MICRO-LANDFORM IN THE LOWER BASIN OF THE TESHIO RIVER, HOKKAIDO, AND THE ATTRIBUTES OF TOPOGRAPHICAL FACTORS FUNCTIONED TO THE LAND USE

Abstract

A narrow flood plain lies along the Teshio River. The flood plain may' become flooded. The deposit of the flood plain is clay. Along the flood plain, old natural levees with a height of 2-3 meters are situated. The deposit of old natural levee is clay. However, it is covered with the humus soil. The groundwater level is high there. Right across the flood plain, there is thick peat deposits filling a concavity of back marsh. The thickness of peat layer sometimes exceeds 5 meters. Until 1963, flood plain was cultivated for soybean, oats, potato and so on. The farm houses were scattered at about 300-meters interval on the old natural levee. The main advantages for farmers in locating there were as follows; 1) the farm house can be kept out of flood damage, 2) an ample amount of water can be obtainable from the shallow well, 3) grass can be cultivated in the flood plain near the farm house. After around 1964, the demand for milk has been increased so rapidly that farmers tried to find new land for the pastures. In this district, the peat land was selected for the new pasture. The importance of peat land was re-evaluated. The merits of peat land are as follows ; the land price is cheaper, large area of land is easily obtainable, the land has not yet been utilized, the soil moisture for grass is sufficient, and lastly, when cows are pastured, it is easy to take countermeasures to keep the ground surface out of their hoof prints by lowering the groundwater level artificially down to the depth of 40-50 centimeters. The peat land could change to the pasture financially supported by the Hokkaido Kaihatsukyoku.