Coastal Floods Induced by Mean Sea Level Rise—Ecological and Socioeconomic Impacts on a Mesotidal Lagoon

Abstract

Coastal floods are currently a strong threat to socioeconomic activities established on the margins of lagoons and estuaries, as well as to their ecological equilibrium, a situation that is expected to become even more worrying in the future in a climate change context. The Ria de Aveiro lagoon, located on the northwest coast of Portugal, is not an exception to these threats, especially considering the low topography of its margins which has led to several flood events in the past. The growing concerns with these regions stem from the mean sea level (MSL) rise induced by climate changes as well as the amplification of the impacts of storm surge events, which are predicted to increase in the future due to higher mean sea levels. Therefore, this study aims to evaluate the influence of MSL rise on the inundation of Ria de Aveiro habitats and to assess the changes in inundation patterns resulting from frequent storm surges (2-year return period) from the present to the future, assessing their ecological and socioeconomic impacts. For this, a numerical model (Delft3D), previously calibrated and validated, was used to simulate the lagoon hydrodynamics under different scenarios combining MSL rise and frequent storm surge events. The numerical results demonstrated that MSL rise can change the vertical zonation and threaten the local habitats. Many areas of the lagoon may change from supratidal/intertidal to intertidal/subtidal, with relevant consequences for local species. The increase in MSL expected for the end of the century could make the lagoon more vulnerable to the effect of frequent storm surges, harming mostly agricultural areas, causing great losses for this sector and for many communities who depend on it. These extreme events can also affect artificialized areas and, in some cases, endanger lives.

Mediterranean Coastal Lagoons Review: Sites to Visit before Disappearance

“…Climate change has as a consequence on sea level rise and with it the disappearance of the sandbars due to shoreline recession [67]. These studies are the most recent on coastal lagoons, and in our study area have dealt especially with Venice [68], but are of concern in general in all coastal lagoons, especially those with urban settlements on their shores [69]. The results show that the level of the lagoons will also rise, as well as there being an increase in temperatures and salinity (especially in those that are less open to the sea) and, therefore, there will be a change in species [70] and a disappearance of lagoons that lose the coastline.…”

Evaluation of future estuarine floods in a sea level rise context

“…According to Hill 36 , when the inlet chocking number is below 5, choking becomes important, and long-wave amplitudes strongly decrease within the embayment. The long-wave continues to damp along the inner lagoon due to energy dissipation when: (1) propagating throughout shallow channels (depth lower than 1 m); and (2) flooding low-lying lands (75% de lagoon area is tidal flats 37 ). The Mondego is the estuary that presents the smallest variation in the inundated area between the extreme sea level scenarios evidencing also that the flooded barriers are very efficient in preventing the flooding of the low-lying areas adjacent to the upper estuary.…”

Impact of Extreme Wind and Freshwater Runoff on the Salinity Patterns of a Mesotidal Coastal Lagoon

“…The implementation of the Delft3D-FLOW numerical model in 3D mode constitutes a first-time application to the entire Ria de Aveiro lagoon. In fact, while there are several studies based on 2DH numerical implementations of the Delft3D-FLOW model for the Ria de Aveiro [16,33,34], no research has explored a 3D implementation of this model for the same estuarine system, according to our knowledge. Moreover, the methodology defined comprises the definition and simulation of several idealized scenarios, which intend to reproduce extreme wind and freshwater discharge events, and therefore were used to investigate the generation of horizontal salinity patterns and vertical stratification.…”