  Mountain river torrents and snow avalanches generate human and material
damages with dramatic consequences. Knowledge about natural phenomenona is
often lacking and expertise is required for decision and risk management
purposes using multi-disciplinary quantitative or qualitative approaches.
Expertise is considered as a decision process based on imperfect information
coming from more or less reliable and conflicting sources. A methodology mixing
the Analytic Hierarchy Process (AHP), a multi-criteria aid-decision method, and
information fusion using Belief Function Theory is described. Fuzzy Sets and
Possibilities theories allow to transform quantitative and qualitative criteria
into a common frame of discernment for decision in Dempster-Shafer Theory (DST
) and Dezert-Smarandache Theory (DSmT) contexts. Main issues consist in basic
belief assignments elicitation, conflict identification and management, fusion
rule choices, results validation but also in specific needs to make a
difference between importance and reliability and uncertainty in the fusion
process.
