REMOTE SENSING AND GIS-BASED ANALYSIS OF URBAN EXPANSION AND ENCROACHMENT ON FLOODPLAIN IN KADUNA METROPOLIS, NIGERIA.

B. Akpu

The inadequate planning and control of the spatial growth of Kaduna metropolis has resulted in the encroachment of physical development on floodplain in the area with adverse consequences. The aim of this paper is to analyze the encroachment of urban expansion on floodplain in Kaduna metropolis. Landsat MSS imagery of 1973; Landsat TM captured in 1990; Landsat ETM+ of 2001 and Nigeriasat-1 image of 2009 were used to generate the built-up layer for the four epoch time series. Visual or manual image interpretation technique was used to extract the built-up landuse which was digitized to create segment maps. The segment maps were polygonized and rasterized. Using the Digital Elevation Model (DEM) constructed from the topographical map of the area, the floodplain was determined and digitized. The built-up area of the various periods was overlain on the floodplain and the extent and rate of built-up encroachment on the floodplain were determined. An interview was also conducted with the management of Kaduna State Urban Planning and Development Authority (KASUPDA) and Lands and Surveys in order to elicit information on the planning and management of urban expansion in the area. Coding and description were used to analyze the data from the interview. The findings reveal that 22.15% of the floodplain has been taken up by physical development as at 2009. The built-up land in the floodplain was increasing at the rate of 9.61% per annum. This paper recommends that: i) KASUPDA should engage adequate and well trained personnel in order to improve efficiency in the control of growth; ii) Remote Sensing and Geographic Information System (GIS) techniques should be adopted for proper monitoring of the rapid urban expansion.

Key words: Built-up; Encroachment; Floodplain; Geographic Information System; Remote Sensing; Urban Expansion.