ABSTRACT: River channel migration and erosion of a national historic site in southern Alberta.

CGRG Bibliography of Canadian Geomorphology
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Abstract

Fort Whoop-Up is a national historic site located at the confluence of the Oldman and St. Mary’s Rivers. As an important part of southern Alberta’s history, the Fort served as the first major trading post in western Canada and was designated a National Historic Site in 1970 due to its role in establishing the Northwest Mounted Police. However, because the Fort is located on a floodplain it is vulnerable river erosion and flooding. To document rates of erosion and channel migration a study was undertaken using historical aerial photographs (1926-1999) and GIS. Changes in channel activity were quantified by measuring the area enclosed by successive channel centrelines. The latter were digitized on rectified aerial photographs. For each interval, the centreline length and intervening area were used to calculate the mean rate of lateral migration (m/year). Results indicate that the river channel in the vicinity of Fort Whoop-Up has evolved from several different processes, including lateral extension, downvalley translation, and meander cutoff. Bedrock confinement upstream of the Fort is a major factor contributing to the progressive encroachment of the channel towards the site (6.8 m/y). To this end, continued downvalley translation is considered to be the main process threatening the long term preservation of this site. If the long term trend continues without bank stabilization, this cultural historic site will likely be eroded in the next 20-25 years.

Bibliography of Canadian Geomorphology