Influence of Surficial Alluvium on Habitat Utilization by Fish in a Semi-Alluvial Clay-Bed Creek

English Abstract:

Morphodynamic processes play an essential role for the ecological integrity of river habitats. Fluvial dynamic processes and morphological changes in rivers can directly impact aquatic organisms; at different stages of their life-cycle they can be sensitive to sediment characteristics. Change in channel morphology can also influence habitat availability. Over the past few decades, efforts have been made to predict the influence of morphological change on aquatic habitat. Nevertheless, there are still large uncertainties in the degree to which erosion/deposition processes can impact the available habitat. The primary aim of the present study is to investigate relations between channel erodibility and habitat availability in a meandering semi-alluvial creek. The main focus of this paper is to examine whether channel erosion can affect the fish community, as the most commonly used indicator species, in two different meandering clay-bed reaches of Watts Creek in the City of Ottawa, Canada. These reaches have similar discharge and bed substrate, which consists of consolidated clay overlain discontinuously with surficial alluvium. However, one of these reaches has been destabilized due to meander confinement. In order to associate fish abundances with particular habitat features in the reach, habitat utilization by resident fish populations was evaluated in each reach. Finally, using a 3D morphodynamic model developed for the reach, along with the observed fish abundances, the effect of the channel instability and surficial alluvial material on habitat utilization is discussed.