Will Similar Event as Hurricane Katrina Occur Again in the Future
Floods
After Katrina: Improved flood protection for New Orleans
The risk of flooding in New Orleans from hurricanes had been known for a long time. However, it was only subsequently the catastrophe wreaked by Hurricane Katrina that a reliable flood control system was developed on the basis of a comprehensive study.
17.08.2015
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A hurricane landfall on the Us Gulf Coast is not a rare consequence. Experts had long been aware that a disaster could happen in New Orleans: even in moderately astringent storms the region was susceptible to flooding – with corresponding risks for the people living there. Two years before the disaster, an commodity entitled "The Creeping Storm" appeared in the magazine Civil Technology, describing in detail how a hurricane could cripple New Orleans, and how such a disaster could be prevented. An emergency practise had even been conducted using as its centrepiece a hypothetical hurricane, Pam – a storm roughly equal to Katrina in intensity. With a comparatively short render period of 50 years, New Orleans was one of the regions in which disastrous flooding had to be expected. Neither American society in full general nor the local population was particularly concerned that no hurricane protection organisation had been completed for the city due to lack of funds. In any case, as an analysis conducted by the Interagency Performance Evaluation Task Force (IPET) prepare up after Katrina showed, it was based on outdated design criteria.
Hurricane Katrina: Levees were breached at more than than fifty places
Katrina tracked beyond the open up bounding main as a Category 5 hurricane, the highest in the Saffir-Simpson calibration used past the Us National Hurricane Centre. Its size and air current field were that of a monster tempest. It created a huge wind set-up in the water level long before it reached state. The water level rose by up to 7 metres along the east side of New Orleans and up to 9 metres forth the coast of Mississippi. Information technology was the largest tempest surge ever recorded in Northward America. A 200-km stretch of coastline was devastated by strong winds and flooding. In New Orleans, it was the flooding rather than the wind that caused the most damage. The city, which is virtually surrounded by water, was not equipped with sufficient alluvion protection to cope with the high surge level. The organisation failed, and dykes and flood walls e of New Orleans and forth the numerous canals leading into the urban center were breached at more than than 50 locations. The "bathtub" in which New Orleans is located was filled and remained flooded for over a month.
Research into the causes: Multiple failures
The storm surge was non the only crusade of the ending. Parts of the protection arrangement failed; some were besides depression, while others were either poorly designed, maintained or constructed. As a effect, the water was able to penetrate to the metropolis largely unhindered. Just it was the failure of organisational structures that magnified the event into a severe ending. The IPET was established in Oct 2005 in an try to understand what had gone wrong during Katrina and why. The aim of the scientists and engineers from various institutions was to analyse and assess the behaviour of the system during Katrina and to implement findings from this for the repair and reconstruction of the storm surge protection system in and around New Orleans.
© Munich Re, based on IPET 2009
Relative property loss for different return periods of flooding at 50% pumping chapters in 2005 pre-Katrina weather condition with the Hurricane Protection System (HPS) compared to today's state of affairs with the Hurricane and Storm Damage Take chances Reduction System (HSDRRS) in place. Coloured areas reflect the different drainage basins within the urban center.
Analysis based on 76 hypothetical hurricanes
The IPET report compares the flood hazard for New Orleans prior to Katrina with the risk following completion (in 2011) of the new Hurricane and Tempest Harm Adventure Reduction System (HSDRRS). The IPET team analysed the full range of possible hurricanes. The resultant water levels in various places (storm surge heights plus waves) were applied to the arrangement so that its operation could be studied. This also immune the reliability of the system to be assessed based on dissimilar design assumptions, and the squad could additionally gauge what areas would exist flooded to what depth at different levels of probability. From the 152 hypothetical hurricanes used for deriving the hazard distribution, 76 were chosen to define surge and wave weather for the actual risk analysis.
Levees, inundation walls, pumps
The Hurricane and Storm Damage Risk Reduction System (HSDRRS) that has been in place since 2011 reduces vulnerability to flooding for almost of the New Orleans region. Three specific measures:
- Higher and more resistant levees and flood walls were constructed throughout the region.
- Emergency pumps and canal closures were installed at the ends of the outfall canals.
- The pumps were designed to significantly reduce flooding heights in 100- and 500-year events. In turn, this reduces harm and the chance for the inhabitants.
Take a chance reduction of at least 75%
While some areas could still experience significant flooding and losses, the situation now represents the best structural risk mitigation status New Orleans has ever had. Given similar evacuation conditions to those seen in Katrina, the 2011 system is expected to reduce potential loss of life by every bit much as 86% without pumping and up to 97% with fifty% pumping for a 100-year flood event. It also markedly reduces potential for loss of life from a 500-year event (98%). Given the aforementioned property distribution and values that existed prior to Katrina, it would reduce straight property damage by 90% for a 100-twelvemonth flood outcome and by 75% for a 500-year event with l% pumping, compared to the pre-Katrina situation without pumping. It is impossible to avoid risk entirely, but with further improvements to the systems and additional technical and not-technical measures, such every bit flood-proofing and emergency plans, information technology tin at to the lowest degree be minimised.
Munich Re Experts
Wolfgang Kron
Head of Research, Hydrological Hazards in Geo Risks Research
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Source: https://www.munichre.com/topics-online/en/climate-change-and-natural-disasters/natural-disasters/floods/flood-protection-improval-new-orleans.html
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