Valutazione indiretta dell'entità dell’erosione nel bacino del Calore Lucano (Italia meridionale)

An evaluation of fluvial erosion entity in the Calore Lucano basin (Southern Italy)

Abstract

A methodology proposed by CICCACCI & alii (1980) was used to determine fluvial erosion entity in the Calore Lucano hydrographic basin. It is based on the use of some network geomorphic parameters (mean gradient of channel slope, drainage density, D, index and density of hierarchical anomaly, ga and ∆a) to calculate the value of suspended sediment yield (Tu) by the means of log equations. Among the several expressions proposed those containing drainage density and hierarchical anomaly index were chosen. The suspended sediment yield calculated values mainly fall into the 2nd (150-300 tons/ km² /year) and the 5th (500-1.000 tons/ km² /year) class intervals. The 55% of the studied sub-basins is carachterized by low intensity erosional processes (<500 tons/ km2 /year). It can be easily understood considering the nature of the outcropping rocks, mainly calcareus, in the Calore Lucano hydrographic basin. Particularly high values of suspended sediment yield, belonging to the 8th (2.000-2.500 tons/ km2 /year), 9th (2.500-3.000 tons/ km2 /year) and 10th classes (> 3.000 tons/ km² /year), are found for those basins closer to the valley bottom, where rocks that are more easily eroded are common. The suspended sediment yield for the whole Calore basin was also evaluated. Its value, 292 tons/km² /year, falls into the 3rd class interval. The total amount of suspended eroded sediment in the Calore basin finally resulted in 188.934 tons/year.