River Bed Form in a Granitic Mountainous Catchment : A Case of the Source Area in Kurose River, Hiroshima Prefecture

In order to clarify spatial variations in a river bed form in a granitic mountainous catchment, we surveyed topographically a steep river on a source area of Kurose River in which the debris flow occurred in 1999. Firstly, we found that the spatial variation in erosion-deposition process on the steep river. Both of the lower stream and upper one held much sediments with large gravels (φ>2m). On the other hand, the middle stream exposed mainly the bedrock. Secondary, we confirmed spatial distribution of river falls. The height of river fall on the upper stream rose with the increase of river gradient. On the contray, the frequency of falls was constant in spite of inclination

NO_3^--N Flux of Streams in the Setouchi Region : Effects of Fruit-Farmland Area, Water Reservoir, and Alluvial Fan

To confirm the effects of fruit-farmland area, water reservoir, and alluvial fan on nitrate load in short streams, we measured runoff and collected water samples at five or eight sites in each of four streams, Seto Inland Sea catchment. Nitrate load of the streams increased with increasing ratio of fruit-farmland area. At a downstream site of water reservoir, nitrate concentration showed a slight decrease. On the area widely domi- nated by alluvial fan, it assumed that groundwater pollution by nitrate-nitrogen is accelerated with groundwater recharge of stream water. It is necessary for conservation of water resources to consider function of these effects as well as river-groundwater mixing