Changes in properties of watershed and its conservation due to changes in land use in mountainous rural area

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In this project, investigations and researches have been carried out for the management and development of mountainous rural area, where reduction of population and moving out of the young people are serios problems. The results are summarised as follows.(1)The investigations of disasters on farm lands in such area showed that smaller but more disasters have occurred in comparison to the areas without such problems.(2)Changes of land use due to devastation of farm lands and forests, or reclamation of farm lands for the developments of the area, have changed the type of vegetation, soil properties and drainage systems, which leads to the changes in the components of hydrologic cycle in watersheds such as storm runoff, low-flow runoff and evapotranspiration.(3)Peak discharge and direct runoff from reclaimed farm lands were increased in comparison to the forest catchment. In the terraced paddy field catchment, peak discharge was greater, while direct runoff was as same as in the forest catchment.(4)Comparison of draft discharge for a wet year showed that the amount of discharge in the forest catchment was greater than in the farm land one, but it was decreased for a dry year. It might be caused by the reduction of evapotranspiration which was influenced due to the changes in land use.(5)The properties of rill network and mechanism of rill initiation have been investigated for land conservation and a routine to decide the optimum length of slope was developed to prevent the soil erosion and rill formation.Finally, we have proposed the ideas for the management and development of mountanious rural area in Japan.