The Times - Picayune

Louisiana's coastal parishes and other Gulf communities from Houston to Mobile should build higher and more resilient roads, bridges and other infrastructure to withstand more intense hurricanes and rainstorms, sea level rise and higher temperatures caused by global warming during the next 50 to 100 years, according to a draft report prepared by the federal Department of Transportation and the U.S. Geological Survey.

But Louisiana, largely in response to Hurricanes Katrina and Rita in 2005, may be ahead of other states. Transportation and hurricane-protection planners in Baton Rouge are already responding to concerns raised in the report, forging ahead with heat-resistant pavements and higher bridges and levees.

Elsewhere along the coast, transportation planners are only now considering the effects of climate change in the next 100 years, which could include as much as a 4-foot rise in sea level, a 10 percent increase in the intensity of hurricanes, a dramatic increase in the number of days with temperatures of 90 and 100 degrees or higher, and more periods of intense rainfall.

At risk are thousands of miles of roads, hundreds of bridges and dozens of airports that will be flooded more often or could be damaged by periods of high heat or more frequent hurricanes, or whose operations could otherwise be affected by climate changes, according to the report.

The report concludes that the combination of more intense hurricanes and higher sea levels also will expand the area facing potential storm damage, a concern because existing roadway capacity is not designed for large-scale evacuations.

"This preliminary assessment raises clear cause for concern regarding the vulnerability of transportation infrastructure and services in the central Gulf Coast due to climate and coastal changes," the report concludes.

The report states that transportation planners and managers could move now to begin adapting to climate changes but that few had done so until experiencing the effects of Hurricanes Katrina and Rita in 2005.

"This first study is a broad regional characterization of the coast's infrastructure and its vulnerability to climate change and sea-level rise," said co-author Virginia Burkett, a biologist with the U.S. Geological Survey's National Wetlands Research Center in Lafayette.

Once this report and two more that identify more localized impacts and potential solutions are completed, "the study will serve as a tool that can be used by state and local planners and policymakers when planning for the needs of existing and future highways, railways, ports, pipelines and other transportation systems," said Jan Brecht-Clark, co-chair of the Department of Transportation's Climate Change Center.

More detailed assessments of the effects by region, using detailed storm-surge modeling to identify specific bridges, roads, evacuation routes and other vulnerabilities, will be completed during the next few years.

Planning needed now

But planners need to immediately consider long-term climate effects when launching transportation projects because infrastructure built during the next 20 to 30 years will be in place for another 50 years, said one transportation planner and co-author.

"They'll be out there as the effects of climate change become more dramatic," said Ken Leonard, former transportation planning director for Wisconsin now with Cambridge Systematics Inc.

"The transportation community is very concerned about climate change," he said, "but it's too early to say whether their updated long-range plans will consider climate change."

Indeed, a survey of planning documents from state and local agencies in Alabama, Mississippi, Louisiana and Texas found that none "directly addresses or acknowledges issues of climate change and variability."

In large part, the report states, that is because most of the planning documents are two to four years old, written before climate-change impacts became better understood in the aftermath of Katrina and Rita.

In fact, release of the study was delayed for about two years after the authors decided it needed to take into account the effects of Katrina and Rita to more than three-quarters of the study area, Burkett said.

While it's unclear whether global warming had an impact on either hurricane, Burkett said the storms "serve to illustrate the kinds of effects we'll see in the future as sea level rises and storms become more intense."

The report uses future climate scenarios, developed by the National Center for Atmospheric Research in Boulder, Colo., based on an ensemble of 21 models of atmospheric and ocean conditions for the Gulf Coast.

Among the findings are that a vast area of the Gulf Coast from Houston to Mobile may be inundated during the next 50 to 100 years based on the study's understanding of the effects of relative sea-level rise driven by global warming.

The report uses a "middle range" of 2 feet to 4 feet of sea level rise for most of its predictions, with the biggest rises in south Louisiana and east Texas, which are most affected by subsidence.

Threat of inundation

The effects would not only be in Louisiana, where concerns about coastal inundation have been raised for years. The report states just a 2-foot rise in sea level would affect 137 miles of Interstate 10 to the east of New Orleans in Mississippi. The runways at New Orleans International Airport could be affected by a 4-foot rise.

The study warned, however, that its sea-level rise estimates are conservative, based on the assumptions in the most recent Intergovernmental Panel on Climate Change reports. Those reports do not include recent research indicating a more rapid rate of melting of polar ice sheets.

As global warming increases the temperature of surface water in the Atlantic and Gulf of Mexico, the report states, the intensity of major hurricanes may increase by 10 percent or more.

The result could mean more storms of at least Category 3 strength, with winds of 111 mph or more, hitting the coast. The storm surge they produce, combined with rising sea levels, could flood facilities 30-feet high or lower.

The Army Corps of Engineers has reached a similar conclusion about future sea-level rise and hurricane effects and is designing flood-control structures in eastern New Orleans and St. Bernard Parish to be as high as 32 feet above sea level by 2057.

But a storm surge of 18 feet threatens 98 percent of port facilities along the coast and a third of coastal rail lines.

The report does not address the effectiveness of existing flood controls, however, or of the planned 100-year hurricane protection for the New Orleans area by 2011. It also does not identify the effect of hurricane winds on transportation infrastructure.

But the potential effects of surge on transportation is real, based on damage estimates from Hurricane Katrina.

"Repair costs for the more than (40-mile) CSX railroad segment damaged in Hurricane Katrina, $250 million, could be dwarfed by the costs of moving the line if the company chose to relocate the line further inland," the report concluded, based on congressional proposals after the storm to authorize $700 million in federal money to do just that.

The effects of surge during Katrina to the Interstate 10 twin spans connecting New Orleans to Slidell and a similar bridge in Bay St. Louis, Miss., also have not been lost on transportation planners in Louisiana and Mississippi, despite the lack of national surge-based construction standards for such bridges, the report states.

Louisiana is developing standards calling for elevating new bridges above surge expected from a 500-year hurricane for main spans and a 100-year event for transition spans close to shore. Mississippi is considering similar standards.

Concerns are also rising about the effects of more frequent hurricanes on pipeline operations, as operators attempt to assure emergency response for breaks and spills in a hurricane's aftermath.

"One hazardous-liquid pipeline representative stated that, prior to Ivan, obtaining pipeline maintenance and repair contract commitments was relatively easy, 'a foregone conclusion of commitment,' but, after Katrina/Rita, it has become increasingly difficult to obtain solid commitments from suppliers to respond to emergency calls," the report states.

Today, the suppliers only commit to put the customer on a response list, for a fee, with no guarantee of a response.

Thermometer rising

Increased temperatures will be a nagging problem in the region, based on predictions from all of the climate models used in the study, with the average annual temperature expected to rise between 1.6 degrees and 4.5 degrees during the next 50 years.

It's likely that the highest-temperature days will cause the most problems. The report predicts a 50-percent chance for 21 or more days a year with temperatures of 100 degrees or above within the next 50 years in 48 Gulf Coast coastal counties.

Many highway-pavement materials degrade more quickly when temperatures remain above 90 degrees. The current average of 77 days per year when the temperature exceeds 90 degrees is expected to increase to between 99 and 131 days a year during the next century.

Those high temperatures could require a change in construction materials for both highways and railroads, as well as restrictions on work-crew hours that could lengthen construction times and increase costs.

In Louisiana, state roads are being built with new, more expensive high-polymer-content asphalts to offset the higher temperatures.

The report suggests that steel- and concrete-bridge designers may also need to begin rethinking their standards, as record highs threaten to meet maximum-design temperatures of 115 to 125 degrees during the next century. The longer periods of higher temperatures also are expected to affect aircraft performance, the report states. Warm air is less dense and decreases both lift and engine efficiency in aircraft, which could require longer runways and more powerful engines.

Some experts believe those problems might be offset by recent improvements in aircraft technology, however, the report states.

But in New Orleans, the problem for airports may be the requirements for higher levees and walls on their borders, based on recent statements by Army Corps of Engineers officials.

The corps is struggling to design a floodwall at Lakefront Airport that won't disrupt air-traffic patterns, and similar problems may crop up in the design of a levee or floodwall at the canal on the western border of Louis Armstrong International Airport in Kenner.

Downpours ahead

An increase in the number of intense rainfall events also could mean more frequent delays for commercial travelers and could force pilots of private aircraft to rely more often on instrument-only flying, or to avoid flying during storms.

Changes in precipitation patterns also have the potential to wreak havoc with the coast, and especially with the New Orleans area. While models indicate the chances of either an increase or decrease in total precipitation is a tossup, the intensity of individual rainstorms is expected to increase.

The more intense rainfall is expected to increase maintenance for roads, airstrips, bikeways, walkways and rail beds.

Higher average temperatures will increase direct evaporation and the amount of water consumed by plants, reducing the amount of water available for agriculture and other purposes.

The higher evaporation rates throughout the central United States could result in a lower water level in the Mississippi River, which could require either deeper dredging or restrictions on the weight carried by ships and barges.

Ironically, sea level rise might actually increase the depth of the river at its mouth, allowing more cargo.

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Mark Schleifstein can be reached at mschleifstein@timespicayune.com or (504) 826-3327.