2011: Year of the flood

If you're not an environmentalist, you're a mass murderer.

http://www.wunderground.com/blog/JeffMasters/comment.html?entrynum=1731

The year 2010 was one the worst years in world history for high-impact floods. But just three weeks into the new year, 2011 has already had an entire year's worth of mega-floods. I'll recap here six remarkable floods that have already occurred this year.

Brazil
Brazil suffered its deadliest natural disaster in history last week, when torrential rains inundated a heavily populated, steep-sloped area about 40 miles north of Rio de Janeiro. Flash floods and mudslides from the heavy rains have claimed at least 772 lives, including 357 in Nova Friburgo and 323 in Teresópolis. The storm left 126 people missing, the Brazilian Health and Civil Defense Ministry said Thursday. Rainfall amounts of approximately 300 mm (12 inches) fell in just a few hours in the hardest-hit regions. Damage estimates are currently $1.2 billion, and 13,000 are homeless.

Australia Queensland
Australia's most expensive natural disaster in history is now the Queensland flood of 2010 - 2011, with a price tag now as high as $30 billion. At least 31 have been killed since December in the floods, and another 40 are missing. According to the Australian Bureau of Meteorology, in 2010 Australia had its wettest spring (September - November) since records began 111 years ago, with some sections of coastal Queensland receiving over 4 feet (1200 mm) of rain. Rainfall in Queensland and all of eastern Australia in December was the greatest on record, and the year 2010 was the rainiest year on record for Queensland.

Australia Victoria
From January 12 - 14, extremely heavy rains over the southern Australian state of Victoria caused major flooding that killed one person and caused hundreds of millions in damage. Kevin Parkyn, a senior forecaster with the Bureau of Meteorology said "Victoria is experiencing one of its worst flood events in its history" after "a week in which rainfall totals have been smashed in parts of Victoria". Bureau of Meteorology senior forecaster Terry Ryan said "It's the worst flood in western Victoria in their history as far as our records go in terms of the depth of water and the number of places affected."

100-year flood in Sri Lanka
As I reported in my previous post, at least 43 are dead and damage estimates are at $500 million in Sri Lanka, which suffered a 1-in-100 year flood this month.

South Africa
Heavy rains of up 345 mm (13.6") have fallen in South Africa so far this month, resulting in deadly floods that have killed 40 people. Seven of the country's nine provinces have been declared disaster zones. Agricultural damage alone from the floods is estimated at $145 million. Heavy rains and severe flooding have also affected neighboring Mozambique, where 13 people are dead and 13,000 homeless or suffering damaged homes. Neighboring Zimbabwe has seen its heaviest rains in 30 years in recent weeks, according to the nation's Civil Protection Unit, but severe flooding has not yet hit that nation.

Philippines
Very heavy rains since late December have triggered a major flooding disaster in the Philippines, where 40 are dead, 453,000 people displaced, and 1.2 million people affected.

Commentary
The year 2011 has begun with a remarkable number of high-impact floods world-wide, and much of the blame for this can be placed on the current La Niña event occurring in the Eastern Pacific. NOAA's Climate Prediction Center currently puts the La Niña event in the "strong" category, and whenever a La Niña or El Niño event reaches the strong category, major perturbations to global weather patterns occur. This typically results in record or near-record flooding in one or more regions of the globe. When one combines the impact of La Niña with the increase of global ocean temperatures of 0.5°C (0.9°F) over the past 50 years, which has put 4% more water vapor into the atmosphere since 1970, the result is a much increased chance of unprecedented floods. A 4% increase in atmospheric moisture may not sound like much, but it turns out that precipitation will increase by about 8% with that 4% moisture increase. Critically, it is the extreme rainfall events that tend to supply the increased rainfall. For example, (Groisman et al., 2004) found a 20% increase in very heavy (top 1%) precipitation events over the U.S. in the past century, and a 36% rise in cold season (October - April) "extreme" precipitation events (those in the 99.9% percentile--1 in 1000 events. These extreme rainfall events are the ones most likely to cause floods.



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