NASA radar watches over California's aging levees

Space Daily via NASA: One morning in 2008, research scientist Cathleen Jones of NASA's Jet Propulsion Laboratory in Pasadena, Calif., was flying over the San Andreas fault near San Francisco, testing a new radar instrument built at JPL. As the plane banked to make a turn, she looked down to see the Sacramento River delta, a patchwork of low-lying lands crisscrossed by levees.

Jones was using an instrument that can measure tiny movements of the ground on the scale of less than half an inch (less than a centimeter). It's called the Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR).

"It struck me that this new instrument might be perfect for monitoring movement of levees," said Jones. Checking the scientific literature, she found that nothing like that had been attempted before in the delta. She reported her idea to water managers at the California Department of Water Resources (DWR). She didn't know it, but she was at the beginning of a long-lived initiative to refine NASA technology for use in safeguarding the delta levees.

In the Sacramento River delta north of San Francisco Bay, islands, agricultural lands and communities below sea level are protected from surrounding water channels by more than 1,100 miles (1,800 kilometers) of dirt levees, many of which date back to the California Gold Rush. About two-thirds of all Californians and more than 4 million acres of irrigated farmland rely on the delta for water.

If a levee gives way, the results can be disastrous. A single 2004 levee failure created $90 million of damage and threatened the water supply to Southern California. However, the first warning that a levee is developing a structural problem can be a tiny soil deformation -- too small to be noticed by a visual inspection....

FEMA photo of a levee near Bombay Beach, California

New study proposes changes in New Orleans area levee systems

William G. Gilroy in Notre Dame News: Less may mean more when it comes to the levee systems designed to protect New Orleans from hurricanes. That’s the conclusion of a new study by a team of University of Notre Dame researchers led by Joannes Westerink, chair of the department of civil and environmental engineering and earth sciences and co-developer of the authoritative computer model for storm surge used by the U.S. Army Corps of Engineers, the Federal Emergency Management Agency (FEMA) and the state of Louisiana to determine water levels due to hurricane surge and to design levee heights and alignments.

The lower Mississippi River south of New Orleans protrudes into the Gulf of Mexico, and man-made levees line the west bank of the river for 55 kilometers of what is known as the Lower Plaquemines section. There are no levees on the east side of this stretch of the river. Westerink points out that, historically, sustained easterly winds from hurricanes have directed storm surge across Breton Sound into the Mississippi River and against its west bank levees.

“This study clearly shows that the man-built west bank levees on the lower Mississippi River enhance the capture of storm surge by the river,” Westerink said. “The surges are generated by the prevalent easterly winds that are common for regional hurricanes, but they spill into the river. These surges then propagate upriver, endangering New Orleans from the river side.”

As an alternative, the study shows that the lowering of man-made levees along the Lower Plaquemines river section to their natural state, to allow storm surge to partially pass across the Mississippi River, will decrease storm surge upriver toward New Orleans.

“By eliminating the 55 kilometers of man-made levees on the west bank of the river from Pointe a la Hache and Venice, the surges propagating in the river from Pointe a la Hache past New Orleans will be lowered by up to two meters,” Westerink said. “This would save billions of dollars in levee construction to protect communities upriver from Pointe a la Hache.”...

FEMA image of the 17th Street levee in New Orleans

Inspectors examine levees in New Orleans, post-Isaac

Pete Spotts in the Alaska Dispatch via the Christian Science Monitor: Hurricane Isaac has come and gone. Floodwaters in southeastern Louisiana are receding. For Chris Gilmore, it's time to take initial stock of how his segment of a $14.5-billion, 133-mile defensive wall of earth, steel, and concrete preformed in the first real-world test of post-Katrina improvements in flood protection for New Orleans and portions of surrounding parishes.

Isaac was a minimal hurricane when it made landfall overnight Aug. 28-29. But its large size and excruciatingly slow motion – at one point stalling for hours over the southeastern part of the state – built a surge whose height here at St. Bernard Parish, estimated at between 14 and 15 feet, rivaled the height of the surge Katrina delivered.

The view from the levee top reveals large patches of dead-wood debris lying along the levee's base like so many casualties of a siege assault. Behind the levee and the new pair of massive steel floodgates that close across the four lanes and center median of Louisiana State Road 46, boats on trailers, RV trailers, and even trailers from 18-wheelers are parked along the highway shoulders. They belong to residents who live beyond the levee and who sought its protection for their hard-earned assets.

So how did this segment hold up? "It looks really good," pronounces the US Army Corps of Engineers' Mr. Gilmore, senior project manager for the St. Bernard Parish portion of the federally funded upgraded flood defenses.

Indeed, so far the most significant levee damage has come from wild hogs, who root around for worms and insects after heavy rains. These "hog holes" will require quick attention. They can accelerate erosion of a levee's earthen base.

Although inspections are still under way, the initial reaction to the post-Katrina improvements to the levees, as well as to the pumping systems that drain water from New Orleans into canals that feed into Lake Ponchartrain, is that they worked as advertised....

Levee repair in New Orleans' Industrial Canal after Katrina, shot by Stephen Marchetti, Wikimedia Commons via Flickr, under the Creative Commons Attribution-Share Alike 2.0 Generic license

Racing to fix California levees before the big one hits

Jeremy Miller on KQED.org: For those who know little about the massive estuary an hour east of downtown San Francisco, the Delta is the meeting place of two of the state’s largest river systems, the Sacramento and San Joaquin. Flowing down from Sierra snowfields and lakes, the two rivers converge in this 1600-square-mile tangle of tidal marshes, sloughs and canals.

As California’s population and economy has grown, so has demand for water, much of which is pumped from the Delta and delivered throughout the state by way of sprawling networks of reservoirs, canals and aqueducts. (For more on the Delta’s geography and history, see the interactive map and presentation accompanying the report.)

A key challenge examined in Sommer’s report is the issue of sea level rise, which makes the Delta’s aging and subsiding 1100-mile levee system increasingly vulnerable to flooding and failure. The threat is magnified by the risk of a major earthquake, which by most accounts the Bay Area is due for. For example, in 2009, the US Geological Survey predicted that there is a 62% chance of a 6.7-magnitude or greater earthquake striking the Bay Area in the period between 2003 and 2032.

...A levee failure could result in a rush of saltwater into the Delta, a scenario sometimes referred to as the “big gulp.”...

Image of head of Old River along lower San Joaquin River provided by M.Burns (CADWR) for release into public domain by MCalamari

Levee breach spared city from brunt of flood

Debra Levey Larson in Futurity.org: When faced with a choice between a deluge or a controlled deluge in May 2011 that would protect the city of Cairo, Illinois, the U.S. Army Corps of Engineers chose the latter. But was ordering an intentional breach of the Mississippi River levee at Bird’s Point the right decision?

“The decision was a difficult and complex engineering problem with significant social and political trade-offs between loss of human lives and loss of properties in urban and rural areas,” says University of Illinois researcher Ken Olson. “But it was a calculated risk built on a growing body of river science and prior flooding experiences.”

The city of Cairo occupies a small sliver of land about 2 square miles or 1,300 acres in size, which is only 1 percent of the size of the New Madrid Floodway (210 square miles or 133,000 acres).

“Due to the size of Cairo and lack of an outlet, even if the sea wall or the earthen levee system which protects Cairo had failed, the filling of the city with floodwater would have done little to drop the record Cairo gauge peak of 61.72 feet on May 3, 2011, and threats to downstream levees would have continued to be a high concern.”

According to Olson’s study, published in the Journal of Soil and Water Conservation, the greatest danger to levee failure is constant water pressure against the levee. The weight of the river pushes water underneath the levee, creating boils and undermining the strength of the levee and its capacity to hold water. Consequently, allowing the levee to break on its own would have created much more damage.

...In Olson’s opinion, the failure of the seawall and levee system would have covered the city of Cairo with 22 feet of floodwater for days and could have resulted in significant loss of life and severe damage to more than 600 buildings in the cities of Cairo, Future City, and Urbandale, Illinois...

This NASA shot of Cairo, Illinois, at the confluence of the Ohio and Mississippi Rivers shows how vulnerable it is to flooding

Levee fixes in California lead to more building — and more risk

Gosia Wozniacka in Recordnet.com via the Associated Press: ...In Lathrop [California], which mushroomed on a Valley floodplain, 18,000 people live in the shadows of levees that once failed. To pave the way for thousands more homes and a tripling of its population, the community is making levee repairs funded largely by $5 billion in state voter-approved flood control bonds.

In California, whose antiquated levee system is the nation's largest, such ambitious plans have raised the stakes in a long-running debate over how much should be built behind levees designed in large part to safeguard farmland, not the 1 million people and $69 billion in property now protected by them.

The planned development in Lathrop and other flood-prone places also has raised questions about whether the state's flood control spending is heading off a potentially disastrous problem or will exacerbate it in the long run.

...An AP analysis of the $3 billion spent so far shows the largest expenditures have focused on improving levees in flood-prone areas where development recently occurred and where much more growth is planned. In several cases, the levee projects were also partially financed by developers waiting to build more housing on the floodplains.

...Critics say this is a poor way to spend the state's flood control dollars, because encouraging new development in floodplains puts more people and property at risk. And higher risk means ever-escalating demands for levee repairs, as well as greater rescue and rebuilding costs after flooding.

"It doesn't make economic sense," said Jeffrey Mount, geology professor at UC Davis. "The state should not be funding projects that induce growth and increase flood risk."....Experts say the state needs to do more to limit aggressive development behind levees....

Yuba County, CA, January 4, 1997 -- A levee break caused the flood-swollen Feather River to pour into the Oliverhurst area in Yuba County, California, photo by Robert Eplett/FEMA

Inadequate flood protection from suspect US levees

Evan Lehman in Scientific American via ClimateWire: Levees are as varied in the United States as the people they guard. They're shaped like snakes, rings and spurs that can be tough, flimsy or a century old. No one knows for sure where all of these earthen walls are, who built them or what type of rocky mixture lies shrouded inside their bulk. Some help protect homes from flooding, while others ring industrial zones containing chemical plants and refineries. Many stop rivers from turning into lakes on farms that abut the riverfront.

They shadow the diverse landscapes they protect. But these widely disparate levees do share at least two common traits -- they are all steadily weakening from water's efforts to go under, over or straight through their earthy embankment. Very few were built to protect against the more powerful storms expected by climate scientists and the flooding that will accompany them.

Now, after years of treating suspect levees with remarkable caution, federal flood officials are recalibrating the way they view the risk to communities lying behind these walls. Government officials say it's driven by better scientific methods used to measure precise flood hazards. But critics believe it could result in still more homes being built in the path of runaway water.

"I do think it's a huge concern," said Shana Udvardy, who directs flood management policy for American Rivers. "The risk is, people are going to believe they're safe when they're not." At last count, there were roughly 30,000 miles of levees across the country. String them together and they would wrap around the world, and then some. Here's another way to harness their ubiquity: For every McDonald's restaurant in America, there are more than 2 miles of levees.

And most of them, almost 70 percent, are not trusted by government flood officials to do their job. The Federal Emergency Management Agency (FEMA) said in 2010 that 20,350 miles of levee walls are "not accredited" -- meaning that those who live behind the barriers are assumed to be threatened by a "high risk" of flooding....

Boys climbing on a levee in New Orleans, shot by Carly Lesser & Art Drauglis, Wikimedia Commons via Flickr, under the Creative Commons Attribution-Share Alike 2.0 Generic license

West bank levee-raising won't take toll on east bank, corps officials claim

Mark Schleifstein in the New Orleans Times-Picayune: The raising of levees along the west bank of the Mississippi River by as much as 2 1/2 feet will not put residents of St. Bernard Parish and the east bank of New Orleans at heightened risk from storm surge in a 100-year hurricane, a team of Army Corps of Engineers officials said Thursday. The briefing was aimed at allaying fears of members of the Southeast Louisiana Flood Protection Authority-East, who have raised concerns that the east bank levees are now too low.

Corps officials said it’s actually the waves atop a hurricane’s surge that threaten the 15.5-mile-long stretch of West Bank levees that have been raised between English Turn and Belle Chasse. Those waves, however, would be created by winds blowing out of the east that accompany the few storms that could push surge up the river, said Max Agnew, a corps hydraulic engineer, and the waves thus would be moving toward the West Bank side of the river.
Concerns about surge traveling upriver were raised in the aftermath of Hurricane Katrina in 2005, when several barges were deposited atop West Bank levees in Algiers.

But the corps didn’t decide higher river levees needed to be incorporated into the area’s system until last year, after complex computer modeling confirmed that some 100-year storms, which have a 1 percent chance of occurring in any year, would push water over the levees.

Corps officials recently announced a second increase in the height of some segments along that 15.5-mile stretch, to be accomplished with either higher earthen levees or installation of concrete walls. Those are supposed to increase what the corps calls “resiliency” — the ability to withstand overtopping from surges caused by a 500-year storm without failing.

The designs also build in expected rises in relative sea level — the combination of sinking soil beneath the levee and higher water levels resulting from climate change — over the next 50 years, which could be between 2 and 3 feet. The average level of water in the river at the Carrollton Gage in New Orleans has been rising by about a third of an inch a year for the past 50 years, according to a corps study. The corps requires levees to be designed to accommodate the effects of sea-level rise over their lifetime, using low, moderate and high estimates of the effects of climate change....

Painting depicting New Orleans, on fire, after Hurricane Katrina; Louisiana Superdome at center. By Joy Garnett, Wikimedia Commons via Flickr, under the Creative Commons Attribution-Share Alike 2.0 Generic license

US Army Corps of Engineers pegs 2011 flood damage to levees at $2 billion

Heather Hollingsworth in the Insurance Journal: The U.S. Army Corps of Engineers estimates it will cost more than $2 billion to repair the damage to the nation’s levees, dams and riverbanks caused by this year’s excessive flooding, a sum that dwarfs $150 million it currently has to make such repairs and that doesn’t account for damage from Hurricane Irene or Tropical Storm Lee.

Floodwaters that raged down the nation’s rivers this year have strained dams, eroded riverbanks, filled harbors with silt and ripped football field-sized holes in some earthen levees protecting farmland and small towns. The damage estimate, confirmed to The Associated Press by corps officials, promises to be more significant than with a typical flood in which high water recedes quickly. The estimate does not factor in flood damage caused by Hurricane Irene and Tropical Storm Lee, and the corps does not have an estimate of the damage from those storms yet.

Along some stretches of the Missouri River, levees have been holding back floodwaters since June 1 as the corps lowered water levels from upstream dams that had filled to overflowing with record runoff from rain and winter snows. That water ultimately proved too much for many levees downstream in states such as Iowa and Missouri. Record high water levels also created havoc along the lower Mississippi from Missouri to Louisiana.

“I’m really nervous about it,” Tom Waters, chairman of the Missouri Levee and Drainage District Association, said of the limited resources. “I think the corps is real nervous about it, too.”

The Senate is considering a $7 billion emergency disaster relief bill, but only $1.3 billion of that would go to the corps. A competing House bill would allocate $3.7 billion to overall disaster aid, $226 million of it to the corps, although Congress could provide more money in future legislation.

Iowa Sen. Tom Harkin said he is working with senators in neighboring states to urge support for the emergency relief. “I have seen firsthand some of the devastation along these rivers and local communities need financial assistance to recover,” Harkin said...

Flooding and levee breach at the confluence of the Nishnabottna and Missouri Rivers on June 16, 2011 during the 2011 Missouri River floods, from the US Army Corps of Engineers

Earthen levees on Missouri River at risk

Josh Funk in STL Today via the AP: Experts say several levees along the Missouri River, especially older ones in rural areas, are at risk of failing this summer as massive amounts of water continue to flow through the river system from upriver reservoirs, but chances of such failures in urban areas remain remote.

So far, most levees have held along the 811 miles the Missouri travels from the last dam at Gavins Point in South Dakota to its confluence with the Mississippi River near St. Louis. But engineers who have studied past floods say the earthen levees in rural areas are at greater risk. "Most of the levees are agricultural levees. They're not engineered. They're just dirt piled up," said David Rogers, an engineering professor at Missouri University of Science and Technology.

A few levees have failed, but most of the flooding thus far has covered more than 560,000 acres of mostly rural land. The water has forced some evacuations, but the extent of the damage may not be clear until it recedes. That's not expected to happen until the fall as the Army Corps of Engineers says it needs to continue releasing substantial amounts of water from upstream reservoirs inundated with heavy spring rains and melt from an above average Rocky Mountain snowpack.

...The corps predicts the Missouri River will remain 5 to 7 feet above flood stage in much of Nebraska and Iowa and may rise as high as 10 feet above flood stage in Missouri until at least mid-August.

The corps predicts that the river will eventually rise high enough to flow over some 18 to 70 levees, mostly in rural areas of southeast Nebraska, southwest Iowa and Missouri. Other levees will become saturated, and water can erode their foundations, seep underneath or find other flaws to exploit....

Water flows from the Missouri River over levee L-550, located north of Highway 136 in Atchison County, Mo., June 19. The local sponsor reported overtopping of the levee to the U.S. Army Corps of Engineers the morning of June 19. The levee is in the Federal Program (PL 84-99) and is operated and maintained by a non-federal sponsor. It was constructed by the Corps in the late 1940s. (U.S. Army Corps of Engineers photo by Carlos J. Lazo)

Without strategy, the Sacramento-San Joaquin Delta risks disaster

Raymond Seed is a director of the Delta Vision Foundation and is a professor of civil and environmental engineering at the University of California, Berkeley. In the Sacramento Bee describes a potential for interlocking failures in the tightly coupled water system of the Central Valley’s water system: Northern California's wet, cold spring may have ruined many a picnic, but it portends a much more serious crisis once temperatures warm up. Across the Central Valley, communities are bracing for a potential onslaught of runoff water brought on by a rapidly melting snowpack. This circumstance would be considered a threat even in places with a robust emergency preparedness plan and a strong infrastructure. For communities near the Sacramento-San Joaquin Delta, a sudden heat wave and resulting flooding could be disastrous.

The two biggest threats to personal safety of Delta residents are flooding and earthquakes leading to multiple levee failures in the region. Despite recent progress in other areas, realistic preparations by the state for response to a flood or seismic event in the Delta are still sorely lacking, with regard to life safety activities including preparation, rescue and response. In addition, the Delta is the heart of the state's extensive water systems, providing water to more than 23 million Californians. In the case of an earthquake or catastrophic flooding, the state's water, transportation and utility infrastructure could well be disrupted for weeks, months or longer.

…Securing the state's water future will require hard work and a mending of wasteful ways. It will require optimizing efficient water use in every way possible, and constructing new facilities for conveyance and storage. It will also require fostering cooperation among all stakeholders to do what is right for the state as a whole. All of this will need to be accomplished while protecting and restoring the Delta ecosystems while also reducing risks to people, property and the state's economy.

The state's water challenges cannot be solved overnight, but there is now an increasingly clear and defined path forward. The Delta Vision Strategic Plan should be implemented without further delay. If it is not, the Delta will continue to be at risk of either a weather-related or earthquake-related disaster – an entirely foreseeable, preventable and unacceptable disaster, and one just waiting to happen….

A levee along the Sacramento River, shot by Indolences

Levees are decades-old protectors

Julie Cooper in the Natchez-Democrat (Mississippi) provides some history to the levees holding back the surging river: The history of the Mississippi River levee system as we know it really begins in 1927. Levees weren’t a new idea then, but creating a federally controlled system of them was. The Great Mississippi River Flood of 1927 killed 246 people and covered thousands of square miles with up to 30 feet of water.

Levees along the Mississippi and its tributaries have existed since the 1800s. But it wasn’t until the Flood Control Act of 1928 that they began to grow taller, stronger and were connected to form a mainline levee all along the river.

The U.S. Corps of Engineers Vicksburg District was unable to provide any exact dates for work done on the local levees, but said work to strengthen the levee system has continued as funding was appropriated since 1928.

In addition to the mainline Mississippi River levee that runs the length of the river in Concordia Parish and to the north and south of it, the parish is nearly totally ringed with another levee system. The ring levee, as local leaders call it, runs alongside the Red, Black and Tensas rivers.

…Local levees were built up from the originals constructed well before the Civil War, Robinson said. They are composed of dirt and clay. A hydrologic analysis is used to determine what the appropriate construction and height should be, he said.

“They go out and do geological borings to analyze and look at what the structure of the existing levee is,” Robinson said. The results of those studies direct the Corps to know what type of dirt is best for that particular section of levee…

The Great Mississippi Flood of 1927, dynamiting through the levee to create an artificial crevasse at Caernarvon, St. Bernard Parish, Louisiana, 14 miles below New Orleans. The crevasse was created to take pressure off levees at New Orleans

How to make a wave behave

USDA Agricultural Research Service: In the lower Mississippi Delta, farmers often build ponds for aquaculture and for storing surface water to irrigate crops. But erosion generated by wind-driven waves can reduce reservoir levee widths by a foot every year, and repairs can be needed as soon as 5 years after a reservoir is completed.

It’s not simple—or cheap—to patch up a reservoir with silt loam levees that can stretch over a mile and that are 25 to 30 feet wide. The costs can average $3 per foot, which adds up to around $15,000 per structure. People have tried to stabilize the levees with tires, construction materials, or vegetation, but hydraulic engineer Daniel Wren is experimenting with another approach. “We wanted to see if we could find a way to cut down on the erosive energy hitting the levees,” he says.

Wren, who works at the Agricultural Research Service’s Watershed Physical Processes Research Unit in Oxford, Mississippi, partnered with ARS hydraulic engineer Carlos Alonso (now retired) and University of Mississippi research associate Yavuz Ozeren for his research. The team gathered data about wind and wave dynamics from a 70-acre irrigation reservoir in Arkansas. Then they took their data into the lab and designed several wave barriers that they tested in a 63-foot-long wave flume.

Lab results indicated that a floating barrier held in place by two rows of pilings would provide the most effective embankment protection from wave action (see diagram). The barrier was made of a 9½-inch-diameter tube that was attached to a 4¾-inch-diameter tube with a 24-inch length of smaller tubing. Since it was confined between the two rows of pilings, the barrier was able to rise and fall with fluctuating water levels—unlike a barrier tethered to the bottom of the pond, which might end up below the water surface as reservoir levels rise.

The team found that this two-tube barrier was able to dissipate 75 percent of wave energy for waves within the design range before they washed against the levees. The waves lost some of their force when they broke against the first tube and then lost even more energy as they broke against the second tube....

Illustration from the USDA website