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posted by martyb on Wednesday May 20 2020, @01:19PM   Printer-friendly

2 Dams Fail in Michigan, Forcing Thousands to Evacuate :

Severe flooding struck central Michigan on Wednesday after two dams were breached and days of heavy rainfall, forcing the evacuation of thousands of residents and prompting officials to warn of life-threatening danger.

The failures on Tuesday of the Edenville Dam and the Sanford Dam, about 140 miles northwest of Detroit, led the National Weather Service to issue a flash flood warning for areas near the Tittabawassee River, with downstream effects expected from Midland to Saginaw overnight. Residents in nearby towns, including Edenville, Sanford and Midland, were evacuated.

Gov. Gretchen Whitmer said at a news conference on Tuesday that downtown Midland, with a population of more than 41,000, could be under nine feet of water by Wednesday morning.

[...] The Tittabawassee River was expected to crest at 38 feet by 8 a.m. Wednesday, more than four feet higher than its record of 34 feet set in 1986. The flood stage is at 24 feet.

Dow Chemical Company, based in Midland, has activated its emergency operations center and will be adjusting operations, Rachelle Schikorra, a spokeswoman, told The Associated Press.

According to Detroit Free Press:

In 2018, the Federal Energy Regulatory Commission revoked the license of the company that operated the Edenville Dam due to non-compliance issues that included spillway capacity and the inability to pass the most severe flood reasonably possible in the area.

The Edenville Dam, which was built in 1924, was rated in unsatisfactory condition in 2018 by the state. The Sanford Dam, which was built in 1925, received a fair condition rating.


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  • (Score: 2) by PiMuNu on Wednesday May 20 2020, @04:32PM (5 children)

    by PiMuNu (3823) on Wednesday May 20 2020, @04:32PM (#996961)

    > a couple of days ago we had an incredible amount of rain.

    Sure, and the paper I linked gave average rainfall rather than some measure of "extreme" rainfall events. Nonetheless, one might naively expect that if average rainfall goes up, the number of "extreme" events goes up as well. Maybe someone can find a better reference.

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  • (Score: 1) by hemocyanin on Wednesday May 20 2020, @05:03PM (4 children)

    by hemocyanin (186) on Wednesday May 20 2020, @05:03PM (#996979) Journal

    Nonetheless, one might naively expect that if average rainfall goes up, the number of "extreme" events goes up as well.

    Maybe. The average can go up because it gently rains more often too. Also, if the average was to rise, extreme events may become less likely really -- there's only so much water the atmosphere can hold and then it can hold no more -- this is why there are no rivers in the sky, so if in a worst case scenario the maximum atmospheric saturation was reach and it never stopped raining at the maximal torrential value, extreme events would fall to zero.

    • (Score: 2) by PiMuNu on Wednesday May 20 2020, @05:47PM

      by PiMuNu (3823) on Wednesday May 20 2020, @05:47PM (#996998)

      There is an article here describing various different estimators of the rainfall probability density function

      https://agupubs.onlinelibrary.wiley.com/doi/full/10.1002/2015GL063238 [wiley.com]

      TL;DR - they say a power law is a good pdf to use, i.e. p(rainfall) = Normalisation*rainfall^k = N r^k

      I guess the mean of such a distribution is given by

      Integral (p) dr = (N/k)*r^(k+1)

      so the number of extreme events does follow the mean rainfall.

      I know nothing about meteorology!

    • (Score: 2) by dry on Thursday May 21 2020, @05:06AM (2 children)

      by dry (223) on Thursday May 21 2020, @05:06AM (#997279) Journal

      Meteorologists talk about atmospheric rivers https://en.wikipedia.org/wiki/Atmospheric_river [wikipedia.org] now and again around here. The most famous one is called the Pineapple Express https://en.wikipedia.org/wiki/Pineapple_Express [wikipedia.org] as it comes from Hawaii and can dump up to 14 inches of rain in a day, one in 1862 dumped 8.5 feet.

      • (Score: 1) by hemocyanin on Thursday May 21 2020, @12:04PM (1 child)

        by hemocyanin (186) on Thursday May 21 2020, @12:04PM (#997342) Journal

        I get that -- what I'm talking about is an actual river -- not floating mists but water fish could live in. They don't exist in the sky because of gravity -- there is an upper limit to the amount of water air can hold at our gravity, pressure, temperature etc, and nothing will make it hold more. Meaning, there is some upper bound to the amount of rain physically possible and once that saturation event is reached, there will be no extreme rain because it would all be the maximal amount.

        • (Score: 2) by dry on Thursday May 21 2020, @03:08PM

          by dry (223) on Thursday May 21 2020, @03:08PM (#997404) Journal

          Some of these really do seem like a water fall from a sky river, but of course you're right in that there is a limit.