Regional differences in the sinuosity of rivers in Finland

Abstract

The aim of this study is to deal with the terminology used in describing the sinuosity of rivers and to focus attention on the terms used. The term meandering only describes the quality of sinuosity, i.e. regular and smooth winding. It does not describe the degree of sinuosity. Mueller's (1968) sinuosity indices have certain drawbacks.

Using a method to determine the degree and quality of sinuosity (Mansikka­niemi 1970 a) 81 of the most important rivers in Finland were analyzed. There are about 5 % very straight, about 20 % straight, about 40 % winding, about 20 % sinuous and about 10 % very sinuous of the rivers in Finland. There is great variety in how the degree of sinuosity varies in different parts of the rivers. The rivers may be classified according to the variations in the degree of sinuosity into homogeneous, >>normal>> and heterogeneous. The lower courses of the rivers are clearly straighter than the middle and the upper courses.

Regional differences in mean river sinuosity are rather great in Finland. Mean sinuosity is greatest in the Kemijoki area, 35 %, and smallest in the rivers flowing to the Arctic Ocean, 22 %. The degree of sinuosity has very little dependence on the magnitude of the river gradient and on the width of river valley. In general it may be said that the topography of the hard crystalline bedrock is almost the only factor having the decisive effect on the degree of river sinuosity in Finland. This is illustrated by means of simple models.