Environmental and resource applications
Figure 3
The stages adopted during
the development of the flood
hazard model.
Defence Survey (SDS) held by the UK Environment Agency. The SDS is
based on fieldwork undertaken by Sir William Halcrow and Partners in
1990. It forms part of the Shoreline Management System which is the
Environment Agency coastal GIS database (Leggett & Jones, 1996).
The SDS is constructed using the Intergraph GIS and Oracle database
packages, but was converted into Arc/Info format for this analysis.
Arc/Info was used to query SDS to determine the lowest defence height
in each management unit. Flood hazard was then modelled as a function
of two mechanisms: overtopping and structural defence failure
(Meadowcroft et al., 1996). In order to derive the annual frequency of
an overtopping event under baseline conditions (year 1990), the return
level frequencies for extreme water heights were compared with the corresponding lowest defence heights in each flood unit. It was assumed
that if a given water level exceeded the lowest defence height, the whole
unit would be flooded.
Integration of the model into a coastal management system
To incorporate the output of the hazard analysis into a Prospero Bay
like modelling application, a decision support system has been developed that consists of a simple front-end and a coastal process modelling
appiication, both written in Visual Basic. These are close coupled to a
mapping applet, Microsoft Datamap, produced by the Mapinfo Corporation. The package is structured in such a way so as to provide
coastal managers, the anticipated users, with a link between potentially useful GIS technology and data and understanding of the processes operating within the coastal zone. Significantly, it lias been
designed for users with little or no GIS experience, and it can run on
almost any PC equipped with Microsoft Windows.
205
Figure 3
The stages adopted during
the development of the flood
hazard model.
Defence Survey (SDS) held by the UK Environment Agency. The SDS is
based on fieldwork undertaken by Sir William Halcrow and Partners in
1990. It forms part of the Shoreline Management System which is the
Environment Agency coastal GIS database (Leggett & Jones, 1996).
The SDS is constructed using the Intergraph GIS and Oracle database
packages, but was converted into Arc/Info format for this analysis.
Arc/Info was used to query SDS to determine the lowest defence height
in each management unit. Flood hazard was then modelled as a function
of two mechanisms: overtopping and structural defence failure
(Meadowcroft et al., 1996). In order to derive the annual frequency of
an overtopping event under baseline conditions (year 1990), the return
level frequencies for extreme water heights were compared with the corresponding lowest defence heights in each flood unit. It was assumed
that if a given water level exceeded the lowest defence height, the whole
unit would be flooded.
Integration of the model into a coastal management system
To incorporate the output of the hazard analysis into a Prospero Bay
like modelling application, a decision support system has been developed that consists of a simple front-end and a coastal process modelling
appiication, both written in Visual Basic. These are close coupled to a
mapping applet, Microsoft Datamap, produced by the Mapinfo Corporation. The package is structured in such a way so as to provide
coastal managers, the anticipated users, with a link between potentially useful GIS technology and data and understanding of the processes operating within the coastal zone. Significantly, it lias been
designed for users with little or no GIS experience, and it can run on
almost any PC equipped with Microsoft Windows.
205