We introduce a simplified crossing wood drain disperses rain water concentration and is used to protect the road surface from erosion due to flooding over the unpaved road. The efficiency of a simplified crossing wood drain was also investigated. A structure of simplified crossing wood drain can be produced within 10 minutes and installed within 18 minutes. The cost of the this product is 1/5 of that of the existing crossing drain product. The production and installation cost can be reduced according to dexterity. In the context of such applications, the degrees of damage for a rubber pad, which preventing the rain overflow, were varied according to their materials. A type of 8.2㎜ thick fabric rubber was the most suitable in this study.

In case an average accumulation of the investigated area is 200㎥/ha with cutting age of 80 years applied, annual workload will be 77ha and require 5 teams; each team consisting of 5 persons, enabling stabled supply of lumbers of 15,500㎥ every year. If one cutover is less than 2ha with cutting age of 80 years applied, it's possible to protect the peculiar ecology and secure stabled labor, workload and lumbering. It may become model forest out of tropical forest management which is controversial all over the world. Of course this presupposes construction of access roads.

Forest management starts from forest road facility, which is designated as generation source of muddy water in mountain stream during initial stage of establishment. Therefore, this study reviewed the effect of suspended sediment generated in forest road surface on the muddy water in mountain stream with respect to marsh area of forest. As a result, characteristics of outflow of suspended sediment was understood, and it was judged that generation of suspended sediment due to establishment of forest road is diluted by mountain stream this charged from drainage area so as to have small effect on muddy water in total mountain stream.

Boeun-gun is hard to develop, because of large numbers of mountains and vast distribution of limited development districts. However it is easy to access from the entire country, and there are large conservation area such as national park and dams. Short-term plans such as attraction of tourists can be established using these advantages. Long-term plans can be planed with stable establishment of continuous considerations and supports. These supports will be rewarded while it demands some time and costs. Private owned mountains can be converted from negligence upkeep of property to utilization of mountains with basic consideration of mountain conservation. This may contribute the essential function of mountain.

Suspended sediment outflows mainly by natural situation and artificial action and affects in down-stream. This research studied suspended sediments origination in forests size and mountain stream for natural situation, density for artificial action, and measured the size and possible quantity of suspended sediments origination and studied obstruction method of the generation by artificial action. As the result, I found that the size of generation is about 2～3% of forest size and the forest size which is affecting bare area of valley is about 1～2ha. In addition, possible outflow segments quantity by artificial facilities is assumed to be maximum 200ton/ha and abstract of mountain incline for mountain development needs minimize bare area valley by make right angle with minimum size.