"Drifters" document Islesboro's tidal currents

GIS-produced map of the Islesboro Drift Study Kathleen Reardon

Islesboro high school students performed a "drift study" through Gilkey Harbor to study how tidal currents run through the islands west of the southern part of Islesboro. This study was based on the Cobscook Bay Resource Center and Shead High School (Eastport) collaboration for the Cobscook Drift Study.

After consulting some local fishermen and tide charts, the class, taught by Dory Kistner with the help of Island Institute Fellow Kathleen Reardon, determined it would investigate the tidal currents through Gilkey Harbor on an ebb tide (starting at high tide at Grindle Point, near the ferry dock).

Using a description of the design from the Cobscook Bay study and funded by the Island Institute, the Islesboro students built four drifters out of five-foot lengths of PVC pipe, gravel (for ballast), and posts with flags (for visibility).

At 9 a.m. on June 7, the drifters were deployed in the channel just west of the ferry dock at Grindle Point from a local lobster boat, SATISFACTION, captained by Josh Conover (with first mate, Lily, a golden retriever). Over the next six hours the students, with the help of Reardon and Conover, followed the four drifters and took readings every half-hour using a mapping GPS (Global Positioning System).

Some of the drifters beached themselves, so they were moved either out farther in the channel or to different locations (creating more than four drift tracks).

Back in the classroom, one of the students processed the data and exported the tracks of each of the drifters to Arc View, a GIS program, to create a map of the tidal currents.

This is the first project of this kind on Islesboro, and there are plans to replicate the study. Kistner will be teaching a physics class next year and hopes to use this spring's field work to determine where the drifters should be deployed. She hopes to gain an even better understanding of how the tidal currents movearound the islands west of southern Islesboro.