Wave Impact Analysis on a Beach-Dune System to Support Coastal Management and Nourishment Works: The Showcase of Mira, Portugal

Abstract

At coasts, sandy beach-dune systems act as natural barriers to environmental forcing, preventing coastal flooding and protecting coastal communities. In the context of coastal studies, it is fundamental to identify beach-dune sectors exposed to wave impact to support coastal management and suggest soft engineering interventions. This work examines the morphodynamics of the Mira beach-dune system on the northern-central littoral of Portugal over the winter 2016-2017. Coupling topographic data with the estimation of wave runup and total water level (TWL) timeseries, we proposed an operational framework to spot the beach-dune system sectors most vulnerable to dune collision and overwash. The highest topographic variations occurred in the northern sector of the study area, where overwash events occurred due to low dune crest (DC) elevation. The dune toe (DT) was frequently collided by waves in the central sector, where the upper beach profile was the most variable during winter. Overall, wave collision and overwash events were registered not only during storms, but also during spring tides and mild wave conditions. Results highlight the importance of uploading the intertidal beach slope when computing the total water levels on wave-dominated mesotidal sandy beaches, and therefore, the need for a consistent monitoring program of the coastal zones. Findings of this work also supported the coastal management of beach-dune systems, where regional authorities need to restore dune ridges to prevent further overwash events and erosion. The presented framework can be applied to build a beach-dune system vulnerability map in response to wave forecast and predicted sea-level rise.

Morphodynamic Response of Open and Embayed Beaches to Winter Conditions: Two Case Studies from the North Atlantic Iberian Coast

“…1). The beach has a length of 2500 m and an average width varying from about 40 to 80 m, as observed during the winter 2016/17 [34]. The beach is oriented NNE-SSW, limited to the north by a 200 m long groin and backed by a dune system with crest elevations ranging from 5 to 16 m. This study site is part of a sandy barrier system, bounded to the east by the Aveiro lagoon.…”

“…The local tide is mesotidal and semidiurnal, with a mean range of 2.2 m [30] Table 1. Morpho-sedimentary characteristics of Patos and Mira beaches: type, D 50 , slope, width, berm height above mean sea level, based on [30,34]. 1).…”

Observations of wave run-up affected by dune scarp during storm conditions: a two dimensional large-scaled movable bed experiment

“…Due to the effects of climate change, sea level rise, and overpopulation in coastal areas, the possibility of exposure to coastal hazards has increased, such as storms and extreme waves (Neumann et al, 2015). Moreover, approximately 30% of coastal regions have suffered from coastal erosion over the past decades (Luijendijk et al, 2018;Mentaschi et al, 2018;Fontań-Bouzas et al, 2022). Therefore, the vulnerability of coastal areas against both coastal hazards and erosion has increased, drawing considerable attention from researcher communities (Fontań-Bouzas et al, 2022).…”

“…Moreover, approximately 30% of coastal regions have suffered from coastal erosion over the past decades (Luijendijk et al, 2018;Mentaschi et al, 2018;Fontań-Bouzas et al, 2022). Therefore, the vulnerability of coastal areas against both coastal hazards and erosion has increased, drawing considerable attention from researcher communities (Fontań-Bouzas et al, 2022).…”

“…Among the nature-based structures, coastal sand dunes serve as a vital defense mechanism, protecting coastal communities from various coastal hazards such as extreme surge levels and erosion (Ciavola et al, 2014;Durań et al, 2016;Palmsten and Splinter, 2016;Phillips, 2018;Pagań et al, 2019;Jin et al, 2021). Additionally, the dunes play a crucial role as repositories of sand, facilitating the natural beach nourishment process (Houser and Ellis, 2013;Jackson et al, 2019;Fontań-Bouzas et al, 2022).…”