Highways in arid regions are highly exposed to damage by floods. This requires intensive analysis of flood quantity, time and direction that can be used to design the suitable protection measures. Flood hazard mitigation can be achieved through calculating quantities and distribution by deriving a rainfall–run-off relationship which plays an important role in watershed managements and protection. This study aims to determine the overflow stream ways crosswise over roads and their stream sizes under various precipitation events of 10, 25, 50 and 100 return periods. This can be used in the planning of the flood alleviation measures to protect the roads from flood hazards. This methodology is applied to a real area, Tama road as a part of King Abdul-Aziz Highway, Kingdom of Saudi Arabia. Recorded data were gathered for the study area, and hydrological models were used for delineation of the study area. The results indicated that the proposed site of the new road is extremely exposed to flash flood hazard and protection measures are essential to protect the road. A system of protection is proposed and designed including 7 channels and 2 culverts to mitigate the flood hazard in the area of study. The proposed mitigation system is fit for protecting this area from flood hazards. Protection of such roads helps to save lives of people and reduce the cost of maintenance and rehabilitation due to damages caused by flood.

干旱地区的公路极易遭受洪水破坏。这就需要对洪水的数量，时间和方向进行深入分析，以便设计合适的保护措施。可以通过计算降雨与径流的关系来计算洪水的数量和分布，从而减轻水灾的危害，这在流域的管理和保护中起着重要的作用。这项研究的目的是确定在10、25、50和100个回返期的各种降水事件下，横穿道路的溢流路径及其流量大小。这可用于防洪措施的规划中，以保护道路免受洪水危害。此方法应用于沙特阿拉伯王国阿卜杜勒·阿齐兹国王公路的一部分，在真实地区塔玛路。收集了研究区域的记录数据，和水文模型被用来划定研究区域。结果表明，拟建的新路段极易遭受山洪灾害，因此保护措施对于保护这条路至关重要。提出并设计了一个保护系统，包括7个通道和2个涵洞，以减轻研究区域的洪水灾害。拟议的缓解系统适合于保护该地区免受洪水危害。保护此类道路有助于挽救人们的生命，并减少因洪水造成的破坏而导致的维护和修复成本。提出并设计了一个保护系统，包括7个通道和2个涵洞，以减轻研究区域的洪水灾害。拟议的缓解系统适合于保护该地区免受洪水危害。保护此类道路有助于挽救人们的生命，并减少因洪水造成的破坏而导致的维护和修复成本。提出并设计了一个保护系统，该系统包括7个通道和2个涵洞，以减轻研究区域的洪灾危害。拟议的缓解系统适合于保护该地区免受洪水危害。保护此类道路有助于挽救人们的生命，并减少因洪水造成的破坏而导致的维护和修复成本。