GEOPHYSICAL AND ARCHAEOLOGICAL INVENTORY OF A DROWNED RIVER VALLEY, COLONEL BY LAKE, ONTARIO, CANADA

Colonel By Lake was created when the lower Cataraqui River was flooded to build the Rideau Canal between 1826 and 1831. The flooding raised water levels by more than 6 m, submerging potential historical and archaeological sites. Historical maps show a number of pre-canal era structures on the banks of the Cataraqui River. In order to gain a better understanding of the pre-canal landscape and its archaeological potential, a systematic geophysical survey and sediment coring program was conducted in Colonel By Lake. A Digital Bathymetric Model (DBM) of the lake bottom was created using 200 kHz single-beam bathymetry and side scan imagery. The pre-canal environment and historical water-level changes were reconstructed using sediment core analysis, including grain size, magnetic susceptibility and thecamoebian assemblages.

The DBM and side scan mosaic clearly define the former Cataraqui River channel, floodplain topography and numerous stump fields defining forest areas cleared for canal construction. By comparing the DBM and side-scan mosaic with canal era drawings (ca.1828), several archaeological features were identified, including two possible canal-era homesteads. These locations are associated with distinct debris scatters in the side scan sonar and await diver investigation. The onset of European settlement and water level fluctuations are also recorded by down-core changes in thecamoebian abundance, grain-size and magnetic properties. These results provide a valuable insight into the pre-canal environment of the Cataraqui River and can be used to guide further archaeological investigation.