The following chapters of the report cover all stages of the design of a revetment. The report, however, is restricted to flexible revetments. Revetments are generally defined as :
any composition of natural or artificial materials, deliberately placed in a marine environment to protect from degradation any artificial or natural body of erodible material””.
The restriction to flexibility excludes all rigid systems such as monolithic structures and vertical seawalls, but still includes all possible additional flexible protection systems, which may be necessary to compensate for adverse effects associated with rigid structures in the marine environment. The most common examples of the latter are bottom and scour protection systems.
The Working Group has acknowledged the close correlation between hydraulic and geotechnic loadings, thus the need for integrated design procedures for a flexible revetment.
The revetment is intentionally treated as a system with the following constituents as subsystems or elements: a cover layer, one or more sublayers, and a core or base. Various functions may be assigned to sublayers, turning them into filter layers or cushion layers (Chapters 2 and 3).
Further, the fact that most revetments are part of a larger scheme or a coastal defence system may require a design philosophy that fits into a wider project or management policy. Therefore, risk assessment, environmental assessment, construction and future management of structures are typical aspects, besides the mere technical design, that are treated.
The contents of the final report are summarized below.
In Chapter 2, “”Systems and Materials””, an overview is given of the various materials that may be used. Their functions are also treated and it is shown how they can be combined in the revetment system as a whole, in a variety of environmental conditions.
“”Design Philosophy”” is treated in Chapter 3, where it is described how the functions of the revetment can be identified and defined to be used as criteria for the selection of alternatives. New means aimed at rational optimization of the design are provided by probabilistic design methods, which are shortly outlined while reference is given inter alia to PIANC reports (illustration of which is given in Section 5.8). A practical list of elements for quality systems is provided, applying to revetment design.
In Chapter 4, “”Design Conditions””, methods to determine the environmental boundary conditions are treated. “”Hydraulic boundary conditions”” (Section 4.2) concentrate on wave and wave-related parameters and under Section 4.3 the parameters related to the subsoil and other granular materials are addressed. Other boundary conditions having usually a much larger time scale and considerable impact are described under “”Coastal Morphology”” (Section 4.1) and in Section 4.4 dealing with climatic and other conditions.
In Chapter 5, “”Design Procedures””, a variety of design data, considerations and boundary conditions reappear, to be used in specific descriptions of interactions or responses between boundary conditions and the revetment system “”External and Ice Loadings””, Section 5.3.1 and “”Internal Loading”” in Section 5.3.2).
Further, design considerations, boundary conditions and interactions are combined into procedures, which the designer can fit into his specific problem.
Chapter 6 begins (in 6.1) with practical design considerations focusing on specifications, construction aspects, inspection and maintenance, and environmental and climatic conditions. In Section 6.2 “”Economic Considerations”” the basic principles to assess investment and management costs are outlined. The selection of alternatives based on these considerations is elaborated with an example. Section 6.3 basically consists of a “”Designer”s Checklist””.
The report contains a glossary of terms and notation. In the two first appendices, practical examples of the design and performance of existing structures are presented in the form of a case study and an inventory of experiences. The third appendix includes recommendations for future work.”
