Mitigation measures of debris flow and landslide risk carried out in two mountain areas of North-Eastern Italy.

The design of remediation works for themitigation and prevention of the associated risk isneeded where these geological hazards affectanthropized areas. Remedial measures for landslidescommonly include slope reshaping, plumbing,drainage, retaining structures and internal slopereinforcement, while debris flow control works consistin open or closed control structures. The effectivenessof the remedial works implemented must be assessedby evaluating the reduction of the risk over time. Thechoice of the most appropriate and cost-effectiveintervention must consider the type of hazard andenvironmental issues, and selects, wherever possible,naturalistic engineering operations that areconsequently implemented according to theenvironmental regulations or the design andspecification standards imposed by the competentpublic administrations. The mitigation proceduresconsist of five basic steps: (a) acquisition of theknowledge of the hazard process; (b) risk assessmentwith identification of possible disaster scenarios; (c)planning and designing of specific remedial measuresto reduce and/or eliminate the potential risk; (d)slope monitoring after application of remedialmeasures, (e) transfer of knowledge to thestakeholders. This paper presents two case studiesdescribing the practice for the design of the mitigationmeasures adopted for debris flow and active landslidesites in North-Eastern Italy. The first case study is adebris flow site, for which, based on observation ofpast events and numerical simulations using thesoftware FLOW-2D, the most suitable mitigationmeasures were found to be the construction of adebris basin, barriers and breakers. The second casestudy deals with an active landslide threatening avillage. Based on the landslide kinematics and theresults of numerical simulations performed with thecode FLAC, hard engineering remedial works wereplanned to reduce the driving forces with benchingand by increasing the available resisting forces usingjet grout piles and deep drainage.