Two 500-year floods in 15 years
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
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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.
Without a doubt. They will certainly still get winds, how much and the surge still in question, but possible.
Yep, I lived in Mandeville for a number of years...through the lovely Katrina's arrival...it's a wonder that there are any businesses left south of the Interstate; they jumped their rates by 300-600 percent after the storm, if you could them to write at all... and trust me, Citizens is no option!
Yeah gotta go pick some light bulbs up at the hard ware store....be back later.
Make sure you get the enviromentally good ones.........LMAO....
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Tropical Storm "FRANK" is expected to enhance the southwest monsoon and bring rains over the rest of Mindanao and Visayas and later to Southern Luzon. Residents in low lying areas and near mountain slopes are advised to take all the necessary precautions against possible flashfloods and landslides. Likewise, those living in coastal areas are alerted against big waves or storm surges generated by this tropical cyclone.
The public and the disaster coordinating councils concerned are advised to take appropriate action and watch for the next bulletin to be issued at 5 a.m. tomorrow.
Little too close for comfort.
Its Pretty much done with eye formation
Does Cantore travel that far? Just pickin'
I think Its really hard for a cyclone to develop in the west pacific and not become a Cat 4
while your on the way to becoming a cat 4 why don't you just skip several of the not so important stops like typhoon and major typhoon
Why does the NHC have an Alt floater titled Fengshen showing the Yucatan Penn?
Cause that broad area around 17N -93W caught my eye this afternoon (see my post below)....Lol; I wish..........Probababy just a temporary error on the part of both NHC and Me....Lol
Pensacola, you got it..local boy right here myself..think we did a damn fine job concidering the circumstances.
Been in meetings and late to add my input but don't forget Navarre, Fort Walton Beach, and Destin. They all experienced the eastern eyewall of those storms and came back with a flurry afterwards. Just look at the rebuilding in those parts now. You would never know a Hurricane hit just 3 years ago.
Thank You Fengshen for enrolling in West Pacific University for a total of 24 hours. Here is your degree in Extensive Rainfall and Rapid Intensification. You now have the super typhoon license allowing you to become a super typhoon within 8 hours.
It would take a large number of things to happen just right for Manila to take a dead on hit...most likely the storm will recuirve before it even gets that far, not to mention it would certainly have to gain 6 or 7 degrees of latitude. Here's the projected path over the next several days:
BTW - love your icon!
thnx, hanna...I like him
Weakening Flag : OFF
Rapid Dissipation Flag : OFF
Thats not good...
Thanks!
Curve band arc - 1.50 for a DT of 4.5
Model Expected T - no also agrees with DT 4.5
Final T-no 4.5/77 knots/966 mb.
Also checking in from AL/FL GC (literally on the line), we did do well with our rebuilding. My only complaint is that all the beach houses "sold out" to the condo developers after Ivan and our beaches are conjested with highrises!
Give me a break.
What is that being based on?
What floods do we have evidence of that happened 500 years ago in America?
Who was even here to record them?
This is like saying you can do 110 or 120 percent performance when it's only physically possible to have 100 percent. Who is coming up with this nonsense?
Temperature Conversion
Conversion Tools
I do not understand this 100/500 year flood insanity. When we purchase life insurance, it is figured on tables, we all know that. However those selling it just tell us it will cost XXX. Why not the same for flood? I don't need to know the details. Tell me how much and I will make a decision. My husband is a catastrophe adjuster and sees so many people that were told they "didn't need flood insurance" because of the 100/500 flood analysis.
It seems to me that insurance agents talk people out of flood insurance even if they want it. That was my experience when we moved to our current house. My husband said "get flood insurance!" It was a federal case to get our agent to write the policy. He kept saying "you don't need it!" What's up!
is it cat 3 yet ?
Tropical Storm "FRANK" has gained more strength as it continues to move closer to Samar - Leyte Area
Tropical Cyclone Bulletin #6
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At 5:00 A.M. PST, Tropical Storm Frank located near 11.0ºN, 127.4ºE or 180 kms East of Guiuan, Eastern Samar has sustained winds of 60 knots with gusts up to 75 knots.
Storm Signals Raised
====================
Warning Signal #3 (100-185 km/h)
Luzon Region
1.No Signals Raised
Visayas Region
1.Samar Provinces
Mindanao Region
1.No Signal Raised
Warning Signal #2 (60-100 km/h)
Luzon Region
1.Catanduanes
2.Sorsogon
Visayas Region
1.Leyte Provinces
2.Biliran Island
Mindanao Region
1.Dinagat Island
2.Siargao Island
Warning Signal #1 (30-50 km/h)
Luzon Region
1.Camarines Sur
2.Albay
3.Burias Island
4.Masbate
5.Ticao Island
Visayas Region
1.Northern Cebu
2.Bohol
Mindanao Region
1.Surigao del Norte
2.Surigao del Sur
3.Agusan del Norte
4.Camiguin
Residents in low lying areas and near mountain slopes are advised to take all the necessary precautions against possible flashfloods and landslides. Likewise, those living in coastal areas under signal 2 and 3 are alerted against big waves or storm surges generated by this tropical cyclone.
The public and the disaster coordinating councils concerned are advised to take appropriate action and watch for the next bulletin to be issued at 11 a.m. today
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