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Soil erosion due to anthropogenic interventions is an emerging threat to the south-eastern coastal districts of Bangladesh. In the recent decade, land degradation intensified this process in this region due to the settlement of the Forcibly Displaced Myanmar Nationals (FDMNs) popularly known as ‘Rohingya’, who fled from Myanmar in 2017. The present study has attempted to quantify the regional soil loss (from 2015 to 2020) using the Revised Universal Soil Loss Equation (RUSLE) model. Results showed that the year 2015 and 2020 witnessed the mean soil erosion at a rate of around 58.2 and 59 t ha-1 yr-1, respectively in the Cox’s Bazar district in which 20 - 21% of the study area was highly subjected to soil erosion. But in the Rohingya camps mean soil erosion for these periods is 59 and 78 t ha-1 yr-1, respectively with a cumulative increase of 32%. The sub-districts adjacent to the Rohingya refugee camps (Ramu, Ukhia, and Teknaf) have experienced intense erosion compared to the others. From 2015 to 2020, a large increase of about 4.54 (6%) t ha-1 yr-1 is observed in the Palongkhali union whereas a maximum decrease of about - 8.08 (23%) t ha-1 yr-1 is observed in the Pokkhali union. In Rohingya camps, the worst soil erosion-affected areas are the camps 8E, 10, 14, 15, 16, and 17 having more than 100 t ha-1 yr-1 mean soil loss. Landuse change is the major contributing factor for soil erosion increase from 2015 to 2020 identified from the geographic detector method. The spatial variations are significantly controlled by slope and elevation factors. This work can help to understand the dynamics of soil erosion and the knowledge can be used for conservation planning in the Cox’s Bazar and Rohingya camp areas.

Rainfall-induced landslides seriously threaten hilly environments, leading local authorities to implement various mitigation measures to decrease disaster risk. However, there is a significant gap in the current literature regarding evaluating their effectiveness and the associated community risk perception. To address this gap, we used an interdisciplinary and innovative approach to analyse the slope stability of landslides, evaluate the effectiveness of existing structural mitigation measures, and assess the risk perception of those living in danger zones. Our case study focused on the Kutupalong Rohingya Camp (KRC) in Cox’s Bazar, Bangladesh, which is home to over one million Rohingya refugees from Myanmar. Although various structural and non-structural countermeasures were implemented in the KRC to mitigate the impact of landslides, many of them failed to prevent landslides from occurring. We utilised a variety of methods from the physical sciences, including the infinite slope, limit equilibrium (LEM), and finite element (FEM) approaches, to calculate the factor of safety (FoS) for specific slopes. Additionally, in the social sciences domain, we conducted a questionnaire survey of approximately 400 Rohingya participants to assess the community’s perception of the interventions and the degree of disaster risk. Our findings indicated that slopes with a gradient greater than 40° were unstable (FoS 2). The slopes were found to be stable for lower slope angles but unstable for higher slope angles (> 50°) and increased overburden loads (50–100 kN/m2). Different mitigation measures were tested on the identified unstable slopes to assess their effectiveness, but the results showed that the countermeasures only provided marginal protection against landslides. Survey results revealed that at least 70% of respondents believed that concrete retaining walls are more effective in reducing landslide occurrence compared to other measures. Additionally, about 60% of the respondents questioned the reliability of the existing structural mitigation measures. The study also found that the cohesion and friction angle of lower sandstone and the cohesion of upper soil layers are important factors to consider when designing and implementing slope protection countermeasures in the KRC area.

The Forcibly Displaced Myanmar Nationals (FDMN), historically known as ‘Rohingya’ who fled the 2017 ethnic atrocities and genocide in the Northern Rakhine State of Myanmar, took shelter in Cox’s Bazar District of Bangladesh. The camp network, known as Kutupalong Rohingya Camp (KRC), is situated in the tectonically active tertiary hilly terrain. The KRC has been experiencing hydrometeorological hazards, where landslides are frequent. This study investigated the slopes’ geological condition, engineering properties and human interventions, which influence the landslides. The exposed slopes were relatively high (> 10 m) and steep ranging from 40° to 60° that have numerous polygonal tension cracks and fissures. From the geological and geotechnical aspects, there are three successive units of slope materials: (1) residual soils of sandy silt with clay, (2) highly weathered silty sandstones and (3) shale/clay with silt and fine sand intercalations at the bottom of the slopes. Field observations revealed that most slope failures occurred in the residual soil and weathered silty sandstone units. The residual soils have a bulk density of 1.49–1.97 g/cm3, a liquid limit of 25–48%, a plasticity index of 5–16% and an undrained shear strength of 23–46 kPa. The silty sandstones have a bulk density of 1.44–1.94 g/cm3, an internal friction angle of 34°–40° and a cohesion of 0.5–13 kPa. The mineralogical composition determined by the X-ray diffraction shows low clay mineral content, which does not affect landslides. However, the slope geometry, low shear strength with strain softening properties and torrential rainfall accompanied by anthropogenic factors cause numerous landslides every year. This study will help take proper mitigation and preparedness measures for slope protection in the KRC area and surroundings.

Groundwater monitoring is essential for sustainable groundwater resource management in a country like Bangladesh, where this precious resource is gradually declining due overextraction. Acquiring groundwater level (GWL) over a large area is time-consuming and expensive. This study proposes an alternative approach to groundwater monitoring using freely available daily groundwater storage (GWS) gridded data of the Global Land Data Assimilation System (GLDAS) with other freely available data, including population, rainfall, temperature, irrigation, elevation for modeling GWL data of Bangladesh with a spatial resolution of 0.25o × 0.25o. This was accomplished by employing multiple linear regression (MLR) and artificial neural networks (ANN), using weekly in-situ GWL data at 844 locations distributed over Bangladesh. The results showed the inability of GWS data to estimate the country's groundwater spatial variability and trend. The relative performance of MLR and ANN models revealed a higher capability of ANN in estimating GWL from GWS and other data with an overall correlation coefficient (R) of 0.95 and mean squared error (MSE) of 0.64. The study revealed population and rainfall have the most decisive influence in determining GWL. The model developed using ANN can be used to estimate GWL at locations where observation data are unavailable and thus monitor GWL for sustainable groundwater management.

An alteration of rainfall variability and changes in rainfall driven extremes have been noticed across the globe with rising earth temperature. Such changes will undoubtedly be more devastating for agriculture-based developing countries. Possible changes in rainfall and droughts due to 1.5º and 2ºC temperature rise scenarios have been evaluated in this study for Bangladesh, which is widely referred to globally most climate change susceptible country. Projections of global climate models (GCMs) of the coupled model intercomparison project phase 6 (CMIP6) for two shared socioeconomic pathway (SSP) scenarios, SSP-119 and SSP-126 were used for this purpose. The results showed an increase in annual rainfall over Bangladesh for both scenarios. However, the changes in rainfall variability would cause a drastic change in the drought pattern. Overall, drought frequency may decrease in the drought-prone western region up to -50% and increase in the east up to 50 to 70%, making droughts more homogeneously distributed over the country. However, a higher increase in the east than a decrease in the west for SSP119 indicates a possible shift in the country's drought-prone region. Comparison of drought scenarios for SSP119 and SSP126 revealed a 0.5ºC further rise in temperature might cause an increase in extreme drought frequency by 30% in the central-eastern region. Bangladesh should take effective drought mitigation measures to sustain its agricultural development.

There is a long history of catastrophic earthquakes in and around Bangladesh due to the ongoing collision of the Indian and Eurasian plates. In this study, deterministic seismic hazard analysis (DSHA) is carried out for the south-central coastal region of Bangladesh. As a case study, important locations (i.e., Kumirmara, Nilganj, Dhulasar, Moudubi, and Char Muntaz) are selected to identify the areas that will experience the maximum and minimum seismic hazards if a catastrophic earthquake occurs. The peak ground acceleration (PGA) and spectral acceleration (SA) values at bedrock and ground surface conditions are estimated considering the worst-case scenario by using all possible seismogenic sources, controlling earthquakes, and two sets of ground motion prediction equations (GMPEs). The GMPEs and seismotectonic maps are used to determine the controlling earthquakes and the shortest distances from the sources to study areas. It is predicted that the Chittagong-Tripura folded belt (CTFB) source, which is located at the shortest distance from the selected areas, may produce the maximum magnitude earthquake. As the ground motion intensities depend on the earthquake magnitude and the distance from the sources, the maximum ground motion (PGA and SA) is observed for the CTFB source. The estimated maximum and minimum PGA values are 0.535 g and 0.301 g at the reference bedrock conditions in Char Muntaz and Kumirmara, respectively. It is observed that at all conditions and for all sources, Char Muntaz will experience the greatest ground motion and Kumirmara will experience the least ground motion. The result of this study will help to select the areas for the development of critical infrastructure in the coastal region of Bangladesh.

The study aims to assess the landslide hazard scenario of the Kutupalong Rohingya camp, considered one of the largest humanitarian shelters for conflict-fled people. The camp area lying in a prominent tectonic setting and meteorological environment, is vulnerable to landslide hazards, specifically in the monsoon season. The worst-case scenario of earthquake and rainfall occurrence at the same time or one after another is considered in this study. Landslide favorable parameters (topographic, soil physical property, and contributing factors) are designed in the study to identify the hazard-prone areas through the factor of safety computation. Topographic parameters are prepared by combining field investigation and remote sensing-based information. Soil physical properties are designed in two different models to account for their uncertainties; normal probabilistic distribution and interpolation-based spatial distribution. The contributing factors (earthquake and rainfall) have been assessed using the probabilistic approach. The Peak Ground Acceleration (PGA) exceedance and rainfall intensities of 50, 75, 100, 200, and 475 years return period are applied in the factor of safety calculation. The factor of safety calculation has been run using two different methods; Monte-Carlo simulation using Python scripts and direct estimation method. Different duration (rainfall intensity) scenarios are also modeled to estimate the vulnerable areas in these models. The findings of the study are finally validated against field investigation-based landslide inventory with more than 84% accuracy at a 90% confidence interval.

The ground motion intensity of an earthquake is significantly changed when seismic waves propagate from the bedrock to the near-surface soft geological materials. The ground where the shear wave velocity (Vs) exists greater than 760 m/s is generally considered as bedrock. As a common practice in the last three decades, the surface ground motion of a soil site is estimated by multiplying the bedrock motion with the site coefficient that is empirically determined from the time-averaged shear wave velocity in the top 30 m (Vs30) of the site. The site coefficient is defined as the ratio of the ground motion intensity at the ground surface to that of the bedrock. If the bedrock of a site exists at a depth of greater than 30 m, the site effect from the depth of 30 m to the bedrock is not accounted in the Vs30-based site coefficient. In Dhaka City, the minimum depth of the bedrock is approximately 175 m. Therefore, the use of the Vs30-based site coefficient to estimate the surface ground motion is not appropriate for the soft and deep sedimentary deposits of this city. In this study, site response analysis using the Vs30-based site coefficient, linear, equivalent-linear, and nonlinear approaches has been performed to estimate the surface ground motion at different sites of Dhaka City and to compare the results of different approaches. It is observed that the surface ground motion is decreased with increasing the depth of the bedrock due to low shear strain and viscous damping in the soft sedimentary deposits.

Dengue fever is a tropical viral disease mostly spread by the Aedes aegypti mosquito across the globe. Each year, millions of people have dengue fever, and many die as a result. Since 2002, the severity of dengue in Bangladesh has increased, and in 2019, it reached its worst level ever. This research used satellite imagery to determine the spatial relationship between urban environmental components (UEC) and dengue incidence in Dhaka in 2019. Land surface temperature (LST), urban heat-island (UHI), land-use–land-cover (LULC), population census, and dengue patient data were evaluated. On the other hand, the temporal association between dengue and 2019 UEC data for Dhaka city, such as precipitation, relative humidity, and temperature, were explored. The calculation indicates that the LST in the research region varies between 21.59 and 33.33 degrees Celsius. Multiple UHIs are present within the city, with LST values ranging from 27 to 32 degrees Celsius. In 2019, these UHIs had a higher incidence of dengue. NDVI values between 0.18 and 1 indicate the presence of vegetation and plants, and the NDWI identifies waterbodies with values between 0 and 1. About 2.51%, 2.66%, 12.81%, and 82% of the city is comprised of water, bare ground, vegetation, and settlement, respectively. The kernel density estimate of dengue data reveals that the majority of dengue cases were concentrated in the city’s north edge, south, north-west, and center. The dengue risk map was created by combining all of these spatial outputs (LST, UHI, LULC, population density, and dengue data) and revealed that UHIs of Dhaka are places with high ground temperature and lesser vegetation, waterbodies, and dense urban characteristics, with the highest incidence of dengue. The average yearly temperature in 2019 was 25.26 degrees Celsius. May was the warmest month, with an average monthly temperature of 28.83 degrees Celsius. The monsoon and post-monsoon seasons (middle of March to middle of September) of 2019 sustained higher ambient temperatures (>26 °C), greater relative humidity (>80%), and at least 150 mm of precipitation. The study reveals that dengue transmits faster under climatological circumstances characterized by higher temperatures, relative humidity, and precipitation.

Groundwater is gradually becoming scarce in Bangladesh like many other countries around the globe due to various climatic, hydrological, and socio-economic changes. This study aimed to assess the spatiotemporal changes in groundwater availability and sustainability in Bangladesh. The study employed weekly groundwater table (GWT) data from 844 groundwater observation wells of the Bangladesh Water Development Board (BWDB) from 1995 to 2019. Mann-Kendall (M-K) test at 95% significance level and the Sen's slope estimator were used to assess the spatiotemporal variations in GWT, and the reliability-resiliency-vulnerability (RRV) approach was applied for evaluating sustainability. In addition, the yearly trends in RRV indicators and sustainability were estimated. The results revealed the mean GWT is low in the northwest and central regions. The GWT is declining almost all over the country, particularly in the areas where it is already low by 0.548-1.398 m/year. The groundwater showed remarkably poor sustainability for most of the areas. It also showed a declining trend over a large area in the central north. The analysis of results through the scrutiny of irrigated land and population distribution of the country revealed higher abstraction of groundwater for irrigation and domestic supply are the major cause of declining GWT in the northwest and central regions of the country. The study provided an understanding of the changes in groundwater and its sustainability which can be used as a guide for sustainable management of groundwater and contribute to drawing up future groundwater policies.

This study aims to build on the existing knowledge and improve the overall PSHA results by modifying source, path and site characteristics for Bangladesh. Firstly, six potential seismotectonic zones have been re-defined based on the recent study of Wang et al. (J Geophys Res Solid Earth 119:3576–3822, 2014) and Nath and Thingbaijam (J Seismol 15(2):295–315, 2011), and the updated earthquake catalogue has been declustered using two methods. Important source parameters, such as recurrence b-values and maximum magnitudes, have been determined using the Maximum Likelihood and cumulative moment methods, respectively, and their uncertainties have been addressed using a logic-tree approach. Secondly, based on literature review and studies in neighboring countries, suitable GMPEs have been selected for the seismic zones and the uncertainties have been addressed using a logic tree approach. A significant novelty of the study lies in the consideration of the site effects by integrating Vs30 values throughout the country. The ground motions—PGA and SA (at 0.2, 1.0 and 2.0 s) are computed using GEM’s OpenQuake and presented in form of hazard maps for 2% and 10% probabilities of exceedance in 50 years as well as mean hazard curves and uniform hazard spectra. Disaggregation for capital city Dhaka has also been carried out to show the hazard contributions of magnitude–distance pairs. The spatial distribution of PGA and SA are found remarkably higher than previous findings, likely due to differences in parameters and uncertainties. The results show a marked increase (by almost 20%) in the observed ground motions with respect to those carried out previously by uniformly characterizing the whole country as a firm rock.

Nowadays, earthquake risk-sensitive land use planning has become a popular approach to reduce urban seismic risk. To address this issue, standard penetration test (SPT), downhole seismic (DS) test, and multichannel analysis of surface waves (MASW) investigations were carried out at various locations in Tangail Municipality, Bangladesh. The intention is to characterize the subsurface soil and to find shear wave velocity up to a depth of 30 m (Vs30) for seismic hazard analysis and liquefaction potential index (LPI) calculation. The Vs30 of the study area ranges from 161 to 228 m/s and the LPI varies from 5.08 to 39.9. These results were analyzed and combined to provide valuable information that can be used for the preparation of earthquake risk-sensitive land use map. The combined results revealed that most of the western and northern areas of Tangail Municipality have relatively lower risk compared to the other areas. The findings of this study will help to prepare a risk-sensitive (earthquake focused) land use plan and to aid future urban development in a resilient manner. In addition, the methodology can efficiently combine different hazard data and give a comprehensive view of the total risk scenario at a glance without loss of information.

The present study assessed the vegetation response to climate in the water-stressed northwest Bangladesh (NWB). The quantile regression analysis was employed to evaluate the effect of climate and climatic extremes on vegetation. The nonparametric correlation analysis was used to assess the climatic influence on vegetation for various time lags. Besides, the modified Mann-Kendall (MMK) test was conducted to understand the changes in climate and vegetation to anticipate the climate change impacts on vegetation. Satellite estimation of Normalized Difference Vegetation Index (NDVI) and observed rainfall and temperature data collected from five locations of the study area for the period 1982-2018 was used for this purpose. The results revealed a negative effect of rainfall, a positive impact of maximum temperature on vegetation in monsoon and a positive influence on minimum temperature on vegetation in winter. Quantile regression analysis revealed a significant negative influence of extreme rainfall and a positive impact of maximum temperature on vegetation for the whole NWB. Overall, the study revealed a greater influence of temperature than rainfall on vegetation change in the region. The trend analysis revealed a reduction in rainfall (-2.56 mm/decade) and a rise in temperature (0.176ºC/decade), and thus, an increase in vegetation (0.014 per decade). The results indicate the positive effect of climate change on vegetation, positively impacting the environment and water resources in the study area.

Soil liquefaction resistance evaluation is an important site investigation for seismically active areas. To minimize the loss of life and property, liquefaction hazard analysis is a prerequisite for seismic risk management and development of an area. Liquefaction potential index (LPI) is widely used to determine the severity of liquefaction quantitatively and spatially. LPI is estimated from the factor of safety (FS) of liquefaction that is the ratio of cyclic resistance ratio (CRR) to cyclic stress ratio (CSR) calculated applying simplified procedure. Artificial neural network (ANN) algorithm has been used in the present study to predict CRR directly from the normalized standard penetration test blow count (SPT-N) and near-surface shear wave velocity (Vs) data of Dhaka City. It is observed that ANN model have generated accurate CRR data. Three liquefaction hazard zones are identified in Dhaka City on the basis of the cumulative frequency (CF) distribution of the LPI of each geological unit. The liquefaction hazard maps have been prepared for the city using the liquefaction potential index (LPI) and its cumulative frequency (CF) distribution of each liquefaction hazard zone. The CF distribution of the SPT-N based LPI indicates that 15%, 53%, and 69% of areas, whereas the CF distribution of the Vs based LPI indicates that 11%, 48%, and 62% of areas of Zone 1, 2, and 3, respectively, show surface manifestation of liquefaction for a scenario earthquake of moment magnitude, Mw 7.5 with a peak horizontal ground acceleration (PGA) of 0.15 g.

Drought is an affliction for a region that primarily depends on agriculture as economic activity. Commonly monitoring and characterizing of drought is performed by only analyzing the meteorological aspect, assuming precipitation as the primary source of water. However, in riverine Bangladesh, this can lead to an erroneous conclusion, as there is a multitude of available water sources. Consequently, in this study, vegetation condition (Standard Vegetation Index), soil moisture (Soil Moisture Index), and precipitation (Standard Precipitation Index) are separately investigated from 2003 to 2019, in the Northwestern Teesta floodplain. Subsequently, statistical regression analysis is performed to determine the relationships between different aspects of drought. In addition, information obtained from field visits and expert opinions has also been assimilated. Analysis of vegetation and soil moisture condition presents a progressively improving scenario. However, SPI shows an incessant decline in meteorological drought conditions, especially after 2007. Evidently, regression analysis does not provide any indication of an interrelationship between the studied agricultural and meteorological parameters. Presumably, this absence is instigated because the study area is highly irrigated as the groundwater table is suitably near the surface and the existence of nearby Teesta river allows for the utilization of surface water. Moreover, the cropping pattern is shifting toward crops that require much less water and to places where soil moisture is scarce. Thus, this study addresses the gap in knowledge regarding the nature of agricultural drought and the dynamics of different aspects of drought which will be invaluable for the water management and agricultural policy in the study area as well as other regions with a similar backdrop.

Globally, a number of catastrophic hydrometeorological hazards occurred in 2017 among which the monsoon floods in South Asia was particularly disastrous, killing nearly 1200 people in India, Nepal and Bangladesh. The wetland region (Haor) of northeastern (NE) Bangladesh was severely affected by flash floods early in 2017, affecting nearly 1 million households and damaging US $450 million worth of rice crops. This study investigates how the NE Bangladesh experienced the 2017 flash floods, and to what degree the wetland communities are vulnerable and resilience to flash floods. Focus group discussion, key informant interviews, and household questionnaire surveys (n = 80) were applied in the study area of Sunamganj district. Results from statistical analyses and regression modelling reveal that poor people are particularly vulnerable to floods but they are also more adaptive and thus resilient; middle-income households are vulnerable as they are hesitant to take up any jobs and accept flood relief; and rich households, despite being less adaptive, are able to recover from flood disasters because of wealth. This study reveals that resilience also stems from deep religious faith in the Haor inhabitants that supports communities to move on by accepting that most natural calamities such as flash floods are divine tests. This study also finds that women are particularly vulnerable and less resilient as they are not normally allowed to work outside of their homes and beyond the Haor communities due to cultural and religious reasons.

Time-averaged shear wave velocity of the soil layers to a depth of 30 m (Vs30) is primarily estimated by different geophysical and geotechnical site investigation techniques, such as downhole and crosshole seismics (DS and CS), spectral analysis of surface waves (SASW), multichannel analysis of surface waves (MASW), and the standard penetration test (SPT). Sufficiently dense field measurements of the Vs30 using these techniques are not feasible for VS30 mapping at a regional scale. Therefore, secondary information, such as geological and topographical constrains are used as proxies to predict the Vs30 for mapping purposes. In the present study, a Vs30 map for Sylhet City has been prepared based on the geological and topographical constrains. The map has five Vs30 units having a distinct mean Vs30 value for each unit. This Vs30 map can be used as an effective proxy to estimate site response of the soil layers in Sylhet City.

Dhaka, the capital city of Bangladesh, is one of the seismically vulnerable cities in the world due to its location close to the convergent boundary between the Eurasian and Indian Plates, unplanned urbanization, non-engineered construction practice, high population density, and weak emergency response system. The city is developed on an elevated Pleistocene terrace with surrounding Holocene floodplains. The terrace consists of the Pleistocene clayey soils, and the floodplains are composed of alluvial sandy and clayey soils. The average shear wave velocity of the near-surface soils up to a depth of 30 m (V s 30 ) is required for Dhaka City to estimate the amplification factors of seismic waves for site-specific seismic hazard analysis. Therefore, the V s 30 has been estimated in the city using downhole seismic (DS), multichannel analysis of surface waves (MASW), and small-scale microtremor measurement (SSMM) methods, and empirical correlation between the shear wave velocity (Vs) and standard penetration test blow count (SPT-N). The V s 30 has also been predicted using the relationship between the V s 30 and Holocene soil thickness. The V s 30 results of the DS, MASW, SSMM, and SPT-N vary from 127 to 320 m/s. The V s 30 values that are predicted based on the Holocene soil thickness vary from 145 to 260 m/s. Then, a V s 30 map has been prepared for Dhaka City using the V s 30 values that are predicted from the Holocene soil thickness at a grid of 30 m. The near-surface soils of the city are classified based on the V s 30 as site classes D (stiff soils) and E (soft soils) according to the NEHRP (National Earthquake Hazards Reduction Program, the USA) and as subsoil classes C and D according to the Eurocode 8.

Bangladesh has often been considered as the land of extremes in terms of natural processes. The statement is justified by the presence of world’s largest delta, one of the largest river systems carrying a huge amount of water and sediment discharge as well as prevalence of a number of natural hazards. These characteristics make the region very dynamic and sensitive to changes. Bangladesh is one of the most densely populated countries in the world and human development activities to accommodate the large population have caused major disruptions to the dynamics of the natural system. The study focuses on such a case where anthropogenic activities, such as polderization, dam construction etc. have disrupted the natural land building process and have caused persistent waterlogging in the southwest region of Bangladesh. The rivers in the region are naturally characterized by active deposition of sediment in riverbed causing reduced drainage capacity. Moreover, construction of coastal polders that de-linked the flood plains from the rivers, and diminished upstream flow during the dry season deteriorated the sedimentation problem in the region. The study delineates different hydrological parameters and characteristics of the deposited sediments along with identification of social vulnerabilities. The investigated hydrological and sedimentological characteristics refer to the existing sediment management as well as provide a framework for the future development works in the pre-identified TRM sites. Based on the findings, the suitability of Inclusive and Adaptive Tidal River Management (TRM++) technique was assessed.

In recent years, decision-making and site-planning strategies for earthquake mitigation have shifted away from a crisis management approach, to a greater emphasis on risk reduction. The earthquake hazard of a particular area can be assessed using geophysical and geotechnical site investigations. In the present study, seismic site characterization was carried out to evaluate earthquake risk for the town of Moulvibazar, Bangladesh, by integrating geophysical and geotechnical approaches. The study revealed that the average shear wave velocity to a depth of 30 m (AVS30) varied from 150 to 235 m/s, and US National Earthquake Hazards Reduction Program (NEHRP) soil site classes D and E were predominant, with soil amplification factors (SAF) of 1.3 and 1.45 for site classes D and E, respectively. In addition, peak ground acceleration (PGA) at the ground surface ranged from 0.325 to 0.3625 g, foundation layer depths for the deep foundation varied from 15 to 29 m, and the predominant periods ranged from 0.35 to 0.72 s. These soil parameters can be used to prepare an earthquake risk-sensitive land use plan for future urban development and to design earthquake-resistant structures.

The average shear wave velocity of the near-surface materials down to a depth of 30 m (Vs30) is essential for seismic site characterization to estimate the local amplification factor of the seismic waves during an earthquake. Chittagong City is one of the highest risk cities of Bangladesh for its seismic vulnerability. In the present study, the Vs30 is estimated for Chittagong City using the multichannel analysis of surface waves (MASW), small scale microtremor measurement (SSMM), downhole seismic (DS), and correlation between the shear wave velocity (Vs) and standard penetration test blow count (SPT-N). The Vs30 of the near-surface materials of the city varies from 123 m/s to 420 m/s. A Vs30 map is prepared from the Vs30 of each 30 m grid using the relationship between the Holocene soil thickness and the Vs30. Based on the Vs30, the near-surface materials of Chittagong City are classified as site classes C, D, and E according to the National Earthquake Hazards Reduction Program (NEHRP), USA and as site classes B, C, and D according to the Eurocode 8. The Vs30 map can be used for seismic microzonation, future planning, and development of the city to improve the earthquake resiliency of the city.

Preparation of liquefaction hazard map of prone areas has high importance for decision makers or site planners to reduce loss of lives. In this study, liquefaction hazard map of Dhaka City was prepared using liquefaction potential index (LPI) and cumulative frequency distribution of LPI of surface geological units, which is an excellent approach to evaluate the liquefaction hazard quantitatively and spatially. LPI values were calculated using Simplified Procedure of liquefaction potential assessment for 53 Standard Penetration Test (SPT) profiles conducted in different surface geological units of the city. The LPI values of the city varied from 0 to 19.33 having very low to very high liquefaction hazard. The hazard of each unit was also defined by cumulative frequency at LPI = 5 which may be evaluated as the threshold for observation effects of liquefaction on surface. The geological units of the city were grouped into three liquefaction hazard zones, i.e., Zone 1, Zone 2 and Zone 3 based on cumulative frequency. The hazard map indicates that 8%, 50% and 72% of Zone 1, Zone 2 and Zone 3, respectively, will show surface manifestation of liquefaction for an earthquake scenario having a magnitude of 7.0 (M w ) and a peak ground acceleration of 0.15 g.

A paleo-seismological study was conducted at Jaflong, Sylhet, Bangladesh, which is on the eastern part of the Dauki fault. The geomorphology around Jaflong is divided into the Shillong Plateau, the foothills, the lower terraces, and the alluvial plain from north to south. Because the foothills and lower terraces are considered to be uplifted tectonically, an active fault is inferred to the south of the lower terraces. This fault, which branches from the Dauki fault as a foreland migration, is known as the Jaflong fault in this paper. The trench investigation was conducted at the southern edge of the lower terrace. The angular unconformity accompanied by folding, which is thought to be the top of the growth strata, was identified in the trench. An asymmetric anticline with a steep southern limb and gentle northern limb is inferred from the back-tilted lower terrace and the folding of the gravel layer parallel to the lower terrace surface. The timing of the seismic event which formed the folding and unconformity is dated to between AD 840 and 920. The trench investigation at Gabrakhari, on the western part of the Dauki fault, revealed that the Dauki fault ruptured in AD 1548 (Morino et al., 2011). Because the 1897 great Indian earthquake (M ⩾ 8.0; Yeats et al., 1997) was caused by the rupture of the Dauki fault (Oldham, 1899), it is clear that the Dauki fault has ruptured three times in the past one thousand years. The timing of these seismic events coincides with that of the paleo-liquefactions confirmed on the Shillong Plateau. It is essential for the paleo-seismological study of the Dauki fault to determine the surface ruptures of the 1897 earthquake. The Dauki fault might be divided into four rupture segments, the western, central, eastern, and easternmost segments. The eastern and western segments ruptured in AD 840–920 and in 1548, respectively. The 1897 earthquake might have been caused by the rupture of the central segment.

The Dauki Fault, which is inferred to go through the southern margin of the Shillong Plateau, is an E–W trending reverse one inclined towards the north. The Dauki Fault was believed to be active during the Late Quaternary time by the geomorphic features of the Shillong Plateau, the gravity anomaly data, and uplifted Tertiary and Quaternary deposits on the southern foothills of the Shillong Plateau. However, previous studies did not show any specific evidence that the Dauki Fault is active, since active fault survey such as satellite photo interpretation and trench investigation was not performed hitherto. We carried out CORONA satellite photo interpretation and trench investigation across the Dauki Fault at Gabrakhari Village for the first time. Consequently small fault strands and clear unconformity accompanied with faulting were confirmed in the trench. However, these small fault strands may be secondary ones branched from a main fault which may be concealed under the trench. The time of seismic event, which is inferred from unconformity, is dated back to A.D. 1500–1630. The seismic event during A.D. 1500–1630 may correspond with the 1548 earthquake which is currently a first recorded large earthquake in Bangladesh. Furthermore, sand dikes due to paleo-liquefaction, which reach near the ground surface, were confirmed at the trench. According to radiocarbon age, the sand dikes were formed during the 1897 Ms. 8.0 Great Assam earthquake.

This study aims to prepare a detailed GIS-based geomorphological map accompanied with landfill sites of Dhaka city area which can be used for multipurpose functionality. Attainment of the geomorphological map is based upon interpretation of the oldest available aerial photographs (1:40,000) and contemporary topographic maps (1:8000) which reflect almost pre-urban ground of Dhaka. Randomly distributed 160 boreholes have been used to prepare representative soil profiles (RSP) to identify the near-surface lithology of the geomorphological units. The study reveals that 13 out of 18 low-lying geomorphic units, comprising 65% of the total area demand landfill practices for urban development. Landfill sites have been merged with urban growth on each low-lying geomorphic unit using a spatially enhanced fused image of IRS-1D PAN and ETM+ bands 5, 4 and 3, acquired February 2000 and 2002, respectively. We found that 43% area of the total low-lying geomorphic units experience fill practices so far. The fill sites have been differentiated into four classes based on their relative thickness. Integration of fill classes with geomorphological map shows the urban dynamics of Dhaka city area till 2002. Due to GIS integration, this map can be rapidly updated to demonstrate temporal modifications in urban ground. It can be used effectively in different geomorphological hazard mapping and urban land-use practices.

A GIS based approach is proposed for the integration of three thematic maps viz. geomorphology, drainage density and slope using fuzzy logic for the assessment of ground water resource potential of a soft rock terrain of Midnapur District, West Bengal, India. The geomorphology and drainage density maps of the area are prepared from IRS-1B LISS-II data, and the slope map is obtained from the contours depicted on the topographic map of Survey of India. Each feature of all the thematic maps is assigned with individual fuzzy set values within a range between 0 to 1 according to their relative importance in the prediction of ground water occurrence. The maps are then integrated through fuzzy operation to model the ground water potential zone of the study area. The evolved model while verified with surface geophysical results is found to be in good agreement.

Bangladesh is a disaster prone country. Though cyclone, flood, landslides, river erosion as well as climate induced hazards are the frequent disastrous phenomena in the country, in the last 150 years, the country experienced damages of five earthquakes having magnitude over 7.0 (Richter Scale). There are subduction zones in the east and north of the country while three major active faults have been studied so far having potential to generate 7.0–8.5 magnitude earthquake. Geophysical and paleoseismic investigations also conducted to estimate the slip-rate as well as recurrence period of the historical earthquakes. Considering the potential risks, the Government has taken initiatives through Comprehensive Disaster Management Programme (CDMP) to assess the seismic risk following the deterministic and probabilistic procedures mainly to address the scenario based earthquake risk management in the country. Following the estimated scenarios, spatial emergency risk management plan in the name of contingency plan developed for the main cities, viz., Dhaka. Chittagong and Sylhet as well as other ten major responding agencies. Numbers of simulation exercises were conducted to implement the contingency plan. In order to rightly address the earthquake risk reduction, government has taken number of initiatives onwards 2006 under the umbrella of CDMP. These are development of 62,000 Urban Community Volunteer mainly in the earthquake prone cities, training for masons and bar binders as well as engineers, preparation of risk sensitive landuse planning, building awareness to the public representatives and city dwellers, increasing the research activities in the government agencies and academic institutions as well as gradual procurement of search and rescue equipments. It can be said that a comprehensive approach has been launched for earthquake risk management in Bangladesh, which need to be nourished by all relevant quarters to develop a sustainable urban risk management environment in the country.