A continuous frozen ground index for flood forecasting

Floods occurring on frozen ground are a serious problem in the Pacific Northwest. These floods cause much damage and are costly to control. Timely warning of potential runoff amounts from frozen ground events can prevent some losses by allowing time for raising of levees or other property protection methods and evacuation of people. A frost index that will reflect the effect of frost on potential runoff from the basin was developed. This Index included the effect of snow depth, the current days temperature, and the previous days Index. The Index was applied to both frozen and unfrozen ground runoff events for Missouri Flat Creek near Pullman, WA and McKay Creek near Pilot Rock, OR. The Index proved useful for determining the runoff enhancement potential of these events. The Northwest River Forecast Center is currently using the Index as a guide in running the forecast models.