flooding during Hurricane Isabel in 2003
Source: National Weather Service, Hurricane Isabel Photo Gallery
Norfolk is only a few feet above sea level. The same is true about the rest of the urbanized Hampton Roads area, including Virginia Beach, Portsmouth, Chesapeake, Suffolk, Hampton, Poquoson, Newport News, and Gloucester.
If current trends continue, the question is not "will Norfolk (and the rest of Hampton Roads) drown?" but "when will Norfolk, Tangier Island, Chincoteague, and other locations near sea level drown - and what should be the response to this threat in coastal areas?"
It is unrealistic to expect owners of private property along the shoreline to passively accept that valuable land, houses, and businesses will wash away in the next century and that no action should be taken to protect current infrastructure. When we buy bananas at the store, we don't expect them to last forever - but the American image of land is that it should last forever, and government agencies should respond when natural processes threaten the value of real estate.
However, taxpayers living away from the coastal zone may object to subsidizing insurance and disaster relief costs for coastal communities, especially expensive waterfront homes built in areas of known risk. If Federal and state funding will be provided, should it finance seawalls, groins, and other shoreline hardening techniques to mitigate impacts in the next 25-50 years, or should government investments focus now on moving existing structures away from the high-risk areas over the next 100 years?
egret trying to feed from bulkhead (hardened shoreline)
Source: US Fish and Wildlife Service, Back Bay National Wildlife Refuge Comprehensive Conservation Plan
Should local cities/counties that issue building permits require that all new structures near the shoreline must be built even higher that the current National Flood Insurance Program maps mandate, just in case predictions of a speedup in sea level rise (compared to historical rates) comes true? How should government agencies deal with old infrastructure, such as sewers, that are at risk from flooding as sea levels continue to rise?
Undeveloped places, such as the Chincoteague National Wildlife Refuge and False Cape State Park, will also be affected. Should places with just plants and animals be sacrificed as the waters rise, so funding can be directed towards urbanized site and shoreline houses? Or should we consciously decide to retreat from the shore,line, removing buildings and converting now-developed parcels into parkland as part of a "managed retreat" strategy over the next 50 years?
Phase 1 and Phase 2 evacuation routes for people in vehicles to flee Hampton Roads
Source: Virginia Hurricane Guide
The Hurricane Flooding and Tidal Surge maps from the Hampton Roads Emergency Management Committee show that a storm surge from a Category 3 hurricane would affect much of the Hampton Roads area. Flood waters could inundate large portions of the developed shoreline, if the moon and tides push tides to their maximum height when a storm arrives.1
Half the residents in Hampton Roads, especially those in Virginia Beach/Norfolk, are supposed to evacuate on I-64 through the Hampton Roads Bridge-Tunnel. Special gates have been installed on access ramps so every lane of the interstate could be used to move people east past Williamsburg. However, the Virginia Department of Transportation (VDOT) will close bridges and tunnels connecting South Hampton Roads to the Peninsula once sustained winds reach 45mph.2
hurricane gates on Interstate 64
Source: Virginia Department of Transportation
The storm surge from a Category 1 hurricane is projected to cover I-64 on Willoughby Spit, blocking evacuation by car through the Hampton Roads Bridge-Tunnel. Hampton Roads residents will need to be convinced to leave Norfolk/Virginia Beach long before any major storm arrives, if the plans for moving people out of the danger zone are going to succeed.
I-64 lane reversal between Norfolk and I-295 beltway, west of Williamsburg
Source: Virginia Department of Emergency Management Virginia Hurricane Evacuation Guide
Hurricanes are fueled by warm water, so a Category 5 storm could impact Florida or the Gulf Coast. Emergency management professionals do not consider seriously the impact of Category 5 storms hitting Norfolk/Virginia Beach; the Commonwealth of Virginia Storm Surge Inundation Maps only consider Category 1-4 hurricanes.
Category 5 hurricanes at Chesapeake Bay are unexpected because of the latitude and the pattern of ocean currents. Hurricanes lose energy as they move north and encounter colder water. Even with the Gulf Stream, the ocean at 36 degrees 30 minutes of latitude (the Virginia-North Carolina border) is too cold for a hurricane to reach Virginia with enough energy to qualify as Category 5. However, climate change could lead to warmer water moving north, which could lead to more-intense hurricanes striking Virginia.
Some Category 5 storms hit the Gulf Coast and then move inland to Virginia, such as Hurricane Camille in 1969. The winds drop to tropical storm status as the weather system travels over land from the Gulf of Mexico to Virginia, but the storms can still drop massive amounts of rain and cause death and destruction in the Blue Ridge.
areas in Norfolk/Portsmouth expect to be flooded by storm surge from Category 1-Category 4 hurricanes
Source: Virginia Department of Emergency Management, Commonwealth of Virginia Storm Surge Inundation Maps
When a hurricane arrives, local officials can issue mandatory evacuation orders. For example, the City of Virginia Beach declared a Local Emergency when Hurricane Irene came ashore at Cape Hatteras, N.C. in August 2011. That storm was Category 1, after weakening just before landfall, but still caused nearly $60 million in damage in Virginia. The Federal government declared that 48 Virginia jurisdictions qualified for Public Assistance, which authorizes Federal funding for emergency response and repair/replacement/restoration of publicly-owned facilities and the facilities of certain non-profits.3
jurisdictions authorized for "Public Assistance" after Hurricane Irene by Federal disaster declaration FEMA-DR-4024, Virginia
(including Alexandria, excluding Gloucester and Richmond counties)
Source: Federal Emergency Management Administration, Virginia Hurricane Irene
The National Flood Insurance Program, managed by the Federal Emergency Management Administration (FEMA), provides coverage for damage to individual properties caused by floods. Private insurers will issue policies that deal with the risks from fire, wind, or visitors tripping on the front steps, but the premiums and deductibles reflect the different risks in different locations. House insurance premiums for Hampton Roads homeowners are roughly twice as high, compared to premiums for houses located in Alexandria and Roanoke.4
In addition to purchasing homeowners insurance, financial institutions that issue mortgages require a high percentage of Hampton Roads homeowners to purchase separate flood insurance policies. Standard homeowners insurance policies cover damage caused by a water pipe break within the house, but do not pay for damage caused by external floods. Flood Insurance Rate Maps produced by FEMA define a Special Flood Hazard Area, the area that has a 1% or greater annual chance of flooding (i.e., 100-year flood plain).
The cost of a National Flood Insurance Program policy for an individual property is tied to the risk of flooding at that specific location, and the elevation of the structure. Houses receive an Elevation Certificate, determining its height above/below the Base Flood Elevation with a 1% or greater annual chance of flooding. For years, flood insurance rates were subsidized for 20% of the policies and did not reflect actual risk, or future risk from sea level rise. A 1991 FEMA report on the predicted impacts of sea level rise noted that nearly 20% more land would be at risk by a 1-foot rise in sea level, and nearly 40% more by a 3-foot rise:5
FEMA's interpretation of flood risk to downtown Norfolk and Ghent neighborhood
Source: City of Norfolk Map Gallery, Flood Insurance Rate Map
Insurance rates were too low to pay for claims (especially after the hurricanes in 2005, including Katrina), and Congress had to appropriate supplemental funding to bail out the insurance program. Subsidized insurance reduced the motivation of property owners to move out of high-risk floodzones. In addition, disaster recovery after tropical storms, hurricanes, and other events (such as Superstorm Sandy in 2012) is also funded largely by the Federal government. Low-cost Federal flood insurance and the expectation of "free" Federal funding after a disaster reduced the pressure on homeowners to minimize risk. State/local government officials could encourage development in high-risk areas, since much of future disaster recovery costs would be funded by the Federal government.
In 2012, the Biggert Waters Flood Insurance Reform Act finally modified flood insurance rates to reflect full risk, phasing out most subsidies. FEMA ended the old pattern of maintaining low, "grandfathered" rates when Flood Insurance Rate Maps were updated to reflect higher risks. Starting in 2012, FEMA began to apply new rates that reflected actual risk after adoption of a new Flood Insurance Rate Map, with the higher rates gradually phased in.6
Cities in Hampton Roads could start now and replan/rezone areas at risk, to replace existing structures that might flood with open space (such as ballfields and waterfront parks) over the next 50 years. Reducing density of development in high-risk areas would be expensive, and alter tax revenues. Such a strategy requires either a long-term perspective, or a stimulus of some sort to alter current patterns of development.
repetitive loss areas in City of Hampton, where two or more claim payments of more than $1,000 have been paid within a 10-year period since 1978
Source: Peninsula Multi-Jurisdictional Natural Hazards Mitigation Plan - City of Hampton, Virginia, Repetitive Flood Loss Analysis (Appendix L)
In 2012, an international insurance executive spoke at a forum on how climate change affects flooding risk, as part of the Old Dominion University Climate Change and Sea Level Rise Initiative. After a tour of Norfolk, she questioned why local governments are increasing risk by ignoring predictions of higher floodzones, approving new development in areas that will be affected if sea level rises:7
low-lying areas adjacent to Lafayette River, and expected to flood from storm surge of a Category 1 hurricane
Source: City of Norfolk, Category 1 Hurricane Storm Surge map
State Corporation Commission, which regulates insurance in Virginia, must ensure insurance companies will be able to pay off all claims if a catastrophe does occur. Insurance companies focus on selected areas, establishing a network of agents and concentrating advertising in particular markets. However, if a "singularity" (such as a hurricane) occurs, then a company could be overwhelmed by the number of claims. In 2007, Allstate announced it would maintain policies of existing customers in 19 Virginia counties, but would write no new policies in order to minimize the risk associated with hurricane damage. (By 2013, Allstate had reentered the market, but with greater selectivity in choosing what sites to insure.)8
It is in the interest of the State of Virginia to have insurance companies hedge their bets, and have only so many policies in one geographic area. To avoid the risk that an insurance company will go bankrupt rather than pay all potential claims, insurers who write many policies in one area will obtain re-insurance, basically buying coverage from other companies. That technique reduces profits, but spreads the risk. While hurricanes may be a low-probability of risk in Hampton Roads, they are not a zero-probability risks.
area predicted to be flooded in Portsmouth, by storm surge from Category 1-4 hurricanes
Source: City of Portsmouth Land Information System (click on images for larger versions)
There are three significant threats to Hampton Roads that the insurance companies and banks (as well as government agencies) have to consider: hurricanes, sea level rise, and tsunamis.
Hurricane: Massive rainfall from a storm can overwhelm the stormwater management systems in urbanized areas, as Hurricane Floyd demonstrated in 1999 when it swamped the city of Franklin and tropical storm Gaston did to Richmond's Shockoe Valley in 2004. In 2003, winds from Hurricane Isabel wrecked utility systems throughout the Coastal Plain of Virginia, leaving some people without electricity for two weeks. In 2011, Hurricane Irene blasted Hampton Roads, Richmond, and Northern Virginia east of I-95.
storm surge can be as much as 15 feet higher than high tide
Source: Virginia Department of Emergency Management, Virginia Hurricane Evacuation Guide
If a hurricane brings a storm surge of 6-8 feet into the region, much of Virginia Beach and Norfolk will be underwater due to the storm surge, the rise in sea level associated with the lower barometric pressure in the eye of the hurricane. Tidewater officials track hurricanes as closely as the officials in Florida or North Carolina, where most hurricanes come ashore on the East Coast, but no hurricane came ashore directly in Virginia in the 1900's.9
But inevitably, one is headed into the Chesapeake Bay. To prepare for evacuation, the state has designated hurricane evacuation routes for getting people out of the Hampton Roads area. The evacuation plan requires reversing eastbound I-64 to double the number of escape lanes headed west; there are gates on all interchanges between the high ground east of Williamsburg (I-295) and Hampton.
The Virginia Institute of Marine Science (VIMS) has even considered building a 24-mile long barrier at the mouth of the Chesapeake Bay, parallel to the bridge-tunnel, to block hurricane-caused storm surges. First step is to create computer models to assess potential designs and environmental impacts. The academic exercise requires making no decisions; the tough cjoices regarding costs vs. benefits (and how to ensure US Navy warships would never be trapped inside Hampton Roads) come later.10
sea level rise predictions
Source: US Fish and Wildlife Service, Vanishing Lands - Sea Level, Society, and Chesapeake Bay (Figure 10)
Sea Level Rise: At various times, the Atlantic Ocean has been higher and Norfolk has been underwater - that's why there are whale fossils from the Miocene Period found in sand/gravel deposits on the Coastal Plain. Since the end of the last ice age, the shoreline of Virginia has moved westward as the Atlantic Ocean has expanded and covered the continental shelf. The Native Americans who first settled Virginia camped on a different Atlantic Ocean coastline during their hunting and gathering expeditions. Their first campsites are probably 30-50 miles offshore now, under 100 feet of saltwater and recent sediments.
Continued global warming could melt remaining ice on Antarctica and Greenland, adding more water to the oceans. A warmer atmosphere will warm up the water in the oceans, causing them to expand. The Intergovernmental Panel on Climate Change (IPCC) projects an absolute sea level rise of 1-3 feet in the next 100 years.11
There may be a "hotspot" for unusually rapid sea level rise in Virginia and further north if warmer, fresher ocean water alters the Gulf Stream and the North Atlantic Current, which currently depress sea level along the shoreline north of Cape Hatteras.12
The worst case scenario: if the West Antarctic Ice Sheet melts, sea level could rise 10-20 feet.13
The Town of Tangier, on a small island in the Chesapeake Bay, may be the first incorporated Virginia jurisdiction to disappear because of sea level rise. Several barrier island communities have been abandoned in the past, including Wash Woods in what is today's False Cape State Park. Residents of Hog Island, on the Atlantic Ocean side of the Eastern Shore, moved to Willis Wharf in Northampton County after a hurricane in 1933 flooded the island. Today, the island is a nature preserve, part of the Virginia Coast Reserve owned by The Nature Conservancy.14
Ever since the first Paleo-Indians arrived in Virginia, rising sea levels have been forcing humans to move their communities back from the edge of the Atlantic Ocean. However, the shifting shorelines that spurred abandonment of Hog Island may be triggered by normal barrier island sand migration, rather than increasing sea levels. An archeologist working on the Eastern Shore has commented:15
changing shorelines of Hog Island
Source: US Geological Survey Circular 1075, Coasts in Crisis
The City of Poquoson is another Virginia jurisdiction that might have to be abandoned, if sea level does rise three feet in the next 100 years. Poquoson's Multi-Hazard Mitigation Plan, when updated in 2009, acknowledged the risk.
According to the plan, "the majority of the City is less than seven feet NGVD" (National Geodetic Vertical Datum). In 2008, Poquoson made the risk of sea level rise a "critical hazard requiring mitigation." The slow, incremental rise is not the concern - the fear is that, because of the gradual sea level rise, a future storm will create a surge of high water that could cause great damage in just one day:16
storm surge, greatest cause of flooding during 1962 storm, could be one foot higher in 2030
Source: City of Poquoson Multi-Hazard Mitigation Plan
In addition to sea level rising, the land in the lower Chesapeake Bay is subsiding. The drop in the level of the land is caused by one or more of the following reasons:
If the land subsidence trends continue, Hampton Roads will experience 0.4-3.3 feet of land subsidence over the next century.17
As described in "The State of the Region: Hampton Roads 2009" report:18
if sea level/land subsidence changes 3.7 feet, all the area in green will be flooded... and other land will be at risk from storm surges
Source: Greenhouse Effect and Sea Level Rise: America Starts to Prepare: Sea Level Rise Maps for Virginia
How will the tourism and real estate industries in coastal areas of Virginia be affected? One option is to harden the shoreline with seawalls or levees, building a protective ring around developed areas in the same way New Orleans is protected. That is the response being taken by the US Government at Wallops Island, to protect National Aeronautics and Space Administration’s facilities. In 2012 the Federal government built a 14-foot high seawall, and widened the beach 82 feet to reduce the energy of ocean waves before they strike the hard barrier.19
After Hurrican Sandy in 2012, the US Army Corps of Engineers revised the rules prohibiting sand replenishment projects on beaches with hard barriers and approved a project to widen the beach at Ocean View. Sand dredged from the Thimble Shoal shipping channel will widen the beach by 60 feet for a seven-mile stretch, even though Norfolk had previously built 36 rock breakwaters. The sand will wash away, so the Corps committed to replenish that stretch of beach every nine years until 2056.20
Ocean View beach, west of Little Creek inlet, before 2015-16 replenishment
Source: ESRI, ArcGIS Online
A sea wall to protect key portions of Norfolk would cost about $1 billion. A sea wall for Virginia Beach would be less suitable, since the city's tourist business is based on access to a sandy beach. A levee or barrier on the current dune line might limit future storm damage to structures along Atlantic Avenue, but hardening the shoreline would block the beach from migrating naturally and eventually eliminate the wide beach as sea levels rise.
As an economist and former president of Old Dominion University described it:21
sea level rise at Sewells Point based on data between 1927 to 2006: a trend of 4.44 millimeters/year, equivalent to 1.46 feet in 100 years
Source: National Oceanic and Atmospheric Administration (NOAA) "Sea Levels Online," Mean Sea Level Trend, station 8638610 at Sewells Point, Virginia
Beach replenishment is only a short-term solution for Virginia Beach. Within 100 years, assuming sea level keeps rising as predicted, the current location of the sandy beach will be completely underwater and the shoreline will have moved west. The City of Virginia Beach has the option of "strategic retreat," sacrificing the developed areas along the shoreline and removing the hotels along Atlantic Avenue to allow the beach to migrate naturally. As sea levels keep rising, the city could remove the next block of developed property along Pacific Avenue and the new shoreline.
Strategic retreat avoids the cost of building and maintaining structures. On the undeveloped Atlantic Coast shoreline of Virginia's Eastern Shore, allowing the water to rise would have minimal impact on property values. However, Tangier Island in the middle of the Chesapeake Bay is at high risk:22
Within Virginia, the jurisdictions with the greatest number of acres at risk from sea level rise are Accomack County, City of Virginia Beach, and Northampton County - not surprising, considering their location and size. Other jurisdictions in Hampton Roads, and counties on the Peninsula/Middle Peninsula/Northern Neck, may be equally exposed to flooding, but are smaller in area.
Within Virginia, there are 140 square miles of dry land within 1 meter of sea level, over half of which has already been developed. In Portsmouth, 80-90% of the city would be underwater if a Category 3 hurricane struck. There are also 55 square miles of non-tidal wetlands and 625 square miles of tidal wetlands, which provide environmental values but are not likely to be protected from sea level rise.23
Asking landowners to adopt the strategic retreat approach to rising sea levels is politically risky. No one wants to abandon developed areas, whether the investment in housing/infrastructure is located on rural Tangier Island or in urbanized Hampton Roads.
Politicians win elections by promising to solve problems. Few candidates will generate substantial campaign funds by telling business leaders to abandon their resort infrastructure at Virginia Beach, and allow other landowners further inland to become high-value waterfront property - at least briefly.
Bureaucratic inertia is also a challenge. Even in 2014, the US Navy had not identified a specific estimate of sea level rise for use in planning how to protect its assets at Hampton Roads, and the Corps of Engineers had not identified the cost-effectiveness of potential projects for making decisions on future budget priorities. The mayor of Norfolk reportedly told a climate scientist at Old Dominion University:24
"Doing nothing" is easy. When The Tide light-rail system was built, it was not elevated in any way to account for projected changes in sea level. "Doing something" that would a real impact on future flooding will be expensive. It would be political suicide to ask voters to raise taxes by $1 billion to fund barriers to delay the impacts of 5-7 feet in sea level rise - the cost would be now, and the benefits would be spread over the next century.
Norfolk is preparing for both adaptation and strategic retreat. The city is identifying neighborhoods along the Lafayette River that could be abandoned rather than protected by seawalls, and considering using city funds to purchase and destroy 20 homes near Norfolk State University. One church in the Ghent neighborhood was affected so often by high water that it added a link on its website to tidal flooding reports, and finally sold the building to move to higher ground.
one church in downtown Norfolk provided a tide chart as well as directions to the building, because high tides flooded the roads and blocked access
Source: Unitarian Church of Norfolk (UCN)
the Unitarian Church of Norfolk sold its building in Ghent and moved to higher ground at Military Circle, "retreating" from flooding
The Chrysler Museum spent $24 million to upgrade the facility in 2012-14, and moved all electrical and other equipment out of its basement in anticipation of future flooding. Norfolk was the third city in the world to hire a full-time "chief resilience officer," and local environmentalists have joked about the business opportunities:25
Chrysler Museum of Art in Ghent
Miami Beach is already tackling the challenge, raising stormwater fees and installing 60 underground pumps to move floodwaters out of the city into Biscayne Bay. Increasing flooding during high tides (known locally as "king tides") was a major issue in the 2013 election for mayor. The storm drains were designed to carry rainwater from the land to Biscayne Bay, but were operating as two-way channels and transporting the bay's water during king tides to flood streets and low-lying sections of Miami Beach.
Pumping floodwaters back into the bay and adding barriers/valves in stormwater channels may be just a Band-Aid solution, delaying the inevitable need to retreat from the barrier island in the next century as sea level rises. The winning candidate contended that future innovations will provide answers to the current questions, commenting:26
Proposed responses to predictions of sea level rise propose a dramatic shift in how government agencies spend tax dollars and regulate development. Owners of shoreline and low-lying private property will be affected the most. Not surprisingly, there is intense debate about not only the proposed responses, but even the need to take action now.
the coast in southeastern Virginia and North Carolina is vulnerable to flooding as sea level rises
Source: Greenhouse Effect and Sea Level Rise: America Starts to Prepare: Maps of Lands Close to Sea Level: North Carolina
North Carolina offers an alternative to strategic retreat or expensive investment. In the coastal region, landowners and local officials recommend that the state should reject predictions that sea level will rise significantly. Twenty North Carolina communities have banded together into the NC-20 coalition to oppose efforts by North Carolina officials to require preparations for a predicted 1-meter (39-inch) rise in sea level by 2021, as predicted by the North Carolina Coastal Resources Commission's Science Panel.
The counties feared state floodplain maps would be revised, requiring new roads/sewers/bridges to be constructed at higher elevations and constraining new development on low-lying land. If insurance companies and government agencies in North Carolina make decisions based on predictions of sea level rise, current coastal area property values could be reduced dramatically over a wide area.
The NC-20 coalition proposed that the Science Panel was wrong; assumptions about an increasing rate of sea level rise as glaciers melt were based on global warming scenarios that should be rejected.
Instead of assuming a 39-inch rise in sea level by 2010, the coalition claimed that the historical rate of sea level rise should be used to assume no more than an 8-inch increase in the next century. The coalition leaders concede that sea level will rise, but dispute the rate (including the concept that Cape Hatteras marks the southern boundary of a "hotspot" with accelerated sea level rise, as ocean currents shift).27
Virginia politicians must also deal with the organized groups who reject the science of predicted sea level rise. In 2012, when the General Assembly funded a study of potential impacts of coastal flooding (which will be used to request Federal funding), the legislators referred to recurrent flooding and to omitted the buzzwords of climate change and sea level rise. The Virginia Department of Environmental Quality (DEQ) refers to coastal resilience when dealing with the impacts of increasing sea levels, bypassing the political debate in order to focus on the response.28
proposed hardening of shoreline and pumps to protect against coastal flooding/tidal surge at The Hague, near Ghent neighborhood in Norfolk
Source: City of Norfolk, Coastal Flooding Mitigation (presented to Expert Advisory Panel, February 16, 2012)
In addition to Virginia Beach and the Eastern Shore, other jurisdictions inland from the Atlantic Ocean will be affected if predicted sea level rise occurs. The Chickahominy River water supply for Newport News could become more saline, increasing the cost for the utility to produce drinking water for the area. In 2011, the US Geological Survey assessed potential impacts and determined:29
If predictions of accelerating sea level rise come true, Norfolk will be abandoned or sea walls will surround it and the Coastal Plain will be flooded further inland. At the 500th anniversary of the English colonial settlement at Jamestown, the historic old capital of Virginia might be a barrier island, a mud flat, or fish habitat - and the ruins of Norfolk could lie underneath sediments accumulating on the continental shelf.
The water table in Tidewater is rising as the wedge of seawater pushes westward. A seawall at Jamestown might block a storm surge like the one from Hurricane Isabel that flooded the visitor center/museum and caused $20 million in damages, but groundwater levels will rise high enough to flood the site in 50-100 years. Archeologists traditionally leave some areas unexcavated, waiting for new scientific techniques to be developed, but are now suggesting all artifacts at Jamestown should be removed soon. One climate scientist from the Virginia Institute for Marine Science (VIMS) expects Jamestown to disappear in a century:30
Tsunami: A tsunami is a big wave, a very, very big wave. In a worst case scenario, Hampton Roads could be devastated by such a wave that might be generated in three different ways:
Landslide: There is a very slim possibility that a catastrophic collapse of the Cumbre Vieja volcano in the Canary Islands, off the coast of northwestern Africa, could create a tsunami that would affect Norfolk and other points on the eastern coastline of North America. The 1964 Alaskan earthquake created a killer tsunami far away at Crescent City, California; an underwater quake near Indonesia in December, 2004 created a tsunami that killed people all the way across the Indian Ocean in Kenya.
A Discovery Channel program claimed that a tsunami created by a landslide on the other side of the Atlantic Ocean could threaten the United States. The Tsunami Society responded with:31
The potential for an East Coast tsunami triggered by other causes is also very low. The Virginia shoreline is far from the closest zone in the Caribbean Sea where tectonic plates, sliding in a quick jerk, could generate a giant wave.
The only recorded tsunami affecting Virginia was the 1929 Grand Banks earthquake, which affected a portion of Newfoundland - but was noticed even in South Carolina. Tectonic plates in the Caribbean caused the 2010 Haiti earthquake, and will move again. However, wave energy from that region would be deflected by Florida or directed into the open Atlantic Ocean, and would have minimal impact in Virginia.32
The Cape Fear Slide, on the Outer Continental Shelf off the North Carolina coast, is one of the largest underwater landslides documented on the eastern edge of North America. It was triggered when a layer of salt rose up under pressure from overlying sediments, forming a dome with steeper and steeper slopes until the sedients broke free. A comparable slide today could generate a wave over 6 feet high on the Outer Banks of North Carolina.33
Gas Hydrates: The edge of the continental shelf could be unstable, due to subsea methane gas hydrate deposits.
The gas is frozen... for now. If there was a change in water pressure, perhaps triggered by a ocean warming followed by a strong hurricane or small landslide, a burst of methane could be released. A series of giant gas bubbles could create a massive underwater landslide, displacing enough Atlantic Ocean water to generate a tsunami that could wash over the Eastern Shore, Norfolk, and other coastal areas.
Source: National Oceanic and Atmospheric Administration (NOAA)
a 6-foot high tsunami would devastate much of Hampton Roads
Source: National Oceanic and Atmospheric Administration (NOAA), NOAA/CIRES Scientists Help Prepare Virginia Beach For Tsunami, Storm-Driven Flooding
Another Bolide: A third potential source of a tsunami is an impact by a bolide (meteor or comet) into the ocean near Virginia.
Could such a wave reach the base of the Blue Ridge, as shown in the 1998 movie Deep Impact? Yes - 35 million years ago, a bolide landing in the Atlantic Ocean off the coastline of Virginia created such a series of tsunamis that swashed back and forth, quickly filling the crater created by the impact. According to the US Geological Survey:34
In the Hollywood movie, the final scene was filmed near Gainesville on the Prince William Parkway, which was then under construction. As the water washed inland, the key characters fled up a mountainside. Judging from the species of pine trees, the up-the-mountain scene was filmed in California. Unfortunately for those on the eastern edge of Virginia, there are no mountains - other than the old landfill in Virginia Beach known as Mount Trashmore.
only in Hollywood are there mountains within 6 miles of Virginia Beach
Source: The Rellim Zone, Movie Review – Deep Impact (1998)
In fact, a tsunami did strike the East Coast on June 13, 2013, triggered perhaps by a landslide off the New Jersey coast or by air pressure changes associated with a localized "derecho" storm. Three people were swept off a jetty in New Jersey into the ocean from rocks that were 5-6 feet above sea level. Further south on the Eastern Shore of Virginia at Kiptopeke, the water gauge recorded an increase in water height 25 centimeters (10 inches) above average. That change was one of the highest recorded from the unusual event, but at Chesapeake Bay Bridge-Tunnel the increase was only 7 centimeters.36
Granby Street, flooded in 1933
Source: Norfolk Public Library Norfolk Historical Images