تقييم مخاطر السيول وتخفيف حدتها لواديي الصعيد والمحبس، بمدينة العمار، منطقة القصيم، المملکة العربية السعودية

Drainage basins in arid and semi-arid environments in many Saudi cities are exposed to flood rains that are irregular in occurring and pose a threat to areas of human settlement. The situation becomes more dangerous if parts of the drainage basin change from natural cover to urban cover, and the city of Al-Amar under study expanded at the expense of Wadi El saaid and Mahbas, which posed a clear threat to the lives, property and infrastructure of the city.

 This study aims to assess the flood risk and reduce their severity to Wadi El saaid and Mahbas, in the city of Al-Ammar, Al-Qassim Region, Saudi Arabia, using hydrological modeling (WMS) to estimate the calculation of the amounts of flood water and flow rates based on the method (SCS Unit Hydrograph), as was used Geographical Information systems (GIS) for the production and monitoring of soil maps, geology, hydrological group and urban areas to show the impact of risks on the city of Amar, as well as the analysis and estimation of the rain depth of the meteorological station – Faidh Elser(D118) for different return periods (2, 3, 5, 10, 20, 25, 50 and 100 years), using Hyfran statistical analysis program, and (Hydraulic Toolbox) was used when proposing protection mechanism and flood risk mitigation.

The results of the study revealed the penetration of the Wadi El saaid and Mahbas into the urban mass of the city of Al-Amar from west to east and northeast, as the city expanded in age and encroached on most of the waterways of these valleys and it became clear from the results of the study that the flood volumes of Wadi El saaid and Mahbas ranges from 336655.8 m 3 to 582394.5 m 3, and flow values ​​range For them from 14.09 m 3 / s to 20.72 m 3 / s, and these valleys in their current state pose a direct threat to life and property, which requires the development of measures to reduce the flood risk.