Gravel Barrier Migration and Sea Level Rise: Some Observations From Story Head, Nova Scotia, Canada

Abstract

The migratory response of swash-aligned gravel-dominated barriers to sea-level rise is a relatively little-studied process. Story Head barrier, on the Atlantic coast of Nova Scotia, is swash-aligned and experiencing contemporary landward migration (6m a ^-1) via storm-generated crest overtopping and overwashing. Barrier migration rates are presented for the period 1945 to 1982. Landward migration of the seaward barrier shoreline is linearly proportional to both the 5-year smoothed rate of sea-level change (r = +0.91) and the annual sea-level change rate (r = +0.69), although the back-barrier migration rate is not related significantly to these rates of sea-level change. This difference between front and back-barrier migration response to sea-level rise reflects the intervening role of storm intensity (frequency and magnitude) superimposed on sea level rise. Story Head barrier fluctuates between dominance of barrier crest build-up by overtopping run-up and crest breakdown by overwashing flow. The balance between these two mechanisms, which controls the rate of onshore barrier migration, depends on both storm intensity and the rate of sea-level rise.