A GIS tool for Coastal Wave Propagation
Catarina Zózimo, Juana Fortes, Nuno Charneca
Portuguese National Civil Engineering Laboratory (PT)
Knowledge of the sea-wave characteristics is of
paramount importance in the design of port and coastal protection works, in
the evaluation of the navigation conditions at the entrance channels and inside
the harbours, and in the study of the morphodynamics of coastal regions.
For such a characterization it is common practice to define the so-called sea-wave
regime in the study region. This wave regime can be obtained from a reasonable
volume of sea-wave data, collected in the study region by adequate measuring
equipment (for instance directional wave buoys). Since the measuring devices
produce only a localized characterization of the desired variables, one has
to use sea-wave propagation numerical models to get a more comprehensive sea
wave description in the study region from the spatial point of view. In addition,
the measuring devices are seldom deployed near the study region, so one has
to transfer the sea-wave regime from the measuring point to the study region,
Figure 1.
Figure 1: Overview of the useful models
However, the application of numerical models can be very
complex and slow, either in the preparation of data files such as bathymetry
data, wave conditions, domain configurations, or in the visualization of the
models results.
Thus, it is important to organize the basic information for the application
of the models (such as bathymetries, harbour geometries, incident wave conditions,
etc.) and to establish quick and efficient working methodologies to deal with
that information. In the field of coastal engineering, there are systems connecting
numerical models with Geographical Information Systems (GIS). Some successful
examples of these systems for modelling sea wave propagation are the commercial
products of the Danish Hydraulic Institute (MIKE_INFO series, http://www.dhisoftware.com),
or the system presented by Gilman et al. (2001).
It is important to note that coastal engineering studies have a strong geographical
component. So, the use of a GIS tool as a basis for the development of the general
system facilitates the storage, retrieval, query, modification, and manipulation
of data as well as the grid generation that is used for discretization of the
computational domains of each numerical model.
Charneca et al. (2004) and Zózimo et al. (2005) began the development
of SIMAR for the Portuguese coast, by using ArcGIS™. The work consisted
in the development of an interface that permits the communication between the
GIS and the wave propagation numerical models by using the Visual Basic for
ApplicationsTM language. That interface permits: a) the automatic visualization
of the bathymetry data and some of the numerical results, b) to run the REFIDF
and DREAMS models (two common numerical models for wave propagation). The interface
was tested for a classical test of the literature (Vincent and Briggs, 1989)
with success. However, this preliminary work did not take into account some
important actions, such as the:
So, the main objective of the work made during the research-training
period was the development and implementation of procedures, in order to enable
SIMAR to perform the four important actions mentioned above. This will facilitate
the studies of wave propagation along the Portuguese coast.
The numerical models implemented in SIMAR include several wave propagation models
such as the parabolic mild-slope model REFDIF, Dalrymple and Kirby (1991) and
its spectral version REFDIF S, Kirby and Ozkan (1994), the elliptic mild-slope
model DREAMS, Fortes (1993) and the fully nonlinear Boussinesq equation model,
FUNWAVE, Kirby et al., (1998), namely its 1D and 2D versions.
The basic steps of the work presented in this report are: