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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1454. msphar
8:21 PM GMT on June 22, 2008
Drak, Thanks. I understand the implication leading on from there. Will continue to watch the Tropical Surface Analysis. The H looks good for now, but I notice they move around from time to time.
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1453. pearlandaggie
8:21 PM GMT on June 22, 2008
GoM blob less impressive than earlier...

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1452. 305st0rm
8:20 PM GMT on June 22, 2008
negative NAO causes weak subtropical highs
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1451. Drakoen
8:18 PM GMT on June 22, 2008
1450. msphar 8:18 PM GMT on June 22, 2008
Staying simplistic "negative North Atlantic Oscillation" is what ? and leads to what ??


Weaker Azores/Bermuda High.
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1450. msphar
8:14 PM GMT on June 22, 2008
Staying simplistic "negative North Atlantic Oscillation" is what ? and leads to what ??
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1449. 305st0rm
8:08 PM GMT on June 22, 2008
what does "ENSO Neutral" mean for the Atlantic MDR ???

Higher than normal SST's
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1448. Drakoen
8:06 PM GMT on June 22, 2008
1445. msphar 8:04 PM GMT on June 22, 2008
So Drak, simplistically what does "ENSO Neutral" mean for the Atlantic MDR ???


Negative NAO most likely, slightly weaker than normal subtropical ridge. Neutral years have shown to have more tropical cyclone activity i.e. 2005. Some of the La Nina circulation patterns will be still be present with below average vertical wind shear.
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1447. Drakoen
8:05 PM GMT on June 22, 2008
1439. BahaHurican 7:59 PM GMT on June 22, 2008
Question: With the high set up as it forecast to be on Wed (pictured below), where would a hurricane already in the CAR most likely make landfall?


Central America.
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1446. Drakoen
8:02 PM GMT on June 22, 2008
1440. BahaHurican 8:01 PM GMT on June 22, 2008
Hey Drak. Re: 1438. That doesn't even seem to suggest that the bulk of the models expect a serious trend towards el nino.


Right. Always go with the consensus which the dynamical and statistical forecast means show ENSO neutral conditions.
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1445. msphar
8:00 PM GMT on June 22, 2008
So Drak, simplistically what does "ENSO Neutral" mean for the Atlantic MDR ???
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1444. HurrikanEB
8:04 PM GMT on June 22, 2008
I don't know if anyone has posted this already.

RELAYED BY NATIONAL WEATHER SERVICE COLUMBIA SC
108 PM EDT SUN JUN 22 2008

...CHILD ABDUCTION EMERGENCY...

WE HAVE JUST RECEIVED THIS IMPORTANT ANNOUNCEMENT REGARDING AN
ABDUCTED CHILD IN MENDENHALL ROAD AREA OF DORCHESTER COUNTY.

THE SOUTH CAROLINA STATE LAW ENFORCEMENT DIVISION IS LOOKING FOR
MCKENIA BRAELYN WRIGHT...A BLACK FEMALE. AGE 11 MONTHS. HEIGHT 21
INCHES. BLACK HAIR AND BROWN EYES. THE CHILD WAS LAST SEEN AT
MENDENHALL ROAD IN SUMMERVILLE SOUTH CAROLINA AND IS BELIEVED TO
BE IN EXTREME DANGER. THE CHILD WAS LAST SEEN WEARING A WHITE
SHORT ONE PIECE WITH RED BIB.

AUTHORITIES ADVISE THE CHILD WAS LIKELY ABDUCTED BY JASMINE LAYRE
WRIGHT. THEY MAY BE TRAVELING IN A 2006 FORD ESCAPE WITH SOUTH
CAROLINA TAGS 528 UXZ. DIRECTION OF TRAVEL WAS UNKNOWN.

IF YOU HAVE ANY INFORMATION REGARDING THIS ABDUCTION, CALL LAW
ENFORCEMENT IMMEDIATELY.

THE FOLLOWING MESSAGE IS TRANSMITTED AT THE REQUEST OF THE SOUTH
CAROLINA LAW ENFORCEMENT DIVISION IN COLUMBIA SOUTH CAROLINA.

$$
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1443. 305st0rm
8:02 PM GMT on June 22, 2008
I don't think el niƱo will make it into the picture throughout the entire 2008 season
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1442. 305st0rm
8:00 PM GMT on June 22, 2008
The Azores high is predicted to stay weak, enhancing sst's in the ATL
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1441. severstorm
3:55 PM EDT on June 22, 2008
Xoendhoroeken, hey so what did you all get down there i myself only got .06 again cant understand this heck of a lines comming at me and poof it was gone and yes i'll take some water well getting low LOL
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1440. BahaHurican
3:59 PM EDT on June 22, 2008
Hey Drak. Re: 1438. That doesn't even seem to suggest that the bulk of the models expect a serious trend towards el nino.
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1439. BahaHurican
3:44 PM EDT on June 22, 2008
Question: With the high set up as it forecast to be on Wed (pictured below), where would a hurricane already in the CAR most likely make landfall? I'm especially looking at the 1016 isobar and wondering how much closer to the high a moderate 'cane would be likely to get.

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1438. Drakoen
7:43 PM GMT on June 22, 2008
Consensus remains ENSO neutral conditions.
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1437. XoendHoroeken
3:38 PM EDT on June 22, 2008
Wow. In the next few days St. Croix is expected to receive gusts to some 50 mph. PR's winds will be gusty as well.
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1436. Drakoen
7:34 PM GMT on June 22, 2008
The ECMWF released their month seasonal probability forecasts today.

Little bit of a change as far as the Mean Sea Level Pressure anomalies. Average anomalies south of 20N. Anomalous Pressures -1mb are most prevalent north of 20N. Anomalous Pressures -2mb are noted in the mid Atlantic.
Photobucket

One of the things to monitor are the precipitation patterns as tropical cyclones produce anomalous higher precipitation in over a given area. The forecast for July-August-September feature above-average precipitation of the African coast some 200mm in the 70%-100% tercile. The precipitation patterns do feature a more meridionally oriented pattern in the mid-atlantic with the WNW track and a more zonal pattern through the Bahamas with above average precipitation in the 50-100mm range in the tercile of 70%-100%. It should be noted that the regions in the Caribbean and most of the MDR, the ecmwf forecast for below average precipitation through the JAS period but coming to more average in the October November months like featured from the CFS.
Photobucket
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1435. stormdude77
2:52 PM AST on June 22, 2008
1433. WeatherfanPR 2:44 PM AST on June 22, 2008

Yeah, it's expected to be very windy across here tomorrow and lasting into tuesday evening/night...
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1434. melwerle
6:53 PM GMT on June 22, 2008
ah...3 pm...naptime.

Catch everyone later...
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1433. WeatherfanPR
6:38 PM GMT on June 22, 2008
Area forecast discussion
National Weather Service San Juan PR
1222 PM AST sun Jun 22 2008

Active tropical wave across the central Atlantic just coming on the
edge of our cropped AWIPS satellite imagery. This wave has a classic
Nevada-sv couplet...with Nevada...or wind surge...racing across 50w at this time.
This wind surge...and associated aej and moisture...is forecast
by GFS to move into the local area first thing Monday morning and
produce very squally weather with strong gusty winds. This wave
will likely produce broader and more frequent squalls than the
last tropical wave on Friday...aided by a 35-40 knots aej and sal on
periphery of this low level wind surge. Most significent weather may
shift northwest across the vi and into the local and offshore Atlantic
waters. Recent forecast have begun to address this...and no
changes to synoptic reasoning at this time.
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1432. weathermanwannabe
2:40 PM EDT on June 22, 2008
From AP:

President Gloria Macapagal Arroyo, who left for the United States late Saturday, talked to officials in a teleconference aired live on nationwide radio Sunday, scolding coast guard officials for allowing the ferry to leave Manila late Friday despite the bad weather.strong>

What were they thinking............
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1431. BahaHurican
2:36 PM EDT on June 22, 2008
Afternoon everybody. I'm watching this line of showers that seems to be popping up. I'm engaged in some outdoor activities and would really prefer not to be rained on today LOL.

It's really hot / humid this afternoon, though, so I won't be surprised if we do get a downpour.

BBL . . .
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1430. melwerle
6:39 PM GMT on June 22, 2008
Too funny MS...love the lightning (hate the bruises)...that's my baby though - love the class and the folks have been great to my daughter (bought the boat for her for her birthday). That's the avatar photo...racing in St. Pete (I'm middle crew). The 420 photo is my daughter...mean MEAN skipper...sometimes I would like to toss her overboard during regatta. She's become a bit more humble sailing the lightning though...a bit more difficult to sail with all the lines.
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1429. weathermanwannabe
2:34 PM EDT on June 22, 2008
1420. all4hurricanes 1:54 PM EDT on June 22, 2008
155 people are dead in the Philippines there was some massive flooding and mudslides and a Ferry that sank with 700 people on board most presumed dead.


Just logged on and read the news with regard to the ferry incident in the Phillipines; WHY somebody is running a ferry (with hundreds of men/women/children aboard) in "Typhoon" type conditions or nearby is beyond me; The Captain/Company that sailed under those condiitons should be held liable......
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1428. BahaHurican
2:19 PM EDT on June 22, 2008
1420. all4hurricanes 1:54 PM EDT on June 22, 2008
155 people are dead in the Philippines there was some massive flooding and mudslides and a Ferry that sank with 700 people on board most presumed dead.


Not surprised am I. That storm (Fengshen) went further west than expected, and I'll bet a lot of people didn't get the full info about it before it was right over their heads.

Sad to hear about the loss of life, especially the potential losses on the ferry where perhaps it might have been avoided.
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1427. txalwaysprepared
6:28 PM GMT on June 22, 2008
It almost looks (to my crazy eyes) that the boc storms want to follow the rest of the showers into FL.
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1426. msphar
6:10 PM GMT on June 22, 2008
Tx count on it, there is always another wave behind the wave. Never turn your back for too long.
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1425. XoendHoroeken
2:10 PM EDT on June 22, 2008
em1418. severstorm 1:50 PM EDT on June 22, 2008 Hide this comment.
1416 looks whats comming in from the west again and again .09 of rain for z-hills just cant get the rain to stay together to get here then blows up agaian after going threw here amazing.

Wow. I should divert the little streams I have forming in my field up toward you there lol. my cypress swamp was high and dry last week but now is spilling into my lawn. And that stuff off to the West looks pretty nasty doesn't it? I can hear the boomers already
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1424. msphar
6:07 PM GMT on June 22, 2008
Mel, Lightning is venerable old class which I recall from a misspent youth, but that 420 looks like one slick slipper.
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1423. txalwaysprepared
6:06 PM GMT on June 22, 2008
Question from the neurotic mom here.

What's he deal with the BOC blob? Anything stearing those showers to one place or another?

And is that another wave behind the wave?
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1422. melwerle
5:57 PM GMT on June 22, 2008
Way cool boat - would love to crew on that! Right now just gotta stick to my lightning and crewing for someone else on their bigger boat on the weekends...

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1421. msphar
5:49 PM GMT on June 22, 2008
Pearl was referring to the pictures I have posted showing the US Coast Guard intercepting my boat and boarding before we reached Boqueron, PR. We had a smooth crossing that day.
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1420. all4hurricanes
5:53 PM GMT on June 22, 2008
155 people are dead in the Philippines there was some massive flooding and mudslides and a Ferry that sank with 700 people on board most presumed dead.
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1419. stormdude77
1:49 PM AST on June 22, 2008
Tropical update
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1418. severstorm
1:45 PM EDT on June 22, 2008
1416 looks whats comming in from the west again and again .09 of rain for z-hills just cant get the rain to stay together to get here then blows up agaian after going threw here amazing.
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1417. 305st0rm
5:48 PM GMT on June 22, 2008
Link
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1416. XoendHoroeken
1:36 PM EDT on June 22, 2008
1411. msphar 1:06 PM EDT on June 22, 2008 Hide this comment.
Pearl, yes that was in the Mona just off the Hour Glass Shoal, which can be very ruough water at times, between Hispaniola and Puerto Rico.


What are you referring to? What was in the Mona? I looked at the past entries but couldn't find what you're talking about.
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1415. pearlandaggie
5:18 PM GMT on June 22, 2008
well, i'm out for now. BBL
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1414. pearlandaggie
5:16 PM GMT on June 22, 2008
1413. i'd bet so. seeing a few friendlies is always nice :)
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1413. msphar
5:12 PM GMT on June 22, 2008
Yes, and after several months in foreign waters it was sweet to see those boys.
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1412. pearlandaggie
5:07 PM GMT on June 22, 2008
1411. i'm guessing the USCG has jurisdiction because of the proximity to Puerto Rico?
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1411. msphar
5:03 PM GMT on June 22, 2008
Pearl, yes that was in the Mona just off the Hour Glass Shoal, which can be very ruough water at times, between Hispaniola and Puerto Rico.
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1410. Orcasystems
4:59 PM GMT on June 22, 2008
1403. msphar 4:48 PM GMT on June 22, 2008 Hide this comment.
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.



Here is a link to a good race tracking page :)
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1409. pearlandaggie
5:00 PM GMT on June 22, 2008
1408. very cool...i'm guessing that was the coast guard boarding your boat for inspection? cool pics!
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1408. msphar
4:51 PM GMT on June 22, 2008
Its a Caliber 40 LRC (Long Range Cruiser). Cutter rigged sloop

41 LOA
32 at the water line

Carries 230 gl diesel. 200 gl water.
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1407. Orcasystems
4:53 PM GMT on June 22, 2008
1403. msphar 4:48 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.
Action: | Ignore User


After 6 years of commercial fishing on a 32' gillnetter with a crew of three and then 22 years in the navy on ships 366' with a crew of 228. 44' and 8 sounds pretty comfy
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1406. pearlandaggie
4:53 PM GMT on June 22, 2008
LMAO, Floodman. poseur-hah!
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1405. Floodman
11:50 AM CDT on June 22, 2008
1349. STROMTOP

*POOF*...er, I mean *FLUSH*

Down the oubliette, poseur!
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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.
Member Since: September 14, 2007 Posts: 3 Comments: 3963

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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.