Estuarine Mapping and Eco-Geomorphological Characterization for Potential Application in Conservation and Management: Three Study Cases along the Iberian Coast

Abstract

Geomorphological changes in recent decades in three estuaries along the Iberian coast were analysed using aerial orthophotographs. A hierarchical classification scheme, based on a literature review representing 26 estuarine eco-geomorphological features relevant to estuarine dynamics and functioning, is described. The estuaries selected were San Vicente de la Barquera (N Spain), Guadiana River (SW border between Spain and Portugal) and the Ebro River Delta mouth (NE Spain). For these systems, a 60-year time series of high-resolution maps was developed, analysing the changes in feature surfaces. The main subsystems analysed were beach, dunes, saltmarshes and the drainage network. The results of the cartographies showed general behaviour common to all transitional systems, relationships among main subsystems and processes inherent to each one. This work illustrates how beaches and dunes serve as a protective barrier for the tidal flats, acting as a sediment buffer for the entire system. The subsystems are connected by the drainage network responsible for the exchange of matter and energy between them. Furthermore, an accuracy assessment was performed in one of the study zones to identify the limitations of mapping with aerial photographs. The results explain the changes with time but also the processes and relationships between the estuarine features at a long-term scale. This work adds an important perspective towards a general understanding of their dependence on intrinsic and boundary conditions.

Vulnerability Analysis of the Riumar Dune Field in El Garxal Coastal Wetland (Ebro Delta, Spain)

“…Although the little urban area of Riumar is a touristic zone, the number of visitors is low. According to Aranda et al [38], this area did not suffer remarkable changes in anthropic features due to its qualification as a Natural Park in 1989.…”

“…Figure 1 shows sandy hooks developed in front of the dune field. These hooks slowly connected to the land and enabled coastal development [21,38]. Moreover, these sand bars favoring the presence of a wide beach, which has been quantified in 116 m on average.…”

Dynamics and sedimentary assessment of a rock-bounded estuary: a case study—Tina Mayor (NW Spain, Iberian Peninsula)

“…The monitoring has also detected the morphological and sedimentary changes in the interior of many of the Cantabrian estuarine systems (Flor-Blanco and Flor 2019), which, in contrast, are directly related to the impact of climate change in terms of sea-level rise and, above all, to the recurrence of extreme storm wave events (Guisado Pintado and Jackson 2019;Castelle and Harley 2020a, b;Flor-Blanco et al 2021) that favour massive sediment intrusion into estuaries. A clear example has been seen in San Vicente de la Barquera with significant loss of saltmarsh vegetation due to sediment intrusion (Aranda et al 2020a), but also other types of ecological changes in estuaries and deltas (Aranda et al 2020b). While in other parts of the world, climate change is linked to human influence (Chen et al 2019).…”

The complexity of studying coasts: From forms and processes to management

“…If they receive enough sediment supply and include sufficient space inland to migrate, usually inside wide estuaries and bays, they can face a sea level rise if it occurs at not very high rates (Sampath et al, 2011;Best et al, 2018). Other conditions, like accelerated sea level rise, or decrease in the sedimentary supply to estuaries, however, may progressively submerge salt marshes until their permanent flooding (Hofstede et al, 2018;Aranda et al, 2020). These environments, and coastal wetlands in general are highly vulnerable systems to rapid sea level rise (Fernández-Núñez et al, 2019).…”

“…The morphological and ecological evolution of salt marshes in the last decades can be analysed through aerial photographs (Aranda et al, 2020). Monitoring of salt marsh dynamics and their biogeomorphological trends are analysed through satellite imagery, LiDAR and high-resolution mapping (Haynes et al, 2017) combined with sediment sampling and textural analysis (Chen et al, 2018).…”