The present disclosure generally relates to the stabilization and/or restoration of beaches, and more particularly relates to stabilization and/or restoration of beaches utilizing longshore transport interactions.
Waves, storms, and coastal currents may all result in beach erosion, manifesting in long term losses of sediment and rock, as well as short term redistribution of sediment and rock to other regions of a coastline. Such beach erosion can damage coastal property, for example, by reducing the size of the beach and undermining coastal structures. Such destruction and losses can have a severe negative impact on beach properties. Additionally, the loss of beach terrain may result in the loss of natural habitats for coastal life. The loss of natural habitats can have a deleterious impact on coastal eco-environments.
According to a first implementation, a method of restoring a beach includes positioning a recovery module at a first location in a region of a beach to sea interface. A longitudinal axis of the recovery module is oriented generally perpendicular to a longshore current in the region of the beach to sea interface. The recovery module is removed from the first location upon achieving a desired level of accretion adjacent to the recovery module.
One or more of the following features may be included. Positioning the recovery module in the first location may include positioning the recovery module to be at least partially emergent during at least a portion of a tidal cycle. Positioning the recovery module in the first location may include positioning the recovery module to be at least partially submerged during at least a portion of a tidal cycle. Positioning the recovery module in the first location may include positioning at least about half of the recovery module in the sea.
Positioning the recovery module may include ballasting the recovery module. Ballasting the recovery module may include filling at least a portion of an interior of the recovery module with water. Positioning the recovery module in the first location may include anchoring the recovery module.
The desired level of accretion may provide a reduced longshore current interaction at the recovery module. Removing the recovery module may include at least partially de-ballasting the recovery module. The method may further include positioning the recovery module at a second location in a region of beach to sea interface. The second location may include an updrift location relative to the first location. The second location may include a seaward location relative to the first location.
According to another implementation, a method of beach restoration includes positioning a plurality of recovery modules at a plurality of first locations in a region of a beach to sea interface. A longitudinal axis of each of the plurality of recovery modules is oriented generally perpendicular to a longshore current in the region of the beach to sea interface. At least one of the plurality of recovery modules is moved from at least one of the plurality of first locations to at least a second location.
One or more of the following features may be included. The at least a second location may include an updrift location relative to the plurality of first locations. The at least one of the plurality of recovery modules may include a furthest downdrift recovery module of the plurality of recovery modules. The at least a second location may include a seaward location relative to the at least one of the plurality of first locations.
Moving at least one of the plurality of recovery modules may include moving all of the plurality of recovery modules to a plurality of second locations. The method may further include removing at least a portion of the plurality of recovery modules from the region of the beach to sea interface. Moving at least one of the plurality of recovery modules to at least the second location may include moving the at least one of the plurality of recovery modules upon achieving a desired level of accretion adjacent to the at least one of the plurality of recovery modules.
According to yet another implementation, a method of beach restoration includes positioning a plurality of recovery modules at a plurality of first locations in a region of a beach to sea interface. A longitudinal axis of each the plurality of recovery modules is oriented generally perpendicular to a longshore current in the region of the beach to sea interface. A furthest downdrift recovery module of the plurality of recovery modules is sequentially moved to an updrift location relative to the remaining recovery modules.
The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features will become apparent from the description, the drawings, and the claims.
a-4c schematically depict various embodiments of a recovery module.
Referring
For example, and referring also to
With reference also to
While recovery module 60 (and/or recovery modules 62, 64, 66) may be described herein as being positioned 10 in first location 68 (and/or locations 70, 72, 74 of recovery module 62, 64, 66) that may generally be in a downdrift region of littoral cell 50, this is intended for the purpose of explanation only (e.g., in the context of a specific embodiment of coastal recovery of a larger region of littoral cell 50, to be described in greater detail below), and should not be construed as a limitation. In various additional/alternative embodiments recovery module may be positioned 10 at any desired location within littoral cell 50, e.g., to effectuate localized coastal recovery, and or to effectuate coastal recovery of a larger region of littoral cell 50 in an alternatively sequenced manner. All such implementations are considered to be within the contemplation of this disclosure.
As shown, a longitudinal axis of recovery module 60 may be oriented 12 generally perpendicular to longshore current 58. Consistent with the present disclosure, the presence of the one or more recovery modules at beach to sea interface 56 may generally disrupt the longshore current in the region proximate the one or more recovery modules. The degree or disruption of the longshore current may be, at least in part, based upon the dimension of the recovery module generally perpendicular to the longshore current. As such, a longitudinal axis of recovery module 60 (as well as a longitudinal axis of recovery modules 62, 64, 66) may be oriented 12 generally perpendicular to longshore current 58 to maximize the disruption of longshore current 58 in the region proximate recovery module 60 (as well as the respective regions proximate recovery modules 62, 64, 66). However, it should be appreciated that other orientations of the one or more recovery modules (including an orientation in which the longitudinal axis of the one or more recovery modules is generally parallel to the longshore current) may also be utilized with varying degrees of efficacy (e.g., which may be based upon, at least in part, the degree of resultant disruption of the longshore current).
Positioning 10 the recovery module (e.g., recovery module 60 for the purpose of example, with the following description being equally applicable to one or more of recovery modules 62, 64, 66) in the first location (e.g., location 68 of recovery module 60) may include positioning 16 the recovery module (e.g., recovery module 60) to be at least partially emergent during at least a portion of a tidal cycle. Positioning 16 recovery module 60 to be at least partially emergent during at least a portion of a tidal cycle may include positioning recovery module 60 such that at least a portion recovery module 60 is disposed above the average water level (e.g., the water level at a midpoint between the crest and trough of a wave) during at least a portion of a tidal cycle. In an at least partially emergent position, recovery module 60 may (but is not required to be) completely submerged during at least a portion of a tidal cycle (e.g., during high tide) and/or in above average seas for littoral cell 50.
Positioning 10 the recovery module (e.g., recovery module 60 for the purposed of example) in the first location (e.g., location 68 of recovery module 60) may include positioning 18 recovery module 60 to be at least partially submerged during at least a portion of a tidal cycle. Being positioned 18 to be at least partially submerged during at least a portion of a tidal cycle, at least a portion of recovery module 60 may be disposed below the average water level during at least a portion of a tidal cycle. In an at least partially submerged position, recovery module 60 may (but is not required to be) completely emergent during at least a portion of a tidal cycle (e.g., during low tide) and/or in below average seas for littoral cell 50.
Furthermore, positioning 10 the recovery module (e.g., recovery module 60, for the purpose of example) in the first location (e.g., location 68 of recovery module 60) may include positioning 20 at least about half of recovery module 60 in the sea. In such an arrangement recovery module 60 may be positioned 20 such that the full height of recovery module 60 is submerged for half of the length of recovery module 60 during at least a portion of a tidal cycle. For example, recovery module 60 may be positioned such that the full height of recovery module 60 is below the average water level at a mid-tide condition (e.g., a tide level that is midway between high tide water level and low tide water level) for half of the length of recovery module 60. Accordingly, recovery module 60 may bridge beach to sea interface 56 during at least a portion of a tidal cycle. In such a configuration, the waterline may generally move up and down the length of recovery module 60 during a tidal cycle.
Recovery module 60 (and/or recovery modules 62, 64, 66) may generally include a generally rectangular prismic, or box-like, structure. According to one embodiment, recovery module 60 may have dimensional ratios of one unit height, one and a quarter units width, and four units length. Similarly, in exemplary embodiments recovery module 60 may have a length of between about 20 feet to about 40 feet. However, these dimensions are intended only for the purpose of illustration, and not of limitation. Various additional/alternative dimensions may suitably be utilized. Generally, in beach environments having a steeper gradient (e.g., as may be associated with a high energy beach) a relatively shorter recovery module may be employed. Conversely, in beach environments having a shallower gradient a relatively longer recovery module may be employed. However, such implementations should be understood to be for the purpose of example, and not of limitation, as environmental conditions, design preference, recovery module availability, and the like, may provide for a variety of alternative implementations. The illustrated recovery module is intended for the purpose of example and should not be construed as a limitation. Various additional/alternative geometries (e.g., cylindrical, trapezoidal, etc.), dimensions, and dimension ratios may suitable be utilized depending upon environmental conditions, design criteria, etc.
Consistent with various embodiments, the recovery modules may include hollow structures that may be manufactured from metal (e.g., reinforced or non-reinforced sheet metal), plastic (including fiber reinforced plastics as well as non-reinforced plastics), composite materials, concrete (reinforced as well as non-reinforced) or other suitable materials. In some embodiments, the recovery modules may include generally sealed and/or watertight structures, and/or include generally sealed and/or watertight features. Further, in some embodiments, the generally sealed and/or watertight structures or features may include fluid conduits, such as passages, hoses, vents, etc., that may be selectively opened such that the generally sealed and/or watertight structures or features may be at least partially filled with fluid (such as water or air), for example, by to allow flooding of the generally sealed and/or watertight structures or features. Additionally, in some embodiments, when the at generally sealed and/or watertight structures or features are filled with air, a recovery module may be at least partially buoyant and/or floatable. An at least partially buoyant and/or floatable recovery module may facilitate, for example, sea transport, for example by pushing or towing.
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With particular reference to
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In a related embodiment, depicted in
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Positioning 10 the one or more recovery modules (e.g., recovery modules 60, 62, 64, 66) may include ballasting 22 the one or more recovery modules. As discussed above, the one or more recovery modules may include an at least partially empty compartment. In some embodiments, the at least partially hollow structure of the one or more recovery modules may be, at least initially, emptied during positioning 10. For example, when the at least partially hollow structure of a recovery module is empty, the weight of the recovery module may be decrease, thereby facilitating moving the recovery module. Once the recovery module has been positioned 10 in the desired location, the recovery module may be ballasted 22, for example, which may increase the weight and stability of the recovery module. Accordingly, once the recovery module has been ballasted 22, the recovery module may be less susceptible to undesired movement, e.g., due to the wind or wave. However, it is also appreciated that the strata of the beach and/or sea floor may vary in consistency and stability, which may give rise to settling of the recovery module. Therefore, the degree of ballasting may be determined, at least in part, by the nature of the beach and/or sea floor strata such that undue settling may be reduce and/or eliminated. Undue settling, as used herein, may include settling that may inhibit and/or undesirably increase the difficulty of future repositioning and/or removal of the recovery module; settling that may alter the degree of emergence of the recovery module and undesirably reduce inhibition of longshore drift or otherwise decrease the efficacy of the recovery module; or otherwise give rise to undesirable movement of the recovery module. The degree of ballasting may be varied by the selection of ballasting materials, the amount of ballasting material, the inclusion of low density materials (e.g., foam materials, air bladders, or other low density materials), and the like. In addition, baffling may be used in conjunction with, or exclusive of the aforementioned ballasting materials, to minimize, mitigate or otherwise eliminate undesired settlement of the recovery modules.
In one embodiment, the recovery module may be ballasted 22 by at least partially filling 24 the recovery module with water. The recovery module may be at least partially filled 24 with water by, for example, pumping water into the recovery module, opening one or more seacocks below the water level (e.g., an possibly also one or more air vents above the water level), thereby allowing the recovery module to at least partially flood. In addition/as an alternative to at least partially filling the recovery module with water, other ballasting materials (e.g., sand, rocks, etc.) may be similarly utilized. Further, in addition/as an alternative to ballasting 22 the recovery module, positioning 10 the recovery module in first location 68 may include anchoring 26 the recovery module in place. The recovery module may be anchored 26 using any suitable known anchor, such as a mushroom anchor, earth auger, etc. Similarly, the recovering module may be anchored 26 by spudding. As is known by those having skill in the art, as spud may generally include a vertical post (such as a steel rod, shaft, or tubular member) that may be coupled to the recovery module (e.g., as by being received through a receptacle or opening in the recovery module and/or attached to the recovery module) and may be at least partially driven into the beach and/or sea floor.
As discussed briefly above, the one or more recovery modules (e.g., one or more or recovery modules 60, 62, 64, 66) may be removed 14 from the first location (e.g., respective first location 68, 70, 72, 74) upon achieving a desired level of accretion adjacent to the recovery module. For example, and referring also to
In some embodiments, for example, as shown in
As discussed above, once a desired level of accretion has been achieved adjacent the one or more recovery modules (e.g., recovery modules 60, 62, 64, 66) in the one or more respective first locations (e.g., respective first locations 68, 70, 72, 74), the one or more recovery modules may be removed 14 from the first locations. Any suitable technique, or combination of techniques, may be used for removing 14 the one or more recovery modules. For example, the one or more recovery modules (e.g., recovery modules 60, 62, 64, 66) may be removed 14 utilizing techniques similar to the techniques utilized for positioning recovery module 60, described with reference to
Consistent with the foregoing description, coastal recovery may be accomplished, at least in part, through accretion adjacent to one or more recovery modules in the one or more first locations. Once a desired level of accretion has been achieved, the one or more recovery modules may be removed from the first locations. As such, coastal recovery may be achieved with not residual structures or components remaining behind once the coastal recovery has been achieved. In some implementations, additional coastal recovery, beyond the accretion adjacent to the first locations, may be desired. Referring also to
The second location (e.g., one or more for second locations 92, 94, 96, 98) may include an updrift location relative to the first location. For example, as shown in
Further, while not shown, in one embodiment, a plurality of recovery modules may be migrated in an updrift location utilizing a “leap frog” type technique. For example, as shown in
With reference again to
According to one embodiment, once a desired level of restoration and/or stabilization has been accomplished (e.g., via accretion of sediment adjacent the one or more recovery modules), one or more recovery modules may be positioned for ongoing maintenance and/or stabilization of the littoral cell 50. For example, one or more recovery modules may be positioned 34 in a maintenance location. The maintenance location may include, for example, one or more of the first locations (e.g., first locations 68, 70, 72, 74), one or more of the second locations (e.g., second locations 92, 94, 96, 98), and/or one or more third locations (not shown). As described herein, the one or more recovery modules positioned 34 in the one or more maintenance locations may be oriented generally perpendicular to longshore current 58. Accordingly, the one or more recovery modules positioned 34 in the one or more maintenance locations may prevent/reduce erosion of the previously accreted sediment.
The one or more recovery modules positioned 34 in the one or more maintenance locations may remain in the one or more maintenance locations for a relatively extended period of time. For example, the one or more recovery modules may remain in the one or more maintenance locations for a single season (e.g., during which the longshore current may have a generally constant direction). Additionally/alternatively, the one or more recovery modules may remain in the one or more maintenance locations for one or more years (or any portion thereof). Not withstanding the relatively extended period of time that the one or more recovery modules may remain in the one or more maintenance locations, the one or more recovery modules may continue to be subject to relatively simple and complete removal.
As described above, recovery modules may be formed from a variety of materials. In the case of recovery modules positioned in a maintenance locations, recovery modules may be formed from a material that is capable of withstanding prolonged exposure to water, for example salt water. For example, such recovery modules may be formed from concrete, e.g., which may be capable of withstanding such prolonged exposure to salt water. Additionally/alternatively, recovery modules positioned in maintenance locations may be formed from composite materials, polymeric materials, corrosion protected steel (e.g., including corrosion resistant coatings, and the like).
According to another embodiment, in addition to restoring a coastal region, accreted sediment may be used to form on shore protective barriers. For example, accreted sediment may be moved (e.g., from one or more of accretion zones 84, 86, 88, 90, 100, 102, 104, 106) to create on shore features such as dunes, berms, and/or other permanent, long term, and/or sacrificial barriers to guard against major storms. Such features may protect further inland portions of the coastal region, e.g., in the even of a relatively large storm. Sediment may be moved from one or more of the accretions zones in a generally conventional manner, e.g., slurry pumping; heavy equipment, such as bulldozers, loaders, and the like; as well as any variety of other suitable techniques.
Consistent with any of the above-described movement techniques, positioning 30 at least one of the recovery modules in a second location may include moving all of the plurality of recovery modules to a plurality of second locations (e.g., moving the plurality of recovery modules en masse). Additionally/alternatively, the one or more recovery modules may be moved in a sequential manner, e.g., in which only one recovery module may be moved at a time. Further, while only a single move of the recovery modules is shown (e.g., positioning 10 the one or more recovery modules in a first position and subsequently positioning 30 the one or more recovery modules in a second position), it will be appreciated that effecting a desired level of coastal recovery may include moving the one or more recovery modules to a plurality of updrift locations and/or a plurality of seaward locations within littoral cell 50. Additionally, the method may further include removing 32 at least a portion of the plurality of recovery modules from the region of the beach to sea interface. As discussed above, one aspect of the present disclosure may include a method to effect coastal recovery that does long leave any equipment or waste within the littoral cell once the desired coastal recovery has been accomplished. The one or more recovery modules may be removed utilizing any suitable techniques, including, but not limited to, the techniques shown and described with reference to
A number of implementations have been described. Nevertheless, it will be understood that various modifications may be made. Accordingly, other implementations are within the scope of the following claims.