Two 500-year floods in 15 years

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

Share this Blog
1
+

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

Reader Comments

Comments will take a few seconds to appear.

Post Your Comments

Please sign in to post comments.

or Join

Not only will you be able to leave comments on this blog, but you'll also have the ability to upload and share your photos in our Wunder Photos section.

Display: 0, 50, 100, 200 Sort: Newest First - Order Posted

Viewing: 554 - 504

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34Blog Index

554. grayingwindsurfer
3:15 PM GMT on June 20, 2008
One other comment on flooding & climate change:
Milly and others have shown annual runoff in large river basins in northern latitudes has been increasing and that climate models (in hindcast mode) do a good job of matching these increases. More importantly, if increasing greenhouse gas concentrations are left out of the models (again, in hindcast mode) the models do a poor job of matching the increased runoff. Although this alone is not definitive, it is yet another VERY STRONG argument that human-induced increases in greenhouse gases are changing the climate and causing increased likelihood of flooding, especially in northern latitudes.
Obviously any individual event can NOT be directly attributed to climate change, but the increased chances of it occurring (or re-occurring) CAN be, at least in part.
Member Since: Posts: Comments:
553. 69Viking
11:10 AM CDT on June 20, 2008
541. Nolehead

Speaking of Hurricane drinks, did you know they're putting a Pat O'Briens in Destin just over the Destin Bridge as part of the Harbor Walk? Hurricanes are some of my favorite mixed drinks!
Member Since: Posts: Comments:
552. kmanislander
4:19 PM GMT on June 20, 2008
This wave seems to be famous for arc clouds ( outflow boundary ). Here is a great image of one showing the arc cloud moving away from the convection to the North. The classic sign of collapsing thunderstorms.

Member Since: August 19, 2006 Posts: 0 Comments: 15798
551. cchsweatherman
12:18 PM EDT on June 20, 2008
456 - Thanks for the response last night. Could you take a look at my comments in my post regarding both tropical waves? Just wanted to get your take on the RAMSDIS surface observations.
Member Since: Posts: Comments:
550. guygee
4:18 PM GMT on June 20, 2008
492. grayingwindsurfer 3:15 PM GMT on June 20, 2008

1)There will NOT be an increase in 100 year floods, but there will LIKELY be an increase in the magnitude of the 100 year flood. This is semantics--The 100 year flood is merely the statistically predicted once-in-a-hundred-years flood (1% chance each year).

We could reword that to say that in terms of our former definition of the 100-year flood, there likely will be an increase in the frequency of these events.
Member Since: Posts: Comments:
549. kmanislander
4:16 PM GMT on June 20, 2008
The Caribbean wave will soon be in the vicinity of this buoy. So far surface pressures are relatively high

Link
Member Since: August 19, 2006 Posts: 0 Comments: 15798
548. Weather456
4:07 PM GMT on June 20, 2008
Nice break in the weather
Member Since: July 24, 2005 Posts: 407 Comments: 19076
547. surfmom
4:12 PM GMT on June 20, 2008
#545 Cheers to that !!!!! adios
Member Since: Posts: Comments:
546. surfmom
4:08 PM GMT on June 20, 2008
Off to work, come on guys/gals - some mental suggestion today - lets get that puff off the Yucatan spinning, it'll cool off the drought ridden SWFL and hopefully put off my moms visit LOL)

In the meantime, I am going to light some candles and bring treats to my statue of King Neptune
Member Since: Posts: Comments:
545. Nolehead
4:10 PM GMT on June 20, 2008
lol...just give us a 4' ground swell..that way both parties are happy!! that would be fair.
Member Since: Posts: Comments:
544. 69Viking
11:05 AM CDT on June 20, 2008
537. Nolehead

LOL! That Lake of Mexico is what helps make fishing out there so nice! Too funny how the surfers wish for waves and the fishermen wish for flat as a lake on a calm day!
Member Since: Posts: Comments:
543. surfmom
4:05 PM GMT on June 20, 2008
Well the Gulf is flat enough to make all the fishermen happy here --guess they need their turn Nole.......hopefully ours will come soon
Member Since: Posts: Comments:
542. nrtiwlnvragn
12:07 PM EDT on June 20, 2008
Member Since: Posts: Comments:
541. Nolehead
4:05 PM GMT on June 20, 2008
liquor and storms go hand in hand...lol..just love a good Hurricane (drink)
Member Since: Posts: Comments:
540. surfmom
4:00 PM GMT on June 20, 2008
As for Gulf coast surfers - this is not our week. The gradient did not get strong & will stay weak. So not enough omph to create strong west winds - thus NO surf this Sunday. Barely any wind. Flat on the gulf coast and more or less the same for the other side.

Looking at the area off of the Yuc, to maybe get strong enough to push some swell my way. till then it's paddling the buoys till something makes some action.
Member Since: Posts: Comments:
539. 69Viking
11:01 AM CDT on June 20, 2008
527. surfmom

LMAO! That is the same wish I would make if my Mom wanted to visit during the summer months! Her and my wife don't get along at all! If anything hopefully the activity down by the Yucatan will push rain north into all parts of Florida even if I have to sacrifice boating this weekend.
Member Since: Posts: Comments:
538. RasBongo
4:00 PM GMT on June 20, 2008
532. Drakoen

True. Apologies
Member Since: Posts: Comments:
537. Nolehead
4:02 PM GMT on June 20, 2008
surfmom...yeah i could use a nice swell...dang lake of mexico out there...
Member Since: Posts: Comments:
536. Drakoen
4:02 PM GMT on June 20, 2008
SOI back in the positive range. It was starting to look like 2006 in May but this upward peek is a good sign that El Nino conditions are still not coming to fruition.
Member Since: Posts: Comments:
533. weatherboyfsu
3:58 PM GMT on June 20, 2008
Good Morning,

Is everyone getting ready for Hurricane season?

Also, I have new thunderstorm pics on here.....check them out.....I will get better ones as the year goes on....
Member Since: Posts: Comments:
532. Drakoen
3:58 PM GMT on June 20, 2008
RasBongo, those streamline images are not current.
Member Since: Posts: Comments:
531. melwerle
3:56 PM GMT on June 20, 2008
Surfmom - you are HILARIOUS. I would wish for it too if that were the case. Try feeding both of them some shots of tequila before they enter the same room. I give my mom a cocktail about an hour b/4 hubby gets home and it makes her a bit mellow...

Member Since: Posts: Comments:
530. guygee
3:35 PM GMT on June 20, 2008
479. FLWeatherFreak91 3:07 PM GMT on June 20, 2008 I have a technical question for you guys... I just got a Wx watch for my bday yesterday and it has an altimeter that is giving me the MOST trouble.[...]

WeatherFreak - What make and model?


Member Since: Posts: Comments:
529. RasBongo
3:35 PM GMT on June 20, 2008
Extract from this 8.00 am trop. discussion (NHC)


A TROPICAL WAVE IS ALONG 23W S OF 12N MOVING W 10-15 KT. THE WAVE SHOWS UP VERY WELL ON THE TPW PRODUCT AND THE HOVMOLLER DIAGRAM THAT CLEARLY INDICATES THE WWD PROPAGATION OF THE WAVE. LOW LEVEL SATELLITE DERIVED WINDS ALSO SUPPORTS THE POSITION OF THE WAVE AXIS WHICH EXHIBITS SOME CYCLONIC TURNING NEAR 7N.

AN UPPER LEVEL TROUGH EXTENDS OVER THE E-CENTRAL ATLC WITH THE BASE REACHING THE FAR SE CARIBBEAN AND THE WINDWARD ISLANDS. AN UPPER-LEVEL RIDGE DOMINATES MOST OF THE TROPICS AND IS ENHANCING CONVECTION ALONG THE ITCZ AXIS TODAY.
HIGH PRES IS IN CONTROL OF THE FORECAST AREA EXTENDING A RIDGE WWD TO THE BAHAMAS AND CUBA. THIS SYSTEM IS FORECAST BY THE COMPUTER MODELS TO STRENGTHEN THROUGH MON PRODUCING A BELT OF
MODERATE TO FRESH ELY WINDS ACROSS THE TROPICAL ATLC FROM THE AFRICAN COAST TO THE CENTRAL CARIBBEAN.

If one looks at the streamlines:
Link

Link

one sees that the system will probably stay at low lattitude until it reaches the E.Carib. islands. Low latt. systems usually do a lot of damages (Ivan, Dean, etc).

Definitively to monitor.
Member Since: Posts: Comments:
527. surfmom
3:45 PM GMT on June 20, 2008
Dropping in for a quick minute. Well, I never wish for hurricanes, but it would make my day if the activity over the Yuc, turns into a nice enough hurricane to scare my mom from coming to FL to visit. My hubby and her fight like dogs and I'd rather face a 'cane then the 2 weeks of dogfights. So for my fist time ever, I am wishcasting for a effective but not destructive 'cane to enter the gulf.
Member Since: Posts: Comments:
526. Drakoen
3:49 PM GMT on June 20, 2008
Interesting wave to the SSW of the Cape Verde islands. Satellite imagery shows some mid-level cyclonic turning along the wave axis which is further supported by the CIMSS 700mb vorticity. CIMSS SAL mid to upper level water vapor imagery reveal mid-upper level subsidence ahead of the wave. The wave is under 10-20 knots of wind shear and is expected to remain at this level or gradually increase as the system continues westward.
Member Since: Posts: Comments:
525. weathermanwatson
3:50 PM GMT on June 20, 2008
Lets see if we have another invest soon!
Member Since: Posts: Comments:
524. cchsweatherman
11:40 AM EDT on June 20, 2008
Good morning all! Just like I had stated last night, I have never given up on this tropical wave now breezing through the Lesser Antilles. If you watch the RAMSDIS loop and pay attention to the observations, you can see that there is a surface circulation associated with the tropical wave. Convection continues to fire with the wave and wind shear has been decreasing ahead of the wave. It looks much better than the past 48 hours.



Our latest Eastern Atlantic tropical wave looks far more impressive than the previous one and has quite a vigorous lower mid-level circulation. It has much more moisture and much less dry air to deal with than its predecessor, but it will have to overcome the hostile wind shear ahead just like the Eastern Caribbean wave has done.

Member Since: Posts: Comments:
523. TampaSpin
11:46 AM EDT on June 20, 2008
Im out....gotta go make some of the green stuff......lol
Member Since: September 2, 2007 Posts: 178 Comments: 20439
522. weathermanwatson
3:45 PM GMT on June 20, 2008
Interesting to watch!
Member Since: Posts: Comments:
521. TampaSpin
11:45 AM EDT on June 20, 2008
Imaiage updated....by 15 minutes
Member Since: September 2, 2007 Posts: 178 Comments: 20439
520. Nolehead
3:43 PM GMT on June 20, 2008
tampa, i've been watching it myself and twc wanna b's keep saying the shear is too strong and it's nothing.....let's just wait and see...
Member Since: Posts: Comments:
519. TampaSpin
11:40 AM EDT on June 20, 2008
Either way it should make for some moisture for Florida.....horray.
Member Since: September 2, 2007 Posts: 178 Comments: 20439
518. TampaSpin
11:34 AM EDT on June 20, 2008
When you put this in motion zoom in you can see a spin starting may not mean anything ......but it is there..have to see if storms start poping.
Member Since: September 2, 2007 Posts: 178 Comments: 20439
517. weathermanwatson
3:38 PM GMT on June 20, 2008
Maybe the tropics will fire up once again.
Member Since: Posts: Comments:
516. NoNamePub
3:35 PM GMT on June 20, 2008
Hey Kids - Yuc Low loks intersting....
How is our waveholding together!?
Member Since: Posts: Comments:
515. Patrap
10:32 AM CDT on June 20, 2008
GOM IR Loop Link
Member Since: Posts: Comments:
514. TampaSpin
11:28 AM EDT on June 20, 2008
Gang...thank you everyone for the help...I really looked hard at the tip of the Yucatan i it sure looks like a low of some type is trying to develop.....i would pay very close attention to that area today......JMO.
Member Since: September 2, 2007 Posts: 178 Comments: 20439
512. Patrap
10:27 AM CDT on June 20, 2008
Its been that way since it was developed.

I explained it fully below.

474.To change your avatar,just click on the Avatar here,and use the "Modify This Image" button down the page,upload new pic and check the "Primary Portrait for Bio" box.
Easy


Member Since: Posts: Comments:
511. Floodman
10:25 AM CDT on June 20, 2008
Hiya, mel!

IKE, one more, as it fits in with "Good Mornin' Judge" so well:



Rubber Bullets

Okay, now back to the tropics
Member Since: Posts: Comments:
510. TampaSpin
11:24 AM EDT on June 20, 2008
505. melwerle 11:23 AM EDT on June 20, 2008

I had trid that before but the bio button was not there before i don't think....i think an update occured over the last few days to fix the problem....but it worked....Thanks SKYEpony
Member Since: September 2, 2007 Posts: 178 Comments: 20439
509. Skyepony (Mod)
3:24 PM GMT on June 20, 2008
There you go TampaSpin..

I'll catch ya'll later.
Member Since: Posts: Comments:
508. Floodman
10:23 AM CDT on June 20, 2008
500. jphurricane2006

You're right, jp...and thanks, by the way...I take your comment 485 as high praise
Member Since: Posts: Comments:
507. TampaSpin
11:23 AM EDT on June 20, 2008
504. 69Viking 11:23 AM EDT on June 20, 2008
499. TampaSpin

So your sprinkler system is hooked up to city water and not tapped into a well? If you're tapped into a well they can't say anything because you're just recycling ground water.


I do you city water........but my understanding is it does not matter...they are fining everyone.....
Member Since: September 2, 2007 Posts: 178 Comments: 20439
506. IKE
10:23 AM CDT on June 20, 2008
10CC Binge...Wall Street Shuffle

Now...back to the tropics........
Member Since: Posts: Comments:
505. melwerle
3:22 PM GMT on June 20, 2008
Hey Tampa - that worked! Upload a new image and check it as your primary...voila
Member Since: Posts: Comments:
504. 69Viking
10:21 AM CDT on June 20, 2008
499. TampaSpin

So your sprinkler system is hooked up to city water and not tapped into a well? If you're tapped into a well they can't say anything because you're just recycling ground water.
Member Since: Posts: Comments:

Viewing: 554 - 504

Page: 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34Blog Index

Top of Page

About

Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.

Local Weather

Partly Cloudy
80 °F
Partly Cloudy