Evolution of a beach–dune system following a catastrophic storm overwash event: Greenwich Dunes, Prince Edward Island, 1936–2005

Abstract

Greenwich Dunes, Prince Edward Island National Park, is a sandy mainland and barrier spit beach–dune complex stretching for about 10 km along the northeast shore of Prince Edward Island, Canada. In October 1923, surge associated with an intense storm produced catastrophic overwash along the whole length of the study area. Subsequent evolution of the system was quantified from historic aerial photographs taken in 1936, 1953, 1971, 1997, and 2005. Orthophoto mosaics were generated for each photo set using PCI Geomatica OrthoEngine, a digital photogrammetric software. Linear changes in shoreline position and areal changes in geomorphic units were evaluated for each photo set. In addition, digital elevation models (DEMs) were extracted from the 1953, 1971, and 1997 aerial photos, enabling analysis of topographic and volumetric changes. The 1936 photos show complete destruction of all foredunes, with overwash and transgressive dunes extending 300 to 600 m inland. A descriptive model of the stages of evolution of the system is proposed based on the processes controlling overwash healing and dune stabilization. Detailed topographic and volumetric changes associated with the development of an extensive transgressive dunefield and subsequent stabilization as a result of reduced sand supply due to the growth of a new vegetated foredune complex and vegetation colonization are doccumented for each stage. It was nearly 40 years before a continuous foredune system was re-established and a further 30 years before the inland transgressive dunes became completely stabilized.

Characterizing storm response and recovery using the beach change envelope: Fire Island, New York

“…shoreline position (Morton et al, 1995;Thieler and Young, 1991;Farris and List, 2007;Houser et al, 2008;Hapke et al, 2010Hapke et al, , 2016Bramato et al, 2012;Phillips et al, 2017) or dune height (Houser et al, 2008(Houser et al, , 2015Stockdon et al, 2009;Wernette et al, 2016)); whereas the other simplifies spatial information along a cross-shore profile to an averaged value (e.g. beach volume and slope) (Morton et al, 1994;Stone et al, 2004;Stockdon et al, 2007;Houser and Hamilton, 2009;Mathew et al, 2010;Scott et al, 2016). Changes in these metrics can be used to better resolve timescales (e.g.…”

“…In contrast to the timescales of event-driven changes which are fixed (i.e. the duration of the event, in days), and therefore straightforward to evaluate, recovery intervals themselves are temporally varying (days, weeks, months, seasons, years) depending on the degree of change (Wang et al, 2006;Mathew et al, 2010;Bramato et al, 2012) and cross-shore location (beach vs. dune), making the definition of the term itself limited to the interval of the study (i.e. recovery with respect to what reference point).…”

“…Anthony et al, 2006;Houser, 2009), which themselves require different instrumentation and understanding to measure and track. Coupled with the spatially (and temporally) varying levels of recovery that occur from the shoreline to the dunes (Phillips et al, 2017;Castelle et al, 2017), the measurement, evaluation, or characterization of recovery is challenging, particularly in a way that is meaningful across sites or locations (Morton et al, 1994;Hesp, 2002;Houser and Hamilton, 2009;Mathew et al, 2010;Houser et al, 2015;Scott et al, 2016).…”

Lateral vegetation growth rates exert control on coastal foredune hummockiness and coalescing time

“…The transition from washover terrace (a low surface) to a continuous dune requires individual incipient dunes to grow and merge, eventually developing into a single continuous ridge. Penland, 1988, 1990;Pye, 1983;Carter and Wilson, 1990;Davidson-Arnott and Fisher, 1992;Mathew et al, 2010;Montreuil et al, 2013). Such a conceptual model, consistent with widely observed field conditions, does not address why some initially hummocky foredunes coalesce to a linear foredune ridge, while others remain hummocky, having variable dune height in the alongshore direction, though Godfrey (1977) discussed the potential for recurring storm events to prevent the coalescing of hummocky dunes, even in locations where vegetation grows rapidly in the lateral direction.…”

Wave-Dominated Coasts

“…Washover healing may be completed within 6-10 years for individual washover fans but following large-magnitude events with inundation overwash, healing may take several decades (Davidson-Arnott and Fisher, 1992;Fritz et al, 2007;Froede, 2008;Mathew et al, 2010).…”