Semi‐variograms for modelling the spatial pattern of landform and soil properties

Many geomorphic properties can be treated as spatially‐dependent random variables. Some are second‐order stationary, others appear to vary without bound. In these circumstances their variation is best described by the semi‐variogram. In most instances the semi‐variogram can be modelled by a simple mathematical function, which itself is bounded for a stationary variable and unbounded otherwise. The function must be conditional negative semi‐definite to be permissible. More complex variation can be represented by combining two or more permissible models. Sample semi‐variograms of several landform and soil properties illustrate the common types of semi‐variogram. Their form and parameters are interpreted in physical terms.