Sediment Yield and its Interannual Variability are Underestimated in
Supply-Limited Mountain Basins with Short Records
Abstract
Climate and sediment supply are critical factors for the sediment output
of geomorphic systems. It is known that non-linearities between forcing
and sediment mobilization may lead to dampened or shredded environmental
signals in sediment flux measurements. But it is unclear under which
circumstances environmental signals, such as extreme events or climate
change, are transmitted and measurable downstream. We used a sediment
cascade model and a stochastic weather generator to quantify climate
forcing effects under a range of sediment supply regimes in a
debris-flow catchment in the Swiss Alps (Illgraben). Sediment yields
estimated from short records have high uncertainties both in terms of
mean and interannual variability, and tend to be underestimated
especially in supply-limited systems, where also long-term memory
effects driven by sediment storage are evident. Consequently, climate
change impact assessments based on short duration records may be grossly
inaccurate, and should be extended with uncertainty estimation.