sediment dynamics in shaping estuarine morphology and highlight the potential of remote sensing and GIS techniques in monitoring and managing coastal environments so that appropriate measures or structures can be built to protect the island.
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    GROUNDWATER QUALITY ANALYSIS OF MANIKGANJ DISTRICT USING WATER QUALITY INDEX AND PRINCIPAL COMPONENT ANALYSIS
    (2023-02) BHUIYAN, MUHAMMAD JUNAID; MAHBUB, RAYUN
    Water Quality Index (WQI) is one of the simplest, most understandable and effective way to determine overall quality of drinking water as well as water used for other purposes. A study was attempted to assess the spatial variability of groundwater quality index of Manikganj district of Bangladesh. For this purpose, 31 water samples were collected and analyzed for potential sources and of contamination. pH, Total Dissolved Solids (TDS), Electric Conductivity (EC), Total Hardness (TH), Total Alkalinity (TA), Iron (Fe), Manganese (Mn), Sulphate (SO₄²- ), Chloride (Cl− ) and Turbidity were measured for calculating WQI. Their mean values were 7.05, 313.07 mg/L, 625.62 µS/cm, 207.35 mg/L, 214.57 mg/L, 5.0 mg/L, 0.093 mg/L, 14.16 mg/L, 104.38 mg/L and 62.06 respectively. The obtained values of WQI were distributed spatially through mapping using IDW interpolation via ESRI ArcGIS software. These values were categorized as excellent, good, poor, very poor, and unfit for every purposes. The WQI values ranged from 7 to 683 with an average value of 134.19. Among the 31 samples, 29.03% were excellent quality, 38.71% were good quality, 9.67% poor quality, 12.9% very poor and 9.67% were unfit for all purposes. The Kaiser–Meyer–Olkin test was 0.747 confirming that the dataset was sufficient for component analysis. The entire dataset could be represented by two components which accounted for 63.53% of the total variance of the dataset. Through PCA the influential contaminants came to light informing that naturally occurring Fe and Mn contaminations resulted in most of the pollution. Through this study, it can be proved that Spatial mapping and PCA are effective tools for determining ground water quality. The results of this study can be used to improve the current water quality situation of Manikganj district and ensure higher quality water resources for the citizens of this district.
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    STUDY ON ENVIRONMENTAL IMPACTS OF E-WASTE
    (2023-02) RAHMAN, SHAMTA NUR
    The study is about the impacts of e-waste on our environment. We have done this research through statical data analysis. Here we had a questionary survey. There we set 10 questions. Among these 9 were with multiple options and it was about their opinion. We got 500 responses from this survey. People were highly interested in this survey. They gave their opinion based on their depth of knowledge, experience and conscience. Based on their opinion and collected information from online as secondary data we have come to a single or multiple solution. Ewaste is polluting our environment since it includes many harmful substances. Our environment is negatively impacted in numerous ways by it. They are burned, buried, and poured into waterways. These pollutants may also find their way into water, air, earth, and food. Either directly or indirectly, poor countries may be affected by e-waste pollution. So, it needs to be appropriately disposed of. Surface water is becoming contaminated as a result of e-waste. It affects aquatic life and leads to various public health issues. Therefore, we shouldn't dump electronic waste into water bodies. When e-waste is dumped on the ground, poisons seep into the earth, polluting the water supply and harming the plants that thrive there. Therefore, it shouldn't be dumped on the ground. When e-waste is treated using techniques like open-air burning, toxic chemicals are released into the environment. It contributes to global warming, acid rain, air pollution, and a variety of respiratory illnesses. Therefore, this approach shouldn't be used. We are able to confirm that e-waste has a great deal of harmful effects on the environment based on the questionary survey and the information we acquired online as secondary data. E-waste has a significant negative impact on water, the atmosphere, and land. E-waste pollutes our environment and prevents the sustainable growth of our society.
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    MORPHOLOGICAL ANALYSIS AND BANKLINE SHIFTING OF THE PADMA RIVER NEAR NARIA UPAZILA USING REMOTE SENSING AND GIS TECHNIQUES
    (2023-02) MIM, FATEMA RAHMAN; AREFIN, MD. MUKTADIR
    A river is defined as any naturally occurring body of water that moves along a specified course. Erosion, sediment transport, and sediment deposition are the three most essential processes taking place in river channels. The geography of Bangladesh is largely shaped by its rivers. The Padma is one of the longest rivers in Bangladesh and it goes all the way across the nation. The river's structure is quite dynamic. Currently, riverbank erosion in the Padma River is a significant concern. Naria, located in the Shariatpur district was selected as the research area. This study aims to assess the morphological alterations along the Padma River in the adversely devastated Naria upazila. Satellite pictures from the past 50 years (1972-2022) were evaluated. In this paper, image processing was accomplished with the use of technologies like EarthExplorer and Geographic Information Systems (GIS). The images of Landsat were collected with the use of EarthExplorer. The results of this research demonstrate that calamities such as riverbank erosion-deposition occur as a result of flooding, sediment transport, and human activity. Massive erosion-deposition was observed in Naria upazila, particularly for the floods that occurred in 1987, 1988, 1998, 2004, and 2007, which were assessed in this study. This catastrophe had a serious influence on a great number of people's lives. It has caused a lot of people to lose their homes and jobs and end up on the streets. Residents in this region are leaving their homes to find better living circumstances due to a lack of sanitation, clean water, healthcare and education. Because of this, the government must promptly adopt strategies that supplement current systems. To stop riverbank erosion and protect people and their way of life, it's important to use both non- structural and structural methods.
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    FLOOD SUSCEPTIBILITY MAPPING USING MACHINE LEARNING
    (2024-02) SHADID, MAKHZUM KHAN
    This study presents an innovative approach to flood susceptibility mapping in the Sylhet district of Bangladesh, integrating Geographic Information System (GIS), machine learning techniques, and the Analytic Hierarchy Process (AHP). The methodology involves the use of Digital Elevation Model (DEM) data, Landsat imagery, and soil data, complemented by a Python-based rainfall prediction model. The study employs AHP to weigh various floodcausing criteria and incorporates machine learning for predictive accuracy in rainfall forecasting. Two separate models are developed using random forest regressor for Sylhet sadar and kanaighat and the model had a R square value of .6677 and .5953 respectively with normalized root square mean error of 0.07 and 0.096. The Flood susceptibility map with prediction model shows an improvement in predicting vulnerable flood zones in comparison to the flood susceptibility map using historical rainfall data.
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    A STUDY ON HYDRO-MORPHODYNAMIC BEHAVIOUR OF THE KIRTANKHOLA RIVER USING DELFT3D MODEL
    (2024-03) RAHMAN, NOMAN; SADIA, NUZHAT FARHAT
    The Kirtankhola River is a meandering river in Bangladesh's southern region where the second-largest river port in the country is situated. It has a tendency to erode and its flow contains huge amounts of sediment. In order to identify the hydrodynamic alterations and related morphological changes of the Kirtankhola River, a hydromorphological study of the river is essential. In this study, hydrodynamic and morphological behaviour of Kirtankhola River is assessed by developing a two - dimensional model using Delft3D and Image Analysis using ArcGIS respectively. The selected reach for developing the Delft3D model is approximately 19.2 km from the downstream of Arial Khan River (u/s) to Barishal Launch Ghat (d/s). The model is calibrated against the observed water level at Barishal Launch Ghat for the months of June-September, 2010. Then it is validated at the same place for the months of June-September, 2022. After calibration and validation, the model is simulated for both of the years and used to study the hydrodynamic and morphological behaviour of the study area. Following that, an assessment is made of the morphological features, including quantification of bed shear stress and critical shear stress. In order to conduct image analysis of the study area, we obtained Landsat images spanning 23 years, divided into 3-year intervals: 2000, 2003, 2006, 2009, 2012, 2015, 2018, 2021, 2023. All the images have been downloaded from USGS EarthExplorer. The findings from the image analysis indicate significant accretion and erosion in different regions, with accretion facilitating Chars' growth while erosion contributes to bank shifting. Erosion occurs annually, with 2009 being the most significant. Area-1(at Char Monai near At Hazar) experienced significant accretion, while Area-2(opposite bank of Char Baria Riverside) experienced erosion, surpassing accretion by nearly fourfold. Major erosion occurred in 2012-2015 in Area-2. The bed shear stress data from 2010 and 2022 was analyzed using five observation points on the Delft3D model. In 2010, the maximum stress was 0.5377 N/m2 , and the average shear stress was 0.3277 N/m2 . In 2022, the maximum stress was 0.9315 N/m2 , and the average shear stress was 0.7603 N/m2 . The critical shear stress was 0.185 N/m2 . It is evident from the model that the maximum and average bed shear stress exceeded the critical shear stress, indicating erosion is occurring. However, some contradictions between the outputs of the ArcGIS study and the Delft3D model were found due to the inadequacy of the required data. Apart from all the limitations, we hope our findings from this assessment will be helpful to understand the overall hydro-morphodynamic behaviour of the river and suggest possible future development works to be implemented on this river through further modifications.
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    EFFECT OF LAND USE AND LAND COVER CHANGES ON SOIL EROSION USING REVISED UNIVERSAL SOIL LOSS MODEL
    (2024-02) ISLAM, MD. SHAKIRUL
    The burgeoning urban landscape of Dhaka, Bangladesh, grapples with the escalating challenge of soil erosion, contributing to land degradation within the city. This study employs the RUSLE model integrated with Remote Sensing and GIS techniques to scrutinize the intricate dynamics of soil erosion within the urban fabric of Dhaka. The distinctive geography of Dhaka, along with its quick development and fluctuating climate, highlights the city's susceptibility to soil erosion. The study finds that the average rate of soil erosion within the study area is around 26.59 tons/ha/year. These findings indicate that there are geographical variations associated with particular land use patterns. The dynamics of soil erosion are largely dependent on the parameters of the RUSLE model. The R factor, which indicates the erosivity of rainfall, varies from 974.53 in 1990 to 867.17 in 2020. The slope characteristics-indicating LS factor falls between 0 and 2.25, while the K factor is recorded at 0.0189. Significant fluctuations in the cover management factor (C), which shows a value of 0.93 in 1990, 1.03 in 2000, 0.98 in 2010, and 0.934 in 2020, as well as the support practice factor (P), which spans from 0.2 to 0.934, are discernible and provide concrete proof of changing land use and conservation strategies. Changes in the climate throughout time may have an impact on the variations in the R factor. The basic characteristics of the soil that affect its erodibility have stayed mostly constant. This stability may be explained by a consistent soil composition, restricted land use changes that don't significantly alter the properties of the soil, efficient conservation techniques that reduce the risk of increased erodibility, the inherent resistance of some soils to change, or regional variations in how land use changes affect erodibility. Slope features can change as a result of infrastructure initiatives, urban development, or construction operations altering the natural topography. Changes in vegetation and land cover are suggested by variations in the C factor. Deforestation, urbanization, and afforestation activities can all have a big impact on soil management and cover. Changes in the P factor may be related to how well and how widely conservation measures are used in the research region. Lower P values may result from increased use of terracing, contour farming, or other erosion control techniques. A dynamic pattern within the research area is revealed by looking at the historical evolution of soil erosion rates. The rate of soil erosion peaked in 1990 at 31.39 tons/ha, indicating a high degree of susceptibility. The rates decreased in the following years, reaching 26.78 tons/ha in 2000 and 24.65 tons/ha in 2010. The rate significantly decreased over the ensuing ten years, reaching 23.54 tons/ha in 2020. These results suggest that land usage, conservation methods, or other environmental conditions may change in the future. Improved land management techniques, greater public knowledge of soil conservation, or changes in land use that lessen erosion susceptibility could all be contributing factors to the observed drop in soil erosion rates over time. The research is useful in a number of important areas. By exploring the intricacies of urban soil erosion in Dhaka, it offers a thorough grasp of the variables affecting this occurrence, such as crop management, conservation techniques, slope characteristics, rainfall erosivity, and soil erodibility. Policymakers and urban planners working on sustainable development and environmental preservation in Dhaka will find this information to be quite helpful. The results might also have an impact on the region's soil fertility. By eliminating the top layer of fertility, soil erosion can affect soil fertility. Therefore, it is important to understand the dynamics of soil erosion. The results of this study could be useful in developing ways to reduce soil erosion, maintain soil fertility, and increase agricultural output in Bangladesh, a country whose economy is mostly dependent on agriculture. This study makes contributions to environmental preservation, urban planning, and maybe agricultural sustainability within the particular setting of Dhaka, Bangladesh.
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    A GIS BASED DRASTIC MODEL FOR ASSESSING GROUNDWATER VULNERABILITY IN TONGI, GAZIPUR DISTRICT OF BANGLADESH
    (2024-03) RAHMAN, MD. MAHMUDUR; REZA, SYED AHNAF
    Groundwater resources in Tongi are currently threatened by many garments, dyeing, paper and pulp, wood, tannery, dairy, poultry, fishery, chemical and textile industries. Many of these industries release untreated heavy metals, solid and liquid wastes consisting of cadmium (Cd), chromium (Cr), and lead (Pb), threatening water resources. A model-based groundwater pollution risk assessment was conducted to address these issues. The most sophisticated among the vulnerability assessment techniques is the GIS-based DRASTIC model. The model considers parameters like depth to the water table, net recharge, aquifer and soil media and hydraulic conductivity, which were collected from Bangladesh Water Development Board (BWDB), Geological Survey of Bangladesh (GSB). This study determined the net recharge from specific yield using bore log data and water table fluctuation. The average net recharge has been calculated as 359 mm/year and varied from 105 to 614 mm/year. Determination of the DRASTIC index involves multiplying each parameter weight by its site rating and summing up the total. The higher index values symbolise a greater risk of GW pollution or greater aquifer vulnerability. Finally, for the year 2013 and 2019, two groundwater vulnerability map were developed for each year for the study area using the DRASTIC Index and GIS mapping. One of the maps was developed following typical DRASTIC weightage suggested in the model and the other map was developed by modifynig weightage for the study area. In 2013, the DRASTIC index values vary from 104 to 156 according to model suggested weightage and it was reclassified into two groups of moderate, and highly vulnerable zones. About 21% of the area is highly vulnerable and 79% area is moderately vulnerable to groundwater contamination. On the other hand, modified weightage DRASTIC index values vary between 113 and 183 and it was reclassified into two groups of moderate and high vulnerable zones. About 3.5% area is moderately vulnerable, 96.5% area is highly vulnerable. In 2019, the DRASTIC index values vary from 91 to 137 according to model suggested weightage. The whole study area is susceptible to moderate vulnerablility to groundwater contamination. On the other hand, modified weightage DRASTIC index values vary between 95 and 164 and it was reclassified into two groups of moderate and high vulnerable zones. About 20.6% area is moderately vulnerable, 79.4% area is highly vulnerable. The modified weightage map has more vulnerbility compared to typical map. Thus, the model provides important information that could be useful to city planners and decision-makers for the establishment of ETPs and putting restrictions on further industrialisation in the vulnerable zones.