Short-Term Assessment of Retreating vs. Advancing Microtidal Beaches Based on the Backshore/Foreshore Length Ratio: Examples from the Basilicata Coasts (Southern Italy)

Abstract

A straightforward conceptual method is proposed to quantitatively assess the seasonal-scale tendency of retreatment or advancement on microtidal beaches by using the backshore/foreshore length ratio. This method is based on measuring the cross-shore profile of a beach when it passes through the "transitional state" that separates the high-from the low-energy season, period during which the morphological characteristics of the beach tend to its equilibrium profile. In order to obtain real measurements of backshore (B) and foreshore (F), the definition of the limits bounding these two important components in subaerial beaches is reviewed and discussed. The approach based on the measurement of the B/F length ratio assumes that foreshore and backshore have equivalent lengths in beaches that approximate to their state of morphodynamic equilibrium (B/F ~ 1). A backshore length exceeding the foreshore length is indicative of a state of beach recession, with a B/F length ratio > 1. When the foreshore length is greater than the backshore length, the shoreline is advancing or, alternatively, it is developing in a state of morphological confinement, i.e. due to the presence of a sea cliff, with a B/F < 1. This practical method is then tested against 36 sand and gravel microtidal beach profiles measured along the coasts of Basilicata, in southern Italy. The various "beach states" are summarised into seven classes (I-VII), each identified from specific value intervals of the B/F length ratio.

An Integrated Approach between Multispectral Satellite Images and Geophysical and Morpho-Topographic Surveys for the Detection of Water Stress Associated with Coastal Dune Erosion

“…The small watercourses (Lato, Lenne, Patemisco, and Tara) that cross the sandy coast close to Palagianello and the surrounding towns do not have sufficient extension and flow rates to supply beaches [26]. There are different orders of dune ridges present along the mobile coastal system, with some extending more than 1 km inland and reaching elevations between 8 m and 17 m above sea level; these dunes are primarily stabilized by the presence of macchia mediterranea vegetation [28,30]. The beaches continued to accrete until the mid-20th century; later, however, they were subjected to erosion driven by a negative sediment balance due to the construction of dams and water collection facilities as well as the construction of tourist resorts, which led to the leveling of the foredunes [29,31].…”

Geochronology and palaeoclimatic context of submerged siliciclastic beachrock formation in the western Mediterranean Sea

“…+1.0 m and -1.5 m MSL (foreshore and upper shoreface, respectively, e.g. Longhitano (2015)). Particle size distribution was obtained with a standard nested column of sieves and a mechanical shaker.…”

Investigating submerged morphologies by means of the low-budget “GeoDive” method (high resolution for detailed 3D reconstruction and related measurements)

“…The Basilicata Tyrrhenian coast (Figure 3) is 20 Km long and is totally located in the municipality of Maratea, the only municipality of the Basilicata Region (Southern Italy) overlooking the Tyrrhenian Sea. The coast is characterized from the geomorphological point of view by a sequence of promontories, high cliffs and shore platforms, intercalated to a series of gravel pocket beaches [17], [18]. Sandy-gravel deposits that lie along the Tyrrhenian coast of Basilicata are interpreted as relict sediments [19].…”