Erwan Garel

Erwan Garel
Universidade do Algarve | UALG · Centro de Investigação Marinha e Ambiental (CIMA)

PhD
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About

84
Publications
29,482
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Introduction
I am a Marine Geologist, specialized in the hydrodynamics and morphodynamics of coastal areas. My present research activities include the coastal circulation along southern Portugal, the dynamics of narrow estuaries and the morphodynamics of ebb-tidal deltas.
Additional affiliations
July 2015 - June 2020
Universidade do Algarve
Position
  • Principal Investigator

Publications

Publications (84)
Presentation
Full-text available
The main objective of this work is to assess the sediment dynamics at the inner shelf in the vicinity of the depth of closure (DoC). The present work was developed within the scope of ECOEXA project that aims to characterize the impact of sediment extraction on marine ecosystems and, at the same time, assess the respective recovery rate.
Article
Full-text available
The subtidal surface water circulation at the northern margin of the Gulf of Cádiz, at the southern extremity of the Iberian upwelling system, is described based on validated hourly high-frequency radar measurements from 2016 to 2020. Statistical analyses (mean, standard deviation, eccentricity and empirical orthogonal functions) are applied to the...
Article
Full-text available
Mechanisms that control the longitudinal transport of larvae and juveniles in nursery grounds such as estuaries are reported for some species. However, the behaviour and population consequences of these mechanisms are still uncertain. In this study, we tested selective tidal-stream transport from the along-channel (up- and downstream) and cross-cha...
Preprint
Full-text available
The subtidal surface water circulation at the northern margin of the Gulf of Cadiz, at the southern extremity of the Iberian upwelling system, is described based on validated hourly high frequency radar measurements from 2016 to 2020. Statistical analyses (mean, standard deviation, eccentricity and empirical orthogonal functions) are applied to the...
Article
Full-text available
Observations indicate that the fortnightly fluctuations in the mean amplitude of water level increase in the upstream direction along the lower half of a tide-dominated estuary (the Guadiana Estuary), with negligible river discharge, but remain constant upstream. Analytical solutions reproducing the semi-diurnal wave propagation shows that this pat...
Conference Paper
Full-text available
Meagre Argyrosomus regius (Asso, 1801) is a large oceanodromous teleost fish. Despite being highly targeted by coastal fisheries, its movement patterns are still not fully understood. In this study, we implement an innovative approach to explore the relationship between meagre movement patterns and coastal currents. We combined movement data obtain...
Preprint
Full-text available
Observations indicate that the fortnightly fluctuations in mean water level increase in amplitude along the lower half of a tide-dominated estuary (The Guadiana estuary) with negligible river discharge but remain constant upstream. Analytical solutions reproducing the semi-diurnal wave propagation shows that this pattern results from reflection eff...
Poster
Full-text available
This work explores the potential of along-tracks CryoSat-2 SAR altimetry to investigate coastal upwelling at the (E-W oriented) south Portugal-Spain coast in the Gulf of Cadiz.
Conference Paper
Full-text available
The continuous need for beach nourishment requires a detailed understanding of the sediment transport characteristics at the shelf borrow sites, to assess their recovery rate and to evaluate the long-term sustainability of these operations. The main objective of this work is to assess sediment transport conditions at an inner shelf borrow site expl...
Article
Full-text available
The alongshore subtidal water circulation along the South Portugal inner shelf is characterised by the temporal alternation of equatorward (i.e., broadly eastward) flows related to coastal upwelling processes and poleward (i.e., broadly westward) Coastal Counter Currents (CCCs). The objective of this study is to get insights about the main drivers...
Article
Full-text available
López-Ruiz, A.; Garel, E., and Ferreira, Ó., 2020. The effects of high river discharges on the morphodynamics of the Guadiana ebb-tidal delta. In: Malvárez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 558-562. Coconut Creek (Florida), ISSN 0749-0208. This work analyses the role of h...
Conference Paper
Full-text available
Artificial nourishment of sandy beaches using sediment from borrow areas located on the continental shelf is increasingly a recommended solution for reversing the erosion process that affects the coastal zone. However, the impact of sand extraction in the shelf and deposition on the beach on the benthic communities (structure and functioning) is st...
Article
Full-text available
Estuaries are essential drivers of primary productivity in coastal waters through the export of dissolved and suspended material. This study aims at quantifying this fertilization process at the two main estuaries in South Portugal, where typical low river discharge conditions occur in winter due to strong flow regulation by upstream dams and seldo...
Article
Full-text available
Assessing the impacts of both natural (e.g. tidal forcing from the ocean) and human-induced changes (e.g. dredging for navigation and land reclamation) on estuarine morphology is particularly important for the protection and management of the estuarine environment. In this study, a novel analytical approach is proposed for the assessment of estuari...
Preprint
Full-text available
Abstract. Assessing the impacts of both natural (e.g., tidal forcing from the ocean) and human-induced changes (e.g., dredging for navigation, land reclamation) on estuarine morphology is particularly important for the protection and management of the estuarine environment. In this study, a novel analytical approach is proposed for the assessment o...
Preprint
Full-text available
This paper presents the results of a pilot experiment with an existing tidal energy converter (TEC), Evopod 1 kW floatable prototype, in a real test case scenario (Faro Channel, Ria Formosa, Portugal). A baseline marine geophysical, hydrodynamic and ecological study based on the experience collected on the test site is presented. The collected data...
Article
Full-text available
As a tide propagates into the estuary, river discharge affects tidal damping, primarily via a friction term, attenuating tidal motion by increasing the quadratic velocity in the numerator, while reducing the effective friction by increasing the water depth in the denominator. For the first time, we demonstrate a third effect of river discharge that...
Article
Full-text available
Current techniques assessing longshore sediment transport rates have large uncertainties, pleading for the development of alternative and complementary approaches. The present study proposes a method to estimate the decadal average rate of longshore transport at modern ebb‐tidal deltas based on a sediment budget analysis of the outer shoal growth....
Article
A numerical model is implemented to explore the effect of the river discharge on tidal propagation along the Guadiana Estuary, a rock-bound estuary located in Southwest Iberia. The MOHID numerical model, in 2D barotropic mode, has been forced by tides at the ocean side and by freshwater at the upstream boundary of the domain. The model was validate...
Article
Full-text available
High spatial resolution coastal Digital Elevation Models (DEMs) are crucial to assess coastal vulnerability and hazards such as beach erosion, sedimentation, or inundation due to storm surges and sea level rise. This paper explores the possibility to use high spatial-resolution Pleiades (pixel size = 0.7 m) stereoscopic satellite imagery to retriev...
Chapter
Full-text available
The Guadiana Estuary is a good example of rock bounded estuary which consists of a single narrow estuarine channel with a meandering morphology imposed by faults systems affecting the hard geology of the substrate. Only along the last kilometers of the estuarine channel, the valley opens when Cenozoic Guadalquivir Basin formations appear. In this a...
Article
Full-text available
The Atlantic blue crab Callinectes sapidus Rathbun, 1896 is native in the western Atlantic, however it is a non-indigenous species across Europe since 1900, among other world regions. In this paper, we report the first occurrences of this species in the Ria Formosa lagoon and in the Guadiana estuary (SW-Iberian Peninsula, Europe) which occurred in...
Article
Full-text available
As a tide propagates into the estuary, river discharge affects tidal damping primarily through a friction term, attenuating tidal motion by increasing the quadratic velocity in the numerator, while reducing the effective friction by increasing the water depth in the denominator. For the first time, we also demonstrate a third effect of river discha...
Poster
Full-text available
ADCP time series (2008-2017) were collected on the inner shelf (23 m water depth) over 13 deployments of 1-3 months long (Fig. 1). Parameters were selected to characterize inversions based on the depth average, near bed, and surface alongshore velocities, low-passed filter at 40 h (Fig. 2, 3). Statistics analyses were applied to these parameters, c...
Article
Full-text available
This paper presents the results of a pilot experiment with an existing tidal energy converter (TEC), Evopod 1 kW floatable prototype, in a real test case scenario (Faro Channel, Ria Formosa, Portugal). A baseline marine geophysical, hydrodynamic and ecological study based on the experience collected on the test site is presented. The collected data...
Article
Full-text available
A 1D analytical framework is implemented in a narrow convergent estuary that is 78 km in length (the Guadiana, Southern Iberia) to evaluate the tidal dynamics along the channel, including the effects of neap-spring amplitude variations at the mouth. The close match between the observations (damping from the mouth to ∼ 30 km, shoaling upstream) and...
Article
Full-text available
When different tidal constituents propagate along an estuary, they interact because of the presence of nonlinear terms in the hydrodynamic equations. In particular, due to the quadratic velocity in the friction term, the effective friction experienced by both the predominant and the minor tidal constituents is enhanced. We explore the underlying me...
Chapter
Full-text available
This is a general overview of marine sand and gravel extraction. The origin of the relict or modern resource and the nature of the deposits are described, together with the related hydrodynamic and sedimentological regimes. Some important variations between countries are stressed in the marine aggregates production and usage. Details are provided o...
Poster
Full-text available
Alongshore coastal counter-currents (CCCs) are worldwide features of upwelling systems, alternating with upwelling jets of opposite direction. At the Gulf of Cadiz, CCCs are observed all year-round, i.e. including during the non-upwelling season. In this study, the current inversion patterns (i.e., the change of current direction from eastward to w...
Raw Data
These data are part of the Iberian Atlantic Margin Sediments Database (IBAM-Sed). See Costas, Susana; Ramires, Margarida; Mendes, Isabel; Ferreira, Óscar (2017): Surficial sediment texture from the Iberian Atlantic Margin Sediments Database (IBAM-Sed). PANGAEA, https://doi.pangaea.de/10.1594/PANGAEA.883104
Chapter
Full-text available
The main patterns of water and sediment transport at the Guadiana Estuary result primarily from the tide and its interaction with the river discharge and channel morphology (Box 1.1). The geomorphological characteristics of the estuary, including surficial sediment and bedform patterns, are presented in Section 1.2. Information about the tidal sign...
Conference Paper
Full-text available
A simplified version of the Inlet Reservoir Model is implemented at the Guadiana ebb delta to define efficient maintenance strategy of the entrance channel. The model is first applied typically to the outer shoal area, reproducing successfully the observed post-jetty volume evolution known from 16 bathymetric grids spanning 47 years. However, the v...
Conference Paper
Full-text available
Environmental monitoring stations providing high frequency data over a multiyear time frame are not common in estuaries. These systems are designed to record extended time-series at high frequency that are of great value for decision makers and the scientific community. However, the continuous acquisition of good quality data at estuaries is genera...
Article
The understanding of the sedimentary links between the beach and the continental shelf is crucial for the evaluation of the coastal sediment budget. However, the comprehension of this dynamics is still poorly understood owing greatly to the lack of direct sediment transport measurement at seasonal and longer time scales. This work aims at evaluatin...
Data
The datasets are described in: Garel E, Ferreira Ó, 2015. Multi-year high-frequency physical and environmental observations at the Guadiana Estuary. Earth System Science Data, 8(2), 567-586, doi: 10.5194/essdd-8-567-2015.
Article
Full-text available
High-frequency data collected continuously over a multiyear time frame are required for investigating the various agents that drive ecological and hydrodynamic processes in estuaries. Here, we present water quality and current in-situ observations from a fixed monitoring station operating from 2008 to 2014 in the lower Guadiana Estuary, southern Po...
Article
Full-text available
At the Gulf of Cadiz (GoC), poleward currents leaning along the coast alternate with coastal upwelling jets of opposite direction. Here the patterns of these coastal countercurrents (CCCs) are derived from ADCP data collected during 7 deployments at a single location on the inner shelf. The multiyear (2008-2014) time-series, constituting ~. 18. mon...
Conference Paper
Full-text available
Multiyear (2008-2014) ADCP data were collected during 7 deployments at a single location on the inner shelf of the Gulf of Cadiz. The time series (~18 months of hourly records) are used to characterise the patterns of coastal counter currents (CCCs) that alternate with upwelling jets of opposite (eastward) direction in this area. The observations i...
Article
Global change is affecting freshwater flow into estuarine nursery areas, with effects on fish larvae retention. Until now, related studies usually considered all early phases of fishes as passive drifters. However, the swimming behaviour of temperate fish larvae in these areas with strong tides and freshwater inflow is poorly described. The goal of...
Article
Full-text available
High-frequency data collected continuously over a multiyear time frame are required for investigating the various agents that drive ecological and hydrodynamic processes in estuaries. Here, we present water quality and current in-situ observations from a fixed monitoring station operating from 2008 to 2014 in the lower Guadiana Estuary, southern Po...
Data
These data were collected by a multi-parametric probe (temperature, pH, dissolved oxygen, turbidity, conductivity and chlorophyll-a) and a bottom-mounted ADP (near-bottom temperature, pressure and current velocity along the water column). The ADP data were recorded every 15 minutes from March 2008 to Jan 2011; Jan 2012 to Jan 2013; and March 2013...
Conference Paper
Full-text available
The undisturbed (pre-jetty) morphology of the Guadiana ebb-delta (Southern Portugal-Spain border) was characterised by a large sandbank (the O’Bril bank) located off the mouth and growing eastward over a broad swash platform (Garel et al., 2014). A pair of parallel jetties was built across this bank in 1974-76 to stabilise the inlet and facilitate...
Data
High-frequency data collected continuously over a multiyear time frame are required for investigating the various agents that drive ecological and hydrodynamic processes in estuaries. Here, we present water quality and current in-situ observations from a fixed monitoring station operating from 2008 to 2014 in the lower Guadiana Estuary, southern Po...
Article
Full-text available
The morphodynamic response of a mixed-energy ebb-tidal delta (Guadiana estuary, southern Portugal) and its down-drift barrier island (Canela Island) to channel relocation and stabilisation by jetties is examined using a series of sequential bathymetric maps and vertical aerial photographs spanning five decades. Morphological analysis indicates that...
Article
Full-text available
This research investigates the dynamics of the axial tidal flow and residual circulation at the lower Guadiana Estuary, south Portugal, a narrow mesotidal estuary with low freshwater inputs. Current data were collected near the deepest part of the channel for 21 months and across the channel during two (spring and neap) tidal cycles. Results indica...
Article
Full-text available
This paper deals with the performances of non-permanent environmental monitoring stations when recording at high-sampling interval (hour) over a long term (months, years) within estuarine waters. Information about data quality and system maintenance requirements are provided based on the experience gained with an autonomous station deployed during...
Article
Full-text available
The exchange (import, export) of sediment near the mouth of the Guadiana Estuary during periods of damregulated and non-regulated river flow are computed and compared. Bedload and suspended sediment transport rates were derived from Acoustic Doppler Profiler (ADP) measurements at a fixed station (∼2 years) and across the estuarine channel (3 tidal...
Article
Full-text available
Gravel pits created by anchor hopper dredging may affect regional sediment transport patterns by trapping sediments. In turn, this may cause -or enhance-erosion at the adjacent coastline. Reliable assessment of such impacts requires a good understanding of the hydro-sediment dynamic processes acting at dredged pits. This paper examines the processe...
Article
Although it is generally acknowledged that most multiple inlets are unstable and cannot coexist, there is evidence to suggest that such inlets can indeed be stable over decadal time scales. Multiple-inlet systems servicing a single embayment, in contrast to single-inlet systems, confer particular hydrodynamic characteristics such as the potential e...
Article
Full-text available
The short-term dynamics of a dredged tidal sandbank (the Kwinte Bank, southern North Sea) are examined, on the basis of field measurements and 1D sediment transport modelling. The field measurements include current data from shipborne Acoustic Doppler Current Profiler (ADCP) and from moorings (ADCP and electromagnetic S4), collected across the bank...
Article
Full-text available
Sand extraction activities on the Belgian Continental Shelf are regulated, in the sense that no major changes to the seabed should occur and natural regeneration of the banks is considered to balance the extraction rates. However, the centre of a tidal sandbank (Kwinte Bank), exploited intensively since the 1970's, is transformed now into a depress...
Article
Full-text available
The North Sea is, to an increasing degree, subject to human activities and interests; a particular example of a user function of this environment is sand extraction. In order to satisfy the demand for sand, tidal sandbanks in some sectors of the North Sea act as a source of sediment, this may lead to the creation of large-scale pits on these bedfor...
Article
Full-text available
This paper provides a brief review of regulations and procedures relevant to the authorization of marine aggregate (MA) operations in eight EU Member States. MA operations are affected by a multi-level legislative/regulatory regime, consisting of international conventions (e.g. the UNCLOS 1982, OSPAR, Helsinki, ICES, Barcelona and Espoo Conventions...
Article
Full-text available
A basic requirement for allowing marine aggregate (sand) extraction on the Belgian Continental Shelf (which takes place on sandbanks) is that it should not result in major environmental changes. However, a tidal sandbank (Kwinte Bank, Flemish Banks), exploited intensively since the 1970’s, has shown evidence of significant morphological changes wit...