In response to extreme rainfall events of February 1996 (380 mm, less than 24 hours) landslide scars spread along the western peak zone of Tijuca massif, between Papagaio and Taquara peaks. Debris flows and shallow failures left behind finger-like scars before feeding extensive rock debris avalanches along the main river channels which drain toward the baixada of Jacarepaguá. Finger-scars (n= 93) vary in size, shape and surface materials (bare rocks, weathered rocks, saprolite or colluvium). An erosive feature prevail on steeper slopes, while a depositional zone may be developed in the lower portion, particularly when associated with slope breaks at hanging plateaus or adjacent valley bottoms. Erosion is dominated by the action of hortonian overland flow. Gullying tend to develop onto the depositional zone and may extend over the upper erosive zone wherever soil is available for transportation. Rocky blocks remain as lag deposits into the gully, particularly in the plateaus and valley bottoms filled up with landslide deposits.
Detailed field observations and erosion measurements have been conducted in a representative landslide scar of February 1996, which is located in forested-slopes in the eastern side of Papagaio peak. The average sheetwash erosion is on the order of 10,5 ton/ha/year; ranging from 30 ton/ha/year, on bare soil to -0,056- ton/m2/year on the interrill vegetation regrowing area. In the depositional feature, the average gully erosion rates (measured for the period of august 1997 to april 1999) is on the order of 4.450 ton/m2/year.
Erosion susceptibility and rates will tend to increase around the scar, as landslide-clearing sites promote forest deterioration and decay of root strength due to border effects (microclimatic changes), especially in larger scars. In ten years forest vegetation will not be fully recovered in their functional aspects that regulate both hydrological and mechanical soil properties on forested slopes.