Valutazione quantitativa dell’erosione in un bacino idrografico mediante l’analisi tridimensionale

Quantitative evaluation of erosion in a drainage basin by means of three-dimensional relief analysis

Abstract

The aim of this work is to describe a research method allowing indirect quantitative evaluation of river erosion in a drainage basin, in the interval from the late Glacial to today. In order to quantify erosion effects, the author measured the volume of solid material brought down from the basin by the waterways from the beginning of the post-glacial erosive phase. In order to do this, he compared the current topographic surface as taken from existing maps (scale 1:10 000) and from that of the late Würm regarding the last withdrawal phases of the Pleistocene glaciers. The late Glacial surface was reconstructed by means of morphological correlations based on specific field surveys aimed at identifying the strips of the old surfaces and recognizing the post- Würm river forms. The volume between these two topographical surfaces corresponds to that of the material brought down by the waterways during the long period considered. Comparison between the two surfaces was carried out using computer-based reading techniques and spatial analysis. The value obtained, 680-730 m³/km²/year, expresses the mean total erosion from the late Glacial to today, in a basin essentially composed of clayey rocks. In spite of the unusual time dimension, this value is not far removed from those already reported in the specialized literature.