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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804. Patrap
9:50 PM CDT on June 20, 2008
07W (Fengshen)

Multispectral Satellite Imagery Link
Member Since: July 3, 2005 Posts: 426 Comments: 128764
803. stormdude77
10:46 PM AST on June 20, 2008
The last thing China needs is a tropical cyclone affecting them...this is really a ''possible'' dangerous situation for them, if the forecast verifies
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802. Patrap
9:49 PM CDT on June 20, 2008
07W.FENGSHEN

Latest vis/geo/1km_zoom/20080621.0157 Link
Member Since: July 3, 2005 Posts: 426 Comments: 128764
801. TampaSpin
10:49 PM EDT on June 20, 2008
798. Patrap 10:47 PM EDT on June 20, 2008
GOM IR Loop Link


Patrap i think that area is of the most concern in the near future instead of the Carribean system.
Member Since: September 2, 2007 Posts: 178 Comments: 20443
800. Tazmanian
7:45 PM PDT on June 20, 2008
TROPICAL WEATHER DISCUSSION...COR
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
805 PM EDT FRI JUN 20 2008



THE CARIBBEAN SEA...
UPPER LEVEL ANTICYCLONIC FLOW COVERS THE
AREA WEST OF 75W WITH THE GUATEMALA/HONDURAS-TO-WESTERN CUBA
UPPER LEVEL RIDGE. STRONG SHOWERS AND THUNDERSTORMS ARE ALONG
THE COSTA RICA COAST ON THE WESTERN SIDE OF A MIDDLE LEVEL TROUGH
IN THE SOUTHWESTERN CORNER OF THE AREA. A MIDDLE TO UPPER LEVEL
TROUGH CONNECTS ONE CUT-OFF CYCLONIC CIRCULATION CENTER NEAR
21N56W IN THE ATLANTIC OCEAN TO A SECOND CUT-OFF CYCLONIC CENTER
NEAR 16N67W IN THE EASTERN CARIBBEAN SEA. A 64W/65W TROPICAL WAVE
SOUTH OF 20N IS MOVING THROUGH THE EASTERN CARIBBEAN SEA.
ISOLATED STRONG THUNDERSTORMS IN VENEZUELA FROM 7N TO 10N
BETWEEN 64W AND 68W. ISOLATED MODERATE SHOWERS FROM 10N TO 16N
BETWEEN 59W AND 66W...AND FROM 15N TO 16N BETWEEN 68W AND 71W.
Member Since: May 21, 2006 Posts: 5091 Comments: 115244
799. TampaSpin
10:45 PM EDT on June 20, 2008
Loop this link 20 back.....Link
Member Since: September 2, 2007 Posts: 178 Comments: 20443
798. Patrap
9:47 PM CDT on June 20, 2008
GOM IR Loop Link
Member Since: July 3, 2005 Posts: 426 Comments: 128764
797. txalwaysprepared
2:43 AM GMT on June 21, 2008
That's a great pic of Fengshen... but so sad to think what's going on underneath. I hope they were ready!
Member Since: August 18, 2007 Posts: 0 Comments: 1642
796. weatherblog
2:42 AM GMT on June 21, 2008
787. Tazmanian 2:37 AM GMT on June 21, 2008
what do you think this blog would be like if Fengshen was in the gulf of MX right now???


Katrina and Rita ring a bell...
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795. Tazmanian
7:42 PM PDT on June 20, 2008
any web cams overe there????
Member Since: May 21, 2006 Posts: 5091 Comments: 115244
794. Floodman
2:41 AM GMT on June 21, 2008
I'm back, by the way, from my wonderful experience with nuclear medicine; thank god for strong narcotics nd tranquilizers!
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793. stormdude77
10:40 PM AST on June 20, 2008
I think we'll see a marked increase in tropical activity, when the positive phrase of the MJO reaches the Atlantic (around the first week of July)...
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792. txalwaysprepared
2:40 AM GMT on June 21, 2008
TampaSpin - ok, yeah I know about the wave. But what about in the GOM? Shear is low yes?

NVM. Now I see your 788. post.

THanks :)
Member Since: August 18, 2007 Posts: 0 Comments: 1642
791. Weather456
10:39 PM AST on June 20, 2008
774. presslord 10:23 PM AST on June 20, 2008
456. That oughta be Required reading


lol lol lol
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790. pottery
10:37 PM AST on June 20, 2008
Thats an incredible storm, in the Phillipines. Gusting to 125 k in the morning. Significant wave height to 18 feet. On small islands, thats awful man.
Member Since: October 24, 2005 Posts: 0 Comments: 24402
789. Floodman
2:38 AM GMT on June 21, 2008
781. cchsweatherman

Because while the area Fengshen is moving across currently has some moutainous areas, it's mostly water, and extremely warm water at that...
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788. TampaSpin
10:36 PM EDT on June 20, 2008
Did anyone see the loop right before sunset near the Yucatan.....sure looked like a LLC trying to develop.
Member Since: September 2, 2007 Posts: 178 Comments: 20443
787. Tazmanian
7:35 PM PDT on June 20, 2008
what do you think this blog would be like if Fengshen was in the gulf of MX right now???



wind shear in the gulf and the environment is all most perfect wind shear been 5 to 10kt for weeks now some time wind shear may get has high has 20kt but falls right back down
Member Since: May 21, 2006 Posts: 5091 Comments: 115244
786. pottery
10:36 PM AST on June 20, 2008
77, those Mile Trees must have been dancing in that wind !
Member Since: October 24, 2005 Posts: 0 Comments: 24402
785. HadesGodWyvern (Mod)
2:34 AM GMT on June 21, 2008
no idea when it made landfall over Eastern Samar it was just a 75-80 knots cyclone and it strenghthened when it reached between Masbate and Samar.

now its near 100 knots
Member Since: May 24, 2006 Posts: 51 Comments: 45650
784. Patrap
9:34 PM CDT on June 20, 2008
Typhoon 07W (Fengshen) Warning #11
Issued at 21/0300Z FORECAST TEAM: ALPHA//
NNNN
Prognostic Reasoning Link
TC Warning Graphic Link
Member Since: July 3, 2005 Posts: 426 Comments: 128764
783. stormdude77
10:30 PM AST on June 20, 2008
Yeah Pottery...very windy here this morning and into this afternoon, (people were actually a bit scared)...
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782. TampaSpin
10:32 PM EDT on June 20, 2008
cchs i hear ya, the environment must be perfect.
Member Since: September 2, 2007 Posts: 178 Comments: 20443
781. cchsweatherman
10:29 PM EDT on June 20, 2008
Question - How the hell did Fengshen strengthen rapidly and develop an impressive eye moving across the Phillipines? Just amazing (of course for us to watch), but tragic for the Phillipines as they're getting lashed by a rapidly strengthening typhoon. I hope they were prepared for a powerful typhoon.
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780. StormJunkie
2:29 AM GMT on June 21, 2008
Evening all :~)

Sorry press, looks official now...

Good to see ya
Member Since: August 17, 2005 Posts: 26 Comments: 16874
779. TampaSpin
10:27 PM EDT on June 20, 2008
776. txalwaysprepared 10:24 PM EDT on June 20, 2008

the pic is why
Member Since: September 2, 2007 Posts: 178 Comments: 20443
778. HadesGodWyvern (Mod)
2:19 AM GMT on June 21, 2008


looks like the eye may pass over Romblon and Occidental Mindoro/Oriental Mindoro

Member Since: May 24, 2006 Posts: 51 Comments: 45650
777. TampaSpin
10:25 PM EDT on June 20, 2008
Member Since: September 2, 2007 Posts: 178 Comments: 20443
776. txalwaysprepared
2:23 AM GMT on June 21, 2008
TampaSpin... why are those two interesting? I'm just signing in. Haven't had a chance to look at anything yet.
Member Since: August 18, 2007 Posts: 0 Comments: 1642
775. pottery
10:11 PM AST on June 20, 2008
Yeah, CCHS. Some heavy convection in small areas East of Tobago, heading across there tonight, and to Grenada by dawn.
The very steep hills in both Tobago and Grenada is not where you want to be in heavy rainfall events. I dont think there is enough in this to warrant any real concern though.
Member Since: October 24, 2005 Posts: 0 Comments: 24402
774. presslord
2:20 AM GMT on June 21, 2008
456. That oughta be Required reading
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773. TampaSpin
10:20 PM EDT on June 20, 2008
Looks like 2 areas of interest, The Carribean and the GOM.
Member Since: September 2, 2007 Posts: 178 Comments: 20443
772. TampaSpin
10:16 PM EDT on June 20, 2008
good evening everyone.
Member Since: September 2, 2007 Posts: 178 Comments: 20443
771. cchsweatherman
10:03 PM EDT on June 20, 2008


Using the latest satellite imagery for the tropical wave, there is may be a low-level circulation center at around 15N 65W. Convection has begun building once again in association with the wave, but I have noticed some more curvature to this convection just NW of this circulation center. It remains a fighter and just needs lower shear in order to develop.
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770. WeatherRhino
1:51 AM GMT on June 21, 2008
Just checking. It looks ugly. First day of Summer and I am just checking it to see whats going on.
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769. pottery
9:48 PM AST on June 20, 2008
Rhino, whatever it is, its going to run into some very dry air in the short term. But it could very well be the next interesting blob.
Member Since: October 24, 2005 Posts: 0 Comments: 24402
768. pottery
9:46 PM AST on June 20, 2008
A 95kph wind gust at G.Adams airport 77 ??
We had no wind here at all today. Just constant drizzle with some heavy stuff from time to time.
Member Since: October 24, 2005 Posts: 0 Comments: 24402
767. WeatherRhino
1:46 AM GMT on June 21, 2008
Whats that coming off the African Coast?
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766. pottery
9:35 PM AST on June 20, 2008
There was a guy from Mexico on here a week ago or a little more. Cant recall his handle. Whatever happened to him ??
He was being flooded out apparently.
Member Since: October 24, 2005 Posts: 0 Comments: 24402
765. stormdude77
9:37 PM AST on June 20, 2008
Pottery, LOL...
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764. HadesGodWyvern (Mod)
1:35 AM GMT on June 21, 2008
looks like the JTWC advisory for Typhoon 07W (Fengshen/Frank) will have the intensity at 95 knots with wind gusts up to 115-120 knots.
Member Since: May 24, 2006 Posts: 51 Comments: 45650
763. Stormchaser2007
1:35 AM GMT on June 21, 2008
07W FENGSHEN.95kts-952mb
Member Since: June 9, 2007 Posts: 4 Comments: 15921
762. pottery
9:30 PM AST on June 20, 2008
Hey Dude77. 37mm so far sounds good to me! I have had 20 here to 9:30, and hoping for a little more. Tanks are filling up nicely. I may even get to wear some clean clothes tomorrow after the Lady does some washing LOL
Member Since: October 24, 2005 Posts: 0 Comments: 24402
761. Patrap
8:31 PM CDT on June 20, 2008


Lets have the Studio Bring up the WV Loop if they would.

Christina,do we have that? Link

Member Since: July 3, 2005 Posts: 426 Comments: 128764
760. Stormchaser2007
1:32 AM GMT on June 21, 2008
From CIMSS....
Raw T#
7.1
Member Since: June 9, 2007 Posts: 4 Comments: 15921
759. Stormchaser2007
1:28 AM GMT on June 21, 2008
Latest T number drop would support near 110knot winds....which is somewhat believable.

Member Since: June 9, 2007 Posts: 4 Comments: 15921
758. cchsweatherman
9:20 PM EDT on June 20, 2008
756. ATS3 9:14 PM EDT on June 20, 2008
CCHS IS MISSING..............
Action: | Ignore User


Odd timing for that comment. I just logged back into the blogs. It seems like you're my No. 1 fan here if you're the only person ever to make a comment like that regarding my whereabouts.
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757. Weather456
9:14 PM AST on June 20, 2008
no problem
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756. ATS3
1:12 AM GMT on June 21, 2008
CCHS IS MISSING..............
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755. sflgatorgirl
1:07 AM GMT on June 21, 2008
I guess the others just don't know, or don't have kids....I got it. BTW, thanks for all of y'all for your knowledge...I have been checking this blog since 04' or 05' season....and this truely is real time info. Very helpful! :)
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754. HadesGodWyvern (Mod)
1:06 AM GMT on June 21, 2008
I believe this will make Fengshen at least 100 knots using the 1 min sustained winds and a Category 3 on the Safir-Simpson scale.
Member Since: May 24, 2006 Posts: 51 Comments: 45650

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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.