Two 500-year floods in 15 years

By: Dr. Jeff Masters , 2:48 PM GMT on June 19, 2008

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The U.S. Geological Survey has preliminary data showing that this month's floods on four of Iowa's rivers--the Cedar, Iowa, Shell Rock, and Wapsipinicon--were 500-year floods. Back in 1993, many rivers in the Midwest also experienced 500-year floods, so the region has endured two 500-year floods in the past 15 years. How can this be? First of all a definition--a 500-year flood is an event that has only a 0.2% chance of occurring in a given year, based on available river flow data. Of course, reliable data only goes back a century at most, so designation of a 500-year flood event is somewhat subjective. Still, it seems rather improbable that two such huge floods should occur within such a short time span, raising the question of whether the floods were, in part, human-caused.

In a provocative story in the Washington Post today, it was pointed out that part of the flooding is due to the draining of wetlands for farming purposes. As nature's natural buffers against flooding are drained and filled to provide room for more farmland, run-off and flooding are bound to increase. Furthermore, as more levees are built to protect more valuable farmland and new developments, flood waters are pushed out of the former areas they were allowed to spread out in and forced into river channels behind the new levees. Even higher levees must then be constructed to hold back the increased volume of water they are asked to contain.

Climate change contributing to flooding?
The heaviest types of rains--those likely to cause flooding--have increased in recent years (see my February blog, "The future of flooding", for more detail). According to the United Nations' Intergovernmental Panel on Climate Change (IPCC) 2007 report, "The frequency of heavy precipitation events has increased over most land areas". Indeed, global warming theory has long predicted an increase in heavy precipitation events. As the climate warms, evaporation of moisture from the oceans increases, resulting in more water vapor in the air. According to the 2007 IPCC report, water vapor in the global atmosphere has increased by about 5% over the 20th century, and 4% since 1970.

Over the U.S., where we have very good precipitation records, annual average precipitation has increased 7% over the past century (Groisman et al., 2004). The same study also found a 14% increase in heavy (top 5%) and 20% increase in very heavy (top 1%) precipitation events over the U.S. in the past century. Kunkel et al. (2003) also found an increase in heavy precipitation events over the U.S. in recent decades, but noted that heavy precipitation events were nearly as frequent at the end of the 19th century and beginning of the 20th century, though the data is not as reliable back then. Thus, climate change is likely partly to blame for increased flooding in the U.S., although we cannot rule out long-term natural variations in precipitation.


Figure 1. Forecast change in precipitation and runoff for the period 2080 to 2099 compared to 1980 to 1999. The forecasts come from the A1B scenario from multiple climate models used for the Intergovernmental Panel on Climate Change (IPCC) 2007 report.

The forecast
According to a multi-model consensus of the climate models run for the Intergovernmental Panel on Climate Change (IPCC) 2007 report, precipitation and river runoff for the Mississippi River drainage basin are expected to increase only slightly by the end of this century (Figure 1). However, more of this rain is expected to fall in heavy precipitation events, the ones most likely to cause flooding. As a result, the U.S. needs to prepare for an increase in the number and severity of 100-year and 500-year flooding events in the coming century.

References
Kunkel, K. E., D. R. Easterling, K. Redmond, and K. Hubbard, 2003, "Temporal variations of extreme precipitation events in the United States: 1895.2000", Geophys. Res. Lett., 30(17), 1900, doi:10.1029/2003GL018052.

Groisman, P.Y., R.W. Knight, T.R. Karl, D.R. Easterling, B. Sun, and J.H. Lawrimore, 2004, "Contemporary Changes of the Hydrological Cycle over the Contiguous United States: Trends Derived from In Situ Observations," J. Hydrometeor., 5, 64.85.

Tropics
It's quiet in the tropics. There are no threat areas to discuss, and none of the models are forecasting tropical storm formation in the next seven days.

Jeff Masters

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1404. pearlandaggie
4:48 PM GMT on June 22, 2008
msphar...what make/model of sailboat do you have? i sold my Catalina 27 earlier this year.
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1403. msphar
4:41 PM GMT on June 22, 2008
I guess I just prefer short handed, decision making much easier, execution suffers I grant you but if there are strong conflicts in personalities 44 feet doesn't allow much room for separation, especially in a competitive environment.

Trolling is always an option on the water but I wouldn't recommend it.
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1402. guygee
4:43 PM GMT on June 22, 2008
I have been on the AgWeb site reading posts from farmers who live and die by the weather. I thought some people might find this thread describing the impact of the flooding on this years corn crop especially interesting: Link. I posted a couple of highlights below.

"IA CORN FARMER:
Posted - 06/16/2008 : 8:15:42 PM
The % Harvested Acres is usually around 91%. 1992=72.2/79.3=91.05%. 1993=63.0/73.3=85.95%!!!! Look at the 1993 Yield=100.7 bu/a!!!!

If IA has lost 3,000,000A, IL has probably lost 2 mil and IN probably .5 mil. That's 5.5mil A. USDA was saying 86 mil acres. If the yield drops to 140 bu/A, The June 30 Corn S&D would look like this:

Planted Acres 80.5 mil acres
Harvested Acres x 91%= 73.26
Yield 140
Beginning Stocks 1,143 mil bu
Production 10,256
Imports 15
Total Supply 11,414
Feed and residual 5,150
Food and seed 1,360
Ethanol (9bil gal Mandate)3,214
Total Domestic Use 9,724
Exports 2,000
Total Use 11,724
Ending Stocks -310

We obviously can not have negative ending stocks. $8-9-10 corn is going to cut Feed, Ethanol, and Exports. If we just cut EXPORTS 1 bil bu, we would have Ending Stocks=690 mil bu.

Obviously, something is going to have to give. I encourage all readers to make their own Corn S&D and post it."
----
IA CORN FARMER -
Posted - 06/19/2008 : 6:10:43 PM
...the reason I have not cranked down ethanol use is that I believe at least 20% and now could be 30% of all 2008 corn is already out of the farmers hands. Meaning that it has been forward contracted in the 5.50-6 range, alot with the ethanol plants. Real common here for many in corn country to hedge this way, talking around my area, I would say 20% before the flood, higher percent now with reduced yields...
----
IA CORN FARMER
Posted - 06/21/2008 : 7:43:26 PM
Iowa55- you are right, this is worse than the Titanic. At least on the Titanic we could put alot of the women/children on lifeboats. Then we could go to the ships bar and drink expensive Brandy and die like men. On our ship the "USS FARM" there are no lifeboats for the women/children and the most expensive bottle I have is Ten High Bourbon, $8.99 per liter.

farmgirl- do not think we have a handle on total acres lost in mine yet, but certainly increasing. My beans today were not submerged, looked ok but had damp off. You could pull them out by the roots very easy. The root structure was gone/rotted.They looked ok 3-4 days ago. [...]
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1401. pottery
12:29 PM AST on June 22, 2008
456, WUnderful update by you. Very pertinent and timely. Thanks. You keep doing that. Its appreciated.
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1400. pearlandaggie
4:39 PM GMT on June 22, 2008
1397. not much there....

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1399. msphar
4:34 PM GMT on June 22, 2008
I remember riding the ferry from Bacolod to Iloilo, a much shorter ferry ride. Sad to ponder the fate of those souls so recently lost.
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1398. pearlandaggie
4:36 PM GMT on June 22, 2008
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1397. 0741
4:34 PM GMT on June 22, 2008
it look like central atlantic wave weaking alot
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1396. Orcasystems
4:32 PM GMT on June 22, 2008
1394. msphar 4:32 PM GMT on June 22, 2008 Hide this comment.
44 foot and a crew of 8! Well they will surely learn something about group dynamics in the process.
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Not to bad if your sailing 1&2 gives you three people to a watch.. its actually not to bad. Never more then 4 people sleeping at a time.

Your right about the dynamics, I know Hale has been tempted once or twice to use one for trolling for sharks.
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1395. pearlandaggie
4:30 PM GMT on June 22, 2008
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1394. msphar
4:28 PM GMT on June 22, 2008
44 foot and a crew of 8! Well they will surely learn something about group dynamics in the process.
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1393. Patrap
11:29 AM CDT on June 22, 2008
Current GOM IR Loop Link

Gulf of Mexico (Updated every ~10-15 mins.)
GOES Imagery
3 Channels, IR,WV and Low Cloud VisibleLink
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1392. pearlandaggie
4:28 PM GMT on June 22, 2008
Fengshen looks to be strengthening...i wonder if the Cat1 status throughout the forecast period will hold...impressive cooling of the cloudtops.

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1391. Orcasystems
4:25 PM GMT on June 22, 2008
1383. msphar 3:47 PM GMT on June 22, 2008
Orcasystems - I see the crew wow! there's a lot of hands.
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Believe it or not, all of the crew members pay to be on the crew. Hale is an open ocean sailing instructor, and those all students.
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1390. pearlandaggie
4:24 PM GMT on June 22, 2008
if the path is correct, looks like western taiwan is in for a surprise!

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1389. pearlandaggie
4:22 PM GMT on June 22, 2008
looks like some of the trolls went back to lurking! LOL
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1388. pearlandaggie
4:20 PM GMT on June 22, 2008
i'm here, cat. it did get quiet!
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1387. catastropheadjuster
4:19 PM GMT on June 22, 2008
Hello anyone out there? I guess i will go wash clothes and stuff. see u all later.
Sheri
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1386. catastropheadjuster
4:15 PM GMT on June 22, 2008
LO- Nope there's plenty of moisture out there just hope we get some more here in Lower Alabama. We got drizzle rain this morning, that's about it.
sheri
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1384. catastropheadjuster
4:09 PM GMT on June 22, 2008
Hey Where did everyone go?
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1383. msphar
3:46 PM GMT on June 22, 2008
Orcasystems - I see the crew wow! there's a lot of hands.
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1382. msphar
3:32 PM GMT on June 22, 2008
Orcasys - nice boat, how many in the crew ?
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1381. trunkmonkey
3:36 PM GMT on June 22, 2008
Folks, i'm comin to Bradenton Beach, on July 6th, thru the 14, hows the models on GFS look for Florida during that time period? glad the blogs are in a slow period!
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1380. txalwaysprepared
3:28 PM GMT on June 22, 2008
456 We do need the rain. Have a drought going on :( Although this week we did get some rain.
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1379. Weather456
11:23 AM AST on June 22, 2008
Also the next series of tropical waves will exit Africa either near 10N or northward. The AEW that is over EAFRICA is along 19E with its vort max at 11N.

Classic and strong AEW becuz it can be detected over the terrain of EAFRICA, which is uncommon for June waves. It is the August and September waves normally amplified this far east.

There is possible another one ahead of this wave near the Prime Meridian.

Tropical Update

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1378. pearlandaggie
3:29 PM GMT on June 22, 2008
later, atmo! good luck with them young 'uns! :)
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1377. atmoaggie
3:23 PM GMT on June 22, 2008
1366. LOL! I love the storms, I really do. But dealing with three young kids (4 1/2, 2 1/2 & 8m) during a storm is truly the source of my neurotic state. :)

Mine was that way before the kids, but now we have a very similar set of little ones to yours. 3 1/2, 20 m, 8m. These 3 are the reason I am more of a user of the intelligent contributions here than a contributor.

currently have a 3year old shouting from 2 feet away and the 20m in lap squirming like a just-caught fish. Later all.
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1376. Orcasystems
3:26 PM GMT on June 22, 2008
1375. jphurricane2006 3:24 PM GMT on June 22, 2008 Hide this comment.
damn I almost sounded smart in post 1373 lmao
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Yup, almost :)

Thanks JP
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1374. Weather456
11:21 AM AST on June 22, 2008
1372. nash28 11:21 AM AST on June 22, 2008
One last thing... Checking the NAO phase it is pretty clear to me that with the negative NAO July-September may get very busy.


Agreed. But I can only see into July. Do you have a link for August and September.
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1372. nash28
11:20 AM EDT on June 22, 2008
One last thing... Checking the NAO phase it is pretty clear to me that with the negative NAO July-September may get very busy.
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1371. Weather456
11:20 AM AST on June 22, 2008
txalwaysprepared,

the steering flow is weak...so all bets are open where the blob will go. Hope it does go north to yall, if you guys need the rain, that is.
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1370. Weather456
11:17 AM AST on June 22, 2008
It seems most are in agreement with the next MJO pulse. It is expected to be stronger than the last one that help spawned Alma-Arthur. I love saying "Alma-Arthur"....lol...lol
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1369. txalwaysprepared
3:16 PM GMT on June 22, 2008
1366. LOL! I love the storms, I really do. But dealing with three young kids (4 1/2, 2 1/2 & 8m) during a storm is truly the source of my neurotic state. :)
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1368. nash28
11:16 AM EDT on June 22, 2008
Hey guys... At work for the moment. Got paged in. Just looked out the windows of the 5th floor in the hospital and it POURING! It's coming down in buckets right now near Raymond James stadium. Now, gotta get back in the car for the long wet drive back to Apollo Beach.

See y'all later.
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1367. Orcasystems
3:14 PM GMT on June 22, 2008
1364. jphurricane2006 3:12 PM GMT on June 22, 2008 Hide this comment.
correction we had 93E lol, navy site took it down and by the looks of it I dont blame them lol
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Its from Victoria BC to Maui HI
They start at 10 am Pacific time.
Here is the website for the race
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1366. atmoaggie
3:14 PM GMT on June 22, 2008
then again everything makes me nervous ;)

Hmmm, wife has that disease. Could it be...nah, not going to say it all the way.
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1365. txalwaysprepared
3:12 PM GMT on June 22, 2008
rain. After TS Allison forming so quickly the BOC and Gulf make me nervous. LOL. But then again everything makes me nervous ;)
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1363. pearlandaggie
3:10 PM GMT on June 22, 2008
1359. i would be careful what i ask for! remember Humberto from last year? i would rather just have these daytime heating showers. :)
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1361. rainraingoaway
9:06 AM CST on June 22, 2008
Well, going camping later in the week. Everytime we go it seems to rain, lol. Forcasters not calling 4 rain, tho. Would be our luck something forms from nothing!
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1360. Orcasystems
3:09 PM GMT on June 22, 2008
JP & StormW

Here is one for you, whats the chances of anything brewing on the Pacific side in the next 5-10 days? The VicMaui Race is on and my Brother in Law is skipping his boat on it. The race starts in about 2 hours.

For anyone interested or following the race, his is the Turicum a C&C 44.
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1359. txalwaysprepared
3:06 PM GMT on June 22, 2008
456. I was going to ask.. it looked like the wave had moved quite a bit. But I wasn't sure.

I would like that BOC Blow up to go straight north to Houston. I need as much water/rain as I can get for my newly planted trees :)
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1358. txalwaysprepared
3:02 PM GMT on June 22, 2008
1354. We have had some nice storms come through this past week, but not as much rain as I would expect with those kind of storms. I guess some places did get lots, but not here.

Not sure about the BOC. I'm guessing it's typical showers, but as soon as I say that it will blow up LOL
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1357. Weather456
10:47 AM AST on June 22, 2008
This is how quickly waves can gain latitude



Blowup in the BOC



Tropical Update
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1356. ajcamsmom2
3:03 PM GMT on June 22, 2008
Wasn't the real StormTop sick last year??? Is he better???
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1354. rainraingoaway
8:57 AM CST on June 22, 2008
Good morning all.

Nice pics txalways. Sure was some spooky weather yesterday. We had hail and some fierce winds. Limbs down around town. Finally got 3/4 inch of rain. Hooray! Through all the mess around Houston the past few days thats all my little town has gotten.

See a blowup in the BOC. Another blob?
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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.