USING GROUND PENETRATING RADAR (GPR) TO IDENTIFY TURTLE NESTS

摘要

Many turtle species are considered species at risk in Ontario and Canada. Legislation and policy protects individuals, habitats and nests. Turtles nest in areas with sand and gravel and other loose substrates, with suitable sunlight and good drainage, including roadsides, and other disturbed areas. The presence of nests may pose constraints to construction and operation of roads and other engineering projects in Ontario. Throughout Ontario, turtles have been observed to nest in the embankments and gravel shoulders of roadways located near wetlands. The ease of access to these nests enables the use of non-destructive technologies, such as Ground Penetrating Radar (GPR), that are capable of locating these nests. During a GPR survey, the radar scans cross subsurface features such as pipes, walls, rocks or void spaces which generate hyperbolic reflections. The turtle nests are essentially void spaces in the gravel shoulder and can be detected using GPR because of the change in the reflected radar signal velocity. Once the data has been collected, it is imported into a data reduction software which digitizes the radar reflections and can also be linked to GPS coordinates. The depth and location of the nests can then be exported into an Excel spreadsheet. In this paper, we will draw on recent project experiences in Ontario to: describe the process for identifying suitable nesting habitat and finding nests; and regulatory approval requirements, including avoidance, mitigation, and compensation requirements. The paper also provides suggestions for improvements in ground-truthing the collected data in order to refine data processing and identification techniques.