为什么洪水沿海岸线美国已经恶化

为什么洪水沿海岸线美国已经恶化

洪水沿海岸线美国一个著名的自然灾害。 近40% 美国人口居住在沿海县。

不同类型的洪水和改变其发生的频率有清醒的认识正向着脆弱性,在短期内,以及在未来可能产生的影响的可靠估计的关键。 鉴于对自然资源和经济活动沿海地区的严重依赖,洪水预防和安全是长期的复原能力的关键要素。

研究 发表在杂志上自然气候变化,我们组装的降雨漫长的历史记载,潮汐测量读数和飓风轨迹来评估暴雨对土地和风暴潮同时出现。 这两者的结合 - 大雨 风暴潮 主要由驱动风暴的风 - 可能会导致“复合型”洪水。

我们发现,沿美国各地的大型绵延的海岸线,沿海洪灾的两个重要驱动程序之间存在系统性的联动,使得它更可能是两者发生串联。 我们的分析表明,在过去一个世纪,复合洪水对许多美国沿海城市的数量有所增加。

获得更多的洞察频率和复合洪水的可能性可以帮助规划者更好洪水关键基础设施评估风险。

脆弱的基础设施

风暴潮和降水之间的相关性一直被洪水风险分析,在一般​​两洪水因素之一孤立了研究中被忽视。 其结果是,策划者可能低估了实际的洪水风险。

事实上,美国政府问责办公室,在七月22 2015报告题为“努力评估极端天气事件的影响,” reviewed US Army Corps of Engineers efforts to integrate changing risk from weather extremes into planning and operations of water resource infrastructure projects. The report concludes: “As the frequency and intensity of some extreme weather events are increasing, without performing systematic, national risk assessments on other types of infrastructure, such as hurricane barriers and floodwalls, the Corps will continue to take a piecemeal approach to assessing risk on such infrastructure.”

The relationship between storm surge and heavy rainfall is stronger along the Gulf and Atlantic coasts – where tropical cyclones and hurricanes often produce large storm surges and also bring significant amounts of precipitation – compared with the Pacific coast.

In the face of storm surge flooding, heavy precipitation on the land serves to accentuate its severity and impacts. In other instances, storm surge simply elevates sea water levels enough so that gravity-fed freshwater drainage is either blocked, slowed down or backed up. In this case, the inland flood potential rises dramatically, and coastal communities face the prospect of malfunctioning stormwater and wastewater infrastructure.

Commingling of the storm surge effects with runoff due to heavy precipitation has a multiplier effect on coastal infrastructure. The impacts can range from washed-out bridges to sanitation and public health concerns due to overflowing wastewater systems. And any increase in sea level would worsen the impacts from storm surges.

Meanwhile, much of the infrastructure that deals with flooding could be greatly improved. The 2013 Infrastructure Report Card issued by the American Society of Civil Engineers assigned the following grades: Levees (D-), Ports (C), Wastewater (D), Roads (D).

Better preparation

With this daunting perspective in mind, we sought to quantify the frequency of occurrence of compound flood events, as gleaned from the historical record. We were seeking to learn the spatial patterns of the risk of compound flooding, as well as its temporal variability over the past century.

For many of the large cities, including Boston, New York City, Tampa, Houston, San Diego, Los Angeles and San Francisco, we found a shift toward storm surge weather patterns that also favor high precipitation. This makes it more likely now, compared with earlier in the 20th century, that concurrent extremes would occur.

For New York City, as an example, we identified the weather situations that typically caused compound events in the past and showed that those have occurred more often over the last few decades. As a result, certain scenarios of combined storm surge and rainfall became twice more likely than they used to be in the mid-20th century. We did not seek to attribute these trends to specific climatic phenomena, but that would be an important next step.

Future research should also focus on the implications of those changes for flood risk noted in our study, including localized estimates of flood risk and the efficiency of countermeasures to mitigate the impacts of these events. At the same time, it will be important to identify linkages between the observed changes in dependency between storm surge and heavy rainfall and large-scale climate phenomena.

This, in combination with simulations performed with high-resolution climate and hydraulic/hydrological models, will allow us to look into the future and define scenarios for changes in the compound flood risk. A better understanding of these heightened risks can then be integrated into coastal adaptation planning and resilience efforts.

作者简介谈话

托马斯·瓦尔在南佛罗里达大学海洋科学博士后研究员。
Shaleen Jain是缅因大学土木与环境工程学院副教授。

本文最初发表于 谈话。 阅读 原创文章.


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