Multi-criteria approach to develop flood susceptibility maps in arid regions of Middle East

Flood susceptibility and risk assessment are very important for suitable urban development. The present study introduces a methodology for identifying flood susceptibility zones using a multi-criteria analysis. The methodology was applied in the Riyadh Province, the central region of Saudi Arabia, validated using historical flood records and re-applied in the Riyadh city to assess the effect of scale on the results. The methodology incorporates 10 susceptibility factors: flow accumulation, annual rainfall, slope, runoff, land use/cover, elevation, geology, soil type, distance from the drainage network, and drainage density. An analytical hierarchy process was employed to derive the weight of each susceptibility factor, and sensitivity analysis was done to test how sensitive are the results to changes in the weights of susceptibility factors, and to evaluate the contribution of different susceptibility factors in developing the flood susceptibility maps. These maps were found to be in good agreement with historical flood events in the Riyadh province and Riyadh city and so they should be useful to assist flood mitigation and for future land use planning in both Riyadh province and Riyadh city. The proposed methodology is useful for general planning and assessment purposes, since it has been shown to be independent of scale, given similar flood susceptibility zones for the Riyadh region were obtained from both large-scale and small-scale models. The highest flood susceptibility areas are found in northern, northeastern, and northwestern parts of the Riyadh Province. Key contributing factors to flood susceptibility are surface runoff, flow accumulation, soil type, elevation, distance to drainage network, drainage density, land use, slope, and geology. Based on results obtained from the sensitivity analysis, it is advisable to consider six or more susceptibility factors in developing flood susceptibility maps, especially factors related to surface runoff and flow accumulation.