The future of flooding

By: Dr. Jeff Masters , 10:06 PM GMT on February 19, 2008

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Are storms getting more extreme due to climate change? That is a difficult question to answer, since reliable records are not available at all in many parts of the world, and extend back only a few decades elsewhere. However, we do have a fairly good set of precipitation records for many parts of the globe, and those records show that the heaviest types of rains--those likely to cause flooding--have increased in recent years. 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. Satellite measurements (Trenberth et al., 2005) have shown a 1.3% per decade increase in water vapor over the global oceans since 1988. Santer et al. (2007) used a climate model to study the relative contribution of natural and human-caused effects on increasing water vapor, and concluded that this increase was "primarily due to human-caused increases in greenhouse gases". This was also the conclusion of Willet et al. (2007).

More water vapor equals more precipitation
This increase in water vapor has very likely led to an increase in global precipitation. For instance, 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, there is a large natural variation in extreme precipitation events.

Pollution may contribute to higher precipitation
It is possible that increased pollution is partly responsible for the increase in precipitation and in heavy precipitation events in some parts of the world. According to Bell et al. (2008), summertime rainfall over the Southeast U.S. is more intense on weekdays than on weekends, with Tuesdays having 1.8 times as much rain as Saturdays during the 1998-2005 period analyzed. Air pollution particulate matter also peaks on weekdays and has a weekend minimum, making it likely that pollution is contributing to the observed mid-week rainfall increase. Pollution particles act as "nuclei" around which raindrops condense, increasing precipitation in some storms.

The future of flooding
It is difficult to say if the increase in heavy precipitation events in recent years has led to more flooding, since flooding is critically dependent on how much the landscape has been altered by development, upstream deforestation, and what kind of flood control devices are present. One of the few studies that did attempt to quantify flooding (Milly et al., 2002) found that the incidence of great floods has increased in recent decades. In the past century, the world's 29 largest river basins experienced a total of 21 "100-year floods"--the type of flood one would expect only once per 100 years in a given river basin. Of these 21 floods, 16 occurred in the last half of the century (after 1953). With the IPCC predicting that heavy precipitation events are very likely to continue to increase, it would be no surprise to see flooding worsen globally in the coming decades.

Jeff Masters

References
Bell, T. L., D. Rosenfeld, K.-M. Kim, J.-M. Yoo, M.-I. Lee, and M. Hahnenberger (2008), "Midweek increase in U.S. summer rain and storm heights suggests air pollution invigorates rainstorms," J. Geophys. Res., 113, D02209, doi:10.1029/2007JD008623.

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.

Milly, P.C.D., R.T. Wetherald, K.A. Dunne, and T.L.Delworth, Increasing risk of great floods in a changing climate", Nature 415, 514-517 (31 January 2002) | doi:10.1038/415514a.

Santer, B.D., C. Mears, F. J. Wentz, K. E. Taylor, P. J. Gleckler, T. M. L. Wigley, T. P. Barnett, J. S. Boyle, W. Brüggemann, N. P. Gillett, S. A. Klein, G. A. Meehl, T. Nozawa, D. W. Pierce, P. A. Stott, W. M. Washington, and M. F. Wehner, 2007, "Identification of human-induced changes in atmospheric moisture content", PNAS 2007 104: 15248-15253.

Trapp, R.J., N.S. Diffenbaugh, H.E. Brooks, M.E. Baldwin, E.D. Robinson, and J.S. Pal, 2007, Severe thunderstorm environment frequency during the 21st century caused by anthropogenically enhanced global radiative forcing, PNAS 104 no. 50, 19719-19723, Dec. 11, 2007.

Trenberth, K.E., J. Fasullo, and L. Smith, 2005: "Trends and variability in column-integrated atmospheric water vapor", Climate Dynamics 24, 741-758.

Willett, K.M., N.P. Gillett, P.D. Jones, and P.W. Thorne, 2007, "Attribution of observed surface humidity changes to human influence", Nature 449, 710-712 (11 October 2007) | doi:10.1038/nature06207.




Winter Flooding (Jmroh)
This is the result of extreme snowmelt and 4 inches of rain.
Winter Flooding
Yellow River Starke County Indiana (StarkeHistorian)
Kankakee Game Preserve, 10 Mile Road: The Yellow River crested this morning at 12.14' at the US35 bridge at 11:45AM. This was 2.14' over flood stage. The record is 15.3 Jan 1, 1991.
Yellow River Starke County Indiana

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251. Patrap
5:27 PM GMT on February 23, 2008
Thats a good link for a home page 23. Many will benefit from that site.
Member Since: July 3, 2005 Posts: 415 Comments: 125715
250. hurricane23
5:25 PM GMT on February 23, 2008
Hey Pat!

Thats a create link for hurricane preparations infact its on my front page on my website.Here is the page i dedicated to hurricane preparedness on my site.
Member Since: May 14, 2006 Posts: 8 Comments: 13597
249. ShenValleyFlyFish
5:13 PM GMT on February 23, 2008
Member Since: September 9, 2007 Posts: 36 Comments: 4687
248. ShenValleyFlyFish
5:11 PM GMT on February 23, 2008
CORRECTION Post # 224 by this writer contains a MAJOR ERROR. Reference to the Weather Underground in the TV show was not to this site. They were discussing a ridiculous attempt to tie Presidential Candidate Obama to the 60's radical group by the same name. (bet the founders if this site have had second thoughts about an inside university joke LoL)

My apologies to all
Shen
Member Since: September 9, 2007 Posts: 36 Comments: 4687
245. TampaSpin
4:31 PM GMT on February 23, 2008
There appears to be some rotation just off St. Petersburg beach area.
Member Since: September 2, 2007 Posts: 177 Comments: 20430
244. TampaSpin
4:14 PM GMT on February 23, 2008
Radar might be showing a vortex just north west of Tampa
Member Since: September 2, 2007 Posts: 177 Comments: 20430
243. Patrap
4:02 PM GMT on February 23, 2008
Create a Family Hurricane Plan today Link
Member Since: July 3, 2005 Posts: 415 Comments: 125715
242. hurricane23
3:41 PM GMT on February 23, 2008
Things could change for the atlantic this season as i think unfavorable conditions could be around this season with the main threat being similar to what we saw back in 07.It will be interesting to see if colorado state university lower there numbers a bit on there next update.

Will see how things evolve in the comings weeks and months and always remember it only takes one.

Found this Seasonal Euro Tropical Precip Forecast rather interesting across the atlantic!

www.AdriansWeather.com
Member Since: May 14, 2006 Posts: 8 Comments: 13597
241. HIEXPRESS
3:38 PM GMT on February 23, 2008
Right under that front in E. Cent Fl. Just rain here.
Member Since: October 13, 2005 Posts: 4 Comments: 2155
240. Patrap
3:25 PM GMT on February 23, 2008
2008 Atlantic Seasonal Hurricane Forecast
Link



Extended Range Forecast of Atlantic Seasonal Hurricane Activity and U.S. Landfall Strike Probability for 2008 - PDF Format Link


Morning to you JFV....
Member Since: July 3, 2005 Posts: 415 Comments: 125715
237. stormdude77
3:20 PM GMT on February 23, 2008
Good morning!

235. JFV 11:12 AM AST on February 23, 2008

Can you believe that it is almost the month of March already? Before we know it, the infamous June 1st date will arrive.

You got that right ... time is really moving along at a fast rate, Pre Season predictions will soon begin...

236. Patrap
3:18 PM GMT on February 23, 2008
Please Kind sir's, May I have the Early seasonal Prediction's on the Atlantic Basin tropics?

Member Since: July 3, 2005 Posts: 415 Comments: 125715
233. ShenValleyFlyFish
3:04 PM GMT on February 23, 2008
Good morning JFV
Member Since: September 9, 2007 Posts: 36 Comments: 4687
231. TampaSpin
2:49 PM GMT on February 23, 2008
Hi Shen....good to hear from ya. You got mail back at you ......dont fall out of your chair....lol
Member Since: September 2, 2007 Posts: 177 Comments: 20430
230. mermaidlaw
2:47 PM GMT on February 23, 2008
Good morning everyone!:) That rain has been over me for about two hours now, here in Hernando county, fl. We sure need it!!
Have a good day, and please stay safe!
Member Since: July 23, 2006 Posts: 20 Comments: 8736
229. ShenValleyFlyFish
2:41 PM GMT on February 23, 2008
226. TampaSpin 9:13 AM EST on February 23, 2008

Hey TS, long time no see. you got mail
Member Since: September 9, 2007 Posts: 36 Comments: 4687
228. TampaSpin
2:35 PM GMT on February 23, 2008
Member Since: September 2, 2007 Posts: 177 Comments: 20430
227. TampaSpin
2:22 PM GMT on February 23, 2008
looks like we are about to get some rain
Member Since: September 2, 2007 Posts: 177 Comments: 20430
226. TampaSpin
2:13 PM GMT on February 23, 2008
Thank God for the NY Times they have upriled the Republican party with their attack and it really does not matter who wins on the Democratic party. Independents are also upset with this attack that was leaning toward Obama. Thank you NY Times....lol
Member Since: September 2, 2007 Posts: 177 Comments: 20430
225. vortfix
2:11 PM GMT on February 23, 2008
Central Florida and the Tampa area......here it is:



224. ShenValleyFlyFish
1:57 PM GMT on February 23, 2008
Correction the following contains a Major Error. The WU mentioned was the 1960's Leftest Radical group the Weathermen. Other than the tongue in cheek inside joke explained in the History of WU They have no connection to this site. I have stripped all identifying information from the post but have let it stand to maintain continuity in the discussion. Again THIS BLOG CONTAINS A MAJOR ERROR.
Shen

I was channel surfing last night watching the political news (FOX, CNN, MSNBC, ETC) and on MSNBC they were talking about Obama and some of the "hits" he was taking (MSNBC is obviously way way for Obama, CNN supports Hillary and of course, Fox leans toward McCain) anyway, Keith Obrian was talking about the blogs picking on poor Obama and he mentioned a "hit" on him from Weatherunderground! nothing more was said about it and I was stunned. Do any of you recall which blog this was in and when it was posted???

NO WAY!!! Do news people now read our WU blogs for news??? ISN'T THAT CRAZY!!!

*******************
The eyes of the world are literally focused upon us. Are we going to look like a bunch of bickering buffoons or or intelligent people worthy of respect? The choice is ours not admin's they can only act after the fact. This kind of notoriety is bound to attract some of the lunatic fringe. Do we tolerate their ravings and antics in some mistaken notion of "free speech" or do we accept that is an open forum dedicated to public discussion of serious issues and those who distract or disrupt this assembly will be respectfully but firmly held to the standards of public discourse? The constitution protects the "right of the people to peaceably assemble" not hold a riot. As one who has gulped more lung-fulls of tear gas than all the chicken-hawks in DC combined attempting to nonviolently protect that right I submit that we must hold each other to the highest standards of public discourse.
Member Since: September 9, 2007 Posts: 36 Comments: 4687
223. ShenValleyFlyFish
1:06 PM GMT on February 23, 2008
207. cchsweatherman 4:59 PM EST on February 22, 2008
Like I have stated before surfmom, I make my own forecasts. I must reiterate the fact that I'm only an amateur meteorologist, so do not rely on my forecast too much.


What is this? Humility on a WU blog? From one so young?

Refreshing
Member Since: September 9, 2007 Posts: 36 Comments: 4687
222. surfmom
1:06 PM GMT on February 23, 2008
Thanks for the weather & pics...looks like the wet is passing above me here in SRQ,so off to the barn to get the four-leggeds moving & groovin. Maybe a small shot of puny waves late this afternoon. adios
Member Since: July 18, 2007 Posts: 30 Comments: 26536
221. HIEXPRESS
12:36 PM GMT on February 23, 2008
.
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220. Cavin Rawlins
12:23 PM GMT on February 23, 2008
CENTRAL AMERICA AND THE CARIBBEAN REGION....

Upper ridging and very dry stable flow covers most of the Caribbean Basin this morning thereby hindering any shower activity and allowing fair conditions to exist at the surface. High pressure ridging remains in control providing 10-25 knot easterly flow, which is driving 6-10 ft swells through the region. The trades are also seen advecting an abundance of high-pressure stratocumulus from the Atlantic, across the Islands to 70W and across the Northwest Caribbean north of 15N and west of 70W.

CENTRAL TROPICAL ATLANTIC...

An upper trough axis roughly lies from 30N/50W to 12N/55W. Very dry confluent stable confluent flow is seen from the Islands to 45W with mid-upper cloudiness and possible showers seen from the ITCZ near 10N/45W to beyond 20N/25W near the Cape Verdes Islands. The surface Azores High is analyzed 1030 mb at 40N/40W. This high is producing a large area of moderate to strong trades and fair weather across the Atlantic with only stable stratocumulus embedded within this flow.

BY W456
Member Since: July 24, 2005 Posts: 407 Comments: 19076
218. Cavin Rawlins
12:04 PM GMT on February 23, 2008
Good Saturday morning to all:

....SYNOPSIS....

GULF OF MEXICO/NORTHWEST ATLANTIC OCEAN WEST OF 50W....

A combination of dry confluent flow at 200 mb and a weak surface pressure pattern is allowing fair skies and tranquil conditions to exist across Mexico, the Northwestern Gulf, Texas and parts of the Deep South. Rawinsonde data and surface observations indicate that a fair amount of moisture remains within the surface layer and thus low clouds and fog may result across some parts. Meanwhile, an upper level high situated over the Caribbean is producing southwesterly upper level flow over much of the Southeastern Gulf with upper level moisture producing scattered to broken mid-upper level cloudiness from the Eastern Bay of Campeche to the Florida Peninsula and beyond. A surface cold front extends from 23N/90W to the Florida Panhandle, enhancing the moisture plume outlined. Due to the weak surface pressure pattern, winds and seas will remain light with swells below 5 ft for the next 12-24 hrs.

Scattered cloudiness and showers are invading the Southwest North Atlantic in association with a frontal system driven by southwesterly upper level flow around the aforementioned upper ridge. Meanwhile, surface high pressure ridging dominates the area anchored by a 1029 mb near 31N/43W. This ridge is aiding in mostly fair weather and producing light to moderate anticyclonic flow across the Atlantic ahead of the moisture plume.

by W456
Member Since: July 24, 2005 Posts: 407 Comments: 19076
217. Drakoen
5:17 AM GMT on February 23, 2008
waves to everyone...
Member Since: October 28, 2006 Posts: 57 Comments: 29714
216. Tazmanian
3:19 AM GMT on February 23, 2008
are weekend storm now has a eye-like feature
Member Since: May 21, 2006 Posts: 5089 Comments: 114075
215. Patrap
11:51 PM GMT on February 22, 2008
LSU Earth Scan Lab Link
Member Since: July 3, 2005 Posts: 415 Comments: 125715
214. tmangray
11:36 PM GMT on February 22, 2008
Powerful storm cranking up off the West Coast. NWS has the low center "bombing" off northern California. Storm wind warning already hoisted for the outer waters, likely to extend to the coast by tomorrow. Large waves expected. Damaging winds expected onshore in northern and central California, perhaps a repeat of January's megastorm. Rainfall is expected to be very heavy. Snowfall in the Sierras will add several feet to the already ample snowpack.
213. surfmom
10:54 PM GMT on February 22, 2008
Thanks for the heads up cchsWeathermen, I know you are not a PRO, but you often have keen observations. Off to dinner thanks for your time
Member Since: July 18, 2007 Posts: 30 Comments: 26536
210. cchsweatherman
10:27 PM GMT on February 22, 2008
How's everything been JFV? Hope school's treating you well.
Member Since: April 14, 2007 Posts: 8 Comments: 5030
208. stuartl
10:13 PM GMT on February 22, 2008
Wow. Isn't this an interesting thread.

I'm from Gloucester in the sw of England and last 'summer' we had some of the worst flooding ever. It was truly amazing to see.

Roads that don't appear to be near water were several feet under... Fields submerged... River levels beating all historic highs...

I found some pics to add to the shots of mayhem:

http://www.bbc.co.uk/gloucestershire/content/articles/2007/07/23/flood_gallery_feature.shtml

Apparently, for us at least, a real issue is that the River Severn hasn't been dredged in over 20 years. The buildup of silt is apparently so great that the bottom of the river is 30 feet higher than it used to be.
207. cchsweatherman
9:59 PM GMT on February 22, 2008
Like I have stated before surfmom, I make my own forecasts. I must reiterate the fact that I'm only an amateur meteorologist, so do not rely on my forecast too much.
Member Since: April 14, 2007 Posts: 8 Comments: 5030
206. vortfix
9:56 PM GMT on February 22, 2008

205. cchsweatherman
9:45 PM GMT on February 22, 2008
Taking a look at the latest models, I'm expecting there could be some strong storms and showers coming Wednesday. The NWS has already begun talking about this system in their discussions and it is mainll calling for a dramatic temperature drop coming Wednesday night and Thursday morning. We will have to wait and see about this system.
Member Since: April 14, 2007 Posts: 8 Comments: 5030
204. surfmom
9:43 PM GMT on February 22, 2008
Checked the weekly forecast and it gives only 30 percent chance --cchsWeatherman are you seein g more here then meets the eye?
Member Since: July 18, 2007 Posts: 30 Comments: 26536
203. surfmom
9:41 PM GMT on February 22, 2008
Hmmmm, just dropped in cchsweatherman - what's up with this storm you are expecting in FL. Bascially when & where --lots of rain, would appreciate your input as I have horses to exercise this weekend for a major polo game. thanks
Member Since: July 18, 2007 Posts: 30 Comments: 26536
202. cchsweatherman
9:34 PM GMT on February 22, 2008
Good afternoon all! Hope everyone is doing fine and getting ready to enjoy the upcoming weekend. I'm watching that storm Taz since it could have a major impact here in Florida with a huge temperature drop late this upcoming week.
Member Since: April 14, 2007 Posts: 8 Comments: 5030
201. Whit
8:37 PM GMT on February 22, 2008
One must not be quick to base increased heavy rain events on global warming. Consider the fact that Western weather patterns have been significantly altered in recent years by the El Nino and La Nina effects. Don't play the "global warming" card just because it sounds cool. The evidence is simply not there as sufficiently as many scientists claim.

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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.