Surface water bodies are one of the irreplaceable natural resources for human survival, and it extensively reduces with increasing the world population. This study modeled the spatiotemporal changes of land use / land cover (LULC) and identified the most influential LULC parameters, which contributes in the reduction of surface water bodies using the Landsat 4 and 5 TM and Landsat 8 OLI images (1992-2017). Rajshahi City Corporation is situated in the Northern piece of Bangladesh. A maximum likelihood supervised images classification algorithm was used for detection of changes in LULC. Matrix union technique was used for identifying the prominent LULC parameters. About 14% of water bodies were filled up in twenty-five year (1992-2017) due to rapid urbanization in Rajshahi City Corporation area. This study can provide an essential move towards necessary actions for preservation of surface water bodies to maintain the ecological balance and environmental sustainability.
Fluvial processes such as bank erosion plays an important role to change the channel stability of the Torsa River in the downstream region. The present study was focused on stream stability assessment of the Torsa River. The study area is situated between the downstream of the Jaldapara Reserve Forest and confluence of Kaljani River. Data of different parameters about 64 bank segments of the Torsa River were prepared using the field work techniques for assessing the stream bank conditions using lateral, vertical and overall reach stability models. The individual results of BEHI and NBS ratings show that out of 64 bank segments only 35 and 19 bank segments classified in higher categories. Overall lateral stability analysis shows that most of the sample bank segments are in an unstable condition. All bank segments are vertically unstable and degrading. Overall reach stability analysis shows widespread instability. BEHI and NBS results are almost similar for most of the bank segments and therefore, BEHI and NBS can be suitable bank erosion hazard predictive models in the study for channel stability analysis.
Flood frequency analysis is one of the techniques of examination of peak stream flow frequency and magnitude in the field of flood hydrology, flood geomorphology and hydraulic engineering. In the present study, Log Pearson Type III (LP-III) probability distribution has applied for flood series data of four sites on the Mahi River namely Mataji, Paderdi Badi, Wanakbori and Khanpur and of three sites on its tributaries such as Anas at Chakaliya, Som at Rangeli and Jakham at Dhariawad. The annual maximum series data for the record length of 26-51 years have been used for the present study. The time series plots of the data indicate that two largest ever recorded floods were observed in the year 1973 and 2006 on the Mahi River. The estimated discharges of 100 year return period range between 3676 m3/s and 47632 m3/s. The return period of the largest ever recorded flood on the Mahi River at Wankbori (40663 m3/s) is 127-yr. The recurrence interval of mean annual discharges (Qm) is between 2.73-yr and 3.95-yr, whereas, the return period of large floods (Qlf) range from 6.24-yr to 9.33-yr. The magnitude-frequency analysis curves represent the reliable estimates of the high floods. The fitted lines are fairly close to the most of the data points. Therefore, it can be reliably and conveniently used to read the recurrence intervals for a given magnitude and vice versa.
Thirty (30) groundwater samples have been collected during Pre-monsoon season-2015 to analyze the groundwater quality of Shikrapur and Talegaon Dhamdhare area. Maps were prepared for major physicochemical elements in groundwater and geomorphologic aspects using GIS and Remote Sensing techniques. Trend in cations is Na>Ca>Mg>K while in anions is Cl>HCO3>NO3>SO4. The average, Na+Ca representing 61.37% of total cations denoting major supply from weathering of plagioclase feldspar while Ca+Mg values, 67.92 % of cations contributed from olivine and pyroxene. Anions like Cl, SO4 and NO3 in groundwater is contributed from anthropogenic activities. The results were compared with WHO norms and found higher values for Electrical Conductivity (EC), Calcium (Ca), Potassium (K), Magnesium (Mg), Chloride (Cl) and Nitrate (NO3). Other elements show low to optimum values indicating good quality for drinking purposes, excluding some pockets from lower reaches. Regular quality monitoring for groundwater with rainwater harvesting is suggested to improve the quality of groundwater in the region.