Analysis of coastal geomorphological processes on a boreal coarse clastic barrier: Long Pond Barachois, Conception Bay, Newfoundland

Pittman, Donald Paul (2004) Analysis of coastal geomorphological processes on a boreal coarse clastic barrier: Long Pond Barachois, Conception Bay, Newfoundland. Masters thesis, Memorial University of Newfoundland.

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Abstract

Long Pond Barachois is a single-ridged open-work gravel-dominated baymouth barrier adjacent to an asymmetric double-basined lagoon. Sea level rise, climate, and inherited geology have controlled long term barrier evolution but human activities have modified littoral processes and barrier morphology. Updrift shoreline armouring induced barrier stretching and breaching, generating a curved planform and a permanent tidal inlet. Tidal exchange generated strong currents in the channel, scouring the backbarrier. This induced in-place narrowing, which was exacerbated when shore-normal breakwater construction in 1973 formed a sediment sink, allowing the inlet-adjacent beach segment to prograde. The narrowed barrier segment breached during a 1976 storm which also induced sluicing overwash north of Burnt Island and cusp-related overwash between the island and the channel. The breach was repaired with silt-rich dredge spoil, placing the barrier in a state of arrested breakdown. The breach repair site has proven very erosion-prone. The barrier breached at the same site in 1992, without overwashing elsewhere on the barrier. The breach was again repaired with silt-rich dredge spoil. Erosion problems have persisted and the barrier is probably not sustainable in its current form in the long term. -- Sluicing overwash occurred due to cyclic barrier narrowing and barrier overstepping onto an impermeable substrate. The crest was low and the barrier has narrowed since 1976. Access road construction has placed a flat impermeable surface on the northern backbarrier and narrowed the berm. Two residences have been constructed in hazard zones. These activities have limited potential management options.

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