Two dimensional flood inundation modelling in urban areas using WMS, HEC-RAS and GIS (Case study in Jeddah city, Saudi Arabia)

This research presents a two-dimensional flood inundation modelling in urbanized areas when some features such as roads, buildings, and fences have great effect on flood propagation. Wadi Qows located in Jeddah City, Saudi Arabia was chosen as case study area because of the flood occurrence of 2009 causing lots of losses either economic or loss of life. The WMS and HEC-RAS program were used for a hydraulic simulation based on channel geometry built by incorporating urban features into DEM using GIS effectively. A resampling method of DEM 90 × 90 m become 10 × 10 m grid cell sizes was conducted to produce a higher resolution DEM suitable for urban flood inundation modelling. The results show that a higher resolution leads to increasing the average flood depth and decreasing the flood extent. Although the change of the grid cell sizes does not affect its elevation values, this approach is helpful to perform flood simulations in urban areas when high resolution DEM availability is limited. In addition, the integration of WMS, HEC-RAS and GIS are powerful tools for flood modelling in rural, mountainous and urban areas.