This week, Marco Van De Wiel, Visiting Professor from Western Ontario University delivered a presentation on "Predicting Geomorphic changes". Since catchment sediment dynamics respond to external forces acting on the catchment: tectonics, climate and human activities, it is therefore often assumed that any change in the sediment dynamics directly reflects change in one or more of these external forces. However, the relation between forcing signal and response signal can be obscured because catchments also impose their own autogenic signal on the sediment dynamics. Moreover, this autogenic signal is highly non-linear because of thresholds in geomorphological processes, interactions and feedbacks between different processes, and response time-lags. This non-linear signal, imposed by the catchment itself, may prevent relating sediment dynamics to forcing signals, i.e. it may prevent linking cause and effect.His presentation addressed the weasel-word “may” from the previous sentence. Using numerical landscape evolution models as a virtual laboratory, the limits on the predictability and unpredictability catchment sediment dynamics are investigated. Is it indeed not possible to link cause to effect in landscape sediment dynamics? Or is it possible to gain insights about past external forces and to predict response to future ones, even in the presence of non-linear autogenic disturbances arising from the landscape itself?
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