Theoretical and numerical considerations of rivers in a tectonically inactive foreland
- Institut für Geo- und Umweltnaturwissenschaften, Albert-Ludwigs-Universität Freiburg, Albertstr. 23B, 79104 Freiburg, Germany
Abstract. Recent advances in the numerics of fluvial landform evolution models allow for large-scale simulations of erosion and sediment transportover time spans of several million years. This study aims at finding out fundamental properties of rivers in a tectonically inactive foreland of a mountain range by investigating a simple reference scenario. This scenario consists of a mountain range and a foreland in a quasi-steady state where the material eroded in the mountain range is routed through the foreland. In order to understand the properties of foreland rivers, a subdivision into two classes – carriers and redistributors – is introduced. Carriers originate in the mountain range and are thus responsible for the large-scale sediment transport to the ocean. In turn,redistributors are rivers whose entire catchment is located in the foreland. Using the concept of carriers and redistributors, it is shown that the drainage network in the foreland permanently reorganizes, so that a steady state in the strict sense is impossible. However, the longitudinal profiles of carriers are described well by a steady-state approximation. Their concavity index is considerably greater than that of rivers in the mountain range. Carriers are predominantly depositing sediment at high rates, while redistributors are eroding at much lower rates. Despite the low erosion rates, the sediment flux from redistributors into carriers is a major component of the overall sediment budget and finally the main driver of the highly dynamic behavior of the carriers.
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