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| Objectives
The TIDE project will develop models of
morphological and ecological dynamics in tidal embayments
to describe the coupled evolution of landform and ecology.
Coastal wetland areas, such as lagoons
and estuaries, are complex and delicate environments subject
to rapid morphological and ecological evolution often in
response to strong human interference. Beside their evident
ecological importance, coastal wetland areas are often the
location of important human settlements and the centre of
relevant social/cultural interests.
The reasons for the great ecological value of lagoons and
estuaries are precisely the reasons that make them extremely
difficult natural systems to study and understand. The richness
of the interactions between ecological components and with
the complex of physical processes occurring in tidal environments
requires a holistic approach to the study of the system
as a whole rather than as a collection of parts. This, in
turn, requires an interdisciplinary approach and the close
collaboration of researchers from a wide range of scientific
fields. This observation was also emphasised by the Demonstration
Programme of D.G. XI on Integrated Coastal Zone Management,
whose recommendations stress the need for a strategy based
on the understanding of interacting processes (physical,
biological and human) through a multi-disciplinary approach.
The construction of an effective policy for the management
and preservation of coastal humid areas requires a greater
understanding of their environments and particularly of
their dynamics, enabling us to predict environmental changes
in response to human pressure (social, agricultural, industrial,
etc.) and to natural or induced 'climate' changes.
However, we do not yet possess sufficiently
complete or holistic theories on tidal systems evolution
since past modelling efforts have, by necessity, concentrated
on describing individual components separate from the whole.
Physicists and engineers have described the hydrodynamics,
geomorphologists the existing, 'static', landforms and biologists
the ecological diversity or energy flow, with no direct
description of their interactions. Further, we still lack
vital information for the understanding of some of the key
processes (e.g. sediment transport, erosion and deposition,
vegetation dynamics, etc.) shaping the morphology of the
system.
We are realising that morphological evolution
in tidal environments is not simply related to physical
processes, such as sediment dynamics induced by hydrodynamic
patterns and residual circulation, but is also crucially
dependent on ecological dynamics, such as development of
vegetation and biological status of the sediments (e.g.
microphytobenthos presence and distribution, bioturbation,
biostabilisation). It is only by developing models incorporating
both 'living' and 'non-living' components that we will be
able to construct a realistic and reasonably complete picture
of tidal environments dynamics both on the short and the
long time scale. The TIDE project can advance rapidly in
this direction by taking, as a starting point, the experience
gained through regional (e.g. LISP, LOIS) and EU (Eloise,
SWAP, INTRMUD, BIOPTIS, ECOFLAT) interdisciplinary projects.
The main objective of the proposed research
is therefore the development and validation of interacting
physical and ecological models to describe the morphological
development of saltmarsh and upper intertidal systems based
on observed landforms and ecosystem properties derived from
remote sensing and ground truthing.
The development of the models described
imposes some important observational requirements which
have not yet been met by existing experimental knowledge.
We believe that, in order to achieve the objectives described,
we must follow a systematic approach which advances from
the large body of information already available. This will
involve observations on a temporal and spatial scale which
can only be achieved through remote sensing techniques.
The scales of interest range, spatially, from the order
of tens of centimetres to the order of kilometres and temporally
from the tidal to the annual time scale. Thus the planned
remote observations will, in contrast to most previous remote
sensing applications, cover time scales from weeks to years,
allowing the investigation of system change occurring on
relatively rapid temporal scales. The development of the
observation techniques required by the models will also
be of great use in management and monitoring practices,
with important implications for the preservation of tidal
environments.
Using this innovative approach, the scientific and technological
objectives of the TIDE project may be identified as follows:
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| TIDE OBJECTIVES:
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- Formulation of improved models for the evolution
of tidal forms.
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These models will have to include both the evolution
of tidal channels features (e.g. branching and meandering)
and salt-marsh morphology and the coupled co-evolution
of such forms and the ecological system (e.g. vegetation).
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- Development of remote observation techniques suitable
to tidal environments.
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In particular we plan to develop objective algorithms
for the retrieval of tidal network patterns and salt-marsh
morphology from accurate (laser) topographies and from
hyperspectral data. Further, the project will require
the evolution of accurate vegetation (salt marsh plants,
macroalgae and microphytobenthos) classification techniques,
to investigate the interactions between landforms and
ecosystem structure. Beside their direct scientific
interest, the techniques developed will constitute new
tools for the management of tidal environments.
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- Construction of a freely accessible data-base of
observations and models on tidal environments.
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This objective is a very important step in the dissemination
of knowledge and the sharing of research results on
tidal systems, which is necessary for the rapid scientific
development of the field and for a greater awareness
of policy makers and of the general public.
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- Evaluation of socio-economic understanding of the
importance of tidal environments.
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Societal awareness of the role of tidal environments
in maintaining the socio-economic health of coastal
systems is relatively poor. The scientific programme
within TIDE will be closely linked to a data gathering
programme initially examining public awareness of coastal
issues and then designed to involve, enhance and resource
knowledge of current threats and opportunities in coastal
management.
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| Past scientific efforts to
understand and model tidal systems have, by necessity, dealt
with just a few of their components and either parameterised
the interactions with other components or assumed them to
be "frozen" in time. The TIDE project aims at
developing current models to include the description of
the main interacting components: hydrodynamics, sediment
dynamics, ecological dynamics. This is a necessary step
for the development of useful predictive and management
tools and requires improved observations, particularly in
relation to the spatial and temporal resolution of the measurements.
In the modelling/observational characterising the TIDE project
particular efforts are planned in the following fields:
UP |
| Development
of models for the evolution of tidal systems |
In
contrast to other geomorphic systems, such as rivers and
river networks (Rodriguez-Iturbe and Rinaldo, 1997; Blondeaux
and Seminara, 1985), tidal system geometry and characteristics
have been described in the literature (Myrick and Leopold,
1963; Pestrong, 1965; Fagherazzi et al., 1999) but have
received relatively little attention as far as quantitative
geomorphological dynamics are concerned. The proposed research
aims to pursue the description of the evolution of the system
by modelling the coupled co-evolution of its morphological
and ecological components. Modelling approaches to tidal
channel dynamics, based on first principles, have recently
been put forward in the literature (Seminara and Tubino,
1998; Schuttelaars and De Swart, 1999) and will be further
improved. We intend to advance this promising and exciting
area of research within the framework of the project by
refining existing models and by explicitly including the
interaction between salt-marsh dynamics and vegetation dynamics.
UP |
| Models
of sediment transport in tidal systems |
Although in
the last two decades the improved knowledge of sediments
dynamics has allowed to gain a better insight into many
geomorphologic processes, at present the long-term modelling
of the morphologic evolution of estuarine environments is
still in an initial stage (e.g. De Vriend et al., 1993).
This is due to the difficulty of coupling physical processes
such as the hydrodynamics and the morphologic evolution
of tidal environments, which strongly interact but work
at rather different time scales. So far the long-term modelling
has been usually tackled by introducing relatively rough
and conceptual approximations of the various physical mechanisms
involved in the problem. As a first step towards the development
of more physically based models of estuarine and lagoon
morphodynamic we intend to study the long-term equilibrium
characteristics of the longitudinal profile and cross-sectional
width of tidal channels by fully coupling the classic shallow
water equations for the flow field (i.e., the de Saint Venant
equations) and the sediment balance equation (Exner) for
the bottom evolution.
The proposed research will also include the development
of a long-term morphodynamic model of sediment transport
in a macrotidal embayment using assimilation of remotely
sensed data. At present, field monitoring of coastal morphodynamics
is the best and most reliable method of process assessment
over the long term. A method that integrates short-term
knowledge based on physical principles with knowledge of
longer-term behaviour from field observations could provide
improved morphodynamic predictions. To test this, we propose
to investigate the assimilation of a temporal sequence of
field data obtained by remote sensing into a morphodynamic
model, in order to predict future changes and estimate model
parameters.
UP |
| Retrieval
of tidal network morphology |
One of the main
priorities for modelling and monitoring tidal systems is
related to the need for accurate, frequently updated, information
on the topography, hydrodynamics and sediment transport
at the scales of interest: O(10-1 m)¸O(103 m) for
the spatial domain and O(1 obs/yr) ¸ O(10 obs/yr)
for the temporal domain. The extraction of the planar and
bathymetric structure of tidal systems at the prescribed
scales is critical. We plan to employ, at chosen sites,
airborne laser scanners and hyperspectral sensors operating
in the visible and near/middle infrared spectral intervals.
Current laser altimeters are capable of obtaining Digital
Elevation Models with a resolution of 1 m and a vertical
accuracy of about 20 cm and will allow the determination
of the bathymetry in emerged areas. Finally, algorithms
for the automatic extraction of the network of connected
channels from high spatial and spectral resolution images
will be developed. Current, improved, algorithms may be
further refined, particularly to obtain the network structure
solely from planar (i.e. non-bathymetric), more widely available,
information.
UP |
| Vegetation
and microphytobentos classification from hyperspectral data |
Salt marsh and
salt marsh vegetation development are very strongly linked
and are mainly determined by sediment supply and the frequency
and duration of inundation, which, in turn, depend on elevation,
position, local and overall topography of the marsh. Current
theories describe marsh development through biological succession,
and progressive stabilisation, of the developing marsh initially
by microbiota (including cyanobacteria and microalgae; Underwood
and Smith, 1999) and then by marsh species (pioneered by
Salicornia and Spartina). An equilibrium develops such that
as the marsh level rises, tidal waters cover the site less
frequently and sediment deposition becomes reduced. This
hypothesis needs a quantitative justification linking the
topographic features of salt marshes to their stability
and the presence and distribution of vegetation. Unfortunately
very little quantitative information is known about vegetation
distribution and its temporal dynamics. We plan to obtain
the needed space-time vegetation distributions by developing
accurate classification procedures applied to frequent hyperspectral
observations on temporal scales ranging from weeks to years.
Standard vegetational indices can be used to estimate the
coverage of halophytes, macrophytic algae (mainly Ulva and
Entermorpha spp), marine macrophytes (e.g Zostera spp.)
and the microphytobenthos (dominated by Bacilliariophyceae
and cyanobacteria) but more exacting analysis can be applied
to separate these groups on the basis of remote sensing
signal. Natural single species stands of each type of assemblage
will be used to obtain spectral signatures characteristic
of each vegetation type, to provide "end-member"
spectra for analysis of mixed systems. The spectral signature
will vary depending on the pigment compliment of the groups
(Wiltshire et al 1998). Characteristic groups of algae can
be distinguished from each other and from higher plants
by the variation in absorbency caused by accessory pigments
such as chl c, fucoxanthin and, in the case of cyanobacteria,
zeoxanthin. The possibility of broad characterisations of
marsh vegetation cover through multispectral data has been
explored in the literature but the potential for accurate
vegetation classification based on hyperspectral data has
only recently been indicated (e.g. Thomson et al., 1998)
and will be further improved yielding an important deliverable
of the TIDE project. Finally, through the close link between
vegetation type and marsh elevation, accurate digital elevation
models of the salt marshes will be produced. The use of
vegetation mapping to investigate the elevation structure
of tidal environments is an entirely original concept which
will be developed by the TIDE project.
UP |
| Evaluation
of socio-economic implications of anthropogenic pressure on
intertidal areas |
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ongoing decline in the "quality" of coastal zones
and estuarine systems has been identified as an area worthy
of priority action under the 5th Environmental Action Programme
(COM(95)511 COM(97)744). Upper mudflats and, particularly
salt marsh regions, are sensitive systems open to demographic
pressure. The EU policy regarding the degradation of coastal
systems is based on "a high level of protection, the
precautionary principles, preventive action, rectification
of damage at source" (source in Article 130r of the
Treaty). The TIDE project will determine the rate of change
in evolution of these systems where exposed to anthropogenic
pressure. The socio-economic importance of these systems
is not easily quantified (see Constanza 1997) but it is
clear that land use patterns (e.g. grazing rights, fertilisation
[run-off or targeted]) and tourism have an extreme impact
on these marginal systems.
The aims of this work will be to:
· Determine the public awareness of
marsh economic and environmental importance.
· To investigate the links between agricultural practice
and system degeneration.
· To examine the spatial and temporal dimensions
of these linkages.
· To investigate farmers' and tourist attitudes and
likely responses to potential restrictions or prohibitions
on marsh exploitation.
· To examine if education and information using future
modelled predictions of habitat change inform those responses.
· To investigate the socio-economic and land use
implications of those responses.
· To investigate the relationship between the European
Union's agricultural, regional and environmental policies.
UP |
| Construction
of a freely accessible data-base of observations on tidal
environments |
There is no
scientific advancement without communication, as this ensures
review of research results, allows further elaboration of
new concepts, contributes to a greater participation of
the general public and makes new knowledge available for
decision makers. To this end, the publicising of the work
progress and results through scientific publications and
also by establishing a freely accessible data base on tidal
environments is an integral part of the project. The data
base will be freely accessible through a web site and will
contain the results and information regarding the research
carried out within the project as well as the current literature
on the subject. The site will be hosted at a well-known
cultural institution which will promote meetings and seminars
on the subject as well as publicise the web site and the
related data-base in the scientific community and in the
general public at large. Particular efforts will be made
to illustrate the possibilities of such a tool to decision
makers as an essential aid for designing environmental policies.
UP |
| References
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| Black, K. S.,
Paterson, D. M., and Cramp, A. (1998). Sedimentary Processes
in the Intertidal Zone. Geological Society, London, Special
Publications. 139, 409 pp. 1998
Blondeaux, P., and G. Seminara, A unified bar-bend theory
of river meanders, J. Fluid. Mech., 157, 449-470, 1985.
COM(95)511 - Communication from the Commission to The Council
and the Parliament on the integrated management of coastal
zones
COM(97)744- Communication from the Commission to the Council
and the Parliament - Report on the progress of the integrated
coastal zone management demonstration programme
De Vriend, H.J., Capobianco, M., Chesher, T., de Swart,
H.E., Latteux, B. & Stive, M.J.F., 1993, Approaches
to long-term modelling of coastal morphology: a review.
Coastal Engineering, 21, 225-269.
Dyer, K.R. (1998) The typology of intertidal mudflats. In:
(Black, K. Paterson, D.M. and Cramp. A, eds). Sedimentary
Processes in the intertidal zone. Geological Society, London,
Special Publications, 139, 11-24, 1998
Fagherazzi, S., A. Bortoluzzi, W. E. Dietrich, A. Adami,
S. Lanzoni, M. Marani, A. Rinaldo, 1999. Tidal networks
1. Automatic network extraction and preliminary scaling
features from DTMs, Water Resour. Res., vol. 35 No. 12,
3891-3904, 1999.
Myrick, R.M., and L.B. Leopold, Hydraulic geometry of a
small tidal estuary, U.S. Geol. Surv. Prof. Pap.,422-B,
18 pages, 1963.
Rodriguez-Iturbe, I., A. Rinaldo, Fractal River Networks:
Chance and Self-Organization, Cambridge University Press,
New York, 1997
Pestrong, R., The development of drainage patterns on tidal
marshes, Stanford Univ. Publ. Geol. Sci., 10, 87 pages,
1965.
Seminara, G. and M. Tubino, 1998. On the formation of estuarine
free bars. In Physics of Estuaries and Coastal Seas, Eds.
Dronkers J. and Scheffers M., A.A.Balkema, pp. 345-353.
Shuttelaars, H.M., and H. E., De Swart, Initial formation
of channels and shoals in a short embayment, J. Fluid Mech.,
386, p. 15-42, 1999.
Thomson, A. G., Fuller, R. M., Sparks, T. H., Yates, M.
G., Eastwood, J. A., 1998. Ground and airborne radiometry
over intertidal surfaces: waveband selection for cover classification,
Int. J. of Remote Sensing, vol. 19, 6: 1189-1205.
Underwood, G.J.C. 1997. Microalgal colonisation in a saltmarsh
restoration scheme, Estuarine Coastal and Shelf Science,
44 (4), 471-481, 1997
Wiltshire K.H. Algae and associated pigments of intertidal
sediments, new observations and methods. Limnologica, x,
1998.
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