Examining the Nature of a Floodplain Using GIS ...

Flooding is one of the rampant and persistent problems in many of the developing countries. Sustainable and innovative actions are needed to address the continuously increasing flood risk in developing countries. The aim of this study was to demonstrate how open-source GIS data source and its functionalities can be used to analyze the nature of a flood plain, particularly in developing countries. The selected case study area is a flood-prone area called Jangwani, found in Dar Es Salaam city in Tanzania. Different GIS open-source data were processed to generate flow direction, flow accumulation, slope, hillshade and contour raster in the floodplain area. Insightful findings were obtained. About 16.4 percent of the surrounding population by area is likely to be affected by the floodplain during the rainy season. The floodplain slopes were found to be flat which impedes the discharge of water to the Indian Ocean. The elevation in the floodplain was found to be lower than in surrounding areas. Thus, the watersheds intersecting Jangwani floodplain which are four times greater than the area of Jangwani floodplain are most likely to discharge in the plain due to the plain’s lower slope. Further, two major transport infrastructures namely the BRT bus terminal and Jangwani bus station, are likely to be inside the floodplain in the occasion of heavy rainfall. This may result in serious transportation hurdles for the populations that surround the floodplain area during the rainy seasons. The results of this analysis can assist in the appraising of effective flood mitigation measures in developing countries where there are limited resources for data acquisition.