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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954. mermaidlaw
2:17 PM GMT on June 21, 2008
Thanks Vort. No one said that, I was just confussed as usual. LOL! I was trying to clear my own head. We have storms about to hit us here.

Have a nice Saturday.
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953. TheCaneWhisperer
2:12 PM GMT on June 21, 2008
Morning All.

Seems to be a pretty good concensus on an Epac storm next week
, all is quiet in the ATL. As discussed, it should heat up in the Atlantic Basin next couple weeks with the expected MJO pulse. Take in the quiet times now, we all know it's not going to be quiet for long.
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952. vortfix
2:14 PM GMT on June 21, 2008
So Vort nothing can come from the blob in the gom, except for some rain?

Who said that Mermaid??
See how things get twisted around? LOL

Nothing happening there right now Mermaid. LOL
Hope you're having a nice Saturday.
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951. mermaidlaw
2:06 PM GMT on June 21, 2008
Good morning Vort, and everyone.

So Vort nothing can come from the blob in the gom, except for some rain?
Member Since: July 23, 2006 Posts: 20 Comments: 8768
950. Patrap
9:10 AM CDT on June 21, 2008
JTWC on TC Fengshen

Imagery Link

TC Warning Graphic Link

Discussion Link

Member Since: July 3, 2005 Posts: 420 Comments: 127547
949. TerraNova
2:01 PM GMT on June 21, 2008
The Central Atlantic looks interesting as the GFS and CMC develop a low along the area of disturbed weather preceeding a tropical wave located just west of 30 West. Convection is being prometed by strong upper level divergence aiding the development of convective clusters.. Shear is currently not especially favorable for development but the GFS Shear Forecast shows wind shear decreasing along and to the west of the wave. Steering currents would take any low that develops along the wave axis into Trinidad/South America similar and so any development would face a problem with land interaction similar to what happened to 91L.

The blob of convection to the west of the Yucatan in the Gulf looks like it attempted to develop an LLC last night but has since either given up on it or relocated it. Shear will remain unfavorable in the GOM or at least in the vicinity of the Yucatan for development through the 25th. No surface stations are reporting anything that even remotely looks like a circulation as of 06z today so it seems like any LLC that it may have had last night is now gone and no new one is developing at the moment.

An upward MJO pulse will occur later this month into next month.
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948. vortfix
2:04 PM GMT on June 21, 2008
And my apologies....Good morning JP and all!
I hope everyone is having a great cup of coffee or two.
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947. hurricanehanna
2:04 PM GMT on June 21, 2008
Anyone up who can tell me about Fengshen? My hubby is in Manila and I'm having trouble reaching him. I thought it would turn east but looks like it has decided to cut across the island. THanks!
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946. vortfix
1:54 PM GMT on June 21, 2008
There's just a mid-upper trough running through the BOC/Yucatan areas.
Divergence is causing the convection flare.
Nothing happening there this morning.
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945. TampaSpin
9:53 AM EDT on June 21, 2008
944. txalwaysprepared 9:53 AM EDT on June 21, 2008

lol
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944. txalwaysprepared
1:50 PM GMT on June 21, 2008
I was just looking at all the GOM stuff. I wish that rain would head this way :( We need it!

Tampa.. he is actually my sweet little angel. My oldest and middle sons could be classified as the demon on most days ;)
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942. sonofagunn
1:45 PM GMT on June 21, 2008
Flare up over the potential spin indicated by QuikScat:

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941. TampaSpin
9:42 AM EDT on June 21, 2008
Could this be the beginning.....
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940. Stormchaser2007
1:41 PM GMT on June 21, 2008
93EINVEST.15kts-NAmb-130N-1160W
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939. TampaSpin
9:41 AM EDT on June 21, 2008
937. txalwaysprepared 9:38 AM EDT on June 21, 2008
tampa lol it's ok. A lot of people thought it was some storm when I posted it last year ;) I think I need to change it...


He looks like a demon.......lol...maybe he is...LMAO
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938. TampaSpin
9:36 AM EDT on June 21, 2008
If the heavy storms continue today off the Yucatan, a LLC will develop with low shear currently. Notice too that shear has been decreasing in the Carribean also.

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937. txalwaysprepared
1:36 PM GMT on June 21, 2008
tampa lol it's ok. A lot of people thought it was some storm when I posted it last year ;) I think I need to change it...
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936. IKE
8:35 AM CDT on June 21, 2008
The Caribbean wave looks headed for Central-America.......
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935. sonofagunn
1:29 PM GMT on June 21, 2008
Stuff near Yucatan...

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934. TampaSpin
9:27 AM EDT on June 21, 2008
931. txalwaysprepared 9:22 AM EDT on June 21, 2008
tampa - lol see ETA on 924. ;)


Oooopppppssssss......sorry.....LMAO
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933. all4hurricanes
1:24 PM GMT on June 21, 2008
if invest 93 becomes a TS what would it be called
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932. IKE
8:22 AM CDT on June 21, 2008
929. weathermanwatson 8:21 AM CDT on June 21, 2008
Bring on the GoM convection to the southeast!!!


Problem is...next week high pressure takes over...hot and dry again........
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931. txalwaysprepared
1:21 PM GMT on June 21, 2008
tampa - lol see ETA on 924. ;)
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930. Patrap
8:20 AM CDT on June 21, 2008

A hurricane's "hot towers" can increase its intensity by adding power to boost the storm's heat engine. For the first time, research meteorologists have run complex simulations of these phenomena using a very fine temporal resolution. They have combined this new simulation data with satellite observations to study the innerworking of the "hot towers" in never-before-seen detail.

Member Since: July 3, 2005 Posts: 420 Comments: 127547
929. weathermanwatson
1:19 PM GMT on June 21, 2008
Bring on the GoM convection to the southeast!!!
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928. IKE
8:21 AM CDT on June 21, 2008
Quiet time in the Atlantic.......too quiet...
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927. TampaSpin
9:19 AM EDT on June 21, 2008
Are we having another Blog hole again......gee
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926. TampaSpin
9:10 AM EDT on June 21, 2008
924. txalwaysprepared 9:08 AM EDT on June 21, 2008

yep it is good....by the way your aviator scares the hell out of me.....lol....
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925. msuwxman
8:09 AM CDT on June 21, 2008
So, we got a new invest out there huh?
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924. txalwaysprepared
1:03 PM GMT on June 21, 2008
tampa I was just coming to check in. That's good news though ;)

ETA - I just saw your question from last night. It's a 3D ultrasound pic of my youngest son (taken last summer). He's now 8 months old LOL
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923. sonofagunn
1:01 PM GMT on June 21, 2008
Dangit, I am supposed to go fishing this afternoon near the Sunshine Skyway. I hope the storms get weaker. I'll fish through rain, but not lightning.
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922. TampaSpin
8:53 AM EDT on June 21, 2008
Guess i messed up last nite....thats my fault for not confirming a morning view, but last nite just before the blog went down i made the comment that it appeared a LLC was developing in the BOC....looks like i was wrong...sorry everyone....never a good idea in the nite to do so without seeing a good visible first....my fault..
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921. Weather456
8:51 AM AST on June 21, 2008
Good Morning All


909. 305st0rm

The turning is observed in the lowe mid-levels rather than the surface.

=============================================
A rather vigorous perturbation within the ITCZ

===============================================
If organization improves then we could have TD 02E

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920. IKE
7:54 AM CDT on June 21, 2008
It's there now....

Tampa Radar
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919. IKE
7:51 AM CDT on June 21, 2008
918. TampaSpin 7:51 AM CDT on June 21, 2008
The sun is out and i have heard thunder all morning, so the heating of the day should be some big time thunder boomers inland i would suspect will occur in the afternoon.


That moisture in the southern GOM is headed your way.
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918. TampaSpin
8:49 AM EDT on June 21, 2008
The sun is out and i have heard thunder all morning, so the heating of the day should be some big time thunder boomers inland i would suspect will occur in the afternoon.
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917. IKE
7:48 AM CDT on June 21, 2008
Good luck surfmom......LOL. No storms in the GOM on the horizon.....maybe July....
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916. TampaSpin
8:47 AM EDT on June 21, 2008
Looks like florida should get some big time rain heading our way..........whooopiiii
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915. surfmom
12:48 PM GMT on June 21, 2008
OK running shoes on - out to hit the street b/4 it gets too hot later all
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914. surfmom
12:46 PM GMT on June 21, 2008
Thanks blueranch you reminded me of one thing I haven't done yet which was to get the boss to fix and check the fence ... geeze...good thing you mentioned that.
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913. surfmom
12:38 PM GMT on June 21, 2008
lol YOU ARE PROBABLY RIGHT ike! first thought this AM, my mother & my mate glaring,snarling, posturing or a hurricane. I'll take that hurricane --although you all know -- now I WILL get what I wished for. It would be hell either way - least with the 'cane I'd get waves.

Which reminds me that the last time Sarasota/Tampa got a 'cane there was a terrible housing/real estate crash happening. Just like the present situation here in SWFL. If things happen in cycles one wonders if this would be the year..mind you this IS the last thing I'd ever want to see happen to our community....but I am watching this year with EYES WIDE OPEN.
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912. nrtiwlnvragn
8:34 AM EDT on June 21, 2008
909. 305st0rm

QuikSCAT from this morning does not show any surface rotation.
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911. IKE
7:32 AM CDT on June 21, 2008

908. surfmom 7:29 AM CDT on June 21, 2008
geeze, I guess i had a lot to say this morning - zooming on the coffee. OK folks off for a good run before it rains --not that it matters, rain-running in SWFL is delightful!

INTERNATIONAL SURF DAY TODAY


Must be your nerves worried about your mom and your other half.
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910. blueranch1
12:31 PM GMT on June 21, 2008
Best bet with horses is to find pasture with as little trees around as possible and make sure all fences are secure. We have thought about hurricane proofing our barn, but if they get freaked out they will buck and kick in a stall and hurt themselves. breaking a leg or whatever. They are fight or flight animals. At least in a pasture they can run out fear and energy.
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909. 305st0rm
12:28 PM GMT on June 21, 2008
Im seeing some kinda rotation in the carribean approaching 75W along 15N
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908. surfmom
12:27 PM GMT on June 21, 2008
geeze, I guess i had a lot to say this morning - zooming on the coffee. OK folks off for a good run before it rains --not that it matters, rain-running in SWFL is delightful!

INTERNATIONAL SURF DAY TODAY
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907. surfmom
12:24 PM GMT on June 21, 2008
There is always much debate as to wether it is safer for horses to ride out the storm in a barn or the fields. Alot depends on the structure. But if you have an old wood barn - best bet is to set them out in the pasture. Horses can get more injured in the structure then if they are out ---of course there is no guarantee
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906. surfmom
12:20 PM GMT on June 21, 2008
Remember to help your geriatric members by doing the same. My mother-in-law is in assisted living, but is allowed her dog. I do not expect the facility to prepare for the dog. Have carrier and an appropriate stash of food available prior to any situation. They will move the elderly, and you may be too busy at your own home, to get to your relative. The dog is properly ID, vaccine information is taped to the kennel. No guarantee's but more of a chance not to be separated. The vaccine papers are crucial for ALL animals - have it ready - you can get far more insistent when you have those documents
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905. surfmom
12:14 PM GMT on June 21, 2008
although I live in suburbia, my son re-configured his old wood treehouse/swing/climber into a chicken coop (NO roosters) So we have chickens. He design the coop to have the nest area on the upper enclosed floor - to avoid any flooding. But - since I can't have chickens running about the house - he saved $ and brought a very, very large dog kennel that has a hand and holds his 6 chickens. If I have to hang that from a hook in the lanai or stash the birds, we have that covered, as well as ID bands around their ankles. Even the gerbil has a hurricane prep plan
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904. surfmom
12:04 PM GMT on June 21, 2008
Good morning Storm! Always have properly sized crates & enough food & water, as well as appropriate ID & vaccine information. When you set up your hurricane food stash remember to do so for your pets. ID does help pets get back to their owners IF separated.

If you are an owner of horses,cattle,goats, Llamas etc. Prior to the event of a 'cane have your plans ready. STay or Go - and the where you are going. If you stay be sure your animals are properly ID. A duck tape info tag braided into a horses tail and mane, and the cattle crayon - write the contact phone number on both sides of the animal (in cause it's laying down on one side)Have your large animal medical supplies already on hand - you will not be able to count on the vets in the initial stages.
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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.