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Natural and Anthropogenic Variations in the Large Shifting Dune in the Corrubedo Natural Park, NW Iberian Peninsula (1956-2017)

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This work analyzes the evolution of the large shifting dune included in the Corrubedo Natural Park from 1956 until the present day. The analysis was carried out using aerial images, orthophotographs, topographic surveys and LiDAR (Light Detection and Ranging) data. Variations were analyzed in terms of four different aspects: evolution of pathways in each period, changes in the position of the mobile dune front and the degree of vegetation cover, all between 1956 and 2017; and variations in elevation and volume of the dune system between 2001 and 2015. To analyze these aspects, geospatial and geostatistical techniques were employed, which revealed that the dune front had undergone two different phases: one until the 1980s, with a mean seaward advance of 32 m and another one between the 1980 s and 2017, when the front prograded to the continent, with an approximate mean advance of 82 m. Loss of volume, related to the expansion of the mobile dune towards the north, was confirmed in this sector. It is evident that these changes are closely linked to anthropic influence, due to sand extraction until the early 1990s and, more recently, due to an increase in the number of visitors to the Natural Park. The results obtained highlight the need to carry out detailed studies to understand the evolution of this system and to prevent further damage in the future. Moreover, based on these analyses, a strategy to improve coastal and environmental management in the Corrubedo Natural Park could be designed.
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sciences
Article
Natural and Anthropogenic Variations in the Large Shifting
Dune in the Corrubedo Natural Park, NW Iberian Peninsula
(1956–2017)
Augusto Pérez-Alberti 1, 2, * , Alejandro Gómez-Pazo 1,3 and X. L. Otero 1,2


Citation: Pérez-Alberti, A.; Gómez-
Pazo, A.; Otero, X.L. Natural and An-
thropogenic Variations in the Large
Shifting Dune in the Corrubedo Nat-
ural Park, NW Iberian Peninsula (1956–
2017). Appl. Sci. 2021,11, 34. http://
dx.doi.org/10.3390/app11010034
Received: 25 November 2020
Accepted: 21 December 2020
Published: 23 December 2020
Publisher’s Note: MDPI stays neu-
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Creative CommonsAttribution (CCBY)
license(https://creativecommons.org/
licenses/by/4.0/).
1CRETUS Institute, Universidade de Santiago de Compostela, 15782 Santiago de Compostela, Spain;
a.gomez@usc.es (A.G.-P.); xl.otero@usc.es (X.L.O.)
2Departamento de Edafoloxía e Química Agrícola, Facultade de Bioloxía, Campus Vida, Universidade de
Santiago de Compostela, Calle Lope Gómez de Marzoa, s/n, 15782 Santiago de Compostela, Spain
3Departamento de Xeografía, Facultade de Xeografía e Historia, Universidade de Santiago de Compostela,
15782 Santiago de Compostela, Spain
*Correspondence: augusto.perez@usc.es
Abstract:
This work analyzes the evolution of the large shifting dune included in the Corrubedo
Natural Park from 1956 until the present day. The analysis was carried out using aerial images,
orthophotographs, topographic surveys and LiDAR (Light Detection and Ranging) data. Variations
were analyzed in terms of four different aspects: evolution of pathways in each period, changes in
the position of the mobile dune front and the degree of vegetation cover, all between 1956 and 2017;
and variations in elevation and volume of the dune system between 2001 and 2015. To analyze these
aspects, geospatial and geostatistical techniques were employed, which revealed that the dune front
had undergone two different phases: one until the 1980s, with a mean seaward advance of 32 m
and another one between the 1980 s and 2017, when the front prograded to the continent, with an
approximate mean advance of 82 m. Loss of volume, related to the expansion of the mobile dune
towards the north, was confirmed in this sector. It is evident that these changes are closely linked
to anthropic influence, due to sand extraction until the early 1990s and, more recently, due to an
increase in the number of visitors to the Natural Park. The results obtained highlight the need to
carry out detailed studies to understand the evolution of this system and to prevent further damage
in the future. Moreover, based on these analyses, a strategy to improve coastal and environmental
management in the Corrubedo Natural Park could be designed.
Keywords: coastal dune; coastal evolution; LiDAR; Corrubedo; Galicia
1. Introduction
Several publications have analyzed coastal dune systems, both at a global level and
within Spain. Different authors have described the types of systems and their main
characteristics [
1
4
]. Other works have focused on the dynamics and the evolution of
these zones, particularly from a geomorphological point of view [
5
12
] but also paying
attention to anthropic influence in these systems (e.g., References [
13
16
]). In this case the
research focuses on an integrated analysis using different techniques in the large shifting
dune within the Corrubedo Natural Park. This dune is 900 m long and 300 m wide and
its maximum height is nearly 20 m. It is a singular formation in the Atlantic coast of the
Iberian Peninsula.
Sedimentary systems are rapidly evolving environments, a fact with major implica-
tions both for the population and for economic sectors such as tourism [
17
]. In this sense
and in relation to the potential impacts of global change, research about the evolution of
sedimentary systems has become a key issue both for researchers and for society in gen-
eral. The last few decades have seen an increase in the number of publications analyzing
their evolution from multiple perspectives [
18
20
]. These variations are associated with
Appl. Sci. 2021,11, 34. https://dx.doi.org/10.3390/app11010034 https://www.mdpi.com/journal/applsci
Appl. Sci. 2021,11, 34 2 of 17
technological advances, which have allowed researching this issue with a higher level of
detail and accuracy [2123].
The Corrubedo Natural Park is located in Galicia, a region in the NW Iberian Peninsula
characterized by a very intricate coastline, with numerous inlets and outlets along more
than 2100 km [
24
]. As the scale of analysis is expanded, the number of the different types
of units identified increases. Among these, it is worth highlighting beach-dune systems,
frequently associated with small lakes and marshlands, which constitute one of the most
vulnerable coastal environments, as well as one of the most sensitive to human impact [
25
].
The study area could be included within this category. Overall, the Galician coast has been
extensively analyzed from different perspectives in recent decades [2630].
The main objective of this study is to analyze the evolution of the Corrubedo large
shifting dune over a period of 60 years. This allows us to better understand their dynamics
and to prevent the evolution of the dune sector. It aims to expand on the knowledge
generated by previous analyses, such as pioneering studies by Vázquez Paz [
31
] and
Delgado Blanco [
32
], in which the authors addressed geomorphological units, as well as by
other research studies about the dune system [
33
], the beach rocks [
34
] and their evolution
or about sections closely located to our study area [
35
,
36
], which have pointed out the
influence of ancient topography and described the main characteristics of the system.
Corrubedo Natural Park as part of Nature 2000 network, the area occupied by the
dune appear in the Plan Director de la Red Natura 2000 de Galicia (PDRN) (Decree 37/2014,
Xunta de Galicia) with the habitat code 2120, as principal habitat and other dune habitats
associated. This zone and the nearby habitats explain the importance of analyze Corrubedo
system to improve the management of this area avoid possible problems related to the
global change.
In line with the aforementioned, this work also reflects the importance of key factors,
both of natural and human origin, for the existing variations in Corrubedo in order to
measure the relevance of these factors for its past dynamics and their role in the present
and future of Corrubedo. This is a key element since this study aims to lay the foundations
for a more efficient management of the Corrubedo Natural Park.
2. Environmental Setting
The Corrubedo dune complex is located in the western edge of the O Barbanza penin-
sula (Figure 1), which separates the ria of Muros-Noia, in the north, from the ria of Arousa,
in the south. It is a large sedimentary inlet delimited by low granitic cliffs and enclosed in
its inner end by low elevations that do not exceed 300 m. Corrubedo is a singular system
with a large sedimentary beach over 4 km in length and with an associated dune field
that encloses a small lagoon and a marshland area with several meandering channels. The
high environmental interest of this sector has led to its inclusion within the Natura 2000
network and to the creation of the Natural Park named Complexo dunar de Corrubedo e lagoas
de Carregal e Vixán(hereinafter referred to as Corrubedo Natural Park) in 1992.
Appl. Sci. 2021,11, 34 3 of 17
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Figure 1. Location map of Natural Park of Corrubedo. 9 (a) represent the area in European context;
(b) shows Corrubedo in west Galicia area; and (c) shows the large dune and the analysis zona in
detail with the polygons used for analyzing the elevation differences (Geomorphic Change Detec-
tion (GCD) zone); the area to analyzed the pathways (Complete area) and the topographic profiles
position above PNOA 2017 orthophotography [37].
The Corrubedo Natural Park has a humid-oceanic climate, with an average yearly
rainfall of 1000–1200 mm and mild temperatures all year round (18.5° in summer and 9.5°
in winter) [38]. Winds vary in intensity and direction depending on the season. S and SW
winds prevail in autumn and winter, in association with low pressures originated by the
Polar front, which causes the majority of marine storms in this area. NW winds prevail
during the summer, in association with anticyclones; winds during this season are persis-
tent but with lower intensity than winter winds, with an average speed of 14 km/h.
Wave data were obtained from point no. 3010013 of the SIMAR network (Puertos del
Estado [39]), located 4 km offshore to the south of the study area. The dominant wave
direction is the West, which is the main orientation of the highest waves (Figure 2a), which
occur during the winter months and frequently exceed 6 m in height (Figure 2c). Figure
2b shows the days with wave heights above Hs.95 (3.78 m), with a total of 280 days (4.28%
of the analyzed period). This value evidences the importance of marine storms in this area,
which constitute an essential erosive agent for the evolution of sedimentary systems, with
values over 95%.
Figure 1.
Location map of Natural Park of Corrubedo. 9 (
a
) represent the area in European context;
(
b
) shows Corrubedo in west Galicia area; and (
c
) shows the large dune and the analysis zona in detail
with the polygons used for analyzing the elevation differences (Geomorphic Change Detection (GCD)
zone); the area to analyzed the pathways (Complete area) and the topographic profiles position above
PNOA 2017 orthophotography [37].
The Corrubedo Natural Park has a humid-oceanic climate, with an average yearly
rainfall of 1000–1200 mm and mild temperatures all year round (18.5
in summer and 9.5
in winter) [
38
]. Winds vary in intensity and direction depending on the season. S and
SW winds prevail in autumn and winter, in association with low pressures originated
by the Polar front, which causes the majority of marine storms in this area. NW winds
prevail during the summer, in association with anticyclones; winds during this season are
persistent but with lower intensity than winter winds, with an average speed of 14 km/h.
Wave data were obtained from point no. 3010013 of the SIMAR network (Puertos del
Estado [
39
]), located 4 km offshore to the south of the study area. The dominant wave
direction is the West, which is the main orientation of the highest waves (Figure 2a), which
occur during the winter months and frequently exceed 6 m in height (Figure 2c). Figure 2b
shows the days with wave heights above Hs.95 (3.78 m), with a total of 280 days (4.28%
of the analyzed period). This value evidences the importance of marine storms in this
area, which constitute an essential erosive agent for the evolution of sedimentary systems,
with values over 95%.
In the Corrubedo system, several geodynamic units can be distinguished between the
upper beach and the continent, ranging from incipient dunes, whose genesis and evolution
is related to hydrodynamic agents, to ancient dunes, which are fixed by vegetation. Vázquez
Paz [
31
] carried out the first detailed cartography of these units, characterized their dynamic
relations and analyzed environmental factors that influenced their recent evolution. In
this sense and following the classification established by Paskoff [
14
], there is a sector of
variable width composed by primary dunes, which receive sedimentary contributions and
where two different categories can be distinguished: embryonic dunes, formed in the upper
beach from berms or deposited material at the front of dune microcliffs and colonized by
pioneer species such as Agropyrum junceiforme or Cakile marítima; and foredunes, which are
sub-elliptic in plain view and generally follow a SW–NW direction, with Ammophila arenaria
as the dominant species.
Appl. Sci. 2021,11, 34 4 of 17
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Figure 2. Wave data about SIMAR point 3010013 between January 2000 and December 2017. (a)
Wave rose with direction and height in percentage; (b) Direction and height of storm days defined
as days with mean Hs > 0.95, in this period the Hs.95 = 3.78 m; (c) Timeseries with mean daily Hs.
Marks indicate the aerial images and orthophotographs date acquisition (starts with letter P and
the entire code appear in Table 1) and the moment of topographic or LiDAR (Light Detection and
Ranging) surveys (starts with letter T and the entire code appear in Table 2). Data from: Meteogali-
cia [38] and IGN (Instituto Geográfico Nacional) [37].
In the Corrubedo system, several geodynamic units can be distinguished between
the upper beach and the continent, ranging from incipient dunes, whose genesis and evo-
lution is related to hydrodynamic agents, to ancient dunes, which are fixed by vegetation.
Vázquez Paz [31] carried out the first detailed cartography of these units, characterized
their dynamic relations and analyzed environmental factors that influenced their recent
evolution. In this sense and following the classification established by Paskoff [14], there
is a sector of variable width composed by primary dunes, which receive sedimentary con-
tributions and where two different categories can be distinguished: embryonic dunes,
formed in the upper beach from berms or deposited material at the front of dune micro-
cliffs and colonized by pioneer species such as Agropyrum junceiforme or Cakile marítima;
and foredunes, which are sub-elliptic in plain view and generally follow a SW–NW direc-
tion, with Ammophila arenaria as the dominant species.
The group of secondary dunes includes a wide stripe of hummock dunes with 2–4 m
in height. This geometry can result from crosswinds from the NW and SW, together with
the protecting effect of vegetation. Towards the shore, the degree of vegetation coverage
progressively increases, except in the vicinity of the mobile dune, where W winds carry
sediments to this area.
On the back is the mobile dune, the main focus of this study, as well as a large sector
of ancient dunes, with lower height and smoother shapes and fully colonized by vegeta-
tion. In some cases, these deposits can be reactivated due to high-intensity winds, and,
particularly in the northern area, they are being covered due to the advance of the mobile
dune.
The origin of the actual dune system could respond to a dune formation model dur-
ing a marine regression phase [1]. According to faunistic and sedimentological results car-
ried out by Margalef [40] in the ria of Vigo, the consequences of the last deglaciation first
manifested in the Atlantic coast of Galicia around 8500–8000 years BP. Nevertheless, it
was not until the maximum Flandrian transgressive phases that the sea retreated to levels
slightly below the current ones. Accretion rates and wave, current and wind action in an
Figure 2.
Wave data about SIMAR point 3010013 between January 2000 and December 2017. (
a
) Wave
rose with direction and height in percentage; (
b
) Direction and height of storm days defined as days
with mean Hs > 0.95, in this period the Hs
0.95
= 3.78 m; (
c
) Timeseries with mean daily Hs. Marks
indicate the aerial images and orthophotographs date acquisition (starts with letter P and the entire
code appear in Table 1) and the moment of topographic or LiDAR (Light Detection and Ranging)
surveys (starts with letter T and the entire code appear in Table 2). Data from: Meteogalicia [
38
] and
IGN (Instituto Geográfico Nacional) [37].
The group of secondary dunes includes a wide stripe of hummock dunes with 2–4 m
in height. This geometry can result from crosswinds from the NW and SW, together with
the protecting effect of vegetation. Towards the shore, the degree of vegetation coverage
progressively increases, except in the vicinity of the mobile dune, where W winds carry
sediments to this area.
On the back is the mobile dune, the main focus of this study, as well as a large sector of
ancient dunes, with lower height and smoother shapes and fully colonized by vegetation. In
some cases, these deposits can be reactivated due to high-intensity winds, and, particularly
in the northern area, they are being covered due to the advance of the mobile dune.
The origin of the actual dune system could respond to a dune formation model
during a marine regression phase [
1
]. According to faunistic and sedimentological results
carried out by Margalef [
40
] in the ria of Vigo, the consequences of the last deglaciation
first manifested in the Atlantic coast of Galicia around 8500–8000 years BP. Nevertheless,
it was not until the maximum Flandrian transgressive phases that the sea retreated to
levels slightly below the current ones. Accretion rates and wave, current and wind action
in an environment with an important sedimentary stock enabled coastal sedimentary
accumulations that allowed the beach to close, forming a lagoon. For 6000–6500 years BP,
the processes of dune genesis and progressive closure of the lagoon occurred synchronically,
with an expansion of the sedimentary barrier taking place around 5000 years BP [35].
The singular presence of a large transversal mobile dune (20 m high at its crest in 2000)
occupying a secondary position in relation to the beach has been scarcely studied, particu-
larly taking into account that coastal areas with similar climatic conditions, orientation and
sedimentary stock are common throughout the NW Iberian Peninsula, yet accumulations
of this magnitude have not formed in any of them. In the opinion of Vázquez Paz [
31
],
its origin could be related to the existence of an orographic obstacle that would lead to
sand accumulation. The dune formation process could have started during a phase of
climatic transition, when sedimentary stock in the system was abundant due to a slight
Appl. Sci. 2021,11, 34 5 of 17
sea level rise that, as pointed out by Klijn [
41
], was also associated with an increase in
the frequency and persistence of storms. During the Little Ice Age, wind intensity and
frequency was significantly higher than in the present [
41
]. Due to this, accretion processes
and the shoreward advance of the dune intensified. This fact generated the progressive
expansion of the parallel corridor. It was a longitudinal dune created by SW fluxes and
reshaped by NW winds.
In addition to natural factors, it is necessary to analyze human influence to understand
the dynamics that explain the evolution of the system. Before the designation of this area
as a Natural Park in 1992, different harmful activities had been carried out for decades
in and around the large shifting dune, such as sand extraction from the dune and access
of pedestrians and heavy vehicles to the dune system. These activities were of great
importance in the decades of 1960 and 1970, in association with the boom of the construction
industry. Sand extraction would not stop until the creation of the Natural Park, which in
turn led to a substantial increase in the number of visitors. It is worth pointing out that the
increased influx of visitors and the different structures created for tourism contributed to
the alteration of the dune system. Among them, it is worth mentioning the construction of
a wooden walkway over the mobile dune system in 2000, later removed in 2006 [33,42].
3. Materials and Methods
Given that this study covers a period of six decades, the consequent changes in
available materials and research techniques have conditioned the development of this
research. Due to this, three different and complementary data sources have been used.
The first source used were aerial photographs and orthophotographs from the IGN
(Instituto Geográfico Nacional) [
37
] from years 1956, 1983, 1989, 2002, 2004, 2008, 2010,
2014 and 2017. Those from the first two study years were black and white aerial pho-
tographs, whereas those from years 1989–2004 were color aerial photographs and those
from 2008 onwards were orthophotographs (Table 1). Based on them, variations in the
different environments located in Corrubedo were analyzed.
Table 1. Date of the aerial images and orthophotographs used.
Code Date Scale Program
- 1956 1/32,000 American Flight
- 1983 1/30,000 National Flight
- 1989 1/5000 Coastal Flight
P1 08/01/2002 1/30,000 SIGPAC 1
P2 09/21/2004 1/30,000 PNOA 2
P3 08/05/2008 1/30,000 PNOA 2
P4 07/30/2010 1/20,000 PNOA 2
P5 07/10/2014 1/20,000 PNOA 2
P6 06/17/2017 1/20,000 PNOA 2
1
Sistema de Información Geográfica de Parcelas Agrícolas.
2
Plan Nacional de Ortofotografía Aérea.
The second data source was the topographic survey performed in this area in Febru-
ary 2001. This survey had a planimetric accuracy around 5 cm and an altimetric accuracy
around 8 cm for recorded points and 20 cm for interpolated points. All data were obtained
either from the main station or from auxiliary stations, always avoiding linking different
auxiliary stations together.
Moreover, this research used LiDAR data [
37
] from years 2010 and 2015. This information
had a resolution of 0.5 points/m
2
and was obtained from the IGN. Additionally, data from
our 2008 LiDAR flight, with a resolution of 0.3 points/m2, were employed (Table 2).
Appl. Sci. 2021,11, 34 6 of 17
Table 2. Date and type of surface elevation surveys.
Code Date Type Source
T1 02/20/2001 Topographic survey Own data
T2 07/07/2008 LiDAR Own data
T3 04/07/2010 LiDAR IGN
T4 22/07/2015 LiDAR IGN
Different methodologies and software were used depending on the type of analysis.
ArcGIS 10.5 (license USC) was employed for geospatial processing and R software [
43
] was
used for statistical analysis and for the majority of graphs.
To analyze variations in the mobile dune front, it was mapped for each date for which
images were available. These lines were used as a proxy to quantify variations through
DSAS (Digital Shoreline Analysis System) [
44
], whose validity was further corroborated by
multiple studies about coastline evolution [
26
,
45
,
46
]. For this analysis, transects were gener-
ated every 5 m and variations were calculated in three different periods: first, between 1956
and 2017, in order to determine the changes throughout the whole study period; a second
timeframe between 1989 and 2017, to determine the differences between the present and
a moment when the configuration of the sector was already similar to the current one;
and, finally, variations between 2004 and 2017 were calculated to understand the recent
evolution and to estimate differences with a higher accuracy.
Variations in pathways were analyzed based on the images listed in Table 1. In this
case, the detectable paths were first drawn and their length was then calculated within a
134.9 ha area around the mobile dune (Figure 1, orange line). This analysis aims to highlight
the importance of human activities in this space since 1956.
As for plant coverage, the edges of the plant-covered areas were mapped for all years
with available images (Table 1). Based on the generated polygons, the area covered by
vegetation within the area delimited in Figure 1was estimated and surface variations
between dates were then calculated.
For the analysis of LiDAR data (2008–2015), Geomorphic Change Detection (GCD)
implemented in ArcGIS [
47
] was used. In this case, a Limit of Detection (LoD) of 0.5 m,
related to RMSE values of data acquisition, was estimated for the analysis of LiDAR
data from 2008, while for data from 2010 to 2015, the LoD was established in 0.2 m,
following specifications by the IGN [
37
]. This limit sets the minimum threshold for a
variation to be considered as an actual change, therefore removing possible errors related
to analysis uncertainty. This information was processed following the same methodology
as previously described [
26
] and the area around the mobile dune was selected for research,
with an overlapping area of 48.82 ha among all the different dates (Figure 1). In this area,
the Difference of Digital Elevation Models (DoD) was calculated to estimate variations
among the different years, both in terms of elevation and volumetrics.
In addition to this analysis of variations, topographic surveys were created, using data
from 2008 to 2015 for a larger area and data from 2001, obtained from topographic surveys,
for a smaller area focused on the dune crest. The aim of this process was to compare the
2001 profiles with the generated Digital Models (DM) based on the LiDAR data and to
obtain a clear image of the variations in the crest of the mobile dune.
As a general approach, Figure 3represents the workflow of this study. On the left
side, the techniques and materials used are represented in green and, on the right side,
the factors affecting changes in the system are represented in blue. These two elements
were combined to attain the main purpose of this work: to determine the variations in the
Corrubedo system since 1956 in order to improve the management of this area.
Appl. Sci. 2021,11, 34 7 of 17
Appl. Sci. 2021, 11, x FOR PEER REVIEW 7 of 19
As a general approach, Figure 3 represents the workflow of this study. On the left
side, the techniques and materials used are represented in green and, on the right side,
the factors affecting changes in the system are represented in blue. These two elements
were combined to attain the main purpose of this work: to determine the variations in the
Corrubedo system since 1956 in order to improve the management of this area.
Figure 3. Flowchart with the materials and steps of variation analysis and the main elements that
could be influencing in the analyzed sector behavior.
4. Results
4.1. Pathway Analysis
The analysis of variations in pathways around the mobile dune showed a clear in-
crease since 1956, reaching their greatest length in 2002, with 11,201 m. These values re-
mained above 7000 m until 2010, at which point their length decreased down to 4986 m in
2017 (Table 3).
Table 3. Pathway length (m) in each analyzed image.
Date Length (m)
1956 1312
1983 8560
1989 11,132
2002 11,201
2004 9920
2008 7917
2010 7536
2014 5817
2017 4986
This evolution was clearly related to an increase in the area covered by vegetation in
Corrubedo, almost non-existent in 1956, although the fact that only black and white im-
ages were available for this date made it more difficult to map. As shown in Figure 4, plant
coverage has been considerably higher from 2000 onwards than in previous decades.
These images also illustrate important changes in pathway distribution, which have re-
duced in recent years and moved southward from the mobile dune, towards the middle
section of the beach. This could be related to protection and control measures.
It is also worth noting that the aerial images from 2002 and 2004 (Figure 4) showed a
pathway across the large shifting dune. This element corresponds to the installation of a
wooden walkway in this area, later removed, although some signs of its presence still
remain in later images.
Figure 3.
Flowchart with the materials and steps of variation analysis and the main elements that
could be influencing in the analyzed sector behavior.
4. Results
4.1. Pathway Analysis
The analysis of variations in pathways around the mobile dune showed a clear increase
since 1956, reaching their greatest length in 2002, with 11,201 m. These values remained
above 7000 m until 2010, at which point their length decreased down to 4986 m in 2017
(Table 3).
Table 3. Pathway length (m) in each analyzed image.
Date Length (m)
1956 1312
1983 8560
1989 11,132
2002 11,201
2004 9920
2008 7917
2010 7536
2014 5817
2017 4986
This evolution was clearly related to an increase in the area covered by vegetation in
Corrubedo, almost non-existent in 1956, although the fact that only black and white images
were available for this date made it more difficult to map. As shown in Figure 4, plant cov-
erage has been considerably higher from 2000 onwards than in previous decades. These
images also illustrate important changes in pathway distribution, which have reduced in
recent years and moved southward from the mobile dune, towards the middle section of
the beach. This could be related to protection and control measures.
It is also worth noting that the aerial images from 2002 and 2004 (Figure 4) showed
a pathway across the large shifting dune. This element corresponds to the installation of
a wooden walkway in this area, later removed, although some signs of its presence still
remain in later images.
Appl. Sci. 2021,11, 34 8 of 17
Appl. Sci. 2021, 11, x FOR PEER REVIEW 8 of 19
Figure 4. Evolution of pathways in the large shifting dune sector since 1956 to 2017. The pathways
(red lines) are on the aerial images and orthophotographs of each data where one can observe the
variations in dune extension (black dashed line). In the case of 1956 image, the dune extension is
not marked for the difficult to define their boundaries in that image.
4.2. Variations in the Dune Front between 1956 and 2017
The analysis of the mobile dune front provided an opportunity to clearly identify its
advance towards the north, occupying an area that had been previously covered by dune
vegetation at least since the 1980s. Related to this process and to the analyzed DSAS pro-
cesses are major differences in its behavior between the period from 1956 to the 1980s, on
one hand and the subsequent period, on the other. For the overall period, an average pro-
gradation of 32.37 m offshore took place but this dynamic was largely due to the expan-
sion of the area covered by vegetation with respect to 1956, when plant coverage in this
sector was much lower and sand dominated the study area (Figure 4). Conversely, ana-
lyzing variations since 1989, the front of the large sifting dune could be observed to pro-
gress 81 m towards the shore. This advance was also clearly noticeable in recent years,
exceeding 30 m since 2004 (Figure 5).
Figure 5. (a) represents the front dune line in each analyzed year and (b) shows the variations of these fronts between 1956
and 2017 and between 1989 and 2017. Positive values indicated an advance to seaward while negative values indicate a
variation to landward.
Figure 4.
Evolution of pathways in the large shifting dune sector since 1956 to 2017. The pathways (red
lines) are on the aerial images and orthophotographs of each data where one can observe the variations
in dune extension (black dashed line). In the case of 1956 image, the dune extension is not marked for
the difficult to define their boundaries in that image.
4.2. Variations in the Dune Front between 1956 and 2017
The analysis of the mobile dune front provided an opportunity to clearly identify
its advance towards the north, occupying an area that had been previously covered by
dune vegetation at least since the 1980s. Related to this process and to the analyzed DSAS
processes are major differences in its behavior between the period from 1956 to the 1980s,
on one hand and the subsequent period, on the other. For the overall period, an average
progradation of 32.37 m offshore took place but this dynamic was largely due to the
expansion of the area covered by vegetation with respect to 1956, when plant coverage
in this sector was much lower and sand dominated the study area (Figure 4). Conversely,
analyzing variations since 1989, the front of the large sifting dune could be observed to
progress 81 m towards the shore. This advance was also clearly noticeable in recent years,
exceeding 30 m since 2004 (Figure 5).
Appl. Sci. 2021, 11, x FOR PEER REVIEW 8 of 19
Figure 4. Evolution of pathways in the large shifting dune sector since 1956 to 2017. The pathways
(red lines) are on the aerial images and orthophotographs of each data where one can observe the
variations in dune extension (black dashed line). In the case of 1956 image, the dune extension is
not marked for the difficult to define their boundaries in that image.
4.2. Variations in the Dune Front between 1956 and 2017
The analysis of the mobile dune front provided an opportunity to clearly identify its
advance towards the north, occupying an area that had been previously covered by dune
vegetation at least since the 1980s. Related to this process and to the analyzed DSAS pro-
cesses are major differences in its behavior between the period from 1956 to the 1980s, on
one hand and the subsequent period, on the other. For the overall period, an average pro-
gradation of 32.37 m offshore took place but this dynamic was largely due to the expan-
sion of the area covered by vegetation with respect to 1956, when plant coverage in this
sector was much lower and sand dominated the study area (Figure 4). Conversely, ana-
lyzing variations since 1989, the front of the large sifting dune could be observed to pro-
gress 81 m towards the shore. This advance was also clearly noticeable in recent years,
exceeding 30 m since 2004 (Figure 5).
Figure 5. (a) represents the front dune line in each analyzed year and (b) shows the variations of these fronts between 1956
and 2017 and between 1989 and 2017. Positive values indicated an advance to seaward while negative values indicate a
variation to landward.
Figure 5.
(
a
) represents the front dune line in each analyzed year and (
b
) shows the variations of these fronts between 1956
and 2017 and between 1989 and 2017. Positive values indicated an advance to seaward while negative values indicate a
variation to landward.
Appl. Sci. 2021,11, 34 9 of 17
4.3. Variations in Vegetation Coverage
Vegetation coverage in Corrubedo also varied greatly over the analyzed period
(Table 4),
from 33 ha in 1956 to a maximum value of 93.9 ha in 2017. This increase in
plant coverage was not linear: this area has remained above 80 ha since 2002, unlike in
previous decades, according to the images used (Figure 6). This increase in vegetation
coverage in dune zones has also been observed both in other areas of Galicia [
48
] and at a
global level [
49
]. This could be related to a decrease in sedimentary activity linked to an
increase in temperature and nutrients along with a decrease in winds, which enables the
expansion of vegetation in these sectors [49].
Table 4. Vegetation surface (ha) in each analyzed image.
Date Surface (ha)
1956 33.0
1983 67.0
1989 66.2
2002 84.9
2004 91.4
2008 92.9
2010 89.7
2014 88.1
2017 93.9
Appl. Sci. 2021, 11, x FOR PEER REVIEW 10 of 19
Figure 6. Evolution of vegetation coverage since 1956 to 2017. The light green polygons represent
the vegetation on the aerial images and orthophotographs of each data.
4.4. Variations in Elevation Since 2001
Using data from the topographic surveys from 2001, from LiDAR (2008, 2010 and
2015) and from field visits during the last 20 years, an overall shoreward progradation of
the dune could be observed, as already mentioned for the front dune. In this sense, a de-
crease in maximum elevation could be observed, with emerging evidence that the sedi-
ments are spreading northward, resulting in a decrease both in dune slope and in crest
area. This advance leads to the fossilization of older plant-covered dune levels in some
sectors (especially on the north side). Another effect was the progressive extension of the
interdune corridor following an NNE-SSW direction, parallel to the dune crest, between
it and the first level of plant-covered dunes located close to the beach (Figures 7 and 8).
Figure 7. Topographic profiles in dune mobile sector between 2008 and 2015. The position of these profiles appears in
Figure 1c in black color.
As shown in Figure 7, a decrease in dune elevation occurred during the 2008–2015
period, especially in the crest. While in 2001 the maximum elevation was 21 m, this eleva-
tion decreased to 20.31 m in 2008, 19.59 m in 2010 and 18.51 in 2015. These modifications
Figure 6.
Evolution of vegetation coverage since 1956 to 2017. The light green polygons represent the
vegetation on the aerial images and orthophotographs of each data. The symbol (?) in this part of the
Figure indicated that in that moment (1956) was not possible identify the large dune extension and
their boundaries.
Additionally, it is worth highlighting that the accuracy of the definition of vegetation
coverage based on older aerial images was lower, because coverage estimations always
have a great uncertainty, especially in the case of the American flight (1956), where image
quality complicates the delimitation of both the dune and the plant-covered area. In relation
to the images, it is necessary to emphasize that the cartography based on images taken in
different seasons, with the area having experienced different meteorological conditions in
Appl. Sci. 2021,11, 34 10 of 17
the months prior to image capture, can also lead to variations in the estimations due to the
sand temporarily covering plants and to the seasonal behavior of some plant species.
Notwithstanding the foregoing, there has been a clear increase in plant coverage in
recent years, which is perfectly consistent with the conclusions reached by other research
studies [26,49].
4.4. Variations in Elevation Since 2001
Using data from the topographic surveys from 2001, from LiDAR (2008, 2010 and
2015) and from field visits during the last 20 years, an overall shoreward progradation
of the dune could be observed, as already mentioned for the front dune. In this sense,
a decrease in maximum elevation could be observed, with emerging evidence that the
sediments are spreading northward, resulting in a decrease both in dune slope and in crest
area. This advance leads to the fossilization of older plant-covered dune levels in some
sectors (especially on the north side). Another effect was the progressive extension of the
interdune corridor following an NNE-SSW direction, parallel to the dune crest, between it
and the first level of plant-covered dunes located close to the beach (Figures 7and 8).
Figure 7.
Topographic profiles in dune mobile sector between 2008 and 2015. The position of these profiles appears in
Figure 1c in black color.
Appl. Sci. 2021, 11, x FOR PEER REVIEW 11 of 19
were more relevant in the central zone of the mobile dune (Corrubedo P2 and P3 in Figure
7), which corresponds to the highest sector and the one with the greatest amount of sedi-
ments.
To analyze variations since 2001, the analysis focused on the peak sector of the dune
system, about which abundant information is available. As shown in Figure 8, elevation
decreased across all profiles. This fact is related to the erosion of the seaward flank and
shoreward dune progradation.
Figure 8. Topographic profiles in the crest of dune mobile sector between 2001 and 2015. The position of these profiles
appears in Figure 1c in red color.
The analysis of LiDAR data from 2008 onwards showed a general decrease in eleva-
tion in the whole analyzed sector. The overall results showed that erosion was the domi-
nant process in the seaward dune flank. In the inner flank, large accumulations of sand
transported to the crest by deflation channels were formed, leading to movements caused
by gravity that helped slow the progression of the dune towards the shore (Figure 9). In
Figure 9, a clear increase in elevation related to the advance of the mobile dune is shown
in green. This dynamic appeared in the system in the 1980s.
Figure 8.
Topographic profiles in the crest of dune mobile sector between 2001 and 2015. The position of these profiles
appears in Figure 1c in red color.
Appl. Sci. 2021,11, 34 11 of 17
As shown in Figure 7, a decrease in dune elevation occurred during the 2008–2015 pe-
riod, especially in the crest. While in 2001 the maximum elevation was 21 m, this elevation
decreased to 20.31 m in 2008, 19.59 m in 2010 and 18.51 in 2015. These modifications were
more relevant in the central zone of the mobile dune (Corrubedo P2 and P3 in Figure 7),
which corresponds to the highest sector and the one with the greatest amount of sediments.
To analyze variations since 2001, the analysis focused on the peak sector of the dune
system, about which abundant information is available. As shown in Figure 8, elevation de-
creased across all profiles. This fact is related to the erosion of the seaward flank and
shoreward dune progradation.
The analysis of LiDAR data from 2008 onwards showed a general decrease in elevation
in the whole analyzed sector. The overall results showed that erosion was the dominant pro-
cess in the seaward dune flank. In the inner flank, large accumulations of sand transported
to the crest by deflation channels were formed, leading to movements caused by gravity
that helped slow the progression of the dune towards the shore
(Figure 9).
In Figure 9,
a clear increase in elevation related to the advance of the mobile dune is shown in green.
This dynamic appeared in the system in the 1980s.
Appl. Sci. 2021, 11, x FOR PEER REVIEW 12 of 19
Figure 9. Evolution of surface elevation in large shifting dune sector. (a) Difference of Digital Elevation Models (DoD)
between 2008 and 2010; (b) DoD between 2010 and 2015; and (c) DoD between 2008 and 2015.
Between 2008 and 2015, a 0.55 m decrease in average elevation could be observed.
A 74.8% proportion of the area experienced variations above the LoD (0.5 m for this pe-
riod) and 83% of this area experienced a decrease in elevation, resulting in a volume loss
of 269,481 m3. In the partial analysis for the period between 2008 and 2010, the area that
experienced variations was 32% and elevation decreased in 80% of this area, resulting in
a net volume loss of 99,124 m3. The net variation in elevation was 0.2 m. Finally, in the
2010–2015 period, a similar decrease in elevation took place, with an average decrease of
0.23 m, although the area that experienced changes above the LoD increased up to 70.9%,
with 75% of the area experiencing loss. The net balance of volumetric change in this case
was 110,317 m3.
5. Discussion
Compared with other sectors of the Iberian coast, the Corrubedo zone shows lower
levels of environmental degradation. However, this sector has not been spared the effects
of certain human activities that damage, sometimes irreversibly, their geomorphological
and, consequently, their ecological and landscape balance [25].
One of the most relevant anthropic elements in Corrubedo was sand extraction for
the construction industry. This practice led to a great reduction in dune volume, which is
very difficult to quantify; at the same time, the loss of plant coverage reactivated erosion
processes [41,50]. This illustrates how anthropic activities can contribute to modify natural
dynamics. According to the available information, the designation of the Natural Park
took place at a time when sediment extraction seemed to be generalized in this area, alt-
hough this practice has been prohibited in Spain since the approval of a Coastal Regula-
tion Law in the 1980s. The areas that were most affected by this activity were those easily
accessed, particularly in the northeastern section and in the vicinity of the estuary, where
the effects of this activity are still observable in the presence of ponds.
The legal protection applied to Corrubedo led to an improvement from the environ-
mental point of view, since it reduced the most harmful activities in this area. Neverthe-
less, there are still some environmental conservation issues related to the number of visi-
tors and their influence on the ecosystems. The pathways generated during the late 1990s
could clearly be observed in some delicate and singular sectors such as the mobile dune
Figure 9.
Evolution of surface elevation in large shifting dune sector. (
a
) Difference of Digital Elevation Models (DoD)
between 2008 and 2010; (b) DoD between 2010 and 2015; and (c) DoD between 2008 and 2015.
Between 2008 and 2015, a
0.55 m decrease in average elevation could be observed.
A 74.8% proportion of the area experienced variations above the LoD (0.5 m for this period)
and 83% of this area experienced a decrease in elevation, resulting in a volume loss of
269,481 m
3
. In the partial analysis for the period between 2008 and 2010, the area that
experienced variations was 32% and elevation decreased in 80% of this area, resulting in a
net volume loss of 99,124 m
3
. The net variation in elevation was
0.2 m. Finally, in the
2010–2015 period, a similar decrease in elevation took place, with an average decrease of
0.23 m, although the area that experienced changes above the LoD increased up to 70.9%,
with 75% of the area experiencing loss. The net balance of volumetric change in this case
was 110,317 m3.
Appl. Sci. 2021,11, 34 12 of 17
5. Discussion
Compared with other sectors of the Iberian coast, the Corrubedo zone shows lower
levels of environmental degradation. However, this sector has not been spared the effects
of certain human activities that damage, sometimes irreversibly, their geomorphological
and, consequently, their ecological and landscape balance [25].
One of the most relevant anthropic elements in Corrubedo was sand extraction for
the construction industry. This practice led to a great reduction in dune volume, which is
very difficult to quantify; at the same time, the loss of plant coverage reactivated erosion
processes [
41
,
50
]. This illustrates how anthropic activities can contribute to modify natural
dynamics. According to the available information, the designation of the Natural Park took
place at a time when sediment extraction seemed to be generalized in this area, although this
practice has been prohibited in Spain since the approval of a Coastal Regulation Law in
the 1980s. The areas that were most affected by this activity were those easily accessed,
particularly in the northeastern section and in the vicinity of the estuary, where the effects
of this activity are still observable in the presence of ponds.
The legal protection applied to Corrubedo led to an improvement from the environ-
mental point of view, since it reduced the most harmful activities in this area. Nevertheless,
there are still some environmental conservation issues related to the number of visitors and
their influence on the ecosystems. The pathways generated during the late 1990s could
clearly be observed in some delicate and singular sectors such as the mobile dune (Figure 4).
These events decreased with the imposition of fines to any person trespassing the security
boundaries and accessing the mobile dune, although nowadays footprints in the dune can
often be observed.
5.1. Installation of a Walway over the Mobile Dune
One of the variations related to the anthropic activity analyzed in this sector was the
installation of a wooden walkway over the mobile dune in early 2000 [
33
,
42
]. This structure
crossed the dune at the bottom of a deflation corridor in its southern sector, close to the
estuary, which was one of the main sediment sources. A preliminary analysis showed
that the installation of this walkway, composed of 15 cm wide crosspieces, caused changes
at a small scale. Although the structure was flexible, its location interrupted the path of
sediments transported by saltation or rolling. When the wind blew in an oblique direction,
one side of the walkway acted as an accumulation zone (oriental sector), while on the
opposite side, a centimetric scarp was originated and became the starter to a large-scale
erosion spot. This fact led to the systematic covering of the structure in some parts, a clear
sign of the importance of eolian transport in this area, where sediments were channeled to
the center of the system.
It is evident that the installation of such structure caused a major perturbation in sand
mobilization and, consequently, in the dynamic evolution of the mobile dune for years. Its
installation also entailed an increase in the accessibility to the dune crest sector, enhancing
its attractive as a slide (Figure 10).
In 2006, analyzing the different morphological units in the Natural Park following
the removal of the wooden walkway, a certain degree of restoration of a natural dynamic
could be observed in this sector, with the appearance of several ripples (Technical report,
unpublished). Other fact worth highlighting is the increasingly natural progradation front.
Even in August, the month with the highest influx of visitors, virtually no footprints could
be observed on the slope, which could be partly related to the stricter surveillance in
this sector.
Appl. Sci. 2021,11, 34 13 of 17
Appl. Sci. 2021, 11, x FOR PEER REVIEW 14 of 19
Figure 10. Evolution of large shifting dune sector in different moments. (a) shows the dune sector
in 1992; (b) shows the walkway in early 2000; (c) shows the walkway in 2020 cover in part for the
dune evolution; (d) shows visitants in the walkway across the dune in 2002; (e) reveals the ripples
in the dune zone and the new walkway position, without the across dune section in 2006; and (f)
shows the state of large shifting dune in the sector close to the walkway in 2012, that clearly repre-
sent their progression.
5.2. Historical Variations in Sedimentary Systems
Corrubedo is not a paradigmatic case in the Galician nor in the international context
[15]. Variations in sedimentary sectors have been widely studied around the world. Gen-
erally, these are sectors of great interest for activities such as tourism and their modifica-
tion could have important effects on the local population [17,51]. Recently, the evolution
of the sedimentary system of Rodas beach in the Cíes Islands was analyzed [26]. This area
is located 40 km to the south of Corrubedo, in the mouth of the ria of Vigo. The changes
observed in this system in recent decades show some similarities, such as sand extraction
activities and increasing numbers of visitors, whose influence was perceived in the path-
ways they generated on plant-covered dunes [52].
This area underwent a paradigm shift in the last decades. While in the late 20th cen-
tury, the damaging activities affecting this system were related to productive industries,
such as construction, agriculture and farming around the lagoon sector [25], nowadays
the main impacts in the Corrubedo area are related to tourism. Its beautiful landscape,
along with the promotion of its most distinctive ecosystems, led to an influx of visitors to
an area of great ecological fragility. Along the same lines, it is worth emphasizing the
importance that other factors could have, such as N and NE winds, whose influence has
been reduced due to the presence of buildings and shrub vegetation in the inner sector, as
well as variations in wind flow due to the topography and roughness of dune sectors. In
terms of natural factors, the increasing frequency and intensity of storms will play a rele-
vant role in the future of the Corrubedo Natural Park.
Figure 10.
Evolution of large shifting dune sector in different moments. (
a
) shows the dune sector in
1992; (
b
) shows the walkway in early 2000; (
c
) shows the walkway in 2002 cover in part for the dune
evolution; (
d
) shows visitants in the walkway across the dune in 2002; (
e
) reveals the ripples in the
dune zone and the new walkway position, without the across dune section in 2006; and (
f
) shows
the state of large shifting dune in the sector close to the walkway in 2012, that clearly represent their
progression.
5.2. Historical Variations in Sedimentary Systems
Corrubedo is not a paradigmatic case in the Galician nor in the international con-
text [
15
]. Variations in sedimentary sectors have been widely studied around the world.
Generally, these are sectors of great interest for activities such as tourism and their modifi-
cation could have important effects on the local population [
17
,
51
]. Recently, the evolution
of the sedimentary system of Rodas beach in the Cíes Islands was analyzed [
26
]. This
area is located 40 km to the south of Corrubedo, in the mouth of the ria of Vigo. The
changes observed in this system in recent decades show some similarities, such as sand
extraction activities and increasing numbers of visitors, whose influence was perceived in
the pathways they generated on plant-covered dunes [52].
This area underwent a paradigm shift in the last decades. While in the late 20th
century, the damaging activities affecting this system were related to productive industries,
such as construction, agriculture and farming around the lagoon sector [
25
], nowadays
the main impacts in the Corrubedo area are related to tourism. Its beautiful landscape,
along with the promotion of its most distinctive ecosystems, led to an influx of visitors
to an area of great ecological fragility. Along the same lines, it is worth emphasizing the
importance that other factors could have, such as N and NE winds, whose influence has
been reduced due to the presence of buildings and shrub vegetation in the inner sector,
as well as variations in wind flow due to the topography and roughness of dune sectors.
In terms of natural factors, the increasing frequency and intensity of storms will play a
relevant role in the future of the Corrubedo Natural Park.
Another aspect that has not been assessed but which directly affects Galician dune
systems, were oil cleaning activities after the Prestige oil spill in 2002. It is worth mentioning
their potential effect on Corrubedo, an area that received a major amount of hydrocarbons
Appl. Sci. 2021,11, 34 14 of 17
that directly affected the dynamics of species found in this area [
53
]. Other activities
indirectly affected the evolution of the Corrubedo area through cleaning tasks in the
area, the use of heavy machinery, the increase in transit of people for cleaning tasks and
modifications to the system with the installation of sand and plastic barriers in sensitive
areas, such as the Vixán lagoon.
5.3. The Importance of Coastal Management in the Future
Management is a key element in order to protect the evolution of the Corrubedo
Natural Park and to avoid potential damage to this area. In this sense, further research is
needed to identify the issues that affect the natural behavior of these fragile ecosystems
and to design measures for their conservation and protection. Furthermore, a close col-
laboration between scientists and the administration is essential, following examples in
other geographical areas, such as the case of coastal management in Scotland [
54
]. This fact
could help to develop plans and regulations adapted to the present and future dynamics of
the Corrubedo area.
Since the creation of the Natural Park and despite the measures announced for its
conservation, multiple issues are still present, leading to a decrease in the quality of
this system. Notwithstanding the presence of informative panels outlining the allowed
and prohibited activities, some visitors still ignore these guidelines. In the mobile dune
area, despite the existence of a signposted walkway, some visitors cross the established
boundaries to directly access the beach.
The inclusion of this area within the Natura 2000 network should have simultaneously
entailed the monitoring of the system’s evolution. In line with the aforementioned, it is
necessary to analyze the zones included within the protected area and their definition. In
some of these sectors, the elements described in management plans do not fully match
the actual elements present in the field, which is an obstacle for their correct management.
In addition to the revision of the described categories and their adaptation to the current
state of the area, a periodical revision of said categorization is also necessary given the high
dynamism of these ecosystems [55,56].
All the studies about the influence of different factors on system dynamics should
address possible changes in the future, along with global change and the increase in erosive
elements [
57
,
58
]. The Corrubedo Natural Park is highly vulnerable to a rise in sea level
and to the increasing intensity and frequency of marine storms [
59
]. New technologies
for gathering information and continuous improvements in processing tools are crucial
for a better management of this zone in the future. Detailed monitoring of the system’s
evolution helps to design management measures adapted to its needs. The application of
new monitoring techniques, such as unmanned aerial vehicle (UAV) flights [
60
,
61
] or the
installation of fixed cameras [
62
] to measure variations, could constitute an excellent tool
to improve the conservation of the Corrubedo Natural Park.
6. Conclusions
The main conclusions of this study are:
The mobile dune is progressively advancing towards the NE, especially in its middle
section, while there is a decrease in maximum elevation and, especially, in the area
occupied by the upper part.
The decrease in elevation of the sedimentary sector is generalized: 83% of the surface
experienced noticeable variations and elevation only increased in the progradation
zone of the mobile dune.
Anthropogenic influence is very important in the Corrubedo Natural Park, espe-
cially activities such as sand mining during the past century. Pathways have a great
importance in this sector, although their length has decreased since 2002.
The analyzed sector showed an important increase in vegetation coverage, espe-
cially since the 2000s. This fact is related with the greater presence of vegetation in
sedimentary systems studied by several authors and in different regions.
Appl. Sci. 2021,11, 34 15 of 17
Visitors and introduced infrastructures have caused major impacts in the Corrubedo
ecosystems in the last decades.
It is necessary to monitor this system in detail to understand its current dynamics and
to allow for a more efficient management.
Author Contributions:
Conceptualization, A.P.-A., X.L.O. and A.G.-P.; methodology, A.P.-A. and
A.G.-P.; formal analysis, A.G.-P. and A.P.-A.; investigation, A.P.-A. and X.L.O.; writing—original
draft preparation, A.P.-A. and A.G.-P.; writing—review and editing, A.P.-A. and X.L.O. All authors
have read and agreed to the published version of the manuscript.
Funding:
The work of AGP is supported by an FPU predoctoral contract from the Spanish govern-
ment (Ministerio de Educación, Cultura y Deporte). Grant Number: FPU16/03050. The Consellería
de Educación, Universidade e Formación Profesional-Xunta de Galicia (Axudas áconsolidación
e estruturación de unidades de investigación competitivas do SUG del Plan Galego IDT, (Am-
biosol Group, ref. 2018-PG036). The authors belong to the CRETUS Institute. All these programs are
co-funded by FEDER (UE).
Institutional Review Board Statement: Not applicable.
Informed Consent Statement: Not applicable.
Acknowledgments:
A.P.-A., A.G.-P. and X.L.O. are a part of the CRETUS Institute. We thank to
Francisco JoséDelgado Blanco and Marina Vázquez Paz for their firstly investigations about the
Corrubedo dune dynamics in the last years of the past century.
Conflicts of Interest: The authors declare no conflict of interest.
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... Gómez-Pazo, Perez-Alberti, et al., 2019;Pérez-Alberti et al., 2020). ...
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Abstract Sandy shorelines are constantly evolving, threatening frequently human assets such as buildings or transport infrastructure. In these environments, sea-level rise will exacerbate coastal erosion to an amount which remains uncertain. Sandy shoreline change projections inherit the uncertainties of future mean sea-level changes, of vertical ground motions, and of other natural and anthropogenic processes affecting shoreline change variability and trends. Furthermore, the erosive impact of sea-level rise itself can be quantified using two fundamentally different models. Here, we show that this latter source of uncertainty, which has been little quantified so far, can account for 20 to 40% of the variance of shoreline projections by 2100 and beyond. This is demonstrated for four contrasting sandy beaches that are relatively unaffected by human interventions in southwestern France, where a variance-based global sensitivity analysis of shoreline projection uncertainties can be performed owing to previous observations of beach profile and shoreline changes. This means that sustained coastal observations and efforts to develop sea-level rise impact models are needed to understand and eventually reduce uncertainties of shoreline change projections, in order to ultimately support coastal land-use planning and adaptation.
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Historical air photographs, LiDAR, and an unmanned aerial vehicle (UAV) were used to record the movement, from 1956 to 2018, of a clay and clast earthflow in a coastal valley in northwestern Spain. Two procedures were employed. The first tracked changes, in a GIS environment, in the location of eight, easily identified objects on the surface of the deposit (large boulders, topographic lobes, and the foundations of an old hut). The second used DEMs of Difference (DoDs) based on Digital Elevation Models from a 2011 LiDAR flight and two UAV flights in 2016 and 2018 obtained by Structure from Motion-Photogrammetry techniques. While the first procedure provided estimates for earthflow movement over a 62-year period, the second produced more precise data for periods of up to 8-years. The first procedure indicated that the mean rate of movement was 0.48 m•yr-1, increasing from only 0.14 m•yr-1 from 1956 to 1983 to between 0.50 and 0.83 m•yr-1 from 1983 to 2018. Despite some temporal and spatial changes in direction, rates of surface movement were quite uniform on the deposit. The increase in earthflow movement after 1983 may be related to an increase in rainfall, although human activities associated with the removal of a wrecked ship from the nearshore may have been a contributing factor. The role of debuttressing due to the wave-induced removal of lateral support from the toe of the deposit is less clear. While there was no clear relationship between wave erosion and rates of movement, coastal retreat may have triggered changes in the direction and sediment flux in the toe of the deposit. This effect could have been tempered by negative feedback, however, whereby coastal erosion and increased flow activity were countered by the protection afforded by the accumulation of large, dislodged boulders on the beach. Because of this feedback, it is difficult to predict the impact of sea level rise and other elements of climate change along this coast.