Open Session - SWISS GEOSCIENCE MEETINGs

2). Sediment transfer starts from the hillslopes (1), where physical weathering followed by gravitational processes are predominant.
The time of residence of sediments is very variable depending on the topographic setting and the intensity of processes
and could be related to a complex stochastic function (e.g. Hegg, 1997). Sediments may have a second repository when
they reach the active gully (2). Here, the time of residence depends on water runoff. It could be explained by less complex
functions, because transfer is done only through two processes – debris flow or bed load transport. These two phenomena
transfer sediments very actively and therefore do not store them for long (3). When they reach the fan (4) sediments transported
by active geomorphic phenomena could either be stored (5) or transit directly to the effluent (6). Following these
previous observations debris transfer are then replaced into the global erosion system. This could help to highlight with
which part of the system volume assessment model are playing. The global scheme can be summarised by a tank cascade as
depicted in Figure 2. The size of the tank is referred to the potential residence time of sediments (the difference in size on
the graph must be seen in a logarithm perspective).
Figure 1. Place of debris flow and bed load transport into the erosive system.
Figure 2. Tank cascade for sediment transfer and landscape elements where the different formula are applied.
REFERENCES
Theler, D. & Reynard, E. in press: Assessing sediment transfer dynamics from geomorphological maps: Bruchi torrential
system, Swiss Alps. Journal of Maps 2008.
Hegg, C., 1997. Zur Erfassung und Modellierung von gefährlichen Prozessen in steilen Wildbacheinzugsgebieten, G 52.
Geographisches Institut der Universität Bern, Bern.
Zimmermann, M., Mani, P. & Romang, H. 1997: Magnitude-frequency aspects of alpine debris flows. Eclogae geol. Helv., 90,
415–420.
20
Symposium 6: Apply! Snow, ice and Permafrost Science + Geomorphology