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

Francisco Silveira,Carina Lurdes Lopes,João Miguel Dias,João Pedro Pinheiro,Humberto Pereira

doi:10.3390/jmse9121430

Francisco Silveira, Carina Lurdes Lopes + Show 3 more

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https://doi.org/10.3390/jmse9121430

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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.

Highlights

Climate change has impacts in estuaries and lagoons all over the world, as highlighted in the last Intergovernmental Panel for Climate Change (IPCC) report that refers to sea level rise driven by climate change which will exacerbate the flooding frequency in coastal areas along the present century
The main goal of this work is to assess the impact of mean sea level (MSL) rise on ecological and socioeconomic status of the Ria de Aveiro lagoon, evaluating: (1) how MSL rise can affect the vertical zonation resulting from the distribution of subtidal and intertidal regions as well as the distribution of the mean sea surface elevation, discussing how these changes will possibly affect the natural protection against inundations, and (2) how MSL rise will potentially change inundation patterns resulting from frequent storm surges (2-year return period) under present and future scenarios, discussing how these events can affect socioeconomic activities
The present study revealed that the MSL rise may change the current flooding patterns of a mesotidal lagoon, impacting its ecological and socioeconomic status

Summary

Introduction

Climate change has impacts in estuaries and lagoons all over the world, as highlighted in the last Intergovernmental Panel for Climate Change (IPCC) report that refers to sea level rise driven by climate change which will exacerbate the flooding frequency in coastal areas along the present century. An example of extreme storm surge events was the hurricane Wilma in 2005, causing the death of 23 people and a damage evaluated at USD 22.4 billion [2]. The combination of these factors might increase the probability of coastal flooding, putting at risk ecosystems, livelihoods/goods and millions of people living in coastal regions [3]. Several examples of estuaries and lagoons subject to coastal flooding can be found around the word over the past few centuries, leading to the construction of barriers or other heavy infrastructures to protect the people and goods at risk [4]. To prevent the inundation effects, a flood barrier was built with an estimated cost of GBP 461 million [6]

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