SUBMERGED GROYNES FOR BEACH STABILISATION

Typically, rubble mound groynes are constructed by end tipping from trucks for which the roadway level must be above high tide. Some adverse effects of such surface piercing groynes include the generation of rips along their trunks (Fleming 1990; Scott et al., 2016), which can transport sand off the beach and out of the groyne compartment. Further, rubble mound groynes have large footprints that may smother benthic habitat. A submerged groyne may obviate such potential adverse impacts. Submerged groynes are used in England to stabilise shingle beaches (Simm et al., 1996). The groyne extends offshore but underwater, protruding far enough above the seabed to arrest alongshore transport of littoral drift. However, scale modelling (Jensen 1997) showed that groynes remaining below the water surface allow for the expansion of rip currents and, hence, a reduction in their velocity and their capacity to transport littoral drift offshore and beyond the groyne compartment. Further, submerged groynes can comprise sheet piling, which may be timber (as used in UK), fibre-reinforced plastic, steel or concrete, which present a negligible footprint, having a minimal impact on benthic habitat.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/UbmLhdXCVj0

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LARGE SCALE IMPACTS OF JETTIES AND TRAINING WALLS - EXPERIENCE ON THE AUSTRALIAN EAST COAST

Coastal Engineering Proceedings ◽

10.9753/icce.v36v.structures.2 ◽

2020 ◽

pp. 2

Author(s):

Angus Gordon ◽

Lex Nielsen

Keyword(s):

Large Scale ◽

East Coast ◽

Flood Mitigation ◽

Rainfall Runoff ◽

Littoral Drift ◽

Adverse Impacts ◽

Long Term Changes ◽

And Training ◽

Eastern Seaboard

Entrance jetties and training walls have instigated fundamental perturbations to coastal and estuary processes at several locations on the Australian eastern seaboard inducing long term changes to foreshore alignments, tidal current velocities, tidal plane elevations and marine ecologies with significant consequences, some having been realised only recently. This paper presents examples of long-term impacts of entrance jetties and training walls on coastal and estuary processes, gleaned from experience on the NSW coast. Jetties constructed at estuary entrances have the potential to alter fundamental coastal and estuary processes inducing changes that evidence indicates may take centuries to resolve. While many beneficial and adverse impacts of jetty construction have been known for many years, such as the improvements to navigation and flood mitigation from rainfall runoff and the interruption to littoral drift transport causing down-drift erosion, some impacts of jetties and training walls have not been well understood.Recorded Presentation from the vICCE (YouTube Link): https://www.youtube.com/watch?v=ARF55RPCPbA&feature=youtu.be

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LONGSHORE CURRENTS IN ONE AND MULTI-BAR PROFILES RELATION TO LITTORAL DRIFT

Coastal Engineering Proceedings ◽

10.9753/icce.v8.15 ◽

2011 ◽

Vol 1 (8) ◽

pp. 15

Author(s):

Per Bruun

Keyword(s):

Wave Breaking ◽

Breaking Waves ◽

Current Theory ◽

Current Approach ◽

Rip Currents ◽

Longshore Current ◽

Littoral Drift ◽

Longshore Currents ◽

Average Water ◽

Sloping Beach

This paper deals with longshore current theories. Introductorily it gives a brief review of wave theories for breaking waves including theoretical, laboratory as well as field results. Next the longshore current theory based on the momentum inflow over a uniformly sloping beach and bottom (Putnam, Munk and Traylor, 1949) is discussed with special reference to its friction factor. The following chapters deal with two new longshore current theories - both based on the continuity principle. One of them called the rip current approach assumes that all water thrown in by wave breaking runs out in rip currents and will probably be valid for profiles with well developed bars and waves approaching the shore almost perpendicularly. The other theory considers the fact that water from a wave breaking under an angle with the bar flows in with a certain phase difference in time longshore and this will create a longshore slope of the average water table, therefore also a longshore current. The water may return to sea uniformly as undertow or in rip currents or by a combination of both. This theory is particularly valid for waves breaking under a certain, not too small, angle with the bar. In both cases the momentum in the breaking waves is ignored because field observations show that in a well developed bar profile most of the momentum has disappeared inside the bar after wave breaking. Examples of computation of current velocities for one bar as well as multi-bar profiles are given. Next the possible relation between longshore currents and littoral drift is discussed.

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Terrestrial laser scanning for geometry extraction and change monitoring of rubble mound breakwaters

ISPRS Annals of Photogrammetry Remote Sensing and Spatial Information Sciences ◽

10.5194/isprsannals-ii-5-289-2014 ◽

2014 ◽

Vol II-5 ◽

pp. 289-295 ◽

Cited By ~ 4

Author(s):

I. Puente ◽

R. Lindenbergh ◽

H. González-Jorge ◽

P. Arias

Keyword(s):

Laser Scanning ◽

Terrestrial Laser Scanning ◽

Point Clouds ◽

Human Populations ◽

Littoral Drift ◽

Storm Waves ◽

Short Period ◽

Rubble Mound ◽

Scan Data ◽

Rubble Mound Breakwaters

Rubble mound breakwaters are coastal defense structures that protect harbors and beaches from the impacts of both littoral drift and storm waves. They occasionally break, leading to catastrophic damage to surrounding human populations and resulting in huge economic and environmental losses. Ensuring their stability is considered to be of vital importance and the major reason for setting up breakwater monitoring systems. Terrestrial laser scanning has been recognized as a monitoring technique of existing infrastructures. Its capability for measuring large amounts of accurate points in a short period of time is also well proven. In this paper we first introduce a method for the automatic extraction of face geometry of concrete cubic blocks, as typically used in breakwaters. Point clouds are segmented based on their orientation and location. Then we compare corresponding cuboids of three co-registered point clouds to estimate their transformation parameters over time. The first method is demonstrated on scan data from the Baiona breakwater (Spain) while the change detection is demonstrated on repeated scan data of concrete bricks, where the changing scenario was simulated. The application of the presented methodology has verified its effectiveness for outlining the 3D breakwater units and analyzing their changes at the millimeter level. Breakwater management activities could benefit from this initial version of the method in order to improve their productivity.

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