In order to assess the processes affecting recent erosion of the shoreline adjacent to Fort Anne National Historic Park, a preliminary study of sediment properties and patterns of water flow in Allain River and across the Fort Anne shore was conducted in May and June 1993. Stations were also established for longer term monitoring of changes in bed level of deposited sediments in the intertidal zone, and for indications of rotational slumping of the Fort Anne embankment where cribwork is exposed.

Geotechnical investigations included the obtaining of 2 cores and measurements of sediment consolidation at 5 sites in the intertidal zone. The cores indicate that much of the shore is composed of a stiff, highly plastic red clay of glaciolacustrine origin that extends to the maximum depths of the cores (1.4 and 2.5 m). Penetrometer measurements showed that the sediment is overconsolidated to degrees that correspond to previous burial beneath 1 to 4 m of overburden. The exposed clay surface, however, has softened and lost cohesion as a result of wetting and bioturbation. It is concluded that erosion of this deposit will continue as long as the surface is exposed to tidal water, resulting in continued lowering of the intertidal zone, and further destabilising of the fort embankments.

Current meters installed on the shore for 12 tides indicated that water flows across the shore in a northerly direction during both ebb and flood. This feature is strongly influenced by the pattern of water movement in Allain River, which in part is determined by a man-made constriction near the Highway 1 bridge. A 105 m long, 1 to 1.2 m high barrier temporarily installed down the shore between Fort Anne and the point significantly reduced velocities across the shoreline, particularly on the Allain River side, but did not seem to greatly change the direction of flow. Diminishing current velocity may be a valuable contribution to decreasing erosion on the shore.

Results of the study lead to recommendations including: widening of the Allain River at the highway bridge by removing a rocky constriction left behind from previous construction; re-establishing a stabilising mass at the toe of the western embankment where erosion is very active and the embankment seems to be most unstable; providing immediate protection against erosion of the remaining saltmarsh; conducting further investigations of the load-bearing properties of the exposed clays, and of the water table within the embankment; and protecting exposed clays against softening of the surface by wetting and bioturbation.