Monitoring and Analysis of Hydro-Environmental Condition in the North Western Part of Bangladesh and Development of a Satellite Based Aridity Assessment Algorithm

Abstract

In the present work the functioning of a coupling of multi type data like remote sensing data, geophysical data, climatic data and other ancillary information, has been studied to address the driving forces related with the ego-environment of Barend Tract and adjacent flood alluvial plane land, and to monitor such processes. Time series remote sensing data have been analyzed over a period of about 27 years (I 973 to I 998) to characterize the aridity of Ba rind tract area and flood alluvial plane land, situated in the northwestern part of Bangladesh. Two adjacent but characteristically different land areas, (i) semi-arid Barend Tract and (ii) Ganges alluvial flood plain land has been selected for the present study where different hydro environmental conditions prevail over the year. The study reveals that the radiometric responses of Landsat TM are characteristically different for the two study sites having different environmental conditions. S patio-temporal analysis from Landsat TM derived spectral response curve shows appropriate seasonal trend and an overall trend towards increased vegetation over the Barend tract area that is consistent with field observation over the study interval. Impacts of climatic variables particularly that of rainfall and temperature on the hydro-environment of the area have been studied. Both rainfall and temperature seem to play a dynamic role in fixing up the hydro-environmental setup of the area. Barend Tract area never flooded, here rainfall is the only source of all hydro-logical activities. Coupling of satellite-derived land cover information with land fond and hydro-climatic data reveals that in surface cover dynamics and its seasonal transformation of surface categories over time and space, are a function of land form characteristics and the prevailing hydro-climatic condition of the area. The sensitivity of surface cover change to the rainfall amount is higher in Ba rind tract area in comparison with the flood plain areas. The semi-arid Barend Tract area remains either mostly bare (about 90 percent) or highly vegetated (vegetation cover greater than 75 percent) depending on the season, which is in contrast to the flood plain areas that are found to be moderately vegetated throughout different seasons, though both sites receive an almost similar amount of seasonal and annual natural facilities.