ABSTRACT: Coastal evolution and sea level variation, Avalon Peninsula, Newfoundland: Geomorphic, climatic, and anthropogenic variation

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Abstract

Coastal evolution and sea level variation along the shores of the Avalon Peninsula of Newfoundland reflect the complex interaction of geomorphic, climatic, and anthropogenic factors. Detailed investigations and ongoing monitoring at several sites along Conception, Trinity, St.Mary's and Placentia Bays, an on the open Atlantic shore, have revealed that recent local anthropogenic activity, in conjunction with geomorphic factors and climatic changes, has resulted in significant changes in the morphology and sedimentary regimes of almost all the sites studied. With the exception of the northeastern tip of the Avalon Peninsula, marine limits following deglaciation were generally higher than the present sea level, reaching values of 20 m asl in northern Placentia and southern Trinity Bays. Continued isostatic recovery resulted in sea levels falling below present values along the entire Avalon coast during the early to mid-Holocene. In the late Holocene, sea levels gradually rose, and the southern Avalon Peninsula was affected by a short-lived transgression about 1,100 to 1,000 B.P., followed by a minor regression c. 800 B.P., and a subsequent return to transgressive conditions. Currently, sea level is rising around the entire peninsula, locally at rates approximately 7 mm/a. Erosion rates at several localities, notably Point Verde (Placentia Bay) and Salmon Cove (Conception Bay) have increased substantially in recent years, driven by combinations of anthropogenic disturbance of beach sediments, erosion of unconsolidated material, and interruptions of sediment influx from both marine and terrestrial sources. Extraction of beach material for aggregate, practiced until relatively recently, has drastically altered the configuration and sedimentary assemblages of Avalon Peninsula beaches. Beaches which have not been utilized for aggregate for more than 50 years, such as Topsail Beach (Conception Bay), have not succeeded in re-establishing equilibrium, and are undergoing rapid erosion. Erosion rates at Topsail Beach and Point Verde have exceeded 1 m/a. The combination of transgression-induced erosion and local anthropogenic activity, in conjunction with increased development of winter ice foot conditions along the shores during the last 5 years, has resulted in a general coarsening of beach textures, an increased sensitivity to large storm events, and changes in morphology of most Avalon shorelines. Many shoreline regions are settle or utilized, and local human activities are currently being disrupted by these ongoing changes

Bibliography of Canadian Geomorphology