1,721,066 research outputs found
Beach cusps and gravel deposits monitoring in a mixed sand and gravel beach from the Apuo-Versiliese coast (Tuscany, Italy): preliminary data
No full textMonitoring backshore and foreshore gravel deposits on a mixed sand and gravel beach (Apuane-Versilia coast, Tuscany. Italy)
No full textObservations on gravel moving on the foreshore and the backshore have been performed on a mixed sand and gravel beach of Northern Tuscany (Italy) subject to erosive processes. In addition to the gravel naturally transported by Magra River, a large amount of gravel has been discharged by human activity through nourishments as part of a series of protection systems. Two transects, with an average spacing of 500 m, were carried out parallel and perpendicular to the coast-line on the beach-face and on the step, and gravel deposits and cusps evolution were monitored. The study was performed following sea-weather changes, in order to obtain data during fair-weather and storm-weather conditions, and shortly after storm decay. The results confirm the existence of a south-directed longshore drift. At the same time, it seems that gravel clasts are no more present on the backshore during major storms. These observations allow to distinguish five phases within a fair-weather to storm-weather cycle and to determine the response of gravel movement to sea-weather conditions
Grain size characterization of modern and ancient dunes within a dune field along the Pisan coast (Tuscany, Italy)
Full text linkIn this paper, grain size analysis on a large number
of samples from a dune field within the Migliarino – San
Rossore – Massaciuccoli Regional Park has been carried out
in order to define the textural characterization of modern
and ancient dune ridges. More than 200 samples along five
transects have been collected from the backshore, the active
dunes and the steady dunes up to the last recognizable dune
ridge. The samples have been dry-sieved and the obtained data
have been processed electronically to achieve textural parameters
such as mean diameter and sorting. The results showed
similar trends of the transects throughout the entire dune field.
In particular, the grain size tends to decrease towards the most
ancient dune ridges, showing a significant drop at the transition
between active and inactive areas. The drastic decrease
might be related to a possible variation of River Arno sediment discharge occurred after the XVIII century
Morphodynamic evolution of an artificial pebble beach in a ten month span; Marina di Pisa, Tuscany, Italy: preliminary data
No full textThe present study has been carried out to evaluate the morphodynamic behaviour of an
artificial pebble beach during a prolonged period of ti me. In this span of about 1O months, a series
of storms has hit the coast, which have made possible to define the response of the beach after
each high-energy event. The study area is located on the Pisan coast, exactly at Marina di Pisa.
The shores of Marina di Pisa are about 6 km in length and are delimited by Arno River mouth to
the north and the city of Tirrenia to the south. The littoral drift is directed to the south throughout
this area (Gandolfi and Paganelli, 1975; Aiello et al., 1975; Mazzanti, 1983; Pranzini, 2004). Tides
are not overly significant, rarely exceeding 30 cm. The only source of sediments input is
represented by Arno River's solid discharge, which is definitely not sufficient to naturally feed the
coast. As a matter of fact, the Pisan coast has been struck by serious erosion processes since
early xxi Century, which have caused a huge retreat of the coastline in several sectors. The
decrease in Arno River sediments discharge and the massive use of hard protection systems
(breakwaters, groynes) are considered as the main reasons to explain the erosion processes,
which stili affect the coast. Breakwaters and groynes were built as a first defence against the
strong wave processes acting on this coast: they were fit to prevent severe flooding, but they
hampered the natural nourishment, hence the existence, of the beaches as well. Therefore, coarse
sediments have been used to artificially feed the shore: during the mid-Nineties few gravel (1O to
30 mm diameter) beaches were built, but they resulted not well suited to that particular setting.
Hence, pebble-to-cobble grain size has been used in subsequent beach fills. The Province of Pisa
has recently completed the construction of three pebble beaches at Marina di Pisa. Due to the
relative lack of knowledge on this kind of beaches, it has been stressed (Buscombe and Masselink,
2006) a continuous and in-depth monitoring of the morphodynamics (sedimentology,
geomorphology, physical processes). However, the research on gravel beaches has been pushed
lately by the large spreading of gravel replenishments as a form of coastal protection. Thus,
repeated and intensive surveys of gravel beach systems should improve the understanding of this
no more uncommon environment.
The beach under study, named Celi 7, is characterized by very coarse grain size (mostly 30
to 70 mm spoils of Carrara marble quarries), two groynes at both ends and a submerged
breakwater 60 m off the coastline. lt is about 250 m in length and 40 m wide. The nearshore is very
steep and it reaches a 3 m plus depth just 20 m seaward of the coastline.
The geomorphological aspect of the research has been addressed by the use of a highaccuracy
GPS instrument. The observations were periodically carried out through July 2007 and
Aprii 2008 and intensified in particular after significant high-energy events. This approach has
allowed to define the beach response under changing sea-weather conditions: besides, it has
made possible to appraise the rate the beach width narrows and, consequently, the effectiveness
of the nourishment. Five profiles were outlined on the beach: along each profile, any single
gradient variation was pinpointed and tracked in order to obtain highly detailed beach sections.
The comparison between these sections has clearly showed a remarkable retreat of the beach
right after the most powerful storms. The retreat is measurable to the tune of 11 m. Given the
originai width of about 40 m, this value is even more noteworthy.
Subsequently, the study has been extended to the sea-bottom fronting the beach through a
series of surveys performed with a single beam instrument installed on a boat. The echo-sounder
tracked points every second, so less than ten back-and-forth routes have been sufficient to
complete the survey and, through data processing, to reconstruct the sea-bottom geomorphology.
These surveys have been necessary to complete rough estimates of volumes of sediments moved
during the period of observation.
The research has been rounded out with two grain size analyses carried out to evaluate the
sedimentologic variations occurring before and after a series of storm. Any morphologic element
has been sampled, namely the step, the beachface, the ordinary berm, the storm berm and the backshore. The results have showed i) slight variations in mean grain size on the step and, in
particular, on the beachface, where values almost coincide; ii) the Mean (Mz) plot of the second
sampling shows exactly the same trend for each profile, that is a decrease moving from the step to
the ordinary berm and a subsequent increase towards the backshore.
In conclusion, the activities carried out in this research have been directed towards a better
definition of this matter, which is of paramount importance not only to increase the knowledge on a
topic not overly debated and studied in the literature, but even for a successful construction of
enormous protection structures like these ones
On the profile evolution of three artificial pebbles beaches at Marina di Pisa Italy
No full textIn this paper, the profiles of three artificial coarse-grained beaches located at Marina di Pisa (Tuscany, Italy) were monitored from April 2008 to May 2009 in order to define the response of the beaches to major storms that occurred during the study. Two beaches are similar, the third differs in length and in the level of protection, being less than half the length of the others and devoid of an offshore submerged breakwater. The work was achieved by means of accurate topographic surveys intended to reconstruct the beach profile from the backshore up to the foreshore-upper shoreface transition (step). The surveys were performed with an RTK-GPS instrument, which provided extremely precise recording of the beach. The most significant features of the beaches were tracked during each survey; in particular, the landward foot of the storm berm, the crest of the storm berm, the coastline, and the step crest were monitored. Five cross-shore transects were traced on each beach. Along these transects, any meaningful slope change was recorded to obtain accurate sections of the beach. The field datasets were processed with AutoCAD software to compare the beach profile evolution during the year-long research. The results showed a comparable evolution of the twin beaches: the resulting storm berm retreat of about 15 to 19. m is a remarkable feature considering the coarse grain size and the offshore protection. Due to the absence of the breakwater, the third beach was characterized by even higher values of recession (over 20. m), and showed hints of wave reflection-related processes after the huge, steep storm berm had been formed and grown after the high energy events. These processes were not as evident on the twin beaches. These results underline the different response of three similar protection schemes, and the importance that frequent monitoring of the beach morphology holds when it comes to coastal management issues
Volume shift reckoning on an artificial pebble beach at Marina di Pisa (Italy)
No full text"Observations on gravel moving on the foreshore and the backshore have been performed on a mixed sand and"
"gravel beach of Northern Tuscany (Italy) subject to erosive processes. In addition to the gravel naturally transported by Magra River, a large amount of gravel has been discharged by human activity through nour-"
"ishments as part of a series of protection systems. Two transects, with an average spacing of 500 m, were carried out parallel and perpendicular to the coast-line on the beach-face and on the step, and gravel deposits and cusps"
"evolution were monitored. The study was performed following sea-weather changes, in order to obtain data during fair-weather and storm-weather conditions, and shortly after storm decay. The results confirm the ex-"
"istence of a south-directed longshore drift. At the same time, it seems that gravel clasts are no more present on the backshore during major storms. These observations allow to distinguish five phases within a fair-weather to storm-weather cycle and to determine the response of gravel movement to sea-weather conditions.
Monitoring of two artificial gravel beaches from Marina di Pisa (Tuscany, Italy): preliminary data
No full textPreliminary results of a monitoring carried out on the shore of Marina di Pisa
(Tuscany, ltaly) are presented in this work: Marina di Pisa has been the centre
of an impressive coastal defence project. This project has got started in the
autumn of 2006 and will come to an end in the spring of 2008: it has been
necessary due to the poor conditions of this area, stili struck by lingering
episodes of erosion . In fact, dating back to the late XIXth century the Pisan
shore experienced first erosive phenomena (due t o a strong decrease of River
Arno sediments discharge caused, amongst others, by an uncontrolled
excavation of the riverbed), progressively worsened up to seriously menace the
city centre of Marina di Pisa. The defence of buildings and houses had become
a pressing priority and it was realized by the accomplishment of hard
protection systems like sea walls (rock armouring in particular): these sea
walls solved the problem they were built for, but they caused the complete
erosion of the fronting sand beaches as well. Subsequent forms of defence
(breakwaters 80 m off the coast-line and grave l replenishments) were carried
out, but with no particular gain even by an environmental impact standpoint.
The above mentioned defence project has been put into execution in such a
worrying situation: i t consists of the enlargement of few pre-existent groynes
(subsequently linked at the head by submerged breakwaters) and of a huge
gravel replenishment. A series of big cells will form that way, characterized by
better water ctrculattOn, lessened envtronmental tmpact and wider gravel
beaches.
The monitoring ai m is to contro l the shore evolution in order to better define
the processes acting on that sector of the littoral zone and, moreover, the need
of integration and/or variations to the project. Besides, the monitoring has
been extended to a beach (named Gorgona) one kilometre south of the cells
where larger works h ave bee n executed: gravel replenishments have been
realized a Iso on this beach, but the difference lies in the absence of offshore
breakwaters. Therefore, it w ili be possible verifying the evolution of both these
beaches given the sa me sea weather and w ave motion conditions. Thus beach
profile and coast-line surveys have been accomplished at Gorgona beach using
GPS technologies during various climatic conditions: so it has been possible
keeping under contrai the beach evolution without the interference of any
offshore structures parallel to the shoreline. At the same time sampling along
transects going from the backshore to the shoreface have been made to define
the grain-size variations normal to the coast-line. This observation has been
particularly interesting because further shows that gravel and pebbles assume
a dimensionai zonation on the backshore, while their diffusion under water is
probably limited to the step, that is the limit foreshore-upper shoreface.
Grain-size analysis has been conducted on every sample; the coarsest ones
have undergone morphometric analysis as well j ust to better locate the
mentioned zonation.
Considering the remarkable peculiarity of the area in which this project has
been rea lized (so much peculiar to probably make Marina di Pisa the only case
of such a type), the obtained resu lts will be very useful not only to better
understand processes acting on a gravel beach, but even to sort of deal with
this kind of coastal defence works by improving the approach with which they
are studied and at the same time to optimize them in the future
Sediment displacement on a corse artificial beach at Marina di Pisa: volumes shift (preliminary data)
No full textA reckoning of sediment displacement in terms of volumes shift on a beach is
paramount where onerous investments have been spent to guard an area
against erosion through coarse replen ishments. This research has been carried
out on the coast of Marina di Pisa (Tuscany), where a huge gravel and pebble
replenishment was set up to protect the town from the dangerous effects of
strong storms.
The Pisa n coast has been affected by lingering erosive processes, and the area
of Marina di Pisa makes no exception. The erosion sprang in the late XIXth
century due to a harsh decrease in River Arno's sediment discharge: the uncontrolled excavation of the river-bed, the widespread construction of hard
embankments and the rigid structures set up to reduce the hydrological hazard
of mountain slopes, ali combined to dwindle the bulk of the sediments that
naturally fed the beaches. The eros io n wiped out long sectors of the sandy
beaches, which characterized the Pisan coast, and became a serious menace
even to the centre of Marina di Pisa. Hard protection structures (g roynes,
detached breakwaters and rock armour) were built to counteract the land
retreat, which eventually ceased at the expense of the natura l sandy beach
environment. In the late Nineties a first gravel (4-to-lOmm) replenishment was
carried out to both protect the coast and give the beach some tourist appeal.
The shortcoming of this grain-size was that the major storms which struck the
coast literally cast the grave l onto the promenade, with any kind of risk to the
population. Therefore, in 2006 a new, la rger replenishment was carried aut,
th is t i me using 30-to-90mm marble pebbles. This rep lenishment was realized
on three beaches along the shore of Marina di Pisa; the beach where this
research has been performed on is named Cella 7.
The Cella 7 is a 250m long, 30m wide pebble beach bound at both ends by
groynes, and seaward by a submerged breakwater SO m off the coast· line. The
sea-bottom is very steep, since the 3m depth is reached within less than 20m
from the coast-line. The sea-bottom between the step and the breakwater is
entirely constituted by sand.
A number of su rveys has bee n made on th is beach after any significant storm
since the autumn of 2007: during each survey the subaerial beach profile was
registered by means of a highly accurate GPS instrument. Basically, a point
every 10m was registered a long the shore on the mai n features that define the
beach, i.e. the step, the beach-face, the ordinary berm, the storm berm and
the base of the lee-side of the storm ber m. Moreover, an extremely accurate
profile was taken every SO m, fora total of five profiles in which points were
reg istered o n any significant slope change. The submerged part of the beach
was surveyed with an echo-sounder Single Beam instrument. Data from these
two sectors of the beach were merged afterwards with ArcGIS software. Then,
the outcome of the m erge was processed yet aga in to yield meaningful
indications about sediment displacement and volumes shifting.
Preliminary data point out a remarkable retreat of the coast-line a long with the>
formation of an impressive and steep storm berm . The measured retreat after
a series of intense storms reaches the 13m mark; though not particularly
worrisome, this feature forces local authorities to leve l the beach at least once
per year. The bulk of the pebbles is pushed landward especially during highest
energy storms, while a loss of sediments out of the celi del imited by the
groynes an d the submerged breakwater is no t detected. Therefore, these
pre liminary results show a slight volumetric increase of the subaerial beach
after most significant high-energy events
Extreme erosion of a dune crest within a short timespan (january – september 2016): the recent case in the Migliarino – San Rossore – Massaciuccoli Regional Park (Tuscany,Italy)
No full textBeach erosion is a process that in the last decades is affecting several coastal areas around the world. Unfortunately the Tuscany coast makes no exception. The factors responsible of this phenomenon are different: some are natural, some other are related to human activities. Usually the latter determine drastic hastening of ongoing processes, mainly because they act over temporal scales much smaller than those typical of the natural factors. In this paper, multiple topographic surveys were carried out along a 5 km long sector of coast located within the boundaries of the Migliarino – San Rossore – Massaciuccoli Regional Park in order to evaluate the evolution state of the area within a 9-months timespan (January 2016 – September 2016). The results emphasize the importance to increase the knowledge about the morphodynamics processes acting on this area based on the resulting retreat that was observed analyzing the data: in just 4 months the crest of a 9 m high dune retreated of about 6 m, which resulted in a volume loss of about 80 m3/m along the selected transect. This worrying outcome implies the need to manage this sector of coast applying a rather different approach relative to those used thus far. It is paramount to consider each sector of coast as a whole and not separately, that is in accordance with the physiographic unit rather than territorial and administrative limits. In addition, this new approach must also take care of the coastal environment in the direction orthogonal to the coastline, adding into the equation rivers and catchment areas, which are the main source of sediments feeding the beaches
Integrating Different Databases to Offer a Geological Perspective of Coastal Management: A Review Case from the Northern Tuscany Littoral Cell (Italy)
No full textA multidisciplinary approach to coastal process research has been increasingly encouraged in the last decade, and it is now widely accepted for a thorough, in-depth analysis of any issue related to such an environment. In this study, we emphasized the need for the integration of different time-scales, not just disciplines. Many geological datasets provided by several sources contribute to the knowledge of coastal processes. We retrieved the available datasets about morphodynamic, geomorphological, and geological aspects of the northern Tuscany (Italy) littoral cell, and we merged all of them with QGIS (Quantum Geographic Information System) applications to provide an assessment of the current situation starting from a geological perspective. Data processing resulted in maps and stratigraphic sections that confirmed that sediment supply is the main factor driving the evolution of the littoral cell. Such a perspective is also useful for the development of reliable coastal evolution future scenarios, not just for a better definition of the present situation. As these datasets are now available for many sectors of coast around the world, this approach may be easily replicated elsewhere to improve coastal management policy making
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