The Use of Natural Stream Characteristics for Stream Rehabilitation Works Below the Manitoba Escarpment

Abstract

Drainage improvement of watersheds draining from the Manitoba escarpment has been based on channel designs which result in nearly straight canals with uniform gradients and trapezoidal cross-sections. These conditions are often associated with environmental degradation, such as loss of fish spawning and rearing habitat, increased erosion and siltation, and changes in water conveyance patterns that can cause property damage. In mobile bed streams, the geometry of the "natural" stream channel in profile and in cross section is determined by the geology of the basin, the extent of the tributary drainage area, and the position of a stream reach in the hierarchical order of the drainage network. Regional stream channel characteristics can be determined from channel surveys in sample reaches that are selected throughout the basin. Selected aspects of the "natural" stream geometry can then be mimicked in rehabilitation schemes that enhance or create physical stream characteristics in the uniform drainage canals that are significant biologically and hydraulically. Experimental rehabilitation and enhancement works have been constructed in Wilson Creek and Mink River. The works have re-stabilized the channels and created new pool and riffle habitats for fish spawning and rearing.