The Alberta Geological Survey (AGS) has updated its digital data (shapefile) of bedrock valley thalwegs to include the addition of more than 1350 new valley thalwegs. The revised shapefile includes fourteen fields of descriptive information, including references to the sources of data collected over more than 50 years at AGS. These attributes enable the user to query thalwegs based on age, nature of valley exposure, genesis of valley, the catchment stream/valley, and the depositional basin.
Unlike previous maps and digital datasets, thalwegs captured in this shapefile are not just those of buried bedrock valleys, or valleys of preglacial age, but include all valleys incised into bedrock including valleys of present-day rivers that have downcut into bedrock. In this last case, incision to bedrock was verified by locating exposures of bedrock from high-quality Google Earth imagery.
AGS has attempted to preserve the traces of historical work, altering or omitting thalwegs only where new information shows either the presence, or the position, to be invalid. Very few edits were made of this nature.
Andriashek, L. comp. (2018): Thalwegs of bedrock valleys, Alberta (GIS data, line features); Alberta Energy Regulator, AER/AGS Digital Data 2018-0001.