Atenuación del escurrimiento fluvial por bosques de Tessaria

Resumen

The flow interference effect of the Tessaria integrifolia forest in
two islands of the Paraná River, located dounstream of the Paraná-Paraguay rivers confluence, was studied.

Current velocity, suspended sediments, channel depth, water transparency, tree density, tallness and coverage, were measured in cross sections of the stream.

The atenuation of the running water by trees can be assumed as a "biological roughness" of the vegetation. It produce a strong decrease in the grain-size distribution of the islands superficial sediments as concequence of the flow interference.

In central areas of the islands occuped by forest with 20-30 ind/m*, current velocity was 10 times lower than similar (depth, slope) Coastal sites without vegetation, while the suspended load resulted lesser than the half.

The erodability coefficient decrease proportionally to the square of the current velocity diminishing. Owing to the forest extensión and coverage in rivers of the De la Plata basin, it is advisable to consider their effect during flood periods.