The present invention relates to a device for an operating barrier for a channel or a waterway to make an operating dam. The invention also relates to the pertinent installation made up of the device and the infrastructures or works to be built in order to make the device operative.

Devices for holding back a waterway or a channel in order to protect an environment, an ecosystem, a territory, a harbour or a city from floods, high tides or phenomena of high water are known.

For example, it is possible to construct two gates: one gate hinged to a side bank of a channel and the other gate hinged to the other side bank of the channel. In the inoperative position the gates are along the side banks of the channel and only, if necessary, are they moved in a substantially perpendicular direction with respect to the channel with the free ends joined so as to completely close off the passage of water, as for example occurs in a sluicegate.

Another very interesting solution is to have several operating gates placed side by side, each of which has an end hinged to the bottom of the channel and arranged so that they extend substantially in a perpendicular direction to the channel. The gates are hollow in order to form caissons which can be filled or emptied with water from the channel.

In the rest or inoperative position, the gates are filled with water, and due to their total weight, they are positioned on the bottom of the channel and, therefore, they are horizontal, thus allowing for the flowing of water and for ships to pass. If necessary, the gates are emptied of the water contained therein by introducing compressed air so that, for the Archimede's Principle, that is the floating thrust, they begin to lift up into a vertical or almost vertical position, thus creating a barrier for the passage of water.

This solution was proposed in order to solve the problem of high water in Venice, and it is known as the"Mose Project". This project is composed of a barrier made up of operating gates for each of the three mouths of the lagoon: Lido, Malamocco and Chioggia.

This solution has some drawbacks among which are the fact that, during the operative position, all the gates are raised up and, therefore, it is not possible for any

vessels to pass. This is a great limitation since it may cause enormous economical losses and inconveniences due to the blockage of leisure navigation (for example, leisure boats and cruise ships), merchant/industrial shipping (for example, oil-tankers and cargo-boats) and fishing navigation (for example fishing-boats).

Another problem caused by the complete closure of the channel, or in the case of Venice of all three lagoon or port mouths, is the fact that the usual water ebb and flow is blocked, thus preventing the normal exchange of water in the lagoon and causing damage to both hydrogeologic and ecologic-environmental aspects.

It must to be considered that due to the waves and the wind, above all during bad weather conditions, the gates are subjected to considerable stresses and wear which during time may damage the structures. In such conditions, the effectiveness of the system can not be assured.

Furthermore, the"Mose operating gates"system is rather complicated, since it is necessary to build complex infrastructures in order to install the gates, and all of these infrastructures have to be constructed and/or installed"in loco", the majority of them underwater on the bottom of the channels. It is easy to understand that putting such a plan into execution is a long, difficult and very expensive operation.

Moreover, maintenance is very difficult, since it is necessary to operate in an marine environment, not suitable for men.

In addition to the complexity and the high cost, this operating gate system also has other problems due to its operating limitation, namely that it is only able to hold back high water up to 194 cm. (which was the highest level of high water that ever occured in November, 1996). In case of higher high water, the protection system does not work.

Furthermore, the Mose project requires a long operating time: in fact, the blowing of compressed air in order to empty the gates is a long and slow process thus limiting very much its flexibility and reactiveness.

There exists other solutions, as that which is described in the German Patent DE 3714248 filed on 29 April 1987 in the name of Paraskevopoulus, wherein it is described a hull which can be filled with water in order to be sunk, thus representing a barrier for a channel. In order to remove the hull, it is sufficient to empty it of water and move the hull in a position where it does not hinder the navigation of ships.

Although this solution is valid, it has however some limitations since, if we consider

the usual dimension of the channels or port mouths (for example in the case of the lagoon of Venice) and, then, the dimension required for the hull, there are difficulties in manoeuvring and operating it, as well as arranging it in the desidered position.

Moreover, due to the remarkable dimension of the hull, the time necessary to fill it and, therefore the operating time, could be too long.

In addition, the force of the water current, added to that of the wind or sea-storms, may make it difficult or impossible to manoeuvre the hull in order to postion it in the correct place; in addition, the forces of nature could dislodge the hull or, even, damage it.

It is important to consider also the fact that the above-described hull completely closes the channel, thus blocking the navigation of any kind of ship.

Furthermore, if the channel is very large, it is impossible to close it.

Therefore, the first aim of the present invention, is a device for the operating barrier for a channel or waterway which eliminates the drawbacks cited with reference to the prior art, that is a device which is simple to build and to install, reliable and safe, with reduced construction costs, easy and rapid to be maintained.

It is very important that the intervention time of the device is short, so that the device is efficient also in case of sudden or unforeseeable events.

Another aim of the invention is that of constructing an installation for a barrier for a channel wherin it is possible to make, not only a total closure, but also a partial and adjustable closure.

Another aim is that of constructing an installation for the protection and safeguarding of lagoons or ports in which the accesses to the sea are two or more, for example, for the saveguarding of the lagoon of Venice.

In the latter, besides the above mentioned, it is very important that in the case of high water, the installation enables the navigation also of large ships (oil-tankers, liners, etc. ) and the natural exchange of water, even when the device is in the operative position wherein it forms a barrier against the passage of water. Therefore, the device has to be adjustable so that, on one hand, it holds back the high water, and on the other hand, it allows the ebb of water, thus controlling the final sea level.

Moreover, the device must be able to block a high water phenomenon, even of an exceptional amount, which may occur from a rise in the medium sea level, in case of

a melting of the glaciers due to the overheating of the earthly atmosphere due to carbon dioxide emissions.

These installations have to be of a minimal enviromental impact.

These aims are reached by a device of the initially described type, that is a device for an operating barrier of a channel or waterway comprising at least one mobile element operating between an operative position where it is sunk wherein it represents a barrier against the passage of water and an inoperative position where the mobile element floats, thus allowing for the passage of water, said at least one mobile element being able to contain the water of said channel and the movement of said mobile element between said inoperative position to said operative position occurs by introducing the water of said channel in said at least one mobile element and the movement between said operative position to said inoperative position occurs by expelling the water contained inside the mobile element, characterized in that said at least one mobile element is a floating mobile element and is provided with at least two rooms or compartments able to contain the water of said channel, so that by entering water inside said at least two compartments said mobile element partially or totally sinks so as to lay down or approach the bottom of said channel, thus reaching said operative position and, from said operative position, by expelling the water from said at least two compartments, said at least one mobile element comes to float again so reaching said inoperative position.

Such a device is easy to construct and to operate since it may be easily built in a dockyard whereas, to make it operative it is sufficient to enter water inside. Also its maintenance is easy, since it occurs on board or in a shipyard.

The time of intervention is quick: in fact, in order to reach the operative position it is sufficient to fill with water the compartments in which the mobile element has been divided so causing the"sinking"operation, which occurs spontaneously and rapidly.

In particular each compartment is provided with at least one hydraulic circuit for introducing and expelling water so as to further reduce the intervention time.

Moreover each hydraulic circuit comprises at least one fill pump designed to introduce water of said channel in said compartment when the mobile element is completely sunk, and then laid down on the bottom, in order to overweight it, so that said mobile element is able, thanks to its own total weight, to maintain said operative position, also in case of strong currents or sea-storms.

Preferably the mobile element comprises breakwaters or breakwaves able to absorb or dissipate the energy of the waves which strike it, safeguarding the integrity of the mobile element.

The mobile elements may be also two or more in number and in such a number that their total length is equal or greater than the width of the channel, so as to be able to even completely close a wide channel.

Preferably, at the lower part of said mobile element there are operating barrier elements which operate between a raised position wherein they substantially do not project outside and then do not form a barrier for the passage of water and a lowered position wherein they project outside thus forming a barrier against the passage of water.

In this case, in said operative position, it is not necessary to completely sink the mobile element in order to made a barrier for the passage of water or, in case of irregular bottoms, the difference in the depth of the channel may be compensated for by differentely operating these operating barrier elements.

This invention also relates to an installation for the barrier of a channel or waterway, characterized in that it comprises at least one mobile element of the above-described type and infrastructures for the manoeuvring and/or positioning and/or standing of said mobile element in said operative position.

It can be noted that these infrastructures require a limited amount of work.

Preferably, said infrastructures comprise reference elements for the manoeuvring and/or positioning and/or standing of said at least one mobile element between said inoperative position and said operative position, thus facilitating the manoeuvring of the mobile elements, even of remarkable dimensions, and further reducing the intervention time.

Such infrastructures for the manoeuvring and/or positioning and/or standing of the mobile element allow for the positioning of the mobile element in said operative position in different manners, so as to form a total barrier of the channel, or a partial barrier with a variable closing rate.

The invention relates also to an installation for the barrier of two or more channels or port mouths which flow into a closed basin or a lagoon, characterized in that each channel comprises a barrier installation as described above As already stated, this rapidness allows for the partial closing of the channel, thus

eliminating the high water phenomenon and, at the same time, assuring the free navigation of any kind of vessel and also the usual exchange of water.

This solution respects the environment since the mobile element in the inoperative position may be easily moved so as not to hinder maritime navigation, and also prevents damage to the environment.

The operating capability is remarkable, since this solution is effective even during exceptionally high water, caused, for example, by a rising of the medium sea level.

Even the cost is reduced if compared to a Mose solution.

These and other advantages of the present invention will be more evident from the following detailed description, given for an exemplifying and not limiting purpose, with reference to the enclosed drawings wherein: - figure 1 is a schematic vertical and longitudinal cross-section of the mobile element of the present invention; - figure 2 is a schematic transverse cross-section of the mobile element of figure 1; - figure 3 is a schematic longitudinal view from the top of the mobile element of figure 1; - figures 4,5, 6,7, 8 and 9 are schematic transverse cross-sections of the mobile element taken along the section line IV-IV of figure 3 wherein the element is represented in different positions; - figures 10 and 11 are respectively a longitudinal and a transverse cross-section of a mobile element provided with operating barrier elements; - figure 12 is a top view of an installation using the mobile element of figures 10 and 11; - figure 13 is a schematic transverse cross-section of a mobile element which shows a variant of the operating barrier elements; - figures 14 and 15 are top views of an installation according to the present invention wherein two mobile elements are depicted in different operative positions; - figure 16 is a top view of a first variant of the installation of the present invention comprising three mobile elements; - figures 17 and 18 are top views of other variants of the installation of the present invention; - figures 19 and 20 are respectively a top view and a transverse view of a variant

relating to the means for keeping in place the mobile elements; - figure 21 is a schematic top view of the Venice lagoon wherein an installation according to the present invention has been represented.

In figures 1, 2 and 3, there is represented a mobile element 20 which comprises a hull 22 provided with a flat bottom 22a, a bow 22b, a stern 22c, a left broadside 22d, a right broadside 22e and a main deck 22f. The inner of the hull 22 is divided into rooms or compartments 24 by walls or bulkheads 26. In particular, there is a longitudinal bulkhead 26a and three transverse bulkheads 26b, c, d, thus forming 8 compartments 24a, 24b, 24c, 24d, 24e, 24f, 24g, 24h.

In figures 4 to 9, there is represented a channel or a waterway 30 wherein a mobile element 20 is depicted in different positions, beginning from the position in which it floats, to the position in which it is sunk and, hence, laid down on the bottom 32 of the channel 30.

The water channel 30 has a bottom 32 and a waterline surface 34 and the distance between the free surface 34 and the bottom 32 is the depth H of the channel 30. The area of the bottom 32 of the channel 30, where the mobile element 20 has to be laid down, is levelled so as to have a flat and horizontal surface so that the flat bottom 22a of the hull 20 may lay down perfectly on it. In particular, it is necessary to compact and remove material from the bottom 32. Furthermore, support blocks 36 are inserted at the levelled area in order to sustain the total weight of the mobile element 20.

The mobile element 20 is provided, for each compartment 24, with a hydraulic installation 40 contained in an independent area for the filling and the emptying of the compartment 24 with the water of the channel 30, so that by entering the water in the compartments 24 the mobile element 20 sinks forming a barrier, whereas draining the water from the compartments 24 the mobile element 20 floats again and, therefore, it may be easily moved in order to allow the passage of water and vessels.

In the following it is described the procedure to follow in order to make operative the mobile element 20, with reference to figures 4 to 9. Such a procedure is divided into the subsequent phases.

In phase 1, called"navigation phase", the mobile element 20, with the compartment 24 completely emptied, is brought at the place where it will be"sunk", in order to lay it down on the bottom 32 of the channel 30, as illustrated in figure 4. In this situation,

the mobile element 20 is at its maximum buoyancy and, therefore, suitable for navigation, whereby it may be easily moved to the desired position. The draught of the mobile element 20, that is the difference of the height between the waterline surface 34 of the channel 30 and the bottom 22a of the hull 22, is indicated with H I.

In phase 2, called"immersion phase", water enters into the hull 22. At a certain moment, the mobile element 20 begins to sink until it touches the bottom 32 of the channel 30 and the water continues to enter into the compartments 24 until it reaches the height H equal to the depth of the channel 30, for the"communicating vases" principle, with the mobile element 20 laid down on the bottom 32, as represented in figure 5.

In figure 3, called"overweighting/standing phase", water is forced to come inside the compartments 24, in order to overweight the mobile element 20. The water contained in the compartments 24 reaches height H2 which is greater than the depth H of the channel 30, as illustrated in figure 6. The overweighting permits the mobile element 20 to withstand high winds and strong currents, and the mobile element 20 is overweighted more and more as weather conditions worsen.

In phase 4, called"lightening phase", the emptying process naturally begins (the pressure of the water, which is contained inside the mobile element 20, is greater than that of the water outside) whereby, first of all, the water surplus introduced in the previous phase is eliminated, thus restoring the water level inside the compartments 24 to the H level, equal to the depth of the channel, as represented in figure 7.

In figure 5, called"emersion phase", water is continuously forced out of the compartments 24 until the mobile element 20 comes to float again and the inside water level reaches height H3 which is less than level H (see figure 8). This is essentially an equilibrium situation wherein the total weight of the mobile element is slightly less than the weight of the water displaced.

From this position, the mobile element 20 may be: - quickly sunk again, by introducing water inside the compartments 24 again ; - manoeuvred, namely it may be slightly moved and sunk again by introducing water inside the compartments 24; - returned to the initial situation by completely emptying the compartments 24.

The last operation represents the phase 6, called"draining phase", which consists of

expelling the water contained inside the compartments 24 until completely emptying them, therefore the mobile element 20 reaches the position indicated in figure 9 (corresponding to the position indicated in figure 4).

At this point, the mobile element 20 may be moved away from its position by repeating phase 1 of navigation in the opposite direction.

In the figures and in particular in figure 4, there is represented a hydraulic circuit 40, in order to introduce or expel water from each of the compartments 24, which comprises a first water intake 42 connected to a first shutoff valve 44 which puts into direct communication the outside of the hull 22 to the compartment 24. The first water intake 42 is positioned at a vertical distance from the bottom 22a of the hull 22 less than the height H1, so that in the navigation phase (figure 4) it is positioned below the waterline surface 34 and, by opening the first shutoff valve 44, the water of the channel 30 comes inside the compartment 24.

The hydraulic circuit 40 comprises a main pipe 50 which vertically extends and has, at the lower end, a second shutoff valve 52 and a drain pump 54 able to take away the water contained in the compartment 24, even water at a low level in the bottom of the hull 22. The main pipe 50, at a height slightly greater than the height H1 from the bottom 22a of the hull 22, is connected by means of a third shutoff valve 56 to a second water intake 58, and the pipe is also connected to a fourth shutoff valve 60 which connects the pipe 50 to the inside of the compartment 24.

At a height slightly less than H, the main pipe 50 is connected to a first water outlet 62 by means of a fifth shutoff valve 64 (see figure 7). In the part of the main pipe 50, located between its connection with the third and the fifth shutoff valves 56,64, there is a fill/drain pump 66 and a sixth shutoff valve 68.

At a height approximately equal to the height H2, the main pipe 50 is connected with the seventh shutoff valve 70 which connects the pipe to the compartment 24 (see figure 6).

At last, for safety reasons, there is an overflow or relief valve 72 connected to a second water outlet 74.

In the following the functioning of the hydraulic circuit 40 is described with reference to the six phases already illustrated. For clarity of explanation, in the figures the direction of the water which flows into the pipes of the hydraulic circuit 40 is represented by arrows, the shutoff valves are shown filled in black if they are in

the closed position and the pumps are shown filled in black if they are not operating.

In the phase 1 of navigation (figure 4), the compartments 24 are completely emptied and the mobile element 20 is moved to the position where it has be"sunk".

When the desidered position is reached, the phase 2 of sinking begins. The first shutoff valve 44 is opened and the water of the channel 30 comes inside the compartments 24 by means of the first water intake 42. The third and fourth shutoff valves 56,60 are also opened, connecting the second water intake 58 to the inside of the compartments 24, but since the latter is positioned above the waterline surface, the water does not enter.

When the mobile element 20 reaches a total weight greater than the floating thrust, it begins to sink until it lays on the bottom 32 of the channel 30. The water of the channel 30 continues to enter into the compartments 24, not only through the first water intake 42, but also through the second water intake 58 until it reaches the height H (for the"communicating vases"principle), measured from the bottom 22b of the hull 22, equal to the depth of the channel 30 (see figure 5).

Now, the phase 3 of overweighting begins. The first and the fourth shutoff valves 44,60 are closed, the sixth and the seventh shutoff valves 68,70 are opened and the fill/drain pump 66 begins to operate. The water enters by means of the second water intake 58, passes through the third shutoff valve 56, the sixth shutoff valve 68, the fill/drain pump 66, the seventh shutoff valve 70 and, at last, comes into the compartments 24. When the height H2 is reached (figure 6), the fill/drain pump 66 is stopped and all the valves, namely the third, the sixth and the seventh shutoff valves 56,68, 70 are closed, so as to prevent water contained inside the compartments 24 from going outside.

The mobile element 20 remains in this position for the necessary time in order to hold back a rising of the water in the channel 30 on one side of the element, for example due to a high tide.

The phase 4 of lightening begins by opening the third and fourth shutoff valves 56,60 so that the water comtained in the compartments 24 comes out spontaneously from the second water intake valve 58. The first shutoff valve 44 is also opened so that the water may spontaneously exit also from the first water intake 42. The water spontaneously exits until the water level inside reaches the height H which is equal to the depth of the channel 30 (figure 7).

For the phase 5 of emersion the first and third shutoff valves 44,56 are closed, the fifth and sixth shutoff valves 64,68 are opened and the fill/drain pump 66 is activated. The water contained in the compartments 24 passes through the fourth shutoff valve 60, the sixth shutoff valve 68, the fill/drain pump 66, the fifth shutoff valve 64 and comes out from the first water outlet 62. At a certain point, the mobile element 20 comes to float again and the water level reaches the height H3 (figure 8).

All the valves are closed, that is the fourth, fifth, and sixth shutoff valves 60,64, 68 and the fill/drain pump 66 is stopped.

In this situation the mobile element 20 may be easily manoeuvred, for example to clear the channel 30 or to vary the amount of the closure of the channel if the element is sunk again.

In the phase 6 of draining, the second and the third shutoff valves 52,56 are opened and the drain pump 54 is turned on. The water contained in the compartments 24 passes through the drain pump 54, the second and the third shutoff valves 52,56 and, at last, it comes out from the second water intake 58 until the compartments 24 are emptied (see figure 9).

In order to completely empty the compartments 24, there is a bilge pump 80 connected to a closing valve 82.

Once the mobile element 20 rests on the bottom 32 of the channel 30, it represents a barrier against the passage of water whereby, obviously, in order to protect a channel or a port mouth opened to the sea, against the high tides and/or sea-storms, its height has to be greater than the sum of the depth of the channel, measured with reference to the medium sea level, and the maximum height of the high tide and/or sea-storm which has to be held back.

In this situation and in case the channel is completely closed, if the water level on one side of the element rises, on the other side the level remains approximately the same and equal to the initial and previous level.

If the channel connects the sea to a basin or a lagoon and it is only partially closed, the water level on both sides of the mobile element is about the same but, as the distance from the element, measured towards the basin, increases, the water level decreases more and more until it assumes approximately the same value which existed at the time the channel was closed.

In figures 10 and 11 there is represented a mobile element 220 similar to the above-

described mobile element 20, except that it is provided with several vertically slidable barriers or barricades 202 mounted on its bottom 222a near its longitudinal middle axis and which extend for all the length of the bottom 222a.

In the rest position, that is when the mobile element 220 is in the inoperative position, the slidable barriers 202 are housed inside convenient recesses 204 made inside the mobile element 220. When it is necessary to make a barrier in the channel, the mobile element 220 is positioned in the area where it has to operate and the barriers 202 are lowered until, if necessary, they touch the bottom 32 of the channel 30 (see fig. l0). Therefore, in the operative position the mobile element 220 is only partially sunk and the closure of the channel is completed by lowering the slidable barriers 202. Therefore, the phase 2 of immersion occurs only partially, whereas the phase 3 of overweighting and the phase 4 of lightening are avoided, thus reducing the necessary time in order to make operative the protection system.

This system may operate also where the bottom 32 of the channel 30 has not been previously levelled, because the barriers 202 may be positioned at different heights (see figure 10).

This innovation produces a solution wherein it is possible to change the position of the mobile element 220 in a very short time, since it is sufficient to raise the barriers 202 and to move the element 220 to a new required postion and, at last, to lower the barriers 202.

In figure 12 there is represented 3 mobile elements 220a, 220b, 220c which are located between a double row of reference elements 206,208 (also illustrated in fig. 11), as for example mooring masts inserted in the bottom 32 of the channel 30, so as to be firmly kept in place in case of strong currents and sea-storms.

The three mobile elements 220a, 220b, 220c are illustrated in the operative position wherein they are aligned and touch each other, so as to form a barrier against the passage of water.

In figure 13 there is represented a mobile element 320 which represents an alternative to the mobile element 220 illustrated in figures 10 and 11. The mobile element 320 is provided with several operating barriers or barricades 302 hinged to its bottom 322a, positioned side by side, placed near each of the two lateral sides and which extend for all the length of the mobile element 320.

In the inoperative position, the operating barriers 302 are raised up (as represented on

the right side of fig. 13) and, therefore, they do not project out from the bottom 322a of the mobile element 320 whereas, in the operative position, they are lowered (as represented on the left side of fig. 13) until they contact, or almost, the bottom 32 of the channel 30.

Even the mobile element 320 is housed between a double row of reference elements 206,208, in an identical manner like the mobile element 220 illustrated in figures 11 and 12.

In order to construct an installation for the operating barrier for the channel 30, there exist different solutions depending on the number of mobile elements 20,220, 320 which are used (which depends on the width of the channel 30 with respect to the length of the mobile element 20,220, 320), and on the fact that the barrier is built somewhere in the middle of the channel 30 or at one end or the other. In order to simplify the explanation, the following description and its corrisponding figures only make reference to the mobile element 20, but it is understood that this applies also to the mobile elements 220,320.

First, we will examine barriers constructed at the ends of channels.

In figure 14 there is represented, from the top, a first installation 100 installed in a channel 30 defined by a left bank 37 and a right bank 38. The channel 30 has a first end, not visible in figure, which flows into a lagoon, a port or the like, and a second end which flows into the sea 101 and made by ends 37a, 38a respectively of the banks 37,38 of the channel 30.

The barrier is built at the ends 37a, 38a by using two mobile elements 20a, 20b, each of them having a length less than the width of the channel 30 and which in the operative position, are arranged in a direction essentialy perpendicular to that of the channel 30. The mobile elements 20a, 20b operate in a symmetrical manner with respect to the middle axis of the channel 30: the mobile element 20a operates near the left end 37a of the channel 30, whereas the mobile element 20b operates near the right end 38a of the channel 30.

Near the ends 37a, 38a respectively of the banks 37,38 and in a direction essentially perpendicular to the banks 37,38, there are located reference elements 102,104, such as mooring masts, so as to exactly position the mobile elements 20a, 20b in a direction perpendicular to the direction of the channel 30 and touching the ends 37a, 38a of the banks 37,38.

More precisely, at the end 37a there is a first reference element 102a positioned outside the channel, a second reference element 102b positioned in front of the end 37a and a third reference element 102c positioned inside the channel 30, and all three reference elements are aligned to each other.

Similarly, at the end 38a of the right bank 38 there are three reference elements 104a, b, c placed in a symmetric manner with respect to the reference elements 102a, b, c.

The positioning of the mobile element 20a occurs by approaching and touching the first reference element 102a (indicated in figure by the dash-line) with the bow 22b and by rotating the mobile element 20a until the stern 22c abuts against the second reference element 102b. At this point the mobile element 20a comes back until it reaches the desired position so executing the above-mentioned phase 1. The other subsequent above-described phases are carried out and the mobile element 20a is sunk and rested on the bottom 32a of the channel 30.

The mobile element 20b is manoeuvred in the same manner.

In figure 14 there is represented, by a continuous line, the final sinking position reached by the two mobile elements 20a, 20b, which corresponds to a closing of the channel of 60%.

In figure 15 the complete closing of the channel has been made (equal to 100%) in which the stems 22c of both the mobile elements 20a, 20b touch one another.

It is evident that by positioning the mobile elements 20a, 20b in a suitable manner, the closing of the channel may vary from a zero value to a maximum value of 100%.

In the particular case in which the channel 30 is very large, in order to completely close the channel, it is necesary to construct an installation 120 similar to the installation 100, but using a third mobile element 20c able to close also the gap between the two mobile elements 20a, 20b, as indicated in figure 16.

In a similar way, in case the channel 30 is narrow, it is possible to use only one mobile element 20, the width of which is greater than the width of the channel 30.

Now, let's examine the barrier built within the channel.

In figure 17 there is represented an installation 130 made in the middle part of the channel which is defined by banks 37,38. Two mobile elements 20a, 20b are used and are respectively positioned thanks to the pairs of reference elements 102a, 102b and 104a, 104b.

In figure 18 there is represented an installation 140 comprising a sole mobile element 20, a stationary barrier 110 placed across the channel 30 and a reference element 102a for the positioning of the mobile element 20.

In both the installation 130 and the installation 140, by differentely positioning the mobile elements 20a, 20b, it is possible to vary the closing from a minimum desired value to a maximum value of 100%.

For the manoeuvring and the positioning of the mobile elements 20a, 20b, each element is provided with its own propulsion means 28 (see figure 1) of the known type, or alternatively, they may be towed by towboats.

In figures 19 and 20, there are illustrated means for keeping the mobile elements 20 in the operative position, which are entirely indicated with reference 400. The keeping means 400 comprise sinkers 402, i. e. anchorage blocks inserted in the bottom 32 of the channel 30 which are provided with foundation posts 404, which by means of chains or ropes 406 are connected to the mobile elements 20 and put in tension when the latter are in the operative position.

In order to facilitate the anchoring or mooring operation of the mobile elements 20 with the sinkers 402, floatation buoys 408, which are connected to the sinkers 402 by means of ropes or chains 410, are used. For the anchoring of the mobile element 20, it is sufficient to take the buoy 408 and join it to the chain or rope 406.

In case of the closing installation of figure 19, wherein two mobile elements 20a, 20b are used for closing the channel 30, there are two sinkers each of them connected to a floating buoy 408a, 408b to which, by means of chains or ropes 406a, 406b, the mobile elements 20a ad 20b are respectively held down.

From the same figure, it can be seen that it is sufficient to have only one reference element 102 for the mobile element 20a and one reference element 104 for the mobile element 20b, each of them respectively arranged at the end 37a of the left bank 37 and at the end 38a of the right bank 38 of the channel 30.

The keeping system 400 allows for the adjusting of the closure rate of the channel 30, since it is sufficient to slaken the chains or ropes 406, to move ahead or back the mobile elements 20a, 20b and, at last, put into tension the chains or ropes 406.

Furthermore, it is possible to use the keeping system 400 also for the manoeuvring of the mobile elements 20a, 20b, in order to vary the opening rate of the channel 30. In fact, by slakening and/or pulling in the chains or ropes 406, it is possible to rotate the

mobile elements 20a, 20b around the respective sinkers 402.

Obviously, this solution may be used also for a closing installation placed inside the channel 30, instead of at its end. In this case, the chains or ropes 406 may also be secured to the banks by means of mooring bitts.

In figure 21 there is illustrated an installation 150 for the safeguarding of Venice which comprises an operating barrier for each of the three port mouths of Lido, Malamocco and Chioggia.

For each port mouth, there are used two mobile elements 20a, 20b to be positioned at the ends of the mouths flowing into the sea for a total of six mobile elements 20. A third mobile element 20c is also used in order to completely close the port mouth of the Lido (since the two mobile elements 20a, 20b are insufficient) as already described with reference to figure 16. Furthermore, the third mobile element 20c is able to substitute for any of the six mobile elements 20a, 20b in case one of them should fail. Obviously, all the mobile elements 20a, 20b, 20c are equal to each other so as to be interchangeable.

Each mobile element is provided with an operating and control apparatus and each apparatus is connected with a centralized control and supervision system which, depending on the forecasted tide, co-ordinates the manoeuvres that each mobile element has to carry out.

As already indicated, thanks to their rapidness, the mobile elements 20a, 20b, 20c may be positioned and sunk in a short time. This permits an efficient protection against the high tides which, otherwise, would create the phenomenon of the high water in Venice allowing, however, for the navigation of liners, oil-tankers and fishing-boats.

If the overall closing percentage of the port mouths reaches 100%, the barrier system is able to hold back very exceptional tides.

The construction of such an installation is simple, since the mobile elements are made in a shipyard and, "in loco", it is sufficient only to level the bottom of the channels and insert support blocks, and to place reference elements. Even this last operation can be avoided if the mobile elements 220 and 320, respectively provided with mobile barriers 202,302, are used.

In case the mobile element 20 is used, the overweighting phase increases the capability of the device to withstand the force of strong sea-storms and winds like "Bora".

Preferably, each mobile element 20 is provided with a breakwater or a breakwave, near the area where it is struck by the waves when it rests on the bottom of the channel 30, so as to absorb the energy of the waves, thus reducing the impact and the force of the waves against the mobile element.

This solution has been illustrated with reference to Venice, but it may be used in any other situation wherein it is necessary to protect a basin, a lagoon, a port or the like, having two or more channels which flow into the sea.

The described device and pertinent intallations have the aim of creating an operating barrier by preventing the passage of water if they are completely closed, or by limiting the passage of water in case of partial closing, thus protecting a city, a port, a land and others from high waters.

The device and the pertinent installations may be used also in order to empty a basin, a lagoon or others in case of necessity, by providing the mobile elements with water- scooping machines.

Moreover, it is possible to use these installations near a river mouth in case of flooding when the sea is not able to handle the water brought by the river. With the above. described installation, on one side the sea water is prevented from entering the river, and on the other side by using the water-scooping machines, the water of the river is discharged into the sea, without the risk that it may come back in.

It is evident that any conceptually or functionally equivalent variation or modification falls inside the protection field of the present invention.

For example, it is possible to increase the number of mobile elements, to vary the number of the compartments or to use another lay-out for the hydraulic circuit or a number of hydraulic circuits different from the number of the compartments in which the hull has been divided.

The mobile elements may be positioned differently with respect to the direction of the channel. The installations may use other kinds of reference elements for the positioning of the mobile elements.