ISO 21650:2007

INTERNATIONAL ISO
STANDARD 21650
First edition
2007-10-15
Actions from waves and currents on
coastal structures
Effets des vagues et des courants sur les structures côtières

Reference number
©
ISO 2007
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ii © ISO 2007 – All rights reserved

Contents Page
Foreword. iv
Introduction . v
1 Scope . 1
2 Terms and definitions. 2
3 Symbols . 9
4 Basic variables for actions from waves and currents . 9
4.1 Water levels . 9
4.2 Waves. 10
4.3 Currents . 13
5 Wave and current action on structures. 13
5.1 Wave action on mound breakwaters .13
5.2 Wave action on vertical and composite breakwaters . 16
5.3 Wave actions on coastal dykes and seawalls . 17
5.4 Wave and current action on cylindrical members and isolated cylindrical structures. 20
5.5 Wave interaction with floating breakwaters. 21
5.6 Wave action on wave screens . 22
6 Probabilistic analysis of performance of structures exposed to action from waves and
currents. 23
6.1 Examination of uncertainties related to wave and current action. 23
6.2 Reliability assessment of structures . 24
Annex A (informative) Water levels . 25
Annex B (informative) Wave action parameters. 27
Annex C (informative) Currents . 41
Annex D (informative) Wave action on rubble mound structures. 43
Annex E (informative) Wave actions on vertical and composite breakwaters. 63
Annex F (informative) Wave action on coastal dykes and seawalls . 68
Annex G (informative) Wave and current actions on cylindrical members and isolated structures. 76
Annex H (informative) Wave interaction with floating breakwaters. 93
Annex I (informative) Wave action on wave screens. 97
Annex J (informative) Probabilistic analysis of performance of structures exposed to action from
waves and currents . 102
Bibliography . 112

Foreword
ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies
(ISO member bodies). The work of preparing International Standards is normally carried out through ISO
technical committees. Each member body interested in a subject for which a technical committee has been
established has the right to be represented on that committee. International organizations, governmental and
non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the
International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of technical committees is to prepare International Standards. Draft International Standards
adopted by the technical committees are circulated to the member bodies for voting. Publication as an
International Standard requires approval by at least 75 % of the member bodies casting a vote.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. ISO shall not be held responsible for identifying any or all such patent rights.
ISO 21650 was prepared by Technical Committee ISO/TC 98, Bases for design of structures, Subcommittee
SC 3, Loads, forces and other actions.
iv © ISO 2007 – All rights reserved

Introduction
This International Standard, which deals with the actions from waves and currents on structures in the coastal
zone and in estuaries, is the first of its kind. Waves and currents and actions from waves and currents on
structures in deeper water, especially structures for the petroleum industry, are dealt with in ISO 19901-1 and
ISO 19902, ISO 19903 and ISO 19904-1. Some of the structural elements for deeper water structures and
coastal structures are the same, especially elements with cylindrical shapes. There will thus be, to some
extent, an overlap between this International Standard and other ISO standards on the wave and current
actions on cylindrical structural elements. There is though, a difference in wave conditions and wave
kinematics between coastal waves and deeper water waves.

INTERNATIONAL STANDARD ISO 21650:2007(E)

Actions from waves and currents on coastal structures
1 Scope
This International Standard describes the principles of determining the wave and current actions on structures
of the following types in the coastal zone and estuaries:
⎯ breakwaters:
⎯ rubble mound breakwaters;
⎯ vertical and composite breakwaters;
⎯ wave screens;
⎯ floating breakwaters;
⎯ coastal dykes;
⎯ seawalls;
⎯ cylindrical structures (jetties, dolphins, lighthouses, pipelines etc.).
For the rubble mound structures it is not possible to determine the forces on and the stability of each individual
armour unit because of the complex flow around and between each armour unit. But there are formulae and
principles to estimate the necessary armour unit mass given the design wave conditions. Coefficients in these
formulae are based on hydraulic model tests. Since the rubble mound structures are heavily used, they are
included in this International Standard, although they may not be treated exactly in accordance with ISO 2394.
This International Standard does not include breakwater layout for harbours, layout of structures to manage
sediment transport, scour and beach stability or the response of flexible dynamic structures, except vortex
induced vibrations.
Design will be performed at different levels of detail:
⎯ concepts;
⎯ feasibility;
⎯ detailed design.
This International Standard is aimed at serving the detailed design.
It is pointed out that the annexes are only informative and are not guidelines/manuals. The annexes have no
regulatory power.
Wave and current conditions vary for different construction sites. It is very important to assess the wave and
current conditions at a given site. Assessment procedures for these conditions and for their uncertainties are
included.
2 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
2.1
actions
force (load) applied to the structure by waves and/or currents
2.2
anchors
units placed on the seabed, such as ship anchors, piles driven into the seabed or concrete blocks, to which
mooring lines are attached to restrain a floating object from excessive movements
2.3
annual maximum method
method of estimating extreme wave heights based on a sample of annual maximum wave heights
2.4
armour layer
protective layer on a breakwater, seawall or other rubble mound structures composed of armour units
2.5
armour unit
relatively large quarry stone or concrete shaped unit that is selected to fit specified geometric characteristics
and density
2.6
astronomical tide
phenomenon of the alternate rising and falling of sea surface solely governed by the astronomical conditions
of the sun and the moon, which is predicted with the tidal constituents determined from harmonic analysis of
tide level readings over a long period
2.7
breakwater
structure protecting a shore area, harbour, anchorage and/or basin from waves
2.8
buoyancy
resultant of upward forces, exerted by the water on a submerged or floating body, equal to the weight of the
water displaced by this body
2.9
chart datum
CD
reference level for soundings in navigation charts
2.10
core
inner portion of a breakwater, dyke and rubble mound structures, often with low permeability
2.11
crest
1. highest point of a coastal structure
2. highest point of a wave profile
2.12
crown wall
concrete superstructure on a rubble mound
2 © ISO 2007 – All rights reserved

2.13
datum level
reference level for survey, design, construction and maintenance of coastal and maritime structures, often set
at a chart datum or national geodetic datum
2.14
deep water
water of such a depth that surface waves are little affected by bottom topography, being larger than about
one-half the wavelength
2.15
design water level
DWL
water level selected for functional design, structural design and stability analysis of marine structures
NOTE Generally it is the water level that mostly affects the safety of the structures/facilities in question. DWL is
chosen in view of the acceptable level of risk of failure/damage.
2.16
density driven currents
currents induced by horizontal gradients of water density generated by changes in the salinity and/or
temperature, which are caused by the influx of fresh water from run-off from land through an estuary, heat flux
from coastal power stations, or other reasons
2.17
diffractions coefficient
ratio of the height of diffracted waves to the height of incident waves
2.18
directional spreading function
function expressing the relative distribution of wave energy in the directional domain
2.19
directional wave spectrum
function expressing the energy density distribution of waves in the frequency and directional domains, being
expressed as the product of frequency wave spectrum and the directional spreading function
2.20
drag coefficient
coefficient used in the Morison equation to determine the drag force
2.21
dyke berms
nearly horizontal area in the seaward and landward dyke slope which are primarily built to provide access for
maintenance and amenity and which reduce wave run-up and overtopping
2.22
dyke toe
part of a dyke that terminates the base of the dyke on its seaward face
NOTE Various toe constructions are used to prevent undermining of the dyke.
2.23
extreme sea state
extreme waves
state of waves occurring a few dozen times a year to once in many years, expressed with the significant wave
height and the mean or significant wave period at the peak of storm event
2.24
filter
intermediate layer, preventing fine materials of an underlayer from being washed through the voids of an
upper layer
2.25
floating breakwater
moored floating o
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