Catenas and Soils

Randall J. Schaetzl

Soil development is intimately tied to the slopes on which soils form. Soils across slopes are connected, process-wise, like links in a chain. This analogy has led to the concept of a catena – a term for a series of soils on a slope. This chapter explores the reasons for soil variation on catenas, focusing on (1) debris and moisture flux along the slope and (2) depth to the water table. Fluxes of sediment, commonly facilitated by water, vary predictably as a function of position on the slope, leading to soils that may be thinner or thicker than expected on steep slope segments where runoff is accentuated. Conversely, soils on lower, flatter slope segments may be overthickened from many years of slow but episodic sediment accumulations from upslope; when sediment accumulations are particularly fast or large, soils here can become buried. Soil texture and infiltration capacities dramatically impact these processes; on slopes composed of coarser, more permeable materials, catenary position is less important because there is less runoff, and thus, even on the steepest slope segments, much of the water infiltrates vertically. Water tables, commonly deepest on the steepest slope segments, vary predictably as a function of position on the slope. High water tables can dramatically affect internal soil processes, as well as weathering and related phenomena.