The document discusses various coastal stabilization techniques and alternative solutions from an international perspective. It provides examples of different systems used, such as seawalls, breakwaters, groins, beach nourishments, and more recently developed geosystems using bags, tubes and other containers filled with sand or mortar. The conclusion emphasizes that there is no single ideal solution and each coastal problem requires evaluating the advantages and disadvantages of different materials and systems based on the specific conditions and protection needs.

3. Example of coastal erosion: Typhoon Damrey 27Sept’05 Vietnam

4. (Alternative) systems and materials in

7. Systems & Materials Headlands examples

8. Direct & In-direct protection Reduction hydraulic loading

9. Systems & materials: examples Granular materials: from sand to rock Prefabricated systems

10. Identification of coastal problem and Functional Design Starting point Selection technology See also: http://www.unesco.org/csi/pub/source/ero18.htm

12. Problem definition Jan van de Graaff, TUDelft

16. Problem analysis Restored cross section: sand nourishment Cross section after coastal recession Cross section eroded: sand nourishment on dune and/or beach

19. Initial considerations Environmental conditions Functional pre-design alternative Selection of preferred scheme Detailed design In the design process one has to distinguish between functional design and structural design. Functional design concerns the impacts and performance of the coastal alternative with respect to coastal protection, improvement of recreational conditions and conservation of natural living resources. Structural design concerns the resistance of the coastal structure to the actions of waves and currents BASIS PRINCIPLES Design Starting Points www.delos.unibo.it

20. Interference with sediment transport To resolve a structural erosion problem (dS x /dx ≠ 0) with the help of structures (‘hard’ solution), the structures must interfere in the existing sediment transports. If we apply beach nourishments: we must nourish the ‘Loss’ J. Van der Graaff, TUDelft

21. Headlands, groynes and offshore breakwaters

25. Headlands and groynes

26. GROINS . Background and definitions. Groins are the oldest and most common shore-connected, beach stabilization structure. They are probably the most misused and improperly designed of all coastal structures. They are usually perpendicular or nearly at right angles to the shoreline and relatively short when compared to navigation jetties at tidal inlets. As illustrated schematically in Figure , for single and multiple groins (groin field) the shoreline adjusts to the presence of the obstruction in longshore sediment transport. Over the course of some time interval, accretion causes a positive increase in beach width updrift of the groin. Conservation of sand mass therefore produces erosion and a decrease in beach width on the downdrift side of the groin. The planform pattern of shoreline adjustment over 1 year is a good indicator of the direction of the annual net longshore transport of sediment at that location. http://www.ce.ufl.edu/~mcdougal/CEM/Part_V_Coastal_Project_Planning_and_Design/V-3_Shore_Protection_Projects.pdf

27. Groynes (see CEM 2002)

29. Sedimentation polders Netherlands Thailand

30. (CEM 2002)

32. Some remarks on Low-crested Structures (LCS) See also: www.delos.unibo.it [email_address] DELOS

33. Distribution of waves along the center of reef (Ohnaka&Yoshizwa, 1994) Functions and definitions or beach

34. Effectiveness Low-crested structures or beach Wave transmission Geometrical Lay-out; Ls/X Flow pattern But also Sediment transport Waves

35. Functionality of offshore breakwaters in relation with sediment transport J. Van der Graaff, TUDelft

36. DK Close to the coastline UK Holly Beach US Far from the coastline;

37. Ahrens (conceptual) Japan Van der Meer 1991 Narrow–crested breakwaters General transmission characteristics (past) Sawaragi, 1995

38. Example of Aquareef transmission Transmission results for water levels close to the crest

39. Distribution of H 1/3 along the center of reef Reduction of wave height Reduction of wave period Prototype measurements for Yugawara reef, Japan

40. DELOS: transmission www.delos.unibo.it

41. Tombolo: L s /X > 1.0 /(1-K t ) Andrew, 1997 (field data) L s /X >0.65 islands and reefs or X/L s < 1.0 (1-K t ), Salient: L s /X < 1 /(1-K t ) L s /X <1.0 - islands (assume K T = 0 for islands and 0.5 for reefs) L s /X <2.0 - reefs or X/L s > 1 (1-K t ), For salients where there are multiple breakwaters: GX/L s 2 > 0.5(1-K t ) (G= gap width) Where L s is the length of a breakwater and X is the distance to the shore, G is the gap width, and the transmission coefficient K t is defined for annual wave conditions. Transmission coef. in Tombolo-Salient relations (proposed by Pilarczyk as an example) Existing criteria (a choice from many):

42. Comment on functional design Use 2- or 3D numerical models for functional design

43. Burger/Delft 1995 Structural design Stability: Comparison (Delos/Aalborg * is lower limit) Design diagram for start of damage using rock

44. Artificial reefs Reef Balls http://www.artificialreefs.org/ Aquareef Japan

45. Prefabricated Erosion Prevention (P.E.P.) Reefs http://chl.erdc.usace.army.mil/%5CMedia/3/5/2%5Ccoas_19_202_684_722.pdf Prefabricated systems/elements Beachsaver reef Wave block http://chl.erdc.usace.army.mil/CHL.aspx?p=s&a=ARTICLES;349

46. http://chl.erdc.usace.army.mil/%5CMedia/3/5/2%5Ccoas_19_202_684_722.pdf http://chl.erdc.usace.army.mil/CHL.aspx?p=s&a=ARTICLES;349

47. USACE demonstration program http://chl.erdc.usace.army.mil/CHL.aspx?p=s&a=PROGRAMS;3 its objectives are to provide state-of-the-art coastal shoreline protection A variety of shore protection devices and methods are being constructed, administered, and evaluated at a number of sites throughout the United States with diverse shoreline morphologies. These shore protection structures must have scientific support for projected performance and must not affect the aesthetic appeal of the area. Both patented devices and nonproprietary methods are permissible. Example: http://chl.erdc.usace.army.mil/CHL.aspx?p=s&a=PROJECTS;48 http://chl.erdc.usace.army.mil/CHL.aspx?p=s&a=PUBLICATIONS;50 National Shoreline Erosion Control Development and Demonstration Program (Section 227) Cape May Point, New Jersey Section 227 Demonstration Site Cape May Point, NJ - Evaluating a prefabricated submerged breakwater and double-T sill for beach erosion prevention

48. http://chl.erdc.usace.army.mil/CHL.aspx?p=s&a=ARTICLES;349 Cape May Point, New Jersey Section 227 Demonstration Site

50. ALTERNATIVES IN COAST PROTECTION DRIM Retaining Beach Sand by a Distorted Ripple Mat The Distorted Ripple Mat (DRIM) is a low cost shore protection method. It is made of precast concrete with a plastic sheet underlay. The DRIM works by controlling the movement of sand whilst causing little impact on the hydraulic and ecological conditions. Various test have been carried out on the design in order to find the optimum working conditions. The results of the laboratory and field tests are detailed in the paper. The DRIMs were found to work and a set of limiting criteria were identified. In addition the DRIM is able to control bottom currents within specific boundaries, even in unfavourable conditions. The combination of these function’s means that DRIMs can be used not only for beach retention, but in other circumstances as well. For example, reducing shoaling in navigation channels.

51. DISTORTED RIPPLE MAT (Japan) Concept of DRIM mat

52. http:// www.beachdrainage.com / http://www.shoregro.com/ http://www.unesco.org/csi/pub/source/ero11.htm Beach drainage Pressure Equalizer http:// www.ecoshore.com / Gravity drainage Japan

53. Gravity drainage Japan http:// www.pari.go.jp / bsh / ky-skb / hyosa / hpj / english /02menb/ yana / yana.htm

54. Gravel beaches Granular materials are still the most popular materials / systems

55. Geosystems Geomattresses Geobags Geotubes Geocontainers Geocurtains Artificial seaweed Etc.

56. Geosystems have been devised as an alternative to traditional breakwater designs. A high strength synthetic fabric is cast into bags, mattresses, tubes or containers which are then filled with sand or mortar. They are used in the following ways:  Mattresses applied as slope or bed protection;  Bags are suitable for slope protection, retaining walls, toe protection, and in the construction of groynes, perched beaches or offshore breakwaters;  Tubes and Containers are mainly used for the construction of groynes, perched beaches or offshore breakwaters, and bunds in reclamation projects. Geosystems have to date been commonly used as temporary measures due to limitations, including low resistance to waves and currents and low durability to vandalism and UV. The sand-filled variety can now be used as permanent structures and offer a number of advantages over traditional breakwaters, mainly: reduction in cost, quick installation, minimal impact on the environment, low skilled labour, use of local materials and equipment. As with most options it has its advantages and disadvantages, but geosystems have greatly improved since their early beginning. However, further work on improving designs and the need for testing under various conditions is still required.

57. before and after the storm Geomattresses

58. Sandbags Suriname Coronie after first storm Sandbags

59. Geobags

60. Applications Geobags Hannover tests

61. More recent, large scale tests in Hannover, with large geobags, can be found on the website: http://sun1.rrzn.uni-hannover.de/fzk/e5/projects/dune_prot_0.html

62. Geotubes New developments

63. Geotubes and design aspects

64. Failure modes: design aspects & execution

65. Design Geotubes: Shape & strength Palmerton Palmerton

66. Geotubes Pocked beach

67. Failures (US examples) Hole in geotube

68. AmWaj Island, Bahrein at low water Example of project:

69. Transmission characteristics of reefs for AmWaj Island, Bahrein; Delft Hydraulics, 2002 For preliminary design

70. Execution AmWaj Island, Bahrein

71. Leshchinsky’s programma Design and execution with geotubes

72. http:// coastal.tamug.edu / am / StudentPowerpointPresentations /Laura_ Mullaney _ Geotubes _ on _ Galveston _ Island %20ppt/ Geotubes _ on _ Galveston _ Island.ppt http://coastal.tamug.edu/capturedwebsites/cepraconference/glo_coastal_presentations/samplejay/sld001.htm

73. Non-woven Woven Geocontainers

74. Geocontainers

75. Dumping trajectory of geocontainer Accuracy of placement still a problem Breakwater Submerged reef, Gold Coast a view

76. Other geosystems Artificial seaweed anchor http:// www.scourcontrol.co.uk/academic.html ; http:// www.scourcontrol.co.uk/index.html

77. Conclusions on Geosystems Remaining questions: - durability - execution - damage and repair - quality control In general it can be said that geosystems as well as all engineering systems and materials have (some) advantages and disadvantages which should be recognized before a choice is made. There is not one ideal system or material. Each material and system has a certain application at certain loading conditions and specific functional requirements for the specific problem and/or structural solution.

78. CONCLUSIONS on selection of protection measures: It is difficult to make the scoring and some of the scores can be discussed, however, the tendency is quite clear. • Dune/cliff stabilisation can provide some coast and slope protection, but at the expense of preservation of the coastal dynamics. • Coast protection by coastline structures can provide coast protection, but most often at the expense of shore degradation and downstream erosion, aesthetics and coastal dynamics. • Mixed solutions can be very attractive providing both coast and shore protection, but most often at the expense of downstream erosion, aesthetics, safety, bathing water quality and coastal dynamics. • Shore protection by nourishment can be attractive, providing some coast protection and good shore protection with even positive downstream effects, but at the expense of aesthetics and coastal dynamics. • Beach drain provides good protection against seasonal beach variations and high groundwater table. • Beach construction provides both coast and shore protection with improvements of aesthetics, safety and bathing water quality. • Management solutions concentrate on re-establishing the coastal dynamics for the benefit of also the downstream shoreline and the general aesthetics but at the expense of coast and slope protection. • Sea defence by a dike protects against flooding, but at the expense of coastal dynamics and biodiversity. Sea defence by artificial dunes or foreland restoration provides only mild protection against flooding, but does preserve/enhance coastal dynamics and bio-diversity.

79. Conclusions There is certainly a future for alternative structures - erosion control - reduction of wave loading The author does not intend to provide the new design rules for alternative structures. However, it is hoped that this information will be of some aid to designers looking for new sources, who are considering these kinds of structure and improving their designs.

80. Research and practical design in the field of Low-crested structures is also the focus of the “Artificial Reefs Program” in New Zealand ( www.asrltd.co.nz ), the International Society for Reef Studies (ISRS) ( www.artificialreefs.org ), and the European Project DELOS (Environmental Design of Low Crested Coastal Defence Structures, 1998-2003) ( http:// www.delos.unibo.it ). Continued research, especially on submerged breakwaters and alternative systems, should further explore improved techniques to predict shore response and methods to optimise functional and structural design.

81. The more intensive monitoring of the existing structures will also help in the verification of new design rules. International cooperation in this field should be further stimulated . These new efforts will bring future designers closer to more efficient application and design of these promising coastal solutions. Continued research, especially on submerged breakwaters and alternative systems, should further explore improved techniques to predict shore response and methods to optimise functional and structural design.

83. Information sources (some websites) http://chl.erdc.usace.army.mil/%5CMedia/3/5/2%5Ccoas_19_202_684_722.pdf http://chl.erdc.usace.army.mil/CHL.aspx?p=s&a=ARTICLES ;349 Prefabricated breakwaters See also: Silvester, R. and Hsu, J.R., 1993, Coastal Stabilization, Prentice Hall Inc., Englewood Cliffs. ALTERNATIVE SHORELINE STABILIZATION DEVICES http:// www.env.duke.edu/psds/docs.htm http://www.coastal.crc.org.au/coast2coast2002/proceedings.html http://www.cne-siar.gov.uk/minch/coastal/coastal1-06.htm#P1407_126482 http:// www.beachdrainage.com / www.ieindia.org/publish/cv/1103/nov03cv3.pdf http://coastal.tamug.edu/capturedwebsites/cepraconference/glo_coastal_presentations/samplejay/sld001.htm http:// www.scourcontrol.co.uk/academic.html ; http:// www.scourcontrol.co.uk/index.html http://www.artificialreefs.org/ www.delos.unibo.it See also References and Websites in the paper

84. Thank you engineered solutions for an innovative world

85. (never) good enough !!??? The knowledge is in continue development/transition; we have to follow these developments

86. Thank you The End

87. The end

89. COASTAL STABILIZATION AND ALTERNATIVE SOLUTIONS including Geosystems IN INTERNATIONAL PERSPECTIVE Krystian Pilarczyk (former) Rijkswaterstaat/Public Works Dpt., Delft, NL HYDROpil Consultancy [email_address]