基于泥沙-径流的山洪灾害动态风险评估与预警

Dynamic flash flood risk assessment and early warning based on sediment-and runoff

我国山洪灾害防治区域面积占陆地面积的40%,山洪灾害防治是山区防灾减灾和经济社会发展的迫切需求,是防止因灾返贫、巩固中国全面脱贫成果的重要保障。山洪灾害风险的准确评估和及时预警是减少人员伤亡的有效手段。现有山洪灾害风险评估和预警体系主要考虑流域产流,基于降雨-流量-水位关系评估山洪风险、预警山洪灾害。然而,山洪往往伴随着大量产沙,洪水和泥沙共同决定着暴雨山洪的受灾程度、受灾范围、预警指标和预警时机。忽略泥沙影响,会导致对山洪水沙灾害风险的严重低估,造成灾害预警的漏报、错报,降低山洪灾害防治的有效性与可靠性。针对泥沙含量、产沙方式等关键要素,分析了泥沙对水沙灾害风险的影响规律,结合现有流域产沙模型与监测技术,提出在径流风险的基础上,引入泥沙风险,针对径流、泥沙风险选用不同预警指标和阈值,实现快速、准确、综合评价和预警泥沙影响下的山洪水沙风险,为我国山洪灾害防治提供理论和技术支撑。

Mountainous flash flood disaster prevention and control area in China accounts for 40% of the whole land area.Flash flood prevention is an urgent need for disaster prevention and reduction in mountainous areas and economic and social development, and it is an important guarantee for preventing people from returning to poverty due to disasters and consolidating China’s achievements in overall poverty alleviation. Risk assessment and early warning is an efficient tool to prevent life and economic loss by flash flood disaster. Current framework of flash flood risk assessment and early warning system mainly adopts runoff production estimation based on hydrological methods of the relationship between rainfall, discharge and water level. However, it should be noticed that flash flood produces not only runoff but also huge sediment, which together determine the inundated area, scope, early warning indicators and warning time. It may highly underestimate the flash flood risk if not considering sediment influence, resulting in missing and misreporting of disaster warning and reducing the effectiveness and reliability of flash flood disaster prevention. Focusing on sediment influence on flash flood risk, key factors such as sediment concentration and sediment yield way is identified, and the influence law of sediment on flood and sediment disaster risk was analyzed. Combined with the existing watershed sediment yield model and monitoring technology, sediment risk was introduced into runoff risk. Different early warning indexes and thresholds for runoff and sediment risk are selected to achieve rapid, accurate and comprehensive assessment and early warning of flash flood with the influence of sediment impacts which can provide theoretical and technical support for flash flood disaster prevention in China.