Rainfall characteristics for periglacial debris flows in the Swiss Alps: past incidences–potential future evolutions

摘要: Based on observational meteorological data since A.D. 1864 and tree-ring records of debris-flow activity, this paper assesses changes in rainfall characteristics their impact the triggering geomorphic events a high-elevation watershed Swiss Alps end Little Ice Age. No trends are visible frequency heavy events, but we observe reduced number heavy, short-lived rainfalls summer concentration advective storms is recorded late early fall 1980s. These conditions resulted cluster debris flows decades twentieth century lowering activity mid 1990s, may be mirroring observed persistent high-pressure systems over Alps. We also intra-seasonal differences system response reflecting state permafrost body source area flows, allowing for very small to released by limited inputs (<20 mm) June July. The same quantities rain will not trigger August or September, when thick active layer capable absorbing water. With projected amplitude climatic change, seasonality, return intervals volumes likely altered. RCM projections based IPCC A2 scenario suggest decrease which most result (further) reduction overall leaving more time sediment accumulate channel. Such an increase channel accumulation rates along with destabilization steep rock-glacier likely, turn, exert control ultimately from areas during future events. Observations adjacent catchments that extremely large beyond historical experience, could occur at study site similar Valais originating periglacial environments.