Project Objectives

The main objective of EVREST is to develop a resilience conceptual scheme and indexes that identify coastal barrier environments self-organisation capacity and limits of the system to absorb disturbance. This can be further detailed in three objectives:

  • to identify natural mechanisms of barrier island resilience, both in oceanfront and backbarrier environments
  • to quantify timescales and evolutionary rates of barrier and lagoon environments recovery in response to coastal change drivers and
  • to evaluate scenarios of barrier island evolution on a multi-decadal scale based in modelling simulations, considering varying coastal drivers and interactions.

The timeframe for this study is the medium- to long-term, comprehending coastal evolution in periods of years to decades, and the study will be developed in a multi-inlet barrier island system (Ria Formosa) located in the south of Portugal. Four main geomorphological environments will be chosen: a) sandy barrier islands, b) dunes, c) salt marshes, and d) pristine stable zones unaffected directly by tidal inlets.

A thorough evaluation will be made of the Ria Formosa barrier system resilience, i.e. the ability of the system (including a number of subsystems) to return to the prior state after a disturbance. This analysis will address the issue of understanding how can long- and medium-term barrier evolution be compared, that is, how much can be extrapolated from medium-term observations to long-term evolution and/or how can long-term evolution information be interpolated to provide reliable data for analysis of medium-term dynamics. The datasets to measure the Ria Formosa barrier system evolution and resilience are mostly vertical aerial photographs, bathymetric charts, topographic maps, high-resolution LIDAR-based terrain models, tidal gauge timeseries, wave buoy and wave hindcast timeseries, and data-based results reported in the literature.

All elements for analysis will be gathered and incorporated into a GIS platform, taking advantage of the spatial dimension of such information. Specific study areas will be chosen for quantification of resilience, following criteria that include quantity and quality of data, representativeness of different environments, and presence/absence of eco-morphodynamic interaction.

The combined study of hydrodynamic variables, geomorphologic evolution, and characterisation of human intervention, will provide information regarding the impacts of specific events, the barrier island evolution rates and patterns, the resilience timeframe and the overall tendency during the last decades. This analysis will evaluate how timescales of evolution and resilience diverge for the different environments (for example, dunes and salt marshes) and in response to drivers and the relation between the long-term and medium-term evolution scales.

Different modelling simulations will be implemented, both on the barrier islands and in the lagoon system. Modelling techniques will be used to predict the long-term system evolution when facing different sea level rise rates, recovery after the impact of severe storms and human interventions. As a synthesis of the overall data analysis, a conceptual scheme of barrier system resilience at the longterm scale will be developed. Evolutionary processes and feedback mechanisms that enable the system recovery will be quantified. Different conditions, as extreme storms, accelerated sea level rise, sediment starvation, will be modelled for the barrier segments and the basin area. These will be used to simulate environments disruption beyond resilience limits. The identification of self-organisation capacity and limits of the system absorption will be compiled to develop innovative resilience indexes that can be straightforwardly transmitted to coastal managers and the general public.