Assessing performance of a “nature‐based” foredune restoration project, Oceano Dunes, California, USA

Abstract

The Oceano Dunes near Pismo Beach, California is part of a large transgressive dune system that extends up to 5 km inland and hosts a state park that has been managed for off-highway vehicle recreation since 1982, although vehicle activity has existed in the dunes for almost 90 years. As a result, foredunes have been largely obliterated and sand surfaces in vehicle use areas are highly emissive of dust-sized particles, causing frequent exceedances of state air quality standards. To reduce dust emissions from the dunes, a nature-based foredune restoration strategy using five different treatments over a 20-ha site was implemented in February 2020.The research hypothesis is that treatments will differ in their ability to promote deposition and dune development and that more intensive planting-based treatments will outperform simpler treatments. We test this using biannual highresolution uncrewed aerial system (UAS) surveys to quantify sediment budgets, sand exchanges between beach, foredune, and backdune components, changes in plant cover, and related dune development over a 2-year period (October 2019-2021).After two full wind and plant-growth seasons, results show that all treatments are maintaining a positive sediment budget (net accumulation), most are developing sizable nebkha dunes (an important stage in foredune development in this region), and some are increasing plant cover and species richness. There is no clear winner, yet two treatments (broadcast native plant and sterile grass seeds, and a highdensity straw planting node with native seedlings) are performing well toward developing an incipient foredune. These results will inform an adaptive management process that could entail further modifications to enhance foredune development. Based on this experience, and with reference to other types of restoration projects, we refine existing criteria used to assess the performance of "dynamic" dune restoration efforts to include settings that involve revegetation (vs. devegetation) as a means for foredune re-establishment.

Post‐wildfire coastal dunefield response using photogrammetry and satellite indices

“…Significant changes are described according to the drone surveys hardware and method's respective error (LoDs) by quantifying changes in derived point clouds. Similar to recent studies (Hilgendorf et al, 2021(Hilgendorf et al, , 2022Konlechner & Hilton, 2022;Walker et al, 2022), both vegetation and surfaces changes are of research interest as they show the post-fire ecogeomorphic response of landscapes and indicate stability, dynamism or transgression. Satellite indices are used to separate landcover types and to assess the 3D changes between pre-fire sandy active areas, and regions that were burnt or unburnt.…”

“…Uncrewed aerial vehicles (UAVs) are used in many disciplines across the physical sciences (Anderson et al, 2019) and in coastal dune research (Hilgendorf et al, 2021; Walker et al, 2022). Geomorphic studies use UAV platforms and spatial data to produce 2D and 3D datasets to track landform, topographic or ground cover changes over time (Gonçalves & Henriques, 2015; Shumack et al, 2022).…”

Contemporary research in coastal dunes and aeolian processes

“…The increasing need for dune research on developed coasts was made explicit by Nordstrom (2004) in Beaches and dunes of developed coasts, and themes such as the restoration of coastal dunes have been the focus of dedicated textbooks, for example, Restoration of coastal dunes (Martínez et al, 2013). Examples of human interventions in coastal dunes in this special issue include the removal of invasive vegetation Hilgendorf et al, 2022;Konlechner & Hilton, 2022), engineered foredune notches (Nguyen et al, 2022), and intensely managed or constructed foredunes (Dickey et al, 2023;He et al, 2022;Sanromualdo-Collado et al, 2022;Walker et al, 2023).…”

“…The increasing need for dune research on developed coasts was made explicit by Nordstrom (2004) in Beaches and dunes of developed coasts , and themes such as the restoration of coastal dunes have been the focus of dedicated textbooks, for example, Restoration of coastal dunes (Martínez et al, 2013). Examples of human interventions in coastal dunes in this special issue include the removal of invasive vegetation (Bauer et al, 2022; Hilgendorf et al, 2022; Konlechner & Hilton, 2022), engineered foredune notches (Nguyen et al, 2022), and intensely managed or constructed foredunes (Dickey et al, 2023; He et al, 2022; Sanromualdo‐Collado et al, 2022; Walker et al, 2023). Many manuscripts within the special issue that investigated the coastal dynamics of naturally forming dunes also explicitly situated the research in the context of contemporary sea‐level rise and climate change (Arce Chamorro et al, 2022; Fisher et al, 2023; Garzon et al, 2022; Hesp et al, 2022; Robin et al, 2022) or hazard mitigation (He et al, 2022).…”

“…In many cases, dune evolution will depend on human action and management interventions driven by different, sometimes conflicting, values or needs, for example, natural (diversity; complexity; unconstrained; and dynamic) and cultural (stability; accessibility; predictability; and static) optimums (Nordstrom et al, 2000). As coastal dunes are increasingly being targeted as feasible ‘Nature‐based Solutions’ (NbSs) with multiple ecosystems services, as described in Walker et al (2023) for mitigating air pollution, this trend of coastal dune research increasingly focusing on management along developed coasts will likely continue.…”