INTERACTIONS BETWEEN TECTONICS, SEDIMENT LOAD, AND BEDROCK EROSION: A NUMERICAL STUDY OF TRANSIENT LANDSCAPES

Equilibrium channel network form appears to be fairly insensitive to the details of the dominant fluvial erosion process. However, when the landscape experiences a change in forcing, such as an increase in uplift rate, feedbacks included in some erosion rules can complicate the transient network response. We investigate the fluvial response to an increase in uplift rate using the CHILD numerical landscape evolution model. We concentrate on differences in channel profile evolution using a number of erosion equations which incorporate the incoming sediment flux as an important agent in eroding bedrock. Using a sediment-flux rule, the transient response varies from simple knickpoint propagation as predicted by the stream power erosion rule. Different parts of the network feel the change in uplift rate at different times, resulting in complex changes in both sediment load and erosion rates. The transient predictions depend on the applied erosion law, illustrating that the details of erosion processes may be important for some applications.