Assessment of Green Measures as Coastal Defences Using Numerical Models

Climate change may reduce the performance and design life of “grey” coastal engineering interventions. Green solutions can be combined with present infrastructures providing extra flexibility to adapt our present beaches with affordable costs. This paper assesses the behaviour of a typology of green solutions (seagrass meadows) via numerical hydro-morphodynamic modelling for an erosive beach prone to episodic flooding, under typical Mediterranean conditions. A multivariate method for jointly assessing flooding and erosion via copulas is proposed and developed. In the considered pilot site, different layouts have been tested by analysing their efficiency and limits. It is concluded that, for moderate SLR rates (RCP 4.5. central trend), these green measures could attenuate efficiently the expected changes in marine drivers. However, the complexity of eco-hydraulic interactions on which the Nature Based Solutions depend would demand periodic monitoring and evaluation for maintaining acceptable risk levels, especially in the case of high-end scenarios.