WEST VIRGINIA FLOODS AND DEBRIS FLOWS, JULY 2001

Training thunderstorm cells in a mesoscale convective complex triggered substantial flash flooding in southern West Virginia and adjacent Virginia on 8 July 2001. Several official NWS stations recorded 120-135 mm of rainfall in 3-6 hr, with rainfall intensities of up to 50 mm/hr. Unofficial data suggest that > 175 mm may have fallen locally. Ensuing events left 2 dead and preliminary damage estimates of up to $150 million in 23 counties.

The hydrologic and geomorphic response to this precipitation was regionally diverse. Floods exceeding a 100 year recurrence interval occurred in the headwaters of the Tug Fork and Guyandotte rivers and similar magnitudes may have been reached in adjacent drainage basins. Low-lying communities in the narrow valleys of the Appalachian Plateaus were hammered by high-velocity stream flows with little warning. Most of the damage stemmed from these water-dominated floods. Debris flows were most common in the New River Gorge, but it is not yet clear whether their distribution relates to local geology and geomorphology or to variation in precipitation intensity.

Although local residents have pointed toward timber and coal-mining practices as "the" cause of flooding, further study will be required to evaluate the relationship between land use and flood intensity or slope stability. Reconnaissance suggests that active mines experienced dam breaks and slope failures, which exacerbated local flooding, but that fully reclaimed mine sites presented no exceptional downstream risk.