Page 8 - Pasanisi_alii_2015

variations in median grain diameter d 50 along beach
profile and little difference between the two sites. So,
as an approximation, consistently with the purpose
of the present work, a constant value of d 50 =0.20 mm
was assumed for both Cala Azzurra and Lido Burrone
beaches.

Bathymetry of submerged beaches
Based on survey data, a quite complex morphology of
submerged beach was observed at both sites. Mean
slope of submerged beach can be estimated as 2.5% at
Cala Azzurra and 1.8% at Lido Burrone.
For example purpose, bathymetric contour maps
derived from surveys 1 and 2 are plotted in Figures 7
and 8. Depending on instruments operation and safety
FIGURE 7 Bathymetric maps of Cala Azzurra derived from Survey of navigation, the minimum investigated depth is about
1 and Survey 2 data
1.5-2.0 m.
Examples of bathymetric changes estimated by two Research & development
consecutive surveys are plotted in Figure 9. Positive
bathymetric variations indicate sediment deposition,
being the opposite for bottom erosion. To a large
extent, slight bathymetric variations can be noticed
between the surveys at both sites, whereas only in
a few limited areas bathymetric changes of 1 m in
absolute value can be observed. Overall, Cala Azzurra
showed greater bathymetric variations than Lido
Burrone. Similar results were obtained comparing data
from the other surveys.
However, for a correct interpretation of results,
FIGURE 8 Bathymetric maps of Lido Burrone derived from Survey considering the various sources of uncertainty in data
1 and Survey 2 data
acquisition and processing, bathymetric differences
lower than 0.30 m in absolute value should be
regarded as negligible.
In Figures 10-13, beach profiles extracted from measured
data at selected cross-shore transects are plotted. As
regards Cala Azzurra, profile CA09 is representative of
the western bay, whilst CA21 corresponds to the eastern
bay. As regards Lido Burrone, profile LB10 is taken near
the North-West end of the site, where emerged beach is
absent, whilst LB23 corresponds to the part of the bay
where emerged beach is present.
As already observed from contour maps, submerged
beach has a quite complex geometry and bathymetric
changes among different surveys are relatively small. In
particular, survey data do not seem to indicate a clear
FIGURE 9 Bathymetric variations estimated from Survey 1 to
Survey 2 seasonal regime of submerged beach profiles.

EAI Energia, Ambiente e Innovazione 4/2015
53