Quantifying variability in stream channel morphology

Glyceria maxima (Reed sweet-grass), an emergent aquatic grass native to Eurasia, has naturalised in North America, New Zealand and southern Australia. Introduced as a ponded pasture species, it threatens native biodiversity and ecosystem processes in freshwater wetlands and waterways. We compared paired sections, either invaded or not invaded by G. maxima, of three upland streams in Gippsland, Victoria, Australia to infer its impacts on macroinvertebrate abundance, morphospecies density, and morphospecies and functional feeding group (FFG) composition. Its potential effects in altering sedimentation were explored by comparing stream channel morphology in paired stream sections at one site. Invasion by G. maxima appears to drive changes in macroinvertebrate morphospecies composition and FFG composition, reducing a diverse array of macroinvertebrates to a more uniform fauna. The estimated volume of plant/sediment matrix in a 50 m invaded stream section was around 1100 m3, nearly 15-fold greater than in an adjacent uninvaded stream section. Glyceria maxima is an autogenic ecosystem engineer, with the ability to convert sections of fast-flowing aerobic streams into partially anaerobic swamps. By generating a root-mat swamp with a high capacity to process nutrients, G. maxima may facilitate its own growth and spread, as well as that of secondary invaders.

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The impacts of ski slope development on stream channel morphology in the White River National Forest, Colorado, USA

Geomorphology ◽

10.1016/j.geomorph.2008.07.003 ◽

2009 ◽

Vol 103 (3) ◽

pp. 375-388 ◽

Cited By ~ 18

Author(s):

Gabrielle C.L. David ◽

Brian P. Bledsoe ◽

David M. Merritt ◽

Ellen Wohl

Keyword(s):

Channel Morphology ◽

National Forest ◽

Stream Channel ◽

White River

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Implications of legacy watershed disturbances for channel structure and salmon habitat availability under different low-flow levels: an analysis of 45 years of discharge–habitat relationships at Carnation Creek, British Columbia

Canadian Journal of Fisheries and Aquatic Sciences ◽

10.1139/cjfas-2020-0120 ◽

2020 ◽

Vol 77 (11) ◽

pp. 1780-1793

Author(s):

David A. Reid ◽

Robin Pike ◽

Stephen Bird ◽

Peter Tschaplinski ◽

David Wilford

Keyword(s):

British Columbia ◽

Coho Salmon ◽

Aquatic Organisms ◽

Channel Morphology ◽

Channel Structure ◽

Low Flow ◽

Habitat Availability ◽

Stream Channel ◽

Ecological Requirements ◽

Trade Offs

In streams where water availability is limited, conservative flow ranges are often adopted by water managers to ensure that streamflow is available to meet the ecological requirements of aquatic organisms. However, a variety of natural and anthropogenic disturbances can influence stream channel morphology and in-stream wood characteristics through time, potentially altering the availability of habitat at a given flow level. Using a 2D hydrodynamic modelling approach incorporating 45 years of detailed channel morphology data from Carnation Creek, British Columbia, this paper examines relationships between legacy (forestry-driven) watershed disturbance, changes to channel morphology, and habitat availability for juvenile coho salmon (Oncorhynchus kisutch) under nine flow levels. Results indicate that substantial variability in the abundance of salmonid habitat is present through time, even when modelled flow levels are held constant. Additionally, trade-offs were observed between availability of habitat types as discharge increased. Finally, modelling results indicate that habitat availability is reduced following historical harvesting. These findings suggest that legacy watershed disturbances affecting stream channel form and function are worth considering when allocating streamflow.

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