Date: Mon Jun 23 16:04:39 2008 Back to Contents

Author: Bernard Cleyet

Subject: Re: University of Iowa flooding

Post:


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Thank you Paul!

The Poisson time interval distribution is one little discussed.

The probability dP that the duration of a time interval between
events between t and t + dt is

dP = a [e^-at ] dt [ a is the mean rate, a events per unit time]

"We see at once that small time intervals have a higher probability
than large time intervals between randomly distributed
events." [Evans, The Atomic Nucleus, pp. 753 ff.]

bc thinks everyone who has listened to a G-M survey meter should
have noticed this.


On 2008, Jun 23, , at 12:28, Paul Nord wrote:

> Jerry,
>
> Isn't that just Poisson statistics?
>
> Two random events are more likely to come in timed close together
> than separated by large delays.
>
> Paul
>
>
> Jerry DiMarco wrote:
>> Dale, Megan,
>> Not to prolong this, but I heard an NPR news story last week
>> that sought to explain how an area can have two 500 yr floods so
>> close together. According to the expert they had on the program,
>> work done to contain a river together with development along its
>> shores effectively narrow the river channel. Since the river can
>> no longer spread out when it floods, that means the level has to
>> go higher. So the old definitions of 100 and 500 year floods,
>> etc. are no longer valid. He said we can expect more of these
>> events in the future, unless we restore the natural overflow areas
>> that normally accompany river systems. Hopefully the powers that
>> be were listening or are aware of this, so the money to be spent
>> in the aftermath will be allocated wisely...
>>
>> Jerry
>> P.S. A few years ago the Yellowstone River (~30 miles east of
>> here) had two 100 year floods back to back. Same problem, same
>> cause...
>
>


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small =
time=A0intervals=A0have a higher=A0probability=A0than large =
time intervals between randomly distributed events." =A0[Evans, The =
Atomic Nucleus, pp. 753 ff.]bc thinks everyone =
who has =A0listened to a G-M survey meter should have noticed this. =
=A0On 2008, Jun 23, , at 12:28, =
Paul Nord wrote:Jerry,Isn't that just =
Poisson statistics?Two random events are more =
likely to come in timed close together than separated by large =
delays.Paul<=
div>Jerry DiMarco wrote: Dale, =
Megan,=A0 =A0 Not to prolong this, but I heard an NPR news =
story last week that sought to explain how an area can have two 500 yr =
floods so close together.=A0 According to the expert they had on the =
program, work done to contain a river together with development along =
its shores effectively narrow the river channel.=A0 Since the river can =
no longer spread out when it floods, that means the level has to go =
higher.=A0 So the old definitions of 100 and 500 year floods, etc. are =
no longer valid.=A0 He said we can expect more of these events in the =
future, unless we restore the natural overflow areas that normally =
accompany river systems.=A0 Hopefully the powers that be were listening =
or are aware of this, so the money to be spent in the aftermath will be =
allocated wisely...=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =
=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =
=A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =
=A0 =A0 =A0 =A0 JerryP.S. A few years ago the Yellowstone =
River (~30 miles east of here) had two 100 year floods back to back.=A0 =
Same problem, same cause... =
=
=

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From tap-l-owner@lists.ncsu.edu Mon Jun 23 16:04:39 2008

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