Habitat Suitability and Hydraulic Signatures of Geomorphological Units in a Restored Channel

English Abstract:

Channel reaches consist of a series of geomorphological units. In many ‘restored’ channels these geomorphological units are a sequence of riffles and pools designed to mitigate flow velocity and provide suitable aquatic habitat. Geomorphological units such as pools and riffles should display morphological, sedimentological and hydraulic signatures. If we can use a hydraulic signature to differentiate between these units we can evaluate the proportion of a given geomorphological unit within a reach. Similarly, a given fish species will require specific hydraulic conditions for different activities. We can use the hydraulic signatures to evaluate suitability of reaches and geomorphological units for target fish species. Therefore, we should be able to assess ‘restored’ and natural channels in relation to the proportion of different geomorphological units and in the area within the channel that is suitable for a given target fish species. 650 m of creek and valley was realigned in Brampton, Ontario to facilitate development and was an opportunity to restore a degraded system. The channel studied consisted of riffle-pool sequence within a larger channel realignment and floodplain design. Velocity, water depth and substrate were measured at numerous cross-sections through a variety of flow conditions between May and September 2013. This study uses these measurements to evaluate the hydraulic signature of each geomorphological unit and the habitat suitability based on velocity and depth for a range of target species. The assessment illustrated that the approach provides quantitative methodology to examine geomorphological units within natural channels. The approach also provides a quantitative method to examine habitat suitability of target species through variable flow conditions.