Practical guide


The following paragraphs aim to describe the complementary tasks to numerical modellings :
- the collecte of the data
- the legislation.
They are presented in boards and should permit to future users to know the guide lines and names of persons to contact to further information.

I-Collect of the data

Here are the necessary data to realise a numerical modelling of an artificial reef. You will find a definition of each element, the description of its main use and its origin.
If you still don't understand any technical terms, please consult our glossary.

 I-1 SHOM maps

This maps are published by the Oceanographics and Hydrographics Department of the Navy (SHOM). They presents the parameters :

In France, to know the Zero level in each port in comparison with the general Zero level in Bourdaloue, consult the "Annuaire des marées des côtes de France" published by the Hydrographics department of the Navy.

SHOM MAPS

- details of the bay, information on the nearby seaside

- the SHOM map of the bay is presented in the project (III-2 Cartes ) in 4 différent sizes

Use

- data for numerical modellings

- essential for the network, less details than in the bathymetry

Needed materia

- digitizing table, software (Matisse de TELEMAC...)

Origin

-

Priice

-

Contact

-

 

I-2 Bathymetry

They are level curves. They represent dephts with a scale of 1/1000ème, and sometimes 1/500ème.

Nowadays, the Hydrographics Department of the national Navy tends to develop new ways to acquire data with satellites.

BATHYMETRY

- description of the sea bed

- presents isobars, scale 1/2000e.

Use

- data basis for software

- used for a detailled network

Needed material

- digitizing table, software (Matisse de TELEMAC...)

Origin

- DDE, studies and surveys department

Price

-

Contact

-

 

I-3 Oceanographics and meteorological data

This data are relatives to wind and swell. They generally can be obtained easily at the National Mete Center. They are presented as compass cards or as diagrams representing frequency and amplitude of the swell.

COMPASS CARDS

- represents the average of the winds in accordance withthe direction

- star with proportional branches

- availa: rose des vents mensuelle à Socoa 1993-1997

                    rose des vents mensuelle au Musée de la mer, Biarritz 1993-1997

Use

- to define the main winds

- complememt of the orientation of the swell

Needed material

-

Origin

- Météo France

Price

- about 150F

Contact

- Monsieur DUPONT, aéroport de Biarritz Parme, tél : 05.59.41.55.02, fax : 05.59.41.55.05

 

SWELL DATA

- synthetical card of swell measures

- monthly repartition of the swell

- diagram hight/periods

-number of events each year by hight

-return period

Use

- permet de définir les hauteurs de houle dominantes

- permet d'optimiser le dimensionnement du reef

Needed material

- eventually : statistics tools

- possibility of statistics treatment by subcontracting

Origin

-Technical Department of the Navy

Price

- Observed data : about 150 F (swell + sea due to local wind ) in Socoa

- After a complete study realised by Météo France : environ 30 000 F

Contact

Statistical data processing : M.Ballesta bureau d'étude à Bordeaux 7, avenue Rollan Garos 33700 Mérignac

Meteorological study : P.Dandin Service central de Météo France Prévisions Maritimes 42, av Coriolis 31057 Toulouse Cedex tel : 05.61.07.82.90

Buyos off Biscarosse : Centre d'Essais des Landes ( données de houle brutes : faire attention à prendre en compte les phénomènes locaux ) tel:05.58.82.23.45

Specialised contact : M. Gérard Goasguen tel :02.98.05.67.73 Joël de l'Her tel:02.98.05.67.60 Service des Phares et Balises de Brest

 

I-4 Sedimentology

SEDIMENTOLOGY

The nature, the origin and the movements of sediments are defined by :
- geomorphology
- hydrodynamics (winds, streams )
- sea bed (topography, bathymetry...)

Use

It is necessary to know the nature of the surface of the sea bed and the nature of the ground in depht. The stability of the reef will depend on that.

Needed material

- eventual modelling on TELEMAC

Origin

- DDAS : analysis of the water

Price

-

Contact

Water analysis : DDAS service Qualité des plages tel:05.59.92.51.79

M.Prouzet Ifremer tel:05.59.48.16.81

Notes on the collect of the data  :

It is one of the most important part of the project. 
In fact, it is not the most difficult but it takes a long time and it musn't be under-estimated.
For example, we had benn a bit desapointed when we realised time was going on. We had to think of another solution and when we decided to begin the modellings with imaginary data, we also discovered that using software is not an easy task ...


 II-Legislation


Construction of a reef requires very careful environmental planning and coordination with the community. Modification of the wave field will alter the local current structure and the forces that move beach sand. Safety must be a primary concern; the reef must not present an unusual hazard to surfers and others.

The following paragraphs summarize the laws governing the coastal development and purpose guide lines for a complete project.

    II-1 The "littoral" law
    II-2 Planification and development
    II-3 Impact study
    II-4 Organigram

 

II-1 the"littoral"law

THE "LITTORAL" LAW

The protection and the coatal devolpment are governed by the "littoral" law, complement of the decret of the 25 Août 1979. Its purpose is to promote a specifical politics of development, protection and exploitment. By governing the coastal constructiond, natural and socio-economical patrimony is protected

"La réalisation de cette politique d’intérêt général implique une coordination des actions de l’Etat et des collectivités locales, ou de leurs groupements, ayant pour objet :

 

 II-2 Planification and development

SMVM 

The government set up a new tool : les schemas of exploitment of the sea (SMVM) . They are exposed to the unicipalities, to the départments and are aprouved by a decret in Government Council.

The decret 86-1252 of the 5 Décembre 1986 fixes the objectives.

" - déterminer la vocation générale des différentes zones
- préciser les vocations des différents secteurs de l’espace maritime et les conséquences qui en résultent pour l’utilisation des diverses parties du littoral
- définir les conditions de la compatibilité entre les différents usages de l’espace maritime et littoral."

 

II-3 Impact study

IMPACT STUDY  

It is imposed by the law of the 10 Juillet 1976 relative to the protection of the nature which the total coast  is superior than 6 millions of francs.

L'’étude d'’impact présente une analyse de l’'état initial du site et de son environnement portant notamment sur les richesses naturelles et les espaces naturels, agricoles, forestiers, maritimes ou de loisirs, affectés par les aménagements ou ouvrages.

L'’étude d’impact présente une analyse des effets sur l’environnement, et en particulier sur les sites et paysages, la faune et la flore, les milieux naturels et les équilibres biologiques et, le cas échéant, sur la commodité du voisinage (bruits, vibrations, odeurs, émissions lumineuses) ou sur l’hygiène et la salubrité publique.

 

II-4 Organigram

To realise a good study of the reef, it is necessary to follow a methodology precised by the law to not forget any parameter. The  following organigram  presents the main steps.

 


 

CONCLUSION

We tried to make this guide practical. The glossary and the contacts lists should also help you the futures users.
Cost aspect was delicate to examine because the project is just at its first step. Nevertheless we estimated the reef volume at about 170 000 m3 : quite important to be very careful while choosing the material ...