GIS based mapping and environmental impact of Wetlands changes in a Riverine district of Bangladesh

This research is concerned with the GIS based mapping and change of areal extent of wetlands within two different periods and to identify the causes of change and impact assessment of wetland change in the study area. This research was conducted at a micro scale level at Daulatpur upazila in Manikganj district. It can be seen that development activities as well as increasing population have made a huge difference in wetlands change which are drying up rapidly at present time in the study area compared with the past twenty years or more. Satellite images of two different periods were analyzed using related software. A questionnaire was conducted to investigate the attitude of the cross-section of people in five unions of the study area. GPS survey and visual observation was also made to verify satellite image information. All collected and gathered primary and secondary data have been processed manually and by using GIS Software (ERDAS Imagine, ArcGIS 9.2, Arc View 3.3, and Image Analysis 1.0). It is found that in 1990, total area of wetland was about 21.76% of the study area has gradually decreased and reached its lowest point was about 20.53% in 2004. From 1990 to 2004, the total area of wetlands decreased to near about 1 sq. mile. The factors responsible for wetlands changes are riverbank erosion, flood and sedimentation, expansion of human settlement, industrialization, unplanned development activities, overexploitation, agriculture and climate change. Degradation of wetlands has created several impacts on drainage system, loss of natural water reservoirs, loss of aquatic animals and fishes, increase in the occurrence of flooding, loss of natural soil nutrients, cropping patterns and amount of production, occupations and transportation facilities. Based on these findings, a number of recommendations have been put forward for conservation, preservation, and management of wetlands to the concern authorities.