Flooding has cost individuals, communities, counties, and the state and federal governments in the billions of dollars. Damage caused by flooding and coastal flooding from January 1, 1950 to April 30, 2017, per the NOAA Storm Events Database, by county, was:
- Lancaster County: A total of $1.87 million in property damage from five of 12 flooding events including a Nor'easter in November 2009, Tropical Cyclone Sandy in 2012, and Hurricane Joaquin in 2015.
- Northumberland County: A total of $20.43 million in property damage from four of 12 flooding events including Tropical Storm Ernesto in 2006, Tropical Cyclone Sandy in 2012, and a Nor'easter in November 2009.
- Richmond County: A total of $1.8 million in property damage from two of seven flooding events including Tropical Storm Ernesto in 2006 and Tropical Cyclone Sandy in 2012.
- Westmoreland County: A total of $220,000 in property damage from two of seven flooding events including Tropical Storm Ernesto in 2006 and Tropical Cyclone Sandy in 2012.
Specific risks to the Northern Neck
Not surprisingly, those areas on the Northern Neck most at risk for flooding are low-lying. And development in those areas will most surely be flooded.Floods may not impact most of Richmond County, but "(u)nfortunately, the most vulnerable areas also represent some of the more desirable development sites, along the shoreline of the major creeks that flow into the Rappahannock River." (Richmond County Virginia, Comprehensive Plan Adopted July 11, 2013 (PDF))
Northumberland County faces a similar challenge. According to the 2006 Comprehensive Plan Northumberland County, Virginia (PDF),
FEMA's Flood Insurance Study determined that all development in the County's floodplains is subject to water damage. Some flood-prone areas are subject to high velocity wave action which may cause structural damage and severe erosion along the shoreline. Due to the exposure afforded by the expanses of open water (fetch) on the Chesapeake Bay and the Potomac River, the northern and eastern sections of the County are most vulnerable to wave damage.
There is considerable development in Northumberland County that is located within the 100-year floodplain shown on the Floodplain Map. It includes full-time dwellings, seasonal cottages, businesses and industries. This is understandable, given that most of the existing development within the County occurred before the flood zone maps were first prepared pursuant to a 1968 federal law. Even today an owner still has the option of building within a floodplain; however, most dwellings that are financed with insured loans are required by the mortgage insuring agency to purchase flood insurance, and/or raise the lowest habitable floor above the 100-year flood elevation.
Pressure for future development in the County's floodplains is expected to continue as long as an abundant supply of lots along the shorelines is available. That, however, is rapidly changing. The low mortgage interest rates in 2003 spurred a boom in waterfront development in the County. The amount of shoreline is dwindling, (examine Figure 1:1 2004 Existing Development), as the price of available land increases.
Lancaster County's proximity to the Chesapeake Bay and Rappahannock River among many other bodies of water make it a target for flooding, especially during storms which drive storm surge. Lancaster County "has approximately 12,448 acres (14.4%), or 19.45 square miles, of land that lies within the 100- year flood plain." (Lancaster County Virginia Comprehensive Plan October 31, 2013, Chapter 2: Suitability of Land for Development (PDF)) The video Northern Neck flooding has worsened with each tide cycle, official says explains more:
Westmoreland County is couched between the Rappahannock and Potomac rivers and has a total of 252 miles of shoreline. The areas which regularly flood along the Rappahannock River do little damage to people and property because "population density in this area is low. One of the main reasons for the low density is that there is poor road access to the shore." (Westmoreland County Comprehensive Plan (2010) (PDF)). The plan's narrative continues,
Along the Potomac River, approximately 77% of the shoreline is considered low shore, and several sections are susceptible to flooding. Of approximately 3,300 parcels along the shoreline, 66.9% are residential, 3.6% are farms with a house, and 2.9% are commercial.
The majority of the residential development along the waterfront consists of strips of houses along the shore, with many being vacation or second homes.
Flood risk assessment
Several state and federal government agencies map areas at risk of flooding. The risk could be 100 years or 500 years or from a storm surge resulting from a storm. Each agency has their own reason for conducting the mapping. FEMA, for example, maps flood zones for the National Flood Insurance Program. This program has three purposes: insuring individuals against losses from floods, engaging communities in loss mitigation, and reducing federal emergency disaster aid.
Post-storm field visits and laboratory tests have confirmed that wave heights as small as 1.5 feet can cause significant damage to structures when constructed without consideration to the coastal hazards. Additional flood hazards associated with coastal waves include floating debris, high velocity flow, erosion, and scour which can cause damage to Zone AE type construction in these coastal areas.
Other FIS reports, maps, and other materials are available at the FEMA Flood Map Service Center.
FEMA also manages the Risk MAP (Risk Mapping, Assessment and Planning) program, a comprehensive way to identify flood risks and plan with them in mind.
The US Geological Survey (USGS), another federal government agency, maintains data sets about floods. The Flood Event Viewer tracks storm surge and high-water mark data among others and can be used for real-time event tracking and after events to assess water height.
On the state level, the Virginia Department of Emergency Management (VDEM) produces storm surge maps. The purpose of the PDF maps of particular areas and the interactive Virginia Hurricane Storm Surge Tool is to identify the risk of storm surge at a specific address or a broader area (town, or neighborhood, for example). As is the case with other maps, risk is color coded. Noteworthy:
- "Storm surge is cumulative so if an area is at risk for category 1 storm surge, it will also be at risk for storms of a higher category."
- "The storm surge zones of this map indicate the maximum area that may be inundated by a hurricane of a given value."
In June, VDEM launched #KnowYourZoneVA, an improved evacuation plan for coastal Virginia during hurricanes and other emergencies or disasters. If you have to remember any color coding, remember the #KnowYourZoneVA colors (see Virginia's got a new hurricane/other disaster evacuation plan). The surge map colors are not the same as the evacuation plan colors and the latter are part of an actionable plan to keep Virginians safe.
This is the fifth in a series of posts about threats and risks, especially during hurricane season.
- Part 1, New series: Hurricanes, evacuation, data, and the Northern Neck
- Part 2, Virginia's got a new hurricane/other disaster evacuation plan
- Part 3, Hurricanes, tornadoes, and other extreme weather on the Northern Neck
- Part 4, #KnowYourZoneVA on the Northern Neck
