2,649 research outputs found
Sea Surges in Camargue: Trends over the 20th century.
No full textContinental Shelf Research 27 (2007) 922–934
Sea surges in Camargue: Trends over the 20th century
A. Ullmanna,b,, P.A. Pirazzolic, A. Tomasind,e
aUFR des Sciences Ge´ographiques et de l’Ame´nagement, Universite´ d’Aix-Marseille I, Aix en -Provence, France
bCEREGE—UMR 6635, Aix en Provence, France
cCNRS-Laboratoire de Ge´ogrphie Physique, 1 place Aristide Briand, 92 195-Meudon, France
dCNR-ISMAR, Venezia, Italy
eUniversita` di Venezia, Venezia, Italy
Received 8 November 2005; received in revised form 24 November 2006; accepted 4 December 2006
Available online 25 January 2007
Abstract
The vulnerability to short-term and long-term sea-level rises is particularly high in subsiding deltaic areas, especially in
microtidal seas, when surges (the differences between the observed sea heights and the simultaneous astronomical tide) are
frequent. At the Grau-de-la-Dent tide-gauge in the Camargue (Rhone delta, France), daily sea-level records are available
since 1905. Hourly tide data spanning the period 1979–1995 were obtained through the digitisation of the original paper
records: the local harmonic constants and the surges for the whole 20th century have been computed from these hourly
observations. It appears that the annual maximum observed sea-level height increases by 4 mm/yr at a rate that is two
times faster than the average observed relative sea level. The increasing trend of the annual maximum positive sea surges
(+1.9 mm/yr), which is equal to the average relative sea-level rise, is thus responsible for this difference. The most
important meteorological factor associated with local sea-surge occurrences is wind blowing from 1001 to 1201 sectors,
which tends to push the water toward the coasts. Since 1961, the frequency and the speed of wind from this sector
increased, although with some variability, thus contributing in part to the increase in the frequency and intensity of the
surges. Due to the changing hydrodynamics phenomenon in the Camargue, a positive feedback mechanism between
extreme marine events and shoreline regression is another factor to explain the sea-surge rise over the long term. The
increase in sea-surge frequency and height during the last century is especially of concern in the deltaic area if the nearfuture
global sea-level rise predicted by climate models is also taken into account.
r 2007 Elsevier Ltd. All rights reserved.
Keywords: Sea level; Surge; Tide; Wind; Flooding risk; Camargue; Rhone delta
1. Introduction
Any rise in sea level will have adverse impacts
such as coastal erosion and flooding, depending on
the time scale and the magnitude of the rise and the
human response to it (Paskoff, 1993). A rise in sea
level may be due to several factors acting on various
time scales, i.e., atmospheric storms (Bouligand and
Pirazzoli, 1999; Pirazzoli, 2000; Trigo and Davies,
2002; Pirazzoli and Tomasin, 2002), river flooding
in estuaries (Svensson and Jones, 2002), but also
land sinking or similar non climate-related changes,
linked to sediment compaction, isostasy, coastal
geomorphologic evolutions or urban development.
ARTICLE IN PRESS
www.elsevier.com/locate/csr
0278-4343/$ - see front matter r 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.csr.2006.12.001
Corresponding author. CEREGE, Europoˆ le Me´diterrane´en
de l’Arbois, B.P 80, 13545 Aix-en-Provence, France.
E-mail address: [email protected] (A. Ullmann)
Les variations du niveau de la mer depuis 20 000 ans : Pirazzoli P.A., Sea level changes, the last 20,000 years
No full textPaskoff Roland. Les variations du niveau de la mer depuis 20 000 ans : Pirazzoli P.A., Sea level changes, the last 20,000 years. In: Annales de Géographie, t. 107, n°600, 1998. p. 249
Marine deposits of late glacial times exposed by tectonic uplift on the east coast of Taiwan
No full textRecent changes in measured wind in the NE Atlantic and variability of correlation with NAO.
Full text linkAbstract. The paper deals with wind measurements,
recorded since the 1950s, at twelve meteorological stations
along a transect near the westernmost European border, between
64 and 44 N. Extreme wind speed tends to decrease
sharply near the northern boundary (at Reykjavick), near the
middle of the study area (at Shannon and Valentia) and near
the southern boundary (at Brest and Cap Ferret), to increase
at Thorshavn, with less significant trends at the other stations.
Average wind speeds confirm the above tendencies,
with an additional increasing speed at Lerwick, Kirkwall,
Malin Head, Belle-Ile and Cap Ferret.
To compare changes in wind activity, the data have been
subdivided into three periods: until 1975, 1976–1992 and
1993–2008. Frequencies have been computed also for the
“winter” (October to March) period, per quadrants, and for
occurrences exceeding the speed of 15ms−1.
At Reykjavick a recent increase in the frequency of strong
winds has occurred from various directions. Between 62 N
(Thorshavn) and 59 N (Kirkwall) strong wind has been increasing
since 1975. Minor changes can be observed at
Stornoway, whereas at Malin Head the greatest increase for
southerlies and westerlies is observed during the 1976–1992
period. At Belmullet, the frequency of strong southerlies has
almost doubled since 1992, while at Shannon and Valentia it
remains quite low. Finally at Brest and Belle-Ile, westerlies
are predominant among winds >15ms−1.
Important changes in time and latitude appear in the
correlation with the NAO (North Atlantic Oscillation) index.
The highest correlation coefficients, calculated with
monthly or seasonal means between the early 1950s and
1975, are observed from between 58 N (Stornoway) and
Iceland, whereas low positive coefficients are reported more
Correspondence to: P. A. Pirazzoli
([email protected])
south. During the period 1976–1992, when increasing NAO
index is predominant, positive correlation improves southwards
as far as 54 (Belmullet) with some improvement also
at Shannon and Valentia, while it remains low or even negative
near the French Atlantic coast. Finally in the 1993–
2008 period, correlation improves for all the stations south
of 54 N (Belmullet), while it weakens more north
Sea-level and surges in the Adriatic area: recent trends and possible near-future scenarios.
No full textEstimation of return periods for extreme sea levels: a simplified empirical correction of the joint probabilities method with examples from the French Atlantic coast and three ports in the southwest of the UK
No full textOcean Dynamics
DOI 10.1007/s10236-006-0096-8
Paolo Antonio Pirazzoli . Alberto Tomasin
Estimation of return periods for extreme sea levels: a simplified
empirical correction of the joint probabilities method
with examples from the French Atlantic coast
and three ports in the southwest of the UK
Accepted: 8 November 2006
# Springer-Verlag 2007
Abstract The joint probability method (JPM) to estimate
the probability of extreme sea levels (Pugh and Vassie,
Extreme sea-levels from tide and surge probability. Proc.
16th Coastal Engineering Conference, 1978, Hamburg,
American Society of Civil Engineers, New York, pp 911–
930, 1979) has been applied to the hourly records of 13
tide-gauge stations of the tidally dominated Atlantic coast
of France (including Brest, since 1860) and to three stations
in the southwest of the UK (including Newlyn, since 1916).
The cumulative total length of the available records (more
than 426 years) is variable from 1 to 130 years when
individual stations are considered. It appears that heights
estimated with the JPM are almost systematically greater
than the extreme heights recorded. Statistical analysis
shows that this could be due: (1) to surge–tide interaction
(that may tend to damp surge values that occur at the time
of the highest tide levels), and (2) to the fact that major
surges often occur in seasonal periods that may not
correspond to those of extreme astronomical tides.We have
determined at each station empirical ad hoc correction
coefficients that take into account the above two factors
separately, or together, and estimated return periods for
extreme water levels also at stations where only short
records are available. For seven long records, for which
estimations with other computing methods (e.g. generalized
extreme value [GEV] distribution and Gumbel) can be
attempted, average estimations of extreme values appear
slightly overestimated in relation to the actual maximum
records by the uncorrected JPM (+16.7±7.2 cm), and by
the Gumbel method alone (+10.3±6.3 cm), but appear
closer to the reality with the GEV distribution (−2.0±
5.3 cm) and with the best-fitting correction to the JPM
(+2.9±4.4 cm). Because the GEV analysis can hardly be
extended to short records, it is proposed to apply at each
station, especially for short records, the JPM and the sitedependent
ad hoc technique of correction that is able to
give the closest estimation to the maximum height actually
recorded. Extreme levels with estimated return times of 10,
50 and 100 years, respectively, are finally proposed at all
stations. Because astronomical tide and surges have been
computed (or corrected) in relation to the yearly mean sea
level, possible changes in the relative sea level of the past,
or foreseeable in the future, can be considered separately
and easily added to (or deduced from) the extremes
obtained. Changes in climate, on the other hand, may
modify surge and tide distribution and hence return times
of extreme sea levels, and should be considered separately.
Keywords Tide gauge . Sea level . Extreme values .
Return period . Atlantic coast . France . UK
1 Introduction
Most methods usually employed to estimate return periods
of extreme values for hydrological or meteorological
datasets (extremes per block, threshold method, annual
maxima [Gumbel] method) are based on a number of
assumptions: (1) that we deal with statistical variates; (2)
that the initial distribution from which the extremes have
been drawn, and its parameters, remains constant from one
Responsible editor: Roger Proctor
Parts of this paper have been presented orally at the session
“Geophysical extremes: scaling aspects and modern statistical
approaches” of the EGU General Assembly, Vienna, 2–6 April
2006.
P. A. Pirazzoli (*)
Laboratoire de Géographie Physique,
Centre National de la Recherche Scientifique (CNRS),
1 Place Aristide Briand,
92195 Meudon Cedex, France
e-mail: [email protected]
A. Tomasin
Università di Venezia
Holocene tectonic uplift deduced from elevated shorelines, eastern Coastal Range of Taiwan
No full textEvolution récente des vents de surcote sur les cotes de la Méditerranée Centrale et de l'Adriatique.
No full textRecent evolution of surge-related events and assessment of coastal flooding risk on the eastern coasts of the English Channel.
No full textOcean Dynamic
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