Document Actions

ijege-14_02-tarragoni-et-alii.pdf

background image
5
Italian Journal of Engineering Geology and Environment, 2 (2014)
© Sapienza Università Editrice
www.ijege.uniroma1.it
DOI: 10.4408/IJEGE.2014-02.O-01
C
laudia
Tarragoni
(*)
, P
iero
BelloTTi
(**)
, l
ina
Davoli
(***)
,
r
ossana
raffi
(***)
, e
lvidio
lupia palmieri
(***)
(*)
AIGeo (Italian Association of Physical Geography and Geomorphology) Member - Viale Eritrea 91 - 00199 Rome, Italy
(**)
AIGeo (Italian Association of Physical Geography and Geomorphology) Member - Via Mare Glaciale Artico 51 - 00122 Rome, Italy
(***)
Sapienza University of Rome, Department of Earth Sciences - Piazzale Aldo Moro 5 - 00185 Rome, Italy
Corresponding Author: claudia.tarragoni@uniroma1.it
Assessment of coAstAl vulnerAbility to erosion:
the cAse of tiber river DeltA (tyrrheniAn seA, centrAl itAly)
extenDeD AbstrAct
i paesaggi costieri sono il risultato di processi morfogenetici particolarmente vivaci; le rapide modificazioni che essi subiscono de-
terminano, in molti casi, una spiccata vulnerabilità in relazione all’opera aggressiva del mare. le aree costiere rappresentano, in genere,
le zone a più alta densità insediativa e sono spesso minacciate da intensi fenomeni di erosione; pertanto, l’analisi della vulnerabilità
costituisce un utile strumento per la mitigazione di tali fenomeni e per una più oculata gestione dell’ambiente costiero.
in questo lavoro si è voluto proporre una metodologia per la valutazione della vulnerabilità locale, che differisce dalle metodologie
proposte da diversi autori nel passato, essenzialmente per due aspetti: il primo riguarda la scala di lavoro scelta (di grande dettaglio,
con ovvie implicazioni di carattere morfologico e climatico); l’altro consiste nella distinzione fra vulnerabilità potenziale, relativa
solamente a fattori naturali, e vulnerabilità effettiva, che prende in considerazione anche variabili antropiche, il cui contributo può far
diminuire o aumentare la vulnerabilità stessa.
la valutazione della vulnerabilità locale (local vulnerability assessment) si fonda sia su una serie di variabili morfometriche e
morfodinamiche (quantitative e qualitative) in grado di esprimere la vulnerabilità potenziale (naturale), sia su una serie di variabili con-
nesse all’attività antropica che influiscono sulla vulnerabilità effettiva. la valutazione della vulnerabilità locale è basata sul calcolo di
un indice di vulnerabilità Costiera attraverso una matrice ove si assegna ad ogni variabile (naturale o antropica) un peso e un punteggio;
ciò consente la costruzione di una carta della vulnerabilità costiera, nella quale il litorale risulta suddiviso in settori a diverso indice di
vulnerabilità Costiera. Tale approccio metodologico consente, dunque, di individuare i settori costieri a maggiore vulnerabilità e che,
in priorità assoluta, necessitano di interventi di mitigazione del rischio associato.
l’area oggetto di studio è l’apice deltizio del fiume Tevere, un litorale di grande pregio storico- ambientale e fortemente urbaniz-
zato; tale paraggio, allungato per circa 12 km, negli ultimi sessanta anni ha subìto fenomeni di erosione così marcati da rendere neces-
saria la messa in opera di diverse tipologie di protezionedella spiaggia, dell’abitato e delle vie di comunicazione.
il litorale in esame presenta per circa il 40% valori di vulnerabilità potenziale molto elevata (specie in corrispondenza del Canale
di fiumicino) e per il restante 60% valori di vulnerabilità potenziale elevata. le variabili naturali (morfometriche e morfodinamiche)
che contribuiscono ad accrescere la vulnerabilità sono essenzialmente: la quota media della spiaggia emersa, la pendenza della spiaggia
sommersa e le variazioni della linea di riva storiche e recenti.
lungo tutto il litorale in studio si rileva una forte pressione antropica: numerose e diffuse sono le strutture insediative, anche a scopo
turistico, che negli ultimi decenni sono state minacciate da fenomeni erosivi così cospicui da rendere necessaria la messa in opera di
strutture a difesa. i valori di vulnerabilità effettiva più elevati si registrano nella parte settentrionale dell’apice deltizio, fra focene e
fiumicino. lungo il litorale prospiciente l’abitato di ostia, nonostante l’intensa urbanizzazione della fascia costiera, la vulnerabilità
effettiva
è relativamente bassa, grazie alla messa in opera di difese di diversa tipologia, prevalentemente caratterizzate da ripetuti inter-
venti di ripascimento della spiaggia, che hanno contribuito ad un significativo decremento della vulnerabilità effettiva.
Senza dubbio, la redazione di una carta che descriva il grado di vulnerabilità costiera di un determinato paraggio può essere un utile
strumento della pianificazione territoriale, rivolto in particolare agli amministratori locali. a tal fine, la metodologia proposta è estensi-
bile ad altre aree costiere a regime microtidale, come quella considerata in questo lavoro.
background image
c. tArrAgoni, P. bellotti, l. DAvoli, r. rAffi & e. luPiA PAlmieri
6
Italian Journal of Engineering Geology and Environment, 2 (2014)
© Sapienza Università Editrice
www.ijege.uniroma1.it
AbstrAct
Coasts are highly sensitive to dynamic geomorphic process-
es that determine rapid environmental changes and landscape
modifications and are potentially vulnerable to accelerated ero-
sion hazard.
Coasts densely inhabited and settled by human infrastructures
are threatened by severe erosional processes; therefore the coastal
vulnerability analysis may represent an essential tool for hazard
mitigation and management purposes.
Tiber river delta has been selected as study area because it
has a particularly high vulnerability to sea erosion that has made
necessary several protection interventions in recent decades.
The local vulnerability assessment (lva) methodology pro-
posed differs from the previous ones for two aspects: the work-
ing scale (with its morphological and climatic implications), and
the distinction between potential (due to natural conditions alone)
and effective vulnerability (where the anthropogenic action is
present and may contribute to vulnerability mitigation or less).
The lva takes into account quantitative and qualitative spa-
tial variables that express morphometric and morphodynamic
natural factors of vulnerability, as well as selected anthropo-
genic factors.
Based on a system of numerical weights and scores, the lva
allows the construction of a local vulnerability map in which the
Coastal vulnerability index (Cvi) is represented for different
sectors of the study area.
The aim of lva is to single out he main vulnerable zones that
should have priority in the mitigation strategy performed within
the study area.
This is the first study finalized to calculate Cvi at local scale
and its results show that the whole coast strip of the study area
has high and very high values of potential vulnerability, while the
values of effective vulnerability decrease where suitable defences
are present.
K
ey
words
: coastal erosion, vulnerability,Tiber River delta, Italy
introDuction
Coasts are landscape features that undergo deep and fast
changes; some morphological modifications can became highly
hazardous where marked erosional processes occur. The present
high intensity of coastal changes is a problem of worldwide impor-
tance that becomes crucial along densely inhabited coastal belts.
most of the coasts of italy and of the other european coun-
tries - where human settlements exist since long time ago - suffer
for particularly marked beach retreat. at present, coastal zones in
europe hostlarge human populations and significant socio-eco-
nomic activities. one third of the about 450 million of inhabitants
of the european union (eu) is estimated to live within 50 km
from the coastline, and the 19% (86 million people) of the total
eu population livesin a 10 km wide coastal strip (eea, 2013).
The proportion is as high as 100% in Denmark and it reaches 75%
in the united Kingdom and the netherlands (n
iCholls
& K
lein
,
2005). The 75% of the inhabitants of the countries overlooking
the mediterranean Sea lives in coastal areas; in italy this value is
between 60 and 70% (annuario.isprambiente.it).
The urbanisation and rapid growth of coastal cities have been
a dominant trend over the last decades that led to the development
of numerous megacities in many coastal regions around the world.
as a result both demand on coastal resources and people exposure
to coastal hazard have been increasing in time (s
terr
et alii, 2003).
The italian shores stretches for over 7500 kmand are charac-
terized by landscapes of outstanding natural value; a great deal
of the national resources come from the coastal areas, as they
host major urban and industrial centres, and continuously grow-
ing tourism activities (d’a
lessandro
et alii, 2002).
The recent reports about climate changes over the entire
globe (ipCC, 2013) have placed serious problems in the manage-
ment of coastal resources as well as in the assessment of coastal
vulnerability and related risks. To understand the way the coast
will evolve is therefore of primary importance.
as K
lein
& n
iCholls
(1999) stated, vulnerability to impacts
is a multi-dimensional concept, encompassing bio-geophysical,
economic, institutional and socio-cultural factors. owing to the
great diversity of natural coastal systems and to the local and re-
gional differences in relative sea-level rise and climatic changes,
the occurrence of and response to these impacts will not be uni-
form around the globe.
Different approaches may be followed to assess coastal vul-
nerability at different spatial and temporal scales, as well as in
different regions and for different policy purposes. Since 1990,
a number of major efforts have been made to develop guidelines
and methodologies for the assessment of coastal vulnerability to
sea-level rise (G
ornitz
, 1990; G
ornitz
et alii, 1991, 1994).
in the european scientific literature, different procedures are
suggested to evaluate coastal vulnerability to climate change at
different spatial and temporal scales (r
amieri
et alii, 2011).These
procedures can be categorized into: i) index-based methods that
include several variants of the Coastal vulnerability index Cvi
(G
ornitz
, 1990; G
ornitz
et alii, 1991, 1994); ii) giS-based deci-
sion support systems that helps decision makers in the sustainable
management of natural resources and also in the choice of mitiga-
tion and adaptation measures (m
oCenni
et alii, 2009; s
Chirmer
et
alii, 2003); iii) methods based on dynamic computer models that
allow to integrate the time dimension in the analysis and mapping
of vulnerability and risks of coastal systems to climate change
(h
inKel
, 2005; h
inKel
et alii, 2010; m
Cleod
et alii, 2010; K
enny
et alii, 2000; W
arriCK
et alii, 2005; W
arriCK
, 2009; h
su
et alii,
2006; h
enrotte
, 2008; e
nGelen
et alii, 1998; m
oKreCh
et alii,
2009; t
orresan
et alii, 2012).
background image
Assessment of coAstAl vulnerAbility to erosion:
the cAse of tiber river DeltA (tyrrheniAn seA, centrAl itAly)
7
Italian Journal of Engineering Geology and Environment, 2 (2014)
© Sapienza Università Editrice
www.ijege.uniroma1.it
The aim of this paper is to propose a methodology for the
estimation of the Coastal vulnerability index (Cvi) at the local
scale that is influenced by both natural and human factors. The
short term analysis for the evaluation of Cvi has been performed
in order to support local assessments and to provide information
suitable for the identification of areas where vulnerability could
be relatively high and for planning preventive adaptation meas-
ures (e.g. construction of coastal defences, beach nourishment,
planning and zoning of coastal territory). The final outcomes of
the analysis are the identification and ranking of homogeneous
vulnerable units for each target of interest, the individuation of
vulnerable areas and the definition of the priorities of interven-
tion. The Tiber Delta area was selected to test the lva methodol-
ogy and the main results of the analysis are presented and dis-
cussed in this paper.
cAse stuDy AreA: the tiber river DeltA
The Tiber river deltais a wave dominated, cuspate delta
(G
alloWay
, 1975) with almost symmetrical wings. its shoreline
extends for about 12.4 km along the central Tyrrhenian coast (fig.
1). The delta has two distributary channels: the main one (fiuma-
ra grande) discharges the 80% of the whole liquid and solid load;
the secondary one (Canale di fiumicino) is the evolution of an ar-
tificial canal cut in roman times between 42 and 112 a.D. it was
definitively reopened on 1612, after a period of intermittent flow.
Delta progradation began about 6 ky B.p., but the most part of
the present cusp developed during the little ice age (lia), when
the four highest floods were recorded (1530, 1557, 1598 and 1606
a.D.). During these events Tiber discharge might have exceeded
3,500 m
3
/s (while its mean discharge is about 230 m
3
/s).
Cusp growth declined since the end of the XiX century, at
the end of the lia. This change in the evolutionary trend is cor-
roborated by the decrease of both the frequency and magnitude
of floods (the last extreme flood was recorded in 1870). in the
second half of the XX century a further reduction occurred as
a consequence the construction of scattered hydroelectric reser-
voirs, in the Tiber basin, and of river sedimentdredging.
The backshore inner edge was bounded by dune belts about
5 m high until the half of the XX century. more recently, the em-
placement of human settlements along the shore has caused the
gradual destruction of the dune system. at present, few and short
stretches of dune belts are locally preserved.
nowadays, westerly prevailing winds produce a littoral drift
that is divergent respect to the Tiber river main mouth (B
ellotti
et alii, 1994). Sands are present on the foreshore and shoreface as
deep as -5 m; sandy silt prevails on the shoreface between the -5
m and -10 m isobaths (B
ellotti
& t
ortora
, 1996).
Boreholes drilled in the foreshore and in shoreface, up to a
depth of -10 m, indicate that no significant variations in sediment
texture took place in the last 300 years (B
ellotti
et alii, 2007).
Data on solid load by the Tiber river are available in the time
interval 1873-1879, and, although discontinuously, for the last 70
years from present time (B
ersani
& B
enCivenGa
, 2001).
The comparison between solid load and changes in the delta
shoreline highlighted the following relationships:
i) the shoreline was in progradation from 1873 to 1879, when the
Tiber average solid discharge was about 10.6 x 10
6
t/y;
ii) the shoreline was stable from 1932 to 1938; when the average
solid discharge was about 7.6 x 10
6
t/y;
iii) the shoreline suffered a pronounced retreat after the Second
World War, when the average solid discharge became lower
than 7.6 x 10
6
t/y.
These remarks suggest that flow rates of about 7.6 x 10
6
t/y
would ensure delta stability (B
ellotti
et alii, 2012).
The comparison of nautical charts of different periods (isti-
tuto idrografico della marina, 1883; 1939; 1984) showed that the
delta apex average slope in the depth interval 0-10 m increased
from 0.12° to 0.26°, in the period 1883-1939. This suggests that
the decrease of the Tiber solid discharge that occurred in the same
period had already triggered the erosive phase, albeit only at the
shoreface. The subsequent further reduction of solid discharge
caused the shoreline retreat and the further increase of average
slope to 0.30°.
Several strategies have been followed since 1950 to contrast
coastal erosion. Detached breakwaters were constructed along the
ostia coast (close to the Tiber mouth) from the 50’s to 80’s. Suc-
cessively, the same protection works were made along the coast
between Canale di fiumicino and Tiber mouth (fig. 1). in ad-
dition, same groynes were built along a part of the ostia coast
during the 80
th
.
The most important defence intervention is the beach nour-
ishment that was made along the shore between the pontile and
the Canale dei pescatori in 1990. about 1.360.000 m
3
of sand and
gravel were disposed to replenish this coastal stretches that was
also protected by detached submerged barriers. other nourish-
Fig. 1 - Location of the studied area. Latium coast, Tiber River delta.
(Google Earth. July, 20, 2014)
background image
c. tArrAgoni, P. bellotti, l. DAvoli, r. rAffi & e. luPiA PAlmieri
8
Italian Journal of Engineering Geology and Environment, 2 (2014)
© Sapienza Università Editrice
www.ijege.uniroma1.it
ments were carried out between 1999 and 2005 along the entire
ostia shore. in these cases sands dredged from the sea bottom
was used for the replenishment that was only at places coupled
with the built of groynes and submerged barriers. (C
aPuto
et alii,
1993; F
ishhendler
et alii, 2012).
DAtA AnD methoDology
The new methodology proposed for the local vulnerabil-
ity assessment (lva) differs from the previous ones for two
aspects: the working scale (with its morphological and climatic
implications), and the distinction between potential and effec-
tive vulnerability. This method takes into account qualitative and
quantitative spatial variables that express morphometric and mor-
phodynamic natural factors, as well as the anthropogenic ones,
that can affect the coast susceptibility to erosion.
The choice of the working scale is crucial because it strongly
influences the selection of the variables. The regional scale stud-
ies (P
endleton
et alii, 2010; K
umar
et alii, 2010) must take into
account variables as, for example, coast typology (i.e. presence of
cliff, rocky coast or beach) and wind and sea conditions. Working
at the local scale the choice of the variables can be contemporar-
ily easier and more effective. first of all it is possible to assume
that wind and sea conditions are homogeneous; secondly coastal
morphology is likely to be similar throughout the study area. in
particular, only beaches are present in the specific case study of
the Tiber delta, which allows very peculiar and detailed morpho-
logical features can be considered as variables.
The method, based on the differentiation between potential
vulnerability (that neglects the anthropogenic factors) and effec-
tive vulnerability (that considers also the anthropogenic action and
its possible contribution to vulnerability mitigation or worsening),
has been carried out in the framework of metropolitan areas study.
The procedure followed in this work is based on the definition
of vulnerability in terms of ranking.
The application of the methodology allows the subdivision
of the studied area in sectors (each of them with homogeneous
variables) that differ from each other in the value of the Coastal
vulnerability index (Cvi). as a consequence, sectors with the
highest Cvi value can be identified as priority sites for erosion
mitigation practises and management strategies.
The methodology has the following main steps: 1 definition
of the matrix; 2 definition of weights to attributes; 3 definition and
scoring of classes; 4 aggregation of attributes; 5 classification of
vulnerability values and construction of vulnerability maps.
The following paragraphs describe the application of each
step of the methodology performed in the study area.
Definition of the local vulnerability matrix
Several factors are involved in the vulnerability analyses; they
must be selected taking into account the working scale and the
availability of data for the whole case study area. Some variables
are expressed by morphometric parameters that are connected to
wave dissipation; others are relevant to the morphodynamics of
the beach. all variables interact with one another.
according to the vulnerability conceptual framework fol-
lowed in this paper, two matrixes have been developed and com-
bined: the first one involves natural variables and the second ones
anthropic variables (Table 1).
Such matrixes have been already tested (http://www.isc.
senshu-u.ac.jp/~thc0456/eaHp/aHpweb.html) in other environ-
mental studies (s
imeoni
et alii, 2007, 2009).They are drawn by
using respectively eight and six leading diagonal terms for poten-
tial vulnerability (vp) and anthropic factors (Tab. 1).
Tide amplitude (about 40 cm) has not been considered a sig-
nificant natural variable: the Tiber delta, in fact, is a wave domi-
nated delta. Sea level rise has also been neglected because Cvi
has been performed for a short term analysis.
nourishments not coupled withthe built of detached breakwa-
ter protections have also been neglected. They, in fact, although
supply new materials to be eroded, are not able to reduce the in-
tensity of erosional processes. protected nourishments, instead,
play a double role: they increase sand supply and lower wave en-
ergy. for this reason their effects on coastal dynamics are similar
to those produced by detached breakwaters.
Definition of weights to attributes
Calculation of Cvi requires the aggregation of single vulner-
ability variables whose relative importance must be weighted. in
this case study, the weight has been expressed as a vector whose
magnitude is the relative importance of the factor and its direction
is the way it contributes to the vulnerability definition. variables
with positive weight are responsible for the increase of vulner-
ability (i.e. elevation or slope) and variables with negative weight
cause its decrease (i.e. coastal protection measures). The weight
assigned to the vulnerability factors used in the Tiber delta case
is shown in Table 2.
The consistency of the judgment matrix is then tested. The
consistency ratio (Cr), is the ratio between Consistency index
(Ci) and random Consistency index (ri); the lattershould be al-
ways <0.1 or <10%, which indicates the overall consistency of
the pair wise comparison matrix.
Definition and scoring of classes
a semi-quantitative code has been considered to quantify
the different importance of each factor; it ranges from 1 (no
importance) to 5 (critical importance). vulnerability classes rep-
resent thresholdsthat reflect variations in the extent the beach
may be affected by erosion impact. Classes have been defined
in quantitative (e.g. elevation, slope, cover data) and qualitative
(e.g. presence/absence or low/medium/high of a particular fac-
tor) categories. Quantitative classes have been defined dividing
the distribution of data into equal-sized sub-ranges (z
ald
et alii,
2006). all these classification methods establish the vulnerabil-
background image
Assessment of coAstAl vulnerAbility to erosion:
the cAse of tiber river DeltA (tyrrheniAn seA, centrAl itAly)
9
Italian Journal of Engineering Geology and Environment, 2 (2014)
© Sapienza Università Editrice
www.ijege.uniroma1.it
Tab. 1 - Vulnerability matrix applied for the assessment of coastal erosion in the Tiber delta
Tab. 2 - Weight ascribed to the vulnerability factors used to estimate the vulnerability to erosion of the Tiber Delta. CI 6.87%, CR 5.21%
*www.pcn.minambiente.it
*
background image
c. tArrAgoni, P. bellotti, l. DAvoli, r. rAffi & e. luPiA PAlmieri
10
Italian Journal of Engineering Geology and Environment, 2 (2014)
© Sapienza Università Editrice
www.ijege.uniroma1.it
ity relative thresholds that are identified considering the distri-
bution of beach data on the italian territory (F
ontolan
et alii,
2001, 2005; aa.vv., 1995). Qualitative classes have been de-
fined on the basis of information drawn from the specific litera-
ture. according to various methodologies internationally known
(G
ornitz
, 1990; a
Buodha
& W
oodroFFe
, 2006; P
endleton
et
alii, 2010), the assignation of scores to vulnerability classes has
been performed using a 1-5 scale. factors related to the greatest
vulnerability (i.e.beach minimum elevation) have the maximum
score (5) those that are relevant to the least vulnerability (i.e.
beach maximum elevation) have the minimum score (1). obvi-
ously, no class has been assigned to variables missing in the
study area.
The highest score has been ascribed to the smallest and lowest
values of beach amplitude and inland elevation, respectively that
are responsible for the enhancement of the potential vulnerability
to erosion. moreover, potential vulnerability decreases as slope of
the upper shoreface decreases (as slope decreases dissipative ac-
tion increases); for this reason, the maximum score has been as-
signed to the highest value of the upper shoreface slope. Similarly,
the potential susceptibility to coastal erosion increases for decreas-
ing sediment budget, therefore the minimum score has been as-
cribed to the lowest value of the evolutionary trend of the upper
shoreface has been assigned to tourist pressure has the maximum
vulnerability score owing to the high density of bathing establish-
ments in this area (Tab. 3); since, the presence of these facilities, in
fact, implies the beach profile alteration and loss of sediment due
to the continuous cleaning and levelling activities.
The presence of artificial protection and/or dune has been
considered a relevant factor decreasing vulnerability of beaches
to erosion (F
ontolan
et alii, 2001, 2005; o
zyurt
, 2008). from
this point of view, the maximum score value have been assigned
to the highest coastal protection measures and to the best pre-
served dunes (m
C
l
auGhlin
& C
ooPer
, 2010).
The state of preservation of the dune is defined by the analy-
sis of five factors (Tab. 4). The maximum score has been ascribed
to the variables indicating a well-status (greater height, lower
slope, larger vegetation cover, absence of break and presence of
fore-dune), and the minimum score has been assigned to the vari-
ables indicating a bad-status (P
reston
et alii, 2008).
Concerning recent and storical ytshoreline trend, the highest
vulnerability score has been attributed to retreating (t
orresan
et
alii, 2008; a
Buodha
& W
oodroFFe
, 2006).
as to the detached breakwaters, the lowest vulnerability score
(1) has been attributed to the lack of structures, the medium (3) to
submerged structures and the highest (5) to emerged structures;
score 4 has been attributed to the submerged structures combined
with nourishment.
Tab. 3 - Classes and scores applied to vulnerability factors used in the Tiber Delta in order to estimate the vulnerability of beach to the coastal erosion. 1:
least important class; 2: strongly less important class; 3: rather less important class; 4: weakly less important class; 5: most important class
background image
Assessment of coAstAl vulnerAbility to erosion:
the cAse of tiber river DeltA (tyrrheniAn seA, centrAl itAly)
11
Italian Journal of Engineering Geology and Environment, 2 (2014)
© Sapienza Università Editrice
www.ijege.uniroma1.it
Aggregation of variables
according to the conceptual framework adopted in this paper,
effective vulnerability results from the algebraic sum of the con-
tribute of both natural and anthropogenic factors:
CVI
=
V
n
+
V
a
where
CVI
= Coastal vulnerability index,
V
n
= potential vul-
nerability and
V
a
= Sum of anthropogenic factors.
in more details, the assessment of coastal vulnerability to ero-
sion is based on the analysis of multiple morphometric, morpho-dy-
namic and anthropogenic variables that are aggregated in the
CVI
.
Different approaches have been used for the assessment of
Cvi (see r
amieri
et alii, 2011 and references therein). G
ornitz
&
W
hite
(1992) and G
ornitzet
alii (1997) proposed and tested (in
terms of sensitivity analysis) different equations (considering 7
key variables) for the derivation of a
CVI
.
many environmental studies (C
ivita
, 1994; C
ivita
& d
e
m
aio
, 1997; F
ontolan
et alii, 2001, 2005) use multiple regres-
sion analysis in which the value of the dependent variable (V)
changes when any one of the independent variables (
vn
), or rela-
tive weight (kn), is modified.
in order to integrate different susceptibilities a weighted linear
combination has been used according to the following equation:
where
vn
i
= score related to the natural variable,
kn
i
= weight
associated with the natural variable,
fa
j
= score related to the
anthropogenic variable and
ka
j
= weight associated with the an-
thropogenic variable.The weights have been calculated according
to Table 2; the scores used in the assessment of the Cvi have been
derived from Table 3.
equation (2) has been applied to all the spatial units, i.e. coastal
sectors, of the study area, that have been identified on the basis of
an homogeneous distribution of data. as a result, sector size is not
constant; anyway all of them have coastline length > 100 m.
construction of vulnerability maps
To evidence the spatial variability of the Coastal vulnerabil-
ity index, the vulnerability map has been produced.
The first step has been the subdivision of the calculated Cvi
values into 5 qualitative classes (i.e. very high, high, medium,
low and very low); they have been identified by dividing the
vulnerability range (Cvi
max
- Cvi
min
) into five equal-sized sub-
ranges (z
ald
et alii, 2006).
it is to underline two aspects:
• vulnerability values higher than 5 and classified in the highest
class (5) are due to high tourist pressure and lack of defensive
works; all of them have been included in the maximum score
class (“very high”) that identifies the sectors that are likely to
be the most prone to erosion.
• negative Cvi values mark areas affected by redundant defen-
ce structures; all of them have been included in the minimum
score class (“very low”).
The vulnerability map is the main output of the developed
procedure. To represent the areal variability of vulnerability in the
studied area, two lines have been drawn parallel to the shoreline.
The landwardline indicates the classes of potential vulnerability-
while the seaward one shows those of the effective vulnerability.
each line has been divided into segments; each of them corre-
sponds to one or more sectors that have the same CVI. each seg-
ment has been coloured according to the CVI classes: from green
to red passing from minor to greater values.
according to s
alman
et alii (2004), that indicates the radius of
influence of Coastal erosion (riCe area) in a buffer of 500 m, the
local vulnerability assessment has been performed for the coastal
areas located within 500 m from the shoreline (fig. 2). obviously
only the variables that are strictly related to the beach must be taken
into account to evaluate beach and not coastal vulnerability.
results AnD Discussion
The results of the proposed methodology are shown in fig. 2.
The results attained for the studied area evidence the presence
of sectors with potential vulnerability values ranging from 3.1
to 4.4; therefore the whole area has sectors falling in “high” and
“very high” classes. This situation is representative of the wide
spreading of erosion processes.
Tab. 4 - Classes and scores applied to vulnerability factors used in the Tiber Delta in order to estimate the vulnerability of beach to the erosion
(1)
(2)
background image
c. tArrAgoni, P. bellotti, l. DAvoli, r. rAffi & e. luPiA PAlmieri
12
Italian Journal of Engineering Geology and Environment, 2 (2014)
© Sapienza Università Editrice
www.ijege.uniroma1.it
The whole area is characterized by low and very low beach
altitude (classes 5 and, subordinately, 4), upper shoreface slope
(>0.008) and inland elevation (only southern sectors fall in class
3). Sediment budget is another relevant factor. it contributes to
the higher vulnerability scores of the shoreline segments char-
acterized by erosional processes: the marked shoreline retreats
along the delta apex have been evaluated both during the recent
period 1994-2010, and the historical period 1954-2010.
The highest values of potential vulnerability have been ob-
tained near Canale di fiumicino; they refer to areas characterized
by very small and very low beach, erosive upper shoreface (class
4) and very low inland altitude (class 5).
Taking into account anthropogenic factors, the whole area is
characterized by high tourist pressure (score 5) and widespread
presence of artificial protections that deeply influence the effec-
tive vulnerability.The focene and fiumicino areas (located to the
north of the Canale di fiumicino) have the highest effective vul-
nerability; their CVI values, in fact, belong to the classes 4 and 5.
moving to the South, the isola Sacra area, located between the
Canale di fiumicino and the Tiber mouth, has “low”, and subor-
dinately “medium”ve, due to the presence of detached breakwa-
ter; the CVI values belong mainly to the class 2.
The massive presence of defensive structures in the rome
municipality contrasts the possible increase of effective vulner-
ability due to the huge anthropic pressure and determines low
values of Cvi. as a result, the coastal stretch that extends from
the Tiber mouth southward has the lowest vulnerability. more in
detail, Cvi values are included within class 2 (from the Tiber
mouth to pontile della vittoria) and 1 (from pontile della vittoria
to the southern edge of the study area).
figure 3 shows the percentage of vulnerability classes for the
whole studied area and for each municipality; it shows what is the
coastal municipality having a higher number of vulnerable sectors.
The first column of figure 3 shows that about 40% of the
total riCe coastline has “very high” potential vulnerability (v
p
)
and 60% of it has “high” v
p
. Taking into account the ve bar graph
(second column in fig. 3), the percentage of riCe area coastline
with “very high” vulnerability decreases from 40% to 21%.
Several sectors that have“high” v
p
(from >3 to 4) decrease
their vulnerability score: in the rome municipality (fig. 2) that
represent the 38% of total studied area, the CVI value obtained
fall under class 2 (16%) and class 1 (22%).
This statistic clearly indicates that at present the fiumicino
municipality is the most vulnerable to coastal erosion.
finAl remArKs
The vulnerability assessment methodology proposed in this
paper can take into account many detailed factors and variables
that are connected to beach erosion, as it has been expressly elab-
orated for the local scale investigations.
for this reason the local vulnerability assessment represent
an important and useful tool to single out the most vulnerable
Fig. 2 - Map of V
p
(landward line) and Ve (seaward line) distribution. Table of length of sectors (m), scores for each factors (V
1
, V
2
, etc.) and potential and
effective vulnerability (V
p
and V
e
).ΣAF is the sum of Anthropic factors (Tab. 3).
background image
Assessment of coAstAl vulnerAbility to erosion:
the cAse of tiber river DeltA (tyrrheniAn seA, centrAl itAly)
13
Italian Journal of Engineering Geology and Environment, 2 (2014)
© Sapienza Università Editrice
www.ijege.uniroma1.it
coastal areas and to support decision makers for territory plan-
ning and management.
The Coastal vulnerability index (CVI) is an outline of weight-
ed linear combination, therefore it allows not only the identifica-
tion of the most vulnerable coastal stretches but also the vari-
ables, and therefore the factors, that most influence the erosional
processes they undergo. in other words, this procedure can help
the choice of the variables that must be considered in the erosion
mitigation programmes.
Considering that the classes of each variable have been defined
taking into account the distribution of data on the italian territory,
the proposed CVI could be applied in other italian sandy beach
systems, thus allowing the comparison between different areas.
moreover the values of CVI (expressing the effective vulner-
ability) compared with potential vulnerability (v
p
) can evidence
the important role of anthropic factors that are able to reduce or
enhance the negative effects of coastal erosional processes.
The bi-dimensional visualization of the results in the vulnera-
bility map affords an efficacious tool capable to transfer immedi-
ately information to stakeholders and decision makers in order to
support them in the planning of appropriate adaptation measures.
if implemented by introducing specific variables that take into
account long-term environmental changes (i.e. relative sea level
rise) and recalibrating the weights of the variables, this method-
ology can also be applied for the prediction of future scenarios.
obviously, the proposed methodology is suitable to be ap-
plied to sandy beach coasts in those areas,like the studied one,
characterized by microtidal regime.
AcKnoWleDgements
This research was funded by the 7
th
framework program eu-
ropean project n. 244251: Solutions for environmental Contrasts
in Coastal areas (SeCoa).
Fig. 3 - Distribution of the percentages of stretches of coast associated with each vulnerability class. Each pair of columns shows the distribution of potential
(left) and effective vulnerability (right). On the left, columns show data referred to the whole studied area (12.4 km); moving to the right data referred
to Fiumicino Municipality (7.7 km) and Rome municipality (4.7 km) are shown
references
a
Buodha
P. & W
oodroFFe
C.d. (2006.) - Assessing vulnerability of coasts to climate change: A review of approaches and their application to the Australian
coast. in: GIS for the Coastal Zone: a selection of papers from Coast GIS 2006. W
oodroFFe
Cd, B
ruCe
e, P
uotinen
m & F
urness
ra (eds). australian
national Centre for ocean resources and Security university of Wollongong: Wollongong, australia, 458 pp.
aa.vv. (1995) - Atlante delle spiagge italiane. Dinamismo - Tendenza evolutiva - Opere umane. Progetto Finalizzato Conservazione del Suolo - Dinamica
dei Litorali. Cnr-miur, SelCa, florence, italy.
B
ellotti
P., C
alderoni
G., C
arBoni
m.C., d
i
B
ella
l., t
ortora
P., v
aleri
P. & z
ernitsKaya
v. (2007) - Late Quaternary landscape Evolution of the Tiber
background image
c. tArrAgoni, P. bellotti, l. DAvoli, r. rAffi & e. luPiA PAlmieri
14
Italian Journal of Engineering Geology and Environment, 2 (2014)
© Sapienza Università Editrice
www.ijege.uniroma1.it
River delta plain (Central Italy): new evidence from pollen data, biostratigraphy and
14
C dating. Zeitschrift für geomorphologie, Berlin, Stuttgart,
germany, 51 (4): 505-534.
B
ellotti
P. & t
ortora
P. (1996) - I sedimenti sul fondale del delta del Fiume Tevere. Bollettino della Società geologica italiana, roma, 115 (2): 449-458.
B
ellotti
P., C
aPuto
C. & v
aleri
P. (2012) - Delta types along the coast of the Italian Peninsula. Considerations on evolutive factors. in: atti del Quarto
Simposio internazionale “Il Monitoraggio Costiero Mediterraneo: problematiche e tecniche di misura”. Cnr, istituto di Biometeorologia (ed.),
firenze.Curatore: f. Benincasa. livorno,12-13-14 June 2012, 205-212.
B
ellotti
P., C
hioCCi
F.l., m
illi
s., t
ortora
P. & v
aleri
P. (1994) - Sequence stratigraphy and depositional setting of the Tiber Delta; integration of high
resolution seismic, well logs and archaeological data. Journal of Sedimentary petrology, 64 (3b): 416-43 u.S.a. published online august 15, 1994.
Doi:10.1306/D4267fDC-2B26-11D7-8648000102C1865D.
B
ersani
P. & B
enCivenGa
m. (2001) - Le piene del Tevere a Roma dal V secolo a. C. all’anno 2000. Dipartimento per i Servizi Tecnici nazionali, Servizio
idrografico e mareografico nazionale, presidenza del Consiglio dei ministri. rome, italy, 1-18.
C
aPuto
C., C
hioCCi
F.l., F
errante
a., l
a
m
oniCa
G.B., l
andini
B. & P
uGliese
F. (1993) - La ricostruzione dei litorali in erosione mediante ripascimento
artificiale e il problema del reperimento degli inerti. in a
minti
P. & P
ranzini
e.(eds.) - La difesa dei litorali in Italia. autonomie ed., rome, 121-151.
C
ivita
m. (1994) - Le carte della vulnerabilità degli acquiferi all’inquinamento: teoria e pratica. Quaderni di tecniche di protezione ambientale. pitagora
press, Bologna, italy, 7: 325 pp.
C
ivita
m. & d
e
m
aio
m. (1997) - SinTaCS. Quaderni di tecniche di Protezione Ambientale. pitagora press, Bologna, italy, 60: 191 pp.
d’a
lessandro
l., d
avoli
l., l
uPia
P
almieri
e. & r
aFFi
r. (2002) - Natural and anthropogenic factors affecting the recent evolution of beaches in Calabria
(Italy). applied geomorphology: Theory and practice. a
llison
r.J. (e
d
.), John Wiley & Sons, ltd, 397-427.
eea (2013) - Trends and projections in Europe 2013 - Technical report. office for official publications of the european Communities,luxembourg, 10:
139 pp. iSSn 1725-9177.
e
nGelen
G., u
ljee
, i. & W
hite
r. (1998) - Report & SIMLUCIA User Manual Report to UNEP CAR/RCU. united nations environment programme
Caribbean regional Coordinating unit, Kingston, Jamaica.
F
isChhendler
i., K
arasin
o. & r
uBin
z. (2012) - Handbook for institutional responses to coastal hazards. a. m
ontanari
(e
d
.), roma, (iT). iSBn: 978-88-
95814-74-2. Doi: 10.7357/Digilab-10047. http://digilab-epub.uniroma1.it/index.php/SeCoa/issue/view/4
F
ontolan
g. (2001) - Forecast and prevention plan: Risk of flooding.province of venice, Soil and Defence unit, Trieste, 92 pp.
F
ontolan
g. (2005) - Forecast and prevention plan: Risk of flooding, updating.province of venice, Soil and Defence unit, Trieste, 109 pp.
G
alloWay
W.e. (1975) - Processes framework for describing in the morphologic and stratigraphic evolution of deltaic depositional system. in: Deltas,
Model for Exploration. Broussard Houston geological Society: Houston, Texas, uSa, 87-98.
G
ornitz
v.m. (1990) - Vulnerability of the East Coast, U.S.A. to future sea-level rise. proceedings of the Skagen Symposium, Journal of Coastal research,
Special issue, 9: 201-237.
G
ornitz
v.m., B
eaty
t.W. & d
aniels
r.C. (1997) - A coastal hazards database for the U.S. West Coast. ornl/CDiaC-81, nDp-043 C. oak ridge
national laboratory, oak ridge, Tennessee, u.S., august 1992.
G
ornitz
v.m., d
aniels
r.C., W
hite
t.W. & B
irdWell
K.r. (1994) - The development of a coastal risk assessment database for the U.S. southeast: erosion
and inundation from sea level rise. in F
inKle
C.W. Jr. (e
d
.). Coastal hazards: perception, susceptibility and mitigation. Journal of Coastal research,
Special issue, 12: 327-338.
G
ornitz
v.m. & W
hite
t.W. (1992) - A coastal hazards database for the U.S. East coast. ornl/CDiaC-45, nDp-043 a. oak ridge national laboratory,
oak ridge, Tennessee, u.S., august 1992.
G
ornitz
v.m., W
hite
t.W. & C
ushman
r.m. (1991) - Vulnerability of the U.S. to future sea-level rise. in: proceedings of Seventh Symposium on Coastal
and ocean management. long Beach, Ca (uSa), 2354-236868.
h
enrotte
J. (2008) - Implementation, validation and evaluation of a Quasi 3D model in Delft3D. m.Sc. thesis at Delft, university of Technology, faculty
of Civil engineering and geosciences, section of Hydraulic engineering. Delft, The netherlands, 119 pp.
h
inKel
J. (2005) - DIVA: an iterative method for building modular integrated models. advances in geosciences, 4: 45-50. Doi:10.5194/adgeo-4-45-2005.
h
inKel
j., n
iCholls
r., v
aFeidis
a., t
ol
, r. & a
vaGianou
T. (2010) - Assessing risk of and adaptation to sea level rise in the European Union: an application
of DIVA. mitigation and adaptation Strategies for global Change, 15: 703-719. Doi:10.1007/s11027- 010-9237-y.
h
su
y.l., d
yKes
j.d., a
llard
r.a. & K
aihatu
j.m. (2006) - Evaluation of Delft3D Performance in nearshore flows. naval research laboratory, nrl/
mr/7320-06-8984.
ipCC (2013) - Climate Change 2013. The Physical Science Basis. Contribution of Working group i to the fifth assessment report of the intergovernmental
panel on Climate Change. s
toCKer
t.F., Q
in
d., P
lattner
G.K., t
iGnor
m., a
llen
s.K., B
osChunG
j., n
auels
a., X
ia
y., B
eX
v., m
idGley
P.m. (e
ds
.).
Cambridge university press, Cambridge, united Kingdom and new York, nY, uSa, 1535.
i
stituto
i
droGraFiCo
della
m
arina
(1883) - NauticalCharts 1:30,000, Sheet 124. istituto idrografico della marina, genova, italy.
background image
Assessment of coAstAl vulnerAbility to erosion:
the cAse of tiber river DeltA (tyrrheniAn seA, centrAl itAly)
15
Italian Journal of Engineering Geology and Environment, 2 (2014)
© Sapienza Università Editrice
www.ijege.uniroma1.it
i
stituto
i
droGraFiCo
della
m
arina
(1939) - NauticalCharts 1:30,000, Sheet 124. istituto idrografico della marina, genova, italy.
i
stituto
i
droGraFiCo
della
m
arina
(1984) - NauticalCharts 1:30,000, Sheet 124. istituto idrografico della marina, genova, italy.
K
enny
G.j., W
arriCK
r.a., C
amPBell
B.d., s
ims
G.C., C
amilleri
m., j
amieson
P.d., m
itChell
n.d., m
C
P
herson
h.G. & s
alinGer
m.j. (2000) - Investigating
climate change impacts and thresholds: an application of the CLIMPACTS integrated assessment model for New Zealand agriculture. Climatic Change,
46: 91-113.
K
lein
r.j.t. & n
iCholls
r.j. (1999) - Assessment of coastal vulnerability to climate change. ambio, 28 (2): 182-187.
K
umar
t.s. & m
ahendra
r.s., n
ayaK
s., r
adhaKrishnan
K., s
ahu
K.C. (2010) - Coastal Vulnerability Assessment for Orissa State, East Coast of India.
Journal of Coastal research, 26: 523-534.
m
C
l
auGhlin
s. & C
ooPer
j.a.G. (2010) - A multi-scale coastal vulnerability index: a tool for coastal managers? environmental Hazards, 9: 1-16. earthscan
iSSn: 1878-0059.
m
C
l
eod
e., P
oulter
B., h
inKel
j., r
eyes
e. & s
lam
r. (2010) - Sea level rise impact models and environmental conservation: a review of models and their
application. ocean & Coastal management, 53: 507-517.
m
oCenni
C., C
asini
m., P
aoletti
s., G
iordani
G., v
iaroli
P. & z
ald
`
ivar
C
omenGes
, j. (2009) - A decision support system for the management of the Sacca
di Goro (Italy). in m
arComini
a., s
uter
G.W. ii, C
ritto
a. (eds): Decision Support Systems for Risk-Based Management of Contaminated Sites, .
Springer, Berlin - Heidelberg, germany, 399- 422.
m
oKreCh
m., h
anson
s., n
iCholls
r. j., W
olF
j., W
alKden
m., F
ontaine
C.m., n
iCholson
C
ole
s., j
ude
s.r., l
eaKe
j., s
tansBy
P., W
atKinson
a.r.,
r
ounsevell
m.d.a., l
oWe
j.a. & h
all
j.W. (2009) - The Tyndall coastal simulator. Journal of Coastal Conservation, 15: 325-335. Doi:10.1007/
s11852-009- 0083-6.
n
iCholls
r.j. & K
lein
r.j.t. (2005) - Climate change and coastal management on Europe’s coast. in v
ermaat
j., B
ouWer
l., t
urner
K., s
alomons
W.
(eds.). Managing European Coasts: Past, Present and Future. Springer, Berlin - Heidelberg, germany, 199-226.
o
zyurt
G., e
rGin
a. & e
sen
m. (2008) - Indicator based coastal vulnerability assessment model to sea level rise. in: The proceedings of the Seventh
international Conference on Coastal and port engineering in Developing Countries CopeDeC vii “Best practices in the Coastal environment”. 24-28
february 2008, Dubai, uae, 2008.
P
endleton
e.a., B
arras
j.a., W
illiams
s.j. & t
WiChell
d.C. (2010) - Coastal vulnerability assessment of the Northern Gulf of Mexico to seaLevel rise and
coastal change. u.S. Department of the interior u.S. geological Survey, report Series, 2010-1146.
P
reston
B.l., s
mith
t.F., B
rooKe
C., G
orddard
r., m
easham
t.G., W
ithyComBe
G., m
Cinnes
K., a
BBs
d., B
everidGe
B. & m
orrison
C. (2008) - Mapping
Climate Change Vulnerability in the Sydney Coastal Councils Group. prepared for the Sydney Coastal Councils group.
r
amieri
e., h
artley
a., B
arBanti
a., d
uarte
s
antos
F., G
omes
a., h
ilden
m., l
aihonen
P., m
arinova
n. & s
antini
m. (2011) - Methods for assessing
coastal vulnerability to climate change. european Topic Centre on Climate Change impact, vulnerability and adaptation, Technical paper, 1/2011,
european environment agency, Bologna (iT), 93 pp.
s
alman
a., l
omBardo
s. & d
oody
P. (2004) - Living with coastal erosion in Europe: Sediment and Space for Sustainability, PART III - Methodology for
assessing regional indicators. e.u.C.C.http://repository.tudelft.nl/view/hydro/uuid%3a483327a3-dcf7-4bd0-a986-21d9c8ec274e/
s
Chirmer
m., s
ChuChardt
B., h
ahn
B., B
aKKenist
s. & K
raFt
d. (2003) - KRIM: Climate change risk construct and coastal defence. DeKlm german
Climate research programme. proceedings 269273, 269-273.
s
imeoni
u. & C
orBau
C. (2009) - A review of the Delta Po evolution (Italy) related to climatic changes and human impacts. geomorphology, 107: 64-71.
s
imeoni
u., F
ontolan
G., t
essari
u. & C
orBau
C. (2007) - Domains of spit evolution in the Goro area, Po Delta, Italy. geomorphology, 86: 332-348.
s
terr
h., K
lein
r.j.t. & r
eese
s. (2003) - Climate Change and coastal zones: an overview of the state of theart on regional and local vulnerability
assessment. in: Climate Change and the mediterranean: Socio-economics of impacts, vulnerability and adaptation, 2003.http://www.feem.it/getpage.as
px?id=765&sez=publications&padre=73
t
orresan
s., C
ritto
a., d
alla
v
alle
m., h
arvey
n. & m
arComini
a. (2008) - Assessing coastal vulnerability to climate change: comparing segmentation
at global and regional scales. Sustainable Science, 3: 45-65. Doi: 10.1007/s11625-008-0045-1.
t
orresan
s., C
ritto
a., r
izzi
j. & m
arComini
a. (2012) - Assessment of coastal vulnerability to climate change hazards at the regional scale: the case study
of the North Adriatic Sea. natural Hazards and earth System Sciences, 12: 2347-2368.
W
arriCK
r.a. (2009) - Using SimCLIM for modelling the impacts of climate extremes in a changing climate: a preliminary case study of household water
harvesting in Southeast Queensland. in: “proceedings ofthe 18
th
World imaCS Congress and moDSim09 international Congress onmodelling and
Simulation,July 2009”. a
nderssen
r.s., B
raddoCK
r.d., n
eWham
l.T.H. (eds.). Cairns, australia, 2583-2589.
W
arriCK
r.a., y
e
W., K
ouWenhoven
P., h
ay
j.e. & C
heatham
C. (2005) - New developments of the SimCLIM model for simulating adaptation to risks
arising from climate variability and change. in: “moDSim 2005. international Congress on modelling and Simulation: advances and applications for
management and decision making. December 2005”. modelling and Simulation Society of australia and new Zealand, melbourne, 551-558.
z
ald
a.e., s
helly
s. & W
ade
t. (2006) - A to Z GIS: An Illustrated Dictionary of Geographic Information Systems. articles (libraries), paper 144,
background image
c. tArrAgoni, P. bellotti, l. DAvoli, r. rAffi & e. luPiA PAlmieri
16
Italian Journal of Engineering Geology and Environment, 2 (2014)
© Sapienza Università Editrice
www.ijege.uniroma1.it
esripress, 2006.
annuario.isprambiente.it
http://www.isc.senshu-u.ac.jp/~thc0456/eaHp/aHpweb.html
Received August 2014 - Accepted October 2014
Statistics