Channel Conveyance Variability can Influence Flood Risk as Much as Streamflow Variability in Western Washington State
Channel Conveyance Variability can Influence Flood Risk as Much as Streamflow Variability in Western Washington State
复制标题
DOI：
10.1029/2021wr031890
复制
发表时间：
2022-06
影响因子：
5.4
通讯作者：
S. Ahrendt;A. Horner‐Devine;B. Collins;J. Morgan;E. Istanbulluoglu
中科院分区：
文献类型：
--
作者：
S. Ahrendt;A. Horner‐Devine;B. Collins;J. Morgan;E. Istanbulluoglu
洪水事件的严重程度和可能性的变化通常与流量的强度和频率的变化有关，但河流输水能力的时间调整也会导致洪水灾害的变化。为了评估河道输水对洪水危害的相对重要性，我们将1930年至2020年期间华盛顿州西部50个河规的河道输水变化与中等（1.2年）洪水流量大小的变化进行了比较。在未受管制的河流中，整个区域的中度洪水有所增加，但在受管制的河流中，这一趋势受到抑制，在某些情况下甚至逆转。河道输水量的变化是普遍存在的，但调整的幅度和时间并不是区域统一的。在40%的量规下，输送量稳定而逐渐地变化。然而，更常见的是，输沙变率是非线性的，包括数十年的振荡（36%的水位计），由于异常大的泥沙供应事件（14%的水位计）引起的快速变化，以及流量调节后输沙的增加或减少（10%的水位计）。洪水风险的输送变异性的相对重要性取决于调整的模式;在历史滑坡，极端洪水和流量调节的某些位置，输送变化对洪水风险的影响匹配或超过同一地点的径流。洪水灾害管理将受益于将历史长期和短期的运输变化纳入未来洪水灾害变化的预测。
Changes in the severity and likelihood of flooding events are typically associated with changes in the intensity and frequency of streamflows, but temporal adjustments in a river's conveyance capacity can also contribute to shifts in flood hazard. To assess the relative importance of channel conveyance to flood hazard, we compare variations in channel conveyance to variations in the flow magnitude of moderate (1.2 years) floods at 50 river gauges in western Washington State between 1930 and 2020. In unregulated rivers, moderate floods have increased across the region, but in regulated rivers this trend is suppressed and in some cases reversed. Variations in channel conveyance are ubiquitous, but the magnitude and timing of adjustments are not regionally uniform. At 40% of gages, conveyance changes steadily and gradually. More often, however, conveyance variability is nonlinear, consisting of multidecadal oscillations (36% of gages), rapid changes due to unusually large sediment‐supply events (14% of gages), and increases or decreases to conveyance following flow regulation (10% of gages). The relative importance of conveyance variability for flood risk depends on the mode of adjustment; in certain locations with historic landslides, extreme floods, and flow regulation, the influence of conveyance changes on flood risk matches or exceeds that of streamflow at the same site. Flood hazard management would benefit from incorporating historic long‐term and short‐term conveyance changes in predictions of future flood hazard variability.