Technical Field

The present invention relates to a method for the requalification, the construction and the restoration of submerged and/or partially submerged beds of lagoons, shores and the like, in order to provide for the restoration of marine habitats.

Background Art

As is known, one of the main causes of degradation of marine habitats is represented by the phenomena of erosion and silting particularly in shoals (areas made up of beds at a depth of just a few dozen centimeters), but it is also represented by the disappearance of formations known as 'velma' (a Venetian word meaning a portion of lagoon bed free from vegetation, quite shallow and normally submerged, but which however emerges under particular conditions of low tide) and 'barena' (another Venetian term meaning wet lagoon areas that are submerged at high tide), which are host to vegetation that thrives in brackish areas and constitute a primary and irreplaceable habitat for lagoon fauna and bird life.

Another reason for degradation is the intensive and prolonged cultivation of mussels in these regions. The sedimentation of organic waste takes away oxygen which is vital to the survival of the mussels.

In attempts to contain this phenomenon reconstruction works have been carried out, both of lagoon beds that are always submerged, and of silty and sandy stretches emerging at low tide, and also of 'barena' formations.

The reconstruction is generally done by moving huge volumes of sand from silted-up areas to eroded areas.

One of the main difficulties of this technique is that the layer of sand that has to be deposited is usually very small, in the order of 50 to 70 cm. Keeping within this window is essential in order to recreate the natural conditions necessary for triggering the formation, in particular of the velma and barena formations, and thus for recreating the ideal habitat for the establishment of the fauna and bird life typical of these areas.

Disclosure of the Invention

The aim of the present invention is to provide a method for the requalification, the construction and the restoration of submerged and/or partially submerged beds of lagoons, shores, and the like, which executes the depositing operations with high precision.

Within this aim, an object of the present invention is to provide a method for the requalification, the construction and the restoration of submerged and/or partially submerged beds of lagoons, shores, and the like, which has a reduced environmental impact.

Another object of the present invention is to provide a method for the requalification, the construction and the restoration of submerged and/or partially submerged beds of lagoons, shores, and the like, which can also be applied when the bed is uneven and characterized by high instability.

Another object of the present invention is to provide a method for the requalification, the construction and the restoration of submerged and/or partially submerged beds of lagoons, shores, and the like, which is low-cost, relatively easily and practically implemented and safely applied.

This aim and these and other objects which will become more evident hereinafter, are achieved by a method for the requalification, construction and restoration of submerged and/or partially submerged beds of lagoons, shores and the like, which comprises the steps of:

a) collecting a mixture of sea water and sandy sediments;

b) varying the density of said sandy sediments in said mixture until a preset density value is reached;

c) transporting said mixture, once said preset density value has been reached, to a deposit site, preferably located in proximity to a coastal region, of the type of a lagoon, shore, and the like, for the requalification, construction and restoration of the bed of said site;

d) releasing said mixture in a controlled manner in order to form a bed, having a density of sandy sediments equal to said value, at the deposit site.

Brief description of the drawings

Further characteristics and advantages of the invention will become more apparent from the detailed description that follows of a preferred, but not exclusive, embodiment, according to the invention, which is illustrated for the purposes of non-limiting example in the accompanying drawings wherein:

Figure 1 is a functional block diagram of the method according to the invention;

Figure 2 is a functional block diagram of an execution sequence of the block labeled a in Figure 1 ;

Figure 3 is a functional block diagram of a different execution sequence of the block labeled a in Figure 1 ;

Figure 4 is a functional block diagram of an execution sequence of the block labeled c in Figure 1 ;

Figure 5 is a functional block diagram of an execution sequence of the block labeled d in Figure 1.

Ways of carrying out the Invention

With reference to the figures, the reference numeral 1 generally designates a method for the requalification, construction and restoration of beds of lagoons, shores, and the like, in order to provide for the restoration of marine habitats.

In precise terms, a lagoon is a coastal basin separated from the sea (or from the ocean) through inlets, or port entrances, and it is characterized by wide variety and great complexity, both environmental and morphological.

A lagoon is in fact made up of a network of main channels, minor channels, islands, velma formations, barena formations, lakes, marshes and reed beds, a primary and irreplaceable habitat for marine fauna and bird life.

A shore is a boundary line between land and the water of an ocean, gulf, sea or great lake, and it is subject to processes of evolution that change its appearance and physical structure, depending on whether the forces that prevail are destructive (that is to say, erosion phenomena due to the disaggregating action of currents and wave motion) or constructive (bringing new sand).

According to the method 1 , first it is necessary to collect a mixture of sea water and sandy sediments (step a)).

In a subsequent step b), it is necessary to vary the density of the sandy sediments in the mixture, until a preset density value is reached.

This operation is preferably performed with the aid of pressure water jet pumps which promote the mixing and disaggregation of the sandy sediments.

This preset value has been calculated to match the chemical/physical characteristics of the bed that is the focus of the marine habitat restoration project.

Once the mixture has reached the preset density value, in a further step c) it will be transported to a deposit site, by means of floating or ballasted pipes, preferably arranged in proximity to a coastal region, of the type of a lagoon, shore, and the like, for the requalification, construction and restoration of the bed of that site.

At this point, it is then necessary to release the mixture in a controlled manner in order to form a bed, with a density of sandy sediments equal to the preset value, at the deposit site.

According to an embodiment of undoubted practical and applicative interest, as illustrated in Figure 2, the step a) of collecting is constituted by two steps e) and f).

The first step e) consists in taking a preset quantity of sandy sediments from sandy deposits preferably selected from quarries located on land or at sea and the like.

The second step f) consists in supplying a treatment tank containing sea water with a preset quantity of sandy sediments.

This withdrawal, and the subsequent transport to the treatment tank, can be carried out, if the distance between the withdrawal area and the deposit area is more than 6-7 km, by means of a cargo ship, provided with an extendable mechanical arm.

According to another embodiment, which is particularly simple and effective, as illustrated in Figure 3, the step a) of collecting will be executed by means of a specific step g) that consists in taking a preset quantity of sandy sediments from an underwater quarry by using dredging systems that are capable of mixing the sandy sediments with sea water in a controlled manner. These systems will be preferably arranged on floating vessels, pontoons and the like.

Conveniently, the step b) of varying consists in disaggregating and homogenizing the sandy sediments, mixed with sea water, until a mixture with the preset density value is obtained.

Verifying that the preset density value has been reached is done by means of a densimeter.

Conveniently, the step c) of transporting involves three substeps.

A substep cl) consists in taking the mixture by means of an aspiration device.

Then, it is necessary to carry out a step c2) of sending the mixture to a straight- flow pump.

Once the substeps cl) and c2) are completed, the process continues with a substep c3), in which the mixture is conveyed under force, by means of the straight-flow pump, inside discharge pipes which lead into the deposit site.

This discharge piping is generally interposed between two stations, one at the point of departure, arranged in proximity to the treatment tank, and one at the point of arrival, positioned at the deposit site, where the discharge pipes go.

The step d) of releasing is broken down, in turn, into four further substeps.

A step dl) consists in a substep of measuring the starting depth of the bed of the site.

Subsequently the process is continued with a substep dl) of depositing the mixture on the bed by using a diffuser that enables homogeneous distribution over the work face.

This diffuser is contained inside a pool constituted by floating pontoons provided with a flexible band which make it possible to limit and contain the turbidity of the mixture inside the pool that is physiologically created.

It is then necessary to perform a step d3), which consists in stepwise monitoring of the current depth of the bed, obtained by depositing the mixture on the bed itself.

These substeps dl) and d2) are generally executed by an amphibious excavator fitted with adapted devices, which is capable of determining its orientation with respect to the bed on which it is operating.

A substep d4) consists in concluding the step d2) of depositing when the current depth reaches a preset design depth of the bed.

More specifically, the step of depositing d2) consists in pouring the mixture on the sea bed in successive layers of preset thickness.

In particular, the step of verifying d3) is performed by means of a satellite control device.

In fact, the planimetric position of the amphibious excavator and the current depth of the bed are geo-referenced by means of the satellite positioning system.

The method 1 , according to the invention, thus makes it possible to carry out the depositing operations with high precision and when the bed is uneven and characterized by high instability.

This is due to the presence of the satellite system which verifies both the planimetric position of the amphibious excavator and the current depth of the bed, continuously comparing it to the preset design depth of the bed.

In this way it is possible to interrupt the depositing operations upon reaching the preset depth, without the necessity of ancillary operations to remove excess sandy sediments.

Another advantage of the present method is that it causes a reduced environmental impact.

In fact the means used, such as for example the treatment tank, prevent the formation of turbidity in the surrounding environment.

Moreover this method does not involve the installation of fixed structures which would contaminate the marine and land habitat.

In practice it has been found that the method for the requalification, the construction and the restoration of submerged and/or partially submerged beds of lagoons, shores, and the like, fully achieves the set aim.

The invention, thus conceived, is susceptible of numerous modifications and variations, all of which are within the scope of the appended claims. Moreover, all the details may be substituted by other, technically equivalent elements.

In the embodiments illustrated, individual characteristics shown in relation to specific examples may in reality be interchanged with other, different characteristics, existing in other embodiments.

In practice, the materials employed, as well as the dimensions, may be any according to requirements and to the state of the art.

Where the technical features mentioned in any claim are followed by reference numerals and/or signs, those reference numerals and/or signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly, such reference numerals and/or signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference numerals and/or signs.