Impact of a hydropeaking dam on the Kananaskis River : changes in geomorphology, riparian ecology, and physical habitat

• Main Author: Buehler, Holly
• Language: English
• Published: University of British Columbia 2013
• Online Access: http://hdl.handle.net/2429/43905

The Pocaterra dam on the Kananaskis River provides a unique opportunity to assess dam induced changes in channel morphology because it has caused reduction in the magnitude of high flows and creation of daily peaking flows with no associated alteration in sediment supply. We assessed reach scale morphological change of the Kananaskis as a result of the hydropeaking flow regime considering change in geometry, planform, vegetation, and pool characteristics and distribution. Pre and post-dam channel conditions were assessed through historical photos, field measurements, remote sensing techniques and modeling. The channel just downstream of the dam widened, the middle six sites show no statistical change, and the most downstream three sites showed statistically significant narrowing. Further changes included a shift towards fewer active channels, abandonment of back channels, increase in density of riparian vegetation, and low diversity of successional stages within the riparian forests. A rational regime model reasonably predicted width adjustment and shift in number of active channels. We also found depth distributions to differ from statistical distributions in the most upstream sites with a higher proportion of low depths while the most downstream site matched the statistical distributions. Pool characteristics were associated with local attributes with large pools formed near large wood and back channels and numerous smaller free forming pools. The hydropeaking signal appears to drive channel change in the upper reaches where the models did not correspond to observed channel characteristics while the reduction in peak flows appears to drive channel morphology in the more downstream reaches. The interactions of the hydropeaking flows with winter ice dynamics also appear to control channel change in this system and contribute to the unique morphology. Channel change is likely associated with decrease in the quality and quantity of suitable fish habitat and thus may have driven declines in fish diversity along this river. Despite the complexity of this system, these modeling and remote sensing methods simply and accurately characterize changes on the Kananaskis and thus provide a useful and rapid method to assess morphological change in a disturbed system.