林道の配置計画について (I) : 端点除去法

Abstract

林道通過予定点を任意の方法で結んだ路網によって集材可能となる林分の面積, あるいは一定歩行時間内で到達できる林分の面積を, 減少させることなく, 乙の路網の不要端点を除去し必要最低限の路網を求める方法について考察した。この方法で得られる結果は最初の路網の一部分であるので, 路網の与え方によって結果が異なる。ここではすべての林道通過予定点を開設評価値の総計が最小となるよう結ぶ路網, 任意の点を基点として他のすべての通過予定点とを最小評価値で結ぶ路網, いくつかの重要な通過点を選びそれらを開設評価値の総計が最小となるよう結ぶ路網等について適用し, 林道総延長, 平均集材距離, 平均スパン長等を算出し評価を行った。

We shall try to analyze planning methods for forest roads in a mountainous working area that is a few hundred hectare. In planning of forest road network, it is usual to compare with many plans about the cost of road construction, the skidding cost, the possible skidding area, average skidding distance, average walking times from road to working place, and etc.. These methods draw a minimum network without decrease of an available working area, eliminating an end point of network which available area is avail to other pass points for skidding or walking. The result is different, if the original network is diverse, so we try to plan for some network. Fig. 1 shows the shortest pass between P5 and the other points, Fig.2 shows the shortest road network and Fig. 3 shows the shortest spanning subgraph of select points for better landing points. It is considered that Fig.2-3 or Fig.3-3 is better than the other road network, judging from the valuation of road construction per skidding area.