Hurricane Katrina Storm Surge Induced Flooding Low-Lying New Orleans: How to Prevent Future Damages and

Introduction  What is storm surge  What happened during Hurricane Katrina  Why New Orleans is vulnerable  The future of New Orleans

What is a Storm Surge?  “Meteorological Residual”  Most dangerous phenomenon associated with hurricanes  Accounts for 70-90% of death & damage

What is Storm Surge?  Large change in sea level  Generated by extreme weather conditions  “Mound” of water driven toward shore by storm  Waves on top of surge devastate area Water weighs 1000 kg/m 3 – Immense potentially destructive power Water weighs 1000 kg/m 3 – Immense potentially destructive power

Background  General Factors Contribute to Storm Surge Storm Winds Storm Winds Wave Run-Up Wave Run-Up Low Pressure inside the storm Low Pressure inside the storm Astronomical Tides Astronomical Tides  Local Factors Slope of Continental Shelf Slope of Continental Shelf Shape of Coastline Shape of Coastline Elevation relative to sea level Elevation relative to sea level

Dangers of Surge  Devastating to low-lying coastal regions Bay of Bengal - India Bay of Bengal - India Galveston – Texas Galveston – Texas  Inland Surge Lake Okeechobee, Florida Lake Okeechobee, Florida m surge; Hurricane San Filippe1928-3m surge; Hurricane San Filippe 1,836 people killed, massive flooding1,836 people killed, massive flooding Lake Pontechrain, Louisiana Lake Pontechrain, Louisiana 2005 ~8m; Hurricane Katrina2005 ~8m; Hurricane Katrina Death toll-unknown and still risingDeath toll-unknown and still rising

BEFORE AFTER

Before and After

Satellite Images After – August 30th Before – August 27th eworleans_flood_0831.jpg

What Happened During Katrina?  Storm Surge ~8 meters (25-28 feet) ~8 meters (25-28 feet) Water is STRONG! Water is STRONG! Pumping Stations flooded Pumping Stations flooded Lack of drainage in cityLack of drainage in city Left helplessLeft helpless

What Happened During Katrina?  Channels/Canals Lack of sea gates allowed water to flow deep into the city Lack of sea gates allowed water to flow deep into the city Intense pressure from water and winds Intense pressure from water and winds Protective walls broke Protective walls broke Funneling Funneling MRGO & Intracoastal WaterwayMRGO & Intracoastal Waterway  New Orleans Flood Map

Why is New Orleans Vulnerable Below Sea Level  City averages 6 feet below sea level  Drainage of former swamp areas led to subsidence  Located between levees of Lake Pontchartrain and Mississippi River  Creates “bowl” effect

New Orleans Elevation

Why is New Orleans Vulnerable Disappearing Wetlands and Barrier Islands  Wetlands and Barrier Islands are best natural defense against storm surges  For every mile of continuous wetland the height of a storm surge can be reduced 3 to 8 inches  Wetlands and Barrier Islands are naturally replenished with sediment from the flooding Mississippi Before and after Hurricane Katrina /09/images/050919_katrina_delta.jpg

Why is New Orleans Vulnerable Disappearing Wetlands and Barrier Islands  Upriver Dams have reduced sediment in the river by up to 67%  Levees built around New Orleans channel the rivers flow far out into Gulf of Mexico  Wetlands and barrier islands being denied natural replenishment 8/14_hetlandc_morupdate/images/gavinspointdam_la rge.jpg

Why is New Orleans Vulnerable Disappearing Wetlands and Barrier Islands  Over the last 50 years wetland loss has been about 60 square kilometers per year  Canal construction has allowed saltwater intrusion to freshwater marshes  Additional salinity kills native plants, which causes even more erosion orps-6.jpg

The Future of New Orleans Rebuilding Current Structures  Restore New Orleans to Pre-Katrina before June 1 st Official start of hurricane season Official start of hurricane season Many building permits already given out Many building permits already given out Work continues, Wednesday, Nov. 30, 2005, at the 17th Street Canal floodwall that was breached after Hurricane Katrina in New Orleans. Government engineers performing sonar tests at the 17th Street Canal found exactly what independent investigators said they would, that steel reinforcements barely went more than half as deep as they were supposed to, a U.S. Army Corps of Engineers official said Wednesday. (AP Photo/Cheryl Gerber)

The Future of New Orleans Sea Gates  Giant air-filled walls  Across Lake Pontchartrain’s two inlets  Considered since 1960’s  Used in Holland & Britain  Cost ~ $500 million-1 billion photos.html?action=viewPhoto&photoID= The Delta Project - Holland

The Future of New Orleans Closing/Covering Canals  Only keep heavily used canals open  Cover others (turn into culverts $$$)  Turn into parks/trails Today, only a slim line of broken marsh lies between the MRGO and Lake Borgne (top of frame). MRGO

The Future of New Orleans Wetland Rehabilitation  Dredging of canals  Saltwater intrusion  Hand planting is costly

The Future of New Orleans Barrier Islands  First line of protection  Shrinking rapidly  Coast

Coast

The Future of New Orleans Other Ideas  Move pumping stations  Drainage Systems  Contain Neighborhoods  Connect barrier Islands Netherlands: Delta Works  Lowlands into parks

Conclusion  New Orleans future is unclear  Will take multiple solutions to protect the sinking city  High cost and will take years to infiltrate

THANKS!!! Chris Below Chris Dierich Keith Erickson Rachel Kjos