Debris-Flow Hazards in the Blue Ridge of Central Virginia

摘要

The June 27, 1995, storm in Madison County,Virginia produced debris flows and floods that devastated asmall (130 km~2) area of the Blue Ridge in the eastern UnitedStates. Although similar debris-flow inducing storm eventsmay return only approximately once every two thousand yearsto the same given locale, these events affecting a similar small-sized area occur about every three years somewhere in thecentral and southern Appalachian Mountains. From physicalexaminations and mapping of debris-flow sources, paths, anddeposits in Madison County, we develop methods foridentifying areas subject to debris flows using GeographicInformation Systems (GIS) technology. We examined therainfall intensity and duration characteristics of the June 27,1995, and other storms, in the Blue Ridge of central Virginia,and have defined a minimum threshold necessary to triggerdebris flows in granitic rocks. In comparison with thresholdselsewhere, longer and more intense rainfall is necessary totrigger debris flows in the Blue Ridge.