Uncertainties in shoreline position analysis: the role of run-up and tide in a gentle slope beach

Abstract

Abstract. In recent decades in the Mediterranean Sea, high anthropic pressure from increasing economic and touristic development has affected several coastal areas. Today the erosion phenomena threaten human activities and existing structures, and interdisciplinary studies are needed to better understand actual coastal dynamics. Beach evolution analysis can be conducted using GIS methodologies, such as the well-known Digital Shoreline Analysis System (DSAS), in which error assessment based on shoreline positioning plays a significant role. In this study, a new approach is proposed to estimate the positioning errors due to tide and wave run-up influence. To improve the assessment of the wave run-up uncertainty, a spectral numerical model was used to propagate waves from deep to intermediate water and a Boussinesqtype model for intermediate water up to the swash zone. Tide effects on the uncertainty of shoreline position were evaluated using data collected by a nearby tide gauge. The proposed methodology was applied to an unprotected, dissipative Sicilian beach far from harbors and subjected to intense human activities over the last 20 years. The results show wave run-up and tide errors ranging from 0.12 to 4.5 m and from 1.20 to 1.39 m, respectively.

Storm Energy Flux Characterization along the Mediterranean Coast of Andalusia (Spain)

“…Table 2. Return period (T r ) and probability of energy flux exceedance (F(P)) for the lower and upper limit of each Class (III, IV, V) calculated using Weibull CDF Equation (3). The minimum values are highlighted with blue-colored font.…”

“…Over the last few decades, one of the faster urban developments has occurred along the Spanish Mediterranean coast, especially at the Costa del Sol [2]. As a result of this expansion, human activities and buildings were placed extremely close to the shore [3]; therefore, they are now threatened by natural hazards influenced by climate change-related processes such as sea-level rise and increases in storm frequency and intensity [4,5]. To reduce storm impacts, it is necessary to understand specific coastal characteristics and sensibilities as well as to fully comprehend storm nature.…”

The Mediterranean Coast of Andalusia (Spain): Medium-Term Evolution and Impacts of Coastal Structures

“…The precision and accuracy of aerial photogrammetric measurements depend on the total uncertainty (σ T ) associated with the determination of each shoreline position, which was sorted out by using the following relation [49]:…”

“…In fact, shoreline is usually taken as the water/land contact, especially in microtidal environments [51][52][53][54] or as the seaward vegetation limit, dune foot, or cliff top, in mesotidal environments [10,55,56]. Given the micro-tidal nature of the studied coast and the absence of foredune ridges in most part of the zone, in this work, the shoreline position was defined as "the water line at the time of the photo" [53,54] and corrections were carried out according to wave run-up (σ wr ) and tidal conditions (σ td ) in the sense of Manno et al [49]. Both parameters were calculated for the five areas in which the investigated littoral was divided.…”

Evaluating the Response of Mediterranean-Atlantic Saltmarshes to Sea-Level Rise

“…Decadal rates of shoreline change were derived using the digital shoreline analysis system (DSAS v4.0 (US Geological Survey, Reston, VA, USA); [38]) at 100 m intervals (782 transects) along the saltmarsh shoreline. DSAS has been widely used to determine shoreline change in different coastal environments, (e.g., References [39,40]). The linear regression rate-of-change (LRR), determined by fitting a least squares regression line to all shoreline points for a particular transect [38] was used here as it expresses a rate of change that takes into account all time steps across the available data.…”