The Management of Oyster Culture Leases and Production
271
over 30 cm on the banc de Bourgeois, whereas deposition is more variable across banc
de Ronce with values between zero and 30 cm.
THE DREDGING OPERATION OF PERQUIS/RONCE
In this area prone to siltation, the idea is to improve the flush effect of the ebb tide
through channels surrounding some of the banks. The Conseil Général of Charente
Maritime is currently funding dredging operations carried out by contractors under
supervision of the local Harbour Maritime Service. Two operations are programmed
for impending execution in several phases, the Etier de Perquis in the East (2 phases)
and the Coursière des Lèzards around the Ronce bank (Fig. 6).
The site width is 50 metres, which means all parcels intersecting this corridor
have to be expropriated and their owners granted equivalent leases in the vicinity. The
dredging corridor width itself is only 20 metres. The objective is to compute the
sediment volume between the present elevation and the projected one
The volume computation makes use of the depth grid file. The elevation to be
reached is 1.0 metre above chart datum. After keeping only the pixels above 1 metre in
the grid file (by a thresholding query on the grid table). An averaging of all pixels
values contained in the polygon is then performed (using the above-mentioned
tool) which yields its average depth
The volume is computed
as:
In Etier de Perquis, the first phase concerns a surface to be dredged of
on an average sediment height of 0.7 metres, that is a volume of
In
Coursière de Ronce,
are concerned on a height of 1.6 metres, i.e. a volume of
Future Prospects
A number of further uses of the cadastre data base are foreseen.
- In biology, stock assessment is a major issue in this basin. In order to assess the
global biomass, the delineation of homogeneous zones of culture type is needed. As
regulations may not be respected, the only way to approach reality is to interpret
airphotos previously registered to the cadastre file. Every couple of years, B&W
airphoto campaigns are undertaken with simultaneous oyster biomass sampling
- Productivity, mortality, epizooties are also of highest concern. Ways are sought to
couple results of trophic and sedimentological models with field observations in test
parcels, together with the incidence of rainfall sewage outfall
- In socio-economy, there are prospects of a better understanding of the lease exchange
system by computing a
lease value based on major bio-
271
over 30 cm on the banc de Bourgeois, whereas deposition is more variable across banc
de Ronce with values between zero and 30 cm.
THE DREDGING OPERATION OF PERQUIS/RONCE
In this area prone to siltation, the idea is to improve the flush effect of the ebb tide
through channels surrounding some of the banks. The Conseil Général of Charente
Maritime is currently funding dredging operations carried out by contractors under
supervision of the local Harbour Maritime Service. Two operations are programmed
for impending execution in several phases, the Etier de Perquis in the East (2 phases)
and the Coursière des Lèzards around the Ronce bank (Fig. 6).
The site width is 50 metres, which means all parcels intersecting this corridor
have to be expropriated and their owners granted equivalent leases in the vicinity. The
dredging corridor width itself is only 20 metres. The objective is to compute the
sediment volume between the present elevation and the projected one
The volume computation makes use of the depth grid file. The elevation to be
reached is 1.0 metre above chart datum. After keeping only the pixels above 1 metre in
the grid file (by a thresholding query on the grid table). An averaging of all pixels
values contained in the polygon is then performed (using the above-mentioned
tool) which yields its average depth
The volume is computed
as:
In Etier de Perquis, the first phase concerns a surface to be dredged of
on an average sediment height of 0.7 metres, that is a volume of
In
Coursière de Ronce,
are concerned on a height of 1.6 metres, i.e. a volume of
Future Prospects
A number of further uses of the cadastre data base are foreseen.
- In biology, stock assessment is a major issue in this basin. In order to assess the
global biomass, the delineation of homogeneous zones of culture type is needed. As
regulations may not be respected, the only way to approach reality is to interpret
airphotos previously registered to the cadastre file. Every couple of years, B&W
airphoto campaigns are undertaken with simultaneous oyster biomass sampling
- Productivity, mortality, epizooties are also of highest concern. Ways are sought to
couple results of trophic and sedimentological models with field observations in test
parcels, together with the incidence of rainfall sewage outfall
- In socio-economy, there are prospects of a better understanding of the lease exchange
system by computing a
lease value based on major bio-