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Anne is a "Strange Quark"

Wow! I won the “strange quark” (2nd place) award in a science writing contest, hosted by Three Quarks Daily, for blogging about the Mississippi River, floods, levees, and the illusion of control.

As I wrote in the comments at 3QD:

Wow! I never thought I’d actually win something for writing about stuff for fun. Thank you to Dr. Lisa Randall for selecting me, the folks at Three Quarks Daily for hosting this contest and boosting me into the finals. I am deeply honored to be a winner of the 3 Quarks Daily contest, and incredibly impressed by the company I’m in.

The 1993 Mississippi River floods were the event that made me become the scientist I am today, so I really wanted to do a creditable job explaining the perspectives and nuances of flood management. Based on the response to the piece, I must have done OK! But now I’ve set myself the goal of bringing that same quality of writing to more blog posts and my scientific papers, so I may be in trouble if they don’t live up to the high praise that this post has gotten.

Thanks to my readers for supporting me in the contest and in blogging generally. Special thanks to my co-blogger Chris for giving me a place to write and for encouraging and supporting me every day.

Flooding around the world (early June edition)

Cross-posted at Highly Allochthonous

Got flood fatigue yet? Too bad, because the wet weather and the high water keeps coming. Here is a quick round up of the notable flood-related news of the week.

High water on the Mississippi River, La Crosse, Wisconsin, 21 April 2011

Front row seats for water levels above flood stage on the Mississippi River, La Crosse, Wisconsin, 21 April 2011

Mississippi River

Floodwall (with emergency height added) in Omaha, Nebraska during the record 1952 floods.

Floodwall (with emergency height added) in Omaha, Nebraska during the record 1952 floods. Will that record be broken this year? (Image from Nebraska DNR.)

Missouri River

Heavy snowpacks in the Missouri River watershed (an areally large, but volumetrically smaller contributor to the Mississippi) have led to near-record flooding that is on-going along its whole length from Montana to Missouri. It’s not getting as much media attention as the Mississippi River, but water levels may stay above flood stage for months. Right now there are heavy rains occurring in parts of the basin, with more rain in the forecast, which will only add to flood problems.

Like the Mississippi, the Missouri is heavily managed by the Corps of Engineers, which is taking some criticism for residents in affected cities. There have also been evacuations because of seepage under levees and concerns about the possibility of failure. Like all big river/developed world flood stories, this one is a complicated mix of huge volumes of water, complicated multi-purpose river management plans, and unwise historical floodplain development.

  • In Historic Flooding On Mississippi River, A Missed Opportunity To Rebuild Louisiana:
    http://www.huffingtonpost.com/2011/06/09/in-historic-flooding-on-m_n_873623.html
  • Flooding from heavy rain in Guizhou province, southwestern China on 6 June 2011 (photo: Xinhua)

    Flooding from heavy rain in Guizhou province, southwestern China on 6 June 2011 (photo: Xinhua)

    China

    For months, China has been stricken by its most intense drought in 60 years, but right now it’s too much, not too little, water that is the problem. Flooding since the 1st of the month has affected East China’s Jiangxi Province and 12 provinces in central and southern China, and more rain is in the forecast for many areas. Intense rains over the last few days have caused the evacuation of more than 100,000 people and killed at least 54.

    Elsewhere

    The Flood Observatory is also reporting on-going flooding in Colombia, the Philippines, Algeria, Haiti and the Dominican Republic, Canada, India, and Upstate New York/Vermont’s Lake Champlain area. In every one of these places, people are losing their homes and lives. While volcanoes and earthquakes shake things up spectacularly now and again, every single day, somewhere in the world, there’s a devastating flood going on.

    Lingering flooding along the Middle Mississippi River and tributaries

    Cross-posted at Highly Allochthonous

    NASA MODIS image of flooding along the Middle Mississippi, 20 May 2011

    Figure 1. NASA MODIS image of flooding along the Middle Mississippi, 20 May 2011.

    One week ago today (28 May 2011), I had the chance to explore the lingering flooding along the Mississippi River and its tributary Big Muddy River in southern Illinois. The area was long past its crest; it is upriver of Cairo and the Birds Point Floodway. Around Carbondale, evidence of the recent high water was still visible in all of the drainages, but the water was back well within the stream banks. Closer to the confluence with the Mississippi though, high water levels on the Mississippi were still forcing backwater flooding of the floodplain and the Big Muddy River.

    Driving and hiking along the escarpment of the LaRue-Pine Research Natural Area afforded expansive views of the flooding – and the remnant landscapes of previous millenia of river activity.

    Foreground: An abandoned channel remains as a wetland. Background: Levees and flooding along the Big Muddy River.

    Figure 2. Foreground: An abandoned channel remains as a wetland. Background: Levees and flooding along the Big Muddy River. (Click for larger version)

    Flooding along the Big Muddy River, 28 May 2011

    Figure 3. Flooding along the Big Muddy River, 28 May 2011 (Click for larger version)

    Once we descended from the hills and onto the floodplain, we were immediately greeted by floodwaters.

    Flooded bottomlands

    Figure 4. Flooded bottomland forest along the Big Muddy River.

    Driving away from the hills towards the Mississippi, our road took us along the top of the levee, giving us close up views of the effects of leveeing, levee repairs, and local wildlife.

    Big Muddy inside the levee

    Figure 5. A barn and fields protected from flooding by the levee on which we drove. (View out the window on the south side of the car.) (This barn is visible in the middle left of Figure 3).

    Big Muddy outside the levee

    Figure 6. The Big Muddy River, in flood, contained by the levee we drove along. (View out the window on the north side of the car, immediately opposite Figure 5.)

    Levee repair along the Big Muddy

    Figure 7. Temporary levee repair along the Big Muddy. The plastic sheeting and sandbags may be covering an area that had cracked or started to erode (click for larger).


    Snapping turtle

    Figure 8. Why did the snapping turtle cross the levee road?

    After crossing the Big Muddy River, we drove along a state highway that was not atop a levee, and only a few feet above flooded fields. Egrets and herons were everywhere in the standing water, and a pleasant breeze whipped up waves on the water. But we were reminded that this scene was normally not so watery…in the image below, you might be able to see a center pivot irrigation line in the field, standing in the flood waters.

    Flooded fields and an irrigation line

    Figure 9. A flooded field, with an irrigation line. Normally, this landscape would not be so blue. (Click for larger)

    Finally we reached the Mississippi itself, in Grand Tower, Illinois. The river was definitely high, but open for business – we watched a tow and barges go by. The town of Grand Tower is situated immediately adjacent to the Mississippi – and protected by a big levee. Near the north end of town, the levee was a few feet lower than the rest, and here a metal floodwall had been constructed atop the levee. There was also evidence that a pumping operation had been set up – to pump water from behind the levee back into the river. Whether this pumping was necessitated by seepage or localized ponding, I couldn’t tell. But here, in a sleepy little town on the Mississippi, the effects of our efforts to keep floodwaters off the floodplain were in full display.

    Pumping set up and a floodwall atop a levee

    Figure 10. A pumping and a floodwall atop a levee (on right side of photo) in Grand Tower, Illinois.


    Mississippi River flooding, Grand Tower, Illinois

    Figure 11. Mississippi River flooding, Grand Tower, Illinois. Looking downstream, with a levee on the left side of the image.

    Anne in the news

    Flooding along the Mississippi River
    Last week, I wrote a post for the Scientific American Guest Blog on “Levees and the Illusion of Flood Control,” about the ways that while levees around individual communities may be good, the systematic leveeing of entire waterways is a bad long-term strategy. On Friday, that post was also featured on the front page of ScientificAmerican.com on their Science Agenda. (I’ll add a screenshot if I can dig it back up.)

    Linkages between climate change and severe weather
    This morning my name may be in your local newspaper, as I’m quoted in an article about how this spring’s severe weather (including flooding along the Mississippi) fits with scientific expectations about climate change. The article was written by the McClatchey syndicate and versions of it may appear in multiple newspapers. For example, here’s the Charlotte Observer’s version of the story.

    Flooding along the Mississippi River

    Cross-posted at Highly Allochthonous

    In case other events have crowded it out of your news feed, there’s record-breaking flooding going on in the Mississippi River basin. Snowmelt in the headwaters, combined with weeks of heavy rains in the middle reaches of the river basin, have pushed the system to its engineered limits. The Mississippi River basin is home to more than 100 million people, and when the water flows past Natchez, it’s carrying flow from 41% of the contiguous United States, making it the third largest river basin in the world. The volume of water carried by the Mississippi River in flood can be measured in the same unit as ocean currents — within the next few days, the Mississippi River at Natchez will be flowing more than 2 Million cubic feet per second.

    Flooding at the junction of the Mississippi and Ohio Rivers, 3 May 2011, NASA image

    Flooding at the junction of the Mississippi and Ohio Rivers, 3 May 2011, NASA image

    Start here

    For hands-down the best analysis on the flooding, the engineering, the politics, and the media coverage of the flooding, you need to turn to Steve Gough’s Riparian Rap blog. Go there now to get caught up. Then when you want some other perspective, check out the links and resources below.

    General information on the flooding

    Floodways doing what they were designed to do

    Edge of the inflow section, Bird's Point floodway. image by the US Army Corps of Engineers

    Edge of the inflow section, Bird's Point floodway. image by the US Army Corps of Engineers


    Early in the week the big Mississippi news story was on the opening of the Bird’s Point Floodway in Missouri. Media reports tended to focus on the sensationalist “us vs. them” people stories, with most of the stories completely missing the fact that the floodway was designed for this purposes and residents in it had known about and been compensated for its existence. Steve Gough had great coverage, including this piece.

    The next big to-do will be over opening the Morganza floodway in Louisiana, expected to happen on Thursday 12 May. So far, the news media seems to be taking a bit more reasonable perspective here, but I expect there will be hysterical stories as well. My two cents: Based on experience with devastating past Mississippi River floods, our national policy has been to design and designate floodways to relieve pressure on levees on the mainstem of the Mississippi River. This means that some people miles from the main river will lose homes and property (and have been compensated for that risk), but it is for the benefit of much larger populations. Further, the areas that lie in floodways are part of the natural floodplain of the Mississippi River, and they would flood much more frequently without the levees.

    More information on Bird’s Point and Morganza floodways can be found below.

    Background Reading

    1927 Mississippi River flooding, image from the Library of Congress

    1927 Mississippi River flooding, image from the Library of Congress


    The best general background information on floods and flood control on the Mississippi River can be found in John M. Barry’s book “Rising Tide: The Great Mississippi River Flood of 1927 and how it Changed America” and John McPhee’s essay on the Old River Control Structure in The Control of Nature, available on-line through The New Yorker.

    Floodwaters rising on the Red River

    Cross posted at Highly Allochthonous

    Fargo, North Dakota is coming out of its 3rd snowiest winter since 1885. Snow continued to fall into late March, and daytime temperatures have only been above freezing for few weeks. At night, it’s still below freezing, though starting tomorrow night the forecast calls for above freezing minimum temperatures. Soils are already saturated, and more rain is possible this weekend.

    In short, it is perfect flood weather for the Red River that runs along the Minnesota-North Dakota border and into Canada. This is a place with the perfect geography for extensive flooding, and a long history of big spring floods.

    Checking the water level on a bridge between Fargo and Moorhead. Photo from Minnesota Public Radio.

    Checking the water level on a bridge between Fargo and Moorhead. Photo from Minnesota Public Radio.

    Every town along the Red River has been devastated by a flood more than once. So they’ve all got emergency response plans in place for weather just like this. For example, Moorhead (Minnesota, across the river from Fargo) has a nifty GIS feature that shows how each foot of flood water affects each city block.

    Residents are already filling sand-bags to build temporary levees. But with year after year of flooding, and with successful sand bag efforts the last two years, some residents might be taking this year’s flood predictions in a somewhat complacent fashion. But looking at the National Weather Service’s North Central River Forecast Center projections, there’s plenty of reason for concern all along the Red River.

    As of 9 am Central time on 7 April 2011, most of the US portion of the Red River is already above flood stage, but water levels will continue to rise almost everywhere for at least the next week.

    Flood stages as of 9 am 7 April 2011. Screen grab from NCRFC.

    Current flood levels along the Red River and nearby drainages, as of 9 am, Thursday 7 April 2011. Orange circles indicate minor flooding, red indicates moderate flooding, purple indicates major flooding. Screenshot from the North Central River Forecast Center, using data supplied by the USGS.

    The flood wave will move downstream – from south to north. In Wahpeton, a crest is expected today, with a second – equally high if not higher – crest next week. There the flood crest is likely to fall a few feet short of record water levels set in 1997.

    Between Wahpeton and Fargo, tributaries to the Red River are having major flooding as well – in part because of backwater effects from the main river. If the Red River is flooding, there’s no place for water flowing down the tributaries to go. Instead they back up, causing even more widespread flooding.

    In Fargo (ND) and Moorhead (MN) – which have a combined population of 200,000 people – the flood will not crest until late Sunday. Right now, the National Weather Service is predicting a crest of 39.5 feet, which 1.3 feet short of the record flooding of 2009. However, there some chance that the river will crest at 41 feet, or even higher if there is precipitation in the next few days. Currently, 80% of the city is protected by sand bags and levees to a height of 41 feet, but those may need to go even higher.

    NWS Flood Forecast for Fargo, North Dakota (7 April 2011)

    NWS Flood Forecast for Fargo, North Dakota (7 April 2011)

    Two weeks ago, the National Weather Service issued a longer-term flood forecast for the Red River at Fargo. At that time they considered it a 10-50% percent chance that the river would reach 40 to 44.3 feet by mid-April. They provided a probability of exceedence curve for their modeled projections of this year’s flood season against the historical record of flooding, as shown below. To understand this graph, it helps to look at a few specific points. Right now, the river is at 35.32 feet. Based on the outlook from two weeks ago, it was virtually inevitable that the river would reach this level, with a probability greater than 98%, as shown by the black triangles. In contrast, 35.32 feet is reached less than 5% of the years in the historical record for Fargo, as shown by the blue circles. The current projected crest of 39.5 feet was given about a 50% chance of being exceeded as of two weeks ago, yet it has only be reached twice (1997, 2009) in 111 years of record. Two weeks ago, the National Weather Service was saying that there was a 25% chance the river could go above 42 feet, which is higher than the top of the sand bag levees now being prepared.

    NWS Chance of exceeding river levels on the Red River at Fargo, conditional simulation based on current conditions as of March 24, 2011

    NC River Forecast Center's 90 model showing the Red River at Fargo's chances of exceeding certain water levels, relative to the historical record.

    The short term forecasts, like the one two above, have better skill than long term forecasts like the immediately above, but the long term forecasts are vital for emergency managers, city officials, and riverside land-owners in making early plans for the flood. The reason they’ve got all the sand and sand bags on hand in places like Fargo is because they knew there was a good chance a really big flood was coming. They’ve been talking about it since January.

    Downstream (north) of Fargo-Moorhead lies Grand Forks, with about 100,000 people in its metropolitan area. Grand Forks was swamped by the flood of 1997, but the current forecasted peak stage this year is about 3.5 feet lower, though the crest won’t reach Grand Forks until late next week. For now, they are watching the water levels and making their preparations. Downstream further, lies Winnipeg, Manitoba. The flood crest won’t reach there until late April, but already the river is 17 feet above normal winter stage, and only 5 feet below the 2009 flood peak. Needless to say, they too are sand-bagging.

    But for the next few days, the action focuses on the Fargo-Moorhead area. You can check out the updated data and forecasts or you can watch the flood play out in Moorhead with a live webcam pointed at the downtown waterfront:
    http://www.justin.tv/widgets/live_embed_player.swfWatch live video from 702 Flood Cam – Moorhead on Justin.tv

    A continental divide that runs through a valley

    Now that’s pathological.

    Parts of the Upper Midwest are disappearing under spring floods. The Red River of the North is at major flood stage, again, and the Minnesota River flood crest is moving downstream. It’s a pretty frequent occurrence in both of these river systems, and in part, flooding is a legacy of the glacial history of the area. The Red River flows to the north along the lake bed of Glacial Lake Agassiz, which is pathologically flat. The Minnesota River flows to the south along the channel of the Glacial River Warren, which was gouged out of the landscape by water draining from Lake Agassiz.

    14,000 years ago there was direct connection between what is now the Red River basin and the Minnesota River basin. Today, there’s a continental divide – with the Red flowing toward Hudson Bay and the Minnesota flowing toward the Mississippi and Gulf of Mexico. But what a strange continental divide it is – for it runs through the former outlet of Lake Agassiz, in what is now known as Brown’s Valley or the Traverse Gap. This divide is not so much a high point in the landscape, but a just-not-quite-as-low area. The little community of Brown’s Valley sits between Lake Traverse (flows to the North, forming the headwaters of the Red) and Big Stone Lake (flows to the south, forming the headwaters of the Minnesota).

    Here’s what it looks like on Google Earth. Note that I’ve set the terrain to 3x vertical exaggeration, so that you have some hope of seeing the subtle topography of this area.

    Croppercapture12

    And here’s a very, very cool oblique photo from Wikipedia. It shows the divide looking from north to south — mostly covered by floodwaters in 2007. It’s not every day you get to see a continental divide covered in water.

    800px-browns_valley_flood_07

    Why does the Red River of the North have so many floods?

    Cross-posted at Highly Allochthonous

    Communities along the Minnesota-North Dakota border are watching the water levels, listening to the weather forecasts, and preparing for another season of flooding. It must be a disconcertingly familiar routine, as this will be the third year in a row in which the Red River of the North reaches major flooding levels. But this isn’t merely a run of bad luck for residents in the Red River Valley, major floods are to be expected in a place with an unfortunate combination of extremely low relief and a river at the whim of snowmelt and ice jams.

    The Red River of the North begins in Minnesota, near the border with North and South Dakota, and it flows northward through Fargo/Moorhead, Grand Forks, and Winnipeg before emptying into Lake Winnipeg, Manitoba. The landscape around the Red River is excruciatingly flat (Figure 1), for the Red River Valley isn’t a stream-formed feature at all, but is the remnant landscape of Glacial Lake Agassiz, which held meltwaters from the Laurentide Ice Sheet for more than 5000 years. The modern Red River has barely managed to incise into this flat, flat surface, because it slopes only very gently to the north (~17 cm/km). Instead, the river tightly meanders across the old lake bed, slowly carrying its water to the north. Topographically, this is a pretty bad setting for a flood, because floodwaters spread out over large areas and take a long time to drain away.

    Topography of the US portion of the Red River Valley from SRTM data as displayed by NASA's Earth Observatoryredriver_srtm_palette

    Figure 1. Topography of the US portion of the Red River Valley from SRTM data as displayed by NASA's Earth Observatory

    The climate of the Red River watershed makes it prone to flooding during the spring, usually peaking in about mid-April. The area receives about 1 m of snow between October and May, and the river freezes over. In late March to early April, the temperatures generally rise above freezing, triggering the start of snowmelt. Temperatures warm soonest in the southern, upstream end of the watershed and they get above freezing the latest near the mouth of the river. This means that snowmelt drains into the river’s upper reaches while downstream the river is still frozen, impeding flow (Figure 2). As the ice goes out, jams can temporarily occur and dam or back up the river, exacerbating local flooding problems.

    Red River near Oslo, Minnesota, 3 April 2009, photo by David Willis

    Figure 2. Red River near Oslo, Minnesota, 3 April 2009. Here the main river channel is still clogged with ice, while surrounding farmland is underwater. Photo by David Willis of http://www.cropnet.com/.

    Together the topography and climate of the Red River watershed are a recipe for large-scale flooding, and the historical record shows that floods are a frequent occurrence on the river. Usually, hydrologists talk about rivers in terms of their flow, or discharge, which is the volume of water per second that passes a point. But, when talking about floods like those on the Red River, it’s not so much volume that matters as how high the water rises (“stage”). The National Weather Service is responsible for flood prediction in the US, and they define flood stage as “the stage at which overflow of the natural streambanks begins to cause damage in the reach in which the elevation is measured.” If the water level continues to rise, “moderate flooding” occurs when “some inundation of structures and roads near streams. Some evacuations of people and/or transfer of property to higher elevations are necessary.” Further increases in water levels can bring a river to “major flooding“, when “extensive inundation of structures and roads. Significant evacuations of people and/or transfer of property to higher elevations.” That’s the sort of flooding that will happen in places along the Red River this spring, as it has many springs in the historical record (Figure 3).

    Annual peak stage on the Red River at Grand Forks, North Dakota

    Figure 3. Annual peak stage on the Red River at Grand Forks, North Dakota. Data replotted from the USGS, with local NWS flood stages shown.

    Already, flood warnings are being issued for the Red River and its tributaries. As I’ll discuss in my next post, the long-range forecast for this spring’s floods on the Red is looking pretty grim. But as the communities along the river brace for the on-coming flood, it is important to remember that the geology and climate of the region make repeated major floods inevitable.

    Pakistan floods: Predicted or Predictable, but a disaster nonetheless

    Cross-posted at Highly Allochthonous

    ResearchBlogging.org

    Unusually heavy monsoon rains in July and August 2010 left large swaths of Pakistan underwater. At least 18 million people were affected by the flood, and it is estimated that, more than six months later, several hundred thousand remain without even temporary shelter. As a result of lost crops and livelihoods from the flood and inadequate relief supplies, malnutrition continues to kill people. Like most floods, the Pakistani poor have suffered far more than those with resources to avoid the flood, or at least its aftermath.

    Remains of a school destroyed by flooding, near Jacobabad by DFID - UK Department for International Development, on Flickr

    Remains of a school destroyed by flooding, near Jacobabad by UK Department for International Development, on Flickr. Used under a Creative Commons license.

    A paper in press in Geophysical Research Letters shows that the 2010 floods were extraordinary. Monsoonal rains tend to occur in pulses, with multi-day wet periods followed by multi-day dry periods, and while the total rainfall over Pakistan during the 2010 monsoon season was not unprecedented, the number and intensity of extremely heavy rains over northern Pakistan was very unusual. The authors are working with very limited historical and satellite data, but they estimate that the number of intense rain bursts that occurred in 2010 had a probability of less than 3% in any given year.

    Using data from the European Centre for Medium Range Weather Forecasts collection of meteorological models, the authors of the new paper show that the timing and intensity of northern Pakistan’s monsoon rain bursts are predictable up to 6 to 8 days in advance – including the rains that caused the flooding in 2010.

    Lead author, Peter Webster, and his coauthors from the Georgia Institute of Technology, draw the following conclusion from their analysis:

    We conclude that if these extended quantitative precipitation forecasts had been available in Pakistan, the high risk of flooding could have been foreseen. If these rainfall forecasts had been coupled to a hydrological model then the high risk of extensive and prolonged flooding could have anticipated and actions taken to mitigate their impact.

    The floods really kicked off with a burst of rain on 28-29 July 2010, and according to Webster’s reanalysis, that rainfall was predictable with good skill 7 days in advance (21 July). Webster and colleagues argue that if that forecast was available in Pakistan, lives would have been saved and the immensity of the disaster reduced. But, C. Christine Fair, writing on the Foreign Policy magazine website suggests that the flood was forecast in Pakistan.

    In the middle of July, the PMD began tracking a storm brewing in the Bay of Bengal. This eastern weather system developed interactively with a western weather system to produce the massive rains and the subsequent super flood of 2010. On July 24, the PMD issued a flood warning to the provincial government of Khyber-Pakhtunkhwa (KPK). Despite these increasingly severe warnings, KPK’s citizenry did not believe them. … The PMD kept issuing warnings to KPK as the rains began to fall. However, as fate would have it, on July 28, … a passenger jet coming to Islamabad from Karachi crashed …With the media beset upon this tragic spectacle, the PMD’s warnings went unheeded as the rain began to fall.

    So the Pakistani government did forecast the flood – at least four days out – in plenty of time to get people in northern Pakistan’s valleys out of the way. The problem was not with the meteorological and hydrologic science either internationally or in Pakistan. Instead, disaster was ensured when flood warnings were not taken sufficiently seriously by regional authorities, media, and residents.

    Why wouldn’t flood warnings be heeded? Perhaps more could have been done to communicate to Pakistanis through channels whose authority they respected. Webster cites an example of flood warnings in Bangladesh being disseminated by imams at local mosques. The Foreign Policy article quoted above places some blame on media distractedness.

    But there was also a more insidious reason the forecasted flood was ignored. It was a rare event, but it was also part of a new climatic pattern for Pakistan. As the Foreign Policy article describes it:

    in recent years there has been a slow but steady change in the location where Pakistan’s major rainfalls concentrate. In the past, monsoon rains fell most intensely over the Punjab. Slowly and steadily, the concentration of rainfall has moved north and west to KPK. This redistribution of concentrated rainfall away from the Punjab and towards KPK explains why no one in KPK had any reason to believe the predicted weather.

    Flooding frequency and intensity have increased in Pakistan in the last 30-40 years compared to earlier in the 20th century. Webster and coauthors state, “This recent increase is consistent with the increase in intensity of the global monsoon accompanying the last three decades of general global warming.” The flood warnings were ignored, in part, because the statistics of monsoon rain patterns are changing. Human memory and historical records are not good guidance if the weather system is changing. In situations like this one, the past is not the key to the present.

    There are lots of things that should have been improved to lessen the magnitude of the Pakistani flood disaster – reservoir management should have been altered; emergency relief supplies should have been distributed more equitably, broadly, and consistently; international assistance should have been much more generous – but the two big lessons for hazard mitigation coming out of the Pakistan floods seem to be: “find a system for making sure that warnings are issued and that they actually make it to people in harm’s way” and “don’t assume the climate of living memory is a very good indicator of the weather of the present and future.”

    Webster, P. J., Toma, V.E., & Kim, H.-M. (2011). Were the 2010 Pakistan floods predictable? Geophysical Research Letters : 10.1029/2010GL046346

    Flooding around the world

    Cross-posted at Highly Allochthonous

    Based on information from The Flood Observatory and other news sources, here are some tidbits about on-going and recent flood events around the world. Every one of these floods is having significant local and regional impacts, even if they don’t make the international news circuit. Common threads amongst these floods are the impact of the La Nina climate pattern and the unequal distribution of flood risks across the economic spectrum.

    New Zealand

    Cyclone Wilma hit the northern end of New Zealand’s North Island on Friday and Saturday 28-29 January, bringing with it intense rains, flooding, and landslides. Wilma unleashed about 28 cm of precipitation in just 12-14 hours, resulting in damage to homes, roads, and water and sewer treatment infrastructure. This was the fourth tropical low to impact New Zealand in just three weeks. The New Zealand Herald has a nice collection of reader-submitted images showing flooding and damage in various areas. My particular favorites are this flooded river valley and this road closed by a landslide. The New Zealand National Institute of Water and Atmospheric Research (NIWA) provides near real-time hydrologic, sea level, and climatic data through their Environmental Data Explorer, so I can show you quantitatively what this cyclone meant for a couple of rivers.

    Mangakahi River at Gorge stream discharge data from NIWA

    Mangakahi River at Gorge stream discharge data from NIWA

    Waitangi River at Wakelins stream discharge data from NIWA

    Waitangi River at Wakelins stream discharge data from NIWA

    While the graphs above show discharge (flow volume per time), which is the unit of currency for hydrologists who want to compare multiple rivers to each other, local flooding impacts depend also on the depth(or stage) of the water. For reference, the Waitangi River goes from ~0.4 m before the storm to 6.2 m at the end of the record shown above. If you click through to this image on the New Zealand Herald website, you’ll see why the record for the Waitangi River ends when it does. That gaging station wasn’t meant for those flow conditions.

    Australia

    While Queensland begins to tally its losses and recover from massive flooding earlier this month, tropical cyclones aren’t about to make the job any easier. Cyclone Anthony brought mostly heavy winds to the Queensland coast south of Townsville Sunday night, and damage is reported to be minimal. But much bigger and much stronger Cyclone Yasi is expected to make landfall in the same area as a Category 4 storm later this week. This cyclone is expected to produce widespread, heavy rain, a strong storm surge along the coast, and winds up to 260 km per hour.

    Meanwhile, in the southeastern state of Victoria, tributaries to the Murray River are also flooding. These floodwaters are still rising and are expected to take weeks to months to recede. Increasing my sympathy for the Australians, Victoria and South Australia are also experiencing a ridiculous heat wave, with temperatures reaching or exceeding 40 C for several days in a row.

    Saudia Arabia

    Flooding occurred around the city of Jeddah over the weekend, killing at least 10 people. Three hours of rain produced 11 cm of precipitation, cars were washed away, and the video below shows the failure of a dam, which the videographer says contained a lake used for dumping untreated sewage.

    [youtube=http://www.youtube.com/watch?v=iiW1ChsOhSs&w=640&h=510]

    South Africa

    Flooding in South Africa has gotten almost no international attention, despite the fact that floods have killed 120 people there and have caused disaster declarations in 8 of 9 provinces. Flooding has also affected Mozambique, where 13 people have died, and forecasts for continued heavy rains over the next several months have much of the southern part of the continent on alert. In some areas, up to 10 times as much rain as normal has fallen in the month of January. Tens of thousands of homes have been destroyed. Many of the lost homes are shacks belonging to poor Africans, because informal settlements are often located in low lying areas.

    Brazil

    The clouds have cleared over the area around Rio that was hard-hit by floods and landsliding earlier this month. The death toll now exceeds 840 people, and the Brazilian federal and state governments have promised to provide up to 8000 homes for people that lost theirs in the disaster. The government also plans to immediately begin increasing its disaster preparedness, including mapping of high risk areas and better weather data collection. Dave Petley did a great analysis using before and after aerial imagery in one of the slide-affected area.