Free Meanders of Major Rivers in Northern Hokkaidô

The writer studied the free meanders in the lower flood plains of the Teshio, the Koetoi (Makubetsu), the Karibetsu, the Yûbestu, the Shokotsu, the Tokoro, the Abashiri and the Musa (Shibetsu) rivers by the analysis of aerial-photographs and topographic maps, and by hydrological data and field investigations. The following points are his conclusions.1. According to different hydrological and soil conditions, the preceding rivers can be classified into the next two types depending on their free meander forms.a) In the plains of the Teshio, the Koetoi, the Karibetsu and the Musa rivers the meander rates (ρ) are less than 0.5 (meander rate : = (L-W) /L, where L is meander wave length and W is meander wave width).b) In the plains of the Yubetsu, the Shokotsu, and the Tokoro rivers, the meander rates (ρ) are more than 0.5.2. The meander rates of meander scars and scrolls in the flood plains are nearly the same as the preceding meander rates.3. As the results of the observation on those meander scars and scrolls, these river channels have been shifted toward the back of the loop by cut-offs of meander and slided to the front of spur of each meander loop compensatively.4. The range of the shifting is nearly equal with the width of each meander belt.