The effect of slope angle on the development of type a and type b channels of rinnenkarren with field and laboratory measurements

The relation between the inclination and the quality of the bearing slope, and the channel type and channel density of various rinnenkarren (type A and type B channels) was investigated. On the bare karren slopes of Totes Gebirge, the connection between the densities of type A and type B (type A channels have no tributary channels, and they are smaller; type B channels have tributary channels, and they are larger) channels and the slope angle was studied, while in laboratory the relation between the number of rivulets forming the channels and the slope angle and the quality of slope was analysed. The density of type A channels increases with the increase in the slope angle, while that of type B channels decreases. In the laboratory the number of rivulets on the various parts of the slope was studied on glass, gypsum and metal plates between 5 and 50° (as well as on metal plate between 1 and 70°). The dip angle of the bearing slope was modified every 5°. The number of rivulets increases with the slope angle mainly on the upper part of the slope and on the metal plate. The number of rivulets decreases towards the lower part of the slope in the case of the same slope and the same slope angle. The number of rivulets (and thus the number of channels) depends on the speed of water flow and the roughness of the surface. On a slope with a small dip angle (smaller than 20°), few rivulets and channels develop and, thus, rinnenkarren systems with large catchment areas may form whose main channels develop into large, type B channels. On slopes with a large dip angle (greater than 30°), numerous rivulets develop even at the beginning of channel development. Because of large rivulet density, channels with small catchment area and thus small-sized (type A) channels may develop. On the karren slopes, two models of channel development are possible: according to model 1, on slopes with a continuously smaller dip angle, the beginning of channel development is increasingly different, thus rinnenkarren systems form which are built by main and tributary channels. In the case of an increasing slope angle, this tendency is less and less valid. On slopes with an increasingly larger slope angle, the beginning of channel development will not be different. According to model 2 (based on the laboratory model), the rivulets that developed on the upper part of the slope join on the lower part of the slope. In this case the initiation of channel formation of the main and tributary channels of the rinnenkarren systems is similar. On the bare slopes of Totes Gebirge, model 1 can be regarded as the dominant one.