Treesearch

The annual continual occurrence of surface slides in the basin was estimated by modifying the estimation formula of Yoshimatsu. The Weibull Distribution Function revealed to be usefull for presenting the state and the transition of surface slides in the basin. Three parameters of the Weibull Function are recognized to be the linear function of the area ratio a/A. The mapping of the hazardous zones could be successfully done using the stream line distribution map and the relief map.

Japan is one of the most snowiest regions in the world. Particularly the mountainous area of Honshu (the main island), along the Japan Sea has heavy snow in winter. In some places, snow piles up more than four meters and the ground is covered with snow about one hundred and forty days a year. The sugi tree is widely planted in snowy regions, and snow-pressure damages, such as basal bending, occurred in juvenile stands, and after that crown snow-damage, such as stem breakage, happen in younger stands about 10~30 years-old. Basal bending is formed by the difference in recovery rate between...

Two kinds of shearing stress meters (type A and type B) were set on the channel bottom in the Arimura River and the Mochiki River on Mt. Sakurajima. Volcanic mud flows take place there about 100 times a year. The results of the surveys demonstrated that the actual shearing force of a volcanic mud flow on Mt. Sakurajima was from 0.46 to 2.50 kgf/cm2. The actual impact force caused by collisions of big stones, which were contained in a mud flow, with the channel bottom was calculated theoretically at about 15 times greater than the dead loads of the stones. The collision of stones in a mud...

The purposes of this study is to obtain exact knowledge of the influences on friction angle during shear by shearing speeds. Ring shear tests on sandy and clayey materials have been carried out with a newly developed High-speed High-Stress Ring Shear Apparatus to examine if there are some changes in the frictional behaviors of these materials at high shearing speeds of O.O1cm/sec-100cm/sec and high normal stress of 0-3.8kgf/cm2. Samples used for tests were glass beads, tennis court sands in the university campus, the Toyoura standard sands (uniform beach sands) and bentonite clays. All...

Abstract - Erosion resulting from logging and road building has long been a concern to forest managers and the general public. An objective methodology was developed to estimate erosion risk on forest roads and in harvest areas on private land in northwestern California. It was based on 260 plots sampled from the area harvested under 415 Timber Harvest Plans completed between November 1978 and October 1979. Results confirmed previous findings that most erosion related to forest management occurs on a small fraction of the managed area.

Abstract - Because of high costs or complex logistics, scientific populations cannot be measured entirely and must be sampled. Accepted scientific practice holds that sample selection be based on statistical principles to assure objectivity when estimating totals and variances. Probability sampling--obtaining samples with known probabilities--is the only method that assures these results. However, probability sampling is seldom combined with appropriate estimators to determine suspended sediment loads. Many current load-estimating methods, therefore, have unknown bias and variation making...

The relationship between forest practices and anadromous fish production has continued to be debated during the intervening decades without a clear resolution. The issue is complicated because there are activities in addition to forest practices that affect anadromous fish production. The offshore fishery removes a large portion of those adults that would return to the streams to spawn. Instream fishing removes another portion of those spawners. Dams on the rivers reduce peak streamflows that influence channel morphology and sediment transport, as well as modify low-flow discharges in the...

Tree roots provide important soil reinforcement that impoves the stability of hillslopes. After trees are cut and roots begin to decay, the frequency of slope failures can increase. To more fully understand the mechanics of how tree roots reinforce soil, fine sandy soil containing pine roots was placed in a large shear box in horizontal layers and sheared across a vertical plane. The shapes of the deformed roots in the sheared soil were explained satisfactorily by an equation that had been developed to model the deformed shape of artificial reinforcement elements, such as wood dowels,...