This is Scientific American — 60-Second Science. I'm Julia Rosen.
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In 2013, a rare September storm swept across the plains of Colorado. When it hit the Rockies, it dropped more than a foot of rain in places like Boulder—as much as the city sees in an entire year. The rain unleashed deadly floods and landslides that swept away roads and buildings. In fact, a new study found that a century's worth of erosion and sedimentation took place in a matter of a few days.
"Once the flooding started, it happened quickly, and took a lot of people unawares."
Sara Rathburn, a geoscientist at Colorado State University in Fort Collins who experienced the storm herself. On top of the damage to manmade structures, Rathburn knew that the floods moved huge amounts of sediment, wood, and the organic carbon they contain. She saw a unique opportunity to put hard numbers on what went where: At the base of one of the watersheds that flooded, a reservoir captured everything that flowed downhill.
"I was thinking about being able to track the sediment from the source to what I'm calling this anthropogenic sink—the reservoir—and really quantify it. We don't have a lot of control on absolutely capturing everything that these large storms produce...and so the fact that the reservoir was capturing everything really seemed like a unique opportunity."
So Rathburn and her colleagues got a Rapid Response Research grant from the National Science Foundation to study what happened. The team compared detailed maps of the landscape and the lakebed before and after the storm, then they quantified the difference. They found that half a million cubic meters of sediment washed downstream during the storm, a volume that would normally take up to 115 years to erode. About 60 percent of it accumulated in the reservoir, taking up 2 percent of its storage space.
The rest of the material was deposited partway down the catchment, where it will continue to be released into the reservoir for years to come, Rathburn says, causing ongoing headaches for dam managers...who are also worried about large logs clogging the openings that they use to release water. The findings are in the journal Geology.
The storm was an extreme event. But Rathburn says such episodes are becoming more and more common.
"I really do think it's climate-change driven. And that it's something that's just absolutely worthy and necessary of our study and our investigation. It's too risky to ignore, given what it means for people living in places where hazards occur, which is almost everywhere."
Thanks for the minute for Scientific American — 60-Second Science Science. I'm Julia Rosen.
2013年9月一场罕见的风暴席卷了科罗拉多平原 。风暴侵袭洛基山脉时，使博尔德等地的降雨量超过一英尺，这相当于这座城市一整年的降雨量 。暴雨引发了致命的洪水和山体滑坡，冲走了建筑、冲毁了道路 。事实上，一项新研究发现，在短短几天的时间内可以形成相当于一个世纪的侵蚀和沉积 。
莎拉·拉斯伯恩是科罗拉多州立大学的地球科学家，她本人就曾亲身经历过风暴 。除了毁坏人造建筑以外，拉斯伯恩知道洪水还会搬运大量沉积物、木头以及二者所含的有机碳 。她发现了一个难得的机会，可以准确计算这些物质去了哪里：在一个泛滥水域的底部，一个水库拦截了流向山下的所有物质 。
“我将这个水库称之为‘人工水槽'，我想追踪沉积物的范围可以设定在源头和水库之间，然后对沉积物进行量化 。我们对完全采集大型风暴所产生的一切没有太多控制力，所以，水库捕获一切物质看起来像一次绝佳的机会 。”
所以，拉斯伯恩和她的同事获得了美国国家科学基金会为“快速响应研究”项目提供的资助，得以进行研究 。研究团队比较了风暴发生前后陆上景观和湖底景观的明细图，然后他们对差异进行了量化 。他们发现，在暴风雨期间，有50万立方米的沉积物被冲到下游，通常这种体积的沉积物需要115年的侵蚀才会形成 。大约60%的沉积物累积在水库中，占水库储存空间的2% 。
其余的沉积物一部分聚积在集水区，未来几年这些沉积物也会继续流入水库，拉斯伯恩表示，这种情况会继续让大坝管理者头疼，同样令他们感到担心的，还有大木头堵塞泄洪出口的问题 。这项研究结果发表在《地质学》期刊上 。
暴风雨曾是一种极端事件 。但是拉斯伯恩表示，现在这种事件正变得越来越普遍 。
“我真的认为这是气候变化造成的 。这绝对是值得我们研究和调查的主题，同时也是有必要的 。考虑到这对生活在危害发生地的居民的意义，这种现象太过危险所以无法无视，而且现在灾害几乎无处不在 。”
谢谢大家收听科学美国人——60秒科学 。我是朱莉娅·罗森 。
1. take place （尤指在控制或组织下）发生，进行，举行；
例句：The official opening of the store will take place next week.
2. on top of 另外；加之；除…之外(还)；
例句：I have a small pension, on top of my salary.
3. be able to 可以…的，能够…的；
例句：The athlete is able to jump two meters.
4. take up 占用，花费；
例句：Email should take up only a small portion of your day, maybe 30 minutes at most.