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Abstract：
Extreme flood events are disastrous and can cause serious damages to society. Flood frequency obtained based on historical flow records may also be changing under future climate conditions. The associated flood inundation and environmental transport processes will also be affected. In this study, an integrated numerical modeling framework is proposed to investigate the inundation and sedimentation during multiple flood events (2,5,10, 20, 50, 100, 200-year) under future climate change scenarios in a watershed system in northern California, USA. The proposed modeling framework couples physical models of various spatial resolution: kilometers to several hundred kilometers climatic processes, hillslope scale hydrological processes in a watershed, and centimeters to meters scale hydrodynamic and sediment transport processes in a riverine system. The modeling results show that compared to the flows during historical periods, extreme events become more extreme in the 21st century and higher flows tend to be larger and smaller flows tend to be smaller in the system. Flood inundation in the study area, especially during 200-year events, is projected to increase in the future. More sediment will be trapped as the flow increases and the deposition will also increase in the settling basin. Sediment trap efficiency values are within 37.5-65.4% for the historical conditions, within 32.4-68.8% in the first half of the 21st century, and within 34.9-69.3% in the second half of the 21st century. The results highlight the impact of climate change on extreme flood events, the resulting sedimentation, and reflected the importance of incorporating the coupling of physical models into the adaptive watershed and river system management.
摘要：
极端洪水事件是灾难性的，会对社会造成严重破坏。根据历史流量记录获得的洪水频率在未来的气候条件下也可能会发生变化。相关的洪水淹没和环境运输过程也将受到影响。在这项研究中,提出了一个集成的数值建模框架，以研究加利福尼亚北部流域系统中未来气候变化情景下多次洪水事件（2,5,10,20,50,100,200年）期间的淹没和沉积，美国。拟议的建模框架耦合了各种空间分辨率的物理模型：公里到几百公里的气候过程，流域的山坡尺度水文过程，以及河流系统中厘米到米尺度的水动力和泥沙输送过程。建模结果表明，与历史时期的流量相比，极端事件在21世纪变得更加极端，系统中更高的流量往往更大，更小的流量往往更小。研究区域的洪水淹没，尤其是在200年的事件中，预计未来会增加。随着流量的增加，更多的沉积物将被捕获，并且在沉淀池中的沉积也将增加。根据历史条件，泥沙圈闭效率值在37.5-65.4%范围内，在21世纪上半叶的32.4-68.8%内，在21世纪下半叶的34.9-69.3%以内。结果突出了气候变化对极端洪水事件的影响，由此产生的沉降，并反映了将物理模型的耦合纳入自适应流域和河流系统管理的重要性。
