Liens

Fight against Erosion.

The fight against erosion consists in stabilize the Sea bottoms by the use of the wellknow “Principle of Hedge”.

Crossing lines of hedge structures, the stream is braked and then go back at the bottom’ level, inducing a sedimentation and an rise of the bottom.

Fields of applications :

The use of this process take place everywhere the currents take off sediments :

- Movable bottoms ( sediments of dredging)

Stabilization of - Seashore line .

- Foot of embankment and beach.

- Artificial reefs (Concrete structures)

Equipping - Playful structures to the skin diving.

- Artificial reefs for nutritious and habitat functions.

Reefs ‘ structures against marine erosion :

The standard structure is the « Hedge » structure.

Hedge’ structure on Boat « Scheme of Hedge’ structure »..

It’s constituted with the arrangement of two or several “rake” of sticks stand in crossway or in square way.

Each rake is constituted by a girder in reinforced concrete from 2 to 4 m long with approximately 50 kg / ml, in which ones, 8 to 16 sticks are fixed down.

In function of the quality of the fouling, the stick are separated by a space from 25 cm to 40cm.

With the Bio-construction around the sticks, the muff of life reach 25 to 35 cm.

The girder is made with reinforced concrete with fiber-glass / epoxy resin sticks to avoid the bursting of the concrete, because of the process of rust generated by the traditional iron.

Rings located at the extremities of the girders allow to fix the structures between themselves.

The general effect is the reduction of the currents, the increase of the sedimentation on a length of ten time the high of the sticks.

Other structures are used.

Positionning of the “Current’ brakes”.

The “Current’ Brakes” are constituted by a double range of « Hedge » structures, allowing a better action on the current and the creation of a pad of stabilizing sediment in the middle of the range.

- On the submarine slope:

The lines of “Hedge” structures are positioned perpendicularly to the coastline but can be lightly oblique in order to act as a deflector and turn the sand toward the seashore.

To bring a good stabilization, the spacing between equivalent “current’ brake” is 10 to 15 time the high of the “Hedge” structure.

- On the beach:

The “Hedge” structure brake the current avoiding the problem generated by the “stones breakwaters” (accumulation of sediments upstream and erosion downstream the strongest current).

- References of erosion ' control:

In few years, the seashore of Cap Ferret has been changed from a sweet slope sandy beach into a abrupt stony embankment.

This embankment induce his own erosion and make periodic crumbling.

This zone is forbidden to general public because of insecurity.

We have made a sub-marine yard at the foot of the stony embankment of Cap Ferret in 2001 and since, the sediments and the embankments are stabilized.

This yard is controlled since 5 years and the results have been validated by the planning department “MD Consultants” specialized in marine sedimentation.

The report confirms the stabilization of the bottom, the diminution of the amplitude of the ripple marks from 40 to 5 cm, the interest of the fauna in that process.