RIPARIAN MONITORING USING 2-CM GSD AERIAL PHOTOGRAPHY

Authors: Booth, D; Cox, Samuel; SIMONDS, GREG - OPEN RANGE CONSULTING

Submitted to: Ecological Indicators
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/20/2006
Publication Date: 7/20/2006
Citation: Booth, D.T., Cox, S.E., Simonds, G. 2006. Riparian monitoring using 2-cm gsd aerial photography. Journal of Ecological Indicators 7:636-648.

Interpretive Summary: Rising manpower costs and time-consuming travel and methods limit agency ecological assessments of riparian (freshwater streams) health and reduce the effectiveness of resource management. We tested low-altitude, high-resolution, intermittent aerial digital photography for relatively inexpensive, high-intensity sampling in a watershed inhabited by the Lahonton Cutthroat trout, a species listed as threatened under provisions of the US Endangered Species Act. Riparian proper functioning condition (PFC) was assessed from the photography by a USDI, Bureau of Land Management team using an average 4 staff hours per stream compared to an estimated 36 staff hours per stream needed for ground PFC assessments. The 2 methods yielded comparable results. We conclude that riparian-condition assessments from the aerial photography allowed increased sample intensity at less than half the cost of conventional ground-based methods.

Technical Abstract: Riparian monitoring is a key aspect of sustainable resource management and is mandated by US federal law for federal land-management agencies. However, it is an endeavor hampered by rising manpower costs and time-consuming travel and methods. These limitations tend to reduce sampling intensity per reach of stream and limit monitoring to the larger waterways of management units—limitations that reduce the accuracy of inferences derived from resulting data with consequential reductions in the effectiveness of landscape-level resource management. We tested the utility of low-altitude, high-resolution, intermittent aerial digital imagery for relatively inexpensive, high-intensity sampling in a watershed inhabited by the Lahonton Cutthroat trout, a species listed as threatened under provisions of the US Endangered Species Act. Measurements gleaned from the aerial imagery included late-summer open water width, number and location of late-summer dry channels, widths of riparian areas and willow coverage. All measurements were geocoded to allow spatial data display. Riparian proper functioning condition (PFC) was assessed from the imagery by a USDI, Bureau of Land Management team. These assessments were compared to similar on-the-ground assessments made during the preceding year. PFC assessments from aerial photography were made using an average 4 staff hours per stream compared to an estimated 36 staff hours per stream for ground PFC assessments. The 2 assessment methods yielded roughly comparable results. We conclude that riparian-condition assessments from 2-cm GSD digital aerial imagery allowed increased sample intensity (and thus increased inference accuracy) and that it did so in our study at a cost less than half that of conventional ground-based methods. We recommend the acquisition and analysis of 2-cm GSD digital aerial imagery be further trialed for its utility and cost efficiency in riparian ecological monitoring of riparian systems.