THE VERMONT NATURAL HAZARD EXPERIENCE AND THE NESEC STATE GEOLOGISTS

In May, 2008, the Northeastern States Emergency Consortium (NESEC, Directors of the Emergency Management Agencies for 8 states in the Northeast U.S.) invited the State Geologists in the region to form a NESEC State Geologists group. The State Geologists advise NESEC on natural hazard issues. The Vermont Geological Survey (VGS) has long been involved in natural hazard investigations and our experience played an important role in developing focus for NESEC coordination.

VGS projects include seismic hazard evaluations, slope stability studies in both surficial materials and bedrock, stream bank erosion studies, flooding, and hydrogeologic studies for contingency planning. Seismic hazard studies include a refinement of HAZUS-MH input data for Burlington to account for amplification of seismic waves within surficial materials. The potential for amplification and liquefaction was reviewed at the VT Yankee Nuclear Power Station with focus on blow counts and 22-35 feet of layered silt, silty sand, sand, and gravel. For post event mitigation planning, slope stability studies are investigated at many sites throughout the state, including a large landslide in Jeffersonville. A landslide mapping protocol that is under development will make use of new Lidar topographic data and field information to identify natural slopes susceptible to failure. In cooperation with the VT Agency of Transportation, rockfall hazards along all State and Federal highways have been analyzed: From a total of 3600 rock cuts, 150 high-hazard cuts were selected for detailed rockfall hazard ranking. Rockfall and debris flows in Smugglers Notch have been studied. Mapping of surficial geology and fluvial geomorphology in several watersheds has resulted in an improved understanding of the variation in stream bank and bed erodibility in various surficial materials and has shown the need for understanding the underlying surficial geology in order to understand the response of streams to changes in land use. Default data was used in HAZUS-MH Flood Module runs for a number of test watersheds. In Brandon, a combination of surficial geologic mapping, analysis of water well records, geophysical studies, and test borings is being used to evaluate a backup municipal aquifer prospect in case of drought or contamination of the current aquifer.