Shoreline dynamics and risk analysis associated with the coastal
low-lying areas
which are likely to be flooded in the next 100 years
are investigated at the macro scale with a 200 m space resolution grid.
The coastline regression and the areas which are expected to be
flooded should be considered as
`potentially' regressed and `potentially' flooded because all the
natural (dunes) and man-made (coastal structures, embankments) obstacles
to water ingression can hardly be taken into account at this resolution.
DIGITAL ELEVATION MODEL (DEM) AT SELECTED TIMES
DEM in 2050 and 2100 are constructed by decreasing the present
ground elevation by the amount of natural and anthropic subsidence
predicted by the corresponding models.
Storm surges simulated by the hydrodynamic model are landward
extended. 9 scenarios are taking into account: 1, 10 and 100
year return period events are simulated at present, in 2050
and 2100.
Expected coastline profile at a given time is computed
as the intersection between the ground level at that time
and the mean sea level at the same time. Only land subsidence
and sea level rise caused by global climate change are considered.
Low-lying areas which may be episodically flooded owing to
eustatism, land subsidence, and intense meteo-marine events are
detected. 15 scenarios are analyzed considering 3 selected times
(at present, in 2050 and 2100), 3 storm return periods (1, 10 and
100 years), and 2 anthropic settlement scenarios (optimistic and
pessimistic).
A risk factor R is associated to each flooded area.
R is computed
as the product between the meteo-marine event probability, the
area vulnerability (assumes equal to the water elevation over the
area), and the economic value of the area itself (based on the land
use). The risk factor is normalized to 100.
The episodically flooded low-lands and the associated risk are evaluated at
the Ravenna, Cesenatico, and Rimini local sites. Due to the limited
extent of these study areas (whose characteristic length is of the order of
10 km) a detailed analysis based on DEMs with a 10 cm vertical
resolution on a regular square grid of 10x10 m is performed.
Major natural and man-made obstacles to water ingression are also taken
into account.
POSITION/SHAPE INDEX
A position/shape index I is introduced to compute
the risk factor at the local scale. I weights the inundation
risk associated with a flooded area on the basis of the area
position and shape.
A risk factor R is associated to each flooded area.
R is computed as the product between the position/shape index,
the meteo-marine event probability, the
area vulnerability (assumes equal to the water elevation over the
area), and the economic value of the area itself (based on the land
use). The risk factor is normalized to 100.