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: 1004 - 954

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

1004. spayandneuter
2:28 PM EDT on June 21, 2008
Glad to see some chatter here about evacuating with pets. Horses, cattle and other large animals are even more difficult. If you have horses and they are not used to being loaded into a trailer, start the lessons now! It will make your life easier. In the California fires we had so many horses that had never been trailered and we ended up having to lead them out for miles to a safe place.

Remember that a disaster can be anything, not just a hurricane, flood or tornado. Fires (house fire is #1), chemical spills and even terrorism should be concerns. What happens if there is a huge chemical spill that blocks the highway leading to your home? What would you do? tough questions that we all need to think about. You can organize your neighbors to help each other in the event you are not home. You can either join or create your own CERT (citizens emergency response team) in your area. Your state's Agriculture department or SART (state agriculture response team) can help you with this. Many times SERT's and SART's are the first responders on the scene and can mean life and death for your animals.

If someone can tell me how to do it, I will post a "one page family disaster plan" which is an excellent format to help you get organized with all your information and your animals' information as well.


Member Since: Posts: Comments:
1003. Skyepony (Mod)
6:37 PM GMT on June 21, 2008
By that latest pass looks like it's gonna stay well east of Manila, avoiding the land. Best scenario for them consider where it was.

Levi~ did that look donut before it hit that bigger island or what?

I gotta shut down. Here comes a severe thunderstorm.
Member Since: August 10, 2005 Posts: 170 Comments: 38093
1002. CybrTeddy
6:39 PM GMT on June 21, 2008
Good day everyone

The Caribbean wave has lost any circulation it had at the 850 and 700 mb level. It never did have a surface low and I see no evidence of one forming at this time. At best there is a wind shift typical of an open wave. Quikscat had winds around 20 to 25 knots South of Hispaniola this morning which is also typical for a wave.

The Atl wave is becoming interesting because an anti-cyclone is building overhead. This can be seen in the shear map as well as by the way in which the cloud field is fanning out in all quadrants. There is also a noticeable lack of any stripping away of the convection by high level winds.

If the high continues to build to the West in tandem with the track of the wave we could see some development in 24 to 36 hours IMO

Here is the AVN loop showing the expanding could deck.


So, what your saying it might develop. Because it has an Anticyclone protecting it from shear?
Member Since: Posts: Comments:
1001. cchsweatherman
2:39 PM EDT on June 21, 2008
...TROPICAL WAVES...
TROPICAL WAVE IS ALONG 33W/34W S OF 16N MOVING W 15-20 KT. BROAD
LOW-MID LEVEL CYCLONIC TURNING IS EVIDENT ON VISIBLE SATELLITE
IMAGERY. LATEST ASCAT WIND DATA SUPPORTS THE WAVE POSITION.
UPPER LEVEL FEATURES CONTINUE TO KEEP MOST OF THE CONVECTION SW
OF THE AXIS. A SMALL CLUSTER OF MODERATE CONVECTION IS FROM
1N-2N BETWEEN 34-35W. ADDITIONAL CLUSTERS OF SCATTERED MODERATE
TO STRONG CONVECTION ARE WITHIN 200 NM AHEAD OF THE AXIS FROM
4N-8N.

TROPICAL WAVE IS IN THE CENTRAL CARIBBEAN ALONG 73W FROM HAITI
TO COLOMBIA MOVING W NEAR 20 KT. SATELLITE IMAGERY SHOWS
LOW-LEVEL TURNING NEAR 15N.
SCATTERED SHOWERS AND THUNDERSTORMS
ARE EAST OF THE AXIS FROM 15N-18N BETWEEN 69W-73W. THIS
CONVECTIVE ACTIVITY IS BEING ENHANCED BY UPPER LEVEL DIVERGENCE.
Member Since: Posts: Comments:
1000. kmanislander
6:17 PM GMT on June 21, 2008
Good day everyone

The Caribbean wave has lost any circulation it had at the 850 and 700 mb level. It never did have a surface low and I see no evidence of one forming at this time. At best there is a wind shift typical of an open wave. Quikscat had winds around 20 to 25 knots South of Hispaniola this morning which is also typical for a wave.

The Atl wave is becoming interesting because an anti-cyclone is building overhead. This can be seen in the shear map as well as by the way in which the cloud field is fanning out in all quadrants. There is also a noticeable lack of any stripping away of the convection by high level winds.

If the high continues to build to the West in tandem with the track of the wave we could see some development in 24 to 36 hours IMO

Here is the AVN loop showing the expanding could deck.

Link
Member Since: Posts: Comments:
999. Levi32
10:15 AM AKDT on June 21, 2008
Yeah Skye they've sure been wrong on the track. They had it way the heck east of Japan 3 days ago. I'm glad it's finally weakening...it was amazing how its eye developed despite being in the middle of all those islands. Now though the core is getting eaten up a bit, and the eye wall is now open and broken.



Member Since: Posts: Comments:
998. Levi32
10:12 AM AKDT on June 21, 2008
991. cchsweatherman 9:29 AM AKDT on June 21, 2008

I see no circulation of any kind, low-level or otherwise, and 850mb vort map doesn't support any. I don't expect any development out of the wave either. Too much shear (30+ knots)
Member Since: Posts: Comments:
997. hurricanehanna
6:11 PM GMT on June 21, 2008
995. - thanks so much Skypony!!!!
glad to know it has weakened. To think he left Louisiana and ended up in this!
Member Since: Posts: Comments:
996. Skyepony (Mod)
5:56 PM GMT on June 21, 2008
93E

click pic for loop
Member Since: August 10, 2005 Posts: 170 Comments: 38093
995. Skyepony (Mod)
5:38 PM GMT on June 21, 2008
HurricanHanna ~ Fengshen has weakend a little. Down to 80 kts or so.

Here's something to feel a little closer to the husband..Live Manila cam, working & looks like the city has power.

If your on highspeed internet last 24hrs MIMIC It's weaving through islands, got forced into a larger one & weakened. It's moved SW to NE to avoid islands.

Navy has Manila with a direct hit


They've been pretty wrong so far with this storm. Atleast it's getting weaker. I think it's avoiding land & will either go just east or South of Manila.
Member Since: August 10, 2005 Posts: 170 Comments: 38093
994. 7544
5:39 PM GMT on June 21, 2008
wave at 32 west might get interesting
Member Since: Posts: Comments:
992. Skyepony (Mod)
5:34 PM GMT on June 21, 2008
We have 93E

Aggie~ try the modify comment button 2 times in a row.
Member Since: August 10, 2005 Posts: 170 Comments: 38093
991. cchsweatherman
1:21 PM EDT on June 21, 2008


Good afternoon. In watching visible satellite loops for the tropical wave, I'm noticing obvious low-level circulation passing under Hispanola. It has been maintain convection throughout the day. Wind shear has been decreasing steadily over the past 24 hours over the wave and has become marginally favorable for tropical development. I will continue monitoring the tropical wave for tropical development, despite the low chances for such to occur.
Member Since: Posts: Comments:
990. pearlandaggie
5:20 PM GMT on June 21, 2008
off-topic but kind of funny...i suspect there will be a new rule on the way to address this sort of thing! LOL

Ambidextrous pitcher's pro debut brings game to standstill;
Switch-hurler, developed by dad, plays cat-and-mouse with switch-hitter
Member Since: September 14, 2007 Posts: 3 Comments: 3963
989. pearlandaggie
5:07 PM GMT on June 21, 2008
atmo, i don't think I personally said to download it! LOL...i got caught up in the rush, too. i usually wait for a month or so before downloading the latest version, however everyone was saying how fast the new rendering engine is in FF3. i have to say the pages do load much quicker, but that modify comment thing bugs the crap out of me!

as far as flash goes, I HATE FLASH! :) i have never had it enabled in FF...only in IE. i only use IE when I need flash apps to work correctly.
Member Since: September 14, 2007 Posts: 3 Comments: 3963
988. atmoaggie
5:00 PM GMT on June 21, 2008
i meant to type "one" instead of "on"...darn "modify comment" still doesn't work in FF3!

Glad I didn't listen when you told me to get it! I have heard ugly rumors about certain flash player applications not working, too.
Member Since: Posts: Comments:
987. pearlandaggie
4:51 PM GMT on June 21, 2008
i meant to type "one" instead of "on"...darn "modify comment" still doesn't work in FF3!
Member Since: September 14, 2007 Posts: 3 Comments: 3963
986. pearlandaggie
4:48 PM GMT on June 21, 2008
latest solar magnetogram...only on SC23 spot to speak of....

Member Since: September 14, 2007 Posts: 3 Comments: 3963
985. txalwaysprepared
4:47 PM GMT on June 21, 2008
FLW it got quiet mighty quickly LOL

See anything interesting out there, yet?
Member Since: Posts: Comments:
984. pearlandaggie
4:45 PM GMT on June 21, 2008
Days turn the corner toward darkness
Member Since: September 14, 2007 Posts: 3 Comments: 3963
983. pearlandaggie
4:44 PM GMT on June 21, 2008
happy summer solstice to everyone! :)

hot and dry as usual here in texas!
Member Since: September 14, 2007 Posts: 3 Comments: 3963
982. FLWeatherFreak91
12:40 PM EDT on June 21, 2008
Um.. massive blog whole?
Member Since: Posts: Comments:
981. Boatofacar
4:03 PM GMT on June 21, 2008
Well...I was gonna cruise my junk over to Old Town near Disney...but the radar says rain! Oh well...we need it!
Member Since: Posts: Comments:
980. melwerle
3:56 PM GMT on June 21, 2008
Everyone have a great day...gonna go find something to do that doesn't require a bunch of outside time (too HOT). BBL
Member Since: Posts: Comments:
979. weathermanwannabe
11:42 AM EDT on June 21, 2008
Hey......I'm out (gonna get out before the showers this afternoon) but definately getting into that Summer pattern here in North Florida, and, I really do not mind the rain at all (it's a good thing) ......BBL
Member Since: Posts: Comments:
978. IKE
10:38 AM CDT on June 21, 2008
Good morning.........
Member Since: Posts: Comments:
977. weathermanwannabe
11:29 AM EDT on June 21, 2008
975. IKE 11:19 AM EDT on June 21, 2008
Morning Ike......Just a quick spot check before hitting some Saturday chores with the kids.......Yeah, in looking at the WV loop this am, plenty of moisture with that wave lifing up from the ITCZ.....Once some of sheer dies down in the MDR, the CV waves will be rocking along (plenty of moisture in the Gulf this am too.......Shot our my original plans to take the kids down to St. George island today as it is raining down there right now)...
Member Since: Posts: Comments:
976. severstorm
11:20 AM EDT on June 21, 2008
HIEXPRESS can i have the link to the website for that lighting data TIA
Member Since: Posts: Comments:
975. IKE
10:18 AM CDT on June 21, 2008
The wave out in the eastern Atlantic has some hope...

"...Tropical waves...
tropical wave is along 32w S of 11n moving W near 20 kt. Broad
mid level inverted-v curvature is shown on satellite imagery and
the mimic-tpw animation depicts a moisture surge between
27w-33w. The upper level flow is keeping most of the convection
to the W of the wave axis. Clusters of scattered moderate/
isolated strong convection are within 225w nm of the wave.".........

From the 8:05am EDST atlantic weather discussion.
Member Since: Posts: Comments:
974. txalwaysprepared
3:15 PM GMT on June 21, 2008
IKE either way, you took time to post it :)
Member Since: Posts: Comments:
973. HIEXPRESS
11:12 AM EDT on June 21, 2008
NOAA SE US Lightning Probability
Member Since: Posts: Comments:
972. IKE
10:12 AM CDT on June 21, 2008

969. txalwaysprepared 10:11 AM CDT on June 21, 2008
IKE thank you so much! I understand now :)


That was the pasted definition/meaning. Not my words.
Member Since: Posts: Comments:
971. IKE
10:11 AM CDT on June 21, 2008
965. hurricane23 10:04 AM CDT on June 21, 2008
Morning!

GOM is all divergence.No tropical concerns during the next 3-5 days if not longer.MJO pulse in about 2 weeks may try to spark up something close to home. Adrian


You're probably right.
Member Since: Posts: Comments:
970. sporteguy03
3:07 PM GMT on June 21, 2008
I really hope the season stays quiet as fluid as that may sound we do not need any systems wrecking havoc on anyone. I still preapare though but each day with no tropical activity threatening anyone is a good day.
Member Since: Posts: Comments:
969. txalwaysprepared
3:10 PM GMT on June 21, 2008
IKE thank you so much! I understand now :)
Member Since: Posts: Comments:
968. IKE
10:06 AM CDT on June 21, 2008
(Trough, Trough Aloft, Upper Level [Cold] Low) An elongated area of relatively low pressure, at constant altitude, in the atmosphere. The opposite of an upper level ridge. Upper level troughs are usually oriented north-south with the north end open. That is, air currents moving from west to east around the earth flow around three sides of the trough then turn eastward rather than toward the west, as in the case of a closed circulation. A large upper level trough may have one or more small upper level closed low circulation systems within it.
Member Since: Posts: Comments:
967. txalwaysprepared
3:04 PM GMT on June 21, 2008
IKE re:963. What does that mean, exactly?
Member Since: Posts: Comments:
966. hurricanehanna
3:03 PM GMT on June 21, 2008
Thanks Patrap.
Member Since: Posts: Comments:
965. hurricane23
11:02 AM EDT on June 21, 2008
Morning!

GOM is all divergence.No tropical concerns during the next 3-5 days if not longer.MJO pulse in about 2 weeks may try to spark up something close to home. Adrian

Member Since: Posts: Comments:
964. txalwaysprepared
3:02 PM GMT on June 21, 2008
Good Shots!! Sadly, I'd love to have those clouds over me right now. Need.The.Rain.

I got lucky on this one a couple days ago, on my cell. Just happened to get the lightning in there.


(not sure the photo will show up)

FLW yes, my husband thinks I'm nuts for wanting to be outside during teh storms!! LOL
Member Since: Posts: Comments:
963. IKE
10:00 AM CDT on June 21, 2008
Upper level trough in the GOM according to the latest discussion...

"with an upper level shortwave trough extending from
the N Gulf Coast near Mobile Alabama to the W Bay of Campeche.
Member Since: Posts: Comments:
962. melwerle
2:57 PM GMT on June 21, 2008
Too funny Fl - I was inside the movie theatre the other day when a great storm hit here - I was pissed I missed the majority of it. Texts were coming in on my cell asking if I was safe...I was really mad that I missed the good stuff (but I do stay inside if there is lightning - call me a chicken)
Member Since: Posts: Comments:
961. IKE
9:55 AM CDT on June 21, 2008
Those are some rough storm clouds....around Tampa..........
Member Since: Posts: Comments:
960. FLWeatherFreak91
10:48 AM EDT on June 21, 2008
Those were taken about 10 min ago in Westchase (North of Tampa) facing West toward the Severe t-storm... Heck no I wouldn't be inside... I'm not missin' that!
Member Since: Posts: Comments:
959. melwerle
2:47 PM GMT on June 21, 2008
Wow FlWeather - when were THOSE taken and where?

I'd be hiding in the hallway closet if that was outside...
Member Since: Posts: Comments:
958. FLWeatherFreak91
10:44 AM EDT on June 21, 2008
Honestly the worst Storm I have seen in years: Sorry about the sideways-ness.... I was in a hurry

img src="Photobucket" alt="" />pic 1
img src="Photobucket" alt="" />
pic2

img src="Photobucket" alt="" />pic3

<>img src="Photobucket" alt="" />
Member Since: Posts: Comments:
957. rainraingoaway
8:30 AM CST on June 21, 2008
Good morning all. I see we have a new blob. Hope you all are well today.
Member Since: Posts: Comments:
956. mermaidlaw
2:21 PM GMT on June 21, 2008
Thanks Terra, I live in Hernando county, North West Of Tampa. Looks like we are about to get hit here. We need the rain, but not the T&L.
Member Since: Posts: Comments:
955. TerraNova
2:17 PM GMT on June 21, 2008
The GOM blob will probably not develop but moisture from it will spread NE towards West Florida/Panhandle and bring much needed rain to those areas. Early day thunderstorms with heavy downpours are popping up over the area north of Tampa.

SVR just issued for the northern portion of downtown Tampa.
Member Since: Posts: Comments:
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.
Member Since: Posts: Comments:

Viewing: 1004 - 954

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.