How is coastal risk on the East and Gulf Coasts changing?

More people and property are in harm’s way

A 2013 study ranks eight U.S. cities among the world’s top 20 based on an estimate of potential average annual flood loss of valuable assets such as buildings, transportation, utilities, and personal property : Miami (#2), the New York-Newark region (#3), New Orleans (#4), Tampa-St. Petersburg (#7), Boston (#8), Philadelphia (#16), Virginia Beach (#17), and Baltimore (#19); (Hallegatte et al., 2013)

Hurricane Sandy was the latest wake-up call

Hurricane Sandy heightened the nation’s awareness of the vulnerability of coastal areas to hurricane damage. Damage was widespread and profound, as seen in this before and after picture in New Jersey.

Hurricanes dominate economic losses from disasters

Dollar losses due to tropical storms and floods have tripled over the past 50 years (accounting for inflation) and currently comprise approximately half of all natural disaster losses (Gall et al., 2011). Figure shows monetary damage (adjusted to 2013 dollars) by types of disaster for all billion-dollar disaster events between 1980 and 2012. Source: NOAA.

Economic losses from coastal storms have increased

From 1980 to 2013, coastal storm events causing billion-dollar losses (in 2013 dollars) increased from about 0.4 per year to more than one per year, and the losses increased from approximately $1.75 billion per year to as high as $45 billion per year in the 5-year span that includes Hurricane Katrina.

More people are moving into high hazard areas

Population growth along the U.S. east coast has been greatest in the areas where major hurricanes are most frequent: the Southeast coast and Gulf of Mexico. From 2000-2012, growth there has been 21% and 18%, respectively, compared to a national average of 11.5%. The red dots show areas where major hurricanes hit on average every 14-22 years, compared to other colored dots where major hurricanes hit less often.

Sea-level rise is increasing coastal risk

Globally, sea level has risen by an average of 3.1 mm per year over the past two decades. Local relative sea level rise rates (which consider rates of land subsidence) are much higher in northern and western Gulf of Mexico and the mid-Atlantic. Sea-level rise increases exposure to flooding and deterioration of beaches and wetlands.

Storm surge may have increased with global temperatures

Using six high quality tide-gauge records (dating to 1923) from the southeastern United States, one study (Grinsted et al., 2013) found that storm surge had increased with global temperature. The study identified a doubling of the likelihood of a Katrina-magnitude storm surge during the 20th century. Evidence grows that hurricanes will be more intense in the future.

Federal funds are paying more bills

The federal government’s assistance to disaster victims is well illustrated by the fact that, over the past 60 years, coastal-storm related Presidential disaster declarations have increased from approximately 1 to 10 per year. Source: FEMA

Federal aid has risen

Federal aid as a percentage of total damage has increased over the past 60 years, as exemplified by these five major tropical hurricanes. Source: Michel-Kerjan, 2013

Options for reducing risks

Coastal Risks can be managed by: (1) reducing the probability of coastal hazards (e.g., floods and wave attacks) using hard structures, such as seawalls, and nature-based strategies, such as beach nourishment and dune building, (left side) or conservation of natural dunes; (2) reducing the consequences of coastal hazards if they occur using design strategies, such as elevating buildings, and nonstructural strategies, such as land-use planning and emergency planning.

Dune building and beach nourishment are the most common strategies today

Many hard structures, such as seawalls and levees, were constructed by the USACE prior to 1970. As the adverse environmental impacts of those structures became clear, beach nourishment and dune building have become the most commonly used strategy.

Hard structures will become more important

Hard structures like this Fox Point Hurricane Barrier in Providence, Rhode Island, are likely to become increasingly important to reduce coastal risks, particularly in densely populated urban areas where space is often lacking to take advantage of nature-based strategies alone.

Strategies that reduce the consequences of storms are given less attention

Despite studies that show a high benefit-to-cost ratio for consequence-reduction strategies such as hazard zoning, building elevation, and land purchases, federal funds for such strategies from 2004-2012 were only about 5 percent of disaster relief funds. Land-use strategies are generally viewed as difficult to implement by state and local governments.

Incentives are needed to encourage new strategies

Stronger incentives are needed to improve pre-disaster planning and mitigation efforts at the local level.

Proactive, rather than reactive steps are needed.

New York, New Orleans, and Miami were poorly prepared for a major storm as shown by Hurricanes Sandy (2012), Katrina (2005) and Andrew (1992). To date, the nation has been reactive, with the vast majority of federal funding being provided only after disasters occur.

A national vision is needed

Effective coastal risk management for the United States requires a national perspective to achieve the most benefits from federal investments. A national risk assessment could identify where risks of human fatalities, economic losses, and social impacts are greatest and in need of targeted risk reduction interventions. Using benefit-cost analysis that takes into account acceptable risks to life-safety and social and environmental factors, the nation could target its investments to reduce coastal risk and enhance overall benefits.

More people and property are in harm’s way
Hurricane Sandy was the latest wake-up call
Hurricanes dominate economic losses from disasters
Economic losses from coastal storms have increased
More people are moving into high hazard areas
Sea-level rise is increasing coastal risk
Storm surge may have increased with global temperatures
Federal funds are paying more bills
Federal aid has risen
Options for reducing risks
Dune building and beach nourishment are the most common strategies today
Hard structures will become more important
Strategies that reduce the consequences of storms are given less attention
Incentives are needed to encourage new strategies
Proactive, rather than reactive steps are needed.
A national vision is needed

Read more about this report, Reducing Coastal Risks on the East and Gulf Coasts, at the website of the Water Science and Technology Board of the National Academy of Sciences.