Exploring the influence of sediment cover on bedrock channel slope and width responses to climate and tectonic perturbations

Sediment plays a key role in modulating bedrock channel response to tectonics and climate. By armoring the channel bed, sediment cover can dampen the topographic expressions of these perturbations in the channel profile. A variety of models have been developed to capture the influence of sediment cover on bedrock channel evolution, including the Stream Power with Alluvium Conservation and Entrainment (SPACE) model (Shobe et al., 2017), which builds on the standard stream power model by conserving the mass eroded from the channel bed and allowing it to be transported downstream or deposited in an alluvial layer. The model assumes that channel width scales with discharge rather than allowing for a dynamically evolving channel width. However, sediment may play an important role in the channel’s evolution by abrading the sidewalls and widening the channel in order to accommodate increased sediment flux, which may in turn reduce vertical incision rates. Here we present a modified version of the SPACE model that explicitly calculates channel width in order to test how sediment cover influences channel widening and steepening in response to climate and tectonic perturbations in 2D and at the landscape scale. Like the original SPACE model, our model is implemented using the Landlab toolkit, a python library for modeling earth surface processes. We use our model to explore how feedbacks between sediment production, sediment cover, and channel widening or narrowing may influence patterns and rates of incision during transient responses to changes in uplift and climate. We specifically test how sensitive vertical and lateral incision rates are to pulses of uplift under varying sediment regimes. We also explore the influence of climate by varying precipitation rate. Our model offers an efficient method for modeling dynamic channel width and sediment dynamics that can be coupled with existing Landlab components to address a wide range of geomorphic problems in two dimensions.