WO2013030810A1

WO2013030810A1 - Structure and method for protection against tsunami -waves and high sea-waves caused by storms

Info

Publication number: WO2013030810A1
Application number: PCT/IB2012/054543
Authority: WO
Inventors: Hans Scheel
Original assignee: Hans Scheel
Priority date: 2011-09-02
Filing date: 2012-09-03
Publication date: 2013-03-07

Abstract

A barrier system adapted to withstand pressure waves under water whereby the barrier system is configured to reflect a pressure wave transmitted through water and under the sea level (1) as a consequence from a geological event that is one from a list comprising at least earthquakes, landslides, asteroids, comets, volcanic eruptions, the system comprising at least a continuous first vertical barrier (8), whereby vertical is defined to be either at a right angle with the sea surface or departing in an angle of maximum plus /minus 25 degrees from the right angle, said barrier being furthermore adapted to be located close to a location where there is a significant reduction of water depth.

Description

STRUCTURE AND METHOD FOR PROTECTION AGAINST TSUNAMI -WAVES AND HIGH SEA-WAVES CAUSED BY STORMS

Field of invention

The invention relates to devices and methods for the protection against Tsunamis. More precisely, the invention relates to using vertical reflecting barriers or walls to reflect pressure waves below sea surface to prevent formation of catastrophic high Tsunami waves, and at the same time creating a possibility to gain new land surface.

Background of the invention

From earthquakes in the ocean, in coastal landslides and submarine landslides, during volcanic eruptions, but also from comets and asteroids falling into sea, pressure waves are initiated that propagate at high speed (-700 km / h) with initially small increase of the water surface. With decreasing depth of the sea towards the coast, the kinetic wave energy of the pressure wave is successively transformed to potential energy by increasing height of the Tsunami waves. In Indonesia and Japan, earthquakes of magnitude greater than 6.5 occurring less than 50 km below the seabed cause such shock waves. From statistical data the magnitude of Tsunami m has been related to the Richter-scale magnitude M of the earthquake by

m = 2.61 M - 18.44

Thus the magnitude m = 2 leads to waves of 4 to 6 m height and coastal damage and lost lives in land- ward areas, m = 3 to waves of 10 to 20 m height causing considerable damage along more than 400 km coastline, and m = 4 leads to waves of 30 m height causing considerable damage along more than 500 km coastline.

Also the type of displacement from the earthquake is important: a vertical displacement of the seafloor is catastrophic, whereas a horizontal strike-slip motion is less harmful.

In the area of the North Atlantic, global warming may firstly cause a destabilization of gas hydrates on the ocean ground, secondly a basic weight shift caused by melting ice sheets, and these may cause massive landslides and earthquakes which then generate pressure waves (Berndt et al. 2009). In other areas shock waves can be triggered by underwater landslides (Hornbach et al. 2007, 2008) whereby the topography of the seafloor plays a role. If these pressure waves near the shore hit a reduction in water depth, sea waves are formed the height of which depends, among other factors, on the inclination of the seabed and on the intensity of the blast. Here, the first very long wavelength of the pressure wave is greatly reduced, so that its energy leads to an increase in amplitude, so that a Tsunami wave of up to 35 m height is formed, kinetic energy is partially transformed to potential energy.

These Tsunami waves have led to major disasters, which claimed many lives and caused huge property damage (e.g. in 1703, Awa / Japan > 100,000 deaths; 1883 Krakatoa explosion > 36,000 deaths; 26.12.2004 earthquake of level 9.1-9.3 in Indonesia > 230,000 Tsunami deaths; and the 8.9-level earthquake of 11.3.2011 Tohoku / Japan caused > 26,000 Tsunami deaths and the Fukushima nuclear power plant accident).

The maximum heights of Tsunami waves caused by landslides in North Atlantic can be calculated according to Berndt (2009). For numerical simulations of Tsunami waves and their behaviour the software COULWAVE of Lynett and Liu (2002, 2011) and its modifications have been widely used. A thorough literature study combined with laboratory experiments and numerical simulations have been described in the PhD thesis (2011) of A. Strusinska of the group of H. Oumeracy. The majority of studies concentrated on descriptions of Tsunami wave behaviour and on possibilities to reduce the energy of high Tsunami waves by breakwaters / artificial reefs and by other means. Thereby the breaking of Tsunami waves is essential to reduce their energy (Iwata et al. 1996, Strusinska 2011). A broad (wide) breakwater may reduce the Tsunami energy by only 25%, so that for reducing Tsunami risks a "multi-defence line protection system would be required" according to Strusinska.

There are many Tsunami-warning systems (Google gives over 1.9 million citations), but for most victims the warning comes too late, and also huge property damages can hardly be avoided. The warning systems are extremely expensive, a single buoy can cost up to $ 1 million (Kristen Gelineau and Tim Sullivan in USA Today 29.10.2010). In USA the National Oceanic and Atmosphere Administration NOAA is coordinating Tsunami warning and protection efforts, and has an archive of Tsunami conferences and workshops.

Earlier proposals to reduce the Tsunami risks include the following:

Researchers at Iowa State University, at the request of the UN Food and Agriculture Organization (FAO), have proposed coastal forests as 'Bioshield' (Science Daily 16.4.2007).

The former Japanese Prime Minister Naoto Kan in 2011 had proposed that the reconstruction of villages is allowed only at higher land levels, which means for fishermen a longer route to the port.

The Ports and Harbours Bureau of Japan Ministry of Land, Infrastructure, Transport and Tourism has proposed a combination of "Submerged Breakwater, Artificial Beach Nourishment and Gentle Slope-type levee" as an "integrated shore protection system" which was realized at the Kamaishi Port, Iwate Prefecture, Japan: From 1978 to March 2009 (in 31 years!) this Tsunami Protection Breakwater has been built at cost of 1.5 billion USD and was celebrated on Monday September 27, 2010 as worldwide deepest breakwater for the Guinness Book of World Records. However, with its length of 1960 m and depth of 63 m it could not protect the harbour and city of Kamaishi, so that the Tsunami caused by the magnitude 9 earthquake of March 11, 2011 had catastrophic effects and killed about 1000 people. The breakwater was partially destroyed. Similarly, the fishing village Taro north of Kamaishi was destroyed with 100 fatalities, although population believed in their double sea walls. The journalist Norimitsu Onishi was critical in New York Times March 31, 2011 of Japan's use of seawalls.

Japanese patent application JP 7113219 discloses several breakwaters, which successively reduce the energy of the„overtopping" Tsunami wave so that it is hoped that the dam on the land will hold up the residual Tsunami wave. 1. The efficiency of this structure is depending on the sea bottom slope in front of the first breakwater; on the height of the first breakwater versus the height from the bottom of the sea and the distance from the coastline; on the height of the submerged breakwater versus the sealevel at the arrival of the tsunami shock wave; and on the slope and height of the bottom structure, the reduction of the Tsunami pressure wave is small. The main effect of the structure disclosed in JP 7113219 is to fight against the Tsunami wave and its energy whereby it is hoped that the breakwater dam on the land will stop the reduced Tsunami wave and will survive the Tsunami wave. 2. No new land surface is obtained, and no energy is„produced". 3. Disadvantage is that the sea of the harbour is sectioned so that its use is limited. One should either preserve the harbour region, or transform it to very valuable land.

Chinese patent application CN 1804224 discloses the use of a large water bag filled with composite material 50 to 80 m from the coast and a second floating bag partially filled with water and partially with gas, both fixed to the seabed. This may reduce the Tsunami wave somewhat, but would not prevent the formation of the catastrophic Tsunami wave.

There is therefore a need for a novel approach and to find a solution to eliminate or at least reduce the Tsunami risks, to prevent the formation of harmful Tsunami waves.

Description of the invention

The invention is based on the principle that pressure waves are reflected respectively held with minimum erosion by vertical walls. Although slightly rounded wall profiles or slightly inclined walls also have a reasonable reflection effect, the vertical wall has an advantage of facilitated fabrication, control, repair, and cleaning. An inclination seawards of the upper part of the vertical wall can be achieved by hanging triangular structures or triangular structures with upper curvature onto the vertical barrier.

The present invention for the Tsunami protection has, compared to the above proposals and warning systems, significant advantages such as robust security as well as in the acquisition of new land. Here the United Nations Convention on the Law of the Sea has to be considered. The invention serves to solve the Tsunami problem, to protect people and to prevent damages. The high construction costs are partially or largely compensated by the value of new land, and also by a significant reduction of insurance costs for all damages and lives along the risky coastlines.

The invention is based on the reflection of approximately horizontal pressure / shock waves at a vertical wall (barrier) submerged in the sea and fixed to the seaground. If the vertical barrier extends to the seafloor (typically 4 km in the pacific) its total reflection prevents the formation of catastrophic Tsunami waves. If the height of the barrier is less, then the ratio of barrier height to the depth of the sea will approximately determine the strength of the reduced Tsunami wave, thereby neglecting friction on the ground and the interference between on-coming and reflecting shock waves. In this case a barrier above sealevel towards the coastline has to be arranged to stop the reduced Tsunami wave.

The invention relates to structures and methods as defined in the claims.

More precisely, in a first aspect the invention provides a barrier system adapted to withstand pressure waves under water whereby the barrier system is configured to reflect a pressure wave transmitted through water and under the sea level (1) at high tide as a consequence from a geological event that is one from a list comprising at least earthquakes, landslides, asteroids, comets, volcanic eruptions, the system comprising at least a continuous first vertical barrier. Vertical is defined to be either at a right angle with the sea surface or departing in an angle of maximum plus /minus 25 degrees from the right angle. The barrier is furthermore adapted to be located close to a location where there is a significant reduction of water depth, and it extends by at least 5 m above mean sea level in order to reject highest sea waves caused by storms and to prevent overtopping of waves.

In a preferred embodiment the barrier further comprises at least a second vertical barrier and a third vertical barrier in a terrace structure, each one of the second and the third vertical barriers extending below a sea level at high tide. Each one of the second and the third vertical barrier is configured to reflect the pressure wave corresponding to its vertical height, and each one of the second and the third vertical barrier thereby reduces the energy of a Tsunami pressure wave. The first barrier forms a step with a step surface joining a lower part of the first barrier with an upper part of the second vertical barrier located on a front-side of the first vertical barrier, whereby the front-side is defined to be located seawards from the first vertical barrier, and the lower part of a structure refers to a part that is located nearer to the sea bottom than the upper part of the structure. The step surface is substantially flat and horizontal, whereby horizontal is defined to be parallel to the sea surface.

In an other preferred embodiment, the barrier system comprises a further continuous vertical barrier, wherein the further vertical barrier is flexible, and is located on the seawards side of the continuous first vertical barrier. The flexible barrier is adapted to partially reflect the pressure wave, and can have turbines on the upper and lower ends to generate electric energy from inward and outward water flow. These turbines are not destroyed by Tsunami shock waves due to the flexible barrier allowing a fraction of the shock wave to pass through. In a further preferred embodiment the first vertical barrier comprises a vertical fixing means configured to fix the first vertical barrier into the sea bottom substantively along a fixing direction that is vertical; and a sideways fixing means configured to fix the first vertical barrier into the sea bottom on a backside of the first vertical barrier that is opposite to a seawards oriented side on which the pressure wave reaches the barrier.

In an other further embodiment the first vertical barrier is realized as a fence with a vertical fixation in the seafloor by means of vertical pillars, and a sideways fixing means comprises at least one sideways pillar which at one of its ends is in contact with the vertical pillars of the fence, and at the other of its ends is fixed into the sea bottom, whereby an angle between the sideway pillar and the sea surface has a value between 10 degrees and 70 degrees.

In still an other preferred embodiment the fence comprises either one of wire rope fence or a strong wire fence made from saltwater-resistant stainless steel.

In still a further preferred embodiment the first vertical barrier is realized from a plurality of concrete blocks.

In a further embodiment at least a first one of the concrete blocks has a groove on its surface that allows to accommodate a corresponding shape from a neighbouring one of the concrete blocks, in order to fix the first one of the concrete blocks to the neighbouring block.

In a further embodiment, the barrier system comprises at least a steel rod, whereby the at least one steel rod is configured to attach at least one of the concrete blocks to an other one of the plurality of concrete block, and further is configured to anchor the at least one of the concrete blocks to the sea bottom.

In an other embodiment the barrier system comprises in a region located on a backside of the first vertical barrier, towards the coast, filling material that is one of a list comprising at least any suitable material, rocks, building rubble, gravel, sand, soil, whereby the filling material supports the vertical barrier, thereby achieving a mechanical stability against the pressure wave, that is improved as compared to the mechanical stability of the vertical barrier without filling material, and whereby the filling generates new land surface.

In a preferred embodiment, the barrier system further comprises at least an additional vertical barrier forming a step with respect to an other vertical barrier of the barrier in a configuration similar as described for the first barrier.

In a preferred embodiment at least one of the vertical barriers or of the horizontal terrace steps is realized from a prefabricated structure of steel plates or concrete.

In a preferred embodiment each step of the terrace structure has a height comprised between 5 meters and more than 20 meters. In still a further preferred embodiment the top of the first vertical barrier has a provision for future heightening of the vertical barrier in case that the mean sea level is increasing with climate change, or that higher storm-driven sea waves are expected.

In a second aspect, the invention provides a barrier system that comprises a steep nearly vertical wall near or at the coast, which is built by digging / excavation, so that the deep sea level extends to the coast, whereby the nearly vertical wall is adapted to reflect a pressure wave transmitted through water and under the sea level at high tide as a consequence from a geological event that is one from a list comprising earthquakes and landslides, and whereby vertical is a direction defined to be substantially at a right angle with the sea surface.

In a third aspect, the invention provides a method for installing a barrier system as described herein, wherein said barrier system comprises the first vertical barrier, the method comprising locating the first vertical barrier close to the beginning of a significant reduction of water depth.

In a fourth aspect, the invention provides a method for concrete wall fabrication on site by pouring concrete slurry into the gap between two provisional vertical walls, into which a steel rod structure has been introduced, and by vibration or sound activation to compact the slurry before solidification, in analogy to concrete wall production on the ground, the concrete having a salt-water resistant composition.

Brief description of the figures

The invention will now be explained through the description of preferred embodiments while referring to figures, as listed herein below:

figure 1 illustrates a schematic cross-section of an on-site vertical barrier according to a first preferred embodiment of the invention;

figure 2 illustrates a schematic cross-section of an on-site terrace structure barrier according to the invention;

figure 3 illustrates a schematic cross-section of an on-site flexible vertical barrier according to the invention; and

figure 4 illustrates a schematic cross-section an example of a steep nearly vertical wall at the coast according to the invention. Description of preferred embodiments

Tsunami barrier

Vertical barrier

In a first embodiment (see fig. 1) the invention comprises a continuous solid vertical barrier 8 that is established in the sea 1 , 2 off the coast, where the water depth decreases significantly.

The references used in fig. 1 are as follows:

1 Sea level at high tide;

2 Bottom of the sea;

3 Steep slope of seafloor;

4 Medium steep slope of seafloor;

5 Small slope of seafloor;

6 Coast;

7 New reclaimed land filled with rocks, rubble, gravel, sand, soil etc.;

8 Fixed Tsunami barrier to reflect pressure waves below sea level and is extended above sea level to protect against residual Tsunami waves and high ocean waves (6 m to 10 m above high-tide level);

9 Vertical fixing in the solid ground

10 Sideways fixation in solid ground.

The solid barrier 8 can withstand the pressure of the shock wave (shock wave not illustrated in fig. 1). Alternatively a flexible barrier (not shown in fig. 1, but represented in fig. 3)) may be used that significantly reduces the impact of the Tsunami pressure wave. In the following, we call this solid barrier 8 or flexible barrier 12, respectively "Fixed Tsunami Barrier" and alternative "Flexible Tsunami Barrier." The barriers according to the invention are referred to "Scheel-Tsunami-Barriers" or STB. They have to withstand only pressure waves under water, not destructive high-speed water masses with alternating pressure and cavitation effects and very high flow velocities acting on breakwaters and on dams with slopes.

These STB barriers can reach the sea level at high tide 1 or protrude from the sea, but they can also end by a gap (not shown in fig. 1) below the sea surface for fishing, navigation or for the exchange of water. This "gap" of course must take into account the tides (high tide and low tide) and causes a reduced Tsunami protection effect. Another possibility for navigation are navigable channels (not shown in fig. 1) at a small angle nearly parallel to the Tsunami barrier, by which the port (not shown in fig. 1) can be reached. The approximately vertical barriers are led around the coastline 6 whereby their morphology can be adapted to the sea floor 2 topography. But the Tsunami Barriers can also be a straight wall or be wave-shaped or zigzag-shaped or irregular. A zigzag- or wave-shaped barrier can be designed so that reflected shock waves from different directions interfere in order to reduce their kinetic energy, but a complete annihilation of the shock wave will not occur. The depth of the Tsunami barriers has to be matched to the slope 3, 4, 5 of the seafloor: when near the coast the rising slope between the ("horizontal") deep ocean seafloor (typically > 1 km up to 4 km) to the shallow coastal floor is more than about 120 degrees (or when the average angle of the sea-ground towards the coast deviates more than 30 degrees from vertical.), the reflection of the pressure wave by this natural less steep slope is reduced so that the Tsunami barrier should be built in this region. Depending on this critical range the Tsunami barrier has to be at least 50 m and even more than 1 km deep. Ideally, the STB should extend to the ocean ground, to its lowest level 2 as is shown in Fig. 1. If this is not possible, or internationally not accepted, or too expensive, the STB should be realized to its maximum total height according to 8 as shown in Fig. 1. Depending on the slope 3 and the height difference, a reduced Tsunami wave may be formed which requires a corresponding height of the protection wall above sea level. Although the coincidence of Tsunami waves and highest waves from tropical storms will be rare, the protection wall above sea level has to take this risk into account and should be higher than the highest expected sea-wave, for example 8 m high. The length of the continuous Tsunami Barrier has to be larger than the coastline to be protected, depending on the coast geography, between 1 to 10 km longer, because the Tsunami pressure wave may arrive at an angle strongly deviating from 90 degrees towards the coastline. The coastline protected by Tsunami Barriers should be protected from the sides as well, so that Tsunami waves from non-protected coast cannot enter from the side. This side protection can be made from Tsunami Barriers or from high walls or from stable high continuous buildings, in case there are no natural barriers like hills against the flood.

The fixed vertical barrier has the effect that most of the pressure wave energy is reflected and another part leads to an upsurge foaming of the waters along the barrier.

Through calculations, the construction and reinforcement of the barrier has to be matched to local conditions of the ground and to the earthquake and tsunami risks. A zigzag or wavy structure of the barrier has the advantage that the foaming effect is somewhat spread, but the disadvantage that the total length of the barrier is extended and associated with increased costs.

In a preferred embodiment, the top of the fixed Tsunami barrier (8) has provision for future heightening of the barrier in case that the mean sea level is increasing with climate change, or that higher storm-driven sea waves are expected. This provision can consist of steel bars extending over the barrier (8).

Step structure

If the bottom of the sea is not steep, but continuously rising, a step structure with vertical steps as modified STB is easier to construct (see fig. 2).

In fig. 2, reference 11 corresponds to fixed Tsunami barriers below sea level in terrace construction.

The minimum step height should be calculated and should be as high as possible for highest reflectivity, preferably more than 20 m, but should be at least 5 m, and the step distance depends on the slope of the bottom of the sea. The step structure can be prefabricated from steel plates or concrete, or can be designed as indicated below. The gap behind the steps may advantageously be filled with rocks, gravel, sand etc. for mechanical strength, or excavated to achieve a horizontal surface. Step heights and the slope of the step structure should reflect at least 40 % of the Tsunami-causing pressure wave. The bottom slope of the sea has to be dredged (excavated) to increase verticality whereby the excavated material is used to fill any gaps behind the large barriers, extending above sea level, towards the coastline to "produce" artificial valuable land.

General considerations

Signal lamps, buoys and audible signals are set up along the Tsunami Barrier in order to warn boats and ships of tsunami danger prior to foaming and to keep them away from the barrier. The optimal structure of barrier and possibly a slight deviation from the vertical installation may be determined by computer simulation that takes into account the local geology and morphology of the seafloor, the depth, the required distance to the sea level at high tide and other factors.

Flexible Barrier

Fig. 3 illustrates a schematic cross section of an example of a flexible STB barrier wherein following references are added:

12 Flexible Tsunami Barrier;

13 turbine for inward flow; and

14 turbine for outward flow.

The flexible STB barrier of fig. 3 reflects some of the pressure of the pressure wave, or it diffracts / refracts the wave and changes its direction, or it causes interference so that wave components are neutralized. Another part of the wave is converted into frothing, and some pressure is neutralized by deflecting the heavy swing barrier or the hanging rods and grids. The residual pressure will continue, however, and must be blocked by a further fixed or flexible barrier or through a solid wall on the coast. This wall is much lower than the wall without Tsunami Barrier. The water flow above and below the flexible barrier can drive turbines for electricity production as schematically indicated in Fig. 3.

Example material for vertical barrier

The simplest design for the first high solid STB barrier and for the barriers of the step structure mentioned above consists of a strong wire fence or wire rope fence (e.g. from a salt water-resistant stainless steel, for instance from GEOBRUGG AG-Geohazard Solutions, Romanshorn, Switzerland) which is held with the seabed precautions (e.g. pillars fixed in the ground vertically and at an angle of typically 40 to 90 degrees towards the coast). In the direction coast the space in front of the grid is filled with rock, building rubble, sand, soil, etc. to withstand the shock waves. Preferably the gap between STB and coastline is filled to a height of say 3 m above sea-level so that new valuable land is generated. The total volume of the new land up to the sealevel will be small with respect to the total volume of the ocean, so that the effect on the ocean sea level will be negligible and small compared to the rising sealevel expected from global warming.

Another construction consists of concrete blocks which are lowered by crane ships with the help of divers, underwater cameras and detectors, and which are locked together by grooves or steel rods and anchored to the seabed. The bottom row of concrete blocks can be adjusted to the seabed morphology. Also the space between the wall of concrete blocks towards the coast is filled with rock, rubble, sand, soil, etc. for generating new land surface. Still another method to construct a vertical STB barrier is on-site fabrication of the barrier by filling concrete between vertical walls or grids in analogy to concrete construction on the ground.

Instead of special stainless steel and concrete, also other building materials can be used which are locally available, even provisional wooden fortified walls, but the coast side has to be filled with sufficient mass. The construction of the STB has to be stable to withstand strongest earthquakes (of magnitude 9 or locally 9.5), it has to withstand the pressure shock waves from such earthquakes, and it has to withstand the erosion effects from the sea. Furthermore, the barriers have to be controlled regularly for damage and for collected deposits in front of the barriers, which would reduce the effectiveness of the nearly vertical barriers. Deposited material like rocks and sand in front of the barriers (towards the sea) has to be removed when reaching a critical level. The vertical walls of the STB facilitate inspection and cleaning.

The flexible tsunami barrier consists of horizontal bars or strong steel ropes between pillars that hold the hanging heavy metal or stone plates, or it is made of heavy metal plates or concrete slabs with lateral pivoting devices (rotary bearing on the seabed pillar). An alternative construction consists of vertical rods or grids, which are hanging from the surface or fixed at the sea ground, with the function of diffracting the pressure wave and / or interfering the wave to reduce its energy and its propagation towards the coastline.

At the points where larger water depths are required for shipping, lockable gates are set up, as they are realized for example in the Netherlands, and these gates have to resist the pressure wave. These gates are automatically locked upon tsunami warning.

Geographical location for barriers

The fixed or flexible tsunami barriers are urgently to be set up along those coastlines, where nuclear power plants, towns, villages, ports, airports (Sendai, Schiphol, etc.) and other important works of civilization must be protected. Ships in the ports are also protected, they must withstand only a small tsunami height, caused by the pressure wave components at the sites of gap, where the barrier does not reach the sea surface, or happens where a fraction of the shock pressure passes the flexible barrier.

In addition to protecting people and property, the inventive tsunami barriers have the important advantage that over the years, by alluvial material from the rivers or by artificial measures / embankment the field between the coast and the first barrier can be won as a new land (see Osaka International Airport). The high construction costs of the Tsunami Barriers can partially or even totally be compensated by the value of the new land.

Tsunami Barriers can be classified as special vertical types of breakwaters or artificial reefs or sea walls, but they are different from dams and breakwaters, which have slopes and are much less effective against Tsunami waves and against the actions of the sea. The average flow velocity along the vertical barriers will be significantly lower than the aggressive flows along and across normal breakwaters and dams, and cavitation below sealevel is not expected. Therefore, also from the corrosion point of view, vertical walls should be applied in coastal constructions whenever possible.

The term "vertical" is defined as right angle to the sea surface.

In the present text the term "vertical" applied to the barrier should be understood as not vertical in the geometrical sense but as steep enough so that the pressure wave is largely reflected and that formation of Tsunami sea waves is prevented. Expressed differently, geometrically the barrier according to the invention may be vertical or slightly deviated from the vertical, for instance by an inclined or a rounded structure.

The barrier according to the invention should furthermore be understood as also encompassing a steep nearly vertical wall 17 near or at the coast, which is built by digging / excavation, so that the deep sea level extends to the coast as is shown in Fig. 4.

Fig. 4 illustrates an example of a steep nearly vertical wall at the coast wherein following references are added:

15 barrier against high seawaves and reduced Tsunami waves;

16 fixation;

17 new vertical wall at the coast;

18 material (rocks, sand) to be excavated and removed;

19 coast.

This wall acts then to reflect the shock waves. If this vertical wall does not extend to the deep sea-ground, the Tsunami pressure wave energy will only partially be reflected so that a high vertical wall at the coastline with proper fixation has to be installed in order to defend remaining Tsunami wave and also highest sea-waves from storms. The excavated material like rocks, gravel, sand etc. could be used to fill up the land behind nearby STB barriers at other parts of the coast. Thus, a combination of excavated vertical walls at some parts of the coast with vertical barriers submerged in the sea at other parts of the coast could be practical and economic.

The flexible STB according to the invention may also be advantageously combined with energy "production" by using the energy of the ocean waves and of the tidal height differences and movements: Turbines for inward flow and for outward flow generating electricity (New York City) or hinged anchored cylinders that are pushed by waves and turn onshore turbines that produce electricity (Orkney, Scotland). Since the realization of the STB would take some time (several months or even years), an early reduction of the next pressure waves can be achieved dynamically by a row of explosions before the pressure waves reach shallow sea bottom and cause high Tsunami waves. From signals from Tsunami warning systems the movement of the pressure wave from the earthquake is analysed and coordinated with the explosions. Chains of bombs, rockets or any suitable objects are brought to explosion below the sea surface near the pressure wavefront in order to spread the oncoming pressure waves so that the resulting Tsunami waves are significantly reduced.

References

C. Berndt, S. Brune, E. Nisbet, J. Zschau und S.V. Sobolev, "Tsunami modeling of a submarine landslide in the Fram Strait", in Geochemistry, Geophysics, Geosystems G3 Vol.10 No.4, 9. April 2009 (Q04009).

M.J. Hornbach et al., "Triggering mechanism and tsunamogenic potential of the Cape Fear Slide complex", U.S. Atlantic margin, Geochem. Geophys. Geosyst. G3 Vol.8(2007) Q12008.

M.J. Hornbach et al., "Did a submarine slide trigger the 1918 Puerto Rico tsunami?", Sci.Tsunami Hazards 27(2) (2008) 22-31.

P. Lynett and P.L.-F. Liu, "A numerical study of submarine-landslide-generated waves and run-up", Philos.Trans.Roy.Soc.A 458(2002)2885-2910; "Simulation of complex Tsunami behavior", Computing in Science and Engineering Magazine 13(4), July/August 2011, 50-57.

A. Strusinska, "Hydraulic performance of an impermeable submerged structure for tsunami damping", PhD thesis 2010, published by ibidem- Verlag Stuttgart, Germany 2011 (ISBN-13: 978-3-8382-0212-9).

Claims

1. A barrier system adapted to withstand pressure waves under water whereby the barrier system is configured to reflect a pressure wave transmitted through water and under the sea level (1) as a consequence from a geological event that is one from a list comprising at least earthquakes, landslides, asteroids, comets, volcanic eruptions, the system comprising at least a continuous first vertical barrier, whereby vertical is defined to be either at a right angle with the sea surface or departing in an angle of maximum plus /minus 25 degrees from the right angle, said barrier being furthermore adapted to be located close to a location where there is a significant reduction of water depth, and extending by at least 5m above mean sea level in order to reject highest sea waves caused by storms and to prevent overtopping of waves.

2. The barrier system of claim 1, further comprising

at least a second vertical barrier and a third vertical barrier, each one of the second and the third vertical barriers extending below the sea level (1), whereby each one of the second and the third vertical barrier is configured to reflect the pressure wave corresponding to its vertical height, and whereby each one of the second and the third vertical barrier (8) thereby reduces an energy of a Tsunami pressure wave,

the first barrier (8) forming a step (11) with a step surface joining a lower part of the first barrier (8) with an upper part of the second vertical barrier (11) located on a front-side of the first vertical barrier, whereby the front-side is defined to be located seawards from the first vertical barrier, and the lower part of a structure refers to a part that is located nearer to the sea bottom than the upper part of the structure, the step surface being substantially flat and horizontal, whereby horizontal is defined to be parallel to the sea surface.

3. The barrier system of claim 1 or claim 2, further comprising a further continuous vertical barrier, wherein the further vertical barrier is fiexible, and is located on the seawards side of the continuous first vertical barrier, whereby the flexible barrier is adapted to partially reflect the pressure wave.

4. The barrier system of any one of the previous claims,

the first vertical barrier (8) comprising

a vertical fixing means (9) configured to fix the first vertical barrier (8) into the sea bottom substantively along a fixing direction that is vertical; and a sideways fixing means (10) configured to fix the first vertical barrier (8) into the sea bottom on a backside of the first vertical barrier (8) that is opposite to a seawards oriented side on which the pressure wave reaches the barrier.

5. The barrier system according to either one of claims 1 and 2, wherein the first vertical barrier is realized as a fence with a vertical fixation in the seafioor by means of vertical pillars, and a sideways fixing means comprises at least one sideways pillar which at one of its ends is in contact with the vertical pillars of the fence, and at the other of its ends is fixed into the sea bottom, whereby an angle between the sideway pillar and the sea surface has a value between 10 degrees and 70 degrees.

6. The barrier system according to claim 5, wherein the fence comprises either one of wire rope fence or a strong wire fence made from saltwater-resistant stainless steel.

7. The barrier system according to either one of claims 1 and 2, wherein the first vertical barrier is realized from a plurality of concrete blocks.

8. The barrier system according to claim 7, wherein at least a first one of the concrete blocks has a groove on its surface that allows to accommodate a corresponding shape from a neighbouring one of the concrete blocks, in order to fix the first one of the concrete blocks to the neighbouring block.

9. The barrier system according to claim 7, further comprising at least a steel rod, whereby the at least one steel rod is configured to attach at least one of the concrete blocks to an other one of the plurality of concrete block, and further is configured to anchor the at least one of the concrete blocks to the sea bottom.

10. The barrier system according to any one of claims 1 to 9, further comprising in a region located on a backside of the first vertical barrier, towards the coast, filling material that is one of a list comprising at least any suitable material, rocks, building rubble, gravel, sand, soil, whereby the filling material supports the vertical barrier, thereby achieving a mechanical stability against the pressure wave, that is improved as compared to the mechanical stability of the vertical barrier without filling material; and whereby the filling generates new land surface.

11. The barrier system of claim 2, further comprising at least an additional vertical barrier forming a step with respect to an other vertical barrier of the barrier in a configuration similar as described for the first barrier.

12. The barrier system of any one of claims 2 or 11, wherein at least one of the vertical barriers or of the horizontal steps is realized from a prefabricated structure of steel plates or concrete.

13. The barrier system of any one of claims 2, 11 or 12, wherein each step has a height comprised between 5 meters and more than 20 meters.

14. The barrier system according to any one of the preceding claims, wherein the top of the first vertical barrier (8, 15) has a provision for future heightening of the vertical barrier in case that the mean sea level is increasing with climate change, or that higher storm-driven sea waves are expected.

15. A barrier system comprising a steep nearly vertical wall (17) near or at the coast, which is built by digging / excavation, so that the deep sea level extends to the coast, whereby the nearly vertical wall is adapted to reflect a pressure wave transmitted through water and under the sea level (1) as a consequence from a geological event that is one from a list comprising earthquakes and landslides, and whereby vertical is a direction defined to be substantially at a right angle with the sea surface.

16. A method for installing a barrier system according to claim 1, wherein said barrier system comprises the first vertical barrier, the method comprising locating the first vertical barrier close to the beginning of a significant reduction of water depth.

17. A Method for concrete wall fabrication on site by pouring concrete slurry into the gap between two provisional vertical walls, into which a steel rod structure has been introduced, and by vibration or sound activation to compact the slurry before solidification, in analogy to concrete wall production on the ground, the concrete having a salt-water resistant composition.