Coastal Issues | Coastal Hazards
Coastal Hazards
"As the coasts become increasingly populated, more and more people are placed in harm's way. Thus far, science has not found effective ways to reduce most hazards. Therefore, citizens must look to strengthening communities. Building safer buildings and strengthening infrastructure are important steps, but it is the manner in which societies are built that largely determines disaster resilience. A vital part of effective disaster planning—whether for mitigation, preparation, response, or recovery—is an understanding of the people and institutions that make up each community, including their strengths and their weaknesses, as a basis for developing policies, programs, and practices to protect them. In the end, it is human decisions related to such matters as land use planning and community priorities that will build stronger, safer, and better communities."
— H. John Heinz III Center for Science, Economics and the Environment, 2002, "Human Links to Coastal Disasters"
Hurricane Ike caused significant damage on Bolivar Peninsula in Texas in September 2008.
The U.S. coast is susceptible to a variety of natural hazards, including coastal storms, flooding, coastal erosion, tsunamis, and land subsidence. All of these hazards threaten lives, property, the natural environment, and, ultimately, economies—a problem that becomes more pressing as coastal populations continue to rise. Although coastal counties comprise only 17 percent of the nation's land area, they are home to over half the U.S. population. In 2003, 153 million people lived along the coast, 33 million more than in 1980.
Intensive development in the coastal zone not only places more people and property at risk to coastal hazards, but it also degrades the natural environment, interfering with nature's ability to protect the human environment from severe hazard events. For instance, seawalls accelerate beach erosion and inhibit the beach's ability to absorb storm energy, thus exposing buildings to the full force of wind and waves. Development can also destroy wetlands that serve as important buffers again storm surge and other types of flooding. So, while nothing can be done to prevent coastal hazard events, their adverse impacts can be reduced through proper planning.
Significant coastal hazards include:
Coastal Storms
Coastal storms take many forms and occur throughout the year. All coasts experience coastal storms and are susceptible to storm-related losses.
Katrina's high winds and a storm surge exceeding 30 feet destroyed this beachfront structure in Pass Christian, Mississippi (December 2005).
Tropical storms and hurricanes (typhoons) are intense summer storms. The main threats associated with these hazards are storm surge, high winds, heavy rain, and flooding, as well as tornadoes.
The North Atlantic hurricane season is from June 1 to November 30 and peaks between August and October. An average hurricane season features approximately 11 named storms. This includes six hurricanes, two of which are major. In the Eastern Pacific, the hurricane season runs from May 15 through November 30 and peaks between July and September. An average season includes 15 tropical storms, of which 9 become hurricanes and 4 become major hurricanes.
The 2004 Atlantic hurricane season was one of the worst on record. However, 2004 was quickly surpassed by 2005, the most destructive hurricane season on record. The 2005 season included 28 named storms, including 15 hurricanes, 7 of which were major (Category 3 or higher). Four major hurricanes made landfall along the U.S. coast. Combined, they caused an estimated $170 billion in damage and approximately 2,000 deaths. Hurricane Katrina alone, which came ashore as an extremely large Category 3 storm and ranks as the costliest U.S. storm on record, caused roughly $134 billion in damage and 1,833 fatalities. The effects of all of these storms, as well as the devastating storms of 2008, are still being felt, and will be for years to come as coastal communities struggle to rebuild their infrastructure, and people displaced by the storm struggle to rebuild their lives.
Winter storms can also produce rough seas, coastal flooding, and beach erosion. Nor'easters along the east coast, which are most frequent and strongest between September and April, typically account for more cumulative damage than hurricanes because they occur more frequently and may last for several days. Strong winter storms are also responsible for significant land losses in the Gulf and around the Great Lakes. Along the Pacific coast, most beach erosion and land loss can be attributed to winter storms and unusual oceanographic conditions such as El Niño, which occurs every four to five years and has a significant effect on weather patterns, sea levels, and ocean currents.
Flooding
Flooding causes more damage in the United States than any other severe weather related event. Flooding can occur in any of the U.S. states or territories at any time of the year.
Coastal Erosion
Coastal erosion is a process whereby large storms, flooding, strong wave action, sea level rise, and human activities, such as inappropriate land use, alterations, and shore protection structures, wear away the beaches and bluffs along the U.S. ocean and Great Lakes coasts. Erosion undermines and often destroys homes, businesses, and public infrastructure and can have long-term economic and social consequences.
In the United States, coastal erosion is responsible for approximately $500 million per year in coastal property loss, including damage to structures and loss of land. To mitigate coastal erosion, the federal government spends an average of $150 million every year on beach nourishment and other shoreline erosion control measures. Despite these efforts, a 2000 Heinz Center study found that erosion may claim one out of four houses within 500 feet of the U.S. shoreline by mid-century.
While coastal erosion affects all regions of the United States, erosion rates and potential impacts are highly localized. Average coastline recession rates of 25 feet per year are not uncommon on some barrier islands in the Southeast, and rates of 50 feet per year have occurred along the Great Lakes. Severe storms can remove even wider beaches, along with substantial dunes, in a single event. In undeveloped areas, these high recession rates are not likely to cause significant concern, but in some heavily populated locations, one or two feet of erosion may be considered catastrophic.
A tsunami following the 1964 Good Friday earthquake caused damage in Kodiak, Alaska.
Tsunamis
Tsunamis are a threat to life and property to anyone and anything living near the ocean. The coasts and inland waters of California, Oregon, Washington, Alaska, Hawaii, the Pacific territories, Puerto Rico, and the Virgin Islands are most at risk among U.S. coastal states, but the Atlantic and Gulf Coasts are not immune.
A series of ocean waves generated by a rapid large-scale disturbance of the sea water, tsunamis do not have a season and do not occur regularly or frequently. Most tsunamis are generated by earthquakes, but may also be caused by volcanic eruptions, landslides, undersea slumps, or meteor impacts. Tsunami waves radiate outward in all directions from the disturbance and can move across entire ocean basins. A tsunami typically causes the most severe damage and casualties close to its source, where local populations may have little time to react before the waves arrive.
The 2004 Indian Ocean earthquake increased awareness of the catastrophic nature of tsunamis. The earthquake triggered a series of tsunamis on December 26 that killed approximately 230,000 people, displaced more than one million people, and caused billions of dollars of property damage.
Land Subsidence
Land subsidence is a gradual settling or sudden sinking of the Earth's surface. This loss in elevation can cause damage but, importantly, it increases the dangers posed by flooding and sea level rise. Subsidence occurs naturally and as a result of human activities. Principal causes include groundwater removal, drainage of organic soils, underground mining, natural compaction, and thawing permafrost.
Texas and Florida are experiencing subsidence related to the removal of groundwater, and subsidence due to oil and gas removal has cost millions in damage and remedial costs in California. Loading of the modern Mississippi River delta, sediment compaction, faulting, and human activities are the main cause of subsidence in the Gulf states. The accumulation and compaction of several hundred feet of sediments since the last ice age has pushed the southern edge of Northern America downward.
For additional information contact Christa Rabenold.