Coarse woody debris in mountain streams and their influence on geomorphology of channels in the Tatra Mts.

Dead wood plays important function in the riverine environment. Dead trees lying in stream channels modify the speed of the current and the shape of the channel, thus have a great influence on channel morphology. Coarse woody debris (CWD) exert influence on variation in channel width and gradient as well as promote lateral channel migration and sediment storage. In this paper we study the characteristics of dead wood delivered to two mountain streams, the Waksmundzki Stream and Pyszniański Stream in the Tatra Mts. The inflow of dead trees to the stream channels was determined with the use of dendrochronological methods. In both channels, a similar number of CWD was found – ca. 60 units per 100 m. In the Waskmundzki Stream more logs were aggregated in form of dams than in the Pyszniański Stream. The distribution of diameters, decay classes, and length classes was similar for both streams. Bank erosion is the most common cause of inflow of dead wood to the stream channel. Cross-dating of the moment of death of trees lying in the stream may indicate that inflow of dead wood to the channels is a continuous process. Fragmented remains of dead trees create geomorphological formations like dams and steps, which highly modify the channels.