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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854. Tazmanian
8:27 PM PDT on June 20, 2008
i think we could see 2 to 4 name storms in july
Member Since: May 21, 2006 Posts: 5093 Comments: 115952
853. moonlightcowboy
10:26 PM CDT on June 20, 2008
This blog will move like a movie with all the posts!
Member Since: July 9, 2006 Posts: 184 Comments: 29610
852. pottery
11:24 PM AST on June 20, 2008
LOL Taz. DO DO up to the chin............
Member Since: October 24, 2005 Posts: 0 Comments: 25533
851. TampaSpin
3:26 AM GMT on June 21, 2008
MLC whats your take in the GOM?
Member Since: September 2, 2007 Posts: 179 Comments: 20450
850. Patrap
3:26 AM GMT on June 21, 2008
As we lean toward July..the Atlantic will awaken with a BANG soon nuff.

Have a Plan,..have a Destination if in a Evact Zone.
Member Since: July 3, 2005 Posts: 433 Comments: 132815
849. Tazmanian
3:25 AM GMT on June 21, 2008
hi moon yup vary soon
Member Since: May 21, 2006 Posts: 5093 Comments: 115952
848. TampaSpin
3:25 AM GMT on June 21, 2008
843. jabjb2 11:21 PM EDT on June 20, 2008
Tampado you think the blob in the GOM will form into anything?


Don't know ......no models are showing any development.....but, sometimes what you see is more important....the environment is good, it just needs some persistent storm activity. The next 24-36 hours we will know....IMO.
Member Since: September 2, 2007 Posts: 179 Comments: 20450
847. Tazmanian
3:24 AM GMT on June 21, 2008
TampaSpin sooner or later if the wind shear dos not go up i think some where a long the gulf coast could be in for a cat 4 or stronger storm whats hop wind shear starts to go up soon here or we could be in big DO DO
Member Since: May 21, 2006 Posts: 5093 Comments: 115952
846. moonlightcowboy
3:23 AM GMT on June 21, 2008
Hey, TAZ! Things will start popping soon!
Member Since: July 9, 2006 Posts: 184 Comments: 29610
845. pottery
3:23 AM GMT on June 21, 2008
OOOOPS, I forgot to add STORMTOP and all his alter-egos, LOL
Member Since: October 24, 2005 Posts: 0 Comments: 25533
844. moonlightcowboy
3:22 AM GMT on June 21, 2008
838. Hey, Pat! Yep, you know those crews are sitting on "go!" Amazing!
Member Since: July 9, 2006 Posts: 184 Comments: 29610
843. jabjb2
3:21 AM GMT on June 21, 2008
Tampado you think the blob in the GOM will form into anything?
Member Since: June 9, 2008 Posts: 0 Comments: 39
842. Tazmanian
3:21 AM GMT on June 21, 2008
Fengshen is looking vary good for some in being under 20 to 30kt of wind shear woud't you say so???

Link
Member Since: May 21, 2006 Posts: 5093 Comments: 115952
841. txalwaysprepared
3:20 AM GMT on June 21, 2008
LMAO Tampa, you are just trying to get me to stay on here all night and watch the potential gom blob!! ;)
Member Since: August 18, 2007 Posts: 0 Comments: 1642
840. moonlightcowboy
3:19 AM GMT on June 21, 2008
836. I don't follow the wPacific much. Hades is one of the pros around here on that real estate.

837. Agreed, Pottery! Good folks here on WU!
Member Since: July 9, 2006 Posts: 184 Comments: 29610
839. TampaSpin
3:18 AM GMT on June 21, 2008
VERY low shear in the GOM also currently.
Member Since: September 2, 2007 Posts: 179 Comments: 20450
838. Patrap
3:17 AM GMT on June 21, 2008
The NOAA G-4 High Flyer and the NOAA P-3 Orion

Standing by to serve at a Moments notice.

Member Since: July 3, 2005 Posts: 433 Comments: 132815
837. pottery
3:15 AM GMT on June 21, 2008
MLC, Flood, Skye, Pat, Storm (X2), Drak, 23,77, 456, and everyone else.
'nuff respect.
Thanks for all you guys and Ladies do also. It is a great Community here, and I feel quite Honoured to be here.
Member Since: October 24, 2005 Posts: 0 Comments: 25533
836. txalwaysprepared
3:15 AM GMT on June 21, 2008
mlc LOL ! Since I had kids I became such a worry wart when it comes to storms coming. Now with three little ones I am sure to be totally neurotic this season!!!

Do storms ever make it to Singapore? Or too close to the equator?
Member Since: August 18, 2007 Posts: 0 Comments: 1642
835. Tazmanian
3:14 AM GMT on June 21, 2008
TampaSpin would you have to no why wind shear in the gulf been 5 to 10kt has of late???

Member Since: May 21, 2006 Posts: 5093 Comments: 115952
834. TampaSpin
3:13 AM GMT on June 21, 2008
828. txalwaysprepared 11:09 PM EDT on June 20, 2008
TampaSpin... you may not like it, but you may become my best "Friend" on here in the next few days. I apologize for all questions in advance!!!


Im no professsional and know just enough to get me in trouble.....but if i can assist you, others and myself will always aid.
Member Since: September 2, 2007 Posts: 179 Comments: 20450
833. Stormchaser2007
3:12 AM GMT on June 21, 2008
Doubt its gonna turn north.....
MIMIC-IR

Member Since: June 9, 2007 Posts: 4 Comments: 15971
832. moonlightcowboy
3:12 AM GMT on June 21, 2008
Have a good sleep, Flood!

TXalways, you better watch that TS fella - trouble! ;P
Member Since: July 9, 2006 Posts: 184 Comments: 29610
831. TampaSpin
3:11 AM GMT on June 21, 2008
GOM Loop.....play this....Link
Member Since: September 2, 2007 Posts: 179 Comments: 20450
830. TexasGurl
3:11 AM GMT on June 21, 2008
Here is a better link animated:

Link
829. moonlightcowboy
3:11 AM GMT on June 21, 2008
824. Yep, Sheri. Aside from gas, I'm noticing about a 15 percent increase in the cost of many things. I'm checking things just to get a good feel and to save money, too! Things are going up! 15 percent seems to be the average so far.(Except for gas - higher!)

Well, hope you get some good rest. NITE!
Member Since: July 9, 2006 Posts: 184 Comments: 29610
828. txalwaysprepared
3:09 AM GMT on June 21, 2008
TampaSpin... you may not like it, but you may become my best "Friend" on here in the next few days. I apologize for all questions in advance!!!
Member Since: August 18, 2007 Posts: 0 Comments: 1642
827. pottery
3:08 AM GMT on June 21, 2008
LOL, dont ask Flood to take no test right now Sheri. He's, uh, er, indisposed for a while.
Member Since: October 24, 2005 Posts: 0 Comments: 25533
826. Floodman
3:08 AM GMT on June 21, 2008
820. catastropheadjuster

Just an MRI, but I'm a wuss and have some clasutrophobia issues...well, folks, I;m out; just wanted to check in on Fengshen and see what the GOM issue was doing...

Thanks for all your kind wishes, and I'll be on off and on over the weekend
Member Since: August 2, 2006 Posts: 10 Comments: 9922
825. moonlightcowboy
3:08 AM GMT on June 21, 2008
821. It's cool, Pottery! Nice to see ya! And, sounds like you've got a good group of judges, too!

822. Yep, Flood, bunch of good folks down in paradise! (sapsuckers)! lol, j/k! (envious), ah!
Member Since: July 9, 2006 Posts: 184 Comments: 29610
824. catastropheadjuster
3:06 AM GMT on June 21, 2008
MLC I will sleep once these unisoms kick in. I took 4 of them. My tolerance level is so high. Can't afford Ambiem to expensive.
Sheri
Member Since: August 24, 2006 Posts: 21 Comments: 3683
823. Stormchaser2007
3:06 AM GMT on June 21, 2008
Another increase in wind speed...now at 100-115knots(according to current ADT estimates)

Member Since: June 9, 2007 Posts: 4 Comments: 15971
822. Floodman
3:05 AM GMT on June 21, 2008
Thanks, MLC...and I agree with you: we are lucky to have the Islanders contributiong to the blog; pottery, kman, bongo (though I don't know, how much ganja before the observations become suspect...LOL) and all the ones I've missed provide some very good first person observations for us
Member Since: August 2, 2006 Posts: 10 Comments: 9922
821. pottery
3:05 AM GMT on June 21, 2008
Hey MLC where you been ?
I got the avatar, chosen by unanimous consensus, and approved in triplicate, by the Sitting Committee of Daughters and Wives and suchlike and stuff.
From a large collection of obscure images and other irrelevant bits and peices that currently bung up my computer. LOL
How are you doing?
Member Since: October 24, 2005 Posts: 0 Comments: 25533
820. catastropheadjuster
3:05 AM GMT on June 21, 2008
Floodman you have to have some test taken or something? I hope your alright.
Sheri
Member Since: August 24, 2006 Posts: 21 Comments: 3683
819. TampaSpin
3:04 AM GMT on June 21, 2008
Steering flow would suggest a Northerly track...IMO.
Member Since: September 2, 2007 Posts: 179 Comments: 20450
818. moonlightcowboy
3:03 AM GMT on June 21, 2008
Hey, Sheri! Lawd, bisquits and tomato gravy .....shoot, now that's food! Enjoy, have a good sleep!
Member Since: July 9, 2006 Posts: 184 Comments: 29610
817. moonlightcowboy
3:02 AM GMT on June 21, 2008
812. Agreed, Flood! (Hope the pain eases, too, man!) In addition to Pottery's gracious demeanor, he's also "critical mass" on the lookout point down in Trinidad! I, at least, count on him to get a scoop on what's coming through! So, he's a key player for WU, too! Thanks, Pottery! :)
Member Since: July 9, 2006 Posts: 184 Comments: 29610
816. catastropheadjuster
3:00 AM GMT on June 21, 2008
Hey Floodman & MLC- How ya'll doing? Fine here. Gotta go to Miss in the morning to go pick tomatoes, gonna come home and start canning them. I love tomato gravy and homemade biscuits. Gotta get up around 4am.
Sheri
Member Since: August 24, 2006 Posts: 21 Comments: 3683
815. Tazmanian
3:00 AM GMT on June 21, 2008
TampaSpin you are right wind shear for that is olny 5 to 10kt


and it has this to go overe


Link


where do you think it may be going???
Member Since: May 21, 2006 Posts: 5093 Comments: 115952
814. TexasGurl
3:00 AM GMT on June 21, 2008
Link

This is like a TD on land????????
813. txalwaysprepared
2:59 AM GMT on June 21, 2008
Tampaspin... they are talking about a front moving through Texas and into the Gulf tomorrow. Will that have any effect on the GOM potential?
Member Since: August 18, 2007 Posts: 0 Comments: 1642
812. Floodman
2:57 AM GMT on June 21, 2008
806. pottery

I'm way ahead of you, my friend...I'm acheiving just the right amount of float as we speak...thanks, by the way, for your concern...you once again confirm my theory that the best people habituate this blog.
Member Since: August 2, 2006 Posts: 10 Comments: 9922
811. SpaceThrilla1207
2:57 AM GMT on June 21, 2008
Where are our Caribbean system and Gulf systems located? I know the Caribbean system is around 65W 15N (the dead zone). Where is the GOM blob circ. located? Expert help would be appreciated.

Also, I agree that the GOM system has a better chance to develop...the Caribbean has too much shear and little convection.
810. moonlightcowboy
2:56 AM GMT on June 21, 2008
Hey, ALL!

- yo, Pottery! Man, where'd you get that avatar?
Member Since: July 9, 2006 Posts: 184 Comments: 29610
809. txalwaysprepared
2:55 AM GMT on June 21, 2008
patrap and tampaspin... thanks for the heads up. I will be keeping an eye on that area. And I'll be looking for your input on it.

:)
Member Since: August 18, 2007 Posts: 0 Comments: 1642
808. TampaSpin
2:54 AM GMT on June 21, 2008
I think this is of more concerning than the Carribean system CURRENTLY.
Member Since: September 2, 2007 Posts: 179 Comments: 20450
807. HadesGodWyvern (Mod)
2:53 AM GMT on June 21, 2008
List of Fengshen landfalls that I can see from JMA track.

1.Eastern Samar/Samar
2.Bilaran
3.Masbate
Member Since: May 24, 2006 Posts: 56 Comments: 49932
806. pottery
2:53 AM GMT on June 21, 2008
Good to see you, Floodman.
Whatever meds work, take them man.
Member Since: October 24, 2005 Posts: 0 Comments: 25533
805. Patrap
2:53 AM GMT on June 21, 2008
Tropics are active in the W Pac and Heating up in the Atlantic.
Member Since: July 3, 2005 Posts: 433 Comments: 132815
804. Patrap
2:52 AM GMT on June 21, 2008
07W (Fengshen)

Multispectral Satellite Imagery Link
Member Since: July 3, 2005 Posts: 433 Comments: 132815

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Dr. Masters co-founded wunderground in 1995. He flew with the NOAA Hurricane Hunters from 1986-1990. Co-blogging with him: Bob Henson, @bhensonweather

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