密歇根新闻广播 密西根州洪水

 

Floods are changing in Michigan. We're building infrastructure¹ like they're not.

Climate change is likely to bring more extreme rainfall and flooding to Michigan. So, flood risk in the next 100 years will probably look very different than in the last. But, much of our infrastructure, like culverts, bridges, and storm drains, is still being designed and built based on the floods of the past.

There’s a culvert in the southern part of the Huron-Manistee National Forest.

The Michigan Department of Transportation built it last year to replace an older, rusted-out model. It funnels² a small creek³ under a busy state highway, M-20.

On a warm day in July, the creek is just a trickle⁴. The culvert looks like it could hold a lot more water.

In fact, it’s big enough to handle a flow rate of 255 cubic feet per second. That’s equal to about 2,000 gallons per second. So, how did MDOT arrive at that size?

The 50-year flood

When engineers build a culvert, bridge, or storm drain, they consider how long the structure is supposed to last and the largest flow it’s likely to see in that time period.

Engineers can calculate, for example, the “50-year flood” by looking at decades of historical flow data, if it’s available.

The 50-year flood is the flow that has a 2% chance of happening in any given year. You’d expect to see it about once every 50 years, based on the flows of the past.

If historical flow data isn’t available, you can still estimate flow by looking at rainfall.

For example, MDOT sized this particular culvert by using values from the 50-year rainstorm in the area.

And, the 50-year rainstorm is determined⁵ in much the same way as the 50-year flood: by looking at historical data.

"We are not climate scientists"

Kristin Schuster, an engineer with MDOT, confirms that her agency is not incorporating climate change when they size culverts, bridges or storm drains.

“We're using our existing datasets and the existing information to calculate flow rates,” she says.

But, climate scientists say we’re probably in for more intense and frequent rainstorms and flooding in the Midwest.

There’s no guarantee the 50-year flood will stay the same size. And yet, we’re still designing structures as if it will.

“You know, we have not tackled that issue to determine if we need to change those numbers,” says Schuster.

The Michigan Department of Environment, Great Lakes and Energy, or DEGLE, is responsible for calculating design flows on bigger watersheds⁶.

Susi Greiner is an environmental engineer there, and she says they aren’t accounting⁷ for climate change in their calculations, either.

“We are not climate scientists,” she says. “We are engineers. And what we have to work with is the data that exists now.”

No good method

Michigan isn’t alone here. There are also federal agencies like FEMA and the USGS involved with calculating design flows, and it’s hard for states to update when the feds haven’t.

Gabriele Villarini is an associate professor of civil and environmental engineering at the University of Iowa. He says there just isn’t a good method yet for adjusting design flows based on climate change projections⁸.

“How do we design, how do we take into account these changes now that the historical record is not necessarily representative of future conditions,” he says.

It’s difficult to figure out how climate change has already impacted floods, and consequently, how it will impact them in the future. This is because long-term, human-caused climate change isn’t the only factor. There are short-term climate cycles, too, and changes to the landscape.

Right now, Villarini is working with the U.S. Army Corps⁹ of Engineers to incorporate climate change projections into some of their designs.

He says he feels a sense of urgency, but that this kind of research takes time.

“It's a wide problem, it's a big problem, it's a recognized problem, but it's also not an easy one,” says Villarini. “And so it's one that we need to tackle with care, given what the potential repercussions¹⁰ are.... Develop something that has been vetted¹¹, verified and then put in place.”

Shifting odds¹²

Susi Greiner of DEGLE wants to stress that even though they aren’t including climate change in their flow calculations, the state requires structures to be designed on the large end – often to withstand the 100-year flood.

“So even if you're getting more intense storms more frequently, the odds are good that you're still gonna have built the structure to withstand those storms,” she says.

But, climate change is likely to keep shifting the odds on storms. And that means infrastructure will need to keep up, or risk being overwhelmed.

1 infrastructure   

n.下部构造，下部组织，基础结构，基础设施

参考例句：

• We should step up the development of infrastructure for research.加强科学基础设施建设。
• We should strengthen cultural infrastructure and boost various types of popular culture.加强文化基础设施建设，发展各类群众文化。

2 funnels   

漏斗( funnel的名词复数 )； （轮船，火车等的）烟囱

参考例句：

• Conventional equipment such as mixing funnels, pumps, solids eductors and the like can be employed. 常用的设备，例如混合漏斗、泵、固体引射器等，都可使用。
• A jet of smoke sprang out of the funnels. 喷射的烟雾从烟囱里冒了出来。

3 creek   

n.小溪，小河，小湾

参考例句：

• He sprang through the creek.他跳过小河。
• People sunbathe in the nude on the rocks above the creek.人们在露出小溪的岩石上裸体晒日光浴。

4 trickle   

vi.淌，滴，流出，慢慢移动，逐渐消散

参考例句：

• The stream has thinned down to a mere trickle.这条小河变成细流了。
• The flood of cars has now slowed to a trickle.汹涌的车流现在已经变得稀稀拉拉。

5 determined   

adj.坚定的；有决心的

参考例句：

• I have determined on going to Tibet after graduation.我已决定毕业后去西藏。
• He determined to view the rooms behind the office.他决定查看一下办公室后面的房间。

6 watersheds   

n.分水岭( watershed的名词复数 )；分水线；转折点；流域

参考例句：

• Hyetographs are important in estimating stormflow hydrographs from upstream watersheds. 降雨历线资料为上游集水区推估洪水流量历线的重要依据。 来自互联网
• Sediments check dam in small watersheds in loess hilly gully area come from three proportion, i. 黄土丘陵沟壑区治沟骨干工程泥沙淤积来源于坡面侵蚀、沟道侵蚀和库区岸坡坍塌。 来自互联网

7 accounting   

n.会计，会计学，借贷对照表

参考例句：

• A job fell vacant in the accounting department.财会部出现了一个空缺。
• There's an accounting error in this entry.这笔账目里有差错。

8 projections   

预测( projection的名词复数 )； 投影； 投掷； 突起物

参考例句：

• Their sales projections are a total thumbsuck. 他们的销售量预测纯属估计。
• The council has revised its projections of funding requirements upwards. 地方议会调高了对资金需求的预测。

9 corps   

n.(通信等兵种的)部队；(同类作的)一组

参考例句：

• The medical corps were cited for bravery in combat.医疗队由于在战场上的英勇表现而受嘉奖。
• When the war broke out,he volunteered for the Marine Corps.战争爆发时，他自愿参加了海军陆战队。

10 repercussions   

n.后果，反响( repercussion的名词复数 )；余波

参考例句：

• The collapse of the company will have repercussions for the whole industry. 这家公司的垮台将会给整个行业造成间接的负面影响。
• Human acts have repercussions far beyond the frontiers of the human world. 人类行为所产生的影响远远超出人类世界的范围。 来自《简明英汉词典》

11 vetted   

v.审查（某人过去的记录、资格等）( vet的过去式和过去分词 )；调查；检查；诊疗

参考例句：

• The recruits were thoroughly vetted before they were allowed into the secret service. 情报机关招募的新成员要经过严格的审查。 来自《简明英汉词典》
• All staff are vetted for links with extremist groups before being employed. 所有职员录用前均须审查是否与极端分子团体有关。 来自辞典例句

12 odds   

n.让步，机率，可能性，比率；胜败优劣之别

参考例句：

• The odds are 5 to 1 that she will win.她获胜的机会是五比一。
• Do you know the odds of winning the lottery once?你知道赢得一次彩票的几率多大吗？