Natural Variability Has Concealed Increases in Western US Flood Hazard Since the 1970s
Natural Variability Has Concealed Increases in Western US Flood Hazard Since the 1970s
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DOI：
10.1029/2021gl097706
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发表时间：
2022-04-16
影响因子：
5.2
通讯作者：
Hall, Alex
中科院分区：
文献类型：
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作者：
Bass, Benjamin;Norris, Jesse;Hall, Alex
近几十年来，美国西部的洪水灾害总体上呈下降趋势。该地区的极端径流量受到自然变异的高度影响，这可能会掩盖或放大人为径流趋势。在这项研究中，我们利用一种称为动态调整的技术，以评估历史（1970-2020年）的年最大1天流量（Qx 1d）从美国西部的未受管制的流域，有和没有自然变化的影响。去除自然变率后，Qx 1d趋势为正（>5%）的盆地比例从25%变为53%。动力学调整后Qx 1d趋势增加（减少）的盆地表现出弱（强）干燥，而且与极端降水加剧和/或积雪大量减少有关。随着自然年代际变率的当前阶段发生变化，以及人为信号继续加强，这些流域可能会出现越来越多的洪水灾害。
Flood hazard across the western United States (US) has generally shown decreasing trends in recent decades. This region's extreme streamflow is highly influenced by natural variability, which could either mask or amplify anthropogenic streamflow trends. In this study, we utilize a technique known as dynamical adjustment to assess historical (1970-2020) annual maximum 1-day streamflow (Qx1d) from unregulated basins across the western US with and without the impact of natural variability. After removing natural variability, the fraction of basins with a positive (>5%) trend in Qx1d shifts from 25% to 53%. Basins with increasing (decreasing) Qx1d trends after dynamical adjustment exhibit weak (strong) drying, and furthermore are associated with intensifying precipitation extremes and/or large decreases in snowpack. Increasing flood hazard will likely emerge for such basins as the current phase of natural decadal variability shifts, and anthropogenic signals continue to intensify.