TTLEM3D - Simulating erosion of uplifting landscapes with layered rocks

Many landscapes are characterized by marked differences in rock erodibility. Cuesta and escarpment landscapes, for example, develop their characteristic form due to contrasts of physical and chemical properties of individual rock layers in lithostratigraphic sequences. Over long time scales, 3D-variable rock properties and resistances to erosion imply that landscapes do not attain a steady state and exhibit autogenically migrating drainage divides. One may thus argue that landscapes with layered rocks are much more dynamic than landscapes characterized by homogenous rocks. Here, we present the development and implementation of TTLEM3D, an enhancement to TTLEM based on TopoToolbox which relies on the detachment-limited stream-power incision model and the eikonal equation to simulate eroding landscapes characterized by spatial variations in rock erodibility and threshold slopes. We show that 3D variations in rock properties strongly affect how landscapes respond to changes in uplift rates and uplift patterns. While simulated elevations compare well with the topography of actual landscapes, we note several discrepancies that reflect theoretical shortcomings of geomorphic transport laws and their application in landscapes with layered rocks.