Nearshore Sandbar Classification of Sabaudia (Italy) with LiDAR Data: The FHyL Approach

Andrea Taramelli,Emiliana Valentini,Lorenzo Rossi,Sergio Cappucci,Iolanda Lisi

doi:10.3390/rs12071053

Abstract

An application of the FHyL (field spectral libraries, airborne hyperspectral images and topographic LiDAR) method is presented. It is aimed to map and classify bedforms in submerged beach systems and has been applied to Sabaudia coast (Tirrenyan Sea, Central Italy). The FHyl method allows the integration of geomorphological observations into detailed maps by the multisensory data fusion process from hyperspectral, LiDAR, and in-situ radiometric data. The analysis of the sandy beach classification provides an identification of the variable bedforms by using LiDAR bathymetric Digital Surface Model (DSM) and Bathymetric Position Index (BPI) along the coastal stretch. The nearshore sand bars classification and analysis of the bed form parameters (e.g., depth, slope and convexity/concavity properties) provide excellent results in very shallow waters zones. Thanks to well-established LiDAR and spectroscopic techniques developed under the FHyL approach, remote sensing has the potential to deliver significant quantitative products in coastal areas. The developed method has become the standard for the systematic definition of the operational coastal airborne dataset that must be provided by coastal operational services as input to national downstream services. The methodology is also driving the harmonization procedure of coastal morphological dataset definition at the national scale and results have been used by the authorities to adopt a novel beach management technique.

Highlights

Nearshore bar dynamics are the main expression of breaking-wave-induced hydrodynamics and sediment transport patterns taking place along the coast
The analysis of the sandy beach classification provides an identification of the variable bedforms by using light detection and ranging (LiDAR) bathymetric Digital Surface Model (DSM) and Bathymetric Position Index (BPI) along the coastal stretch
Past researches have proposed several methods to predict the nature of the cross-shore equilibrium profile and to classify the beach morphodynamic state based on the detection of different bars systems in the surf zone [1,6]

Summary

Introduction

Nearshore bar dynamics are the main expression of breaking-wave-induced hydrodynamics and sediment transport patterns taking place along the coast. The use of morphodynamic classification of the beach system is often recommended [3,4] It should be based on the analysis of coastal processes and beach response under a wide range of physical parameters. In this regard, the dimensionless sediment fall velocity (often referred to as the Dean number) and the wave steepness are commonly considered as key parameters to predict and define the nature (barred or non-barred) of a cross-shore equilibrium profile (e.g., [5]). Past researches have proposed several methods to predict the nature of the cross-shore equilibrium profile and to classify the beach morphodynamic state based on the detection of different bars systems in the surf zone [1,6]. The most recent and complete classifications take into account the interaction between the main physical parameters (i.e., wave energy, sediment grain size, seabed slope, shape of bed forms, etc) that affect the equilibrium of both the cross-shore and alongshore beach profile (e.g., [7,8,9])

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