Riverbank instability and development control in Saskatoon

Abstract

Slope instability along the banks of the South Saskatchewan River Valley has been a continual problem for Saskatoon's City Engineering Department since 1913. It has affected building and bridge foundations, damaged municipal roads and services, and interfered with park and playground development. Where the glacial till in the banks is overlain by lacustrine clays, silts, and sands, the lower portion of the slip surface invariably follows the stratigraphic contact between the till and the overlying materials. Piping of intertill stratified drift is the major cause of slope instability where the till is exposed at the surface. Groundwater from the natural infiltration and from lawn watering greatly affects the slope stability. Remedial techniques have consisted primarily of subsurface drainage systems.Increased pressure for development along the riverbank has led to the recent establishment of the Meewasin Valley Authority which has complete control of development within and along the river valley. Opposition to the Authority's establishment has been strong. Its success in controlling development near unstable slopes will only be proven with time.