During NEARCONTROL we synthesized the current knowledge on the geological influences in coastal barrier behaviour at decadal to centennial scales (mesoscale), which allowed to benchmark the challenges in describing and understanding mesoscale coastal change and develop a hierarchy of geological controls that individually or collectively determine the behaviour of coastal barriers. We identified nearshore (or shoreface) morphology as an intermediate-level control, as although sedimentary nearshores are recognized as a dynamic feature, morphological changes occur at much longer timescales rendering nearshore morphology an effective geological control on contemporary and future coastal barrier behaviour. Detailed analysis of nearshore morphology and stratigraphy in various coastal sites in South Africa and Ireland using high-resolution geophysical data revealed wide variability in nearshore configuration, which consistently departed from equilibrium models and often presented compound profiles. Our results show that the underlying bedrock and stratigraphic surfaces exert spatially variable nearshore geological control, with the wave ravinement surface (i.e. erosional surface created by wave erosion and scour as the coastline migrates landward with SLR) being prevalent in determining the morphological configuration of sedimentary nearshores. The dependence of the modern nearshore surface on the underlying wave ravinement surface confirms that contemporary nearshore dynamics are underpinned by antecedent wave erosion, highlighting the importance of extreme coastal storms in shaping the past, present and future nearshore morphology. For Ireland in particular, our results show positive temporal trends in the frequency and intensity of coastal storms over the past 60 years, indicating that winter wave conditions are becoming more energetic and stormier with attendant implications for nearshore morphological behaviour and future evolution. We also quantified storm-induced nearshore morphological change with unprecedented detail in a South African embayment, and these results were integrated with hydrodynamic numerical models to explore the coupling between inherited large-scale bedforms and nearshore waves in the development of nearshore erosional hotspots.
The response of sedimentary barriers and nearshore areas to accelerated SLR in a changing climate will be overwhelmingly determined by the geological and stratigraphic framework of the coastal area to be transgressed and the extent to which future wave erosion is effective in modifying the nearshore morphology. The synchronous barrier and nearshore landward translation under SLR that is still assumed in most mesoscale coastal evolution modelling approaches is far from ubiquitous, and the conceptual and analytical approach that underpins the equilibrium-profile model grossly oversimplifies the processes and mechanisms of coastal evolution. Our results demonstrate that decoupled barrier-nearshore evolution over an irregularly erodible surface is to be expected for most sedimentary coasts and that progress in predicting mesoscale coastal evolution requires an improved understanding of nearshore erosion during extreme coastal storms.
The research developed and results obtained have been and will continue to be disseminated in various ways. So far, 10 manuscripts have been published or submitted for peer-review in scientific journals, 16 presentations have been delivered to national and international conferences, 1 MSc thesis has been completed, a conference session and a workshop have been organized, as well as a training event and one outreach activity.
