Marine erosion of the Point Grey cliffs

Abstract

At the edge of Vancouver and the Strait of Georgia the Point Grey cliffs experience marine and subaerial erosion. The retreat of the cliffs will eventually result in losing university assets, infrastructure and archaeological treasures. Wave-induced sediment transports are supposed to be the main marine erosion mechanism. This report presents other potential marine erosion mechanisms (e.g. direct wave attack, sediment budget deficits, sea-level rise and increased storm intensity) over different time scales and studies the sediment transport and budgets in more detail. The study is performed with the help of a numerical hydrodynamic model with representative scenarios of the hydrodynamic conditions. The model and scenarios are set-up by means of a site visit, literature, water level records, wind and wave records and sediment samples. The resulting scenarios and results provide an hydrodynamical overview of flow- and wave conditions. Subsequently, the sediment transports, indeed, seem to be initiated by waves. Results also opened up a new potential sediment transport path not yet mentioned by sources. However, the sediment transports does not seem to be the only erosion mechanism. A potential human-induced sediment budget deficit is likely as well. Additionally the direct wave attack and the combined sea-level rise and intensified storms are also either present or becoming more relevant in the future. The contents of this report forms a basis for developing design criteria for a coastal solution to the marine erosion of the Point Grey cliffs. An engineered beach, together with a foreshore nourishment, out of locally dredged material seems like the most logical option. By further improving the numerical model and the overall study with presented recommendations, this study can inspire further design steps for a solution to save the Point Grey cliffs.