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Tag Archive: flooding

  1. Timing is key in keeping organic matter in wet cropland soils, new study finds

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    • Periodically flooded soils may actually lose organic matter at accelerated rate, a new report suggests.

    November 24, 2017 Iowa State University read full ScienceDaily article here

    ..The study found that timing plays a key role in how well wet soils retain organic matter. While soils with consistently high moisture content do retain organic matter over the long term, soils may actually lose organic matter during shorter spans of flooding. The findings have implications for agricultural fields that are poorly drained or flood for a few weeks of the year before drying out, Hall said. The study also shows that wetlands, thought of as a useful tool for conservation and carbon sequestration, may require consistent flooding to realize environmental benefits from organic matter accumulation….

    …”We found that periodically wet soils don’t necessarily protect organic matter from decomposition and may lead to losses, at least over a timescale of weeks to months,” he said.

    The study drew on research conducted in an ISU laboratory. The researchers took soil samples from a central Iowa cornfield and subjected the sample to various conditions before conducting chemical analyses.

    Hall said future research should widen in scope and include field experiments as well as laboratory-based work. He said he wants to test how various drainage techniques influence organic matter loss as well as pinpoint the length of time required for wet soil to realize environmental benefits….

    Wenjuan Huang, Steven J. Hall. Elevated moisture stimulates carbon loss from mineral soils by releasing protected organic matter. Nature Communications, 2017; 8 (1) DOI: 10.1038/s41467-017-01998-z

  2. A massive storm flooded Houston. Experts say California’s state capital could be next.

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    • Sacramento is more vulnerable to catastrophic flooding than any other major city in the United States except New Orleans, according to federal officials, a threat created by the city’s sunken geography.

    October 29 2017 see full Washington Post article here

    …Models show a levee failure could submerge parts of this inland metropolis [Sacramento] under as much as 20 feet of water. As Northern Californians are recovering from wildfires and sifting through homes reduced to ash, officials in the state’s capital are struggling to prevent another type of natural disaster….

    …Levees and other flood defenses here and in the surrounding Central Valley have amassed up to $21 billion in needed repairs and upgrades, while Sacramento’s population has continued to grow. Just days before Hurricane Harvey slammed into Texas and flooded Houston, a report from the California Department of Water Resources warned that “many flood facilities” in the Central Valley “face an unacceptably high chance of failure.”…

    ….If a levee were to break along the American River, which empties into the Sacramento River near downtown, water would start flowing into the city.

    Although floodgates could be quickly deployed to protect downtown Sacramento from a life-threatening deluge, the water would eventually seep in from other directions, covering much of the area in several feet of water, said Roger Ince, a Sacramento emergency coordinator.

    The water would continue flowing south and deposit more than 20 feet of water in the Pocket neighborhood, where about 20,000 people live in one- and two-story homes….

    ….In a 2010 report called “Overview of the ARkStorm Scenario,” more than two dozen scientists concluded that two back-to-back storms of similar strength could slam into California and submerge 25 percent of the state underwater.

    “This isn’t science fiction,” said one of the authors, Keith Porter, a research professor at the University of Colorado at Boulder. “It’s a very realistic scenario, and it could happen at any time.”

    Jeffrey Mount, a senior fellow and water resources specialist at the Public Policy Institute of California, said such projections raise serious questions about continued development in California’s flood plain, a debate that has been playing out in Sacramento’s Natomas neighborhood, where thousands of new homes are planned…

  3. Forest grazing counteracts the effectiveness of trees to reduce flood risk

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    • Planting trees can reduce flood risk, but a high intensity forest land use, such as grazing, can counteract the positive effect
    • Infiltration rates were between ten and a hundred times higher under trees, when the forested area remained relatively undisturbed, compared with adjacent pasture
    • Forest buffer zones, with restricted access, strategically placed to intercept surface runoff before it reaches the stream may be more effective than larger scale planting when the forested areas are used for other purposes

    October 10, 2017 Lancaster University read full ScienceDaily article here

    As the frequency and severity of flooding becomes an increasing problem, land managers are turning to natural flood management measures, such as tree planting, to reduce the risk. When rainfall exceeds the rate at which water can enter the soil it flows rapidly over the land’s surface into streams and rivers. Trees can help to reduce the risk of surface runoff by increasing the number of large pores in the soil through which water can drain more easily. Land use, such as grazing, also affects the soil’s ability to absorb water; however, while the effect of land use on surface runoff has been well studied in grasslands, little is known about the effect of land use in forests.

    …Researchers found that infiltration rates were between ten and a hundred times higher under trees, when the forested area remained relatively undisturbed, compared with adjacent pasture. Where sheep were allowed to graze under the trees there was no observable difference from the pasture.

    They also compared forest types — conifer forest planted with Scots Pine and broadleaved forest planted with sycamore — and found that infiltration rates were significantly higher under Scots Pine than under sycamore, but only when the forest was ungrazed…

    …”Tree planting can make an important contribution to flood risk management, but forest buffer zones, with restricted access, strategically placed to intercept surface runoff before it reaches the stream may be more effective than larger scale planting when the forested areas are used for other purposes.”…

    K.R.Chandler, C.J.Stevens, A.Binley, A.M.Keith. Influence of tree species and forest land use on soil hydraulic conductivity and implications for surface runoff generation. Geoderma, 2017 DOI: 10.1016/j.geoderma.2017.08.011

  4. What would an entirely flood-proof city look like? From China to New Jersey

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    • As the recent floods from Bangladesh to Texas show, it’s not just the unprecedented magnitude of storms that can cause disaster: it’s urbanisation.
    • From sponge cities in China to ‘berms with benefits’ in New Jersey and floating container classrooms in the slums of Dhaka, we look at a range of projects that treat storm water as a resource rather than a hazard.

    by Sophie Knight Sept. 25 2017 read full GuardianUK article here

    They call it “pave, pipe, and pump”: the mentality that has dominated urban development for over a century. Along with the explosion of the motorcar in the early 20th century came paved surfaces. Rainwater – instead of being sucked up by plants, evaporating, or filtering through the ground back to rivers and lakes – was suddenly forced to slide over pavements and roads into drains, pipes and sewers. Their maximum capacities are based on scenarios such as 10-year storms. And once they clog, the water – with nowhere else to go – simply rises.

    The reality of climate change and more frequent and intense downpours has exposed the hubris of this approach. As the recent floods from Bangladesh to Texas show, it’s not just the unprecedented magnitude of storms that can cause disaster: it’s urbanisation.

    …With climate change both a reality and threat, many architects and urbanists are pushing creative initiatives for cities that treat stormwater as a resource, rather than a hazard….

    …In China, the government has commissioned the construction of 16 “Sponge Cities” to pilot solutions for the freshwater scarcity and flooding suffered in many cities as a result of rapid urbanisation. Chicago architectural firm UrbanLab was commissioned to design the masterplan for Yangming Archipelago in Hunan province: a new centre within the larger city of Changde, devised as a “new model for the future”.

    The area, a low-lying land river basin that experiences heavy rainfall, is regularly flooded. Instead of incorporating defences against water, UrbanLab put space for it to flow at the centre of its urban plan, putting major buildings on islands in an enormous central lake. Canal-lined streets that UrbanLab call “Eco-boulevards” connect the eight districts – the process is visualised in this video.

    UrbanLab says their vision combines a dense metropolis with a nature setting: “As a functional center, Yangming Archipelago will serve as an urban model, we expect it to lead the way to a new way of thinking about the city of the future.”

    The two-mile Pilsen Sustainable Street, commissioned by the Chicago Department of Transportation to improve the urban ecosystemPermeable pavements: Chicago’s ‘green alleys’

     

    The bioswale, an environmentally-friendly form of drainage through landscape, at the Pilsen Sustainable Street on Cermak Rd.
    Bioswale along cermak road
    • Rainwater travels through the self-cleaning, pollution-reducing sidewalk before going on to feed surrounding plants…

    …In New Jersey and New York…in response to Sandy, ZUS partnered with MIT’s Center for Advanced Urbanism and De Urbanisten to devise New Meadowlands: a masterplan for combining flood resilience with recreational amenities through marshes and a system of parallel raised banks called berms.

    Between the outer berm and the sea, the restored wetlands would soak up seawater and slow down tidal waves, preventing them from hitting the dikes at high speed. The stretch of berms would serve as a wildlife refuge, filling up with rainwater during periods of heavy rain before draining out. And on the insider of the inner berm, ditches and ponds would retain rainwater, preventing it from causing sewers to overflow….

    A terrace in Little Ferry, one of the first sites for the pilot project of New MeadowlandsBerms with benefits

     

    Floating pods – and beyond…

    Waterstudio’s Floating City Apps in a slum
  5. ‘Horizontal hurricanes’ – atmospheric rivers pose extreme storm risk but also drought-busting opportunity for California; plans for new 2-3 week forecast and ranking system similar to hurricanes

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    • Severe atmospheric rivers in California could mean 23 days of rain and wind  causing floods and landslides to the tune of $300 billion in property damage per past USGS modeling
    • Atmopheric rivers — while carrying the potential for more damage — will also help California maintain typical rainfall levels amid a drying climate.
    • plan to begin publishing regular 14-day to 21-day outlooks on atmospheric rivers as soon as this winter along with new rating system for intensity on a scale of 1 to 5, similar to hurricanes.

    By Kurtis Alexander September 27, 2017 read full SF Chronicle article here

    …California is facing its own threat of bigger and more destructive storms. Mounting research, much of it done in the wake of the near-record rains that pulled California out of a five-year drought this past winter, shows that seasonal soakers may not come as often as they used to, but could pack more punch when they do arrive.

    ….The massive weather systems that rise out of the Pacific Ocean, now popularly called atmospheric rivers, can drop as much water as Hurricane Irma dumped on Florida this month — billions of gallons that submerged cities and towns.

    …U.S. Geological Survey ran a simulation of what a sequence of severe atmospheric rivers might look like in California…. 23 days of rain and wind that caused floods and landslides to the tune of $300 billion in property damage….big drenchers earlier this year…caused mass flooding in San Jose and other cities and triggered a near-catastrophe at Lake Oroville when a pair of dam spillways failed.

    …A group of Southern California scientists, some of whom are partnering with Sonoma County, plan to begin publishing regular 14-day to 21-day outlooks on atmospheric rivers as soon as this winter. Current forecasts typically don’t anticipate the events more than a week out.

    …Marty Ralph, director of the Center for Western Weather and Water Extremes at UC San Diego’s Scripps Institution of Oceanography, is also working to develop a rating system for the storms.  The blasts will be evaluated for intensity on a scale of 1 to 5, similar to hurricanes. A test run of the ratings last winter pegged the strong atmospheric river in February, which contributed to the damage at Oroville Dam, as a category 5 eventResearch published in the journal Geophysical Research Letters in August, which Ralph participated in, indicates that atmospheric rivers are carrying increasing amounts of water.

    …Sometimes called horizontal hurricanes, atmospheric rivers are exactly what they sound like: airborne channels of water that develop over the Pacific Ocean and are pushed along by strong winds toward the West Coast during the winter….providing as much as 50 percent of the state’s annual rainfall in a matter of days — dumpings that are critical to water supplies but, at times, bring on disaster…

    Another study [published in September] in the journal Scientific Reports, suggests that the swelling intensity of atmospheric rivers — while carrying the potential for more damage — will also help California maintain typical rainfall levels amid a drying climate….

    During the height of the drought, California went as long as a year without seeing a single atmospheric river. But the state was hit by more than 30 of the systems last winter, according to Scripps researchers. That explains why the season was one of the wettest on record….

    Alexander Gershunov, Tamara Shulgina, F. Martin Ralph, David A. Lavers, Jonathan J. Rutz. Assessing the climate-scale variability of atmospheric rivers affecting western North America. Geophysical Research Letters. Volume 44, Issue 15 16 August 2017. Pages 7900–7908 DOI: 10.1002/2017GL074175

  6. Cartoons- climate change, flooding

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    http://www.gocomics.com/mattdavies/2017/08/31

    http://www.gocomics.com/nickanderson/2017/09/01

    cartoon

    http://www.philly.com/philly/opinion/signe/20170830_Daily_Signe_Cartoon_08_30_17.html

    http://www.gocomics.com/joelpett/2017/08/26

    http://www.gocomics.com/claybennett/2017/08/30

  7. Houston’s flooding shows what happens when you ignore science and let developers run rampant

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    • The watershed of the White Oak Bayou river, which includes much of northwest Houston, is a case in point. From 1992 to 2010, this area lost more than 70% of its wetlands, according to research (pdf) by Texas A&M University.
    • The vanished wetlands wouldn’t have prevented flooding, but they would have made it less painful, experts say.
    • Wet land needs wetlands….Prairies, which also act as floodwater sponges, have been decimated too.

    Since Houston, Texas was founded nearly two centuries ago, Houstonians have been treating its wetlands as stinky, mosquito-infested blots in need of drainage.

    Even after it became a widely accepted scientific fact that wetlands can soak up large amounts of flood water, the city continued to pave over them. The watershed of the White Oak Bayou river, which includes much of northwest Houston, is a case in point. From 1992 to 2010, this area lost more than 70% of its wetlands, according to research (pdf) by Texas A&M University.

    In the false-color satellite images below, plants and other vegetation appear green, while urbanized and developed areas appear blue and purple. Drag the slider to see how northwest Houston has changed since 1986.

    ….In recent days, the flooding caused by Hurricane Harvey has raised water levels in some parts of the watershed high enough to completely cover a Cadillac. The vanished wetlands wouldn’t have prevented flooding, but they would have made it less painful, experts say….

    ….Between 1992 and 2010 alone nearly 25,000 acres (about 10,000 hectares) of natural wetland infrastructure was wiped out, the Texas A&M research shows. Most of the losses were in Harris County, where almost 30% of wetlands disappeared.

    Altogether, the region lost the ability to handle nearly four billion gallons (15 billion liters) of storm water. That’s equivalent to $600 million worth of flood water detention capacity, according to the university researchers’ calculations.

    To be sure, that’s a drop in the bucket of what Harvey will eventually unleash. The estimate was already at nine trillion gallons a couple of days after the storm made landfall. But saving and restoring wetlands is nonetheless an important part of making Houston more storm resistant, says Mary Edwards, a wetlands specialist at Texas A&M’s AgriLife Extension.

    …It’s not just wetlands that are being destroyed. Prairies, which also act as floodwater sponges, have been decimated too. Below, maps show the change in the Katy Prairie, west of downtown Houston. By 1996, much of it was gone, but another 10% had been lost by 2010, while the developed acreage grew by 40%, data from HARC shows….

  8. As Hurricane Harvey hits Gulf Coast, Central Valley must prepare for the coming storm- Editorial

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    • The Big One in the form of a superstorm may come this winter, or the next or the one after that. But it is headed this way.
    • New plan calls for multi-benefit floodplain management, expanding bypasses and limiting building
    • Giving rivers and floodways more room to carry flood waters is the best way to protect communities from dangerous floods, and giving rivers more room provides multiple benefits, including clean water, parks, and habitat for fish and wildlife.
  9. Four things Houston-area leaders must do to prevent future flooding disasters

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    Read full article in the Texas Tribune

    …This may seem like a freak occurrence. But it’s the third catastrophic flooding event this region of 6.5 million people has experienced in three years. And scientists and other experts say that much of the devastation could have been prevented. …They say local officials need to account for more frequent and intense rains that are sure to come with climate change, rather than looking to what has happened in the past in their search for solutions.

    Here’s what local leaders could have done to protect the region — and what they must do to prevent such disasters in the future.

    Preserve and restore as much prairie land as possible

    Much of northwest Houston used to be covered in prairie land, where tall grasses could absorb huge amounts of floodwater….

    Restrict development in floodplains and buy flood-prone homes

    Buildings continue to go up in vulnerable floodplains all over Harris County. A few years ago the city of Houston tried to ban new development in the most flood-prone areas. …

    Plan for climate change

    In planning for flooding from future storms, local officials largely look to past rainfall totals and weather patterns. But climate change will heighten the risks that the region already faces. That’s particularly true because it sits so close to the Gulf of Mexico, where sea levels are rising and waters have been warming as the planet gets hotter….“The exact same storm that comes along today has more rain associated with it than it would have 50 or 100 years ago,” renowned climate scientist Katharine Hayhoe told The Texas Tribune last year. Hayhoe said Houston needs to plan for more frequent and intense rainstorms, just like many other cities in the country….

    Educate the public

    Hundreds of thousands of people have moved to the Houston area in recent decades; it’s consistently ranked as one of the nation’s fastest-growing cities. But people who move to flood-prone areas are often unaware of the risks….