Karachi: An Expanding City with Rising Disasters

Karachi, the biggest city of Pakistan, has undergone rapid urbanization since the creation of Pakistan in 1947. The city is expanding with an alarming rate placing pressure on the available natural resources and services with rising number of natural hazards. Urbanization brings not only multiple environmental challenges but also causes socioeconomic issues. One of the current environmental problems due to urbanization of Karachi is blockages in its natural drainage system causing localized floods after heavy rainfalls. In this paper, landuse/cover (LULC) changes of the Karachi city and their impacts on natural drains of one of its three major watersheds, Malir River Basin, over the last 23 years (1993–2015) have been studied. Historical satellite data and remote sensing tools were utilized to examine LULC changes of the Malir River Basin. The U.S.-based first earth observing satellite series of Landsat were selected for this purpose. Shuttle Radar Topographic Mission’s Digital Elevation Model (DEM) along with the topographic sheets of 1975 was utilized to delineate the streams of the Malir Basin using geographical information system (GIS) tools. GIS overlay analyses were done to identify the blockages in the riverbed and flood damages. For flood simulation, historical (1985 to 2014) rainfall gauge observations of Pakistan Meteorological Department (PMD) were acquired. The results of the study showed that a significant portion of the riverbed, delineated from 1975 topographical sheets, has currently been occupied by urban and agricultural lands which have severely affected the natural drainage of stormwater causing localized floods in the basin.