COLLABORATIVE RESEARCH: Comparison of Regional Flood Frequency Responses to Climatic Variability in the Western United States

9725336伊利 洪水与过去十年至百年尺度气候变化之间的联系对未来洪水规模和频率的概率评估有着巨大的影响，特别是在未来区域或全球气候变化情景方面。 本研究将使用古森林数据比较十年到千年尺度的气候变化对美国西部三个水文气候区（西南，西北和西部大盆地）河流大洪水的幅度和频率的影响。 古洪水研究将提供过去个别洪水事件的物理证据，通过洪水沉积物的地层分析，将每条河流上严重洪水的记录延长100到1000年。 以前的研究在西南部和初步的实地工作期间进行的夏季在俄勒冈州的约翰戴河和特拉基河在内华达州证实，在所有三个地区的河流优秀的古森林记录的可用性。 美国西南部河流的古洪水年表表明，在过去5000年中，区域气候条件和百年尺度的大洪水频率变化之间存在联系。 该项目的主要目的是确定在现代记录的短时间尺度上洪水发生的时间和控制方面所表现出的区域差异是否适用于洪水对长期气候变化的区域反应。 即使放射性碳测年方法的分辨率相对较低，这种关于洪水水文气候学的广泛的新视角也是可以实现的。 与凯利雷德蒙，副主任和区域气候学家的西部区域气候中心，现代流量，气象和大气压力数据将进行分析，作为在每个地区的古洪水的模拟，从而帮助了解在每个区域洪水系列中观察到的模式的基本物理基础。 这项研究还将利用最近改进的统计计算机程序，将古森林信息纳入单站点洪水频率分析（由填海局开发），以及量化和减少古森林排放模型不确定性的方法（House，1996）。根据关于罕见的大洪水的规模和频率的真实的信息了解气候与洪水之间的联系，将提高供水管理人员预见全球和区域范围气候现象的区域后果的能力，这是面对不确定的未来气候条件的长期规划的一个日益重要的组成部分。

9725336 Ely The connection between floods and decadal-to centennial-scale climatic variations in the past has tremendous implications for probability assessments of the magnitude and frequency of future floods, especially in relation to scenarios of future regional or global climate change. This study will use paleoflood data to compare the influence of decadal-to millennial-scale climatic variability on the magnitude and frequency of large floods on rivers in three district hydroclimatic regions of the western U.S: the Southwest, Northwest, and western Great Basin. The paleoflood studies will provide physical evidence of individual flood events in the past, extending the record of severe floods on each river by 100s to 1000s of years through stratigraphic analysis of flood deposits. Previous studies in the Southwest and preliminary field work conducted during the summer of 1997 on the John Day River in Oregon and the Truckee River in Nevada confirm the availability of excellent paleoflood records from rivers in all three regions. Paleoflood chronologies on rivers in the southwestern U.S. indicate a connection between regional climatic conditions and centennial-scale variations in the frequency of large floods over the last 5000 years. A principal aim of this project is to determine whether demonstrated regional differences in the timing and controls on floods at the short time scales of the modern records hold true for the regional responses of floods to longer-term climatic variations. This broad, new perspective on flood hydroclimatology is achievable even with the relatively coarse resolution of radiocarbon dating methods. With the collaboration of Kelly Redmond, Deputy Director and Regional Climatologist for the Western Regional Climate Center, modern discharge, meteorological and atmospheric-pressure data will be analyzed to serve as analogs for the paleofloods in each region and thus aid in understanding the underlying physical bases for the patterns observed in each reg ional flood series. The study will also take advantage of recent refinements in statistical computer programs for incorporating paleoflood information into single-site flood frequency analyses (developed by the Bureau of Reclamation), and methods for the quantification and reduction of paleoflood discharge-modeling uncertainties (House, 1996). Understanding links between climate and floods from the basis of real information on the magnitude and frequency of great, rare floods will improve the ability of water-supply managers to foresee the regional consequences of glodal-and regional-scale climatic phenomena, an increasingly important component of long-term planning in the face of uncertain future climate conditions.