Slide 4 of 66
Notes:
This is an example of a steady-state landscape simulated by Howard’s (1994, op. cit.) simulation model. The landscape is simulated on a 100x100 matrix. High areas are reddish, low areas are bluish. Lighting is from the left.
Lateral boundaries are periodic in that slopes are continuous between the left and right boundaries, and material (water, sediment, mass wasting flux) exiting to the left re-enters on the right boundary. The top boundary is a no-flux boundary, so that it is normally a drainage divide. The bottom boundary is forced to be level and is lowered at a constant rate (the base level control).
At each grid cell the erosional processes include both linear creep diffusion and fluvial erosion proportional to the shear stress exerted by the flow. Initial conditions are generally a low-relief fractally random landscape with no imposed channels or divides. However, as base level is lowered providing gravitational energy for erosion, a landscape spontaneously develops in which the processes are areally segregated to a large degree into convex divides and sideslopes on on hand, and a dendritic channel network on the other hand. The divides are primarily eroded by creep, where low contributing drainage area make this process most efficient. Along the channels fluvial erosion dominates, due to large contributing drainage areas. Thus erosion with a combination of diffusive mass wasting and concentrative fluvial erosion implies that a normal fluvial landscape with a dendritic drainage pattern will emerge. The fluvial channels are assumed to be bedrock rather than alluvial.
