Abstract

The morphology and sediments of the entire glacial outwash plain shoreline of the northeast Gulf of Alaska (Cordova to Icy Point) were studied on a reconnaissance basis in 1969–71. Fifteen permanent beach profiles were established, eighteen detailed site studies (zonal studies) were carried out, and sediment samples were collected at ninety stations, using a 4 km spacing. The following general conclusions are derived from this study:

1. Coastal morphology of the area consists of:

   1. areas where outwash streams border the coast,

   2. beach-ridge plains located downdrift of the outwash streams, and

   3. the delta of the Copper River.

Depositional models have been defined for each of these morphological types.

2. Southeasterly storms dominate the coastal processes, generating strong littoral drift from east to west (as indicated by beach morphology, grain size trends, and limited field measurements.

3. Recent earthquake activity has left a major imprint on the shoreline morphology, especially in bedrock areas, where uplifted wave-cut benches are well preserved.

4. Beach morphology:

   1. The large diurnal inequality of the tides has a striking effect on beach morphology, inasmuch as wave energy is focused at four different levels on the beach during a single tidal cycle.

   2. Beach face slopes show great differences which correlate with grain size differences, the coarsest beaches having the steepest slopes.

   3. The erosional-depositional cycle on the beach closely follows the one described for the East Coast of the U. S. The cycle is initiated by a storm which leaves a flat, erosional profile. The recovery profile consists of landward-migrating ridge-and-runnel systems, and the mature profile consists of a wide, constructional berm. Storms are more numerous in Alaska, so the frequency of completion of the cycle is less than on the East Coast.