BY STEVE BALLOU
The threat and impact of natural disasters ARE nothing new, but this past year has been a not so subtle reminder that these are significant inescapable forces requiring study, understanding, and action. The fear that welled in my chest, even from the safety of a hotel room in Oregon, as I watched Katrina become a Category 5 hurricane advancing on the Gulf Coast proved well founded. Current spending on the far from complete recovery exceeds $34 billion, making it the most expensive natural disaster in U.S. history. And, with the loss of 1,300 lives, it is the deadliest since 1928. We were all witness to the destruction and the lack of anything even closely resembling an organized, efficient response. Now, six months later, the road to recovery and prehurricane normalcy is still without strategic road signs, just as the area was without literal signage after the storm. Most of the articles written about Katrina and governmental hearings focus on the failure of government at all levels to protect and rescue the citizens on the Gulf Coast, especially in New Orleans.
Most of the questions aimed at uncovering the failures of the federal response to Katrina imply that we let this happen. Various experts suggest that we should have been prepared for “The Big One” and that somehow the debacle of response and ongoing recovery should have been avoided. The preparation before, the destruction during, the ineffectual response afterward, and the pace of recovery since are interrelated issues that usually don’t include mention of climatology and geology, much less the impact civilization has had in these areas. If hindsight is 20/20, the leaders advocating rebuilding all that was New Orleans and hoping for a better outcome with the next big event are wearing mental blinders. Thousands of pages in detailed reports have been critical of the efforts at all levels of government. The rising storm surge of blame has been transformed into a sea of documents that outline steps for dealing with future natural disasters of this magnitude more effectively. As a geologist, a firefighter, and a FEMA responder, I believe we need to look at the big picture. In reality, we not only let this happen, but we created an untenable situation that continues to invite disaster.
In the fire service we like to think that our actions are the results of training, experience, the best information available, knowledge, and situational awareness-all predicated on the “risk vs. benefit” litmus test. Shouldn’t we apply similar philosophies to the decision-making process as we ponder where to go from here? The House of Representatives Bipartisan Committee Report on Katrina is titled “Failure of Initiative.” If a failure of initiative is the failure to act in the face of common sense and make the hard choices, then I agree.
Several factors go into the making of a disaster of this magnitude; to get the big picture, we need to examine the complete profile of Katrina. To do this, we need to understand the geology of the Gulf Coast and the climatic trends that influence the formation of such apocalyptic storms.
As children, most of us probably felt secure and safe in our homes despite certain dangers. Although dangers existed, they were usually viewed as manageable, especially when seen through the eyes, and evaluated with the reason, of a child.
Growing up in the Midwest on the tale of “Tornado Alley,” I learned at an early age to fear the power and potential for damage associated with the very same wind machine that transported Dorothy to Oz. It wasn’t long after this awareness took root that I learned the behaviors necessary to survive a tornado. The world and all its wonders became less static, and the comfort of a constant unchanging physical environment was gone forever.
GEOLOGIC ASPECTS
The Crescent City is built on a segment of the Mississippi River Delta. A series of seven distinct sedimentary lobes that have been actively forming for 5,000 to 6,000 years comprise this river-dominated delta. Lobes are formed when the sediment carried along by the river is deposited where it slows to meet the Gulf of Mexico. Sediment is dropped from suspension as flow slows, larger sand particles first, gradually grading into fine mud and clay, which make up much of the fertile flood plains that mantle southern Mississippi and Louisiana. Channels of the Mississippi River deposit sediment in a lobate formation in an area until the delta lobe piles up, forcing the channel to build out and eventually shift. Evidence suggests that there have been several major shifts in the distributory channels in this area over time. Channel relocation is a function of water following the path of least resistance with the steepest gradient (Figure 1).
 Figure 1 Channel Relocation. Photo courtesy of Liam Gumley, Space Science and Engineering Center, University of Wisconsin-Madison and the MODIS science team. |
This satellite view of the region shows the faint trace of past channels and reveals the extent and character of the modern delta. This sequence of deposition, accumulation, and channel abandonment results in a series of overlapping lobes that form new delta in an expanding arc. In flood, the Mississippi overflows its banks and deposits material above sea level, creating natural levees and new wetlands. Delta building is a dynamic process that continues to build as long as sediment supply exceeds the rate of erosion and sea-level rise. Periodic channel abandonment and relocation produce deposition in those areas while areas not being fed erode. Human activities have been and are altering the natural processes described.
The Mississippi has been channelized and dammed to the extent that much of the delta-building sediment has been shut off and lost before it gets to the mouth of the river. The Army Corps of Engineers has forced the Mississippi to maintain its present course, feeding the delta around New Orleans despite the river’s efforts to divert an ever-increasing amount of its flow to the Atchafalaya River at the Old River Lock site. Flow through the Atchafalaya River has increased to near a third of the Mississippi’s discharge and is thus building delta near Morgan City, west of New Orleans.
For nearly a century, the withdrawal of oil and gas from the area has, according to many experts, contributed to regional subsidence. Devoid of anthropologic activities, the Mississippi Delta is a sketchy place built on muds from floods and sedimentation; so much sediment has accumulated that the weight of the delta alone is causing the area to sink. According to an article in the August 2005 Geotimes: “Scientists agree that subsidence is occurring along coastal areas of Louisiana, Mississippi, Texas, and Alabama.”
Subsidence factors such as compaction, diminished sediment replacement, deflection of the lithosphere, and tectonic activity add to the human activities that jeopardize the viability of these coastal regions. The rate of subsidence is a subject of controversy, with rates varying from a few millimeters per year to as much as 1.5 meters per century. Subsidence translates into loss of buffering wetlands, with up to an acre inundated every 35 minutes, and 65 to 100 square kilometers per year over the past few decades. Thus, coastal areas in general, and New Orleans especially, is becoming increasingly vulnerable through the degradation of shorelines and wetlands.
CLIMATOLOGIC INFLUENCES
Combine our subsidence model with rising sea level, and the specter of catastrophe looms large. Although the fact that our atmosphere, land, and seas are warming is not in dispute, the debate concerning the cause, whether natural and cyclic or anthropomorphically enhanced, becomes moot.
As the seas warm, thermal expansion could contribute 50 percent of the projected rise, with glacial melt accounting for the rest. All theory aside, any increase in sea level will have dire consequences on a sinking, shrinking, evermore vulnerable delta.
The 2005 North Atlantic hurricane season was the most active and costly in 154 years of record keeping. The 26 named storms; 13 hurricanes; and Zeta, the latest forming tropical storm on record, are amazing enough, but the formation and landfall of three Category 5 storms were totally unprecedented. Hurricanes Rita and Katrina are the fourth and sixth most powerful storms. At 882 millibars, Wilma is the strongest hurricane ever recorded. What factors contributed to this record-breaking year? Was this year an anomaly or a hint of more to come? To answer these questions, it will help to understand how hurricanes form and the factors that influence their severity.
Hurricanes are heat engines that absorb heat from the oceans and convert it into gigantic organized storms. Warm moisture-laden air rises and increases with cooling, moisture content, resulting in cloud and localized storm formation. As the mass of warm clouds and storms takes shape and is pushed along by the trade winds, the characteristic spin is imparted through the Coriolis force, a result of our spherical planet’s rotation and storm movement at any vector departing the equator. Hurricanes form under specific conditions, constituting a “hurricane recipe” of sorts:
- Warm ocean temperatures of 80°F or greater,
- . Only form a minimum of 5° latitude from the equator to acquire spin, and
- Form in the absence of strong wind shear.
The present rise in global temperatures is apparent. Whether this trend continues remains to be seen and is the crucial element in the recipe, as temperature relates directly to the destructive potential of future hurricanes. A probable factor contributing to Rita and Katrina’s unusual behavior as they failed to weaken as quickly as past storms on approaching land was that warmer than normal waters along the coast continued to supply sustaining heat (Figure 2). The Sea Surface Anomaly chart (SSTA) shows that the sea temperatures offshore of Mississippi and Louisiana were 2 to 2.5°C above normal during Katrina. The possibility of steadily increasing temperatures is very real given the expected trend of recent global temperatures that have exceeded that based on historical data. Hurricane strength and destructive potential correlate directly to sea surface temperature. Katrina reached sustained speeds near 163 mph; according to projections, sustained winds could reach levels of 220 to 240 mph if SST rises near 90°F.
 Figure 2 Sea Surface Temperature Anomaly. Courtesy of the National Climatic Data Center U.S. Department of Commerce http://www.ncdc.noaa.gov/oa/reports/tech-report-200501z.pdf. |
Although the location of tropical storm development will remain a constant, barring any shift in the earth’s rotational axis, and increasing temperatures appear to be a given, the absence of wind shear is uncertain. Calm upper atmospheric winds allow tropical storms and hurricanes to develop into massive storms.
El Nino in the eastern Pacific causes rising air that spreads over the Caribbean and Atlantic, creating wind shear that tilts the growing columns of clouds that would become a hurricane if allowed to build vertically. The effects of a strong El Nino hinder the development of storms in the Atlantic that affect the Eastern and Gulf Coasts of the United States. The ability to accurately predict El Nino strength and area of influence is akin to reading tea leaves, according to many researchers.
The Atlantic Muli-decacal Oscillation (AMO) is an observed occurrence of oscillating periods of cooler than normal sea-surface water temperatures followed by warmer than normal decades. Figure 3 shows global ocean surface temperatures distribution and trend as we head into the next warm phase of the AMO. The last warm phase, which began in the 1940s, brought a dramatic increase in the number of storms that reached hurricane strength. That period of intensity lasted into the early 1960s. Clearly, we seem to be experiencing the incipient stage of the next warm phase.
 Figure 3 Global Ocean Surface Temperatures. Courtesy of http://www.aoml.noaa.gov/hrd/Landsea/atlantic/fig14.html. |
According to the Intergovernmental Panel on Climate Change (IPCC), in the past, “… the observed variations in the intensity and frequency of tropical and extra-tropical cyclones and severe local storms show no clear trends in the last half of the 20th century, although multi-decadal fluctuations are sometimes apparent.”
With regard to the future, the IPCC says: “There is little consistent evidence that shows changes in the projected frequency of tropical cyclones and areas of formation. However, some measures of intensities show projected increases, and some theoretical and modeling studies suggest that the upper limit of these intensities could increase. Mean and peak precipitation intensities from tropical cyclones are likely to increase appreciably.”
Most experts don’t predict a rise in the total number of storms but foresee an increase in the intensity of developing storms in the future. Clearly, coastal areas need be concerned about the continued potential for catastrophic storms that will cause increasing dramatic economic, environmental, and human losses. Serious consideration should go into any plan to rebuild coastal areas. Certainly, many areas of sensitive or commercial value are worthy of effort and cost, but planners need to be selective. The U.S. Army Corps of Engineers, the Federal Emergency Management Agency, and the U.S. Geological Survey have generated flood and storm-inundation potential maps legislators need take heed of as the subject of development is addressed. Not only are coastal populations and property vulnerable, but they are also subsidized by federal programs. Spending on coastal areas includes federal flood insurance, beach reclamation, and infrastructure that is rebuilt and maintained to promote coastal and barrier island development.
In the final analysis, filtered of political influence and anthropomorphic bias, future losses can be minimized. The ability to prevent the degree of catastrophe from Katrina was limited by tradition and culture, but other factors such as better planning and situational awareness must influence the decisions of development in coastal areas.
The Federal Government needs to take the lead in efforts to protect the interests of the nation pertaining to coastal development. We need a National Hurricane Policy and Coastal Development Policy that promote sustainable development and guarantee that safety standards are adhered to. Evacuation procedures and infrastructure must be adequate to allow egress from threatened areas. Even if the coming Atlantic Multi-decadal Oscillation produces storms of intensities and frequencies similar to those of the last warm trend, the dangers and economic losses will be unimaginable. The vulnerability of interests results from the combination of the coastward population migration, the untenable status of much of New Orleans and the Gulf Coast, and the possibility of sea-level rise. Although Katrina and the situation in the Gulf are the focus of this discussion, the same risks apply to all developed coasts.
The threats of vulnerability need to be at the forefront of any discussions concerning coastal development and rebuilding. Instead of focusing on improved response, we need the wisdom of risk vs. benefit and selective development as the proactive approach to an increasingly untenable situation.
STEVE BALLOU is a 23-year veteran of the Janesville (WI) Fire Department, where he serves as a shift commander. He is an instructor at Beloit College.
