An Earth-Surface Landscape Evolution Model with a Biological Life Signature

In geomorphology, the traditional continuity equation model has provided a useful framework allowing examination of important questions about landscape evolution through time. However, it has advantages and disadvantages. Key advantages include the ability to quantitatively reproduce observed landscape features and mathematical simplicity. This approach has produced some significant findings that have led to a better understanding of the factors driving landscape evolution. The disadvantages are nonetheless significant, particularly the use of a single, empirically-determined parameter for describing the many competing factors that direct the evolution of landscape shape changes. The lack of direct inclusion of theoretical terms and formulations that can realistically account for on- and near-surface layer soil transport processes is a major limitation. We have developed a revised theoretical approach to the formulation of landscape evolution models. It commences with a new derivation, from first principles, of the soil surface continuity equation using a three-dimensional, thin, surface-plane volume element as its basis. The resulting solutions retain the key forecasting feature of the original , namely the prediction of landscape surface elevation as a function of time and position. The model can be formulated to include a wide range of surface and near-surface processes, such as soil bioturbation, gravity-driven down-slope soil creep, surface mound erosion, and source-soil erosion. Hillslope landscape profiles displaying an up-slope convex shape and a down-slope concave shape are inherent in the newly derived continuity equation. Numerical landscape shape evolution results for idealized hillside initial conditions are readily obtained and allow for comparison of the relative magnitude and significance of several soil transport processes.