CoastGIS’99: geomatics and coastal environment
Its location and low lying nature means the coast of East Anglia is vulnerable to the effects of global warming. Because of this vulnerability,
the climate change associated aspect of coastal management was chosen
for the initial development of the GIS Management System. Of course,
the use of GIS for the assessment of coastal flooding is not new (Shennan,
1993; Zeidler, 1997) but previous work has often not fully exploited
the technology. The methodology adopted for this application is outlined below.
Modelling flood risk along the east coast
The first stage in the research centred around the construction of a GIS
based risk assessment model. Vulnerability was modelled as being a
function of three main coastal processes; tidal and storm surge activities,
sea-level rise, and isostatic adjustment.
To estimate the impacts of storm surges, information was provided by
the Proudman Oceanographic Laboratory on high water predictions
for a period of up to 10000 years at various locations along the coast
(Dixon & Tawn, 1997). A prediction of high water return periods for
each management unit was then calculated in Arc/Info using interpolation; values for each unit were estimated as a function of the return
periods for the nearest two adjacent data points and the distance from
those points to the mid-point of the unit.
Sea level rise predictions were made using the results of research by the
Climatic Research LJnit of the University of East Anglia. Values for projected sea level rise under different climate change scenarios were
derived from the Model for the Assessment of Greenhouse-gas Induced
Climate Change (MAGICC) (Hulme et al., 1995). Based on the output
of MAGICC, the estimated sea level (relative to the base year 1990) was
derived for all years up to 2100. For each management unit, the sea level
rise estimates associated with three different model scenarios (corresponding to a mean warming of 1.5°C, 2.5°C, and 4.5°C respectively) was
computed.
A final important consideration was the impact of isostatic uplift, i.e. the
movement of the land level since the last glaciation that is causing the
subsidencc of most of southern England. This has obvious implications
for determining vulnerability of the coast to sea level rise. Estimates
of yearly mean isostatic adjustment rates for each management unit were
derived in Arc/Info based on a interpolation of point predictions made
for eastern England by Shennan (1989).
The basic spatial units chosen for analysis were MUs. The steps cleveloped to assess climate-change associated flooding risk for each MU are
outlined in figure 3. Because MUs do not have an official designated
landward extent, the 5 m elevation contour was used. In cases where
the 5 km contour lay more than 5 km from the coast, a 5 km buffer
zone was used to close the MU instead.
A major task involved quantifying the level of flood protection provided
within each management unit. For this purpose, data on sea defence
heights and backshore elevation values was taken from the National Sea
204
Its location and low lying nature means the coast of East Anglia is vulnerable to the effects of global warming. Because of this vulnerability,
the climate change associated aspect of coastal management was chosen
for the initial development of the GIS Management System. Of course,
the use of GIS for the assessment of coastal flooding is not new (Shennan,
1993; Zeidler, 1997) but previous work has often not fully exploited
the technology. The methodology adopted for this application is outlined below.
Modelling flood risk along the east coast
The first stage in the research centred around the construction of a GIS
based risk assessment model. Vulnerability was modelled as being a
function of three main coastal processes; tidal and storm surge activities,
sea-level rise, and isostatic adjustment.
To estimate the impacts of storm surges, information was provided by
the Proudman Oceanographic Laboratory on high water predictions
for a period of up to 10000 years at various locations along the coast
(Dixon & Tawn, 1997). A prediction of high water return periods for
each management unit was then calculated in Arc/Info using interpolation; values for each unit were estimated as a function of the return
periods for the nearest two adjacent data points and the distance from
those points to the mid-point of the unit.
Sea level rise predictions were made using the results of research by the
Climatic Research LJnit of the University of East Anglia. Values for projected sea level rise under different climate change scenarios were
derived from the Model for the Assessment of Greenhouse-gas Induced
Climate Change (MAGICC) (Hulme et al., 1995). Based on the output
of MAGICC, the estimated sea level (relative to the base year 1990) was
derived for all years up to 2100. For each management unit, the sea level
rise estimates associated with three different model scenarios (corresponding to a mean warming of 1.5°C, 2.5°C, and 4.5°C respectively) was
computed.
A final important consideration was the impact of isostatic uplift, i.e. the
movement of the land level since the last glaciation that is causing the
subsidencc of most of southern England. This has obvious implications
for determining vulnerability of the coast to sea level rise. Estimates
of yearly mean isostatic adjustment rates for each management unit were
derived in Arc/Info based on a interpolation of point predictions made
for eastern England by Shennan (1989).
The basic spatial units chosen for analysis were MUs. The steps cleveloped to assess climate-change associated flooding risk for each MU are
outlined in figure 3. Because MUs do not have an official designated
landward extent, the 5 m elevation contour was used. In cases where
the 5 km contour lay more than 5 km from the coast, a 5 km buffer
zone was used to close the MU instead.
A major task involved quantifying the level of flood protection provided
within each management unit. For this purpose, data on sea defence
heights and backshore elevation values was taken from the National Sea
204