The Use Of Non-Invasive Geophysics To Assess Damage By Burrowing Animals To Earthen Levees Near Dayton, Ohio

Ground-penetrating radar (GPR), electrical resistivity, and streaming potential methods were<br>employed at southwestern Ohio, flood-control levee sites to test their effectiveness for determining the<br>amount of damage by animal burrows. Three 36-m long sections of earthen levee were tested, each<br>containing visible groundhog burrows. Overall levee dimensions and burrow locations dictated the<br>extent of the field surveys at each site. The GPR data were gathered with 80 and 300 MHz antennas.<br>2D electrical resistivity imaging was performed using a system with a dipole-dipole electrode<br>configuration. Electrical resistivity data were collected under dry conditions and while saline water was<br>pumped into selected visible burrows. The intent was to increase the resistivity contrast of the burrows.<br>Non-polarizing electrodes were used to gather streaming potential data. One core sample taken at each<br>site helped provide information on levee composition.<br>The GPR data provided the most reliable information on levee damage at the West Carrollton<br>site. Depth of penetration and resolution were good enough to map potential burrows to depths of about<br>2.4 meters and show a potentially interconnected network of burrows throughout the upper half of the<br>levee. GPR data for the other levees yielded results only to depths of around 1.5 meters and with lower<br>resolution compared to the West Carrollton data. Electrical resistivity imaging obtained adequate depth<br>penetration at all three sites, although resolution was too poor to effectively mark any burrows and<br>estimate any internal damage caused by the burrows. The streaming potential data lacked signal above<br>the noise range and thus provided little useful information. Based on the GPR data, significant<br>groundhog damage may exist in the West Carrollton levee. In addition, this levee may contain an<br>extensive, interconnected network of burrows. Not enough information is available for the Dayton and<br>Middletown sites to make similar conclusions.