Nature-Based Solution along High-Energy Eroding Sandy Coasts: Preliminary Tests on the Reinstatement of Natural Dynamics in Reprofiled Coastal Dunes

Abstract

This paper describes a large-scale experiment designed to examine if reinstating natural processes in the coastal dune systems of Southwest France can be a relevant nature-based adaptation in chronically eroding sectors and a nature-based solution against coastal hazards, by maintaining the coastal dune ecological corridor. An experiment started in late 2017 on a 4-km-long stretch of coast at Truc Vert, where experimental notches were excavated and intensively monitored in the incipient and established foredunes. Preliminary results indicate that most of the excavated notches did not develop into blowout. Only the larger elongated notches subsequently excavated in the established foredune in 2018 showed evidence of development, acting as an effective conduit for aeolian landward transport into the dunes. All notches were found to have a statistically significant impact on vegetation dynamics downwind, even those that did not develop. The area of bare sand landward and within the elongated notches notably increased implying a loss of vegetation cover during this first stage of development. Observations of a nearby coastal dune system that has been in free evolution over the last 40 years also indicate that, although the dune migrated inland by more than 100 m, it is now mostly made of bare sand. Further work is required to explore if and how dunes maintained as dynamic systems can become an efficient nature-based solution along this eroding coastline.

16 years of topographic surveys of rip-channelled high-energy meso-macrotidal sandy beach

“…It is a remote beach located more than three kilometers from the first inland carpark beach entry. Apart from the backing coastal dune which has been reprofiled in the early 80 s 37 , Truc Vert has never been nourished or affected by hard structures and tourism. This motivated the first topographic measurements in the late 90 s, surveying irregularly in time a single profile with a theodolite 38 .…”

“…It covers a wide range of storms and of isolated extreme events 53 , an anomalous winter with severe storm clustering 17,41 and a few cycles of large interannual beach variability. This monitoring program is also entering a new era as, since 2016, 4 km of coastal dunes are now surveyed at least quarterly 54,55 , together with notches dug in the dune to reinstate dune mobility and address plant community restoration along with biological monitoring 37 . With the growing interest in long-term beach datasets 23,30 and growing need of validation data for a wealth of coastal models 56 , it is timely to facilitate the unrestricted use of this unique high-energy meso-macrotidal beach dataset, including the daily surveys during the ECORS'08 field campaign.…”

Spatial Variation in Coastal Dune Evolution in a High Tidal Range Environment

“…For example, their coastal protection function has been valued in the US as $86,000 per hectare per year [2]. In recent years, observations have been made of increased vegetation and stabilization of coastal dunes [3,4], leading to vigorous debate on the appropriateness of intervention [5,6] and research into intervention efficacy, e.g., [7,8]. Proper understanding of the drivers of dune evolution in all forms of coastal environment is required to inform an adequate suite of management practices.…”

Classification of Atlantic Coastal Sand Dune Vegetation Using In Situ, UAV, and Airborne Hyperspectral Data

“…These management strategies generally include beach nourishment [13], vegetation planting [14], sand fencing [15], or mechanical reprofiling [16]. Recently, in some regions of the world, this method of stabilization has been challenged by another method that encourages the dynamism of the environment in order to restore dune diversity and mobility [17][18][19]. Indeed, coastal dune vegetation can affect the vulnerability of coastlines by determining the maximum height of the foredune, but also their resilience, by modifying sand mobility [20,21].…”