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MacDuff, Alexander Marcel

University of British Columbia

Assessments of instream fish habitat in North America have been dominated by the Instream Flow Incremental Methodology (IFIM) used in conjunction with hydraulic modelling programs, such as the Physical Habitat Simulation (PHABSIM). While this methodology has repeatedly been described as invaluable for managing instream habitat, it has received significant criticism due to the intensive data demands and the logistical challenges that often limit data collection. In the past decade, several studies have demonstrated a potential solution in the implementation of topographic surveys conducted with the use of Unmanned-Aerial-Vehicles (UAVs) to produce digital elevation models (DEMs) derived from aerial images using Structure-from-Motion (SfM) photogrammetric software. There remain significant concerns that this approach will not be applicable to mountainous streams. Therefore, this study aimed to evaluate the effectiveness of UAV-SfM surveys for supplementing an IFIM assessment for Upper Mission Creek in the Southern Interior of British Columbia. Through an extensive field campaign, a total of 30 transects were surveyed multiple times with different methods, including the standard surveying convention using an engineer’s level and stadia rod, recording depths on a wading rod while measuring discharge, an RTK-DGPS survey, and UAV flights. During the subsequent quality control exercises, variance in the UAV-SfM sourced DEM was found to be comparable to traditional surveying methods. Unexpectedly, transects derived from the photogrammetric DEM produced more accurate and precise hydraulic models for predicting mean flow velocities. Habitat modelling demonstrated that reductions in the number of transects incorporated into the model, mimicking surveys with logistical constraints, led to highly variable and uncertain final estimates of wetted usable habitat. In contrast, supplementation of photogrammetric transects into the model was observed to compensate for reductions in the number of traditional transects in the model, thereby stabilizing habitat availability estimates. Although mountainous streams are more challenging to survey, supplementation of UAV-SfM sourced topographic data into the IFIM offers significant improvements in accuracy, precision and scale while expediting assessments of instream habitat.

Text

2022-06-02

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/81683

Earth and Environmental Sciences

University of British Columbia

UBCO

http://creativecommons.org/licenses/by-nc-nd/4.0/