From BLDGBLOG
Two Water Tables
1) A neighborhood in Brooklyn known as “The Hole” is thirty feet below sea level. It is so close to the water table, in fact, that local homes are not connected to the city’s sewer system, relying instead on cesspools; the streets—with names like Ruby, Emerald, and Sapphire—are often flooded, on the verge of permanently returning to marshland. The Hole is a short documentary by Courtney Sell and Billy Feldman about this neighborhood; cowboys on horseback wander through water-logged streets while abandoned housing developments soak up rain like giant sponges....MORE
2) Montréal’s St. Pierre River “was pushed underground long ago,” we read in the Montréal Gazette...
And from Scientific American:
After a $14-Billion Upgrade, New Orleans' Levees Are Sinking
Sea level rise and ground subsidence will render the flood barriers inadequate in just four years
By Thomas Frank, E&E News on April 11, 2019The $14 billion network of levees and floodwalls that was built to protect greater New Orleans after Hurricane Katrina was a seemingly invincible bulwark against flooding....MUCH MORE
But now, 11 months after the Army Corps of Engineers completed one of the largest public works projects in world history, the agency says the system will stop providing adequate protection in as little as four years because of rising sea levels and shrinking levees.
The growing vulnerability of the New Orleans area is forcing the Army Corps to begin assessing repair work, including raising hundreds of miles of levees and floodwalls that form a meandering earth and concrete fortress around the city and its adjacent suburbs.
“These systems that maybe were protecting us before are no longer going to be able to protect us without adjustments,” said Emily Vuxton, policy director of the Coalition to Restore Coastal Louisiana, an environmental group. She said repair costs could be “hundreds of millions” of dollars, with 75% paid by federal taxpayers.
“I think this work is necessary. We have to protect the population of New Orleans,” Vuxton said.
The protection system was built over a decade and finished last May when the Army Corps completed a final component that involves pumps.
The agency’s projection that the system will “no longer provide [required] risk reduction as early as 2023” illustrates the rapidly changing conditions being experienced both globally as sea levels rise faster than expected and locally as erosion wipes out protective barrier islands and marshlands in southeastern Louisiana.
Of primary concern are the earthen levees that form the backbone of the 350-mile maze of protection that includes concrete floodwalls, pump stations and gated structures, Army Corps spokesman Matthew Roe said.
The levees are losing height as they start to settle—a natural phenomenon that is exacerbated by the soft soils in southern Louisiana. Some floodwalls are built into the levees.
But “the global incidence of sea level rise” also is contributing to the inadequacy of the levees, the Army Corps said in the April 2 Federal Register notice announcing that it is studying system improvements.
“It’s happening a little bit faster than our projections in 2007,” Roe said....