Assessments on debris flow distribution, triggering and evolution in the Dolomites area (North-Eastern Italy).

Debris flows are considered among the most dangerous and destructiveprocesses that affect mountainous areas all over the world. In Italy debris flows are verycommon in all the Alps, and in particular in the Dolomites (North-Eastern Italy). Thispaper concerns the study of debris flows distribution, triggering and evolution in theCortina d'Ampezzo area, located in the Eastern Dolomites, sample study area over about30 years in the context of National and European research projects. The morphology of thearea is characterised by sub-vertical dolomitic cliffs and a thick talus developing from theirbase to the valley bottom. Through the analysis of aerial photographs, 325 debris flows,both channelized and hillslope type, have been detected. They all originate at the rock cliffbase and develop towards the valley floor. The morphometric and hydrologic parametersof the rock headwater catchment and of the transport and deposition zones have beenmeasured for each debris flow, as well as the recording of the rainfall responsible for thetriggering process. The debris flows have been divided according to their type (hill-slopeor channelized) and rock headwater catchments which do not give rise to debris flow havebeen considered separately. All the collected data have been statistically analysed gettingsome general conclusions especially regarding the headwaters that do not originate debrisflows. The mean channel lengths increase over the years, and this would seem inconnection with an increasing trend of total annual rainfall and frequency of maximumintensity since the late 1980s.