The impact of geology on sediment dynamics. A modelling approach for the Northern Franconian Jura, Germany.

Landscape Evolution Models (LEMs) are powerful tools for simulating erosion and accumulation patterns over a landscape. To accurately capture the complexity of the system, several parameters are used to describe the flow of water on a surface and thereby calculate a change in landscape. However, due to the need for reasonable computing power, simplification is often necessary. The CAESAR-Lisflood LEM simplifies the transition from precipitation to runoff with a cell storage-based system, where water is retained in each cell and released at later iterations, simulating infiltration and forming the hydrograph. This reduced complexity works well for surface processes, but can lead to issues in catchments, where ground water flow and infiltration are unknown parameters, and an unknown proportion of sediment transport is connected to sub-surface processes.

Located in the Northern Franconian Jura, Germany, the Weismain River catchment (~125 km2) is a particularly challenging area to model the sediment dynamics, due to its karstic geology. The Weismain river and its tributaries are deeply incised into a limestone plateau forming small, well-defined valleys opening to wider floodplains in the lower parts of the catchment, where sandstone is dominant. To gain a better understanding of the sediment dynamics and the evolution of this catchment, the impact of the karstic environment needs to be evaluated. With CAESAR-Lisflood we are looking at the spatial distribution of alluvial sediment from different model inputs and how differences in discharge calculations affect model results. With this model setup we can gain insight into the sediment dynamics of the catchment and increase confidence in future results.