150
urbanised society in that the gently sloping land adjacent to estuaries provide ideal
locations for our cities, industry, transport links and water-based recreation facilities.
When expressed as a proportion of the total linear distance of the British coastline the
area that is susceptible to coastal flooding due to sea level rise is very small.
The nature of the problem provides an opportunity for identifying the
potential areas of impact of coastal flooding. The dynamic nature of the spatial
problem combined with the multiplicity of environmental data involved demands a
methodology which can manage the data while at the same time allows modelling of
the problem to take place under a variety of scenarios.
Main Reasons for Attempting to Predict Flood Risk
There are three reasons for predicting the areas most at risk from the possibility of
future flooding:
to allow the identification of the most vulnerable and/or most valuable sections
of the coastline;
to allow for the preparation of a management protection policy which may
involve substantial changes in land use over the next 30 years;
to determine by means of cost-benefit survey the sections of coastline that
would justify the massive cost of strengthening the existing flood protection
mechanisms.
1)
2)
3)
This chapter presents a methodology that can help provide information for the first and
third points shown on the overhead. The methodology involves the compilation of a
spreadsheet comprising minimum elevation values and land use types. Until the
availability of the Ordnance Survey (OS) Digital Terrain Model (DTM) data in March
1997, the compilation of elevation data had taken a considerable of amount of time.
The OS DTM tiles now available at a scale of 1:10,000 provide either contoured
elevations or a 10 metre grid of elevation values. At the time of writing a suitable
translator for the OS DTM tiles was not available and instead the methodology used in
the chapter will be illustrated by means of the earlier manually-derived elevation
values based on a 100 metre grid.
Predictions for Sea Level Change
Sea level has been predicted to rise world wide by about 18 cm by 2030 and, assuming
current trends are maintained, by a further 90 cm by 2100 compared to present datum
level (Wigley et al., 1992b). These figures are less than previously thought likely, but
in combination with a potential increase in storminess (Portney, 1991) will be
sufficient to cause serious periodic flooding in low lying areas (Jones, 1994). Stronger
winds will result in larger waves which will cause greater erosion along estuary banks.
Increased rainfall over the land area will cause a greater run-off of fresh water (Wigley
et al,. 1992a). An increase in the discharge of fresh water into estuaries will result in
G. Jones
urbanised society in that the gently sloping land adjacent to estuaries provide ideal
locations for our cities, industry, transport links and water-based recreation facilities.
When expressed as a proportion of the total linear distance of the British coastline the
area that is susceptible to coastal flooding due to sea level rise is very small.
The nature of the problem provides an opportunity for identifying the
potential areas of impact of coastal flooding. The dynamic nature of the spatial
problem combined with the multiplicity of environmental data involved demands a
methodology which can manage the data while at the same time allows modelling of
the problem to take place under a variety of scenarios.
Main Reasons for Attempting to Predict Flood Risk
There are three reasons for predicting the areas most at risk from the possibility of
future flooding:
to allow the identification of the most vulnerable and/or most valuable sections
of the coastline;
to allow for the preparation of a management protection policy which may
involve substantial changes in land use over the next 30 years;
to determine by means of cost-benefit survey the sections of coastline that
would justify the massive cost of strengthening the existing flood protection
mechanisms.
1)
2)
3)
This chapter presents a methodology that can help provide information for the first and
third points shown on the overhead. The methodology involves the compilation of a
spreadsheet comprising minimum elevation values and land use types. Until the
availability of the Ordnance Survey (OS) Digital Terrain Model (DTM) data in March
1997, the compilation of elevation data had taken a considerable of amount of time.
The OS DTM tiles now available at a scale of 1:10,000 provide either contoured
elevations or a 10 metre grid of elevation values. At the time of writing a suitable
translator for the OS DTM tiles was not available and instead the methodology used in
the chapter will be illustrated by means of the earlier manually-derived elevation
values based on a 100 metre grid.
Predictions for Sea Level Change
Sea level has been predicted to rise world wide by about 18 cm by 2030 and, assuming
current trends are maintained, by a further 90 cm by 2100 compared to present datum
level (Wigley et al., 1992b). These figures are less than previously thought likely, but
in combination with a potential increase in storminess (Portney, 1991) will be
sufficient to cause serious periodic flooding in low lying areas (Jones, 1994). Stronger
winds will result in larger waves which will cause greater erosion along estuary banks.
Increased rainfall over the land area will cause a greater run-off of fresh water (Wigley
et al,. 1992a). An increase in the discharge of fresh water into estuaries will result in
G. Jones