Locating drainage tiles at a wetland restoration site within the Oak Openings region of Ohio, United States using UAV and land based geophysical techniques

Drainage tiles were used to drain wetlands in the midwestern United States to convert them into farmlands. With decades of farm operations, utility maps showing tiles’ locations are now mostly innaccurate or simply do not exist. However, knowledge of the location of tile networks is needed to effectively restore these farmlands to their original wetlands conditions. With many fields spanning several hectares, efficiently locating drainage tiles at large farmfields can be problematic. Drainage tiles create variations in soil physical properties including moisture content, surface temperature and dielectric permeativity within and around the pipes which can be sensed by geophysical methods. Our study assesses the application of electromagnetic radiation via visible and thermal infrared imaging using an unmanned aerial vehicle and ground penetrating radar (GPR) to locate drainage tiles at large farmfield scale. The study was conducted at the Sandhill Crane wetland, a 1.1 km2 old agricultural field located in Swanton, Ohio. A UAV equiped with visible and thermal infrared cameras acquired imagery on a regular grid and about 100 GPR lines were measured using a 250 MHz radar system. Both visible and thermal infrared images identified the drainage tiles and their orientations. GPR profiles reveal the drainage tiles mostly in a parallel East-West direction. By using a UTV to pull the GPR system, we efficiently collected data along long profiles covering the entire site. The delineated tile network will improve management of the anthropogenically altered hydrology at the site as it is being restored into its original wetland conditions.