| This paper analyzes the Lagarelle Creek watershed, situated in the
Municipality of Vallo di Nera, in the eastern Umbria region, central Italy.
In this part of the Region, narrow valleys and very steep slopes
characterize the morphology of the Appennine ridge. The presence of
strongly-tectonized rocky masses, subdivided by several joint systems, is
the main cause for the formation of sorted debris deposits, which accumulate
mainly along the topographic convergences. This determines the conditions
for possible events of debris flows.
According to previous studies, the basin of the Lagarelle Creek, has been classified as an area prone
to a high hazard of debris flows (Regione dell'Umbria – C.N.R. I.R.P.I., 1996). For this reason, systematic studies have
been carried out on the whole watershed which, in this first phase, have examined
the definition of the geological and morphological features of the zone, by
means of the acquisition of cartographies and of field surveys, and the
elaboration of the topographical data of the basin, by means of a digital
model of the terrain.
Once the potential triggering areas of debris flows were identified, an
assessment of the mobilizable volumes possibly involved in a debris
flow event was carried out. To perform such an assessment both the
geomorphologic method proposed by Hungr (Hungr et al., 1984) and the
empirical relations calibrated on debris flow events of the alpine arc were
applied. The results obtained were compared with those derived from
information supplied by the inhabitants of the small mountain village, who
have described in detail the most important events of the last century. |