Abstract
A simple modeling method for estimating the outflow from the bottom of a snowpack during the spring melt season is proposed; this model can be used in distributed applications for preventing snowmelt-induced landslide hazards in mountainous regions. A temperature-radiation index melt model (Konya et al.,2004) is applied to the results of heat balance observations carried out at Oshirakwa in Niigata Prefecture in the winter of 2007/08 in order to calibrate the coefficients of the model. Estimated global radiation using a locally calibrated Angstrom model (Yang and Koike,2005) with duration of sunshine at the nearest AMeDAS station can be used as an input to the melt model. The percolation of water through a snowpack is modeled using a linear reservoir with a discharge coefficient that varies with a change in the snow depth (Nakatsugawa et al.,2004). Moreover, a new parameterization of the discharge coefficient with positive degree-day is applied for this percolation model. It is found that this combination of a melt model and a percolation model yields good estimates of outflow from the bottom of a snowpack at 1-hour intervals in the latter stage of the melt season when the following three input data are available : air temperature, global radiation (or duration of sunshine), and rainfall intensity.
