Sedimentation In Coastal Embayments, Northeastern Gulf Of Alaska

Abstract

ABSTRACT During the last two centuries, glacial-fluvial, glacial-marine, and littoral sedimentation have completely filled at least three major embayments in the coastline of the northern Gulf of Alaska. In addition, the same processes are presently responsible for significant shoaling in Controller Bay, Icy Bay, Yakutat Bay, Dry Bay, Lituya Bay and Taylor Bay. The three filled embayments are Tsivat Bay, Kaliakh Bay and Vancouver's Icy Bay. To document the depositional histories of these nine coastal embayments, comparisons of shoreline configuration and depth were made from eighteenth century maps of exploration, nineteenth and twentieth century nautical charts and maps, and numerous ground and aerial photographs. These comparisons often permit calculation of volumes of sediment accumulated and rates of sedimentation. Sedimentation rates in the nine Gulf of Alaska coastal embayments vary, but may be as high as 2 - 3.75 m/yr. Icy Bay, Yakutat Bay, and Lituya Bay all have areas that accumulate more than one meter of sediment annually. Planning and development of harbor facilities in coastal embayments of the Gulf of Alaska must include consideration of long term deposition patterns in the selection of harbor sites. Without careful analysis of sedimentation patterns, harbors may be selected which could fill with sediment before the completion of development. INTRODUCTION The- Gulf of Alaska coastline has been mapped and explored since 1741. Numerous maps and charts, and more recently, ground and aerial photographs have been made which depict parts of the coastline and which serve as permanent records of the configuration of the coastline at specific points in time. Maps of exploration, early ground photographs, seismic surveys, recent nautical charts and maps, and 1926-1979 aerial photography document many significant changes in the configuration of the coastline of the Gulf of Alaska and in the depth of specific coastal embayments. This paper will describe changes in nine Gulf of Alaska coastal embayments and discuss the implications of sedimentation on the onshore siting of resource development facilities. The nine enbayments, (Fig. 1) from west to east are:Controller BayTsivat BayKaliakh BayIcy BayVancouver's Icy BayYakutat BayDry BayLituya BayTaylor Bay Many of the early maps of exploration are printed or drawn at scales that make it difficult to tell what is cartographic imagination and what is real. Others however, are accompanied by narratives of exploration complete with soundings and descriptions of positions. Detailed accounts of the voyages of Bering (Davidson, 1901), 0 Cook (Ellis, 1782), La Perouse (1798), and Vancouver (1798) form the basis for many of the earliest shoreline comparisons made in this paper. A detailed atlas by Tebenkov (1852), which incorporates many of the earlier maps of exploration, includes data compiled by the Russian American Company in the early nineteenth century and serves as a basis for comparison with the modern data.