**STATEMENT OF**

**DR. VIRGINIA BURKETT**

**CHIEF SCIENTIST FOR GLOBAL CHANGE RESEARCH**

**U.S. GEOLOGICAL SURVEY**

**U.S. DEPARTMENT OF THE INTERIOR**

**BEFORE THE**

**COMMITTEE ON ENERGY AND NATURAL RESOURCES**

**UNITED STATES SENATE**

**REGARDING FINDINGS OF THE U.S. CLIMATE CHANGE SCIENCE PROGRAM STUDY**

***SAP 4.7: Impacts of Climate Change and Variability on Transportation
Systems and Infrastructure: Gulf Coast Study, Phase I***

**May 13, 2008**

Mr. Chairman and Members of the Committee, as a Lead Author and Editor
of the U.S. Climate Change Science Program assessment of climate change
and its impacts on Gulf Coast transportation, I am pleased to present a
summary of our findings about trends in the physical environment and the
climate variables that have implications for the transportation sector.
I would like to acknowledge the other editors and co-authors of the
report, with whom I have collaborated over the past four years to
develop this broad regional assessment upon which my testimony is based
(CCSP 2008):

*Editors:* Michael J. Savonis (FHWA) and Joanne R. Potter (Cambridge
Systematics)

*Lead Authors:* Michael J. Savonis, Joanne R. Potter, Robert C. Hyman
(Cambridge Systematics), Barry D. Keim (Louisiana State University),
Thomas W. Doyle (USGS), Robert S. Kafalenos (FHWA), Kenneth J. Leonard
(Cambridge Systematics), Ron Hagelman (Texas State University),
Stephen B. Hartley (USGS), Matthew Sheppard (IBM), John H. Suhrbier
(Cambridge Systematics), Eric Lindquist (Texas A&M Univerisity), and
Jessica E. Tump (Cambridget Systematics)

*Contributing authors:* Claudia Tebaldi (National Center for Atmospheric
Research), Daniel M. Beagan (Cambridge Systematics), Alan Meyers
(Cambridge Systematics), Michael F. Wehner (Lawrence Berkeley National
Laboratory), Tamara G. Houston (NOAA), David T. Hunt (Cambridge
Systematics), Michael K. Maynard (Wilbur Smith Associates), Barbara
Fritsche (Wilbur Smith Associates), Russell H. Henk (Texas
Transportation Institute), Edward J. Seymour (Texas Transportation
Institute), Leslie E. Olson (Texas Transportation Institute) , Wesley R.
Dean (Texas A&M University), Ivor Van Heerden (Louisiana State
University), S. Ahmet Binselam (Louisiana State University), and Nanda
N. Srinivasan (Cambridge Systematics)

These authors collectively represent three Federal agencies, five
universities and research institutions, and two transportation planning
and engineering firms. In addition to the contributions from these
co-authors, the study was guided by a 16-member advisory committee
formally chartered by the Secretary of Transportation under the Federal
Advisory Committee Act of 1972. This committee included transportation
experts representing the various modes (e.g., rail, ports, highways) and
several additional physical scientists and risk assessment experts.

The Gulf Coast project was sponsored by the U.S. Department of
Transportation (DOT) in partnership with the U.S. Geological Survey
(USGS) under the auspices of the U.S. Climate Change Science Program
(CCSP). The study, Synthesis and Assessment Product (SAP) 4.7 titled
"Impacts of Climate Change and Variability on Transportation Systems and
Infrastructure: Gulf Coast Study, Phase I" is one of 21 "synthesis and
assessment" products planned and sponsored by the CCSP with the
Department of Transportation as the lead agency. This SAP was completed
by the CCSP in March 2008. This project demonstrates how our
understanding of climate change and other physical processes can be
integrated with knowledge of transportation engineering and planning to
produce an assessment of risks and vulnerability that is relevant to
this important sector of the U.S. economy.

The ultimate goal of this 3-phased research project is to provide
knowledge and tools that will enable transportation planners and
managers to better understand climate change and associated risks,
adaptation strategies, and tradeoffs involved in planning, investment,
design, and operational decisions. The objective of Phase I of this
project, which we have now completed, was to conduct a preliminary
assessment of the risks and vulnerabilities of transportation in the
region, after collecting and integrating the range of data needed to
characterize the region -- its physiography and hydrology, land use and
land cover, past and projected climate, current population and trends,
and transportation infrastructure. Subsequent phases will involve a more
detailed analysis. Phase II will involve an in-depth assessment of risks
to transportation in a selected location, reporting on implications for
long-range plans and impacts on safety, operations, and maintenance.
This phase will also develop a risk assessment methodology and identify
techniques to incorporate environmental and climate data in
transportation decisions. Phase III will identify and analyze adaptation
and response strategies and develop tools to assess these strategies,
while enumerating future research needs.

My comments this morning will focus on the major drivers of change in
the central Gulf Coast, considering the natural physical setting as well
as the historical and projected changes in climate. The Lead Author of
the study from the DOT, Mike Savonis, is with me to answer any questions
that you might have about potential impacts on the wide range of
transportation modes within the regions, such as pipelines, highways and
ports.

The Gulf Coast study area (Figure 1) includes 48 contiguous coastal
counties in four States, from Houston/Galveston, Texas, to Mobile,
Alabama. This region is home to nearly 10 million people living in a
range of urban and rural settings and contains critical transportation
infrastructure that provides vital service to its constituent States and
the Nation as a whole. It is also highly vulnerable to sea level rise
and storm impacts. A variety of physical datasets were compiled for
review and use by the project research team. Most of the spatial data
was organized in geographic information system (GIS) formats or "layers"
that can be used to assess the vulnerability and risks of the
transportation infrastructure in the study area and inform the
development of adaptation strategies. In cooperation with DOT's Bureau
of Transportation Statistics we developed a GIS that allows us to
overlay elevation, storm surge, census data, and other attributes of the
study area with transportation infrastructure.

The Central Gulf Coast region is a low-lying sedimentary coast with low
topographic relief; the great majority of the study area lies below 30 m
(100 ft) in elevation (Figure 2). Much of the central Gulf Coast region
is prone to flooding during heavy rainfall events, hurricanes, and
lesser tropical storms. Land subsidence is a major factor in the region,
particularly in the Galveston region and the Mississippi River deltaic
plain. Subsidence is influenced by both landform characteristics of
specific locations as well as by human activities, such as ground-water
withdrawals. Most of the coastline is also highly vulnerable to erosion
and wetland loss, particularly in association with tropical storms and
passing storm fronts. It is estimated that 56,000 ha (217 mi^2^) of land
were lost in Louisiana during Hurricane Katrina. Further, many Gulf
Coast barrier islands are retreating and diminishing in size. The
Chandeleur Islands, which serve as a first line of defense for the New
Orleans region, lost roughly 85 percent of their surface area during
Hurricane Katrina. As barrier islands and mainland shorelines erode and
submerge, human communities and onshore infrastructure in low-lying
coastal areas become more susceptible to inundation and destruction.

The central Gulf Coast study area's transportation infrastructure is a
robust network of multiple modes -- critical both to the movement of
passengers and goods within the region and to national and international
transport with:

-   27,000 km (17,000 mi) of major highways -- about 2 percent of the
    Nation's major highways -- that carry 83.5 billion vehicle miles of
    travel annually.

-   Pipelines, bulk terminals, and other infrastructure that receive and
    transport two-thirds of all U.S. oil imports. Pipelines traversing
    the region transport over 90 percent of domestic Outer Continental
    Shelf oil and gas. Approximately one-half of all the natural gas
    used in the United States passes through or by the Henry Hub gas
    distribution point in Louisiana.

-   The largest concentration of public and private freight handling
    ports in the United States, measured on a tonnage basis, which
    handle around 40 percent of the Nation's waterborne tonnage. Four of
    the top five tonnage ports in the United States are located in the
    region.

-   The center of U.S. transcontinental trucking and rail routes with
    one of only four major points in the United States where railcars
    are exchanged between the dominant eastern and western railroads.

-   The Nation's leading and third-leading inland waterway systems (the
    Mississippi River and the Gulf Intracoastal Waterway) based on
    tonnage and providing 20 States with access to the Gulf of Mexico.

-   61 publicly owned, public-use airports, including 11 commercial
    service facilities.

    All of these transportation modes are vulnerable in some way to the
    changes in climate that are anticipated in this region during the
    next 50 to 100 years. The relative vulnerability of facilities is
    dependent, in large part, on elevation and distance from the
    coastline.

The Gulf Coast, like much of the world, has experienced significant
changes in climate over the past century and is expected to change even
more rapidly during the next century (IPCC, 2007). The four key climate
drivers in the Central Gulf Coast region -- rising temperatures,
changing precipitation patterns, rising relative sea levels, and
increasing storm intensity -- present clear risks to existing
infrastructure. These factors can be incorporated into decisions that
enable communities to prepare for and adapt to changing climatic
conditions. The research team's assessment of historical and potential
future changes in these four variables draws on publications, analyses
of instrumental records, and models that simulate how climate may change
in the future.

Our assessment of the present climate and 20^th^ century trends was
built around climatic data from the United States Climate Division
Datasets (CDD) and the United States Historical Climate Network (USHCN).
Empirical trends and variability were analyzed for temperature and
precipitation at the CDD level for the climate divisions along the Gulf
Coast from Galveston, Texas, to Mobile, Alabama, including Texas Climate
Division 8, Louisiana Divisions 6-9, Mississippi Division 10, and
Alabama Division 8 (Figure 3).

Results from our analysis of temperature variability during 1905 to 2003
indicate that the 1920s or 1930s was generally the warmest decade for
the various Gulf Coast climate divisions (Figure 3). After a step down
in the temperature in the late 1950s, the coolest period occurs in the
1960s, while a warming trend is evident for all seven climate divisions
beginning in the 1970s and extending through 2003. Of the seven climate
divisions, LA6, LA8, and MS10 have slight but significant cooling trends
over the 98-year period of record. Precipitation variability shows that
the 1940s and 1990s were the wettest decades, while the 1950s was
generally the driest (Figure 4). Although all of the climate divisions
at least suggest long-term patterns of increasing rainfall, only MS10
and AL8 have significant trends.

A water balance model developed for the region suggests a long-term
trend of increasing annual runoff (Figure 5). Over the entire record
since 1919, there was an increase in rainfall that, combined with
relatively cool temperatures, led to an estimated 36 percent increase in
runoff. Modeled future water balance, however, suggests that runoff is
expected to either decline slightly or remain relatively unchanged,
depending upon the balance of precipitation and evaporation. Moisture
deficits and drought appear likely to increase across the study area,
though model results are mixed. These findings are consistent with the
Intergovernmental Panel on Climate Change (IPCC, 2007), which concludes
that it is very likely that heat waves, heat extremes, and heavy
precipitation events over land will increase during this century and
that the number of dry days (or spacing between rainfall events) will
increase. Even in mid-latitude regions where mean precipitation is
expected to decrease, precipitation intensity is expected to increase
(IPCC, 2007).

Sea level has risen more than 120 m (395 ft) since the peak of the last
ice age (about 20,000 B.P.) and over the 20^th^ century by 1-2 mm/year
(0.04-0.08 in/year). The rate of global sea level rise since 1963 is
estimated at 1.8 mm/year (0.07 in/year) (IPCC, 2007). More recent
analysis of satellite altimetry data for the period from 1993 to 2003
shows a global average rate of sea level rise of about 3.1 (2.4-3.8) mm
per year (0.12 in/year). Whether the faster rate since 1993 reflects
decadal variability or a long-term acceleration over the 20^th^ century
rate is unclear. There is high confidence, however, that the rate of
observed sea level rise was greater in the 20^th^ century compared to
the 19^th^ century (IPCC, 2007).

Changes in mean water level at a given coastal location are affected by
a combination of changes in sea level in an ocean basin and by local
factors such as land subsidence. Gulf Coastal Plain environments,
particularly in the central and western parts of the Gulf Coast study
area, are prone to high rates of land surface subsidence attributed to
soil decomposition and compaction, deep fluid extraction, and the lack
of sediment deposition. For example, the Mississippi River delta region
demonstrates relative sea level rates of 10 mm/year (0.40 in/year),
five-fold greater than the 20^th^ century rate of global sea level rise.
Subsidence rates for several Gulf Coast sites by previous investigators
range from a low of 0.27 cm/year (0.11 in/year) in the Big Bend region
of northwest Florida up to 2.39 cm/year (0.94 in/year) for coastal
Louisiana.

The scenarios of future climate referenced in our report were generated
by the National Center for Atmospheric Research (NCAR), a research
center lead by a consortium of universities and international
organizations, by using an ensemble of 21 different atmosphere-ocean
coupled general circulation models (GCM) for the Gulf Coast region.
Model results, climatic trends during the past century, and climate
theory all suggest that extrapolation of the 20^th^ century temperature
record would likely underestimate the range of change that could occur
in the next few decades. While there is still considerable uncertainty
about the *rates* of change that can be expected (Karl and Trenberth,
2003), there is a fairly strong consensus regarding the direction of
change for most of the climate variables that affect transportation in
the Gulf Coast region.

Climate models currently lack the detail needed to make confident
projections or forecasts for a number of variables, especially on small
scales, so plausible "scenarios" are often used to provide input to
decision making (Parson et al., 2007). Output from an ensemble of 21
GCMs run with the three emissions scenarios indicate a wide range of
possible changes in temperature and precipitation out to the year 2050.
The models agree to a warmer Gulf Coast region of about 1.5 °C ± 1 °C
(2.7 °F ± 1.8 °F), with the greatest increase in temperature occurring
in the summer. Based on historical trends and model projections, we
conclude that it is very likely that in the future the number of very
hot days will substantially increase across the study area. Modeled
outputs of potential temperature increase scenarios for August are
presented in Table 1. Extreme high temperatures could be about 1^o^C
(1.8 °F) greater than the change in the average temperature simulated by
the GCMs.

Scenarios of future precipitation are more convoluted, with indications
of increases or decreases by the various models, but the models lean
slightly toward a decrease in annual rainfall across the Gulf Coast.
However, by compounding changing seasonal precipitation with increasing
temperatures, average runoff is likely to remain the same or decrease,
while deficits (or droughts) are more likely to become more severe. Each
of the climate model and emissions scenarios analyzed in our report
represents plausible future regional conditions.

Increased tropical storm intensity is likely to accompany global warming
as a function of higher sea surface temperatures, which have been
observed globally (Webster et al., 2005; IPCC 2007). The kinetic energy
of tropical storms and hurricanes is fueled from heat exchange over warm
tropical waters. An increase in sea surface temperature (SST) from
global climate change is likely to increase the probability of higher
sustained winds per tropical storm circulation (Emanuel, 1987; Holland,
1997; Knutson et al., 1998). Sea surface temperature has increased
significantly in the main hurricane development region of the North
Atlantic during the past century (Bell et al., 2007) (Figure 6) as well
as in the Gulf of Mexico (Smith and Reynolds, 2004) (Figure 7).

Recent empirical evidence suggests a trend towards more intense
hurricanes formed in the North Atlantic Basin, and this trend is likely
to intensify during the next century (IPCC, 2007). In the Gulf region,
there is presently no compelling evidence to suggest that the number or
paths of tropical storms have changed or are likely to change in the
future.

Change in the rate of sea level rise is dependent on a host of
interacting factors that are best evaluated on decadal to centennial
time scales. Two complementary modeling approaches were applied in this
study to assess the potential rise in sea level and coastal submergence
over the next century. Both models were used to estimate relative sea
level rise (RSLR) by 2050 and 2100 under a range of greenhouse gas
emissions scenarios. Both models account for global sea level change as
estimated by the global climate models and also incorporate values for
land subsidence in the region based on the historical record. One model,
CoastClim, produces results that are closer to a simple measure of
future sea level change under the scenarios of future climate. A similar
model, SLRRP, also incorporates values for high and low tidal variation
attributed to astronomical and meteorological causes, which are pulled
from the historical record. The SLRRP model is rectified to the NAVD88
(North American Vertical Datum of 1988) that is commonly used by
surveyors to calculate the elevations of roads, bridges, levees, and
other infrastructure. The tide data used in the SLRRP model is based on
a monthly average of the mean high tide (called mean high water) for
each day of the month (Table 2). The SLRRP results capture seasonal
variability and interannual trends in relative sea level change, while
the CoastClim results do not.

The three long-term tide gauge locations analyzed in this study
represent three subregions of the study area: Galveston, Texas (the
chenier plain); Grand Isle, Louisiana (the Mississippi River deltaic
plain); and Pensacola, Florida (Mississippi/Alabama Sound) (Figure 8).
For each of these gauges, we examined potential range of relative sea
level rise through 2050 and 2100 using the SRES B1, A1B, A2, and A1FI
emissions scenarios based on the combined output of 7 GCMs. Results for
the year 2100 generated with CoastClim range from 24 cm (0.8 ft) in
Pensacola to 167 cm (5.5 ft) in Grand Isle. Results for the year 2100
from SLRRP (Table 3), which as noted above accounts for historical tidal
variation, indicate relative sea level rise in the range of 70 cm (2.3
ft, NAVD88) in Pensacola to 199 cm (6.5 ft, NAVD88) in Grand Isle.

Storm surge simulations accomplished basin-specific surge height
predictions for a combination of storm categories, track speeds, and
angled approach on landfall that can be summarized by worst-case
conditions to exceed 6 to 9 m (20 to 30 ft) along the central Gulf
Coast. Storm attributes and meteorological conditions at the time of
actual landfall of any storm or hurricane will dictate actual surge
heights. Transportation officials and planners within the defined study
area can expect that transportation facilities and infrastructure at or
below 9 m (30 ft) of elevation along the coast are subject to direct and
indirect surge impacts. Sea level rise of 1 to 2 m (3 to 6 ft) along
this coast could effectively raise the cautionary height of these surge
predictions to 10 m (33 ft) or more by the end of the next century.

Changes in climate can have widespread effects on physical and
biological systems of low-lying, sedimentary coasts. However, the large
and growing pressures of development are responsible for most of the
current stresses on Gulf Coast natural resources, which include: water
quality and sediment pollution, increased flooding, loss of barrier
islands and wetlands, and other factors that are altering the resilience
of coastal ecosystems (U.S. Environmental Protection Agency, 1999).
Human alterations to freshwater inflows through upstream dams and
impoundments, dredging of natural rivers and engineered waterways, and
flood-control levees also have affected the amount of sediment delivered
to the Gulf coastal zone. Roughly 80 percent of U.S. coastal wetland
losses have occurred in the Gulf Coast region since 1940, and
predictions of future population growth portend increasing pressure on
Gulf Coast communities and their environment. Sea level rise will
generally increase marine transgression on coastal shorelines and the
frequency of barrier island overwash during storms, with effects most
severe in coastal systems that already are stressed and deteriorating.
An increase in tropical storm intensity or a decrease in fresh water and
sediment delivery to the coast would tend to amplify the effects of sea
level rise on Gulf Coast landforms.

The global near-surface air temperature increase of the past 100 years
is approaching levels not observed in the past several hundred years
(IPCC, 2001). Regional "surprises" are increasingly possible in the
complex, nonlinear Earth climate system (Groisman et al., 2004), which
is characterized by thresholds in physical processes that are not
completely understood or incorporated into climate model simulations;
e.g., interactive chemistry, interactive land and ocean carbon
emissions, etc. While there is still considerable uncertainty about the
*rates* of change that can be expected (Karl and Trenberth, 2003), there
is a fairly strong consensus regarding the direction of change for most
of the climate variables that affect transportation in the Gulf Coast
region. Key findings from our analysis and other published studies for
the study region concerning future climate include:

**Warming temperatures** **--** All GCMs available from the IPCC (via
the Coupled Model Intercomparison Project 3) used in this study indicate
an increase in average annual Gulf Coast temperature through the end of
this century. Based on GCM runs under three different emission scenarios
developed by the IPCC Special Report on Emissions Scenarios (SRES) (the
low-emissions B1, the high-emissions A2, and the mid-range A1B
scenarios), the average temperature in the Gulf Coast region appears
likely to increase by at least 1.5°C ± 1°C (2.7°F ± 1.8°F) during the
next 50 years. Extreme high temperatures are also expected to
increase -- with the number of days above 32.2°C (90°F) very likely to
increase significantly across the study area. Within 50 years the
probability of experiencing 21 days a year with temperatures of 37.8°C
(100°F) or above is greater than 50 percent (Figure 9).

**Changes in precipitation patterns*** ***--** Some analyses, including
the GCM results from this study, indicate that average precipitation
will increase in this region while others indicate a decline of average
precipitation during the next 50 to 100 years. In either case, it is
expected that average soil moisture could decline, due to increasing
temperatures and resulting higher evapotranspiration rates. While
*average* annual rainfall may increase or decrease slightly, the
*intensity* of individual rainfall events is likely to increase during
the 21^st^ century.

**Rising Sea Levels --** Relative sea level is likely to rise between 1
and 6 ft by the end of the 21^st^ century, depending upon model
assumption and geographic location. The highest rate of relative sea
level rise will very likely be in the central and western parts of the
study area (Louisiana and East Texas) where subsidence rates are highest
(Table 3). Relative sea level rise (RSLR) is the combined effect of the
projected increase in the volume of the world's oceans (eustatic sea
level change), which results from increases in temperature and melting
of ice, and the projected changes in land surface elevation at a given
location due to subsidence of the land surface. The highest rate of
relative sea level rise will very likely be in the central and western
parts of the study area (Louisiana and East Texas), where subsidence
rates are highest (Table 3). The analysis of a "middle range" of
potential sea level rise of 0.6 to 1.2 meters (2 to 4 feet) indicates
that a vast portion of the Gulf Coast from Houston to Mobile may be
inundated over the next 50 to 100 years. The projected rate of relative
sea level rise for the region is consistent with historical trends,
other published region-specific analyses, and the IPCC 4^th^ Assessment
Report findings, which assumes no major changes in ice sheet dynamics.

**Storm Activity --** The destructive potential of hurricanes is likely
to increase as the sea surface temperature of the Atlantic and Gulf of
Mexico continue to rise. Rising relative sea level will exacerbate
exposure to storm surge and flooding. Depending on the trajectory and
scale of individual storms, facilities at or below 9 m (30 ft) could be
subject to direct storm surge impacts. Rising relative sea level will
exacerbate exposure to storm surge and flooding.

In the near term, the direction and scale of these modeled outcomes are
consistent regardless of the assumptions used for level of greenhouse
gas emissions. Model outputs are relatively similar across a range of
IPCC SRES emission scenarios for the next four decades. However,
long-range projections (modeled to 100 years) do vary depending upon
emission scenario, with the magnitude of impacts indicated being more
severe under higher-emission assumptions.

Based on findings from the USGS-led research team about the physical
setting and climatic trends, a regional-scale characterization of
impacts on transportation systems and infrastructure was led by the DOT.
The following summary of potential impacts is presented in the Executive
Summary of the report:

**Warming temperatures may require changes in materials, maintenance,
and operations.** The combined effects of an increase in mean and
extreme high temperatures across the study region are likely to affect
the construction, maintenance, and operations of transportation
infrastructure and vehicles. Higher temperatures may also suggest areas
for materials and technology innovation to develop new, more
heat-tolerant materials. Some types of infrastructure deteriorate more
quickly at temperatures above 32.2°C (90°F). As the number of very hot
days increases, different materials may be required. Further,
restrictions on work crews may lengthen construction times. Rail lines
may be affected by more frequent rail buckling due to an increase in
daily high temperatures. Ports, maintenance facilities, and terminals
are expected to require increased refrigeration and cooling. Finally,
higher temperatures affect aircraft performance and the runway lengths
that are required. However, advances in aircraft technology are expected
to offset the potential effects of the temperature increases analyzed in
this report, so that current runway lengths are likely to be sufficient.
The effects of increases in average temperatures and in the number of
very hot days will have to be addressed in designing and planning for
vehicles, facilities, and operations.

**Changes in precipitation patterns may increase short-term flooding.**
The analysis of future annual precipitation change based on results of
climate model runs is inconclusive: some models indicate an increase in
average precipitation and some indicate a decrease. In either case, the
hotter climate may reduce soil moisture and average run-off, possibly
necessitating changes in right-of-way land management. The potential of
changes in heavy rainfall may have more significant consequences for
transportation; more frequent extreme precipitation events may result in
more frequent flooding, stressing the capacity of existing drainage
systems. The potential of extreme rainfall events and more frequent and
prolonged flooding may disrupt traffic management, increase highway
incidents, and impact airline schedules -- putting additional strain on
a heavily used and increasingly congested system. Further, prolonged
flooding -- inundation in excess of one week -- can damage pavement
substructure.

**Relative sea level rise may inundate existing infrastructure.** To
assess the impact of relative sea level rise (RSLR), the implications of
rises equal to 61 cm and 122 cm (2 and 4 ft) were examined. As discussed
above, actual RSLR may be higher or somewhat lower than these levels.
Under these scenarios, substantial portions of the transportation
infrastructure in the region are at risk: 27 percent of the major roads,
9 percent of the rail lines, and 72 percent of the ports are at or below
122 cm (4 ft) in elevation, although portions of the infrastructure are
guarded by protective structures such as levees and dikes. While
protective structures will continue to be an important strategy in the
area, rising sea levels significantly increase the challenge to
transportation managers in ensuring reliable transportation services.
Inundation of even small segments of the intermodal system can render
much larger portions impassable, disrupting connectivity and access to
the wider transportation network.

**Increased storm intensity may lead to greater service disruption and
infrastructure damage.** This study examined the potential for flooding
and damage associated with storm surge levels of 5.5 m and 7.0 m (18 ft
and 23 ft). These modeled outputs are comparable to potential surge
levels during severe storms in the region: Simulated storm surge from
model runs across the central Gulf Coast demonstrated a 6.7- to 7.3-m
(22- to 24-ft) potential surge for major hurricanes. These levels may be
conservative; surge levels during Hurricane Katrina (rated a Category 3
at landfall) exceeded these heights in some locations. The specific
location and strength of storm surges are of course determined by the
scale and trajectory of individual tropical storms, which are difficult
to predict. However, substantial portions of the region's infrastructure
are located at elevations below the thresholds examined, and recent
storms have demonstrated that major hurricanes can produce flooding
miles inland from the location of initial landfall. With storm surge at
7 m (23 ft), more than half of the area's major highways (64 percent of
Interstates; 57 percent of arterials), almost half of the rail miles, 29
airports, and virtually all of the ports are subject to flooding.

Other damage due to severe storms is likely, as evidenced by the damage
caused by Hurricanes Katrina and Rita in 2005. Damage from the force of
storm surge, high winds, debris, and other effects of hurricanes can be
catastrophic, depending on where a specific hurricane strikes. This
studyI did not examine in detail these effects; the cumulative direct
and indirect impacts of major storms need to be further analyzed.
However, given the expectation of increasing intensity of hurricanes in
the region, consideration should be given to designing new or
replacement infrastructure to withstand more energy-intensive,
high-category storms.

Mr. Chairman, thank you for the opportunity to present the findings of
Phase I of the Gulf Coast study. I will be happy to answer any questions
that you and other Members of the Committee may have.

Table 1. Modeled outputs of potential temperature increase (°C \[°F\])
scenarios for August.

  -------------- ----------- ------------ ------------ -------------- ----------- ------------ ------------
  **Mid-Term                                           **Long-Term                             
  Potential                                            Potential                               
  (2050                                                (2100                                   
  Scenarios)**                                         Scenarios)**                            

  Temperature                                          Temperature                             
  Increase by                                          Increase by                             
  Scenario                                             Scenario                                
  Percentile: °C                                       Percentile: °C                          
  (°F)                                                 (°F)                                    

  **Scenario**   **5^th^**   **50^th^**   **95^th^**   **Scenario**   **5^th^**   **50^th^**   **95^th^**

  **A1B          1.6 (2.9)   2.5 (4.5)    **3.4        **A1B          3.0 (5.4)   3.9 (7.0)    5.0 (9.0)
  mid-range**                             (6.1)**      mid-range**                             

  **B1 low**     **0.9       1.8 (3.2)    2.6 (4.7)    **B1 low**     **1.8       2.7 (4.9)    3.6 (6.5)
                 (1.6)**                                              (3.2)**                  

  **A2 high**    1.1 (2.0)   2.3 (4.1)    **3.4        **A2 high**    3.3 (5.9)   4.7 (8.5)    **6.0
                                          (6.1)**                                              (10.8)**
  -------------- ----------- ------------ ------------ -------------- ----------- ------------ ------------

Note: Lowest/highest changes in bold.

**Table 2.** USGS SLRRP model results showing the mean land surface
elevations (cm \[NAVD88\]) subject to coastal flooding for the Gulf
Coast region by 2050 and 2100 under a high, mid, and low scenario based
on combined output for all seven GCM models for the A1FI, B1, A1B, and
A2 emissions scenarios.

<table style="width:100%;">
<colgroup>
<col style="width: 19%" />
<col style="width: 7%" />
<col style="width: 7%" />
<col style="width: 7%" />
<col style="width: 7%" />
<col style="width: 19%" />
<col style="width: 7%" />
<col style="width: 7%" />
<col style="width: 7%" />
<col style="width: 7%" />
</colgroup>
<tbody>
<tr class="odd">
<td><strong>Year 2050</strong></td>
<td colspan="4"><strong>Low</strong></td>
<td><strong>Year 2100</strong></td>
<td colspan="4"><blockquote>
<p><strong>Low</strong></p>
</blockquote></td>
</tr>
<tr class="even">
<td></td>
<td><strong>A1FI</strong></td>
<td><strong>B1</strong></td>
<td><strong>A1B</strong></td>
<td><strong>A2</strong></td>
<td></td>
<td><strong>A1FI</strong></td>
<td><strong>B1</strong></td>
<td><strong>A1B</strong></td>
<td><strong>A2</strong></td>
</tr>
<tr class="odd">
<td>Galveston, TX</td>
<td>83.0</td>
<td>80.9</td>
<td>83.4</td>
<td>83.4</td>
<td>Galveston, TX</td>
<td>130.7</td>
<td>117.0</td>
<td>124.9</td>
<td>127.0</td>
</tr>
<tr class="even">
<td>Grand Isle, LA</td>
<td>107.5</td>
<td>106.0</td>
<td>108.8</td>
<td>106.3</td>
<td>Grand Isle, LA</td>
<td>171.2</td>
<td>159.7</td>
<td>168.7</td>
<td>167.6</td>
</tr>
<tr class="odd">
<td>Pensacola, FL</td>
<td>48.0</td>
<td>47.8</td>
<td>48.4</td>
<td>53.7</td>
<td>Pensacola, FL</td>
<td>83.9</td>
<td>70.1</td>
<td>78.2</td>
<td>75.2</td>
</tr>
<tr class="even">
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
</tr>
<tr class="odd">
<td><strong>Year 2050</strong></td>
<td colspan="4"><blockquote>
<p><strong>Mid</strong></p>
</blockquote></td>
<td><strong>Year 2100</strong></td>
<td colspan="4"><blockquote>
<p><strong>Mid</strong></p>
</blockquote></td>
</tr>
<tr class="even">
<td></td>
<td><strong>A1FI</strong></td>
<td><strong>B1</strong></td>
<td><strong>A1B</strong></td>
<td><strong>A2</strong></td>
<td></td>
<td><strong>A1FI</strong></td>
<td><strong>B1</strong></td>
<td><strong>A1B</strong></td>
<td><strong>A2</strong></td>
</tr>
<tr class="odd">
<td>Galveston, TX</td>
<td>88.9</td>
<td>86.7</td>
<td>88.7</td>
<td>88.8</td>
<td>Galveston, TX</td>
<td>146.0</td>
<td>129.5</td>
<td>137.1</td>
<td>140.8</td>
</tr>
<tr class="even">
<td>Grand Isle, LA</td>
<td>113.6</td>
<td>111.8</td>
<td>114.2</td>
<td>111.8</td>
<td>Grand Isle, LA</td>
<td>185.3</td>
<td>171.4</td>
<td>180.2</td>
<td>181.3</td>
</tr>
<tr class="odd">
<td>Pensacola, FL</td>
<td>53.9</td>
<td>53.6</td>
<td>53.7</td>
<td>60.0</td>
<td>Pensacola, FL</td>
<td>99.2</td>
<td>82.6</td>
<td>90.3</td>
<td>89.3</td>
</tr>
<tr class="even">
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
<td></td>
</tr>
<tr class="odd">
<td><strong>Year 2050</strong></td>
<td colspan="4"><blockquote>
<p><strong>High</strong></p>
</blockquote></td>
<td><strong>Year 2100</strong></td>
<td colspan="4"><blockquote>
<p><strong>High</strong></p>
</blockquote></td>
</tr>
<tr class="even">
<td></td>
<td><strong>A1FI</strong></td>
<td><strong>B1</strong></td>
<td><strong>A1B</strong></td>
<td><strong>A2</strong></td>
<td></td>
<td><strong>A1FI</strong></td>
<td><strong>B1</strong></td>
<td><strong>A1B</strong></td>
<td><strong>A2</strong></td>
</tr>
<tr class="odd">
<td>Galveston, TX</td>
<td>94.8</td>
<td>92.5</td>
<td>93.9</td>
<td>94.3</td>
<td>Galveston, TX</td>
<td>161.3</td>
<td>142.0</td>
<td>149.3</td>
<td>154.5</td>
</tr>
<tr class="even">
<td>Grand Isle, LA</td>
<td>119.6</td>
<td>117.6</td>
<td>119.6</td>
<td>117.3</td>
<td>Grand Isle, LA</td>
<td>199.6</td>
<td>183.1</td>
<td>191.7</td>
<td>195.1</td>
</tr>
<tr class="odd">
<td>Pensacola, FL</td>
<td>59.8</td>
<td>59.4</td>
<td>58.9</td>
<td>66.3</td>
<td>Pensacola, FL</td>
<td>114.5</td>
<td>95.0</td>
<td>102.5</td>
<td>103.5</td>
</tr>
</tbody>
</table>

Table 3. SLRRP model parameters and results showing the mean sea level
rise projections for the Gulf Coast region by 2050 and 2100 under a
high, mid, and low scenario based on combined output for all seven GCM
models for the A1FI emission scenario.

  ------------------------ --------------- -------------------- -------------- -----------------------
  **Model Parameters**     **Scenarios**   **Louisiana-Texas\   **Louisiana\   **Mississippi-Alabama
                                           Chenier Plain**      Deltaic        Sound**
                                                                Plain**        

  Tide Gauge                               Galveston, TX        Grand Isle, LA Pensacola, FL

  Sea Level Trend (mm/yr)                  6.5                  9.85           2.14

  Subsidence (mm/yr)                       4.7                  8.05           0.34

  Sea Level Rise by 2050   High            94.8                 119.6          59.8
  (cm, NAVD88)                                                                 

                           Mid             88.9                 113.6          53.9

                           Low             83.0                 107.5          48.0

  Sea Level Rise by 2100   High            161.3                199.6          114.5
  (cm, NAVD88)                                                                 

                           Mid             146.0                185.3          99.2

                           Low             130.7                171.2          83.9
  ------------------------ --------------- -------------------- -------------- -----------------------

Figure 1. Map of the study area, which extends from Mobile, AL, to
Houston/Galveston, TX.

![](media/image1.png){width="4.233333333333333in"
height="3.0618055555555554in"}

Figure 2. Relative elevation of counties in the study area (delineated
in blue). All areas shown in bright orange are below 30--m elevation.
(Source: U.S. Geological Survey)

![](media/image2.jpeg){width="4.916666666666667in"
height="2.9069444444444446in"}

Figure 3. Temperature variability from 1905-2003 for the seven climate
divisions making up the Gulf Coast study area. The level of significance
in long-term temperature trend within each division was determined at α
≤0.05.

![](media/image3.png){width="6.146527777777778in"
height="6.933333333333334in"}

Figure 4. Precipitation variability from 1905 to 2003 for the seven
climate divisions making up the Gulf Coast study area. The level of
significance in long-term precipitation trend within each division was
determined at α ≤0.05.

![](media/image4.jpeg){width="6.147222222222222in"
height="6.850694444444445in"}

Figure 5. Variability and trends in model-derived surplus (runoff) and
deficit from 1919 to 2003 for the Gulf Coast study area.

![](media/image5.png){width="4.293055555555555in"
height="2.223611111111111in"}

Figure 6. Sea surface temperature trend in the main hurricane
development region of the North Atlantic during the past century. Red
line shows the corresponding 5-yr running mean. Anomalies are departures
from the 1971--2000 period monthly means.\
(Source: Bell et al., 2007)

![](media/image6.png){width="3.5833333333333335in"
height="1.6958333333333333in"}

Figure 7. Sea surface temperature trends in the Gulf of Mexico region
produced by using the ERSST v.2 database. The plot includes the SST
anomalies averaged annually, as well as the anomalies determined from
the averages for August only and the July-September peak of the
hurricane season. (Source: Smith and Reynolds, 2004)

![](media/image7.pct){width="3.7506944444444446in" height="2.525in"}

Figure 8. Tide gauge records and mean sea level trend line for three
northern Gulf Coast tide stations at Pensacola, FL, Grand Isle, LA, and
Galveston, TX, corresponding with the eastern, central, and western
coverage of the study area. (NOAA tide gauges).

![](media/image8.png){width="4.7131944444444445in"
height="4.997222222222222in"}

**Figure 9**. The current and future probabilities of having 1 to 20
days during the summer at or above 37.8 °C (100 °F) in or near Houston,
TX, under the A2 emissions scenario.

![](media/image9.png){width="4.083333333333333in" height="3.1875in"}

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