Flooding in the United States
Floods are the most common of natural disasters in the United States, and consequences can be severe. In the last 10 years, they have occurred in every one of the fifty states and caused nearly $24 billion in losses. Flash floods in particular are among the most frequent and deadly of weather-related hazards. Damage from flooding, however, is rarely covered in homeowner’s and business insurance policies.
Vulnerability to flooding varies with local conditions and is based on a number of factors: rainfall, river-flow and tidal-surge conditions, topography, flood-control measures, and changes due to building and excavation. Among the immediate causes are hurricanes, broken dams or levees, defective drainage systems, and sudden winter thaws, as well as heavy rain.
Flooding in the New River Valley
In a recent assessment of vulnerabilities in the New River Valley, flooding was ranked number one. In the area surrounding Virginia Tech, local floods are more likely both to happen and to have far-ranging, severe impacts than any other kind of disaster.
The mountains of western Virginia are among the most flash-flood prone areas in the U.S., due to the strong storms created by the collision of warm, moist Gulf air and cold fronts from the North. On February 22, 2003, for example, heavy rains fell upon accumulated ice and snow, setting off flash floods that impacted every jurisdiction in the New River Valley. Montgomery County and other western Virginia counties were later declared Presidential-disaster areas.
Blacksburg is also vulnerable to more predictable, riverine floods. The city is located atop the eastern continental divide where Toms and Stroubles Creeks flow into the New River. These two creeks along with Cedar Run, a tributary of the Roanoke River and Slate Branch are of the most concern for flood conditions. Flooding is most likely to occur in low-lying areas as a result of heavy rains of a localized storm, a tropical storm, or a combination of rain and snowmelt. Record setting floods occurred in 1940, 1972, 1978, 1985, and 1991. The 1991 flood caused $4.5 million in damage on the Virginia Tech Campus, including major damage to the Donaldson Brown Center.
Flood Advisory Terms
- Flood Watch: Flooding is possible. Tune in to NOAA Weather Radio, commercial radio, or television for information
- Flash Flood Watch: Flash flooding is possible. Be prepared to move to higher ground; listen to NOAA Weather Radio, commercial radio, or television for information.
- Flood Warning: Flooding is occurring or will occur soon; if advised to evacuate, do so immediately.
- Flash Flood Warning: A flash flood is occurring; seek higher ground on foot immediately.