Numerical Investigation of Sediment‐Yield Underestimation in Supply‐Limited Mountain Basins With Short Records

Abstract

Climate and sediment supply are critical for geomorphic systems. It is known that complex relations between such forcings and sediment mobilization may lead to dampened or erased environmental signals in sediment records. But it is unclear under which circumstances environmental signals are transmitted and measurable downstream. We used a numerical approach consisting of 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). We show that sediment yields estimated from short records are highly uncertain both in terms of mean and interannual variability. Furthermore, sediment yields tend to be underestimated in supply‐limited systems, where also long‐term memory effects, driven by the history of sediment storage, are evident. Consequently, determining geomorphic system response from short records may be grossly inaccurate and should be extended with sediment supply detection and uncertainty analysis.

Controls on Sediment Transport From a Glacierized Catchment in the Swiss Alps Established Through Inverse Modeling of Geomorphic Processes

“…Despite being visually evident in Fieschertal (Figure 2), we omit mass wasting processes that introduce sediment to the proglacial area from the valley sides or stream channel banks (e.g., Legg et al., 2014). We have chosen not to include these processes in the absence of data quantifying specific events, their highly intermittent nature, and difficulties in accurately modeling them (e.g., Hirschberg et al., 2022). Furthermore, many mass wasting events are above the glacier margin, such as those visible in Figure 2, and are disconnected from the proglacial area, depositing sediment directly onto the glacier.…”