Dendrogeomorphological analysis of shore erosion along Bolsena lake (Central Italy)

Abstract

Dendrogeomorphological research was conducted along a volcanic caldera lake of Bolsena in central Italy, Latium region, in order to investigate the erosion process that affects its coastline. Most of the trees sampled were black poplars ( Populus nigra L.) with root systems differently exposed. The cores taken from trunks show growth stress (suppression) at different times according to the distance of the tree from the shoreline. Results of the morphological analysis of the root systems were used as a qualitative estimate of the erosion process developing an erosion map of the lake's shoreline. The dating of suppressions was used to calculate the main horizontal erosion rate at different shoreline sectors. The most intense erosion was recorded on the southern and northern shore, affected by the strongest and long-lasting winds (mean erosion rate at southern coast=0.092 m/year, northern coast=0.064 m/year, eastern coast=0.049 m/year, western coast=0.028 m/year). The age of the living trees along the shore points out that the erosion started at least in the 1970s (one of the highest lake level episode) and it is still in progress.