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: 1254 - 1204

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

1254. 0741
5:43 AM GMT on June 22, 2008
i saw radar that you hammer in afternoon
Member Since: Posts: Comments:
1252. 0741
5:34 AM GMT on June 22, 2008
you up late tonight? how was your weather? we got late storm here in miami i was at my friend house round 8:30pm when i could hear thunder
Member Since: Posts: Comments:
1248. 0741
5:27 AM GMT on June 22, 2008
here on water vapor you see shear to north wave and see it affect it why do people see invest with this wave??? i donot
Member Since: Posts: Comments:
1245. 0741
5:23 AM GMT on June 22, 2008
you right some say their anticycle over it do you see that their post shear that point to anticycle over it
Member Since: Posts: Comments:
1244. TampaSpin
1:22 AM EDT on June 22, 2008
Invest:
A weather system for which a tropical cyclone forecast center (NHC, CPHC, or JTWC) is interested in collecting specialized data sets (e.g., microwave imagery) and/or running model guidance. Once a system has been designated as an invest, data collection and processing is initiated on a number of government and academic web sites, including the Naval Research Laboratory (NRL) and the University of Wisconsin Cooperative Institute for Meteorological Satellite Studies (UW-CIMSS). The designation of a system as an invest does not correspond to any particular likelihood of development of the system into a tropical cyclone; operational products such as the Tropical Weather Outlook or the JTWC/TCFA should be consulted for this purpose.
Member Since: September 2, 2007 Posts: 179 Comments: 20448
1242. 0741
5:18 AM GMT on June 22, 2008
jp some here saying we could see 92l by later today i told them i donot even if have anticycle
Member Since: Posts: Comments:
1241. Skyepony (Mod)
5:19 AM GMT on June 22, 2008
ASCAT caught the wave in question about 4 hrs ago..
it's at the top


Surfmom~ Glad you happened across Hades when you did. Nite.
Member Since: August 10, 2005 Posts: 225 Comments: 39388
1240. 0741
5:12 AM GMT on June 22, 2008
you see how wave look past 24 hour on this loopLink
Member Since: Posts: Comments:
1239. TampaSpin
1:15 AM EDT on June 22, 2008
1237. jphurricane2006 1:14 AM EDT on June 22, 2008
jrrp showed a shortwave image, not water vapor


Jp if you read back it was not his pic we was referring to it was Stormchasers...lol

Member Since: September 2, 2007 Posts: 179 Comments: 20448
1236. TampaSpin
1:14 AM EDT on June 22, 2008
goodnite everyone.......
Member Since: September 2, 2007 Posts: 179 Comments: 20448
1235. TampaSpin
1:08 AM EDT on June 22, 2008
Watervopor pic.....
Member Since: September 2, 2007 Posts: 179 Comments: 20448
1234. TampaSpin
1:06 AM EDT on June 22, 2008
Most recent pic...
Member Since: September 2, 2007 Posts: 179 Comments: 20448
1233. Stormchaser2007
5:05 AM GMT on June 22, 2008
Oh I thought he was referring to post 1216. sorry
Member Since: Posts: Comments:
1232. TampaSpin
1:02 AM EDT on June 22, 2008
1229. 0741 1:01 AM EDT on June 22, 2008
jrrpp that sat pic make it look more stronger look at one that stormchaser post


Stormchaser post was a watervopor.....not a very good pic of a tropical system.
Member Since: September 2, 2007 Posts: 179 Comments: 20448
1231. Stormchaser2007
5:01 AM GMT on June 22, 2008
Thats because mines more recent...
Member Since: Posts: Comments:
1230. surfmom
4:58 AM GMT on June 22, 2008
jeeze i just signed off, but i read your information. I believe the americans were schedule to be in Cebu several days ( our thursday/friday) before the wedding --i am just grateful to Hades because he alerted me well in advance and i was able to alert my friend that this TD was reeving up to a typhoon's well before the PI authorities were -- I did my best, I know he got my message b/4 the storm hit .... so at least i was able to do that
Member Since: Posts: Comments:
1229. 0741
4:59 AM GMT on June 22, 2008
jrrpp that sat pic make it look more stronger look at one that stormchaser post
Member Since: Posts: Comments:
1228. Stormchaser2007
5:00 AM GMT on June 22, 2008
1227. What?
Member Since: Posts: Comments:
1227. JRRP
4:55 AM GMT on Junio 22, 2008
mmmmmmmmmmm ¬¬

Member Since: Posts: Comments:
1226. 0741
4:55 AM GMT on June 22, 2008
to tell you ture i see it coming apart by sunday night maybe few shower will affect islands by tue but i donot see it been strong wave at all i see as weaking wave because high shear anticycle wont help this wave
Member Since: Posts: Comments:
1225. surfmom
4:53 AM GMT on June 22, 2008
I AM SIGNING OFF - YOU MAY NEVER EVER SEE ME UP THIS LATE AGAIN - HAVE A GOOD NIGHT

SKYE HAVE A GOOD nIGHT, and kiss that special horse of yours on the nose for me -- Skepony looks to be one of those special souls --like my centi,
Member Since: Posts: Comments:
1224. Stormchaser2007
4:55 AM GMT on June 22, 2008
1221. Well im not calling this 92L because i dont believe that it will develop into anything major...
Member Since: Posts: Comments:
1223. Stormchaser2007
4:52 AM GMT on June 22, 2008
1218. Well that may be true but the NHC has become more conservative with declaring invests...so I dont know if they would declare this unless it was an immediate threat to develop.
Member Since: Posts: Comments:
1222. Skyepony (Mod)
4:44 AM GMT on June 22, 2008
Well today is tommarrow over there. They should have already been there. The nearest big city from San Juan is Manila. The ferry was going on a regular run from Manila to Cebu. Other than 4 confirmed the news on the other 696 is anywhere from stranded to missing. Looking at some of those youtubes, I could imagine there will be stories...
Member Since: August 10, 2005 Posts: 225 Comments: 39388
1221. 0741
4:49 AM GMT on June 22, 2008
((Well it looks good now...))
look at cloud too north of wave you see shear plus look at carribbean you see shear blowing from west to east by later tonight it will like other wave i donot see invest 92 like some of you are saying
Member Since: Posts: Comments:
1220. surfmom
4:52 AM GMT on June 22, 2008
B I N G O
Member Since: Posts: Comments:
1219. Stormchaser2007
4:51 AM GMT on June 22, 2008
Water Vapor looks rather moist in its path...

Member Since: Posts: Comments:
1218. TampaSpin
12:51 AM EDT on June 22, 2008
1216. Stormchaser2007 12:49 AM EDT on June 22, 2008

This would be an invest the way it looks now if we was in August..
Member Since: September 2, 2007 Posts: 179 Comments: 20448
1217. surfmom
4:48 AM GMT on June 22, 2008
well, I like to see some kind of a hurricane b/4 July --my mom is scheduled to visit and the mate is already making a ruckus. i'd rather live through a cane then watch the two of them go at it It is the first time in my life i have wished for a cane-- i am hoping that if we have one she'll be too afraid to visit and disturb the household peace
Member Since: Posts: Comments:
1216. Stormchaser2007
4:48 AM GMT on June 22, 2008
Well it looks good now...

Member Since: Posts: Comments:
1215. surfmom
4:42 AM GMT on June 22, 2008
The grass is wonderful. two days ago we were out seeding the pastures. we tried Argentine Bahia --it has very deep roots and another grass that is quick growing but doest have the roots that the Argentine Bahia has. on some of the pastures here in SWFL we had to spread some lime, in order for the fertilizer to work
Member Since: Posts: Comments:
1214. 0741
4:43 AM GMT on June 22, 2008
anticyclone will not save that wave in central atlantic ((that i was trying say)) error in that line
Member Since: Posts: Comments:
1213. txalwaysprepared
4:43 AM GMT on June 22, 2008
TS LOL... yep.. that's about my 3 kiddos. hahaha
Member Since: Posts: Comments:
1212. JRRP
4:40 AM GMT on Junio 22, 2008
.
Member Since: Posts: Comments:
1211. surfmom
4:38 AM GMT on June 22, 2008
The wedding was sched. for today --june 21, there was a handful of americans (his sister ,son etc. they are very american and the village outside of Cebu is very primitive. I am sure they are OK, but these are people who are use to amenities --guess there will be some interesting stories when they get back.
Member Since: Posts: Comments:
1210. 0741
4:15 AM GMT on June 22, 2008
everyone look at sat pic of area in central atlatic you see shear in eastern carribbean anticyclone will save that wave in central atlantic look at later today you see shear system as it move more west what i see it already getting shear Link
Member Since: Posts: Comments:
1209. Skyepony (Mod)
4:37 AM GMT on June 22, 2008
That's alotta dancin babys for all the rain we been havin:)

Yeah mine really have had alotta fun after these rains the last week. & the pasture grass..
Member Since: August 10, 2005 Posts: 225 Comments: 39388
1208. Skyepony (Mod)
4:28 AM GMT on June 22, 2008
when was the wedding to be?
Member Since: August 10, 2005 Posts: 225 Comments: 39388
1207. surfmom
4:29 AM GMT on June 22, 2008
Good to see you skyepony! my four leggeds were thrilled with the rain today - they came galloping over to see me splashing in the puddles, my favorite Centi --he was so wonderful to watch --funny how when i want to ride him through a puddle he's sooo afraid, but when playing in the pasture stomp, splash total horse joy
Member Since: Posts: Comments:
1206. TampaSpin
12:31 AM EDT on June 22, 2008
Look what i found in the closet......lmao
Member Since: September 2, 2007 Posts: 179 Comments: 20448
1205. Skyepony (Mod)
4:22 AM GMT on June 22, 2008
Here's one from a shrinking shore.
Member Since: August 10, 2005 Posts: 225 Comments: 39388
1204. surfmom
4:23 AM GMT on June 22, 2008
Thanks Tigger , my best BUDDY is smart but he's a surfer soooo smart can be relative at timeS. most of the time he's at san juan,. but the wedding was scheduled to be in Cebu -- a very small village in the area of cebu
Member Since: Posts: Comments:

Viewing: 1254 - 1204

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.

JeffMasters's Recent Photos

Lake Effort Snow Shower Over Windsor, Ontario
Sunset on Dunham Lake
Pictured Rocks Sunset
Sunset on Lake Huron