Category 3 storm surge in Hampton Roads
Source: Hampton Roads Emergency Management Committee
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, Gloucester...
The Hurrican Flooding and Tidal Surge maps from the Hampton Roads Emergency Management Committee1 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.
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 In a worst-case scenario, I-64 in the Willoughby Spit area would be underwater once a storm arrived. For evacuation to succeed, people will need to be convinced to leave Norfolk/Virginia Beach long before any major storm arrives.
hurricane gates on Interstate 64
Source: Virginia Department of Transportation
The emergency management professionals do not consider seriously the impact of Category 5 storms hitting Norfolk/Virginia Beach. Hurricanes are fueled by warm water, so a Category 5 storm could impact Florida or the Gulf Coast. However, hurricanes lose energy as they move north and encounter colder water. Even with the Gulf Stream, the waters off Virginia Beach are too cold for a Category 5 storm to reach Virginia. Some Category 5 storms hit the Gulf Coast and then move north 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, though the storms can still drop massive amounts of rain.)
The National Flood Insurance Program, managed by the Federal Emergency Management Administration (FEMA), provides coverage for damage caused by floods. Private insurance companies determine what level of other risks to accept over the long term. The low-probability risks, such as hurricanes, are not zero-probability risks.
Also, the 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. 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.
There are three significant threats to Hampton Roads that the insurance companies and banks (as well as government agencies) have to consider:
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.
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.3
But inevitably, one is headed into the Chesapeake Bay. The state has designated hurricane evacuation routes for getting people out of the Hampton Roads area. It requires reversing eastbound I-64 so there are 4 escape lanes headed west to the high ground at Williamsburg.
 Category 1 |
 Category 2 |
 Category 3 |
 Category 4 |
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) | |||
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.4. The worst case scenario: if the West Antarctic Ice Sheet melts, sea level could rise over 20 feet.5
The City of Poquoson 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) and in 2008 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:6
In addition, the land in the lower Chesapeake Bay is subsiding, perhaps in part from 1) pumping out groundwater, 2) slow isostatic response ("rebound") of the land after the weight of the ice sheets disappeared in the last 20,000 years, 3) tectonic pressures within the North American Plate that could be bending the continent and downwarping the Chesapeake Bay area, and 4) continued compaction of sediments that were disrupted 35 million years ago when a "bolide" (comet/meteor) impacted near what is today Cape Charles. If the land subsidence trends continue, Hampton Roads will experience 0.4-3.3 feet of land subsidence over the next century.7
As described in the "The State of the Region: Hampton Roads 2009" report:8
Unless the trends change, Norfolk will be abandoned (or sea walls will surround it) in several hundred years. At the 600th anniversary of Jamestown, the historic old capital of Virginia could be a barrier island, and the ruins of Norfolk could lie underneath sediments accumulating on the continental shelf.
|
Tsunami: A tsunami is a "big wave." A very, very big wave... and Hampton Roads could be devastated by one.
The Cumbre Vieja volcano in the Canary Islands, off the coast of northwestern Africa, could collapse and create a tsunami that drowns Norfolk and other points on the eastern coastline of North America. The claim that a giant wave could threaten the United States due to a landslide on the other side of the Atlantic Ocean sounds surprising to many, but the 1964 Alaskan earthquake created a killer tsunami 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. Oddly enough, there is a second geologic risk that could generate a massive wave that might destroy Norfolk. 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 strong hurricane or small landslide, a burst of methane could be released. The giant gas bubble would create a massive underwater landslide and displace enough Atlantic Ocean water to generate a tsunami that would wash over the Eastern Shore, Norfolk, and other coastal areas. |
Would such a wave reach the base of the Blue Ridge, as shown in the 1998 movie Deep Impact? Perhaps not... but 35 million years ago a comet or meteor landing in the Atlantic Ocean off the coastline of Virginia may have created such a wave.
In 2006, Norfolk became the first East Coast city to earn recognition by the National Oceanic and Atmospheric Administration (NOAA) as "TsunamiReady/Storm Ready." According to the local paper, the city official responsible for disaster preparedness:9
Links
|
|
