Measuring urban expansion pattern using spatial matrices in Khulna City, Bangladesh.

Khulna, the third-largest metropolitan area in Bangladesh, has become a potential site for the polycentric urbanization for multiple mega-projects. Measurement of urban expansion is essential for regulating haphazard growth and achieving effective management. This study aims to quantify and compare the urban expansion pattern of Khulna City Corporation (KCC) and surrounding areas' development hotspots. Landsat remote sensing images of 1990, 2000, 2010 and 2020 were used to perform supervised classification using Geographic Information System (GIS). To quantify urban expansion, we compute Annual Urban Expansion Rate, Urban Expansion Intensity Index, and Urban Expansion Differentiation Index. Although annual urban expansion in the study area was slow during the first two decades, it accelerated to 6.76% during the last decade. 48% of the total built-up areas have grown during 2010-2020 alone. Even though KCC experienced continuous urban growth over a thirty-year period, after 2010, the rate of urban expansion in peripheral areas exceeded that of KCC. Transboundary and intra-regional transportation and economic corridor development, establishment of economically potential zones (EPZ), urban to rural migration, availability of rich agriculture hinterland, low land price and several direct transportation links between the core and periphery are the major influencing factors of peri-urbanization.