U.S. Geological Survey, Santa Cruz, CA, USA.
Water Research Laboratory, School of Civil and Environmental Engineering, University of New South Wales, Sydney, Australia.
Sci Rep. 2022 Mar 9;12(1):3848. doi: 10.1038/s41598-022-07209-0.
Wildfire and post-fire rainfall have resounding effects on hillslope processes and sediment yields of mountainous landscapes. Yet, it remains unclear how fire-flood sequences influence downstream coastal littoral systems. It is timely to examine terrestrial-coastal connections because climate change is increasing the frequency, size, and intensity of wildfires, altering precipitation rates, and accelerating sea-level rise; and these factors can be understood as contrasting accretionary and erosive agents for coastal systems. Here we provide new satellite-derived shoreline measurements of Big Sur, California and show how river sediment discharge significantly influenced shoreline positions during the past several decades. A 2016 wildfire followed by record precipitation increased sediment discharge in the Big Sur River and resulted in almost half of the total river sediment load of the past 50 years (~ 2.2 of ~ 4.8 Mt). Roughly 30% of this river sediment was inferred to be littoral-grade sand and was incorporated into the littoral cell, causing the widest beaches in the 37-year satellite record and spreading downcoast over timescales of years. Hence, the impact of fire-flood events on coastal sediment budgets may be substantial, and these impacts may increase with time considering projected intensification of wildfires and extreme rain events under global warming.
野火和火灾后的降雨对山区坡面过程和沉积物产生产生了深远的影响。然而，目前尚不清楚火洪序列如何影响下游沿海滨岸系统。现在正是研究陆地-海岸连接的好时机，因为气候变化正在增加野火的频率、规模和强度，改变降水率，并加速海平面上升；这些因素可以被理解为海岸系统的对比性的堆积和侵蚀因素。在这里，我们提供了加利福尼亚州大苏尔的新卫星衍生的海岸线测量结果，并展示了河流泥沙排放如何在过去几十年中显著影响海岸线位置。2016 年的一场野火和随后的创纪录降水增加了大苏尔河的泥沙排放量，导致过去 50 年中河流泥沙总负荷的近一半（约 2.2Mt 至 4.8Mt）。据推断，大约 30%的河流泥沙为滨岸级砂，并被纳入滨岸单元，导致了 37 年来卫星记录中最宽的海滩，并在数年的时间内向下延伸到沿海地区。因此，火洪事件对沿海泥沙预算的影响可能是巨大的，并且考虑到野火和极端降雨事件在全球变暖下的预期加剧，这些影响可能会随着时间的推移而增加。
