Development of a method for estimating the likelihood of finger flow and lateral flow in Canadian agricultural landscapes

Finger flow (FF) and lateral flow (LF) are key pathways connecting sub-surface contaminant transport from soils to water bodies. The objectives of this study were to develop methodologies for predicting the likelihood of FF and LF occurrence in agricultural soils across Canada at the landscape scale, and to use them as input parameters for risk indicators of water contamination. Both FF and LF consider the volume of infiltrating water. FF considers soil texture, layering, and content in coarse fragments, while LF considers restricting layers, trees, slope, and soil depth. High risk of LF in British Columbia is associated to shallow soils over compacted till in steep areas with higher density of trees. South of the St. Lawrence River shows the largest region at high risk of LF due to much water infiltration, compacted till and shallow soils. Eastern provinces have higher risk of FF, due to layered sandy soils and abundant precipitations. LF and FF distribution maps can also be used as simple tools for supporting the identification of land surfaces where management should consider subsurface contaminant transport processes and to warn potential water pollution from inland agricultural contaminants.