Social and Economic Vulnerability of Landslide Victims in Chittagong District

Abstract

Recently the frequencies of landslides have increased and a lot of people have been killed in different hill areas in Chittagong district of Bangladesh. To assess the landslide vulnerability in Chittagong, this study has been conducted, both secondary and primary data (qualitative and quantitative) were collected and analyzed. As a result of increasing hill collapse, victims are losing houses, damaged have been done for crops and trees and roads are destroyed. The victims do not have enough safe house to take shelter in the disastrous time. Still, they are living in the hilly areas and are careless about the devastating impact of this natural calamity and continuing in cutting trees and building their houses in an unplanned manner. Hence, a vast amount of social, economic and physical impacts has been found during the research and analysis have shown that people are not properly aware about the impact of the landslide. Basing on primary data, collected through Questionnaire survey, Focus Group Discussion and case study, a modeling of landslide intensity is prepared by applied logistic regression. From the model it has been found that if there are records to increase of rainfall, loss of homestead and hill collapse compare to the previous year, then intensity of landslide also to be increased in that particular area. At the same time, decreasing of tress in the hills and high population density influenced on landslide in the study area. It is observed that vegetation or land cover change is playing an important role to accelerate the landslide in the study area. The analysis of land cover change was done by using Normalized Difference Vegetation Index (NDVI) of vegetation data obtained from satellite image from 2001 to 2019. The area of thick vegetation in Chittagong City Corporation area give a downward trend from 2001 to 2019 which means the number of thick vegetation is lessening significantly with time. The time series analysis of the land cover shows that whenever the percentage of vegetated area decreases, there was a landslide event. Rainfall data collected from TRMM and analyzed; it has been found a relationship between landslide occurrences with the antecedent rainfall. The rainfall threshold for the landslide events is determined in order to find the minimum intensity or duration of rainfall required to trigger a landslide. For this, 5-day antecedent rainfall for each corresponding previous landslide event has been calculated. In case of TRMM, the threshold value for rainfall is 100mm that is if there is more than 100mm rainfall in the study area, then there is a possibility that landslide can occur. Whereas, if the rainfall value exceeds 75mm, then there is a possibility of landslide occurrence, according to the rain gauge station data. Analyzing soil mosture data and the regression method applied, result shows a positive correlation between root zone soil moisture and landslides. On the otherhand, the surface soil moisture shows a negative relation for the possibility of landslide occurrence. Several literature also outlined that landslides are not triggered only due to surface layer saturation; rather, it is the combined effect of surface and sub-surface saturation. However, the root zone soil moisture plays an important role in landslide occurrence than surface zone soil moiture in the study area. Arbitrary cutting the foot of the hill and massive destruction of the hill are responsible for landslides than the heavy rainfall in the canopy structure of the area of Chittagong City Corporation and in Upazilas. Humans are largely responsible for this inescapable change in nature. The trees are cut down by influential people in connection with dishonest official of forest department, the local people are silent in fear. Land grabbers, various influential people or organizations are occupying the hills and making various plans. The important thing is that even if a small hill collapses or someone dies, the victims or local people are reluctant to inform the newspaper or the administration. Because, if it is known, those who live here are also afraid of eviction, so everything is kept secret. To prevent the landslide, based on the analysis the most effective permanent solutions have been found are built retaining wall around the hill and stop digging soil, free the hills, stop living on the hills and plant more trees upon the hills and beneath the hill areas. Almost 99% of the people are interested to move to the new place if the governments wants but currently, they do not have any place to go. Rehabilitating the residents of hill area to plain land through planned way and rehabilitating through way of settlement in accordance with the Social Forestry Rules-2004 is essential. Cutting down hills is a punishable offense. The respective authority must be proactive against cutting down the hill in filing lawsuits and take criminal action against those who are destroying the hills. Precise national hill management act should be executed based on experience of other countries for fair hill management.