Browsing by Author "Tarekul Islam, Dr. G.M."

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Assessment of sedimentation and watershed prioritization using remote sensing and GIS techniques
(Institute of Water and Flood Management(IWFM), BUET, 2022-06-21) Banik, Anik Chandra.; Tarekul Islam, Dr. G.M.
Sedimentation is considered one of the major significant issues for all water development projects, which leads to the reduction of the water storage capacity, hinders the water supply of channels, irrigation, navigation, and damages streams geomorphology, and also limits the reservoir for the fulfillment of the purpose for which it is designed. To ensure the long-term sustainability of any reservoir or dam, it is necessary to scientifically manage soil, water, and vegetation with integrated approaches at the watershed or sub-watershed scale where watersheds need to be considered as planning units for the administrative purposes to conserve land and water resources. The severity of the sedimentation problem can be evaluated by priority delineation of the sub-watershed through the estimation of sediment yield index (SYI), land cover/ land use (LULC), and morphometric parameters analysis. In Bangladesh, the efficient use of water resources in agricultural sectors faces different challenges due to different natural calamities, diversion of river water on the upstream sides, and continuous silting up of different rivers. Approximately 550,000 hectares of land are currently irrigated under 15 large irrigation programs. The Muhuri Irrigation Project (MIP) located in the southeastern region of Bangladesh was designed to serve as supplemental irrigation in the dry season as well as increase agricultural production in this region. But over time, it has lost productivity in terms of both irrigated area and crop intensity due to limited access to the surface and groundwater and poor drainage due to the sedimentation in the rivers and their associate khals. The present study assessed the extent and rate of sedimentation in the reservoir of MIP and investigated the spatio-temporal variations of water storage capacity using Remote Sensing and Geographic Information System techniques. The prioritization map based on the integration of SYI, LULC, and morphometric analysis is also developed for this region. To analyze the sedimentation, water depth, and extract the LULC data, Landsat satellite imageries of 1988, 1998, 2008, and 2020 have been chosen based on the availability of the average dry season maximum water level of five gauging stations during the passage of the satellite over the study area. For the estimation of spatial and temporal variations of water depth, the log-ratio algorithm has been used and the analysis of the result revealed that the areas of bathymetry depths within the range of ≤ 6m, ≤ 9m, and ≥ 9m are1.66 km2,12.93 km2, 4.54 km2 for the 1988 year 0.58 km2,11.24 km2, 4.19 km2 for the 1998 year 2.38 km2, 7.56 km2, 1.27 km2 for the 2008 year and 1.66 km2, 5.76 km2, 3.76 km2 for the 2020 year and the total waterbody decreased to 2.91 km2,4.79 km2,0.036 km2 respectively during1988-1998,1998-2008,2008-2020 period. To estimate the incremental volume of the reservoir, the primordial formula has been used and the results showed that about 5.216 Mm3 volume of sediment is deposited from 1988 to 2020 between 4.44-3.93 m water level. Finally, to estimate the sediment yield between the 1988-2020 period for all Upazilas covered by the study area, an empirical equation of SYI has also been effectively used. According to SYI analysis, Fulgazi and Porshuram Upazila fall under low priority, while Chagalniya and Sonagazi Upazila fall under medium and Feni Sadar and Mirsharai Upazila are under the high priority category. However, morphometric parameters analysis revealed that Chagalniya Upazila falls under low priority and all other Upazilas i.e., Feni Sadar, Fulgazi, Porshuram, Mirsharai, and Sonagazi Upazila fall under the high priority category. Based on the analysis of LULC data, Feni Sadar, Fulgazi, and Mirsharai Upazilas fall in high priority areas, Chagalniya and Parshuram Upazilas fall in medium priority areas, and the rest of Sonagazi Upazila falls in the low priority area. Based on the integration of morphometric, LULC, and SYI parameters, the common sub-watersheds that fall under high priority are Feni Sadar and Mirsharai Upazila whereas Chagalniya, Parshuram, and Sonagazi Upazilas are under low priority, and only Fulgazi Upazila falls under medium priority. However, the results of this study may be useful for the watershed manager, decision-makers, and planners in framing an appropriate plan for the intervention of sustainable management of sediment issues in the region.
Assessment of suspended sediment concentration in the Padma river using satellite remote sensing
(Institute of Water and Flood Management (IWFM), 2016-10) Mashrekur Rahman; Tarekul Islam, Dr. G.M.
Variation of Suspended Sediment Concentration (SSC) is an important parameter in the hydrologic, morphologic and ecosystem studies of large alluvial rivers; especially in the Ganges-Brahmaputra-Meghna (GBM) delta. Traditional in situ measurement of SSC in the large Padma River is challenging in terms of time, cost, skilled personnel and spatial coverage. Moreover, there are limitations in terms of spatial and temporal acquisition of reliable data. Satellite remote sensing offers convenient assessment and spatio-temporal mapping of suspended sediments in large alluvial rivers. This study investigated the applicability of open-access Landsat Enhanced Thematic Mapper (ETM+) images in estimating the SSC of the Padma. Multiple- temporal Landsat 7 ETM+ images were processed to extract Digital Numbers (DN) of pixels corresponding to Bangladesh Water Development Board (BWDB)’s river measurement station, Mawa (SW93.5L). The DNs were converted to radiance and ultimately to top-of-atmosphere (ToA) reflectance. Since mostly clear scenes were used, in situ atmospheric correction was ignored. The ToA values for Landsat-7 bands 1-4, which sense electromagnetic radiation of 0.45-0.52, 0.52-0.60, 0.63-0.69 and 0.76-0.90 μm respectively, were combined with corresponding measured values of SSC, procured from historical data archives of BWDB, between the years 2000 to 2010 for determination of statistical relationship between them. R2 for bands 1, 2, 3 and 4 were 0.64, 0.51, 0.44 and 0.67 respectively. The results from analysis showed that Coefficient of Determination (R2) value of band 4 (Near Infrared) presented the best relationship - therefore chosen as the best SSC indicator. Scatter plot of predicted SSC values from a polynomial equation based on band 4 against in situ values of SSC with 1:1 fit line generated strong positive coefficient of determination of 0.89 and Root Mean Square Error (RMSE) of 88.3 ppm. Using a polynomial model based on the band 4 data, spatial distribution maps of SSC, between the years 2000 and 2010, for monsoon and post-monsoon seasons were demonstrated. SSC levels appeared to be generally higher in monsoon and flood seasons compared to post-monsoon season. However, there were exceptions in this observation too. Rise in discharge, water level and flow velocity increased the overall SSC. During cross-section analysis, it was generally observed that rise in bed level also caused small jumps in SSC levels. Using statistical correlation analysis of measured values of SSC and corresponding in situ values of flow velocity, a logarithmic relationship model was derived. Using these models and SSC spatial distribution maps, spatial variation maps of water flow velocity were created.
Estimating salinity and concentration of chlorophyll-A in the Meghna estuary using landsat imagery
(Institute of Water and Flood Management (IWFM), BUET, 2023-10-07) Zaman, Asaduz; Tarekul Islam, Dr. G.M.
Variations of salinity and Chlorophyll-a concentration are important parameters to identify the possible opportunity for effective management of the Meghna estuary. Traditional in situ measurement systems in the large Meghna estuary are very challenging for real-time monitoring. Moreover, the major limitation in terms of spatial-temporal acquisition of reliable data. The remote sensing technique is a very popular and convenient system for real-time monitoring of salinity and chlorophyll-a concentration. This study investigates the applicability of Landsat TM and Landsat OLI images for estimating these parameters in the Meghna Estuary. Multiple Landsat images from 1989 to 2022 were processed to extract Top of Atmospheric Reflectance (ToA) corresponding data from 18 Bangladesh Water Development Board (BWDB) stations. Since mostly clear scenes were used, atmospheric correction was ignored in situ. For regression analysis, several band or band combinations were investigated to determine which band makes a strong correlation. However, it is noticed that no strong correlation was developed in relation to in situ data and ToA reflectance. Qualitative analysis with Landsat OLI band 4 elucidates that high sediment concentration in the Meghna estuary strongly correlates with the in situ data and ToA reflectance. So, Landsat data is not suitable for salinity mapping in the high sediment concentrate Meghna Estuary. The Inverse distance weighted interpolation method was used to quantify the salinity gradient mapping. Also, investigate the changes in salinity levels for different years and observe that salinity levels increase over the years. The maximum average salinity level was found in 2021 for all eight stations. The highest mean salinity level observed in Tajumuddin station was 7.64 ppt in 2021, which was 0.15 ppt in 2000. Another Chlorophyll-a concentration can also be measured by using a bio-optical algorithm. This analysis was conducted through the conversion of Digital Numbers to remote sensing reflectance. This bio-optical algorithm is a formula of the combination of blue R_rs (490) and green R_rs (555) band from Landsat TM & Landsat OLI. This algorithm elucidated the spatial and temporal variation of chlorophyll-a concentration in Meghna Estuary from 1989 to 2022. Chlorophyll-a concentration is high in the northeastern part of the estuary along the Chittagong coast with an average concentration of 4-6 mg/m3, where the maximum concentration is about 10 mg/m3, and the minimum concentration is 2 mg/m3.
Flood hazard and vulnerability assessment in a riverine flood prone area a case study
(Institute of Water and Flood Management, 2014-09) Sadequr Rahman Bhuiyan, MD.; Tarekul Islam, Dr. G.M.
Khoksabari Union of Sirajganj Town is surrounded by a network of rivers namely the Jamuna, the Bangali and the Karatoa which makes the Union vulnerable to flooding. The present study assesses the hazard and vulnerability of riverine flood in a flood prone area using Remote Sensing (RS) and Geographic Information System (GIS). In the context of flood hazard and vulnerability assessment, flood frequency analysis is carried out to assess flooding for different flood magnitudes. Flood inundation maps are prepared based on DEM and satellite image for different risk elements using ILWIS software. LANDSAT satellite images have been downloaded and used to develop land use map in the study area. The land use map is used for mapping of settlement and fishery by using ILWIS software. The vulnerability function is developed for preparing vulnerability maps for settlements and fisheries. For the development of vulnerability function, depth-damage relation has been developed. Present monetary values of settlement and fishery damage are collected through field survey from actual flood of the study area. Vulnerability functions of settlements and fisheries are used to produce raster-based vulnerability maps. The flood frequency analysis shows that the Pearson Type III distribution is the best fitted distribution for flood frequency analysis in the study area. In 100-year return period flood, inundation percentage of the total agriculture, settlement, fishery and road areas are 48, 35, 53 and 38, respectively. High land (F0) of the study area is 55% which is not much inundated in normal monsoon flood. Vulnerability scaled as low, very low, moderate, high and very high vulnerable settlement areas are found to be 17, 12, 3.43, 1.03 and 1.35 percent, respectively for 100-year flood. These correspond to a maximum of 20%, 40%, 60%, 80% and more than 80% damage of the respective settlement areas. In 100-year flood magnitude, low, very low, moderate, high and very high vulnerable fishery areas are found to be 18, 19, 9, 3 and 4 percent. These correspond to a maximum of 20%, 40%, 60%, 80% and more than 80% damage of the respective fishery areas. The results of this study may be useful for future flood damage mitigation plan in the study area.
Flood hazard and vulnerability assessment in a riverine flood prone area: a case study
(Institute of Water and Flood Management (IWFM), 2014-09) Sadequr Rahman Bhuiyan, Md.; Tarekul Islam, Dr. G.M.
Khoksabari Union of Sirajganj Town is surrounded by a network of rivers namely the Jamuna, the Bangali and the Karatoa which makes the Union vulnerable to flooding. The present study assesses the hazard and vulnerability of riverine flood in a flood prone area using Remote Sensing (RS) and Geographic Information System (GIS). In the context of flood hazard and vulnerability assessment, flood frequency analysis is carried out to assess flooding for different flood magnitudes. Flood inundation maps are prepared based on DEM and satellite image for different risk elements using ILWIS software. LANDSAT satellite images have been downloaded and used to develop land use map in the study area. The land use map is used for mapping of settlement and fishery by using ILWIS software. The vulnerability function is developed for preparing vulnerability maps for settlements and fisheries. For the development of vulnerability function, depth-damage relation has been developed. Present monetary values of settlement and fishery damage are collected through field survey from actual flood of the study area. Vulnerability functions of settlements and fisheries are used to produce raster-based vulnerability maps. The flood frequency analysis shows that the Pearson Type III distribution is the best fitted distribution for flood frequency analysis in the study area. In 100-year return period flood, inundation percentage of the total agriculture, settlement, fishery and road areas are 48, 35, 53 and 38, respectively. High land (F0) of the study area is 55% which is not much inundated in normal monsoon flood. Vulnerability scaled as low, very low, moderate, high and very high vulnerable settlement areas are found to be 17, 12, 3.43, 1.03 and 1.35 percent, respectively for 100-year flood. These correspond to a maximum of 20%, 40%, 60%, 80% and more than 80% damage of the respective settlement areas. In 100-year flood magnitude, low, very low, moderate, high and very high vulnerable fishery areas are found to be 18, 19, 9, 3 and 4 percent. These correspond to a maximum of 20%, 40%, 60%, 80% and more than 80% damage of the respective fishery areas. The results of this study may be useful for future flood damage mitigation plan in the study area.
Investigation into household water supply , sanitation and hygiene of a selected slum with gender perspective
(Institute of Water and Flood Management (IWFM), 2010-04) Safina Naznin; Tarekul Islam, Dr. G.M.
Lack of safe water and basic sanitation is an acute problem for the women and girls who live in poor and overcrowded urban slums in Bangladesh. Access to safe drinking water is a basic human right and essential for achieving gender equality, sustainable development and poverty alleviation. The study intends to identify the household water supply, sanitation and hygienic behavior in a selected urban slum. The study also highlights women contribution in household based water management. From the study it has been found that the water supply and hygienic condition of the study slum are worsening and people, especially women suffer the most due to lack of availability of water. Only 16% household used pipe water for their domestic purposes and remaining 84% used water from open reservoir. Their water storage behavior also unhygienic and 48% water storage pots remains uncovered in the study slum. Only 1% household used fitkiri as a disinfectant. They are habituated to take the contaminated water and suffer from various water-borne diseases including skin diseases, diarrhea, and year round abdominal pains. Moreover, 22% people of the slum area use open latrine besides lake. In addition to this, only 30% respondent use soap after toilet for hand washing and 48% use only water for hand washing. Remaining 22% does not use anything for hand washing. This is in part due to limited awareness or ignorance of the health hazard related to use of unsafe water for household purposes and unhygienic sanitation practices. Although women in Korail slum play a strong role in community mobilization in safe water and hygiene promotion; men, especially the elite and influential people have voice and decision making for water management and operation in this area. Moreover, women are not as widely consulted and women’s priorities and requirements are not given as much attention due to different power relations between women and men. Although women have the opportunity to earn money, they do not have control over their resources. Moreover, they often subject to violence in the study slum. Women’s control over resources is limited because of societal values and practices determining men as the guardians of property, the heads of the household and the decision makers in the public sphere.