Spatial and temporal changes in beach width and its effect on the condition of foredunes on Dune du Nord, Les Iles de la Madeleine

Abstract

Changes in coastal environments are a result of interacting hydrodynamic and aerodynamic processes. Spatial and temporal changes in beach width and foredune condition, some of which are influenced by climate change and (consequentially) sea level rise, are documented throughout academic literature. Data was collected from Dune du Nord on Iles-de-la-Madeleine to investigate: a relationship, or lack thereof, between beach width and foredune condition, whether chance plays a role (and to what extent) on dune scarping; and changes in foredune position between 2003 and 2018.<br> Both fieldwork and satellite image analysis were used to classify foredune condition and measure beach width, and to gather complementary data to provide context for those results. Satellite image analysis showed that between 2003 and 2018 there was significant change in foredune condition and beach width. The data shows that beach width is not a strong indicator of foredune condition on Dune du Nord. The literature shows that foredunes are more easily scarped when in front of a narrow beach, although a large enough storm may erode a foredune with a wider adjacent beach. Because beach width is continuously changing the location of foredune scarping along a beach is largely up to chance. Shifts in beach width were found to be rapid enough to change significantly before a scarped sand dune recovers to a “stable” state. This explains why scarped foredunes were found behind wide beaches. The mean beach width was found to increase from 32.30 meters in 2003 to 39.53 meters in 2018. Foredune position was found to retreat between 2003 and 2018; as 87 out of the 97 data points retreated landward.