Extracting topographic characteristics of landforms typical of Canadian agricultural landscapes for agri-environmental modeling. I. Methodology

Soil and topographic information are key inputs for many agri-environmental models and there are linkages between soil and topography at the Field scale. A major source of soil data is soil databases established based on field soil survey. Although both soil and topographic information are recorded in field soil surveys, the nominal nature of the topographic data has limited their use in agri-environmental models. in this study, we developed a methodology to extract various topographic derivatives and to classify the landscape into landform elements with distinctive topographic characteristics based on detailed analyses of fine resolution digital elevation models. Data obtained from these analyses were used to calculate a representative two-dimensional hillslope of five segments, each with a defined length and slope gradient. A set of modal hillslopes was developed to describe topographic variability. Additional topographic parameters, ratios and indices were calculated to reflect different aspects of topographic characteristics and also to build connections between different agri-environmental models. in particular, a topographic complexity index was developed as a quantitative measure of the degrees of divergence and convergence. This paper describes the methodology using one site as an example. Application of this methodology to other landforms in agricultural land of Canada is reported in a companion pape