Abstract
Several remotely sensed images, acquired by different sensors on satellite, airplane, and drone, were used to trace the beach ridges pattern present on the delta of the River Ombrone. A more detailed map of these morphologies, than those present in the literature, was obtained, especially at the delta apex, where beach ridges elevation in minor. Beach ridges crests, highlighted through image enhancement using ENVI 4.5 and a DTM based on LiDAR data, were then processed with ArcGIS 9.3 software. Starting from this map, a method to reconstruct beach ridges segments deleted by the transformations of the territory is proposed in this paper. The best crest-lines fitting functions were calculated through interpolation of their points with Curve Expert software, and further extrapolated to reconstruct the ridges morphology where human activity, riverbed migration, or coastal erosion eliminated them. This allowed to reconstruct the ridges pattern also offshore the present delta apex, where the shoreline retreated approximately 900 m in the last 150 years. Results can be further used to implement conceptual and numerical models of delta evolution.
Highlights
Deltas are dynamic depositional landforms, sensitive to changes in both the terrestrial and marine environment [1,2], constantly reshaped by river input, tides, and waves [3,4]
Wave-dominated deltas are characterized by a cuspate morphology, a steep offshore profile, and the presence of more or less curved beach ridges parallel to past shoreline positions [5]
Beach ridges frequently evolve in coastal dunes which reflect a huge amount of sediments that are redistributed by waves and moved inland by winds forming elongated and parallel morphologies behind the coastline [10]
Summary
Deltas are dynamic depositional landforms, sensitive to changes in both the terrestrial and marine environment [1,2], constantly reshaped by river input, tides, and waves [3,4]. Wave-dominated deltas are characterized by a cuspate morphology, a steep offshore profile, and the presence of more or less curved beach ridges parallel to past shoreline positions [5]. This allowed to reconstruct Holocene delta formation phases for many rivers, and to date, the various morphologies when archaeological remnants were present or if radiometric dating were executed [6,7]. Beach ridges frequently evolve in coastal dunes which reflect a huge amount of sediments that are redistributed by waves and moved inland by winds forming elongated and parallel morphologies behind the coastline [10]. Beach ridges morphology and related pattern could be used as markers of morphodynamic variations: they can give information on past wave regime, climate conditions, sediment supply, and sea level change [13,14,15,16]
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