The role of chronic and episodic disturbances on channel–hillslope coupling: the persistence and legacy of extreme floods
The role of chronic and episodic disturbances on channel–hillslope coupling: the persistence and legacy of extreme floods
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DOI：
10.1002/esp.3958
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发表时间：
2016-08
影响因子：
3.3
通讯作者：
E. Dethier;F. Magilligan;C. Renshaw;K. Nislow
中科院分区：
文献类型：
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作者：
E. Dethier;F. Magilligan;C. Renshaw;K. Nislow
景观形态代表了与复苏过程相关的不稳定事件的累积影响。大多数地貌学研究都集中在间歇性罕见事件对景观形态的作用，而对慢性输入的作用和持久性的关注较少。为了更好地确定慢性和间歇性极端事件在区域尺度上的相互作用，我们使用航空摄影和洪灾后沉积物采样来评估溪流和山坡的响应和恢复到100-300年。热带风暴艾琳在新英格兰引发的洪水。在14000平方公里的研究范围内，航空照片分析表明，风暴引发了(n=534)和重新激活(n=460)了大量滑坡。这些山体滑坡极大地增加了对区域侵蚀速率的总体估计(从0.0023毫米/年。在没有艾琳的情况下，到0.0072毫米/年。和艾琳)。同样，艾琳产生的0.25-0.5棵树/千米的LWD输入在单个事件中超过了年本底速率，这些集中的输入(101-102棵树/滑坡)可能导致特别持久和地貌有效的大堵塞和障碍。最后，我们发现，滑坡的伤痕在事件发生多年后继续提供升高的泥沙输入，这从艾琳引发的滑坡产生的溪流中持续较高的悬浮泥沙浓度得到了证明。总体而言，我们的结果表明，在构造稳定、中等起伏的系统中，罕见的高震级事件具有比以前所认识到的更重要的地貌作用。了解这些事件的作用在新英格兰等地区具有特别重要的意义，这些地区极端风暴的频率和强度预计会增加。此外，这些影响可能迫使重新考虑河流系统中的保护和恢复目标(例如，以河道形式和大量木材负载和分配)。版权所有©2016 John Wiley&Sons，Ltd.
Landscape form represents the cumulative effects of de‐stabilizing events relative to recovery processes. Most geomorphic research has focused on the role of episodic rare events on landscape form with less attention paid to the role and persistence of chronic inputs. To better establish the interplay between chronic and episodic extreme events at regional scales, we used aerial photography and post‐flood sediment sampling to assess stream and hillslope response and recovery to a 100–300 yr. flood caused by Tropical Storm Irene in New England. Within a 14 000 km2 study area, analysis of aerial photographs indicated that the storm initiated (n = 534) and reactivated (n = 460) a large number of landslides. These landslides dramatically increased overall estimates of regional erosion rates (from 0.0023 mm/yr. without Irene to 0.0072 mm/yr. with Irene). Similarly, Irene‐generated LWD inputs of 0.25–0.5 trees/km exceeded annual background rates in a single event, and these concentrated inputs (101–102 of trees/landslide) are likely to result in large jams and snags that are particularly persistent and geomorphically effective. Finally, we found that landslide scars continue to provide elevated sediment inputs years after the event, as evidenced by sustained higher suspended sediment concentrations in streams with Irene‐generated landslides. Overall, our results indicate that infrequent, high‐magnitude events have a more important geomorphic role in tectonically stable, more moderate‐relief systems than has been previously recognized. Understanding the role of these events has particular relevance in regions such as New England, where the frequency and magnitude of extreme storms is expected to increase. Further, these effects may force reconsideration of conservation and restoration targets (for example in channel form and large wood loading and distribution) in fluvial systems. Copyright © 2016 John Wiley & Sons, Ltd.