畑地における耕盤層の存在が流出特性へ及ぼす影響

抄録

By climate change in recent years, it is often experience a local heavy rainfall at the eastern part of Hokkaido, which is well known as field crops thriving. A local heavy rainfall cause severe sediment erosion over the farm fields. We provided a study site which is located at the Mokoto River basin in this area. It is known that the presence of furrow pan layer, which is generated with plowing a field by tractor and have few drainage property. It is also known as a snowy cold region where air temperature is less than or equal -20 degree and soil freezes up to 40 cm depth.

The aim at this research is to evaluate occurrence conditions of the surface flow on the farm field, which is closely related to sediment outflow from fields to river. We apply the saturated-unsaturated flow model to estimate runoff from farm fields that is configured from a variety soil layer, such as furrow pan layer, frozen soil layer. Results of a numerical simulation of the field with furrow pan layer reproduced the occurrence of surface flow over the fields but the surface flow was unrecognizable over the field without furrow pan layer. Furthermore, few snowmelt intensity resulted in the surface flow over the field with frozen soil layer.