Effects of land use change on the planform of the Kafubu river channel in Ndola urban, Zambia (1993-2015).
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This study sought to investigate the extent to which land use changes in Ndola Urban during the 22 years (1993-2015) have affected the planform of the Kafubu River using GIS and remote sensing techniques. The major objective was to assess the extent to which land use changes in Ndola urban have affected the size of the Kafubu River in the study period. For primary data, field observations on river channel were made and five local council planners as well as 13 respondents who had lived in Ndola for more than 20 years were interviewed for information on factors that may have caused land use and river planform changes. For secondary data aerial photographs taken in 1993 and 2015 and a 2009 IKONOS satellite image were used in assessing changes in land use and on the river morphology. The semi structured interviews were analysed using inductive thematic analysis. For analysis, aerial photographs covering the study area taken in 1993 and 2015 and a 2009 satellite image were georeferenced using 11ground control points. ArcGIS 10.5 software was used to generate object based classification land use maps which were later used to compare land use changes and river planform changes. A total of 10 evenly spaced transects were marked and made onto river polygons for each year to aid comparison of channel width with time using AutoCAD 2018. Findings of the study were that, most of the river buffer zone 50m on either side of the river had changed from crop land use to residential areas. The built up area had increased from 41.54ha in 1993 to 198.46ha (377.76%) in 2015 over the whole study period. Between the years 1993 and 2009 there was an increase in channel width at transects 6,7,8,9 and 10 while the other transects showed a width reduction. Similarly, between 2009 and 2015 there was an increase in channel width at transects 1, 2, 3 and 4 while reduction was observed at the other transects. For the entire study period the river width had reduced at all transects except at transects 2 and 10, in terms of channel growth or accretion and reduction due to erosion. The maximum annual rate of accretion was found to be 1.27m/year higher than that of erosion (maximum 0.2m/year) indicating an overall reduction in channel width. In terms of land coverage in the 22-year period, the surface area of Kafubu River reduced from 17.14ha in 1993 to 8.02ha (53.21%) by 2015. Factors attributed to causing land use changes were shortage of state land, corruption in allocation of land, proximity to central business district, population increase, ignorance of environmental issues, and poor planning by the Municipal Council. Similarly, channel planform changes were influenced by building houses in the buffer zone and by the expansion of the river Hyacinth weed. It is concluded that Kafubu River in the 22 years period has been affected by land use change in the river buffer zone from crop land to residential area which led to narrowing of channel width because of deposition of sediment into the river and consequently the reduction of the surface area of the river by 53.21 percent. It is recommended that the local government should implement strict land allocation policies, put more effort in water Hyacinth removal and protect the river buffer zone. Because of the inevitability of urbanisation, Kafubu River channel banks should be made permanent by construction of concrete banks in the town reach which will also protect residents from effects of flooding during wet years. Keywords: Remote Sensing, Accretion, Erosion, Kafubu River
The University of Zambia
- Natural Sciences