Multi-Decadal Deltaic Land-Surface Changes: Gauging the Vulnerability of a Selection of Mediterranean and Black Sea River Deltas

Abstract

Areal changes over delta surfaces determined by land and water ratios are a promising tool for identifying spatial and temporal changes in deltas that may reveal subsidence and shoreline erosion. Such changes can also provide the basis for more detailed studies on variations in land-cover and vegetation. Changes in land and water areas over a 35-year period (1984–2019) were determined for a selection of ten river deltas in the Mediterranean (Nile, Rhône, Po, Ebro, Moulouya, Ceyhan-Seyhan, Medjerdja, Ombrone, Arno) and the Black Sea (Danube), with a particular focus on aspects of subsidence and shoreline erosion. With the exception of the Ombrone, Arno, and Moulouya, and to lesser extent the Medjerdja, where notable changes dominate in the coastal zone and are tantamount to net erosion, the spatial pattern is largely dominated by delta-plain changes characterized by increasing areas of water. The pattern reflects a mix of shoreline erosion, land-use and land-cover changes, such as the ecological restoration of wetlands, but also increasing subsidence in these deltas, all of which have been exposed to a declining fluvial sediment supply due to human influence. The use of data on land-water ratios needs to be complemented by more detailed studies devoted to each delta in order to clearly disentangle changes related to land-use, vegetation, and subsidence. It is also important to determine how wetlands are interpreted in such ratios, as these important ecological elements are sensitive to ratio variations. It would also be interesting in future studies to examine how these variations play out over time, notably in deltas where changes have been significant over the period 1984–2019.

Convolutional Neural Network and Optical Flow for the Assessment of Wave and Tide Parameters from Video Analysis (LEUCOTEA): An Innovative Tool for Coastal Monitoring

“…On the other hand, widespread video monitoring stations could improve the assessment of storm surge parameters, in which the tide gauges are unevenly distributed along the coasts and mainly located in the harbors, meaning that video monitoring could assess the storm surge directly impacting the coasts [4,99]. This is particularly important to predict the effect of coastal flooding and submersion in susceptible areas, such as wetlands [100], deltas [101], low-lying coasts [33], and highly populated coastal cities [33,102].…”

Impacted fluvial and coastal sediment connectivity in the Mediterranean: a brief review and implications in the context of global environmental change

“…Several deltas and distant coasts dependent on the rivers have become more or less severely eroded as a result of negative sediment budgets (Besset et al, 2017). By reducing river liquid discharge and sediment supply, human activities upstream have favoured accelerated subsidence of deltas (Figure 4), whereas extractive activities can exacerbate this problem in the delta environment itself (Anthony et al, 2021), invariably enhancing the potential influence of waves in washover processes and in dispersing deltaic bedload and fine-grained sediment, but also in exacerbating coastal erosion. Some of the causes of, and the responses to, shoreline destabilization have been essentially a matter of 'hard' engineering, for both historical and cultural reasons (e.g., Pranzini et al, 2018).…”

Coastal Erosion Caused by River Mouth Migration on a Cuspate Delta: An Example from Thanh Hoa, Vietnam

“…Cuspate deltas, which were first defined by Wright and Coleman [1], are examples of deltas that protrude slightly into open water. They have been the object of numerous studies by coastal scholars [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] because they are one of the three most widely seen delta morphologies classified by Galloway [3]. According to Galloway [3], this type of landform was designated as a wave-dominated delta because the morphologies of these deltas are formed mainly via the interaction between riverine (sediment supply) and ocean (waves) forces.…”