WOODY DEBRIS CHARACTERIZATION IN A SMALL BASIN WITH ARAUCARIA FOREST

The effect that wood deposited in a river, woody debris (WD), causes on its hydrogeomorphic processes depends on the dimensions of the wood and the channel. Studies related to WD are still very rare in Brazil. Therefore, the objective of the present study was to demonstrate the feasible methodology of field survey and to characterize the WD along a natural channel inside the Perdizes stream basin, located in the municipality of Cambará do Sul, Rio Grande do Sul state. The study basin is characterized by the Mixed Rain Forest (Araucaria Forest), in a good condition of conservation. The final part of the stream, from its mouth, was divided into 3 sections. The WD field survey within these sections included orientation against the channel, size, origin and location. A topographic survey was carried out to construct the stream longitudinal profile. The results show that the volume and frequency of WD are directly related to the presence of araucaria in riparian vegetation. The total WD-quantity was compared with other rivers around the world. Furthermore, it was observed that the highest proportion of WD was oriented parallel to the flow direction, confirming an already known trend. In addition, the obtained results permit to say that the present methodology of field survey and of statistical analysis is useful for the DW dynamics study.