Application of GIS in developing flood rescue routes a case study of Nyando District

Abstract

The devastation and damages caused by floods in terms of loss of property, livestock, infrastructure and human life in Nyando District is now a known repeated sequence in the basic information of Kenyans and the whole world. Various flood mitigation and management studies have been undertaken in the whole of Nyando Basin with wide range of objectives to control the perennial floods in this District. Ministry of Water Resources and Development, MoWRD (2004) assessed the general damages from floods in Nyando at Kshs.85.65 million.

Another assessment by Ministry of Water and Irrigation, MW&I (2009) projected the same at Kshs.160 million. In this research project, the main intention is to demonstrate the use of Geographical information system (GIS) to select most suitable flood rescue between flood prone areas and safe rescue centers. Various datasets are identified , collected and then used to develop a (GIS) database for the study area, followed by a number of analyses carried out on it to eventually yield the most suitable rescue routes between flooded areas and flood rescue centers within the study area.

The data required for this research included spatial data of Digital Elevation model (DEM), shapefiles for rivers, lakes and roads. These were used together with non spatial data of rainfall, river flow and population census in data preparation, leading to creation of the geodatabase. Network analysis was then undertaken using ArcGIS 10 (Network Extension). The sub locations prone to flooding were chosen as incidents in the network analysis and health centers in the higher ground taken as facilities (rescue centre).

Analysis of network analyst gives the strong opinion that creating a route can mean finding the most scenic route, depending on the impedance chosen. If the impedance chosen is the closest facility (Rescue Centers) from several incidents (Flooded Locations in Nyando), then the best route is the quickest/shortest route to rescue centre. Hence, the best route can be defined as the route that has the lowest impedance, or least cost. Other attributes played no roles in computing the solution, implying that if a time cost and attribute was chosen as impedance, then only the time cost attribute was used to optimize the desired evacuation routes.