Modelling centennial sediment waves in an eroding landscape – catchment complexity

Abstract

Sediment flux dynamics in fluvial systems have often been related to changes in external drivers of topography, climate or land cover. It is well known that these dynamics are non‐linear. Recently, model simulations of fluvial activity and landscape evolution have suggested that self‐organization in landscapes can also cause internal complexity in the sedimentary record. In this contribution one particular case of self‐organization is explored in the Sabinal field study area, Spain, where several dynamic zones of sedimentation and incision are observed along the current river bed. Whether these zones can be caused by internal complexity was tested with landscape evolution model (LEM) LAPSUS (Landscape Process Modelling at Multi‐dimensions and Scales). During various 500 year simulations, zones of sedimentation appear to move upstream and downstream in eroding river channels (‘waves’). These waves are visualized and characterized for a range of model settings under constant external forcing, and the self‐organizing process behind their occurrence is analysed. Results indicate that this process is not necessarily related to simplifications in the model and is more generic than the process of bed‐armouring that has recently been recognized as a cause for complexity in LEM simulations. We conclude that autogenic sediment waves are the result of the spatial propagation in time of feedbacks in local transport limited (deposition) and detachment limited (erosion) conditions. Copyright © 2014 John Wiley & Sons, Ltd.

Modelling long‐term (300 ka) upland catchment response to multiple lava damming events

“…The average and variation of net erosion for the parameter settings that were not selected after calibration show similar trends to those of the optimal parameter set depicted in Figure 6. Generally, P has much less influence on total erosion values than K. Sensitivity plots of K and P are described in Baartman et al (2012a) and Schoorl et al (2014) and indicate that sedimentability factor P influences resedimentation and floodplain dynamics, while hardly influencing total erosion . Likewise, upstream migration of net erosion differences (Figures 9 and 10) occurs in all parameter settings, but the exact pattern is dependent on parameter settings.…”

Complexity and non‐linearity in earth surface processes – concepts, methods and applications

“…Reason for non-linearity Discussants in this issue Thresholds Outputs will not be proportional to inputs above and below a threshold Phillips, 2014 Storage effects The addition or removal of stored components will affect input-output relationships Croke et al, 2015;Schoorl et al, 2014 Saturation and depletion…”

“…The effect of an increase in input varies with respect to some optimum Croke et al, 2015;Schoorl et al, 2014 Self-reinforcing, positive feedback…”

“…He demonstrated that complex non-linear dynamics are not an artefact of models, equations and simplified experiments, but can be recognized in many geomorphic systems and have profound implications for prediction, explanation and application (Table I). Phillips' (2003) template has successfully been applied in areas like weathering and rock slope erosion (Viles, 2013;Krautblatter and Moore, 2014), sediment connectivity and cascading (Fryirs, 2013;Schoorl et al, 2014) and soil formation and degradation (Montagne et al, 2013). This appraisal of complexity highlights that complex systems can be rather simple in structure and functioning, and are not Temme et al, 2008).…”

Applying Pattern Oriented Sampling in current fieldwork practice to enable more effective model evaluation in fluvial landscape evolution research

“…Wainwright and Mulligan 2005). Schoorl et al 2014). This approach of 'insightful simplification' or 'reduced complexity modelling', does seek to explain what has happened in a specific place, as in the traditional heuristic model, but also to more broadly understand the known global driving factors within fluvial landscapes (Veldkamp and Tebbens 2001), and to create generalizable statements about the development of large-scale geomorphological features.…”