CGRG Bibliography of Canadian Geomorphology
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Author : Barrie, J.V.; Currie, R.G.; and Kung, R.
Date : 1998.
Title : Surficial sediment distribution and human impact - Fraser Delta
Publication : Geological Survey of Canada Open File
Issue : 3572
Page(s) :
Abstract
The Fraser River Delta is a Holocene, river dominated depositional feature, built into the deep (>300 m) waters of the Strait of Georgia on Canada's Pacific coast. The delta provides much of the coastal terrain on which the port city of Vancouver and adjacent municipalities have developed. Consequently, the delta has been modified to provide ferry, coal and dredge spoil dumpsite. The confinement of the Fraser River to its present channels began during the early part of this century. Prior to this, distributary channel switching/avulsion occurred regularly. The annual river load (approximately 17.3 X 106 tonnes) is 65% silt and clay, and 35% sand, transported primarily during the spring and summer freshet. Today, most of the sand is removed from the system by dredging and the mud is transported in a plume past the intertidal estuary and northwards into the basin by the dominant flood tidal flow (tide range of 3 to 5 m). The remainder of the sand is deposited as a tractive load from the main channel of the Fraser River into active submarine channel systems asymmetrically about the river mouth. The asymmetry is a result of jetty construction on one side of the main channel. Two causeways to the south of the main channel and one to the north that cross the intertidal zone to the delta foreslope also act as barriers to the dominant northward tidal sediment transport, causing estuarine and localized seabed erosion. Here, the presence of the causeways results in tidal flow separation with clockwise back eddies forming gyres. On the delta foreslope, off the southern causeways, an eroded submarine distributary channel failure complex (Hart and Barrie, 1995) has been exposed by enhanced tidal flows that scour the seabed and form northward migrating subaqueous dunes. The erosion increases the delta slope and, consequently, risk of slope failure. This complex developed when the river mouth discharged in this region (1,000 - 3,500 14C yrs BP) and migrated freely across the delta plain.
Bibliography of Canadian Geomorphology