Department of Environmental Science, Policy, & Management, University of California, Berkeley, CA, 94720, United States of America.
J. Amorocho Hydraulics Laboratory, Department of Civil and Environmental Engineering, University of California, Davis, CA 95616, United States of America.
Sci Total Environ. 2020 Oct 20;740:140117. doi: 10.1016/j.scitotenv.2020.140117. Epub 2020 Jun 10.
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.
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也可能在未来气候条件下发生变化。相关的洪水泛滥和环境输运过程也将受到影响。本研究提出了一个综合数值建模框架，用于研究美国加利福尼亚州北部流域系统在未来气候变化情景下多次洪水事件（2 年、5 年、10 年、20 年、50 年、100 年、200 年）期间的淹没和沉积过程。所提出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厘米到米尺度的河流水动力和输沙过程。建模结果表明，与历史时期的流量相比，21 世纪极端事件变得更加极端，系统中的大流量趋于更大，小流量趋于更小。未来，研究区域的洪水淹没范围，尤其是在 200 年一遇的洪水事件中，预计将会增加。随着流量的增加，更多的泥沙将被捕获，沉积区的沉积量也将增加。泥沙捕获效率值在历史条件下为 37.5-65.4%，在 21 世纪上半叶为 32.4-68.8%，在 21 世纪下半叶为 34.9-69.3%。研究结果强调了气候变化对极端洪水事件、由此产生的泥沙沉积的影响，并反映了将物理模型耦合纳入适应性流域和河流水系管理的重要性。
