Geospatial assessment of effect of urbanization on natural drainage in a medium-sized town of Akure, Nigeria

Abstract

AbstractThis study examined the state of some urban streams in a tropical environment of Nigeria. It analysed satellite images which include Landsat 5 TM (1986), Landsat 7 ETM (2002), Landsat 8 (2018) imageries with 30 m resolution using ENVI 5.3. The images were classified using a supervised classification algorithm to obtain land use/land cover themes for spatial analysis in the ArcMap 10.3 environment while drainage systems were extracted from the topographical map of 1966 of the study area. Result showed a total drainage network of about 90, covering a total distance of 307 km in 1986, which decreased to 226.87 km in 2018. Within the study period (32 years), more streams experienced decrease in lengths (231.44 km) than those whose lengths increased (129.85 km). While 136.92 km stream lengths were lost within the study period, about 25.45 km stream length were rejuvenated. Urban landuse correspondingly increased from 18.8% in 1986 to 52.2% in 2018, suggesting that a converse relationship between increase in urban land cover and dearth of streams in the area. The study provides information regarding the current status of the drainage system for effective planning and management of flood hazards in the study area. It also canvasses for adequate provision and maintenance of setbacks to streams and rivers under the supervision of the Development Control Department (DCD) of the Ondo State Ministry of Urban Development and Regional Planning (OSMUD&RP).