Hurricane Isabel, 2003 (Source: NOAA)
Hurricane disaster planning in Hampton Roads is focused on evacuating people if a Class 3 storm hits. In 2014, the emergency management professionals felt confident enough about predicting the path of strong storms to revise the evacuation plans. Old plans were based on closing gates along I-64, reversing the eastbound lanes so everyone in the region could flee inland to Richmond.
New plans involve defining specific evacuation zones for evacuation alerts, so fewer people will be asked to leave and congestion will be more manageable. The first areas to be evacuated will be low-lying areas subject to flooding by storm surges, and the governor will initiate the process for issuing warning to evacuate starting 72 hours (rather than 48 hours) before a storm's predicted arrival in Hampton Roads.1
Florida/Louisiana get Class 5 hurricanes, and South Carolina gets Class 4 hurricanes (including Hugo, which devastated the state in 1989). Virginia is north of 36° 30' latitude, storms moving north encounter cooler water, and wind intensity drops as the temperature of the ocean drops. Virginia rarely sees hurricanes stronger than Class 2, though Class 3 storms are a realistic threat. As the ocean warms over the next century, Class 3 hurricanes could become more common.
The wind from hurricanes offers some danger in Virginia, but on the coastline flooding from the storm surge is the greatest danger. In 1667 the water level in the Chesapeake Bay rose 12 feet, and in 1749 it rose 15 feet.2
There were "Great September Gusts" in 1667, 1769, 1775 (The "Independence Hurricane"), and 1821. The storm that passed over Mount Vernon on July 23, 1788 is called "George Washington’s Hurricane."
After the soil is saturated from heavy rain, strong winds can blow down large trees - but the greatest threat from hurricanes as they move inland. Hurricanes that strike the Blue Ridge can create major landslides.
Topographic change is a process of "punctuated evolution," and in just a minutes storms can transform the landscape more significantly than centuries of slow erosion. Much of the carving of stream valleys, and much of the lowering of Virginia's mountains, occurs in short bursts from major storms.
storms such as Hurricane Isabel in 2003 can storm surges on the Atlantic Ocean/Chesapeake Bay coast, and also generate enough concentrated rainfall to create floods in the valleys of the Blue Ridge
Source: National Aeronautics and Space Administration (NASA), Earth Observatory, Hurricane Isabel
In 1967, Hurricane Camille entered the United States along the Gulf Coast, then moved inland until it paused at Nelson County. At least 27 inches of rain fell in six hours at Massies Mill, though the National Weather Service collected unverified information that 31 inches fell at some locations.
Soil on mountainsides became saturated, and the extra weight of the water made the soil too heavy to remain on some steep slopes in the Blue Ridge. Patches of soil detached from the underlying bedrock and slid downhill, peeling away and exposing the hard igneous core of the mountain. Landslides and debris flows from Hurricane Camille left scars for decades. Inland, away from the Virginia coast, that storm caused 113 deaths from the landslides and floods.3
Hurricane Agnes created massive flooding in 1972. Floodwaters flowing ver the top of the two dams on the Occoquan River destroyed the Route 123 bridge at the Town of Occoquan, and one of the Route 1 bridges downstream.
the Route 123 bridge destroyed in Hurricane Agnes, 1972
Source: Library of Virginia, Raging Occoquan River
the Route 1 bridge destroyed in Hurricane Agnes, 1972
Source: Library of Virginia, Repairs begin at Occoquan Bridge
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 to Virginia's coastline, the damage will be measured in billions of dollars. 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. A Class 3 hurricane will hit the Chesapeake Bay someday, and coastal cities are preparing for the inevitable.
the storm surge from Hurricane Isable was as high as six feet near West Point, on the York River
Source: National Oceanic and Atmospheric Administration (NOAA), Historical SLOSH Simulations - Isabel
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.
One major challenge for emergency management officials is to determine when to order a mass evacuation. The patch of a storm changes, and the disruption of an evacuation would be dramatic, so there is a natural desire to wait until weather forecasters are confident about a storm track. On the other hand, the evcuation plan assumes 36 hours will be required for everyone to get to higher ground. Critics have noted:4
Hampton Roads evacuation routes assume the Chesapeake Bay Bridge-Tunnel will be closed and no one should flee to the Eastern Shore
Source: Virginia Department of Emergency Management, Virginia Hurricane Storm Surge Tool
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 storm surges. The first step was to create computer models to assess potential designs and environmental impacts. The academic exercise requires making no decisions; the tough choices regarding costs vs. benefits (and how to ensure US Navy warships would never be trapped inside Hampton Roads) will come later.5
sea level rise predictions
Source: US Fish and Wildlife Service, Vanishing Lands - Sea Level, Society, and Chesapeake Bay (Figure 10)
Superstorm Sandy in October, 2012 bypassed most of Virginia before slamming into New Jersey and New York City, but a future storm like it could redistribute the sands on Willoughby Spit and destroy all the development there, including the southern end of the Hampton Roads Bridge-Tunnel
Willoughby Spit was formed by hurricanes in the 1700's
Source: US Army Corps of Engineers, Norfolk District Image Gallery
in 1969, Hurricane Camille dropped at least 27" of rain overnight in Nelson County Source: National Oceanic and Atmospheric Administration (NOAA), Hurricane Camille - August 16-21, 1969
the most-direct route from England to Virginia required tacking against westerly winds, so ships often sailed south to the Azores and then west across the Atlantic Ocean following the same track as hurricanes
Source: Atlas of the Historical Geography of the United States, Winds and Sailing Routes: Summer (Plate 1e, digitized by University of Richmond)
how wind and air pressure fluctuate as a hurricane passes over -
Hurricane Ivan off the coast of Alabama, September 2004
(Source: NOAA National Buoy Data Center)