HSDRRS - coastal.la.govcoastal.la.gov/.../02/HSDRRS-presentation01112018.pdf · New Orleans Topography. B. Of course, we all know that New Orleans is like a bowl, with some areas
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HSDRRS Hurricane Storm Damage Risk Reduction System Times-Picayune / NOLA.com
HSDRRSHurricane Storm Damage Risk Reduction System
Times-Picayune / NOLA.com
Presenter
Presentation Notes
The Corps or Engineers says it is not a hurricane PROTECTION system… but is instead a �RISK REDUCTION system.
Times-Picayune / NOLA.com
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The changes since Katrina/Rita have made the system around greater metropolitan New Orleans a PERIMETER DEFENSE. Instead of canals allowing water to reach into the city, and then trying to hold the water inside the canals, the idea is to stop the water at the perimeter with improved levees, levee walls, gates and pump stations.
17th Street Canal
Orleans AvenueCanal
London AvenueCanal
Industrial Canal
Intracoastal
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New Orleans has more canals than the city of Venice, Italy. Those canals are connected to Lake Pontchartrain, the Industrial Canal (aka the IHNC—Inner Harbor Navigation Canal), the Intracoastal Waterway (GIWW), MRGO and Lake Borgne. The most infamous during Katrina were the 17th, Orleans, London and Industrial Canals.
17th Street Canal
Orleans AvenueCanal
London AvenueCanal
Industrial Canal
Intracoastal
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When the canal levee walls broke, the city experienced heavy flooding. However, west of the 17th Street Canal, Metairie and Kenner did not experience the same type of flooding. Why not? After all, they are connected to Lake Pontchartrain, too.
Orleans AvenueCanal
London AvenueCanal
Industrial Canal
Intracoastal
17th Street Canal
BAYOU ST. JOHN
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The answer is that the canals in Kenner and Metairie were protected at the lake perimeter by closures—gates and pumps. Bayou St. John also held out the lake water because it has a gate near the lake entrance.
Orleans AvenueCanal
London AvenueCanal
Industrial Canal
Intracoastal
17th Street Canal
BAYOU ST. JOHN
Presenter
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In the horror and confusion of Katrina, there was some flooding in the Kenner/Metairie area when pumps went unmanned and there was leakage. But the flooding there was nowhere near what it was in Orleans and St. Bernard Parishes.
Times-PicayuneNOLA.com
Graphic
10+ feet8-10 feet6-8 feet4-6 feet2-4 feet0-2 feet
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We certainly remember the depths of the floodwaters when the canal walls broke.
City of New OrleansGround Elevations
From Canal St. at Mississippi River
to theLakefront at U.N.O.
NEWORLEANS
A
BLAKE PONCHARTRAIN
A
MR&TPROJECT DESIGNFLOWLINE (18 FEET)
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. C. S
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IDE
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RIG
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LONDON AVENUE CANAL FLOODWALLHURRICANE LEVEE / FLOODWALL (14.0 FEET)
30
20
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-10
-20
30
20
10
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-10
-20
ELEV
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IN F
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VD
FLOODWALL ALONGMISSISSIPPI RIVER
23 FT
New Orleans Topography
B
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Of course, we all know that New Orleans is like a bowl, with some areas below sea level. Water can accumulate in this “bowl” from torrential rain alone, and in Katrina it filled mostly from the lake water flowing into the city through the broken levee walls along the canals.
17th Street Canal
Orleans AvenueCanal
London AvenueCanal
Intracoastal
BAYOU ST. JOHN
Industrial Canal
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The drainage design has always been for water from the bowl to be pumped up into OUTFALL CANALS—the elevated 17th, Orleans and London canals—and let the water gravity-flow into Lake Pontchartrain. For navigation purposes, the Industrial Canal has always been open at the lake and the Intracoastal Waterway.
17th Street Canal
Orleans AvenueCanal
London AvenueCanal
Industrial Canal
Intracoastal
BAYOU ST. JOHN
Presenter
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But when storm surge filled up Lake Pontchartrain, instead of the outfall canals flowing into the lake, the lake surged into the canals. The levee walls lining the canals were not up to the task. They broke and flooded the city.
Times-PicayuneNOLA.com
Lesson Learned:PROTECT THE PERIMETER
Times-PicayuneNOLA.com
Graphic
10+ feet8-10 feet6-8 feet4-6 feet2-4 feet0-2 feet
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Lesson learned: Protect the perimeter and you better-protect the city. The closures that leaked in Kenner and Metairie were improved, and most importantly in Orleans Parish, at their connections to Lake Pontchartrain the outfall canals received pumps and gates that could be closed, and water could be PUMPED out into the lake. No more relying on gravity and open outfall canals. The Corps built Interim Control Structures (pumps) along the open perimeter.
17th Street Canal
BAYOU ST. JOHN
17th
ORLEANS
LONDON
INTERIM PUMPS: PERMANENT PUMPS:
9,200 cfs12,600 cfs 37%
17th Street Canal
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The interim pumps were very good, and as of January of this year (2018) they’ve been replaced by even better permanent pump stations. At the 17th Street closure, the interim pumping capacity has been increased by 37 per cent to 12,600 cubic feet per second (cfs) for the Permanent Pump station.
INTERIM PUMPS: PERMANENT PUMPS:
2,200 cfs2,700 cfs 23%
BAYOU ST. JOHN
17th
ORLEANS
LONDON
Orleans Avenue Canal
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At the Orleans Avenue closure, the interim pumping capacity has been increased by 23 per cent to 2,700 cubic feet per second (cfs) for the Permanent Pump station.
BAYOU ST. JOHN
17th
ORLEANS
INTERIM PUMPS: PERMANENT PUMPS:
5,200 cfs9,000 cfs 73%
LONDON
London Avenue Canal
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At the London Avenue closure, the interim pumping capacity has been increased by 73 per cent to 9,000 cubic feet per second (cfs) for the Permanent Pump station.
Navigable Width: 95’2 Lift Gates: 50’ wide each
Height: 16’ above sea level
Sill Depth: 18’ below sea level
BAYOU ST. JOHN
17th
ORLEANS
LONDON
SEABROOK
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No pumps installed at the Seabrook opening to the Industrial Canal, but a sector gate can close the 95-foot-wide navigation channel, along with 50-foot lift gates on either side of it. Fully closed, 16-feet of storm surge from the lake can be held out.
24,300 cfs
BAYOU ST. JOHN
17th
ORLEANS
LONDON16,000 cfs
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So, on the Outfall Canals, we have gone from no capacity to pump water out of New Orleans, to an interim pumping capacity of 16,000 cfs, to the current capacity of 24,300 cfs with the Permanent Pumps.
Canal(normal water level)
I- Wall
Levee
Steel Sheet Pile
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In many places along the canals and on the outer perimeter, smaller I-Walls have been replaced with T-Walls that are bigger, stronger, better armored, and have a deeper, foundation of sheet piling and supporting structures. How much bigger? Have a look.
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The smaller I-Wall is on the left, and the T-Wall is on the right. Building the T-Walls was an incredible construction project.
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Someone snapped this at sunset with their Blackberry cell phone. It was a massive project, and it had to be done quickly—because who knew when the next Katrina might strike the area—but it also had to be done right. A great engineering accomplishment.
26 miles
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This particular stretch of T-Wall extends about 26 miles in this perimeter section of St. Bernard Parish—more than the length of the Causeway across Lake Pontchartrain.
LPVLAKE PONTCHARTRAIN AND VICINITY
Includes 77 risk reduction features in St. Charles, Jefferson, Orleans, and St. Bernard parishes.
Presenter
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That is just a part of the perimeter system that makes up the HSDRRS system. On the East Bank, the project is called the LPV: Lake Pontchartrain & Vicinity project.
LPVLAKE PONTCHARTRAIN AND VICINITY
Includes 77 risk reduction features in St. Charles, Jefferson, Orleans, and St. Bernard parishes.
WBVWESTBANK AND VICINITYIncludes 98 risk reduction features in St. Charles, Jefferson, Orleans, and
Plaquemines parishes.
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On the West Bank, it is called the WBV, the West Bank & Vicinity. The outer perimeter of each has improved earthen levees, levee walls, gates and pumps, an outer perimeter that tie into the river levees on either side of the Mississippi.
PERIMETER: 133 Miles
TOTAL: 350 miles with interior levees/floodwalls
75 Pump Stations
Total Pumping Capacity: 8 Million cfs TOTAL COST:$14+ Billion
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Combined, the HSDRRS system has a 133 mile perimeter—350 miles if you include the interior levees and floodwalls. It has 75 pump stations with a combined total pumping capacity of 8 Million cfs. The cost: more than $14 Billion.
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If any water does get past the perimeter, the internal areas are sectioned off into drainage districts, so if water gets into one area it won’t necessarily flow into another area.
WEST CLOSURE COMPLEX
IHNC SURGE BARRIER
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Two of the most impressive construction projects along the perimeter are the IHNC Surge Barrier and the West Closure Complex.
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The site of the IHNC Surge Barrier is at the confluence of the Intracoastal Waterway (GIWW) and the Mississippi River Gulf Outlet (MRGO) where Katrina’s storm surge was funneled into the Intracoastal and then into the Industrial Canal.
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The levee wall along the Industrial Canal broke, flooding the Lower 9th Ward and beyond. The overtopping of MRGO also helped to flood the entire area to depths of 12 feet and more.
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To secure the perimeter in this area, that 26-mile T-Wall was built, MRGO was closed with a rock structure across it below Hopedale, and the Surge Barrier was built at the point where the surge funneled in.
SECTOR GATEBARGE GATEEach 150’ wide
LIFT GATE56’ wide
COST:$1.1 Billion~
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The barrier keeps storm surge from Lake Borgne entering New Orleans. But on a normal day with no surge, there are 3 gates that can be open to allow boats and barges to pass through. At the north end are two channels, each 150 feet wide, with a sector gate and a barge gate that can be closed, and more to the middle, there is a 56-foot-wide lift gate.
Largest continuous surge barrierin the world: 1.8 miles
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The Corps had to invent new construction methods and techniques to create the barrier as strong as it needs to be, and in a quick amount of time before the next hurricane might hit.
26’ ABOVE Sea Level
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The top of the barrier is 26 feet above sea level, so it will take an incredible storm surge to overtop it.
647Steel
Batter Piles3’ diameter
Sea Level
26’ ABOVE Sea Level
129’ below waterline
190’ below
waterline
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But as much as you see of the barrier, 80 percent of it is below the water line and the subsurface mud line.
The West Bank also has a perimeter of levees, levee walls, gates and pumps that tie into the Mississippi River levee. When a storm is coming from the Gulf, the system is closed tight and the surge is kept out.
3 PUMPS8,991 cfs
6 PUMPS15,623 cfs
WBV
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But, like New Orleans, when completely closed and sealed from storm surge, the enclosed area can flood from torrential rainfall alone. So, 9 pumps deliver the water into the Harvey and Algiers canals, and they flow to the West Closure Complex.
Removed more than 25 miles of levees and floodwalls from direct surge impact
WCC COST:$1 Billion~
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The structure is open to the Intracoastal Waterway. The navigation opening is 225-feet wide, but can be closed off with the largest sector gate in the Western Hemisphere. The gates are 32-feet tall. To get rainwater out of the system, the pump station’s 11 pumps generate a combined force of nearly 60-thousand horsepower. This structure has allowed for 25 miles of levees and floodwalls to be removed from the direct impact of storm surge.
Largest Pump Station in the World
19,426 cfS
1,165,560 cf /minute
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This is the largest pump station in the entire world, with a capacity of more than 19,400 cfs—that’s more than a million cubic feet per minute.
