Hurricane Katrina

===Analysis of New Orleans levee failures===
{{Main|2005 levee failures in Greater New Orleans}}
[[File:Hurricane Katrina Eye viewed from Hurricane Hunter.jpg|thumb|upright|View of the eyewall of Hurricane Katrina taken on August 28, 2005, as seen from a [[NOAA]] [[WP-3D Orion|WP-3D]] [[hurricane hunter]] aircraft before the storm made landfall on the United States [[Gulf Coast]]]]
According to a modeling exercise conducted by the [[U.S. Army Corps of Engineers]] (USACE), two-thirds of the deaths in [[Greater New Orleans]] were due to levee and [[flood wall]] failure.<ref>Charles F. Anderson, Jurjen A. Battjes; et al. (2007). "The New Orleans Hurricane Protection System: What Went Wrong and Why" [http://biotech.law.lsu.edu/katrina/reports/ERPreport.pdf (PDF)] {{Webarchive|url=https://web.archive.org/web/20160304061810/http://biotech.law.lsu.edu/katrina/reports/ERPreport.pdf |date=March 4, 2016}}. American Society of Civil Engineers. Retrieved July 25, 2016.</ref> On April 5, 2006, months after independent investigators had demonstrated that levee failures were not caused by natural forces beyond intended design strength, Lieutenant General [[Carl Strock]], [[chief of engineers]] and commander of the Corps of Engineers, testified before the United States Senate Subcommittee on Energy and Water that "We have now concluded we had problems with the design of the structure."<ref>Staff Writers [https://web.archive.org/web/20080527010320/http://www.unregisterednews.com/content/view/184/53/ "Problems with the design of levees"]. ''[[Unregistered News]]''. September 29, 2005. Retrieved on April 14, 2010.</ref>

A June 2007 report released by the [[American Society of Civil Engineers]] determined that the failures of the levees and flood walls in New Orleans were found to be primarily the result of system design and construction flaws.<ref name="ASCE HKERP report"/> The U.S. Army Corps of Engineers had been federally mandated in the [[Flood Control Act of 1965]] with responsibility for the conception, design, and construction of the region's flood-control system. All of the major studies in the aftermath of Katrina concluded that the USACE was responsible for the failure of the levees. This was primarily attributed to a decision to use shorter steel sheet pilings during construction in an effort to save money.<ref name="Robertson"/> According to a report published in August 2015 in the official journal of the [[World Water Council]], the Corps misinterpreted the results of a 1985 study and wrongly concluded that sheet piles in the flood walls needed to be driven to depths of only {{convert|17|ft|0}} instead of between {{convert|31|and|46|ft|0}}. That decision saved approximately US$100 million, but significantly reduced overall engineering reliability.<ref>{{cite news |page=707 |author1=J. David Rogers |author2=G. Paul Kemp |title=Interaction between the US Army Corps of Engineers and the Orleans Levee Board preceding the drainage canal wall failures and catastrophic flooding of New Orleans in 2005 |publisher=Water Policy |year=2015 |access-date=January 28, 2017 |url=http://wp.iwaponline.com/content/17/4/707 |archive-url=https://web.archive.org/web/20170203220852/http://wp.iwaponline.com/content/17/4/707 |archive-date=February 3, 2017 |url-status=live}}</ref>

In January 2008, Judge [[Stanwood Duval]] of the U.S. District Court ruled that despite the Corps' role in the flooding, the agency<ref name="Nossiter"/> could not be held financially liable because of [[sovereign immunity]] in the [[Flood Control Act of 1928]]. Exactly ten years after Katrina, J. David Rogers, lead author of a new report in the official journal of the World Water Council, concluded that the flooding during Katrina "could have been prevented had the corps retained an external review board to double-check its flood-wall designs".<ref>{{cite news|last=Stoltz|first=Mary Helen|title=Flood damage after Katrina could have been prevented, S&T expert says|publisher=Missouri S&T|date=August 24, 2015|access-date=February 22, 2016|url=http://news.mst.edu/2015/08/flood-damage-after-katrina-could-have-been-prevented-st-expert-says/|archive-url=https://web.archive.org/web/20160220034916/http://news.mst.edu/2015/08/flood-damage-after-katrina-could-have-been-prevented-st-expert-says/|archive-date=February 20, 2016|url-status=live}}</ref>

Other factors may have contributed to the flooding. According to the authors of ''Catastrophe in the Making'' (Island Press, 2009), the straight design and lack of outward flow into the Gulf allowed the [[Mississippi River-Gulf Outlet Canal]] to become "the perfect shortcut for salt-water intrusion" which damaged buffering cypress forests and wetlands which historically had protected New Orleans from storm surge.<ref>{{cite book|page=120|author1=Freudenburg, William R.|first2=Robert|last2=Gramling|title=Catastrophe in the Making|publisher=Island Press|year=2009|access-date=October 15, 2015|url=https://www.islandpress.org/book/catastrophe-in-the-making|display-authors=etal|archive-url=https://web.archive.org/web/20160105121505/https://www.islandpress.org/book/catastrophe-in-the-making|archive-date=January 5, 2016|url-status=live}}</ref> The Army Corps of Engineers built and maintained the canal. Furthermore, according to storm surge researcher Hassan Mashriqui:

{{blockquote|Storm surge pushing across shallow [[Lake Borgne]] from the east is constrained by these MRGO levees to the south and, to the north, by the long-standing levees of the Intracoastal Waterway (GIWW). Initially ten or more miles apart, these two channels meet, and when they do, the water building between their levees is squeezed into a single channel – the Funnel – only 260 yards wide, constrained by levees 14 feet to 16 feet high….In concert with the denuded marshes, it could increase the local storm surge hitting the Intracoastal Waterway by 20 percent to 40 percent – a critical and fundamental flaw.<ref>{{Cite book|url=https://books.google.com/books?id=ZNroiySUreQC|title=The Storm: What Went Wrong and Why During Hurricane Katrina&nbsp;– the Inside Story from One Louisiana Scientist|first1=Ivor van|last1=Heerden|first2=Mike|last2=Bryan|date=May 18, 2006|publisher=Penguin|via=Google Books|isbn=9781101201701|access-date=October 30, 2015|archive-url=https://web.archive.org/web/20160428000452/https://books.google.com/books?id=ZNroiySUreQC|archive-date=April 28, 2016|url-status=live}}</ref>}}

[[File:Katrina-new-orleans-flooding3-2005.jpg|thumb|View of flooded New Orleans in the aftermath of Hurricane Katrina]]
The Corps of Engineers disputes these causalities.<ref>Warrick, Joby; Grunwald, Michael. [https://www.washingtonpost.com/wp-dyn/content/article/2005/10/23/AR2005102301200_pf.html "Investigators Link Levee Failures to Design Flaws"]. {{Webarchive|url=https://web.archive.org/web/20161125035439/http://www.washingtonpost.com/wp-dyn/content/article/2005/10/23/AR2005102301200_pf.html |date=November 25, 2016}} ''The Washington Post''. October 24, 2005. Retrieved on June 5, 2006.</ref> Nonetheless, in June 2008, the Army Corps of Engineers New Orleans District submitted a Deep-Draft De-authorization Study of the MRGO which stated that "an economic evaluation of channel navigation use does not demonstrate a Federal interest in continued operation and maintenance of the channel." Congress ordered the MRGO closed as a direct result.

Many of the levees have been reconstructed since Katrina. In reconstructing them, precautions were taken to bring the levees up to modern building code standards and to ensure their safety. For example, in every situation possible, the Corps of Engineers replaced I-walls with T-walls, which have a horizontal concrete base that protects against soil erosion underneath the flood walls.<ref name=Walls>{{cite news | first=Matt | last=Crenson | agency=Associated Press | url=http://www.constructionequipmentguide.com/story.asp?story=6589 | title=Levee Repairs to Be Finished By First Day of Hurricane Season | date=February 2, 2006 | access-date=May 12, 2008 | archive-url=https://web.archive.org/web/20060207184213/http://www.constructionequipmentguide.com/story.asp?story=6589 | archive-date=February 7, 2006 | url-status=live}}</ref>

Funding battles continue over the remaining levee improvements. In February 2008, the Bush administration requested that the state of Louisiana pay about $1.5 billion of an estimated $7.2 billion for Corps of Engineers levee work (in accordance with the principles of local cost-sharing required by Congress as early as the [[Flood Control Act of 1928]]), a proposal which angered many Louisiana leaders.<ref name=funding>{{cite news | title=White House Budget for Levee Work Riles Many Louisiana Elected Officials | agency=Associated Press | first=Cain | last=Burdeau | url=http://www.cegltd.com/story.asp?story=10045 | date=February 12, 2008 | access-date=May 12, 2008 }}{{Dead link|date=March 2024 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> On May 2, 2008, Louisiana Governor [[Bobby Jindal]] used a speech to The National Press Club to request that President Bush free up money to complete work on Louisiana's levees. Bush promised to include the levee funding in his 2009 budget but rejected the idea of including the funding in a war bill, which would pass sooner.<ref name=BushJindal>{{cite web | url=http://www.2theadvocate.com/news/18539869.html | title=Jindal asks Bush for levee cash | publisher=2theadvocate.com | first=Gerard | last=Shields | date=May 3, 2008 | access-date=May 12, 2008 | archive-url=https://web.archive.org/web/20080506102615/http://www.2theadvocate.com/news/18539869.html | archive-date=May 6, 2008 | url-status=live}}</ref>