The evolution of the Rhône delta coast is analysed using digitally processed data obtained from field surveys effected in 1895, aerial photographs taken in 1940, 1950, 1960, 1970, 1980 and 1990, and a DGPS-based survey carried out in 2000. The whole dataset was integrated into a Geographic Information System to determine coastline retreat and advance and to quantify gains and losses of land area at the coastal fringe of the delta. It is shown that sediment input from the Rhône, longshore drift currents and sea defences have had a marked influence on space-time variations of the position of the coastline. These data enable characterisation of the morphose- dimentary circulation at the coast, and the identification of a clear pattern of littoral sediment cells.

The Mediterranean basin (including the Black Sea) is characterized by a plethora of deltas that have developed in a wave-influenced setting. Many of these deltas are sourced in sediments by river catchments that have been variably dammed. The vulnerability status of a selection of ten deltas subject to different levels of reduction in fluvial sediment supply following damming was analysed by quantifying changes in delta protrusion area and protrusion angle over the last 30 years. The rationale for choosing these two metrics, which do not require tricky calculations of longshore bedload transport volumes and river ‘influence’, is that as sediment supply wanes, increasing relative efficiency of waves leads to longshore redistribution of reworked sediments and progressive ‘flattening’ of the delta protrusion. The results show that eight of the ten deltas (Nile, Rhône, Ebro, Ceyhan, Arno, Ombrone, Moulouya, Medjerda) are in erosion, whereas two (Danube, Po) show stability, but the statistical relationship between change in delta protrusion area and sediment flux reduction is poor, thus suggesting that the role of dams in causing delta shoreline erosion may have been over-estimated. But this poor relationship could also be due to a long temporal lag between dam construction and bedload removal and transport to the coast downstream of dams, and, where the delta protrusion is being eroded, to bedload trapping by shoreline engineering structures and by elongating delta-flank spits. Other potential influential factors in shoreline change include subsidence, sea-level rise, storminess, exceptional river floods, and managed sediment releases downstream of dams. A longer observation period and high-resolution sediment-budget studies will be necessary to determine more definitively to which extent continued trapping of sediment behind dams will impact overall delta stability in the Mediterranean and Black Seas. Mitigation of delta erosion is likely to become costlier under continued sediment starvation and sea-level rise.

The dynamics of the sandy coast between Castellaneta and Taranto (Southern Italy) has been influenced by many natural and anthropogenic factors, resulting in significant changes in the coastal system over the last century. The interactions between vertical components of sea-level changes and horizontal components of the sedimentary budget, in combination with anthropogenic impact, have resulted in different erosion and accretion phases in the past years. Local isostatic, eustatic, and vertical tectonic movements, together with sedimentary budget changes, must be considered in order to predict the shoreline evolution and future marine submersion. In this study, all morpho-topographic data available for the Gulf of Taranto, in combination with Vertical Land Movements and sea-level rise trends, were considered by assessing the local evolution of the coastal trend as well as the future marine submersion. Based on the predicted spatial and temporal coastal changes, a new predictive model of submersion was developed to support coastal management in sea-level rise conditions over the next decades. After that, a multi-temporal mathematical model of coastal submersion was implemented in a Matlab environment. Finally, the effects of the relative sea-level rise on the coastal surface prone to submersion, according to the Intergovernmental Panel on Climate Change Assessment Reports (AR) 5 Representative Concentration Pathways (RCP) 2.6 and RCP 8.5 scenarios, were evaluated up to 2100.

Résumé Les apports solides jouent un rôle déterminant dans la mobilité holocène des littoraux du delta du Rhône. Les phases de progradation deltaïque sont associées aux apports solides abondants et grossiers qui sont liés aux forçages climatiques et anthropiques dans les bassins versants. Cette relation est cependant modulée par les variations de vitesse de montée du niveau marin, par l'amplitude de l'espace de sédimentation et par la géomorphologie du chenal fluvial. La mobilité des lobes deltaïques est analysée depuis 7000 ans, avec un intérêt particulier pour les périodes de défluviation et de déplacement des embouchures, dont les causes sont discutées. L 'embouchure actuelle et trois bras fossiles sont étudiés : le bras de Saint-Ferréol (4000 ans BP-vr siècle ap. J.-C), les Bras de Fer et de Pégoulier (xvi-xix° siècles ap. J.-C, i.e. pendant le Petit Âge Glaciaire). À partir du XIXe siècle, les aménagements favorisent les ultimes avancées du delta et perturbent le déroulement naturel des avulsions.

Comme son nom l’indique, le Coastal Engineering Manuel (CEM), proposé par l’U.S. Army corps of Engineers (USACE) est un manuel d’ingénierie côtière. Le CEM, qui comporte 6 volumes et totalise presque 3000 pages, est diffusé par VeriTech Cie (http://www.veritechinc.net/main.php) au format pdf (environ 350 Mo) ou papier. L’objectif du CEM est de proposer, dans un unique et accessible document, les méthodes et procédures de planification, de gestion, de construction et d’entretien des projets d...

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.