Landscape Evolution Model

LEMming tracks regolith and sediment fluxes, including bedrock erosion by
streams and rockfall from steep slopes. Initial landscape form and stratigraphic
structure are prescribed. Model grid cells with slope angles above a threshold, and
which correspond to the appropriate rock type, are designated as candidate sources
for rockfall. Rockfall erosion of the cliffband is simulated by instantaneously
reducing the height of a randomly chosen grid cell that is susceptible to failure to
that of its nearest downhill neighbor among the eight cells bordering it. This
volume of rockfall debris is distributed across the landscape below this cell
according to rules that weight the likelihood of each downhill cell to retain
rockfall debris. The weighting is based on local conditions such as slope angle,
topographic curvature, and distance and direction from the rockfall source. Rockfall
debris and the bedrock types are each differentiated by the rate at which they
weather to regolith and by their fluvial erodibility. Regolith is moved according to
transport rules mimicking hillslope processes (dependent on local slope angle), and
bedload and suspended load transport (based on stream power). Regolith and sediment
transport are limited by available material; bedrock incision occurs (also based on
stream power) where bare rock is exposed.