Keywords: Jamuna River, Hazard, Remote Sensing, NDWI, Erosion, Accretion This paper presents the results of some of the Jamuna River erosional hazards from Bahadurabad Ghat to Bhuapur (near Jamuna Bridge). Results are also presented on the Jamuna River accretion and water discharge. Landsat images from 1977 to 2014 and water discharge data were analysed to find out a relationship between dynamics of erosion and accretion for different time intervals with average annual water discharge. It is clearly established that total amount of erosion and accretion rates varies with different times. The highest erosion rate 21.15 km² year^-1 was observed in the period of 1989-1992 and the highest accretion rate 13.57 km² year^-1 was observed in the period of 1980-1989. The erosion and accretion values fluctuated with increasing average annual maximum water discharge but the difference between erosion and accretion had remained low before water discharge reached to 67000 m³s^-1 and it is estimated higher after crossing annual average maximum water discharge of 67000 m³s^-1. This discharge value also plays an important role on bar development and active channel. It is also observed that unvegetated bar areas remained higher than active channel areas before average annual maximum water discharge reached to 67000 m³s^-1. Finally, all the erosional hazards and accretion values are compared and evaluated to see their influence on the annual discharge.

Sand mining using dredging technology from channel bars is a common technique worldwide. To minimize adverse effects of dredging, geo-engineering nature of the soil should be evaluated before mining. Therefore, the present study deals with the potential risks associated with dredging for mineral sand extraction by analyzing the engineering geological properties of the soil from the Brahmaputra River bar and the surrounding areas, Bangladesh. A detailed engineering geological analysis was conducted using field and laboratory testing methods, including Standard Penetration Tests (SPT), mineralogy, grain size distribution (GSD), California Bearing Ratio (CBR), and direct shear tests. The findings divulge that the soil in the study area is light gray, unconsolidated, moderately sorted, poorly graded, and classified as fine-to-medium silty sand. SPT-based liquefaction potential assessments suggest that the soils are highly susceptible to liquefaction, particularly during dredging or seismic events. The study also identifies the risk of localized slumping and soil instability, which exacerbated by micaceous and quartz-rich sands. The CBR results further classify the subgrade as weak to medium-strong, indicating risks of slumping, erosion, and instability. The non-cohesive granular soil in the area may liquefy or be susceptible to erosion, wave attack, bank slope failures, and seepage development during and after dredging as indicated from GSD and direct shear test results. Thus, proper safety precautions, including soil stabilization techniques, controlled dredging, and slope reinforcement, should be taken before dredging on such river bar to minimize risk. This research offers practical guidance for dredging companies to minimize risks and improve soil stability, contributing to safer and more sustainable river bar dredging operations worldwide.

More than one million Rohingya refugees who fled from Myanmar, had constructed temporary shelters on the loose unconsolidated sandy hills (SC-SM, SP & ML) of Ukhiya-Teknaf region, Cox’s Bazar area, Bangladesh. After entering Bangladesh, the green eco forests of Ukhiya Hills had to be destroyed by cutting trees and hill slopes as they built their shelters which eventually had destructive effects on the ecosystem of Ukhiya Teknaf region. Sands (SP-SM) are mainly uniformly graded and composed of more than 72% to 98 % sand. This research has been carried out to assess the liquefaction potentiality index vales, susceptibility using SPT and risks associated with the Ukhiya hills at different earthquake magnitudes. During earthquake at Magnitudes 5 or greater, Ukhiya hill soils are susceptible to liquefy up to a depth of 12 m.. From the Liquefaction Potentiality Index (LPI) values, risk and sensitivity analysis, it is established that the Ukhiya hills are medium to highly susceptible to liquefy at higher magnitudes (M= 5 or greater). It is also established that north western part of the camp hills are high to very high risk prone areas. Based on Liquefaction Potentiality Index (LPI) values, four seismic risk zones are identified in and around the Rohingya camp area. Some geo-engineering recommendations are also made to reduce this seismic hazard for sustainable community living in the camp area.