Like their colleagues in the "Dredging" section, the agents of the " Hydrography" section are all registered sailors.  A manpower of seven people whose seniority varies from three to thirty years within this cell which, until last 31 December, depended on the DDE before being integrated into the Port Authority of La Rochelle.
 

As emphasized by Jacques Fazilleau, Head of Cell, the tasks concerned with hydrography are vast " They relate to all the measurable physical elements at sea:  study of currents, particle size distribution, side-scan and seismic sonar, study of tides and bathymetry ".  These the last two points represent 95 % of the activity ensured by Jacques Fazilleau, Christian Guichet, Jean-Patrice Guicheteau, Jean-Jacques Besnard and Laurent Chognot, all hydrographers, as well as Jean-Pierre Linkarneau and Alexandre Hautefeuille, the two owners of launches.

« Three times per annum, we use sonar for the whole of the Port »

Bathymetry and the study of the tides, are two of the specialities which the team of Jacques Fazilleau carries out for the Port Authority of La Rochelle. "Three times per annum, we use sonar for the whole of the Port ".   Aboard the catamaran launch Les 2 Mouettes the agents measure the height of water using the ultrasonic depth finder.  "It is a tool of high precision.  The last one cost no less than 50 000 €."   In the phase of acquisition of data, the GPS centi-metric differential gives to the pilot the position of the launch compared to the profile to be followed and makes it possible, at the same time, to locate with precision the site for measurement of depth.  The computer file made up is then worked over again in offices for a data processing run. And that is where the whole skill of the hydrographer lies!  If the sea reports require one working day for three people, the following stage mobilizes an agent for three days.  "It is necessary to carefully check the absence of faulty reproductions in the surveys carried out on site.  The passage of a fish in the area of the probe can for example distort the height of measured water.  All the points raised must be consistent ".   Last phase, after acquisition and treatment:  type-setting, publishing and sending of the documents.  Because these data are invaluable for the other operational services related to the operations of the Port. "The Harbour Office must be informed of the Harbour coastline to know if he can or not accommodate a ship, just as the "Engineering" and "Dredging" services which must be informed of the progress recorded".

Customers of the "Hydrography" service

In addition to the Port Authority of La Rochelle, the "Hydrography" service also intervenes on behalf of customers.   First of all in the number of hours worked:  the County Council of Charente-Maritime.  "An agreement binds us to the departmental institution.  It arranges our assignments in all the departmental ports:  the commercial port of Rochefort/Tonnay-Charente and thirty-eight other ports, for fishing, oysters and   leisure".  Until the end of 2005, the " Hydrography " service also intervened in the natural public domain for the County Council, in order to follow the evolution of the coast line on the whole of the department, in particular on significant points such as La Baie de  Marennes-Oléron (Oyster Bay) or la baie de Bonne Anse.  Because of moving to the status of a Port Authority, modifications in financing took place for the continuation of these interventions.  " These assignments are of primary importance for coastal defences  and they are used in addition to support various studies or documents published by the Hydrographic and Oceanographical Service of the Navy, IFREMER, the University of La Rochelle, or the Centre for Technical Study of Equipment ".  

"The whole panel of nautical means"

The second customer of the service, are the authorities and private companies.  "We are talking about ports such as Sand-d’Olonne, Lorient, Noirmoutier, Brest or Cherbourg ".   As for private companies, these are for example sand-glasses who, for collection areas at sea, are obliged to produce bathymetric reports. "Whatever the location and the nature of our interventions, we have the whole panel of nautical means to operate where one wants to!  ".   In addition to the catamaran launch Les 2 Mouettes, the section under Jacques Fazilleau has two others:  Bathus as well as a smaller one in tow, Babydro.  "To get to the port of Vitrezay on the estuary of the Gironde, by sea, we need a whole day, whereas by road two hours are enough ".