Beach Response to a Shoreface Nourishment (Aveiro, Portugal)

Diogo Mendes,Paulo Baptista,Cristina Bernardes,Joaquim Pais-Barbosa,Paulo A Silva,Celso Pinto

doi:10.3390/jmse9101112

Diogo Mendes, Paulo Baptista + Show 4 more

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https://doi.org/10.3390/jmse9101112

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Abstract

In Aveiro (NW coast of Portugal), a coastal monitoring programme was carried out in sequence of a shoreface nourishment intervention (over than 2 M m3) performed in 2020. In this programme, almost one year of biweekly subaerial topographies and quarterly bathymetric surveys have been collected along a 10 km coastal stretch between June 2020 and June 2021. In this study, topographic and bathymetric surveys were analysed to assess the expectation that if the shoreface nourishment is located in sufficiently shallow water depths, its landward movement will feed adjacent beaches and, consequently, increase the subaerial beach volume. Results show that the subaerial beach volume is well correlated with the 1.05 m (above MSL) isoline displacement through time. While the seaward limit of the shoreface nourishment moved landwards about 200 m, the shoreline proxy (isoline of 1.05 m) displayed a maximum seaward displacement of 60 m. The displacement of the shoreline proxy was highly variable in space, along the 10 km coastal stretch, and also in time, during storm events. During such events, both landward and seawards displacement of the shoreline proxy took place, depending on the spatial position. Moreover, while beaches close to the initial shoreface nourishment intervention displayed faster accretion patterns than those located farther away, the well-defined onshore movement of the shoreface nourishment did not result in a considerable beach volume increase. The achieved results were also compared against case studies of shoreface nourishments with similar volumes performed worldwide.

Highlights

Beach nourishment constitutes a nature-based engineering solution commonly employed by coastal managers on sandy beaches [1]
The sand can be either placed on the subaerial beach or in the subtidal beach, as an underwater mound. While the former is usually referred in the literature as a beach nourishment, the latter can be referred as profile nourishment [2], berm nourishment [3], nearshore berm [4] or shoreface nourishment [5]
Note that the shoreface nourishment intervention led to morphological modifications up to −11 m (MSL) at Costa Nova (November 2020 in Figure 2a,b) but this was due to the intervention and not due to the natural beach behaviour

Summary

Introduction

Beach nourishment constitutes a nature-based engineering solution commonly employed by coastal managers on sandy beaches [1]. It comprises the placement of large quantities of good quality sand on the beach to advance it seaward [2]. The sand can be either placed on the subaerial beach or in the subtidal beach, as an underwater mound While the former is usually referred in the literature as a beach nourishment, the latter can be referred as profile nourishment [2], berm nourishment [3], nearshore berm [4] or shoreface nourishment [5]. Shoreface nourishment was used to designate the placement of sand in the subtidal zone of a beach profile

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