Catchment-scale, high-resolution, hydraulic models and habitat maps – a salmonid's perspective

Abstract

The advent of remotely-sensed high-resolution imagery has led to the development of methods to map river bathymetry. In this study, we utilized high-resolution imagery to map river depth and quantify hydraulic habitats at the catchment scale (>1000 km²) during low flows. Using 0.3-m airborne multi-spectral imagery (resampled to 0.5 m), we mapped contiguous river depth (124 km) within a well-established Atlantic Salmon (Salmo salar) and Brook Trout (Salvelinus fontinalis) river – The Little Southwest Miramichi, New Brunswick. We built image-derived depth maps with and without field data calibration. The model without field calibration data (flow resistance equation‐based imaging of river depths) accurately described river depths (R² = 72.7; RMSE = 0.167 m; n = 762); however, it overestimated shallow depths. The field-calibrated model removed shallow depth errors (R² = 76.4; RMSE = 0.155 m; n = 762). We mapped velocity using a relationship between river geometry and discharge, and coalesced the field-calibrated depth and velocity maps to create Froude and Reynolds number maps. Finally, we performed an unsupervised classification model to delineate the hydraulically relevant habitat units for salmonids. This approach provides an unprecedented view of catchment-scale hydraulic habitats that will advance both hydrological process research and river resources management.

Keywords:

• Aerial imagery
• Atlantic Salmon
• Brook Trout
• catchment-scale
• FREEBIRD
• habitat
• remotely-sensed bathymetry

Acknowledgements

First, the authors would like to thank Lord Pisces. We would like to thank two anonymous reviewers for their constructive comments. In particular, we would like to thank Prof. G. Pasternack for his comments which greatly strengthened this work. Geospatial information was provided through GeoNB, New Brunswick Department of Energy Resources Development. A. Culberson, D. Connor, J. Leavitt, M. Ndong and M. Warner are thanked for help in collecting field data. The authors would also like to thank B. Newbury and R.A. Cunjak for their guidance and E.M. Corey for help with initial drafts.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

The authors wish to thank NSERC (RGPIN-2018-06015), Collaboration for Atlantic Salmon Tomorrow (CAST), J.D. Irving, Limited, Department of Fisheries and Oceans Canada, Atlantic Salmon Conservation Fund, New Brunswick’s Environmental Trust Fund and New Brunswick Wildlife Trust Fund for funding support. A.M.O’S would like to thank the Miramichi Salmon Association (MSA), Forestry and Environmental Management – UNB, Bud and Peggy Bird and Mr. and Mrs. Art Van Slyke for generous scholarships.