Geomorphic and sediment volume responses of a coastal dune complex following invasive vegetation removal

Abstract

This paper documents application of an established geostatistical methodology to detect significant changes in a foredune-transgressive dune complex where Parks Canada Agency (PCA) implemented a dynamic restoration program to remove invasive marram grasses (Ammophila spp.) and enhance dynamic dune habitat for an endangered species. Detailed topographic surveys of a 10 320 m 2 site in the Wickaninnish Dunes in Pacific Rim National Park, British Columbia, Canada for the first year post-treatment are compared to a pre-restoration LiDAR baseline survey. The method incorporates inherent spatial structure in measured elevation datasets at the sub-landscape scale and models statistically significant change surfaces within distinct, linked geomorphic units (beach, foredune, transgressive dune complex). Seasonal and annual responses within the complex are discussed and interpreted.All ) mostly from supply to the supratidal beach and incipient dune. This sediment influx occurred independent of the restoration effort and was available as a buffer against wave erosion and as supply to the landward dunes. The foredune received +200 m 3 (0 Á 13 m 3 m -2) and its seaward profile returned to a similar pre-restoration form following erosion at the crest from vegetation removal and scarping by high water events. Sediment bypassing and minimal change was evident at the mid-stoss slope with appreciable extension of depositional lobes in the lee. The transgressive dune complex experienced high accretion following restoration activity (+201 m ) mostly from depositional lobes from the foredune, precipitation ridge growth along the downwind boundary, and growth of existing lobes within the complex. Further integration of this methodology to detect significant geomorphic changes is recommended, particularly for applications where sampling densities are limited or logistically defined.

Post‐disturbance evolution of a prograded foredune barrier during a sustained dynamic restoration project—the role of wind speed, wind direction and vegetation

“…Field studies show that rapid vegetation mortality can promote localized substrate mobility, topographic change and downwind dune migration (Arens et al, 2004;Darke et al, 2016;Eamer et al, 2013;Ruessink et al, 2018;Shumack & Hesse, 2018;Walker et al, 2013).…”

The role of physical disturbance for litter decomposition and nutrient cycling in coastal sand dunes

“…Recently, scientists and coastal dune stakeholders have been attempting to reintroduce a certain dynamic in stabilized coastal dunes characterized by high plant cover and biomass (Creer et al, 2020;Pye et al, 2020;Arens et al, 2020). This is particularly the case in Northern Europe where some remobilization projects are attempting to restore a dynamic of sediment transport from the beach to the back of the dune by removing vegetation or foredune notch excavation (Eamer et al, 2013;Konlechner, et al, 2015;Arens et al, 2013;Kuipers 2014). In these low-stress coastal dunes, these methods have been shown to be successful in increasing sand transport and thus disturbance in the dunes (Ruessink et al, 2018), leading to an increase in diversity, by reducing competition, and a rejuvenation of the soils (Brunbjerg et al, 2015;Nordstrom et al, 2007), confirming the CSR model (Grime, 1974).…”

Dynamic restoration and the impact of native versus invasive vegetation on coastal foredune morphodynamics, Lanphere Dunes, California, USA

“…We note a distinct difference in management and restoration goals, differentiating species-driven practices from contemporary 'dynamic' restoration practices. Dynamic restoration aims to restore the form and function of a geomorphic system and improve landform resilience to external pressures by employing complementary native plant species (Arens et al, 2013;Cooper & Jackson, 2020;Darke et al, 2013Darke et al, , 2016Delgado-Fernandez et al, 2019;Eamer et al, 2013;Pickart, 2013;Walker et al, 2013). We regard landform resilience as an ability to maintain, regain, or translate form, in response to sea level rise or erosion.…”