Beach morphodynamics and types of foredune erosion generated by storms along the Emilia-Romagna coastline, Italy

Abstract

The objectives of this study are to examine the response of a dune and beach system on the Adriatic coastline in northern Italy to the arrival of storms, compare it with seasonal (months) and medium-term (3-year) morphodynamic change, and evaluate results predicted by the numerical model XBeach. The studied coastline stretches 4 km from the Bevano River mouth to the north of the site to the township of Lido di Classe to the south, where the beach is protected by coastal structures. Fieldwork consisted of topographic profile surveys using RTK-DGPS technology (7 times over an approx. 3-year period). 103 samples of surface sediment were collected along 20 of the cross-shore profiles at 6 distinct cross-shore positions, selected on the basis of morphological beach characteristics. Data analyses of dune and beach slopes enabled the study area to be divided into 6 separate morphological zones using the spatial (longshore and cross-shore) variation of morphologies located on the backshore and intertidal beach observed in a preliminary survey of the area. Other criteria were a spatial consistency in beach slopes and/or presence/absence of intertidal morphologies identified in the aerial photographs and Lidar data. The swash zone slope did not show any significant variability for the entire area. A weak seasonal trend in the variability of the mean foredune slope was observed, with steeper slopes typically during winter and flatter slopes during summer. Analysis of grain size revealed that the beach sediment is well-sorted fine sand tending to medium, with a decreasing trend in size from the Bevano River mouth southwards towards Lido di Classe. According to the Masselink and Short (1993) classification, the natural part of the study site has an Intermediate Barred Beach (IBB) and following the Short (1999) classification, results in a modally LBT (longshore bar-trough) or LTT (low tide terrace) with a small section being TBR (transverse bar and rip). Storms are considered the main factor controlling changes in the beach and dune slope. The most significant storm was recorded in March 2010 with a peak significant wave height of 3.91 m. Contrary to the seasonal dune trend, several foredune slopes were observed to flatten following this event, which can be attributed to the action of dune slumping from the already weakened dune state. Modelling of foredune erosion, using a process-based model (XBeach), reproduced the erosion of the upper beach and dune toe reasonably well, but is currently limited by the acceptable slope value for dune stability, which does not account for biotic factors (e.g. plant roots). The comparison between the storm impact categories of Sallenger (2000) and the DSF (Dune Stability Factor) of Armaroli et al. (2012) shows a very good correspondence between the effects of the winter 2008–2009 storms and the vulnerability of the dune system predicted using both classifications

Impacts of storm chronology on the morphological changes of the Formby beach and dune system, UK

“…marram grass) is present the dune frontage at the profile of interest is relatively free from the influence of plant root stabilisation. Such biotic factors can play an important role on the dune stability increasing slope steepness (Armaroli et al, 2013). In this region the nearshore is characterised by a series of symmetrical sand ridges which are separated from the dune complex by a planer slope and are between 0.5 and 1.0 m high with a wavelength between 150 and 500 m. These features are formed due to the large tidal range and wave dominance in shoreline evolution.…”

Quick Response Assessment of the Impact of an Extreme Storm Combining Aerial Drone and RTK GPS

“…From a geomorphologic point of view, the formation of an intertidal bar after a storm event was also noticed by Armaroli et al, 2013. The scouring channels highlighted in Fig.…”

Can an early-warning system help minimize the impacts of coastal storms? A case study of the 2012 Halloween storm, northern Italy

“…4). Lido di Classe is a double-barred sandy beach of approximately 30 m in width and has natural vegetated foredunes backed by a low-lying pine forest (Armaroli et al, 2013). Eleven closely spaced (alongshore spacing = 250 m) profile lines over a 2.5 km stretch are used for validation, with dune crests ranging from 2.1 m at the southernmost profile (profile name: classe11) to 3.9 m at the northernmost profile (profile name: classe01).…”