Tracking the changes in the urbanization and vegetation pattern of Dhaka city using Remote Sensing Images

Abstract

There is no doubt that Dhaka city i. growing bUl in which direction and what rale thaI is the main COnCllm.There is also the question how urban growth is influencing the different landuses. Thi. study was initiated to find the answer to these questions. In today. faSI growing pace, the be.t available option to to understand the phenomenon ofuman growlh is the application of Remote Sensing techniques in amulgamation of GIS methods. The study made an attempt 10 understand the relation.hip between the spatial and temporal trends in urbanization and vegetation pattern with tho u.e of Remote Sensing methods. Multidate Landsat images of 1993,1996,199,2003 and L1SS III image of 20117have been used to delineate tho iancover of Dhaka Metropolitan Area into <even c!asses;Water, Builtup area, Baresoil, Grass typo vegetation, Tree type vegetation, Crop type vegetation and Wetlands. In this study only two of the widely used approacl1es i.e. Maximum Likelihood method (a supervised oIassifioation approach) and NOVI (a vegetation index based approach) was explored. Aouracy assessmenlof the oIassified images with thaI of ground !ruth dala showed that tllOqualily of results obtained through maximum likelihood oIassification method were much beller than the NDV! derived outputs. It W,," found through lancovor analysis that over the years, builtup area within !he city boundary has expanded from 23% to 47% from 1993 to 2007. Consequently, other lype of landuses have decreased within a span of 14 years from 1993 02()()7, such as vegetation area (including grass, trees and crops) 58% to 400/0, wetland and waterbodics 14% to 8.7%. TIICdecrease in tree type vegetation is prominent reaching 10% in 2007 from 17% in 1993. The spatial paltern of dmnges in both urbanization and vegetation area is sporadic in lUll"'e. The image analysis shows that the areas with vegetation (gill", tte.s), bare soil, agricnltural land (area with crops), walert>odies and wetlands have been convened into urban areas and lhis trend is still continuing. If such a trend of urbanization at the cost of reduction in velletation, waterbodies continues ignoring any planning consideration of keeping green space, preserving wetlands then Dhaka city's environmenr will becomc unmanagable oau.sing deterioration to the qualily oflife of city dwellers.