Effects of the tributary channel and water catchment area on rinnenkarren development (Totes Gebirge, Austria)

ABSTRACT The goal of this study is to interpret the cross-sectional increases of rinnenkarren systems with the use of analytical model and CFD simulation. In rinnenkarren, water accumulation from the catchment was approximated using an analytical method based on field data. The length of eddies appearing at tributary junctions was studied by CFD in model channels. The results of the analytical and numerical models were compared against morphometrical parameters of rinnenkarren surveyed in the Totes Gebirge (Austria). It is found that there is a relationship between catchment size and channel development. Along small catchments, channel development is random. However, channel development along large catchments is controlled by water concentration. Decrease in the slope angle of the catchment results in an increase in the volume of water entering the channel and development of tributary channels. When water inflow is not concentrated in a single place, several smaller tributary channels emerge. When it is concentrated, only one large-sized and long tributary develops. At the junctions of large tributaries significant vorticity was identified in the CFD models. In addition to the previous model studies, the similarity between the lengths of the simulated vorticity sections and the local field hollowings was revealed.