Avalanche developing process after forest cutting on heavy snow slopes

Wien

1982

S. 187-197

10 Abb.

Unselbständiges Werk

200004897

The uprooting process und decrease in stumps after cutting on the mountain alopes in the Naeba Mountains, South Niigata Prefecture, where seasonal snow lies between 3m and 5m deep on the average, were followed 9 years regarding their work in controlling avalanches. 1. Stumps with a higher center of gravity, or a greater heigh-to-diameter ratio, decreased in number from earlier years after cutting than those in lower ratio. Stumps started to decline in number at 8 years after clear cutting and they decreased to half in 10 years, as a result of decay and uprooting due to large snow pressure. 2. In general the total desplacement of inclined snowpacks in each winter increased with decreasing stump density. Ground avalanches occurred on the lush grass clopes where seedlings had been planted just after clear cutting, only when the stump densities decreased to about 100 per ha. On the bushy uncontrolled slopes where no trees had been planted after clear cutting, no avalanches occurred despite decrease of stumps and an increase of snow displacement, because some of the bushes grew to a greater size, shich was enough to check release of avalanches. 3) No avalanches occurred on the slopes where different intensities of thinning had been tried, while the larger parts of clear cut slopes were developing of stumps and newly planted seedlings. In order to regenerate mountain forests in such heavy snow areas, it is preferable to retain effective snow-supporting stands by treatment like thinning rather than clear cutting.