The storm that swept across the Rockies in September 2013 unleashed huge amounts of sediment downstream, doing the work of a century of erosion. Julia Rosen reports.

2013年9月席卷落基山脉的风暴向下游倾泻了大量的沉积物，而自然侵蚀完成这一过程需要一个世纪。朱莉娅·罗森报道。

撰文/播音：朱莉娅·罗森（Julia Rosen）

翻译：郭鑫鹏

审校：李轩

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.

2013年，一场罕见的九月风暴席卷了科罗拉多平原。当它抵达落基山脉时，在博尔德这样的地方降下了超过了一英尺的雨量，这与这个城市一整年的降雨量相当。这场降雨引发了致命洪水和山崩，摧毁了道路和建筑。一项新研究发现，往往要一个世纪积累的侵蚀和沉积仅在这在短短几天中发生了。

“Once the flooding started, it happened quickly, and took a lot of people unawares.”

“洪水一旦发生，它就会进展得非常迅速，让人猝不及防。”

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.

柯林斯堡科罗拉多州立大学地理学家萨拉·拉斯本便亲自经历了这场风暴。从建筑的损害情况中，拉斯本得知洪水带来了大量的沉积物、木头，以及它们包含的有机碳。之后她发现了一个可以准确统计各种成分的绝佳机会：一个位于洪水流向转折点的水库捕获了冲下来的所有东西。

“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.”

“我一直在考虑否能够追踪沉积物从源头到这个被我称为“人造水池”的水库之间的过程，以及能否对其加以量化。通常，我们无法得到大风暴产生的所有东西……但这次水库却收集到了所有东西，这对我们来说是一个绝佳的机会。”

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 yards 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.

所以拉斯本和她的同事获得了国家科学基金会应急研究的一项经费，来研究到底发生了什么。这个团队比较了风暴前后景观和湖床的细节图，然后定量分析了其中的差异。他们发现，在此次风暴中，一共有50万立方英码的沉积物被冲到了下游，这样体积的沉积物通常需要115年的自然侵蚀。这些沉积物的60%被冲进了水库，占了其2%的存储空间。

The rest of the material was deposited partway down the river, 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. [S. L. Rathburn et al., The fate of sediment, wood, and organic carbon eroded during an extreme flood, Colorado Front Range, USA]

其余物质沉积在了河流中途，它们会在接下来的几年中陆续到达水库，拉斯本说，这会让水库管理者持续头疼的…另外他们还得担心大型木头阻塞排水口。这个发现发表在期刊《地质学》上。

The storm was an extreme event. But Rathburn says such episodes are becoming more and more common.

这场风暴是极端天气。但是拉斯本说这样的情形会变得越来越常见。

“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.”

“我认为它是气候变化引起的。我们的研究和调查绝对是有价值并且必要的。考虑到居住在灾害发生地人们，我们决不可以视而不见，而这样的危险几乎在任何地方都有可能发生。”

-Julia Rosen