Flash Flood Assessment for Wadi Mousa City-Jordan

This paper aims to assess risks due to potential Flash Floods hazards in Wadi Mousa and to determine the magnitude of flows for flash flood hazards and construct Floodplain Zone maps for the selected flood return periods of 25, 50, 75 and 100 years. Wadi Mousa is considered an ephemeral wadi with intermittent flash flood of flows that can exceed the 298 m3/s threshold. Its floods, however, do not flow every year. Nevertheless, at certain years the extent of flood can be huge. The surface drainage may be broadly divided into sub-catchments according to drainage namely; Wadi Als-Sader, Wadi Jelwakh with Wadi Khaleel, Wadi Al-Maghir. Wadi Zarraba is the confluence of the three sub- catchments. The study covers an area of 53.3 km2 and comprises a high semi -arid infrequent flash floods generated by heavy rainstorm over the catchment and flows to Wadi Araba. Average annual rainfall of Wadi Mousa was calculated of 178 mm, and average annual evapotranspiration is 1300 mm per year. The runoff analysis indicates that only rainfall events exceeding 22 mm within the 24 hour period would generate runoff.