Historical flood imprints reveal factors causing catastrophic impacts on modern Jeddah, Saudi Arabia: a case of flash floods versus rapid urbanization

Abstract

In the Jeddah region of Saudi Arabia, disastrous flash floods frequently occurred during the last few decades. Short-spelled torrential heavy-rains were considered the main reason for flash floods, which led to high water levels in “urban centers” situated along coastal plains of the Red Sea as well as high-gradient terrains of large braided wadi networks. These flash floods caused enormous fatalities related to lives, properties, and city utilities. It looks impossible to avoid flash flood risks and/or prevent their occurrences under prevailing climatic conditions, but it is possible to mitigate their adverse impacts on city life and property provided interactive relationship between flash flood attitudes and urban development planning are known clearly. This research study was conducted based on extracted wadi courses using SRTM-DEM data and archive geological published maps, modern Jeddah city-map, high-resolution mosaics depicting Jeddah geomorphology, and GIS-linked thematic layers/models. In the integrated research approach, it was evaluated the results from natural and cultural phenomena. Eastern parts of the catchment and terrain of wadis found plutonic igneous rock that resists water percolation and allows runoff from upstream to downstream, resulting in severe flooded conditions. These models revealed extents of extracted historical-imprints of wadi’s flooded courses on the modern city expansion in the Jeddah basin. Comparison indicated that most of the natural drainages and landscape features were bulldozed during Jeddah’s modernization activities. It was also deduced that unanticipated huge construction was another factor aggravating devastation by flash floods in the Jeddah basin. These findings seem to be imperative to reconsider for the formulation of intelligent mitigation plans and redesigning/modifications of new urban settlements.