Application of remote sensing and geographic information systems to assess crop food security vulnerability due to dam induced flood: The case of ward 24, Chivi district, Zimbabwe
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The nexus between floods and food security related to crop production is undoubtedly relevant yet rarely studied. This applies specifically to drought prone areas in developing countries such as Zimbabwe’s Masvingo Province where Tokwe-Mukosi Dam was built as a multipurpose water project. Therefore, it was important to model crop agriculture before, during and after flooding since 2014. The study calculated a robust modified normalised difference water index (MNDWI) to detect water surface areas so as to determine the flood spatial extent. In addition, the study used on-screen digitized cultivated and non-cultivated areas in high spatial resolution Google Earth images. Thereafter, the digitized cultivated areas were overlaid with flood spatial extent Landsat 8 OLI maps in ArcGIS 10.4. The study demonstrated that, although dam construction is earmarked for food security, specifically, through irrigation among other activities, Tokwe Mukosi Dam has resulted in negatively affecting food production. The study illustrated that in Ward 24, total arable land declined from 7 849ha before flooding to 1 796.46ha after flooding, clearly showing an immense reduction (77%) in food production aspect of the food security pillar. Moreover, the crop production was therefore reduced approximately from 7 456.55 to a mere 1 706.64 (23%) metric tonnes of maize following the 2014 flood disaster and evacuation exercise. The study applied geographic technologies to assess the effects of flood events on food security from the area. Nonetheless, there is still need for further research to assess the food security conditions of the people that were evacuated or resettled to new place due to dam construction especially after irrigation is installed to understand food production.