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(11) | EP 4 563 749 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | ARTIFICIALLY TRIGGERED NATURAL BARRIER FOR COASTAL PROTECTION |
| (57) The application presents a natural-based solution to the problem of coastal protection,
based on soft engineering and minimising use of raw materials and energy use. Through
the integration of field work, laboratory analysis, and in situ formation, a multidisciplinary approach incorporating sciences such as geomorphology,
microbiology, geology, morphodynamics and engineering is employed. The process facilitates
the development of an artificially-triggered, but naturally-developed submerged structure,
offering a comprehensive approach to coastal protection that can have diverse applications
in coastal engineering.
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Field of Invention
[0001] The present invention relates to integrated coastal zone management (ICZM) and protection. Particularly, the present invention relates to use of soft engineering to establish an artificially-triggered naturally-developed submerged barrier, to protect a coastline from erosion.
Technical background
[0002] The coastal zone is a complex and dynamic environment. It includes fragile ecosystems such as beaches, dunes, lagoons, wetlands, deltas, as well as archaeological and other cultural sites, and is thus sensitive to both natural processes and human activities. For example, a coastal region is influenced by the extent of exposure of the coast to wave activity, climate (which affects wave patterns and sea level), the type of sediments or rocks that compose it, and its morphology. Human interventions resulting particularly from settlement and tourism, also have a significant effect on coastal regions.
[0003] Coastal erosion, which refers to the permanent removal of coastal materials, is a significant issue that affects the coastal zone at a global scale, threatening natural environments, human settlements and infrastructure worldwide. Various studies have shown that, by the year 2100, up to 50% of the world's sandy beaches may undergo erosion, and rising sea levels and an associated increase in the frequency of storm events, attributed to global climate change, will play a significant role in such erosion. Human activities, such as coastal development and construction activities, also contribute to the destruction of coastal landforms, and the acceleration of coastal erosion rates. Building of dams and anti-flood measures in rivers can result in sediment traps, leading to coastal sediment shortage. Coastal sediments play a key role in the coastal zone - they directly define the characteristics of coastal processes, which can potentially lead to either sediment accumulation or removal, thus changing the morphodynamics and morphology of the coasts, and increasing their vulnerability to erosion.
[0004] It is therefore important to prioritise the preservation and restoration of coastal landforms, in order to maintain the natural balance of the coastal zone and protect it from further erosion and inundation. Typical coastal protection measures include use of hard structures such as seawalls, cantilevers, breakwaters and coastal dikes, which are expensive, highly unattractive and which require constant maintenance.
[0005] Embodiments of the present invention provide a method of establishing an artificially triggered, but naturally developed, structure for protecting a coastline from erosion.
[0006] Embodiments of the present invention aim to provide eco-friendly coastal sustainability by creating such natural barriers on the seabed of sandy beaches that are prone to erosion, while:
- (a) protecting the beach from further erosion,
- (b) lowering CO2 emissions,
- (c) saving building materials and
- (d) leaving the natural beauty of the beach intact, thus attracting tourists and contributing to the local economy.
[0007] A barrier or reef produced according to embodiments of the present invention has similar properties to natural beach rocks. Beachrocks are hard coastal deposits that consist of different beach sediments, lithified near the shoreline through the precipitation of calcite and its polymorphs through physicochemical and biochemical cement precipitation or 'cementation'. Beachrocks act as natural breakwaters, protecting the coast from wave action and encouraging sand accretion. Embodiments of the present invention utilize natural material which is not foreign to a coastal region to be protected, such as existing sediments, sea water and bacteria existing naturally in the beach sand and water, to imitate the natural beachrock characteristic.
Summary of invention
[0008] According to an aspect of the present invention, there is provided a method of establishing a natural coastal protection structure for protecting a coastline from erosion, comprising: excavating an offshore trench in the seabed at a predetermined location, the trench having a predetermined shape and depth; storing sand removed from the seabed by the excavation of the trench; positioning a geotextile shell within the excavated trench, and adding the stored sand to the interior of the geotextile shell to form a sand structure; and supplying a bacterial suspension, of pre-existing bacteria in the site, to the sand structure to initialise biochemical cementation of the sand structure to form the coastal protection structure having substantially the predetermined shape.
[0009] The predetermined location and predetermined shape may be identified based on geomorphological, hydrodynamic and morphodynamic analysis of the coastline environment.
[0010] The method may comprise three-dimensional modelling of the effect on wave motion of a structure having the predetermined shape, and positioned at the predetermined location of the coastline, to verify suitability of the structure for protecting the coastline from erosion.
[0011] The method may comprise selecting the bacterial suspension for supply to the sand structure, and organic solidification solution, based on analysis of the bacteria content of sand and water samples at or near the predetermined location to determine the bacteria most active in causing microbiologically-induced calcite precipitation in the sand samples.
[0012] The method may comprise determining a regime for supply of the bacterial suspension to the sand structure, the supply regime including a rate of supply and a quantity of supply of the bacterial suspension.
[0013] The method may comprise installing a pipe network for supplying the selected bacterial suspension to the sand structure from a storage means, according to the determined supply regime.
[0014] The method may comprise removing the geotextile shell and the pipe network after the sand structure has formed the coastal protection structure.
[0015] The method may comprise determining that the sand structure has formed the coastal protection structure by estimating the progress of cementation of the sand structure by submarine geophysical monitoring, and measuring Ca2+ content and pH levels of liquid samples obtained through the pipe network and extracted at a monitoring device, and comparing the estimated cementation progress with a respective threshold.
[0016] The method may comprise verifying that the sand structure has formed the coastal protection structure by obtaining one or more samples of the sand structure and determining their level of cementation, by analysing one or more of a uniaxial unconfined compressive strength analysis, porosity, organic carbon content, mineralogy, geochemical characteristics, and lignocellulosic biomass composition.
[0017] The cementation of the sand structure may be compared with composition of naturally-occurring material at the coastline, and it may be determined that the sand structure has formed the coastal protection structure when the cemented sand structure has a composition which is substantially the same as naturally-occurring material.
[0018] The method may comprise terminating supply of the bacterial suspension when the sand structure has formed a coastal protection structure.
[0019] The geotextile shell may comprise a porous geotextile material, having a porosity at which the supplied bacterial suspension is contained within the shell.
[0020] The coastal protection structure may be a cemented sand natural barrier for attenuating kinetic wave energy.
[0021] According to another aspect of the present invention, there is provided a natural coastal protection structure produced according to any one of the methods described above.
[0022] Embodiments of the present invention therefore provide a natural-based solution to the problem of coastal protection, based on soft engineering and minimising use of raw materials and energy use. Through the integration of field work, laboratory analysis, and in situ formation, a multidisciplinary approach incorporating sciences such as geomorphology, microbiology, geology, morphodynamics and engineering is employed. The process facilitates the development of an artificially-triggered, but naturally-developed submerged structure, offering a comprehensive approach to coastal protection that can have diverse applications in coastal engineering.
Description of Figures
[0023] Embodiments of the present invention will be described by way of example only, with reference to the accompanying drawings, of which:
Figure 1 is a flow chart illustrating a methodology for constructing a coastal protection structure, within which methods of embodiments of the present invention are performed;
Figure 2 is a flow chart illustrating methods according to embodiments of the present invention; and
Figures 3(a)-(e) are illustrations of a submerged barrier produced according to the methods of embodiments of the present invention.
Detailed description
[0024] A methodology for constructing a coastal protection structure, within which methods of embodiments of the present invention are performed, can be divided into three phases, as illustrated in Figure 1.
(1) Comprehensive preliminary study of the work area
[0025] As set out above, methods of embodiments of the present invention are designed to imitate nature and to follow its processes in the development of a coastal protection structure, without intervention in the natural local environment other than to accelerate a natural cementation processes.
[0026] As such, formation of a coastal protection structure, such as a submerged barrier, relies on the use of natural material native to the area of interest, specifically at the site of a coastal region intended for protection. Such natural material includes sediments, sea water and bacteria existing naturally in the beach sand and water, and this material is used to imitate the natural beachrock characteristic as a breakwater, taking into account the effect of environmental conditions at the coastal region on the growth of the natural barrier.
[0027] Prior to development of the coastal protection structure, there is therefore a need to assess the physical parameters of the coast, and its hydrodynamic regime, in a preliminary process based on geomorphological, hydrodynamic, and morphodynamic studies, so that natural beachrock can be imitated as faithfully as possible. The nature of such assessment is well understood by geoscientists operating in the field of coastal zone analysis, and forms the first phase S10 of the methodology described herein.
[0028] Geomorphological studies include the detailed mapping of the physical and morphological characteristics of the coastal area, using positioning systems such as real-time kinematic positioning (RTK) using global navigation satellite systems (GNSS) and drones, and high-resolution satellite imagining. Geomorphological studies are also carried out in the underwater area where the morphology of the seabed is mapped using geophysical sensors such as sidescan sonar.
[0029] Hydrodynamic studies include the collecting of data of wind (direction, intensity, speed, periodicity) and waves (direction, wave height, speed, periodicity), and performance of a corresponding statistical analysis to determine how such parameters affect the coastal zone. This analysis can be implemented using specific models and/or applications, in a manner known according to the state of the art. Morphodynamic studies include a combination of geomorphological studies and analysis of sediment granulometry, which can be conducted by sampling sediments in specific spatial intervals (on-shore and off-shore), and investigating them in a laboratory using e.g. sieving or particle size laser measurements.
[0030] The outputs of the first phase S10 can be generalised in terms of environmental characteristics 12 of the coastline, and physical characteristics 14, relating to sediments and geometry of a natural barrier structure to be formed, which are input to processes of embodiments of the present invention as defined below.
(2) Laboratory analysis and development of artificial beachrocks
[0031] This second phase S20 of the methodology includes performing laboratory tests in order to identify the bacteria present in the study area, and to identify the most types most active in calcite (CaCO3) precipitation. The nature of such testing is well known according to the state of the art.
[0032] In one example, sand and water samples are analysed in the laboratory to identify bacteria content by performing urea hydrolysis to characterise microbiologically-induced calcite precipitation (MICP). Sand samples are treated for mineralogical analysis using X-ray diffraction (XRD), while water samples are analysed for characteristics such as temperature, CaCO3, Mg2+ and salinity. Both sample types are analysed for bacteria identification through third generation (nanopore) sequencing of the 16S rRNA gene. In parallel, the culturable microbial community is analysed using suitable media such as ZoBell2216E. Isolated strains are characterized (16S rRNA) and their growth kinetics are determined with respect to the corresponding calcium precipitation rates.
[0033] The results are combined with those obtained from urea hydrolysis in order to isolate those bacterial communities which are most active and which will be most effective to trigger natural barrier formation. Their physiology and interactions are studied, to enable production of an artificial inoculant for enhanced natural barrier formation, which is triggered by a natural biocementation process.
[0034] Experiments are then performed in order to test the growth and solidification of the natural barrier, artificially triggered by the identified inoculant. Experiments are conducted by setting a number of experimental parameters and conditions, including qualitative and quantitative aspects of the bacterial populations, CaCO3 content, water-depth in relation to mean sea level (m.s.l.) and water table, the thickness of the resulting natural barrier, and distance from the shoreline. The natural barrier sample development is measured as a function of time.
[0035] The solidified natural barrier is tested to determine its uniaxial unconfined compressive strength (UCS) using needle penetration tests and HCl rinsing is performed to estimate the cement content. The samples are analysed under polarized optical microscopy, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and XRD for correlation with literature analysis of naturally-occurring beach rocks.
[0036] For example, the most common cemental material is a calcite polyform which is observed in naturally-occurring beachrocks. High-magnesium calcite (HMC) contains > 5 mol % MgCO3, along with aragonite crystals. In the lower intertidal zone, beachrock cement consists of acicular aragonite forming isopachous fringes, while HMC cements form bladed isopachous rims or brown-coloured micritic size crystal, pelletal formations, sediment grain coatings and pores fillings. On the other hand, cements of low-magnesium calcite polyform with < 5 mol % MgCO3 are indicative of the meteoric-vadose zone.
[0037] The outputs of the second phase S20 of the methodology can be characterised as a definition of a MICP process 24 used for the natural barrier sample which is developed and tested, in terms of identification active bacteria and parameters characterising the rate of cementation of natural barrier sample, triggered by such bacteria.
(3) In situ application in the coastal region of interest
[0038] After validation of the artificially-triggered cementation process in the lab, in-situ development of the coastal protection structure can be performed. This third phase S30 of the described methodology represents methods of embodiments of the present invention which are described below in relation to the construction of an artificially-triggered natural barrier.
[0039] Figure 2 shows a methodology of embodiments of the present invention. The methodology shows a series of steps which are performed as part of development phase S30 of the methodology of Figure 1.
[0040] The studies conducted in the preliminary analysis phase S10 and the laboratory analysis phase S20 are used, in embodiments of the invention, to estimate the ideal position, depth, distance from the shore, and shape of the natural barrier to be established, along with its corresponding dimensions (width, length, height, and inclination). The setting of the natural barrier S40 is thus achieved through a combination of fieldwork and laboratory analysis, including modelling of wave kinetics and the way in which they would be affected by the presence of a physical structure at or near the coastline location of interest, and takes its inputs from the environmental characteristics 12 and physical characteristics 14 output from stage S10 of Figure 2.
[0041] In embodiments of the present invention, the setting of the natural barrier S40 can be performed using a machine-learning process, based on a joint optimisation model trained using data from previous similar constructions, whether artificially triggered natural barriers produced by prior iterations of embodiments of the present invention, or fully artificial barriers. Typically, the natural barrier will have a shape which correlates, at least weakly but often strongly, with the shape of the coastline.
[0042] The cementation nature of the artificially-triggered natural barrier, in its estimated configuration, is also anticipated as part of the establishment of the natural barrier S40. This involves the use of three-dimensional models of the barrier slab, allowing morphological analysis and visualization of results before scaling up natural barrier production in situ. This also enables the relationship between measurements obtained in the preliminary analysis phase, and their effect on ideal barrier location and configuration, to be refined; visualization is particularly useful in embodiments in which a machine learning model is either not used, or is limited in its scope, with empirical calculations being performed instead.
[0043] This setting of the natural barrier S40 may, in some configurations, be considered as a step occurring prior to the in situ development S30 itself. Embodiments of the present invention may thus be characterised as receiving input from a setting phase S40, and commencing with a physical construction phase 550, rather than including the setting phase S40 itself.
[0044] The physical construction phase S50 of the submerged setting of the natural barrier begins, in embodiments of the present invention, with the excavation S52 of a trench at an offshore location corresponding substantially, or as close as reasonably possible in view of any physical access limitations and without disturbing the existing underwater flora (e.g. Posidonia fields), to the ideal location derived from the modelling process. The trench is excavated at a specific depth, using any machinery appropriate for relocating of the seabed's sediment while temporary walls and sand barriers are installed at the sidewalls of the trench, forming a cofferdam. The excavated sand from the seabed, along with additional sand from the deeper seabed, are stored for later re-use. Typically, the trench is dug at a depth in the region of 4-6 metres, but the specific depth will depend on the slope of the seabed and the required distance from the shore for the natural barrier setting.
[0045] A physical representation of step S52 is illustrated in Figures 3(a) and 3(b), which shows the establishment of a cofferdam 90 in an area of coastline represented by the sea 91 and its seabed 92 sloping away from the shore 93. In Figure 3(a), a trench position is defined using temporary sidewalls 94 which are dug into the sea bed at the required location, and which may be reinforced or replaced with cofferdam walls once sand is excavated from the trench as shown in Figure 3(b).
[0046] Geotextile materials are added to the excavated trench in step S54. The geotextiles may, in some embodiments of the present invention, be provided in sheet form, which can be folded in a tube-like or case-like configuration, substantially conforming to the interior of the extracted trench. The geotextiles thus form a 'shell' structure, the interior of which is then filled with the stored sand. The geotextiles allow for the stabilization of the sand in a specific geometry, conforming to the natural barrier structure, while pores in the geotextiles allow the circulation of water molecules into the sand. In some embodiments, geofibres are used instead of, or in addition to, geotextiles. After setting the barrier structure in this manner, the temporary cofferdam walls and sand barriers are removed. The setting of the natural barrier is thus established.
[0047] The setting of the natural barrier structure is illustrated in Figure 3(c) and Figure 3(d), via the addition of geotextile materials 95 to cofferdam 90.
[0048] According to embodiments of the present invention, a pipe network, based on the principles of an irrigation system, is distributed through the volume of the natural barrier structure in installation step S56. The pipe network is to transport a bacterial suspension as step 562 of bacterial treatment phase S60, into the geotextiles, to increase the number of the specific ureolytic bacteria, of the type pre-existing at the location of the natural barrier, identified from the preliminary analysis. Bacteria injected into the natural barrier structure are larger than the pores in the geotextiles, and are therefore trapped within the shell.
[0049] The pipe network transports the bacterial suspension from a source such as a tank, which is either arranged on-shore or is positioned on an offshore floating structure close to the natural barrier site, such as a buoy. Natural-based MICP solidification solution, including natural sea water material such as CaCI, urea and organic matter, as well as artificial sea water, is also supplied in step S64, which occurs in parallel with step 62, through the pipe network, considering the natural composition of the seawater, in order to provide Ca2+ and organic content to initiate the MICP reaction, in a manner dependent on results from the preliminary analysis. Bacteria and solidification solution may, in some embodiments, be distributed through the pipe network in phase S60 at specific time intervals, and in specific quantities at particular times, according to a supply regime determined from the modelling phase S20 and the MICP definition 24. The source may have an automated delivery system, accessible via a control device or application (for example, software executed by an on-shore control system) which is controlled in accordance with the supply regime, for example by control of the state of a tap and/or control of an injection pump.
[0050] Any suitable pipe network may be employed. For example, in some embodiments, one or more 'trunk' pipes are distributed along the upper surface of the natural barrier, and a plurality of 'branch' pipes extend downwardly from the trunk through and towards the bottom of the natural barrier structure.
[0051] The supply of the bacterial suspension and solidification trigger a biochemical cementation process.
[0052] Figure 3(d) illustrates a representation of the natural barrier setting, with the installed pipe network 96. In the illustrated embodiment, the pipe network is supplied from a floating source 97. The geotextile shell 95 is not shown in Figure 3(d) - the interior of the shell is represented by a cemented natural barrier 98.
[0053] In structure-modelling phase S70, the structure is monitored using submarine geophysical and/or geotechnical techniques 572 to determine its solidification progress. At the same time, liquid samples are retrieved S74 through the pipe network and diverted into a monitoring device in order to measure the Ca2+ and pH of the liquid and estimate the progress of the ureolysis procedure. The monitoring device may be co-located with the source of the bacterial suspension, may be positioned elsewhere, or may be detachable from the pipe network via one or more valves, and attached only when monitoring is required to take place. The results from the monitoring device are provided to the control system. Adjustments are made to the rate or content of the supply of the bacterial suspension and/or solidification solution, if these are required.
[0054] A further advantage of the use of the natural barrier is that carbon dioxide diluted in the sea water, can bind within the cement of the natural barrier structure. This promotes growth of plant life on the natural barrier structure, while avoiding the wider release of CO2 through water and in the air where it may be harmful to organisms, for example, fish, and in general to the ecosystem.
[0055] When the artificially-triggered naturally developed barrier is formed to the required specification, the bacterial treatment may be terminated, in embodiments of the present invention, to prevent excessive natural barrier development and any negative impact on the coastal environment. The geotextile materials and pipe network are removed to provide the natural barrier with a natural appearance.
[0056] To verify completion of the natural barrier in a finalization and verification phase S80, one or more samples are taken in step S82 from various parts of the natural barrier structure to be analysed for their physical properties by determining the UCS, studying their physical structure and calculating their porosity using X-ray computerised tomography (CT) scanning. Further analysis may be conducted in phase S80 in embodiments of the present invention using methods such as (a) total organic carbon analysis to measure the amount of organic carbon after inorganic carbon has been removed, (b) Fourier-transform infrared spectroscopy (FT-IR) for better material content interpretation and (c) use of a thermogravimetry analyser (TGA) for determining composition of lignocellulosic biomass in wet chemical methods. The samples are analysed for their mineralogical compositions as well as for their geochemical characteristics using optical polarized microscopy, SEM-EDS and XRD.
[0057] The results from the aforementioned analysis are combined in step S82 order to evaluate the level of solidification. Every sample is evaluated in relation to slab thickness and surface solidification, microscopic-level cementation, solidification time, and water and air temperature. When the measurements correspond to a predetermined threshold of cementation, it is determined that the natural barrier is complete.
[0058] The structure-modelling phase S70 and the finalization and verification phase S80 may, in some configurations, be performed outside of methods according to embodiments of the present invention, as subsequent stages, with the embodiments instead concluding with bacterial treatment phase S60. This may be appropriate in circumstances in which the behaviour of the natural barrier development is assumed to follow its modelled behaviour closely, for example where a natural barrier is close to an already-developed natural barrier in a similar environment, such that the requirements on modelling and verification can be relaxed.
[0059] The development of an artificially-triggered, naturally-developed natural barrier on the sea bed of the coastal zone is an innovative, sustainable, natural-based soft engineering solution to mitigate coastal erosion. The construction of the natural barrier involves engineering methods and limited materials that are harmless to the environment. In embodiments of the present invention, geotextiles, sand barriers and temporary walls are in position underwater for two months.
[0060] The resultant natural barrier acts as a submerged breakwater, as it attenuates the kinetic energy of the waves. It has properties similar to natural beachrocks, and can reduce coastal erosion, while also providing a natural rocky habitat that contributes positively to marine biodiversity.
[0061] Figure 3(e) illustrates a representation such attenuation of kinetic wave energy by a natural barrier 98 developed using the methodology of embodiments of the present invention. The structure of the cofferdam 90 shown in Figures 3(b)-3(d) is removed, as are the geotextile shell 95 and the pipe network 96. Kinetic energy of waves moving in the direction of the left-to-right arrow 99 towards the shore 93 is represented in relation to a first group 100 of unattenuated large waves at the surface of the sea 91. A subsequent group 101 of smaller sea waves are shown above the natural barrier 98, where the natural barrier 98 has attenuated kinetic energy of the first group 100 of waves. In this manner, the use of the natural barrier 98 to protect the coastline from erosion can be envisaged.
[0062] It will be appreciated that specific process details or aspects of the structure or composition of the natural barrier may vary depending on the location and environmental conditions of the target area, as well as the specific bacteria used for the carbonate precipitation process. As such, embodiments of the present invention are not restricted to use of any specific materials, bacterial triggers, or natural barrier settings.
1. A method of establishing a natural coastal protection structure for protecting a coastline
from erosion, comprising:
excavating an offshore trench in the seabed at a predetermined location, the trench having a predetermined shape and depth;
storing sand removed from the seabed by the excavation of the trench;
positioning a geotextile shell within the excavated trench, and adding the stored sand to the interior of the geotextile shell to form a sand structure; and
supplying a bacterial suspension to the sand structure to initialise biochemical cementation of the sand structure to form the coastal protection structure having substantially the predetermined shape.
2. The method according to claim 1, wherein the predetermined location and predetermined
shape are identified based on geomorphological, hydrodynamic and morphodynamic analysis
of the coastline environment.
3. The method according to claim 2, comprising three-dimensional modelling of the effect
on wave motion of a structure having the predetermined shape, and positioned at the
predetermined location of the coastline, to verify suitability of the structure for
protecting the coastline from erosion.
4. The method according to claim 2 or claim 3, comprising selecting the bacterial suspension
for supply to the sand structure, and organic solidification solution, based on analysis
of the bacteria content of sand and water samples at or near the predetermined location
to determine the bacteria most active in causing microbiologically-induced calcite
precipitation in the sand samples.
5. The method according to claim 4, comprising determining a regime for supply of the
bacterial suspension to the sand structure, the supply regime including a rate of
supply and a quantity of supply of the bacterial suspension.
6. The method according to claim 5, comprising installing a pipe network for supplying
the selected bacterial suspension to the sand structure from a storage means, according
to the determined supply regime.
7. The method according to claim 6, comprising removing the geotextile shell and the
pipe network after the sand structure has formed the coastal protection structure.
8. The method according to claim 7, comprising determining that the sand structure has
formed the coastal protection structure by estimating the progress of cementation
of the sand structure by submarine geophysical monitoring, and measuring Ca2+ content and pH levels of liquid samples obtained through the pipe network and extracted
at a monitoring device, and comparing the estimated cementation progress with a respective
threshold.
9. The method according to claim 8, comprising verifying that the sand structure has
formed the coastal protection structure by obtaining one or more samples of the sand
structure and determining their level of cementation, by analysing one or more of
a uniaxial unconfined compressive strength analysis, porosity, organic carbon content,
mineralogy, geochemical characteristics, and lignocellulosic biomass composition.
10. The method according to claim 8 or claim 9, wherein the cementation of the sand structure
is compared with composition of naturally-occurring material at the coastline, and
it is determined that the sand structure has formed the coastal protection structure
when the cemented sand structure has a composition which is substantially the same
as naturally-occurring material.
11. The method according to any one of the preceding claims comprising terminating supply
of the bacterial suspension when the sand structure has formed a coastal protection
structure.
12. The method of any one of the preceding claims, wherein the geotextile shell comprises
a porous geotextile material, having a porosity at which the supplied bacterial suspension
is contained within the shell.
13. The method according to any one of the preceding claims, wherein the coastal protection
structure is a cemented sand natural barrier for attenuating kinetic wave energy.
14. A natural coastal protection structure produced according to the method of any one
of the preceding claims.