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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154. Stormchaser2007
7:35 PM GMT on June 19, 2008
Yeah gotta go pick some light bulbs up at the hard ware store....be back later.
Member Since: June 9, 2007 Posts: 4 Comments: 15950
153. atmoaggie
7:34 PM GMT on June 19, 2008
So thats why these people in the Philippines need to be ready.

Without a doubt. They will certainly still get winds, how much and the surge still in question, but possible.
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152. Floodman
2:33 PM CDT on June 19, 2008
I'm out...conference call...BBL
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151. atmoaggie
7:29 PM GMT on June 19, 2008
With the exception of a large contingent in New Orleans...if you're not part of that contingent I apologize, but of all the areas hit by you know who, they are the furthest behind in recovery

You should see the "recovery" going on to the north of NOLA. St Tammany parish did get the full effect of Katrina, but now...almost no sign it ever happened. The only lingering effect is that the insurance companies want to wait a while to start making premium money here again. I guess they want to get a few years closer to the next storm to start writing policies.

Can you believe that most ins companies will not write a policy for a home 15 miles inland from Lake Pontchartrain at 100 feet above sea level? The money they could make, but choose not to.
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150. Stormchaser2007
7:29 PM GMT on June 19, 2008
146. Your Welcome! I do believe theres a trough thats gonna give it a shove to the north...but these typhoons arent always picked up. So thats why these people in the Philippines need to be ready.
Member Since: June 9, 2007 Posts: 4 Comments: 15950
149. Floodman
2:27 PM CDT on June 19, 2008
143.
Yep...
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148. PensacolaNative
7:27 PM GMT on June 19, 2008
10/4 Myway... No harm.
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147. atmoaggie
7:28 PM GMT on June 19, 2008
Back to work for me.

Later guygee...I am out, too. Rat killin.
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146. atmoaggie
7:27 PM GMT on June 19, 2008
Thanks for the MIMIC loop chaser.

The end looks like a classic recurve...is there a trough there to pick it up to the N or something?
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145. guygee
7:14 PM GMT on June 19, 2008
Thanks atmoaggie, something for me to ponder.
Also some wise words from MLC. It should be known about Obama that his chief economic adviser is son of Milton Friedman aka neoliberal supreme Austan Goolsbee from the U. of Chicago.

Adaptation is the key to the future.

Back to work for me.
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144. Floodman
2:25 PM CDT on June 19, 2008
142. atmoaggie

With the exception of a large contingent in New Orleans...if you're not part of that contingent I apologize, but of all the areas hit by you know who, they are the furthest behind in recovery
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143. Stormchaser2007
7:24 PM GMT on June 19, 2008
139. Yeah that would be very unfortunate....If I recall correctly Manila got hit hard last year.
Member Since: June 9, 2007 Posts: 4 Comments: 15950
142. atmoaggie
7:22 PM GMT on June 19, 2008
Nole I just hate to be grouped with people who want handouts. I have been through at least 25 tropical systems in my lifetime here and have never asked or received any gov help. Oh and we were actually hit by the hurricanes.

You should have seen the same to the third power on the MS gulf coast after Katrina. People seem to actually care for their neighbours now. Sure some of them did get some gov help, but by and large, the entire coastline is of the DIY mindset.
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141. myway
7:19 PM GMT on June 19, 2008
Pensecola
The comment was not intended for you.
I migrated to Miami 25 years ago.
Lost house in Andrew (lived in Cutler ridge)
Moved to Palm Beach county and have been in Francis, Jeane and Wima.
No govt. help for me either. Thats what I par premiuims for and why I prepare.
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140. Stormchaser2007
7:24 PM GMT on June 19, 2008
138. Yep its about time!
Member Since: June 9, 2007 Posts: 4 Comments: 15950
139. Floodman
2:22 PM CDT on June 19, 2008
137. Stormchaser2007

Due west and then north could be bad...depending on timing that could dump it right on top of Manila
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138. Floodman
2:22 PM CDT on June 19, 2008
135. Stormchaser2007

That should just about take care of it...
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137. Stormchaser2007
7:21 PM GMT on June 19, 2008
Looks to moving due west...then at the end a slight northern component. IMO
Member Since: June 9, 2007 Posts: 4 Comments: 15950
136. Nolehead
7:16 PM GMT on June 19, 2008
yep, exactly!! Just a few times....
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135. Stormchaser2007
7:15 PM GMT on June 19, 2008
The EATL waves time is finally up...40-50knots of shear like Kman said should bring a quick demise.

Member Since: June 9, 2007 Posts: 4 Comments: 15950
134. pearlandaggie
7:13 PM GMT on June 19, 2008
now that was uncalled for, floodman! LOL
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132. PensacolaNative
7:11 PM GMT on June 19, 2008
Nole I just hate to be grouped with people who want handouts. I have been through at least 25 tropical systems in my lifetime here and have never asked or received any gov help. Oh and we were actually hit by the hurricanes.
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131. Floodman
2:14 PM CDT on June 19, 2008
127. atmoaggie

LMAO
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130. counters
7:14 PM GMT on June 19, 2008
atmoaggie, you're dead on - all of us should be worried about the over-hyping and emotional sensationalism being put on AGW. However, this isn't to say that the theory is in anyway affected because some bozos are politicizing it for their own ends.
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129. kmanislander
7:11 PM GMT on June 19, 2008
This image shows arc clouds as the leading edge of the wave to the east of the islands. This is indicative of collapsing thunderstorms.

40 to 50 knots of shear plus being a fast mover pretty much spells the end for this wave. At best it may bring a little rain to the islands.

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128. NEwxguy
7:12 PM GMT on June 19, 2008
112. Floodman 7:04 PM GMT on June 19, 2008
108. moonlightcowboy

Overall I tend to be very optimistic about things, but when I start to think about them intellect takes over, and we all know what a buzz-kill intellect can be

ROTFLMAO
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127. atmoaggie
7:13 PM GMT on June 19, 2008
121. atmoaggie

Suspicious and Bitter; hmm, aren't those course offerings at A&M? LOL

Just kidding, atmo aggie...


The football players take them as prerequisites to basket weaving. ;-)
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126. atmoaggie
7:10 PM GMT on June 19, 2008
Looks like Fengshen has a chance to miss Cape Hatteras...I mean Philippines and become only a fish storm.
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125. Stormchaser2007
7:09 PM GMT on June 19, 2008
Well it does have rather favorable OHC in and around it....Also in the latest satellite loops I am seeing a NW or W motion in its track...

Member Since: June 9, 2007 Posts: 4 Comments: 15950
124. Floodman
2:11 PM CDT on June 19, 2008
121. atmoaggie

Suspicious and Bitter; hmm, aren't those course offerings at A&M? LOL

Just kidding, atmo aggie...
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123. TEXASYANKEE43
7:06 PM GMT on June 19, 2008
113. HadesGodWyvern


Yes, agreed. The storm still has time to intencify too...
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122. Floodman
2:05 PM CDT on June 19, 2008
114. Stormchaser2007

Well, if it doesn't gain some latitude, it'
ll run through the central PI; some mountains but mostly water...what does the steering look like? It looks to have a bit of a "slightly W of N" look to it, so Luzon will certainly get some of it
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121. atmoaggie
7:06 PM GMT on June 19, 2008
Overall I tend to be very optimistic about things, but when I start to think about them intellect takes over, and we all know what a buzz-kill intellect can be...LOL

HA. LOL. That is how I turned so suspicious and bitter.
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120. HadesGodWyvern (Mod)
7:05 PM GMT on June 19, 2008


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119. weatherboyfsu
7:05 PM GMT on June 19, 2008
Good afternoon,

Looks to be a few nasty cells developing just to my north near ocala florida.....

Kind of dry here west of orlando but things seem to be getting more humid....
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118. atmoaggie
6:57 PM GMT on June 19, 2008
"I think it's extremely difficult to pin the last season on global warming. That does not preclude that there may be a global warming signal buried in there somewhere, but nobody in my field thinks that we've seen it."


Flood, pretty sure Kerry Emanuel said that (A lot more level-headed than anything Trenberth had to say about 2004 season). And my point with IPCC is NOT whether or not climate change is occurring, but the effects of it. Climate has always been changing (look at all of the lovely, but different, species we have) and always will be (look into the future at all of the lovely species that are a result of adaptation).

The fear-mongering is where I have a problem with IPCC. Some of the supposed results known so far are not so good, some simply are not bad at all, but good. IPCC has been giving us, with the mainstream media's assistance, the earth-is-going-to-be-some-horrible-wasteland-because-the-temp-went-up-a-little treatment. Seriously.
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117. TEXASYANKEE43
7:02 PM GMT on June 19, 2008
Hey flood, How bad was that storm this am in DFW? Cause its right about to me now!
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116. Nolehead
7:03 PM GMT on June 19, 2008
Pensacola, you got it..local boy right here myself..think we did a damn fine job concidering the circumstances.
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115. counters
7:04 PM GMT on June 19, 2008
Re #89:

Funding sources, such as NSF, NASA, NOAA, etc. still have to justify budgets with non-scientists...most representing the public (congress). Generating a public furor makes more money available to those generating the furor...in grants.

Not when the government authorizing those grants is hostile to the science, as is evidenced here, here, here, here, here, and... you get my point.
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114. Stormchaser2007
7:04 PM GMT on June 19, 2008
107. Thanks Flood!! I have a bad feeling bout this one....: (
Member Since: June 9, 2007 Posts: 4 Comments: 15950
113. HadesGodWyvern (Mod)
7:02 PM GMT on June 19, 2008
104. TEXASYANKEE43 7:00 PM GMT on June 19, 2008

ya.

Philippines, Taiwan, and the Japan southwestern Islands need to prepare.
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112. Floodman
2:03 PM CDT on June 19, 2008
108. moonlightcowboy

Overall I tend to be very optimistic about things, but when I start to think about them intellect takes over, and we all know what a buzz-kill intellect can be...LOL
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111. PensacolaNative
6:54 PM GMT on June 19, 2008
Myway
Pensacola and Mobile took care of themselves after Ivan and Dennis....In your reference to other parts of the country.....Our neighbors should have payed attention to how we handled the situation.
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110. TEXASYANKEE43
7:00 PM GMT on June 19, 2008
It could recurve befor it gets that far North tho...
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109. Nolehead
7:01 PM GMT on June 19, 2008
myway...AMEN!! that's so true..
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108. moonlightcowboy
2:01 PM CDT on June 19, 2008
99. Flood, you may just be right, my friend!
Member Since: July 9, 2006 Posts: 184 Comments: 29610
107. Floodman
1:56 PM CDT on June 19, 2008
Nice graphic, Stormchaser...Fengshen, huh? Be happy if you're not in the PI
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106. myway
6:57 PM GMT on June 19, 2008
Nole
I am a transplanted midwesterner. Live in Florida now. My point was for people to stop complaining and start doing something yourself. If you wait for outside intervention, your situation will get worse and WE will all pay for it in the end.
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105. NEwxguy
6:50 PM GMT on June 19, 2008
hmmmmm,man messing up his environment,I find that hard to believe,we've never done that in the past?
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104. TEXASYANKEE43
6:57 PM GMT on June 19, 2008
103. HadesGodWyvern


That does not look good for Japan with it moving West.....
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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.

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