Chapter 7
The Implications of Oceanographic Chaos
for Coastal Management
E. Wolanski . B. King . S. Spagnol
Graphics. The graphics on the CD can be accessed using a web browser such as Netscape Navigator or Microsoft's Internet Explorer. To start open the file 'index.htm' on
the CUI-ROM. All animations on the CD are stored in AVI format using Cinepak compression. If your browser has trouble viewing these animations visit the homepage
(http://home.netscape.com or http://www.microsoft.com) to download the appropriate plugin. Also read the help.htm file on the CD.
7.1
Introduction
Water currents are usually the first thing measured in environmental impact assessment studies in the ocean. To predict the impact of a pollutant discharge the speed and
direction of the currents are used in a model to calculate the trajectory of contaminants. To characterize a non-conservative material carried by the water currents, the
usual practice is to incorporate in the model sink and source terms. In the model turbulence is usually parameterized, often using an eddy diffusion approach, or explicitly calculated using a turbulence closure assumption. This modelling technique is
successful in reproducing simple ecological and biogeochemical processes in the open
ocean (e.g. Nihoul1993 and references therein).
This technique is also routinely applied in the coastal engineering community to
determine environmental impacts from human activities such as structures, dredging
and dumping of contaminants (e.g. oil, sewage and dredge spoil). Usually the predicted
contaminant plumes are smooth. These plumes are then superimposed on an atlas of
marine resources to determine likely environmental impacts.
In practice, post-construction verification of models is the exception rather than
the rule. Thus, if the structure works within expectations in an engineering way, i.e. the
wave field is within predicted range, then the environmental impact from engineering
structures is also assumed to have been predicted correctly.
Wave models, the principal tool of coastal engineers, have nothing to do with models related to environmental issues. Ecosystem or pollution models are seldom verified. Sewage plumes are an example. Discharges from sewage outfalls are predicted to
be continuous, smoothly varying pollutant plumes. In practice however, these plumes
are extremely patchy (Wu et al. 1994; Pritchard et al. 1996). This patchiness applies to
other contaminants also. For instance, oil slicks commonly break up into patches that
the models do not reproduce (Dean et al. 1990). This patchiness has important implications for a coastal manager because an oil spill at sea along a rugged coast can oil
one beach while the adjoining one remains untouched (Hayes et al. 1990).
The Implications of Oceanographic Chaos
for Coastal Management
E. Wolanski . B. King . S. Spagnol
Graphics. The graphics on the CD can be accessed using a web browser such as Netscape Navigator or Microsoft's Internet Explorer. To start open the file 'index.htm' on
the CUI-ROM. All animations on the CD are stored in AVI format using Cinepak compression. If your browser has trouble viewing these animations visit the homepage
(http://home.netscape.com or http://www.microsoft.com) to download the appropriate plugin. Also read the help.htm file on the CD.
7.1
Introduction
Water currents are usually the first thing measured in environmental impact assessment studies in the ocean. To predict the impact of a pollutant discharge the speed and
direction of the currents are used in a model to calculate the trajectory of contaminants. To characterize a non-conservative material carried by the water currents, the
usual practice is to incorporate in the model sink and source terms. In the model turbulence is usually parameterized, often using an eddy diffusion approach, or explicitly calculated using a turbulence closure assumption. This modelling technique is
successful in reproducing simple ecological and biogeochemical processes in the open
ocean (e.g. Nihoul1993 and references therein).
This technique is also routinely applied in the coastal engineering community to
determine environmental impacts from human activities such as structures, dredging
and dumping of contaminants (e.g. oil, sewage and dredge spoil). Usually the predicted
contaminant plumes are smooth. These plumes are then superimposed on an atlas of
marine resources to determine likely environmental impacts.
In practice, post-construction verification of models is the exception rather than
the rule. Thus, if the structure works within expectations in an engineering way, i.e. the
wave field is within predicted range, then the environmental impact from engineering
structures is also assumed to have been predicted correctly.
Wave models, the principal tool of coastal engineers, have nothing to do with models related to environmental issues. Ecosystem or pollution models are seldom verified. Sewage plumes are an example. Discharges from sewage outfalls are predicted to
be continuous, smoothly varying pollutant plumes. In practice however, these plumes
are extremely patchy (Wu et al. 1994; Pritchard et al. 1996). This patchiness applies to
other contaminants also. For instance, oil slicks commonly break up into patches that
the models do not reproduce (Dean et al. 1990). This patchiness has important implications for a coastal manager because an oil spill at sea along a rugged coast can oil
one beach while the adjoining one remains untouched (Hayes et al. 1990).