Photo: National Oceanic and Atmospheric Administration
Remember those teachers who pushed you really hard? It’s usually only in retrospect that you come to realize that they actually taught you something. The harsh lessons of Hurricane Katrina felt more like punishment, and 10 years have not diminished the pain suffered then. But with the perspective of time, we can now perceive a silver lining: The experience transformed the way we plan and engineer flood protection — and indications are that new ideas are working. By most measures, the New Orleans delta region is more resilient and better prepared to withstand storms and floods than ever.
To make sure that such a disaster never happens again, engineers have gone to school on hurricanes, including Katrina. They have examined the ways storm surges form and grow in strength. This study has added to a more advanced body of knowledge on how to make coastal communities more resilient for the future. Other regions looking for ways to design water management systems can also learn a lot from Katrina. While few cities have geography quite like that in New Orleans, the very complexity of managing flood risk from ocean, river, lakes, and drainage canals makes the region a worthy study subject (Rogers, 2008).
New water-management strategies that emerged from the Katrina experience have made New Orleans more resilient, but their effects have reached much farther than the Crescent City. In fact, the hard lessons learned from the storm have influenced planners, engineers, policy makers, and federal agencies worldwide to rethink the ways they “protect” communities from storm surges, flooding, and hurricanes.
Resiliency lessons learned from Katrina
Lesson 1: Get organized — In the wake of a disaster, coordinating help and recovery can be a huge challenge. In response to the destruction from Hurricane Katrina, leaders quickly realized that a more integrated approach to building resilience into the Louisiana coastline made more sense than many individual efforts. The State of Louisiana created a team to plan and manage rebuilding, restoration, and resilience. Together, they worked to align the goals of citizens, utilities, industry, communities, nonprofits, and state and federal entities, plus all the many academic and professional planners and advisory resources.
The Coastal Protection and Restoration Authority (CPRA) worked with citizens and experts to develop the 2012 Louisiana Coastal Master Plan. ARCADIS and the RAND Corporation provided expertise on storm surge and risk assessment to support coastal water management strategies. The ideas, risk analysis, and planning that went into this planning created a unified, prioritized vision and set in motion construction of a comprehensive defensive infrastructure. After exploring hundreds of project ideas, the team identified the ones that offer the most benefit.
Wisely, the state is thinking long term. Work is poised to begin on the 2017 Master Plan development, which builds on the ideas and data made available from subsequent storms such as Hurricane Isaac.
Lesson 2: Redefine resilience — In the 21st Century, we pursue ways to mitigate the impact of storms across many criteria with the goal of achieving a quick recovery, not just defense. Before Katrina, flood defense was all about structures such as levees and barriers. But, though hard-engineered structures still play a critical role in defensive strategies, the enormity of superstorms such as Katrina and Rita brought home the fact that it may not be possible to create barriers against every eventuality. The truth is, there’s no practical way to prevent flooding, but there are ways to reduce its destructive force.
Philosophically, the idea of resilient communities now looks beyond infrastructure to a broader view that includes socioeconomic factors. One big lesson from these huge storms is that communities with social and financial resilience recover faster than those with infrastructure alone.
To advance resilience planning, the Rockefeller Foundation issued a 100 Resilient Cities Challenge with funding for cities to add a chief resilience officer (CRO). In November 2014, New Orleans named Jeff Hebert as the city’s CRO. He is already working to integrate planning and action to make New Orleans a more resilient city.
Lesson 3: Move fast — It can be difficult to move forward when so much planning still needs to be done, but building systems to be flexible and expandable will allow for priority projects to proceed so they can do their jobs as quickly as possible. After Katrina, the city faced so many equally important needs, it could easily have become overwhelmed. But a key decision was made to move forward with the most critical hurricane defense projects while broader planning continued.
The power of political will present in New Orleans and related federal agencies cannot be underestimated in rebuilding post-Katrina. The nation joined the engineering industry to align goals and move in one, focused direction.
The result was that even though the rest of the region’s hurricane infrastructure was still being built in 2012 when Hurricane Isaac hit, enough of the system was ready and able to prevent widespread flooding. Fast-tracking system levees, floodwalls, critical flood gates, and pump stations put them in place in time to deploy during that storm.
Lesson 4: Make a model — Understanding clearly what happened during Katrina helps engineers develop better resilience strategies. Data from Katrina and other Gulf storms, such as Ike and Gustav, contributed to state-of-the-art computer models that recreate how wind, storm surges, and tides behave and interact. These computer models provide ways to study and analyze risk. Over time, each additional storm produces new data that continually improves understanding.
These models can be used to run scenarios to test ideas for infrastructure designs or determining flood hazards such as a 1 percent likelihood hurricane storm surge. They also allow us to look at a range of possible future conditions, accounting for sea level rise and subsidence variations.
Even better, these storm surge models are behind the new National Oceanic and Atmospheric Administration (NOAA) storm surge warnings to be issued for hurricanes tracking toward the Louisiana coastline in the 2015 hurricane season. Warning systems have to be both accurate and fast. The old models were accurate, but were not fast enough to make the thousands of calculations needed to forecast a storm surge alert that people could act on. Harnessing the computing power of between 250 and 1,000 supercomputer cores running simultaneously enabled Louisiana and several other southeastern U.S. states to be able to pilot a storm surge warning system this year.
Lesson 5: Use multiple lines of defense — There is no magic bullet for universal flood protection. Multiple elements can address different aspects of flood control, working in concert as conditions develop and adding flexibility to the whole system. In New Orleans, the principle of multiple lines of defense is a key component in the Hurricane and Storm Damage Risk Reduction System (HSDRRS), which includes wetlands restoration and new green infrastructure, in addition to hard-engineered structures and levees.
A holistic system enables all the parts to perform different but related functions. For example, the West Closure Complex is a key part of the HSDRRS, helping to protect areas on the west bank of the Mississippi River. More importantly, this system helps prevent storm surges from overwhelming 26 miles of flood protection infrastructure along the Harvey (USACE, 2013) and Algiers (USACE, 2012) canals while evacuating interior rainfall from the protected areas.
System design starts with the perimeter you want to protect. Chances are, the system will work in multiple ways to prevent water from damaging critical infrastructure and moving water out quickly. A flexible, resilient system can handle more types of flood events and will speed recovery.
Lesson 6: Wetlands matter, so engineer with nature — Wetlands are critical not only as hurricane and flood barriers but also as a unique place for fishing and recreation. Numbers vary, but estimates of the economic importance of Louisiana wetlands range from $1 billion from a 1997 estimate, to another that states that the loss of these resources could cost the nation $36.6 billion from lost public use value over the next 50 years (Restore or Retreat, 2012).
Hurricanes Katrina and Rita washed away 217 square miles of coastal wetland in a month. Further erosion occurs at an estimated rate of a football field a day, resulting in more than 1.2 million acres of land lost since the 1930s (USACE-New Orleans District, 2015). As land is lost, saltwater incursions push farther inland, threatening the ecosystems that depend on fresh water.
While it’s nearly impossible to restore what’s been lost, current restoration efforts are working to at least keep pace with the rate of land loss. The key concept is to build with nature, not against it. New projects are diverting sediment from the Mississippi River to the delta and starting to stem the loss of wetlands. Sediment-rich fresh water from the river provides the delta with the mineral content necessary for wetlands to build upon to keep up with subsidence and sea level rise. ARCADIS recently helped the Army Corps design the White Ditch Freshwater and Sediment Diversion project to maximize delivery of valuable land-building sediments from the Mississippi River to support marsh habitat.
The Lower Barataria Sediment Diversion Project is an example of the State of Louisiana Coastal Protection and Restoration Authority’s larger, $50 billion program of coastal restoration and protection. Intended to rebuild the barrier islands, shoreline, and coastal marshes of Caminada Headland and Shell Island, the program is designed to restore both habitat and the sustainability of the shoreline itself. An integral component of the overall program, this project is expected to create 9,000 to 12,000 acres of wetlands over a 50-year period.
Lesson 7: Pump it up — Since most of New Orleans is below sea level — like a vast bowl — barriers alone can’t do the job of keeping water out. Heavy rain and leakage can still create flood risk, especially in low-lying areas of the city. Not only were the old pump stations not designed for Katrina’s rainfall and storm surge combination, in many cases, staff couldn’t remain onsite to operate them during the storm. Critical pump stations have been storm-proofed through the addition of redundant power supplies, hardening, and safe houses to protect workers during emergency operations. Their improved ability to remove rainwater or surge combine with levee armoring to provide a higher degree of resiliency and faster recovery.
In addition to the pump stations that have been repaired, upgraded, or that are being added, the West Closure Pump Station, the world’s largest pump station, can pump nearly 20,000 cubic feet per second (cfs) of floodwater from the Gulf over the closure barrier. This equates to a volume that would fill an Olympic-sized swimming pool in less than 21 seconds, and staff can remain onsite safely.
Lesson 8: Support the economy — The water surrounding New Orleans is both a threat and an economic engine. According to Greater New Orleans Economic Development authorities, by tonnage, the Greater New Orleans region is part of the largest port system in the world and the highest volume shipping port in the Western Hemisphere. As such, the region’s waterways support commerce not just for the Gulf, but throughout the eastern half of the United States.
Since blocking the flow of goods and commerce is not an option, all barriers meant to hold back floods also need to allow passage of shipping during the many months without a hurricane. Rather than build fixed barriers on the critical Industrial Canal and Gulf Intracoastal Waterway connecting Lake Pontchartrain, the Mississippi River, and Lake Borgne, planners built the Seabrook Sector Gate Complex to perform a dual role. When open, the three-story-high, steel-plated gates allow safe waterway navigation between Lake Pontchartrain and New Orleans’ Industrial Canal; however, when storms approach, the gates close, creating a continuous barrier blocking storm surges from the lake from entering the canal. Similarly, the Gulf Intracoastal Waterway – West Closure Complex includes a floodgate that opens for navigation on canals.
Lesson 9: Boost ROI with sustainable stormwater and groundwater management — You can’t control hurricane flooding without addressing everyday stormwater and groundwater management. Low-lying New Orleans experiences frequent rains that aren’t quite hurricanes, but that require regular stormwater management interventions. The Greater New Orleans Urban Water Plan (GNO, 2015) sought to integrate the traditional gray infrastructure of storm sewers and pipes with many green infrastructure strategies. These build on existing stormwater infrastructure, but use more of the landscape to store stormwater longer in retrofitted canals, ponds, and bioretentive green spaces such as rain gardens and bioswales.
Funded by the Louisiana Office of Community Development-Disaster Recovery Unit, the Urban Water Plan outlined the many ways stormwater management will benefit the city. This analysis shows that hurricane infrastructure in the form of green stormwater management delivers monetary value. The list of benefits includes $8 billion in repetitive flood costs over 50 years, a $2.2 billion reduction in reduced subsidence damage costs, $609 million in reduced flood insurance premiums, $183 million in increased property values, and significant economic impact in business and jobs.
The Sewerage and Water Board of New Orleans initiated a series of green infrastructure projects in 2014, including GIS analysis and needs assessment, multiple green infrastructure components, and volunteers to monitor and analyze the effects of the green infrastructure on stormwater runoff (SWBNO, 2015).
Lesson 10: Build for the future, not the last storm — This might be the biggest lesson of all from New Orleans. The next “Big One” may be bigger than any ever experienced. And sea level rise has changed the game for water management planning.
All of the modeling, planning, and risk assessment done after Katrina have informed projects around the world, and each storm experience builds on the last. In New York City, Hurricane Sandy woke up planners to the need to build to the 100-year level and beyond. As we learn more about sea level rise and subsidence, we also see how building to these higher standards will help communities stay ahead of these changes.
We also learned from Katrina that resilience planning is not a one-and-done proposition. Keeping this infrastructure relevant over time requires regular inspections and testing, coupled with an active maintenance schedule to keep systems in a state of readiness. This process includes periodic reassessment of flood threats and identifying any changes to risk, coupled with a review of new technologies and advancements in engineering that could be built into plans to improve overall risk reduction. Levee safety programs form a framework for long-term assessments and readiness, and results should be shared to allow communities to maintain an active role in risk management actions.
Much of post-Katrina planning in New Orleans and post-Sandy planning in New York have built on lessons learned in the Netherlands. But in many ways, knowledge has also flowed from the U.S. to the Netherlands as the country continues to improve its flood protection system. The Dutch Dialogues (dutchdialogues.com) were launched after Katrina to share approaches to water management, landscape architecture, flood protection, and urban design. Since then, these multi-disciplinary, cross-cultural interactions inspired similar discussions in New York, Tampa Bay, San Francisco, Taipei, Taiwan, and Aruba.
Perhaps the biggest lesson mega-storms like Katrina teach us is humility. We can design flood protection for specific ranges of conditions and risks, but risk will always exist. It is especially important to keep reminding the public of this, particularly over long periods of non-flooding, when complacency is the enemy. We also need to remember that even if our systems work perfectly nine years in a row, that outlier is always a threat. Despite our engineering advances, there will be a time when evacuation is required.
Like all infrastructure, water management is always a work in progress. Flexible designs allow for continued improvement without having to fund everything at once. New ideas will continue to come from all parts of the globe. And fortunately for many communities around the world, they, like New Orleans itself, will benefit from the lessons learned from Katrina.
Walter Baumy, national technical manager, ARCADIS, has developed specialized experience in flood risk management and is responsible for design and project delivery for water resource projects for ARCADIS clients. Previously, he worked more than 37 years with the U.S. Army Corps of Engineers, New Orleans District, most recently as chief, engineering division.