Titus 1 

Does Sea Level Rise Matter to 

Transportation Along the Atlantic Coast? 

By Jim Titus 

Introduction 

steady barrage of studies and news 

reports about global warming has 

ensured that virtually all 

transportation planners realize that 

the transportation sector of the U.S. economy is 

an important cause of increasing concentrations 

of greenhouse gases. Less attention has been 

paid, however, to the effects of global warming 

on transportation—and virtually no attention has 

been paid to the ways by which our 

transportation infrastructure may impair our 

ability to adapt to the consequences of global 

warming. 

The focus on causes of global warming may 

be appropriate. The effects on climate of 

greenhouse gas emissions are not fully evident 

until roughly 50-100 years after they are 

released into the atmosphere, so it is generally 

understood that we have to reduce emissions 

now to mitigate the problem by 2050-2100.1 

Although the lead-time for roads and airports 

can be substantial, it is not 50-100 years; so why 

should a transportation planner worry about the 

consequences of global warming? 

Several plausible answers come to mind: 

First, because we have been releasing 

greenhouse gases for over a hundred years, the 

effects of past emissions are becoming more and 

more evident. For example, the sea is already a rising, so transportation activities that are 

sensitive to small rises in sea level already have 

a

 Global warming appears to be responsible for about 1 mm/yr of 

the current rate of sea level rise. 

to deal with the consequences. Second, some 

aspects of our infrastructure have long enough 

lifetimes to justify a consideration of long-term 

environmental changes like sea level rise. 

Finally, and perhaps most important: 

Transportation routes can channel development 

patterns for centuries, and thus, the ability of 

coastal regions to adapt to climate change during 

the next century and beyond may be helped or 

hindered by the decisions that transportation 

officials make today. 

The fact that climate change may affect the 

outcome of today’s decisions does not, however, 

prove that those impacts are important enough to 

consider today. Ultimately, it’s a question of 

magnitude. The data show that the 

transportation sector contributes about 27 

percent of U.S. greenhouse gas emissions,

 2

 so 

DOT clearly needs to think about emissions. 

But no one has assessed the extent to which 

today’s decisions leave our transportation 

infrastructure vulnerable to climate change. 

This paper is part of a DOT process to 

motivate adaptation to climate change in the 

U.S. transportation sector. In this paper, I lay 

out the implications that seem important enough 

to think about, both as a first step toward a 

comprehensive assessment of how the 

transportation sector can adapt to sea level rise, 

and hopefully, to motivate some decision makers 

to recognize those cases where they need not 

await such an assessment before beginning to 

take appropriate measures. 

The Potential Impacts of Climate Change on Transportation 
2 Does Sea Level Rise Matter to Transportation Along the Atlantic Coast? 

Some Background Facts the Atlantic Coast. Considering the effects both 

subsidence and greenhouse gases, sea level is 

Other discussion papers and presentations most likely to rise by about 2 feet along most of 

explain what scientists know about the causes the Atlantic Coast. There is a 1- percent chance 

and effects of global warming, and of a 4-foot rise, and a 95% chance that the sea 

projections of future sea level rise. To will rise more rapidly in the next century than in 

recap: Sea level is already rising along the U.S. the last century.

4

coast; see Figure 1. IPCC estimates that global

sea level will rise 9 to 88 cm during the 21st Rising sea level inundates low areas, erodes

century.

3 Because of regional subsidence, the beaches and wetlands, increases flooding from

rise will be 15-25 cm greater in parts of the mid- storm surges and rainstorms, and enables

Atlantic, and 5-15 cm greater elsewhere along saltwater to advance upstream. All of these

Figure 1. Sea level trends along the U.S. coast, 1900-2000. This map shows all sites with at least 50 years of data. 

The greatest sea level rise is shown in Louisiana (at the Mississippi delta), in Texas (near Galveston), and along the 

mid-Atlantic coast. The estimates are based on a linear regression of sea level on time, using data collected by the 

National Ocean Service and provided to the Permanent Service for Mean Sea Level in the United Kingdom. 

The Potential Impacts of Climate Change on Transportation 
Titus 3 

effects can have impacts on transportation. 

Figure 2 shows the approximately 60,000 square 

kilometers of land along the U.S. Atlantic and 

Gulf Coasts that lies below the 5-ft (NGVDb

) 

contour, which is roughly within 2-3 feet above 

the ebb and flow of the tides.c

 Louisiana, 

Florida, Texas, and North Carolina account for 

more than 80 percent of the lowest land. 5 

Outside of those four states, the largest 

vulnerable populated region is the land along the 

Eastern Shore of Chesapeake Bay stretching 

from Dorchester County, Maryland to Accomac 

County, Virginia. Most of the U.S. Pacific 

Coast is on relatively high ground, although 

there are some low areas along San Francisco 

Bay. In addition to these lands, erosion can 

threaten relatively high ground within a few 

hundred feet of a tidal shore. 

Global warming also increases flooding in 

the coastal zone. Storm surges from hurricanes 

and northeasters

d

 will build upon a higher base, 

and hence reach farther inland. Moreover, 

higher sea level slows the rate at which areas 

drain, so rainstorms will also tend to cause 

greater flooding in coastal areas. Furthermore, 

because a warmer atmosphere can hold more 

water vapor, rainstorms are getting more intense, 

which may further increase flooding. In 

addition to flooding and lands loss, sea level rise 

e enables saltwater to advance farther upstream. 

The actual effect of sea level rise depends on 

what people do in response to the direct physical 

responses. There are three fundamental 

response pathways: hold back the sea with dikes 

and other structures; hold back the sea by 

b

 The National Geodetic Vertical Datum of 1929 is used as the 

reference elevation for most topographic maps, although it is 

gradually being replaced. Along the East Coast, mean ocean sea 

level is about 8 inches above NGVD, largely because of sea level 

rise since 1929. Back barrier bays tend to have a mean tide level 

of about 1 ft. NGVD. c

 The ocean tide range tends to be about 5-6 feet; in the estuaries 

along barrier islands the range is much less, while some harbors 

have much greater tide ranges. The surge from a 100 year storm is 

close to 20 feet in parts of Florida, but more on the order of 8-10 

feet in the Mid-Atlantic and 5 feet in many estuaries. d A number of reports on the EPA Sea Level Rise Reports web 

page examine the issue of increased flooding and saltwater 

intrusion. Go to www.epa.gov/globalwarming/sealevelrise . e A number of reports on the EPA Sea Level Rise Reports web 

page examine the issue of increased flooding and saltwater 

intrusion. Go to www.epa.gov/globalwarming/sealevelrise . 

elevating the land surfaces and other structures, 

and allow nature to take its course and 

accommodate as necessary. As a general 

proposition, holding back the sea with dikes and 

other structures results in a large-scale 

elimination of wetlands, beaches, mudflats, and 

other coastal habitat; but the environmental 

consequences may be minor in areas where this 

habitat has already been destroyed. Elevating 

land surfaces maintains the status quo and 

generally preserves the narrow fringing wetlands 

and beaches; whether there is a large-scale loss 

of vegetated wetlands depends on whether the 

effort to elevated land surfaces extends to those 

areas. Retreat usually has the least 

environmental impact, because human activities 

are not squeezing intertidal ecosystems between 

the rising water and the coastal development;

f 

but it can have the greatest impact on 

communities whose residents have to move. As 

we discuss below, transportation considerations 

may often affect which path society takes in its 

response to rising sea level. 

Direct Effects of Sea Level Rise on 

Transportation 

Navigation 

Sea level rise makes water deeper, which 

enables deeper draft vessels to navigate a 

particular channel. This effect, however, is 

fairly small compared with the draft of most 

vessels. Saltwater advancing upstream can alter 

the point at which flocculation leads to 

sedimentation and the creation of shoals. 

Similarly, the clearance under bridges decreases. 

In a few cases where clearances are extremely 

tight, this effect could limit the ability of boats 

to pass underneath a bridge, particularly in the 

case of very small boats slowly passing 

underneath very small bridges, where the 

clearance may be less than a foot. Larger 

vessels are less likely to be impeded, because 

most bridges over key shipping lanes are either 

drawbridges or have very high spans. (A few 

low bridges have been deliberately located to 

f

 A number of reports on the EPA Sea Level Rise Reports web 

page provide estimates of the impact of holding back the sea on 

wetlands and beaches. 

The Potential Impacts of Climate Change on Transportation 
4 Does Sea Level Rise Matter to Transportation Along the Atlantic Coast? 

Figure 2. Map of lands close to sea level along the U.S. Atlantic and Gulf Coasts. Although the results nominally 

are in meters, the 1.5 meter contour is primarily based on the 5-ft NGVD contour from USGS topographic maps. 6 Source: Titus and Richman (2001). 

prevent large ships from passing farther 

upstream.

g

) 

Port facilities are on the water’s edge, and 

therefore potentially vulnerable to sea level rise. 

Docks, jetties, and other facilities are 

deliberately set at an optimal elevation relative 

to the water level and therefore a rise in sea level 

leaves them at a suboptimal elevation. 

However, these facilities tend to be rebuilt 

g

 An example of a low bridge that prevents large ships from 

proceeding farther upstream would be the bridges over the 

Mississippi River in Baton Rouge. 

relatively frequently compared with the time it 

takes for a substantial rise in sea level.7 

Sea level rise can also have important 

indirect effects on navigation, which we discuss 

below. 

Aviation 

Sea level rise is not likely to be a serious 

problem for a mode of transportation that is 

miles above the sea. Still, coastal cities such as 

Boston, New York, and Washington tend to 

have airports built along tidal waters, sometimes 

on filled areas. Therefore, their runways are 

The Potential Impacts of Climate Change on Transportation 
Titus 5 

vulnerable to flooding. A dike already protects 

New York’s LaGuardia airport, but other 

airports might experience increased flooding as 

the sea rises, or have to take protective 

measures.

 8 Changes in storms could also affect 

airports—but no one knows the direction of the 

likely change. 

Rail and Tunnels 

Railroads often cut across marsh areas in the 

coastal zone. In the case of some smaller shortline railroads, tracks are so low that they are 

often flooded, and the beds may be vulnerable to 

sinking from compaction of marsh peat. Thus, 

as the sea rises, some tracks will be more 

vulnerable to flooding. 

Tunnels may also become more vulnerable, 

both because the risk of their entrances and 

vents flooding will be greater, and because the 

hydraulic pressure on the tunnel walls increases 

as water tables rise. 

The New York Metro Area rail and subway 

system appears to be particularly vulnerable. A 

number of East Coast railroads have been in 

their current locations for 150 years, during 

which time the sea has risen 1.5-2 feet. Many 

tracks, signals, and stations are low enough to be 

flooded during severe storms. Many subway 

entrances are in the 100-year floodplain, and are 

occasionally flooded by northeasters.

9 

Roads 

The most important impact of sea level rise on 

transportation concerns roads. In many lowlying communities, roads are lower than the 

surrounding lands, so that land can drain into the 

streets. As a result, the streets are the first to 

flood. In some barrier island communities, the 

lowest bayside streets are already flooded during 

spring high tides. As the sea rises, this flooding 

will become more and more frequent. Most 

roads are not flooded by the tides, and have 

some type of drainage system to convey water 

away during rainstorms. As sea level rises, 

these drainage systems become less effective, 

causing more flooding—and increased rainfall 

intensity will further increase the severity and 

frequency of flooding there. 

Whether street flooding is a serious problem 

or a minor nuisance depends on a variety of 

factors. In recreational areas during the summer, 

a flooded street is often a source of 

entertainment for people who came to that 

community to be on the water.

10,h During cold 

weather or severe storms, however, some of 

these roads may be critical evacuation routes. 

Increased flooding increases evacuation times, 

which either increases the risk to life or requires 

emergency officials to require evacuation 

sooner, including for storms where it later 

becomes evident that evacuation was 

unnecessary. 

Some roads are threatened by erosion. In 

some cases, the loss of a road parallel to the 

shore may remove the only road access to a 

particular area. 

Transportation Adaptive Responses 

to Sea Level Rise 

When one attempts to describe the impact of sea 

level rise on transportation without describing 

the adaptive response, one is generally implicitly 

assuming that the community does nothing 

about sea level rise, that is, that it is simply 

allowing nature to take its course. But that is 

only one of many possible options, and in 

developed areas where most transportation 

occurs, it is probably the least likely option. 

That does not mean, however, that sea level rise 

has no impact on transportation—but it is very 

different than the impact from passively 

allowing the situation to deteriorate. Moreover, 

transportation considerations may often play an 

h

 See Bergen Record, “Rise in sea level likely to increase N.J. 

floods,” Wednesday, September 04, 2002 (by Alex Nussbaum). 

“Two days a month... Barnegat Bay creeps over the sea wall at the 

end of 28th Street in Ship Bottom... Like clockwork, water backs 

up through storm drains and trickles down the dead-end street that 

runs between a half-dozen summer homes. Local kids grab their 

inner tubes and float down the block. Carried by the tide, a few 

confused crabs wander the pavement. Some days, it's a full-fledged 

creek. Others, it's merely a puddle around the storm grates.... 

Laurence Delorme said he has to tie his garbage cans down to keep 

them from floating off during these tides. ‘It gives me beachfront 

property twice a month,’ jokes Delorme, 33. ‘The kids splash in 

it.’" 

The Potential Impacts of Climate Change on Transportation 
6 Does Sea Level Rise Matter to Transportation Along the Atlantic Coast? 

important role in the actual response to sea level 

rise. Let us consider the three fundamental 

pathways, in turn. 

Elevate Land and Structures 

Roads 

Many developed barrier islands and other low 

lying communities will probably respond to sea 

level rise by bringing in fill to elevate the land.i 

If the streets are elevated by the amount that the 

sea rises, flooding will be the same as it is today. 

In some cases, this may be less expensive than 

keeping streets at the current elevation. When 

streets are repaved, it is often necessary to 

remove the old pavement down to the roadbed, 

and haul away that material. Simply repaving 

on top of the existing road saves a step, at least 

for slow residential streets. On the other hand, 

high-speed roads may require additional fill and 

reconstruction of the roadbed. 

An important advantage of simply elevating 

the land is that the location of the roads do not 

have to be changed. Moreover, many types of 

drainage systems will continue to work properly, 

because the head gradient between street level 

and the sea remains the same. An important 

exception may be the underground runoff 

storage systems found in some communities, 

such as Atlantic City. Those tanks are currently 

above sea level and hence can gravity drain; if 

the sea rises and the tanks are below sea level, 

they would need to be retrofitted with check 

valves, and perhaps even pumps. Eventually, of 

course, a higher street would allow for higher 

tanks; but elevating the streets may be advisable 

as a near-term measure, whereas reconstruction 

of the tanks may not be necessary for many 

decades. 

i

 Eight New Jersey towns on barrier islands have signed 

agreements with EPA pledging to prepare for the consequences of 

rising sea level. All of those agreements stated that the particular 

towns find the dike and retreat options as unacceptable, and hence 

the communities’ only viable option is to gradually elevate land 

and structures. For an analysis of Long Beach Island, see 

“Greenhouse Effect, Sea Level Rise, and Barrier Islands: Case 

Study of Long Beach Island, New Jersey”, Coastal Management, 

18:65-90 (1990). 

Another advantage of elevating lands is that 

transportation planners do not have to anticipate 

long-term sea level rise; they simply need to 

keep up with the rise as it occurs. When roads 

become flooded, they can be elevated; but it is 

probably not necessary to design most roads for 

future conditions because roads can generally be 

repaved to a higher elevation as flooding gets 

worse, as part of the ordinary program of 

repaving. And there may be problems from 

making a street too high relative to the 

surrounding lands. 

However, some advance notice may be 

necessary in those communities that rely on the 

streets to drain the land. For example, Ocean 

City, Maryland requires lots to have at least a 2 

percent grade so that all property can drain into 

the street, to prevent standing water and the 

resulting breeding habitat for mosquitoes. If the 

town elevated the streets a foot, some streets 

would drain into people’s yards, which would 

essentially contravene the town’s policy. 

Therefore, as the sea rises, the town tolerates 

increased flooding in the few streets that are low 

enough to frequently flood. For all practical 

purposes, the lowest lot on the block dictates the 

street elevations for all. Therefore, the town 

may have to give people some notice that in the 

future they need to elevate their lots— 

eventually, low lots can not be a reason to not 

elevate the street; instead, an elevated street 

must trigger the requirement to elevate the lot. 

The situation in Ship Bottom, Long Beach 

Island, New Jersey also illustrates the need to 

look into the future. One of the key 

thoroughfares is flooded by spring tides as long 

as there has been at least modest rainfall and 

hence inflow into the estuaries. The county 

spent tens of thousands of dollars to retrofit a 

street drain with a check valve, which prevents 

the street drain from backing up into the street 

(unlike numerous side streets to the south). 

However, during several months of the year, 

spring tide (about 1.5 feet above mean tide level) 

overtops the surrounding land and floods the 

streets anyway (see Figure 3). Confused crabs 

are often seen walking down the street as the 

tide recedes. Elevating the street will eventually 

be necessary—forcing the homeowners to 

The Potential Impacts of Climate Change on Transportation 
Titus 7 

Figure 3. Photo of flooded street in Ship Bottom, New Jersey. This area tends to be flooded during spring high 

tides except for drought years, when nearby Barnegat Bay is lower than usual. The author took this photo on Labor 

Day 2002 during a neap tide with a northeaster whose 25kt winds from the East had elevated the ocean levels by 

approximately one foot. 

elevate their yards or be flooded by rainwater. 

Local governments must ask themselves whether 

retrofitting a drainage system with a checkvalve 

is a wise use of limited funds if the rising sea 

will require the street to be elevated anyway; by 

contrast, the checkvalve is almost certainly a 

useful first step in an area that must eventually 

be diked. 

Of course, if areas are going to be elevated, 

then the roads may have to accommodate 

increased dump truck traffic. 

Air, Rail, Shipping, Tunnels 

Just as roads can be elevated, so can runways 

and railroad beds. New bridges and tunnels can 

be built higher than would otherwise be the case. 

For example, recognizing the logic of 

anticipating sea level rise, the designers of the 

new causeway to Prince Edward Island made it 

one meter higher than it would otherwise have 

been. But existing structures will remain at 

current elevations. Therefore, even communities 

that are elevated may have increased seepage 

into tunnels and reduced clearance under 

bridges. 

The Potential Impacts of Climate Change on Transportation 
8 Does Sea Level Rise Matter to Transportation Along the Atlantic Coast? 

Navigation in tidal waters will be 

automatically elevated by the amount of sea 

level rise, but one has a choice with canals. If 

water levels are elevated by the amount of sea 

level rise, canal drainage will remain the same, 

although bridge clearance will reduce. 

Protect with Dikes 

If a community will be protected with a dike, the 

roadways do not need to be elevated, but 

otherwise, planners have a great deal more to be 

concerned about, because the response cannot be 

purely incremental as with elevating the land 

surface. If a dike will eventually be constructed, 

it’s important to make sure that there is a road 

parallel to the shore fairly close to the shore, 

preferably seaward of all construction. Such a 

road could be the location of the eventual dike 

system, which may include not only a dike but 

also a drainage canal and road for dike 

construction and maintenance. Without such a 

roadway, the public authority will have to 

purchase shorefront lands for the dike, and 

perhaps demolish waterfront homes. 

Once land is protected by a dike, the 

problem of street flooding from tidal and storm 

surges will be abated. However, rainwater 

flooding can become worse because the barriers 

that keep the sea out also keep rainwater in. 

Even before the dike is built, road engineers 

need to consider its eventual construction. For 

example, street drains in some areas are only 

rebuilt about every 100 years. If a dike is likely 

to be built in the next 100 years with streets kept 

at current elevations, the eventuality of check 

valves, pumping stations, and increased 

underground storage may imply a different 

optimal configuration for the drain pipes, 

especially if a large number of outfalls would be 

replaced by a smaller number of pumping 

stations, or if the pumping stations would be 

located somewhere different from existing 

outfalls. Because the best way to rebuild a 

drainage system depends on whether the land 

will be elevated or protected by dikes, municipal 

engineering departments need to know 

whether—and preferably when—the city will 

elevate the land surfaces or protect with dikes. 

Ideally, the leaders of a community will 

decide with appropriate input whether—and 

how—to hold back the sea and transportation 

planners can act accordingly. Because most 

communities have not yet made those decisions, 

however, the decisionmaking may flow in the 

opposite direction: Road planners do what they 

do, with or without a consideration of sea level 

rise, and decades later the status quo that the 

transportation infrastructure created will be a 

primary determinant of the community’s 

ultimate decision. Even if the retreat option is 

preferred, the existence of an important road 

along—and close to—the shore may make 

holding back the sea the only realistic option. 

Even if a dike would have been less expensive 

than elevating the land, the absence of a shoreparallel road may make land acquisition costs 

too costly or politically impossible. Therefore, 

if a community does not have a long-term sea 

level rise plan, anyone planning infrastructure 

with a long lifetime becomes—by default—the 

sea level rise planner who must either make an 

assumption about whether and how the sea will 

be held back, or ignore the situation and design 

the system as if the sea was not rising. 

Highway reconstruction may also dictate 

responses to sea level rise if there is no plan. As 

the sea rises, roads through undeveloped low 

areas tend to become dikes unless there is an 

explicit decision to convert it to a causeway. 

The roadway may have been originally elevated 

to prevent flooding; but as the sea rises and 

shores retreat, tidal waters reach the road—and 

the road blocks the flow of water, acting as a 

dike. Later, communities may build upon this 

initial de facto dike and create a complete dike 

system. Alternatively, the road authority may 

install culverts under the roadway, or make 

occasional breaks in the dike with bridges, to 

allow water to flow around the road, essentially 

converting the road to a causeway. 

Air, Rail, and Tunnels 

Dikes can reduce the effective length of a 

runway. Assuming a typical descent angle of 3 

degrees and that the runway stretches all the way 

to the dike, a one foot rise in sea level 

effectively shortens the runway by 20 feet. This 

The Potential Impacts of Climate Change on Transportation 
Titus 9 

is not too serious for a typical 10,000-foot 

runway. 

Dikes along with effective pumping systems 

can largely solve the existing and projected 

vulnerability of low-lying railroads within the 

urban areas that are protected. Increased 

hydraulic head may be a problem for tunnels in 

areas where the water table continues to rise 

with the sea; but an effective drainage system 

would keep the water table from rising. 

How Inclusive is the Dike? 

Perhaps the most serious problem with the dike 

option is the fact that because it is not 

incremental, one must decide which areas are 

within the dikes and which areas are outside of 

the dikes, and such decisions may be continually 

revisited. New highways might logically avoid 

low areas that are not going to be protected with 

dikes. But that may be a moving target. 

A key question regarding dikes is whether to 

dike the coast as it is today, or to follow the 

Dutch approach of shortening the coast. The 

basic idea behind shortening the coast is that it 

may be safer and much less expensive to build a 

large dike across the mouth of a bay, than to 

build smaller dikes along all the shores of the 

bay and its tidal rivers and creeks. Because 

existing ports would now be inside the dike, 

either ships would have to pass through locks, or 

new deepwater ports would be built outside the 

dike. Such an approach seems unlikely in the 

United States, both because of the environmental 

consequences and our nation’s general 

preference for small, uncoordinated 

infrastructure projects over large, coordinated 

efforts. 

Nevertheless, the basic principal of coast 

shortening will probably be applied in a number 

of areas. First, in areas with finger canals for 

recreational boaters, it would be impractical to 

dike all shores. Dikes around the entire 

communities with locks at the main stem of the 

canal would be more feasible, assuming that the 

communities are not elevated with fill. Second, 

storm surge barriers such as the Thames River 

Barrier have the effect of shortening the 

coastline during storm surges, but they generally 

stay open and hence need not interfere with 

navigation. Finally, large-scale water projects 

have some similarities with coast-shortening 

dikes. In the Everglades and Dismal Swamps, 

one must choose between elevating the canal 

waters by the amount of sea level rise, or 

keeping canals at current elevations. 

The sea will rise for the foreseeable future— 

perhaps even more rapidly during future 

centuries than the 21st century. In theory, we 

might elevate low lands forever as the sea rises. 

Holding back the sea, however, may become 

progressively more difficult. At first, tide gates 

and check valves allow water to drain at low 

tide; later, communities would need pumps. As 

the sea continues to rise, a community would 

have to pump more and more water due to 

greater infiltration, and the water would have to 

be pumped to higher locations. The dikes would 

probably have to be elevated by more than the 

sea level rise, because the impact of a dike 

failure would be far greater if the sea was 10 feet 

above Main Street than if it was only 2 feet 

above the town. This concern may be an issue 

for Louisiana, where the eroding shores are 

bringing the Gulf of Mexico closer every year to 

New Orleans, which is already below sea level. 

But for the Atlantic Coast, these are issues for 

future generations. 

Retreat and Accommodation 

Just as a dike can avert many impacts of sea 

level rise on transportation, so a retreat strategy 

can be very similar to the direct effect of 

ignoring the issue and addressing the 

consequences. In some areas that are destined to 

be abandonedj

, it may not make sense to make 

additional investments in transportation so as to 

prevent the consequences of sea level rise. 

Some of the roads to Delaware Bay in 

Cumberland County, New Jersey, are very 

rough, and there is little reason to fix them 

because much of the coastal zone of that county 

is being returned to nature. Roads along the 

j

 Several communities have used EPA funding to develop maps 

illustrating which areas will be protected and which will be 

abandoned. 

The Potential Impacts of Climate Change on Transportation 
10 Does Sea Level Rise Matter to Transportation Along the Atlantic Coast? 

retreating shores of the undeveloped Outer 

Banks are washed out during storms and rebuilt 

inland; roads along developed areas are also 

washed out in storms, but rebuilt and 

maintained—and given minimal protection such 

as a few dump truck loads of sand to act as a 

sacrificial dune for the next moderate storm. 

Although lightly developed areas may 

retreat without advance planning, a retreat policy 

requires a substantial degree of planning in more 

densely developed areas. With no dikes planned 

and the land surfaces not being elevated, street 

flooding gets worse and worse; but that flooding 

can be mitigated by increasing the size of 

ditches and other maintenance that is probably 

worthwhile even in an area that will be given up 

to the sea. Ironically, it may be particularly 

important to elevate highways as evacuation 

routes, because such areas will become more 

and more vulnerable, and will probably remain 

inhabited until a catastrophic storm destroys 

most structures. 

Just as shore-parallel roads are important for 

areas that will be diked, areas that will retreat 

need roads that are not shore-parallel. If 

someone’s only access is a shore-parallel road, 

then as soon as one part of the road is washed 

out, she loses access even if her property is a 

long way from being lost. Put another way, 

shore-parallel roads tend to thwart a retreat 

policy, even if it would otherwise be desirable. 

Although a retreating ocean shore requires 

oceanfront roads to be abandoned or relocated 

inland, the submergence of lands along an 

estuary does not necessarily mean the road will 

be abandoned. As an extreme example, consider 

US-64 and US-264, which connect the Outer 

Banks to the population centers of North 

Carolina. As Figure 4 shows, a large portion of 

the Albemarle-Pamlico Peninsula is low enough 

to be submerged with a significant rise in sea 

level. But the Outer Banks will continue to be 

viable and popular beach resorts, as far as we 

know, and less vulnerable to complete 

inundation than the peninsula. Therefore, those 

coastal planners who have thought about the 

issue expect that a small number of communities 

on the peninsula will be protected, the Outer 

Banks will survive, and people will continue to 

drive there. Figure 5 illustrates the thinking of 

these planners, which implies that US-64 and 

264 will become a combination of causewaystyle bridges, filled causeways, and isthmuses 

with the highway and some development on 

either side, connecting the various small towns 

with the mainland, each other, and the Outer 

Banks. This map is just one possibility: perhaps 

one of the highways will instead determine the 

location of a dike. But currently, retreat is 

taking place and there is a universal consensus 

in the state that US 64 and 264 will continue to 

exist. Many developed barrier islands are 

connected to the mainland with roads that pass 

through low-lying marsh that may become open 

water in the future. 

The retreat policy will have only minor 

impacts on navigation on the East Coast, which 

fortunately does not have the problems facing 

Louisiana, where solving land loss will probably 

require a reconfiguration of shipping lanes. To 

be sure, retreating barrier islands are difficult to 

reconcile with inlet stabilization projects, both 

politically and geologically. Hence Oregon 

Inlet, along North Carolina’s retreating Outer 

Banks, still has not been stabilized. In most 

cases, however, the areas where the inlets have a 

lot of boat traffic have populated barrier islands 

where retreat is unlikely; while retreating barrier 

islands are found in areas with relatively little 

boat traffic. 

Figure 6 shows these various options being 

put into effect in North Carolina. Figures 6a and 

6b demonstrates retreat and accommodation in 

Kitty Hawk and Elizabeth City. Figure 6c 

shows a dike-protected community, while Figure 

6d pictures homes being elevated. 

Assessment Options 

This cursory examination shows that sea level 

rise can have important impacts on roads, and 

that how we plan our roads can have an 

important impact on how coastal communities 

deal with sea level rise. The serious impacts of 

sea level rise on shipping appear to be limited to 

Louisiana, where a multiagency process is 

already underway to develop a long-term plan of 

The Potential Impacts of Climate Change on Transportation 
Titus 11 

Figure 4. Map of lands close to sea level in North Carolina. Source: Titus and Richman. (2001). 

The Potential Impacts of Climate Change on Transportation 
12 Does Sea Level Rise Matter to Transportation Along the Atlantic Coast? 

Figure 5. Draft maps illustrating the areas where North Carolina state coastal planners expect people to hold back 

the sea. Areas depicted in brown are almost certain to be protected with beach nourishment, fill, or some form of 

structure. Areas in blue represent privately owned land that the state planners do not expect to be protected. Areas 

in red represent land that probably will be protected, but where protection is less likely than the areas in brown. 

For example, along the barrier islands north of Corolla, the Coastal Barrier Resources Act prohibits federal 

assistance. Although property values may be sufficient to justify beach nourishment to hold back the sea, the 

absence of federal funding makes such projects less likely than in similar areas that are eligible for federal funding. 

These maps are being revised to reflect the local expertise of county governments, who generally expect more areas 

to be protected. Source: Walter Clark, North Carolina Seagrant. 

The Potential Impacts of Climate Change on Transportation 
Titus 13 

(a) 

(b) 

The Potential Impacts of Climate Change on Transportation 
14 Does Sea Level Rise Matter to Transportation Along the Atlantic Coast? 

(c) 

(d) 

Figure 6. Photos of four ways to respond to sea level rise in North Carolina. (a) Retreat along the Southern 

portion of Kitty Hawk: houses on stilts being abandoned to the sea; (b) Accommodating the higher water levels in 

Elizabeth City: a house on stilts is still occupied in this inlet; (c) A dike protects the Gum Neck agricultural 

community in Tyrrill County; and (d) Every home in sight is being elevated along this road in Carteret County. All 

photos taken the week of Columbus Day, 2002. 

The Potential Impacts of Climate Change on Transportation 
Titus 15 

action. The implications for railroads and 

airports seem to be more limited, but potentially 

very amenable to long-term planning for sea 

level rise because of the relatively small number 

of decisionmakers, compared with roads. 

Unfortunately, the impacts of sea level rise 

on transportation have not been quantified. 

Some types of guidance probably do not need 

quantitative assessments to prove meritorious; 

but a complete absence of quantitative evidence 

makes it difficult to be sure that the impacts of 

sea level rise on transportation are serious at a 

national scale. Therefore, an obvious next step 

would be to conduct a few relatively targeted 

assessments just to quantify the scope of the 

problem, including: 

1. A GIS assessment to quantify roadmiles, 

miles traveled, railroad miles, and railfreight 

under various definitions of vulnerable area 

(e.g., within one meter above the ebb and 

flow of the tides, within one meter of the 10-

year flood, within the area that might either 

be inundated or eroded as the sea rises). 

2. Overlay through areas within 1-meter above 

the ebb and flow of the tides (or where that 

form of elevation data does not yet exist, 

below the 5 and 10-ft contour) and the 

coastal floodplain. 

3. Overlay areas where planners expect people 

to hold back the sea, and areas that planners 

expect to be abandoned. 

4. Identify the roads in the coastal zone that are 

currently flooded by tides. 

5. Initiate a stakeholder outreach program with 

coastal highway departments to determine 

what kind of help they need from DOT to 

factor sea level rise into their planning. 

1

 Intergovernmental Panel on Climate Change. 2001. “Climate Change 2001: The Scientific Basis”. Cambridge and New York: 

Cambridge University Press. 

2

 U.S. Environmental Protection Agency. 2002. Inventory of U.S. Greenhouse Gas Emissions and Sinks. Washington, D.C. U.S. 

Environmental Protection Agency:. EPA 430-R-02-003 

3

 Intergovernmental Panel on Climate Change. 2001. “Climate Change 2001: The Scientific Basis”. Cambridge and New York: 

Cambridge University Press. 

4

 EPA. 1995. “The Probability of Sea Level Rise,” www.epa.gov/globalwarming/sealevelrise 

5

 Titus, J.G. and C Richman. 2001. “Maps of Lands Vulnerable to Sea Level Rise: Modeled Elevations along the U.S. Atlantic 

and Gulf Coasts.” Climate Research, CR 18:205-228. 

6

 Titus, J.G. and C Richman. 2001. “Maps of Lands Vulnerable to Sea Level Rise: Modeled Elevations along the U.S. Atlantic 

and Gulf Coasts.” Climate Research, CR 18:205-228. 

7

 National Academy of Engineering, Marine Board. 1987. Responding to Changes in Sea Level. Washington, D.C.: National 

Academy Press. 

8

 Jacob, K.H., N. Edelblum, and J. Arnold. 2000. “Risk Increase to Infrastructure due to Sea Level Rise.” In Climate Change 

and a Global City: An Assessment of the Metropolitan East Coast Region. Washington, D.C.: United States Global Change 

Research Program. 

9

 Jacob et al. supra note 10 at 17-30. 

10 Nussbaum, Alex. Bergen Record, “Rise in sea level likely to increase N.J. floods,” Wednesday, September 04, 2002. 

The Potential Impacts of Climate Change on Transportation 
16 Does Sea Level Rise Matter to Transportation Along the Atlantic Coast? 

Jim Titus, J.D., directs EPA’s Sea Level Rise project, whose continuing mission is to accelerate the 

process by which the U.S. coastal zone prepares for the long-term consequences of rising sea level. 

The Potential Impacts of Climate Change on Transportation