In forest, we planed roads for recreation with a digital map and studied the most suitable route of them using a genetic algorithm (GA) and Dijkstra method to do total evaluation of them efficiently. Considering earth-volume and safety of driving, we confined them to one-way traffic and one-lane road in this paper. We planed two roads to go and back in a different route. The evaluation factors are the scene in a forest, the view, the viewed frequency, the slope gradient, the distance between two roads, the variance of ground height, the length of roads and the longitudinal slope. One calculation of this method is to settle two intermediate points per one route, and to search between four points, beginning point, two intermediate points, and end point, in Dijkstra method. Changing coordinates of the intermediate point, we attempt a solution of the most suitable one by a simulated evolution of GA. We obtained the optimum solution, calculating in 30,000 times. It took about 45 hours. We can consider the factors that are evaluated with looking out the whole area and do total evaluation. And we can confirm the efficiency of GA. The future problems are studying how to select the factors and weights that justly fit the size of the grid cell and settle intermediate points.

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This study was conducted to understand the change of water quality in a stream caused by forest road construction by measuring suspended sediment concentration and turbidity at surveying points A, B, a mountainous watershed unaffected by forest roads, and C, affected by forest road. The results of the measurements were analyzed in relation to rainfall factors and discharge. The results were : 1) Turbidity measured with suspended sediment concentration was confirmed to have a high correlation (r=0.984) with suspended sediment concentration. Turbidity was regarded as a possible subsidiary index of suspended sediment concentration. 2) Suspended sediment concentration originating in the stream of the mountain watershed was more highly affected by 1 hour rainfall intensity than 10 minutes one. In the case of the production of sediment discharge from the road surface and/or slopes of forest roads, the suspended sediment discharge in the stream was more highly affected by 10 minutes rainfall intensity than 1 hour one. Also, when rainfall intensity increases for a short period, the maximum suspended sediment concentration precedes peak discharge because of an inflow of much sediment from the road surface and/or slopes of forest roads at the same time. 3) The relationship between discharge Q and suspended sediment concentration SSC, in the case of the production of sediment discharge from the mountain watershed, was confirmed to be expressed as SSC =aQ^b (a, b : coefficients). But, in the case of the production of sediment discharge from the forest road, the discharge and suspended sediment concentration was not confirmed the direct relationship. In that time, it was ascertained the marked hysteresis effect.

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For an improved mechanized methods of logging, the method for estimating the optimal working area, on which a certain kind of logging operation could be carried out most economically is discussed through the use of an interactive computer-aided simulation. A procedure is presented to solve for the most efficient operating flow system given alternative modes of ground-based harvesting, these were combined feller-buncher, skidder and processor. The technical features to solve this problems can be exclusively approached on a productivity basis by comparing operational queuing delay time in relation to trade-offs of the equipment's installation, values of varying skidding distance and out-put, and harvesting restrictions. The results showed that the skidding distance varied as the density of transshipment yard points in number/ ha and the type of skidding road nets, and also the most suitable working system would be considerably influenced by the opimal skidding distance. Then, the optimal skidding distance was estimated to be about 400〜500m. Elements characterizing working process were also investigated, which were the operating availabilty k_s, where k_s meant a ratio of productive hour per scheduled operating hour, and the operating duplicating ratio C_s defined from the rate of operating overlap time for processing some works simultaneously in the fixed scheduled period. Then, in the method using these elements, we could lead to the development of production equations for all phases of logging.

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The tram-car was developed to mechanize forestry work and to improve safety in steep mountains. This machine utilizes rail-support system to transport workers, machines, materials, and wood in the forest. The features of this machine include three-wheel drive (3WD), hydraulic driving gear system, water-cooled 4-cycle, 3-cylinder diesel engine with a modified deep oil pan, fail-safe system, two rails (main-rail and sub-rail) and a prefab rail method. We confirmed satisfactory safety through performance tests on traction, braking and rail intensity. Then, we constructed tram-cars in Higashishirakawa Village and Shirotori Town in Gifu Prefecture, and investigated the construction work. Work element analysis showed that workers spend much time removing obstacles, adjusting rail position and waiting. This indicated the necessity of mechanization and greater efficiency for the construction work. In addition, the main factors affecting work efficiency were the angle of inclination in the case of no obstacles and the obstacle removal when there are obstacles. Finally a comparison of the construction efficiency among tram-car, mono-rail and forest road showed that tram-car is useful in steep mountains.

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Forest roads play an important role as public transportation as well as wood transportation in mountainous regions where public roads are not enough. The objective of this study is to evaluate road networks in six villages located in the center of the Kii Peninsula using network analysis in order to make them effectively formed. The α-indices showed that lower-standard roads did not form a circular type network but a go-back type network in this region. The β-indices were 1.0 or a little more than 1.0 and it means that alternative routes exist in some areas. In most areas, however, it is still difficult to find an available alternative route when traffic is held up by slope failures. According to the analysis with the η-indices, it was found that the network was subdivided mostly at the level of a village road. According to the evaluation based on the Crofton's formula, the connectivity of road networks between Simokitayama and Nosegawa villages and between Simokitayama and Otou villages was low. Conversely, the one between Tenkawa and Nosegawa villages was high. Therefore, road construction as well as improvement of the existing roads is required to improve the connectivity of roads, especially when they cross over ridges.

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After the logging, skidding roads are abandoned and left to be reforested under the natural revegitation process. In this, we studied on that natural reforestation process. The studied sites had been abandoned for 11-12 years, partly gravelled for track transportation, partly seeded by meadow grass for erosion controle. The results are as follows. 1) The plots where the height of cutting slope is lower than 1 m : The slope is stable and covered by natural vegetation roughly. The road surface is thoroughly covered by susuki (Miscanthus sinensis Anderss). The gravelled part, seeded part and track trace part are less covered with susuki. 2) The plots where the height of slope is 1〜3 m: The vegetation coverage on the slope is about 30%. Much amount of the colluvial soil is at the foot of the slope. Susuki is growing on the vally side of the road. 3) The plots where the slope is heighter than 3 m : The vegetation coverage on the slope is very small and susuki is not found on the road. Then the conclusions are as follows. 1) The skidding roads whose cutting slope is lower than about 1 m are naturally reforested. 2) The scarification of road surface is effective for introduction of natural visitation of vegetation cover. 3) Susuki is suitable for revegitation on road surface. 4) Existing trees should be reserved as seed tree near the road.

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