Laboratory measurements of the erodibility of gravelly soils

The critical shear stress and erodibility of soil are fundamental parameters for modeling embankment breaching. Unfortunately, very few studies have examined the erosion characteristics of soils consisting predominantly of particles larger than sand. This report presents results of an experimental study in which the erosion characteristics of gravelly soils were measured. A flume apparatus was developed in which 0.45-m-square samples were extruded into confined flow. A mechanical laser system allowed the measurement of scour in real time, resulting in a continuous and automated erosion test. The critical shear stress of a uniform gravel was found to match the expected values based on the Shields diagram, while tests that were composed largely of gravel but contained other soils, such as sand, silt, and clay, varied significantly with the critical shear stress and erodibility, depending highly on the characteristics of the finer soils.

A hydrodynamic model of an embankment breaching due to overtopping flow using FLOW-3D

Embankment dam failures are concerning to many people in the society today, including dam engineers, federal, state, and local officials. The effects of dam failure may cause more harm than good; leading to the losses of lives, properties being damage, economic and environmental downfall. Embankment dam breaching is a complex process between hydraulics and soil erosion processes; until today it still requires more researches to be done. Many factors involved in embankment breaching such as cohesiveness of embankment material, compactness of the embankment soil material, height of the dam and slope of the dam. Through the help of simulation techniques such as computational fluid dynamics, it is possible to understand the behaviour of embankment breaching processes. In this research, modelling of embankment breaching with the aid of FLOW-3D allow us to open doors to plenty of experiments to breaching in the near future. This research focuses in analysing and comparing hydrodynamic parameters; breach outflow hydrograph, peak outflow rate Qp and failure time iy, and geometric parameters; breach depth Hb , and top breach width Bt , of the modelling breached embankment for different sediment diameter and inflow rates. Moreover, the research also investigates the velocity magnitude and breach width during the embankment breaching process.

Comparative Assessment of Livelihood Vulnerability of Climate Induced Migrants: A Micro Level Study on Sagar Island, India

The effects of climate change are causing large scale human displacements over the past few decades. Climate refugees are putting the biggest challenges to the geophysical biological and social system all over the world. This paper attempts to assess and compare the vulnerability of the climate-induced migrants and regular settlers of selected mouzas of Sagar Island, south 24parganas, India. People are witnessing their lands vanishing under their feet in these constantly sinking and shrinking deltaic estuaries of Sundarban. Findings of LVI and LVI-IPCC analysis indicate that the climate-induced migrant communities are more exposed to climatic variability due to the poor adaptive capacity. Moreover, poor access to food, water, health facilities is making them extremely vulnerable with lower resilience as these mouzas are facing frequent flooding, severe coastal erosion, embankment breaching and higher storm surge on annual basis. The outcomes of this study could be beneficial ineffective on-site risk management and planning propositions.

Comparative Assessment of Livelihood Vulnerability of Climate Induced Migrants: A Micro Level Study on Sagar Island, India

The effects of climate change are causing large scale human displacements over the past few decades. Climate refugees are putting the biggest challenges to the geophysical biological and social system all over the world. This paper attempts to assess and compare the vulnerability of the climate-induced migrants and regular settlers of selected mouzas of Sagar Island, south 24parganas, India. People are witnessing their lands vanishing under their feet in these constantly sinking and shrinking deltaic estuaries of Sundarban. Findings of LVI and LVI-IPCC analysis indicate that the climate-induced migrant communities are more exposed to climatic variability due to the poor adaptive capacity. Moreover, poor access to food, water, health facilities is making them extremely vulnerable with lower resilience as these mouzas are facing frequent flooding, severe coastal erosion, embankment breaching and higher storm surge on annual basis. The outcomes of this study could be beneficial ineffective on-site risk management and planning propositions.

An assessment of the livelihood vulnerability of climate induced migrants: A case study on Sagar Island, India

The effects of climate change are causing large scale human displacements all over the World over past few decades and climate refugees are putting biggest challenges to the geophysical biological and social system. This paper attempts to assess the vulnerability of both the refugee and regular settlers of selected mouzas of Sagar Island, south 24parganas, India where people are witnessing their lands vanishing under their feet in these constantly sinking and shrinking deltaic estuaries. Findings of LVI and LVI-IPCC analysis indicate that the climate induced migrant communities are more exposed to climatic variability due to poor adaptive capacity. Poor access to food, water, health facilities are making them extremely vulnerable with lower resilience as these mouzas are facing frequent flooding, severe coastal erosion, embankment breaching and higher storm surges on an annual basis. The outcomes of this study could be beneficial for effective on site risk management, adaptation strategies and further planning propositions.

Geo-historical Appraisal of Embankment Breaching and Its Management on Active Tidal Land of Sundarban: A Case Study in Gosaba Island, South 24 Parganas, West Bengal

The embankments act as a life line for deltaic people of the Sundarbans. The reclamation of immature land through the construction of embankment without proper planning has been increasing the vulnerability of embankment breaching due to various natural and anthropogenic causes. The construction and maintenance of embankments are difficult tasks without prior knowledge about the mode of vulnerability and ground situations of the sites. To understand the scenario of embankment breaching and its recent management strategy, an intensive field survey was conducted to comprehend the underlying reasons for embankment breaching and its management techniques at the ground level. The modern techniques were also incorporated to identify the vulnerable sites of river bank erosion. The study reveals that the southern part of the delta is more vulnerable due to intensive river bank erosion. To understand potential capabilities of these embankments to combat against fluvio-hydrological challenges, a sequential change of embankment construction from historical past to present and recent scientific engineering model of Aila Dam has been chalked out in this study. The present study is an attempt to understand the geo-historical perspectives of embankment construction and to identify the vulnerable coastal zone of Gosaba Island of Sundarban. The study also aims to illustrate the modern techniques of embankment management for its longevity in such a dynamic land.

Public perceptions for managing coastal hazards-study on Indian sundarbans

Community perception becomes a central issue for hazard mitigation of an area. Present study made an attempt to assess public opinion regarding various problems associated with life and livelihood of Sundarbans. A survey was conducted over 254 households located along 22 mangrove fringe villages of Kultali, Gosaba and Hingalganj. Waterlogging, erosion, salinity, storm surges and embankment breaching are the major challenges identified during the survey. Details account of causes, consequences and their spatial extension have been presented and future coping strategies are also recommended. Elevating houses (92%), green buffering (80%) and construction of pucca house (9.8%) are the desired coping strategies for different hazards. Regarding future strategies, 48% like to stay if Govt. initiated for hazard mitigation and 37% like to live with the disaster.