The cathastrofical grand rainfall, which appeared on 2.08.2005 year in the amount of 70 l/m2 caused innudation in the basin of the Wielka Puszcza stream. The high flows caused numerous damages, for example: depresson of river bed bottom from 1 to 2m and broaden about 2–4 m. In many places the river banks, asphalt road, bridge and numerous trees were destroyed. After the innudation the assessment of destructions and also the biological construction in the river banks protection before the flows were made. It was found that, at the good biological construction of river banks there is not erosion. The best plant species for the biological construction are: Alnus incana, Salix alna, S. fragilis, S. viminalis, S. purpurea and other willow. If there are in biological construction the big flows don`t devastate the banks. Unadequate to biological construction are the forest trees for example Picea excelsa because they do not protect the river banks against the big flows. Assessment of damages made by big outflow for example: channel deepening and enlargement, reservoir sedimentation and damages of river banks by stones. The trees which were uprooted by big water created in some places water falls, and at its deep holes in ...
