Part 2: Civil engineering — Section 2.6 Inland waters, coastal and maritime engineering pot

BRITISH STANDARD
BS6100-2.6:
1991
Incorporating
Amendment No. 1
Glossary of
Building and civil
engineering terms —
Part 2: Civil engineering —
Section 2.6 Inland waters, coastal and
maritime engineering
BS6100-2.6:1991
This British Standard, having
been prepared under the
directionof the Basic Data and
Performance Criteria for Civil
Engineering and Building
Structures Standards Policy
Committee, was published
underthe authority of the
Standards Board and comes
intoeffect on
28 June1991
© BSI07-1999
The following BSI references
relate to the work on this
standard:
Committee reference BDB/3
Draft for comment90/11090 DC
ISBN 0 580 19400 0
Committees responsible for this

British Standard
The preparation of this British Standard was entrusted by the Basic Data and
Performance Criteria for Civil Engineering and Building Structures Standards
Policy Committee (BDB/-) to Technical Committee BDB/3, upon which the
following bodies were represented:
Association of Builders’ Hardware Manufacturers
Association of Building Component Manufacturers
Brick Development Association
British Precast Concrete Federation Ltd.
British Standards Society
Building Employers’ Confederation
Building Services Research and Information Association
Chartered Institution of Building Services Engineers
Concrete Society
Contract Flooring Association
Department of the Environment (Building Research Establishment)
Department of the Environment (Property Services Agency)
Federation of Civil Engineering Contractors
Fibre Building Board Organisation (FIDOR)
Gypsum Products Development Association
Incorporated Association of Architects and Surveyors
Institution of Civil Engineers
Institution of Highways and Transportation
Institution of Structural Engineers
Institution of Water and Environmental Management
National Council of Building Material Producers
National Federation of Roofing Contractors
National House-building Council
Royal Institute of British Architects
Stone Federation

Timber Trade Federation
Water Companies Association
Water Services Association of England and Wales
The following bodies were also represented in the drafting of the standard,
through subcommittees and panels:
British Railways Board
Department of Transport
National Rivers Authority
Amendments issued since publication
Amd. No. Date Comments
7254 August 1992 Indicated by a sideline in the margin
BS6100-2.6:1991
© BSI 07-1999
i
Contents
Page
Committees responsible Inside front cover
Foreword iii
260 1 Base terms 1
260 2 Surface water and groundwater 1
260 21 Precipitation 1
260 22 Surface water 2
260 23 Groundwater 3
260 24 Miscellaneous 4
260 3 Watercourses 5
260 31 General 5
260 32 Topography and regime 5
260 33 Legal 6
260 34 Miscellaneous 6
260 4 Canals and locks 7

260 41 Canals 7
260 42 Types of lock 7
260 43 Lock gates 7
260 44 Other lock features 8
260 45 Miscellaneous 8
260 5 Irrigation and land drainage 9
260 51 Types of irrigation and systems 9
260 52 Factors and requirements 10
260 53 Channel delivery 10
260 54 Piped delivery 11
260 55 Land drainage 11
260 56 Miscellaneous 12
260 6 Docks and harbours 12
260 61 Docks 12
260 62 Berths 13
260 63 Fenders 13
260 64 Breakwaters 14
260 65 Miscellaneous 14
260 7 Waves, tides and offshore structures 15
260 71 Waves 15
260 72 Wave action 17
260 73 Currents 17
260 74 Tides 17
260 75 Results of water action 18
260 76 Offshore structures 19
260 77 Miscellaneous 20
260 8 Protective works 20
260 81 General 20
260 82 Wave protection 20
260 83 Erosion prevention 21

260 84 Flood prevention 22
260 9 Miscellaneous 22
260 91 Water quality 22
260 92 Navigation 24
BS6100-2.6:1991
ii
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Page
260 93 Operations 24
260 94 Coast features 25
260 95 Sediment transport 25
Index 26
BS6100-2.6:1991
© BSI 07-1999
iii
Foreword
This Section of Part2 of BS6100 has been prepared under the direction of the
Basic Data and Performance Criteria for Civil Engineering and Building
Structures Standards Policy Committee.
A general introduction to and explanation of this glossary is given in Part0 of
BS6100, which itemizes the Parts, Sections and Subsections into which this
glossary is divided and provides a general alphabetical index of all the terms in
the Sections and Subsections already published. Those using individual Sections
and Subsections of this glossary are urged to consult Part0 when doing so.
The other Sections of this Part are as follows:
2.1 Structural design and elements
2.2 Substructures. Earthworks. Foundations. Tunnels
2.3 Superstructures. Bridges. Large span structures
2.4 Highway and railway engineering
2.5 Hydraulic engineering and construction work

2.7 Public health. Environmental engineering
2.8 Pipelines and ducts
Terms are listed alphabetically in the index and are referred to by numbers which
are found against the terms in the body of the Subsection. They are arranged in
a classified order, each term having an individual number consisting of seven
digits in two parts, the first of three digits, the second of four. The first three
digits represent the number of the Part, Section and Subsection. The fourth digit
represents the group of terms, the fifth digit represents the subgroup of terms,
and the last two digits represent the place within the subgroup.
Alternative terms are given in medium type below the preferred terms with their
status indicated by “deprecated”. These terms are not individually numbered but
are included in the index with a reference to the preferred term. Terms of more
than one word, e.g.“brushwood fender” are written in a direct style, not as
“fender, brushwood”. The inverted term is included in the index with reference to
the direct term.
Italicized words indicate terms that are defined elsewhere in this Subsection.
A British Standard does not purport to include all the necessary provisions of a
contract. Users of British Standards are responsible for their correct application.
Compliance with a British Standard does not of itself confer immunity
from legal obligations.
Summary of pages
This document comprises a front cover, an inside front cover, pagesi toiv,
pages1 to32 and a back cover.
This standard has been updated (see copyright date) and may have had
amendments incorporated. This will be indicated in the amendment table on the
inside front cover.
iv
blank
BS6100-2.6:1991
© BSI 07-1999

1
No. Term Definition
260 1 Base terms
260 1001 precipitation Water derived from atmospheric vapour and deposited on a
surface as mist, rain, hail, sleet and snow or dew.
260 1002 watercourse Route, usually in the form of a natural depression, along
which water flows by gravity.
260 1003 channel Natural or man-made open passage to convey or contain
water.
260 1004 drainage Removal of surplus water.
260 1005 drain Pipeline or similar conduit, usually underground, or channel
that conveys foulwater, waste water, surface water or other
unwanted liquids.
260 1006 discharge Volumetric flow rate.
260 1007 headworks Intake and associated works at the upstream end of a water
engineering scheme.
260 1008 irrigation Artificial distribution of water to land, usually for growing
crops.
260 1009 canal Channel constructed to carry water, usually for navigation
(2), water power or irrigation.
260 1010 lock Enclosure on a river, canal or at the entrance to a non-tidal
dock, with movable watertight gates through which vessels
pass and proceed from one water level to another.
260 1011 bank Strip of land that forms the edge of a river, canal or reservoir.
260 1012 bed Nominally horizontal or slightly sloping portion of a
watercourse or area of ground under a body of water that is
for most or all of the time covered by water.
260 1013 berth Place where a vessel can be moored, usually for loading and
unloading cargo or passengers.
260 1014 dock Basin for shipping.

260 1015 harbour Natural or artificially sheltered area of water where ships
can lie.
260 1016 wave Oscillation of water level propagated along the surface.
260 1017 tide Periodic rising and falling of water that results from the
gravitational attraction of the moon and the sun and other
astronomical bodies acting upon the rotating earth.
260 1018 aqueduct (1) Conduit for conveying water over long distances.
260 1019 well Hole, usually vertical, excavated or drilled into the ground for
the extraction or observation of water, oil or gas.
260 2 Surface water and groundwater
260 21 Precipitation
260 2101 rain Precipitation in the form of liquid water drops that have a
diameter greater than0.5mm.
260 2102 rainfall Amount of precipitation expressed as a depth usually related
to a particular time of aggregation, for example daily rainfall.
260 2103 intensity of rainfall Rate of precipitation expressed as a depth in unit time, for
example, millimetres per hour.
260 2104 isohyet Line on a map joining places with equal rainfall.
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No. Term Definition
260 2105 interception Process by which precipitation is retained by and later
evaporated from a structure or vegetation and is thus
prevented from reaching the ground.
260 22 Surface water
260 2201 run-off Discharge of surface water that results from precipitation.
260 2202 storm run-off Run-off due to rain.
260 2203 snow melt Run-off due to melting snow.
260 2204 frazil ice

slush ice
deprecated
Ice formed, as colloidal crystals, in a watercourse when the
temperature of the entire body of water flowing along it is
reduced to0°C.
260 2205 base flow
dry weather flow
deprecated
That part of the discharge in a watercourse not directly
derived from run-off.
260 2206 peak flow Maximum discharge during a particular flood event or over a
specified period of time or a fluctuating flow.
260 2207 design storm Rainstorm parameters adopted for the design of water
engineering construction works.
260 2208 design flood Flood parameters adopted for the design of water engineering
construction works.
260 2209 spate
freshet
deprecated
Sudden short-lived increase in discharge.
260 2210 catchment area Area of land that drains naturally to a given point on a river.
260 2211 sewage catchment Area of land that drains to a single sewage treatment works
or outfall.
260 2212 subcatchment area Component part of a catchment area.
260 2213 watershed
divide
deprecated
Boundary between catchment areas.
260 2214 spring Natural outflow of water from the ground.
260 2215 lake

mere, loch, lough, linn, tarn
regional
Large inland body of water.
260 2216 pond Small shallow inland body of fresh water.
260 2217 coastal lagoon Shallow body of water close to the sea and usually with a
shallow restricted inlet from the sea.
260 2218 sea Body of salt water that usually forms a delineated part of an
ocean.
260 2219 swallow hole Natural shaft, due to geological features, down which water
can flow into an aquifer or underground watercourse.
260 2220 hydrography Applied science concerned with the study and measurement
of seas, lakes and other waters where volume is more
important than the rate of flow.
260 2221 hydrology Science of the occurrence and movement of water over and
below the surface of the earth from the moment of
precipitation to the moment of entry into the ocean or of
evaporation into the atmosphere.
260 2222 hydrometry Measurement and analysis of the flow of water.
260 2223 hydrograph Relationship, or graph, that shows the variation with time of
the level, discharge or velocity of water in a watercourse or
channel.
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No. Term Definition
260 2224 unit hydrograph Theoretical hydrograph that would result from a storm of
unit intensity of rainfall and unit duration.
260 2225 mass diagram Graph that shows cumulative flow quantities such as the
integration of a time-flow curve.
260 2226 time of concentration Time taken for a droplet of surface water that falls on the

most remote part of a catchment area to flow to a given point
under investigation.
260 2227 flood detention area Area of land to impound water from river flood flow in excess
of the downstream capacity.
260 2228 surface water Water that flows over, or rests on, the surface of buildings,
other structures or the ground.
260 23 Groundwater
260 2301 soil water Water present in soil belt.
260 2302 soil belt Upper soil layer, constantly affected by evaporation and plant
transpiration, that is partially saturated with percolating
water.
260 2303 intermediate water (1) Water present in intermediate belt.
260 2304 intermediate belt Partially saturated soil layer between soil belt and capillary
fringe.
260 2305 capillary water Water held in the capillary fringe.
260 2306 capillary fringe
capillary zone
deprecated
Soil layer above water table in which water is raised by
capillary action.
260 2307 held water
vadose water
deprecated
Pellicular water, gravitational and capillary water suspended
in partially sealed interstices in the aeration zone.
260 2308 aeration zone Zone between ground surface and water table that comprises
the soil belt, intermediate belt and capillary fringe.
260 2309 groundwater
phreatic water
deprecated

Water within saturation zone.
260 2310 saturation zone Zone below water table and above rock flow zone throughout
which all fissures are filled with water under hydrostatic
pressure.
260 2311 free water Groundwater in interconnected interstices in saturation zone,
that extends down to the first impervious barrier and moves
under the influence of gravity in the direction of the slope of
the water table.
260 2312 internal water Water present in rock flow zone.
260 2313 rock flow zone Zone of the earth’s crust into which water cannot permeate
and below the upper limit of which water cannot exist in a
free state since all interstices have been closed by plastic flow
of the rock.
260 2314 hydroscopic water Water, in soil, that is in equilibrium with atmospheric water
vapour pressure and that is essentially water in which
attraction between water molecules can hold against
evaporation.
260 2315 pellicular water
adhesive water
deprecated
Water, retained in soil by attraction between water and soil
molecules and that forms a coating around the particles and
that may move from one particle to another.
260 2316 water table Surface of groundwater in saturated soil or rock.
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No. Term Definition
260 2317 phreatic water Water in the zone below the water table.
260 2318 phreatic surface Surface to which groundwater would rise in an open ended

pipe.
260 2319 phreatic zone Zone below the phreatic surface.
260 2320 recharge Flow of water to groundwater storage from precipitation,
infiltration from surface streams and other sources.
260 2321 aquifer Water-bearing formation of permeable rock, sand or gravel
capable of yielding significant quantities of water.
260 2322 underflow Groundwater movement in an aquifer.
260 2323 specific yield Ratio of the volume of water yielded by unit volume of
permeable rock or soil when drained by gravity under
specified conditions after being saturated to unit volume.
260 2324 specific retention Ratio of the volume of water retained against gravity by unit
volume of rock or soil that has been saturated and allowed to
drain completely to a remote body of mobile water by way of
continuous capillary interstices to unit volume.
260 2325 specific storage Ratio of the volume of water that unit volume of a vertical
column of an aquifer releases from storage as the head within
the column declines unit distance to unit volume.
260 2326 storage coefficient Ratio of the volume of water that a vertical column of an
aquifer of unit cross-sectional area releases from storage as
the head within the column declines unit distance to unit
volume.
260 24 Miscellaneous
260 2401 water cycle Complete natural cycle of water circulation from the
atmosphere to the earth and return to the atmosphere
through various stages or processes such as precipitation,
run-off and evaporation.
260 2402 shallow well Well less than15m deep.
260 2403 deep well Well equal to or more than15m deep.
260 2404 borehole Hole, usually vertical, bored to determine ground conditions,
for extraction of water or measurement of groundwater level.

260 2405 culvert Covered channel or large pipe that forms a watercourse below
ground level, usually under a road or railway.
260 2406 box culvert Culvert of rectangular cross section.
260 2407 safe yield Maximum rate at which water may be extracted from an
aquifer over a period without depleting the supply or causing
a deterioration in quality.
260 2408 rain gauge Instrument that collects and measures precipitation falling
on it.
260 2409 flood routing Determining at successive points along a river the timing and
form of the hydrograph of a flood.
260 2410 infiltration Passage of water through the soil surface into the soil or from
the ground into a conduit.
260 2411 transmissivity Rate of flow of groundwater through a vertical strip of unit
width of an aquifer, the strip extending the full saturated
depth under unit hydraulic gradient at a fixed temperature.
260 2412 leaching Removal of soluble constituents from soil or other material by
percolating liquid.
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No. Term Definition
260 2413 return period Average interval of time between a number of events that
equal or exceed a particular magnitude, calculated from the
probability of recurrence of such events.
260 3 Watercourses
260 31 General
260 3101 river Water flow along a large watercourse.
260 3102 stream
beck, bourne, brook,
burn, gill, rhine, rife, rill,

runnel,spur
regional
Water flow along a small watercourse.
260 3103 estuary
firth, frith, kyle
regional
Mouth of a river connected to the sea where the tide meets
the river current.
260 3104 creek Small inlet on coast or estuary.
260 3105 feeder Stream or conduit that supplies water to a canal, reservoir or
pond.
260 3106 pen Stretch of water between successive weirs or locks in a river.
260 3107 leat Artificial channel that takes water from a natural
watercourse and conveys it at a shallower gradient than the
watercourse for supply or power purposes.
260 3108 cut Excavated channel that forms part of a river or navigation (2)
system.
260 3109 tidal length of river
tidal river
deprecated
Part of a river within the influence of tides.
260 32 Topography and regime
260 3201 headwater (1) Source or upper reach of a stream or river.
260 3202 regime (1) Dynamic equilibrium between accretion and erosion in an
open channel system or a coastal environment where the
balance existing between the two may vary over a time span
from days to tens or even hundreds of years.
260 3203 regime (2) State in which a river or canal has adjusted its slope and
cross section to an equilibrium condition.
260 3204 reach Stretch of water between two features alongside or across a

river or stream.
260 3205 left bank Left side of a watercourse looking downstream.
260 3206 right bank Right side of a watercourse looking downstream.
260 3207 low flow channel
dry weather channel
deprecated
That part of a multistage channel that is designed to carry
base flow.
260 3208 two stage channel Channel in which normal flow is contained in the lower part
of a wider main channel.
260 3209 flood channel (1) Channel that carries excess water during flood conditions.
260 3210 flood channel (2) Channel made in an estuary by the rising tide.
260 3211 ebb channel Channel made in an estuary by the falling tide.
260 3212 navigation channel Channel for navigation (2).
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No. Term Definition
260 3213 flood plain Area of land that borders a river and is partly or wholly
covered with water during floods.
260 3214 washland Low land adjacent to a river or drain used for storage of flood
water.
260 3215 salting
outmarsh, saltmarsh
deprecated
Area of land periodically covered by saline water and that
usually supports vegetation.
260 3216 meander Deviation of a river from a straight course caused by erosion
of outside bends by impinging currents and accretion on
inside bends.

260 3217 bar Silt, sand or shingle deposit at a river mouth, usually across
the channel.
260 33 Legal
260 3301 navigation (1) Part of a river, usually canalized, over which there is a legal
right to navigate.
260 3302 slack-water navigation
still-water navigation
deprecated
Navigation (1) with no current or a very slight current, made
possible in a river by maintaining the water level with weirs.
260 3303 riparian owner Owner of part of the bed or bank of a river.
260 3304 riparian right Legal right of a riparian owner concerning the river.
260 3305 main river Length of river so designated by statute.
260 3306 enmaining Process of adopting a new length of river as main river.
260 34 Miscellaneous
260 3401 flow duration curve Graph that shows the frequency with which the discharge in
a watercourse is equalled or exceeded during a given period.
260 3402 rating curve Graph that shows the relationship between depth and
discharge in a channel or over a weir.
260 3403 training works Structure designed to influence the location, flow, scouring or
silting capacity of a river.
260 3404 cutwater Streamlined end of a bridge pier shaped to deflect water
flowing past the bridge pier with minimum turbulence.
260 3405 retention board Board used as a weir in a small watercourse.
260 3406 tidal sluice Structure to prevent tidal flow from occurring in an upstream
direction whilst allowing flow to occur in the downstream
direction at low water.
260 3407 tidal door Hinged gate in a tidal sluice operated by the flow of water.
260 3408 pointing door One of a pair of mitre gates in a tidal sluice operated by the
flow of water.

260 3409 penning Action of forming a pen.
260 3410 brushing Cutting and removal of weed and bush growth in a
watercourse.
260 3411 barge bed Place where barges can moor and rest on a soft bed at low
water levels near the bank of a river.
260 3412 camp shedding Protection on the bed of tidal water to enable a vessel to rest
safely at low water levels.
260 3413 headwater(2) Water upstream of a structure.
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No. Term Definition
260 4 Canals and locks
260 41 Canals
260 4101 canalization Division of a river into reaches
by the introduction of control
structures such as weirs to enable it to function as a canal.
260 4102 pound Stretch of water between two successive locks on a canal.
260 4103 summit canal Pound at a summit on a canal that requires an artificial
water supply to it.
260 4104 offside Bank of canal without a towpath.
260 4105 winding hole Short section of canal widened to allow barges to be turned.
260 4106 canal lining Impervious lining to a canal to reduce leakage.
260 42 Types of lock
260 4201 entrance lock
guard lock
deprecated
Lock that provides access to a dock or a canal system from
tidal water.
260 4202 double lock Arrangement of two parallel adjacent lock chambers in a

canal, sometimes interconnected to reduce lockage.
260 4203 flight of locks
staircase
deprecated
Series of connected locks in which each lock chamber is
followed immediately by another, the head gate
of each lower
lock forming a tail gate for the lock above it.
260 43 Lock gates
260 4301 lock gate Gate to separate water in a lock from that outside it or to
divide the lock chamber into two compartments.
260 4302 head gate Upstream gate of a lock or conduit.
260 4303 tail gate Downstream gate of a lock or conduit.
260 4304 sector gate One of a pair of lock gates
that consists in plan of a quadrant
of a circle that rotates about its centre, and that can
withstand water pressure from either side.
260 4305 mitre gate One of a pair of lock gates that, when closed, meet at an
obtuse angle so that the upstream water pressure assists in
sealing the gate contact faces.
260 4306 lift gate Lock gate that opens by rising vertically.
260 4307 lock paddle
wicket
deprecated
Sluice gate to enable a lock to be filled or emptied.
260 4308 gate paddle Lock paddle installed in a lock gate.
260 4309 heel post Vertical member of lock gate, nearest to the lock wall, that
fits into a hollow quoin.
260 4310 mitre post Vertical member of a mitre gate furthest from the lock wall.
260 4311 spear post Post attached near the mitre post of a large lock gate

with a
wheel at the bottom running on a curved track on the gate
platform.
260 4312 balance beam
balance bar
deprecated
Horizontal member that extends from the top edge of a
lock
gate used to lever open the gate when water levels are
balanced.
260 4313 anchor and collar Top hinge for lock gate
that comprises a plate, with a hole to
accommodate the pintle, that is anchored into the lock side.
260 4314 collar strap and anchor Top hinge for lock gate that comprises a strap, around the
heel post, that is anchored into the lock side.
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No. Term Definition
260 4315 gate platform Floor of gate chamber.
260 4316 lock sill
clap sill
deprecated
Raised part of the floor of a lock against which the lock gates
bear when shut.
260 4317 mitre sill Lock sill for a mitre gate.
260 4318 gate recess Recess provided in a side wall of a gate chamber to receive a
lock gate when it is open.
260 4319 gate cylinder
gate ram

deprecated
Hydraulic cylinder used to open and close a lock gate.
260 4320 cylinder pit
ram pit
deprecated
Pit, at the side of a lock, that contains a gate cylinder.
260 4321 capstan pit Pit, at the side of a lock, that contains a capstan operating an
underwater chain to open or close a lock gate.
NOTETwo capstan pits are required per lock gate.
260 4322 chain culvert Underwater passage that connects a lock and capstan pit and
contains a chain to open or close a lock gate.
260 4323 hollow quoin Vertical groove in corner of a gate recess within which the
gate rotates.
260 4324 paddle hole Orifice, the flow through which is controlled by a lock paddle.
260 4325 paddle frame
sluice frame
deprecated
Guide for lock paddle.
260 4326 ground paddle Lock paddle installed in a culvert that bypasses the lock
gates.
260 4327 pintle Vertical pin mounting for a lock gate.
260 4328 pintle pot Recessed bearing to receive a pintle.
260 44 Other lock features
260 4401 lock chamber
lock bay, coffer
deprecated
Space enclosed between the gate chambers of a lock.
260 4402 gate chamber Part of a lock within which a lock gate or pair of lock gates
operates.
260 4403 head bay That part of a lock upstream of the gate chamber of the head

gate.
260 4404 tail bay That part of a lock downstream of the gate chamber of the tail
gate.
260 4405 lift (1) Vertical distance that a vessel is raised or lowered when
passing through a lock.
260 4406 lockage Volume of water transferred from the upper to the lower level
of a canal or river when lowering the water in a lock.
260 45 Miscellaneous
260 4501 side pond Storage pond, at an appropriate level, connected to a lock
chamber to reduce lockage.
260 4502 cope Top edge of a dock wall or similar structure.
260 4503 step Place a lock gate in position on its pintle.
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No. Term Definition
260 4504 racking Process of sealing joints between stop logs by introducing fine
suspended material into the water immediately upstream.
260 4505 lock ladder Ladder in lock chamber for the use of boat crews.
260 4506 mooring ring Ring on a bank or on lock side to which craft are moored.
260 4507 roving bridge Bridge over canal to enable a horse to change from one side of
the canal to the other without being released from the tow
rope.
260 4508 flexible dam Dam that consists of a flexible membrane, supported by
frames at close centres, held down to the bed by water
pressure.
260 4509 clough Sluice gate formed of planks.
260 4510 sanitary station Facility into which canal boat chemical toilets are emptied.
260 4511 blockage factor Proportion of water cross section of a navigational canal
obstructed by the hull of a vessel in motion.

260 4512 squat Phenomenon whereby a moving vessel rises at the bow and
goes down at the stern.
260 4513 aqueduct (2) Bridge that carries a conduit.
260 5 Irrigation and land drainage
260 51 Types of irrigation and systems
260 5101 continuous flow
irrigation
Method of delivery of irrigation water by which each irrigator
receives his allotted quantity of water at a continuous rate.
260 5102 supplemental irrigation Irrigation practice whereby water is supplied for
comparatively short and usually irregular periods of drought
during the crop growing season so as to overcome the
shortage of soil moisture.
260 5103 pumped irrigation Irrigation in which water is delivered by pumping through
pipes.
260 5104 gravity irrigation Irrigation in which the flow of water is maintained by gravity
alone.
260 5105 lift irrigation Gravity irrigation in which water is lifted by a pump or other
device.
260 5106 surface irrigation Irrigation in which water is directed across the land surface.
260 5107 flood irrigation Irrigation in which water is made to cover the surface of the
land to such a depth as to cause saturation for a considerable
time.
260 5108 border irrigation Flood irrigation in which land is divided into strips and water
is delivered into each strip from an irrigation canal.
260 5109 check irrigation Flood irrigation in which fields are divided into rectangles by
low bunds.
260 5110 basin irrigation Surface irrigation of orchards by which each area or group of
trees is surrounded by a bund.
260 5111 spate irrigation Surface irrigation for which earth diversion embankments

are built across normally dry watercourses to divert spate
water into canals leading to bunded fields where the water is
ponded until absorbed.
260 5112 furrow irrigation Surface irrigation in which water is run in furrows between
crops.
260 5113 sprinkler irrigation Irrigation in which water is conducted in pipes to sprinklers
that distribute water like rain.
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No. Term Definition
260 5114 sub-irrigation Irrigation in which water is applied below the ground
surface.
260 52 Factors and requirements
260 5201 gross irrigable area Gross area to be irrigated less such areas as are excluded
from a project by reason of their being unsuitable for
irrigation, either on account of the nature of the soil, or
because the ground is too high to be irrigated by gravity flow
or economically by pumps or other water lifting devices.
260 5202 duty
duty of water
deprecated
Relation between area irrigated, or to be irrigated, and
quantity of water used, or required, to irrigate it for the
purpose of maturing its crop, expressed as a depth.
260 5203 command Height of water level in an irrigation canal at an outlet or
turnout site above the general level of the land in the area to
be irrigated from that outlet.
260 5204 field command Difference in water level, in an irrigation canal, and the level
of the highest point of parcel of land irrigated.

260 5205 farm losses Losses of water on a farm due to uneven distribution, poor
handling, and percolation into the subsoil due to excessive
irrigation.
260 5206 irrigation efficiency Ratio of irrigation water consumed by crops of an irrigated
farm, field or project to water diverted from the source of
supply.
260 5207 water requirement Quantity of water from all sources required for crop
production.
260 5208 irrigation requirement Quantity of water, exclusive of precipitation, required for crop
production using irrigation.
260 5209 consumptive use Quantity of water that arises from evapo-transpiration from
irrigated areas.
260 5210 evapo-transpiration Evaporation of water from soils and transpiration of water
from plants.
260 53 Channel delivery
260 5301 irrigation canal Canal used for irrigation.
260 5302 main canal Irrigation canal that takes water from a headworks and
delivers it to subsidiary irrigation canals.
260 5303 primary canal
lateral canal, branch canal
deprecated
Irrigation canal that takes water from a main canal to feed
lesser irrigation canals.
260 5304 secondary canal Irrigation canal that takes water from a primary canal for
distribution.
260 5305 tertiary canal
minor canal, distributory
canal
deprecated
Irrigation canal that takes water from a secondary canal for

distribution.
260 5306 quaternary canal
sub-minor canal
deprecated
Irrigation canal that takes water from a tertiary canal for
final distribution.
260 5307 check Structure to control the water level in an irrigation canal.
BS6100-2.6:1991
© BSI 07-1999
11
No. Term Definition
260 54 Piped delivery
260 5401 main line Pipe in sprinkler irrigation that conveys water under
pressure from a source of supply to feed subsidiary pipes or
sprinkler laterals.
260 5402 lateral Subsidiary conduit that branches off a larger conduit.
260 5403 sprinkler lateral Pipe that feeds sprinklers.
260 55 Land drainage
260 5501 land drainage System of conduits, structures and embankments required to
control water levels and to protect urban and agricultural
land from flooding, either by fresh or salt water, or to
alleviate such flooding.
260 5502 land reclamation Exclusion of the sea, or other mass of water, from areas that
were previously submerged, or subject to inundation, often by
the raising of land levels.
260 5503 field drainage
subsoil drainage,
landdrainage
deprecated
System of drains to control the water table in a field or series

of fields.
260 5504 drainage system System of drains and ancillary works that conveys their
contents to a cesspool, sewerage system, outfall or other place
of disposal.
260 5505 drainage area
drainage basin
deprecated
Defined area served by a drainage system.
260 5506 land drain
field drain,
agricultural drain
deprecated
Drain used in agriculture to lower the water table.
260 5507 drain tile Small diameter short earthenware pipe with plain ends.
260 5508 tile drain Length of drain tiles laid with open joints to form a land
drain.
260 5509 filter drain
french drain,
rubble drain
deprecated
Drain formed by excavating a trench and backfilling it with
granular material within which may be laid a porous or
perforated pipe.
260 5510 mole drain Small circular lined or unlined land drain formed in cohesive
soil by a mole plough.
260 5511 mole plough Vertical knife blade with a horizontal bullet shape at its
lower end, that is pulled through the ground to form a
continuous hole for cables, pipes or drainage.
260 5512 box drain Small square or rectangular drain.
260 5513 delph ditch Ditch, landward of sea defence works, in which overtopping or

seepage of sea water is collected.
260 5514 soak ditch Ditch at toe of an embankment or raised river bank to collect
seepage water and lower the water table in the embankment.
260 5515 counter drain Drain constructed along the toe of a dam or embankment to
collect and remove seepage and so stabilize the embankment.
260 5516 ditch Trench for surface water drainage.
BS6100-2.6:1991
12
© BSI 07-1999
No. Term Definition
260 5517 wet fence Water-filled ditch used primarily to confine animals.
260 5518 catchwater (1) Small channel cut into the ground on the uphill side of an
excavation to lead run-off clear of it.
260 5519 catchwater (2) Conduit to intercept water from an adjacent catchment area
and divert it into an impounding reservoir.
260 5520 arterial drain Large watercourse, usually artificial, in a drainage system,
that takes water from subsidiary watercourses.
260 5521 level Land drainage district, drainage area or lowland area in
river valley or fen capable of being managed as one unit.
260 5522 fen Low land that is below high water level or needs special
drainage and is seasonally subject to controlled water levels.
260 5523 marsh Low-lying flat land, formed by natural accretion, that is
either wet and soft or needs land drainage for agricultural
use.
260 5524 wastage Lowering of land surface level that results from the draining
of peat soils.
260 5525 inning Land reclaimed from sea or marsh.
260 5526 tide locked Situation where the outflow from a pipe or channel is
prevented by the level of the tide.
260 5527 lift (2) Height through which liquid is raised.

260 56 Miscellaneous
260 5601 rill way Channel in foreshore that carries flow from an outfall.
260 5602 cascade Series of vertical steps in the invert of a drain, sewer or
channel to prevent excessive velocity.
260 5603 open channel flow Water flow, with a free surface, through a conduit.
260 5604 wetted perimeter Length of contact at a cross section between a conduit and the
liquid flowing in it.
260 6 Docks and harbours
260 61 Docks
260 6101 wet dock Dock in which water is retained at a level by gates.
260 6102 dry dock
graving dock
deprecated
Dock with gates from which water may be pumped out
leaving it dry to enable a vessel to be built or repaired.
260 6103 tidal dock Dock without gates.
260 6104 docking block One of a number of blocks to support the underside of the hull
of a ship in a dry dock.
260 6105 altar Step in wall of dry dock, used for holding the feet of the
shores that steady a vessel when the dry dock is empty.
260 6106 ship caisson Sinkable floating box that is used to close the entrance to a
lock, dry dock or wet dock by sinking in position with water
ballast.
260 6107 sliding caisson Partially buoyant ship caisson, moved on rollers from a
housing chamber.
BS6100-2.6:1991
© BSI 07-1999
13
No. Term Definition
260 6108 limpet dam

limpet, leech
deprecated
Transportable open-topped working chamber with one side
open, shaped to fit a dock wall, that seals against the wall as
water is pumped from the enclosed space to provide a dry
working area.
260 6109 dockyard Naval establishment with docks, building slipways, stores
and associated facilities.
260 6110 port Group of berths or docks, or the town or city in which they are
situated.
260 62 Berths
260 6201 quay Platform structure, usually backing onto land, provided
alongside a berth.
260 6202 wharf Riverside quay for commercial use.
260 6203 pier Structure, usually open, that projects from the shore and is
used as a promenade or to provide berths.
260 6204 jetty Structure that provides access to one or more berths at some
distance from the shore.
260 6205 jetty head Platform structure at the offshore end of a jetty.
260 6206 lead-in jetty Framed structure that guides vessels into the entrance of a
confined area such as a lock or dock.
260 6207 staithe Elevated waterside structure for loading vessels.
260 6208 island berth Berth at which a vessel is moored to an isolated structure
that is not structurally connected to the shore.
260 6209 berthing line Line of face of undeflected fender at a defined water level on a
quay or, where no fenders exist, the quay wall face.
260 6210 basin Area of open water, such as that on a canal or in a harbour,
that provides berths.
260 6211 impounded basin Basin connected to tidal water by a lock and in which the
water level is approximately constant.

260 6212 tidal basin Basin directly connected to tidal water.
260 6213 yacht basin Area of water within a harbour that is allocated specifically
for berthing of yachts.
260 6214 marina Basin with berthing facilities and ancillary services for
pleasure craft.
260 63 Fenders
260 6301 fender Energy absorbing device on the side of a vessel or shore
structure for protection from damage due to impact.
260 6302 elastomeric fender unit Unit formed of elastomeric material that absorbs the energy
of impact of a ship during berthing by being deformed
elastically by compression, bending or shear or a combination
of such effects.
260 6303 pneumatic fender unit Elastomeric container filled with air under pressure that
absorbs the energy of impact of a ship during berthing.
260 6304 hydraulic fender Fender in which the energy of impact during berthing is
absorbed by a hydraulic device.
260 6305 non-recoiling fender Hydraulic fender with a series of horizontally mounted
hydraulic jacks that exert a force against the hull of a ship
through a fender face, counteracted by the mooring lines.
BS6100-2.6:1991
14
© BSI 07-1999
No. Term Definition
260 6306 floating fender Fender that consists of floating baulks, cylindrical bundles of
timber or elastomeric cylinders.
260 6307 hanging fender Fender that comprises a timber frame suspended from a
marine structure.
260 6308 gravity fender Fender that absorbs the energy of impact during berthing by
raising a suspended weight.
260 6309 rotating fender Fender that comprises one or more pneumatic tyres or

elastomeric cylinders that rotate on a vertical axis to
facilitate movement of a ship along a quay or into a dock.
260 6310 collapsible steel fender Fender that consists of a corrugated steel tube that absorbs
excessive energy of impact during berthing by plastic
deformation.
260 6311 spring fender Fender in which steel springs are used, usually to provide the
top support for fender piles acting as propped cantilevers.
260 6312 brushwood fender Floating fender composed of bundles of brushwood.
260 6313 buoyant fender Fender, anchored to the sea bed, that floats in front of a quay
face and that is forced backwards and downwards during
berthing.
260 6314 fender pile Cantilever pile installed in front of a marine structure to act
as a fender.
260 6315 rubbing strip Replaceable hardwearing abrasion-resistant facing strip on
the side of a vessel or quay.
260 64 Breakwaters
260 6401 breakwater Long structure in the sea to protect a harbour or shore from
waves.
260 6402 rubble mound
breakwater
Breakwater that consists primarily of rocks dumped or placed
on the sea bed.
260 6403 vertical face
breakwater
Breakwater in which wave attack is resisted primarily by a
vertically faced structure that extends directly from sea bed
level.
260 6404 composite breakwater Breakwater that consists of a submerged rubble mound
surmounted by a vertically faced structure projecting above
sea level.

260 6405 main breakwater Breakwater that forms the side of a harbour from which the
prevailing wind blows.
260 6406 lee breakwater Breakwater that forms the side of a harbour remote from the
prevailing wind.
260 6407 island breakwater
mole
deprecated
Breakwater not connected to the shore.
260 6408 roundhead Rounded enlargement at the end of a breakwater or rounded
end to a dock entrance wall to reduce adverse effects of flow
past it.
260 65 Miscellaneous
260 6501 dolphin Isolated structure or strong point used either to manoeuvre a
vessel or to facilitate holding it in position in a berth.
BS6100-2.6:1991
© BSI 07-1999
15
No. Term Definition
260 6502 mooring dolphin Dolphin with mooring bollards or hooks for securing a vessel
with mooring lines.
260 6503 flexible dolphin Dolphin constructed of vertical piles cantilevered from the
bed of a river or the sea that absorbs the energy of impact
during berthing by deflection of the piles.
260 6504 warping dolphin Dolphin provided at one end of a structure or at a change in
direction of a berth to support vessels being manoeuvred
between two adjacent positions by the use of mooring lines.
260 6505 breasting dolphin
berthing dolphin
deprecated
Dolphin designed to take the impact of a berthing vessel or to

prevent a moored vessel being pivoted by wind and current
about a short jetty head.
260 6506 bell dolphin Dolphin surmounted by a heavy bell-shaped fender that is
free to rock under impact from a vessel and whose centre of
gravity is thereby raised to absorb berthing energy.
260 6507 berthing beam Isolated piled structure, with a continuous capping situated
parallel to a berth, that has a similar function to two or more
breasting dolphins.
260 6508 slipway
drawdock
deprecated
Inclined structure, built partly under water, on which vessels
are launched and hauled out of water.
260 6509 shipbuilding berth Inclined structure on which vessels are built and launched.
260 6510 launchway Track on which a ship on a shipbuilding berth is launched.
260 6511 traversing slipway Slipway at the top of which a ship can be moved laterally,
leaving the slipway clear.
260 6512 mooring bollard Strong shaped post or pair of posts, usually of cast iron, fixed
to a waterside structure for the attachment of mooring lines.
260 6513 fairlead Guide to change the direction of a rope without causing
damage.
260 6514 capstan Machine that has a vertically mounted concave sided drum
on which a rope may be wound under power but not stored.
260 6515 harbour resonance Wave resonance that occurs in a harbour when reflections of
certain wavelengths reinforce and amplify the incident wave
pattern.
260 6516 lead-in dolphin Dolphin to guide a vessel.
260 7 Waves, tides and offshore structures
260 71 Waves
260 7101 wavelength Distance between two successive wave crests.

260 7102 wave period Time for two successive wave crests to pass a fixed point.
260 7103 wave height Height of a wave crest above the preceding wave trough.
260 7104 wave amplitude Half the wave height.
260 7105 significant wave height Average height of the highest one-third of the waves.
260 7106 significant wave period Average of the periods of the highest one-third of the waves.
260 7107 phase velocity Speed at which a wave propagates.
260 7108 wave steepness Ratio of wave height to wavelength.
260 7109 incident wave Incoming wave with reference to a shore or structure.
BS6100-2.6:1991
16
© BSI 07-1999
No. Term Definition
260 7110 reflected wave Wave that is returned seaward when an incident wave
impinges on a steep or vertical surface.
260 7111 coefficient of reflection Ratio of the wave height of a reflected wave to the wave height
of the incident wave.
260 7112 wave group Series of waves in which direction, wavelength and wave
height vary only slightly.
260 7113 wave energy spectrum Graph that shows the distribution of wave energy as a
function of wave period or frequency.
260 7114 spectral density Measure of the wave energy of the sea at a particular time
and location expressed as a function of wave frequency and
direction.
260 7115 monochromatic waves Series of waves, each of which has the same wavelength and
wave period.
260 7116 random waves Waves of varying wave height and wave length as they occur
in the sea.
260 7117 non-breaking wave Stable wave.
260 7118 breaking wave Wave that has reached a condition of instability.
260 7119 broken wave Wave that has become unstable and has broken.

260 7120 swell Waves at a location generated by winds remote from that
location.
260 7121 wake Recurring eddies downstream of an obstacle or moving
vessel.
260 7122 bore
eagre
regional
Wave that has a nearly vertical front advancing upstream in
some estuaries and that results from a rising tide.
260 7123 tsunami Wave caused by an earthquake or eruption of the sea bed.
260 7124 still water level Level that the surface of the water would assume if all wind
and wave action were absent, at a pressure of1bar
a
.
260 7125 wave forecasting Estimation of future wave characteristics.
260 7126 wave hindcasting Use of historical weather data to calculate characteristics of
waves that probably occurred at some time in the past.
260 7127 relative depth Ratio of water depth to wavelength.
260 7128 shallow water Water of relative depth below0.05, in which wave
characteristics are determined by water depth.
260 7129 intermediate water (2) Water of relative depth between0.05 and0.5.
260 7130 deep water Water of relative depth greater than0.5, in which depth has
no effect on wave characteristics.
260 7131 fetch length Distance, uninterrupted by land, over which wind-generated
waves are formed.
260 7132 fetch Area in which waves are generated.
260 7133 group velocity Velocity of propagation of a wave group, being the velocity at
which the energy of the wave group travels.
260 7134 refraction Change of direction of waves approaching a shore caused by
change in depth of water, with a tendency of the wave crests

to align parallel to bed contours.
a
1bar=10
5
Pa=10
5
N/mm
2
.
BS6100-2.6:1991
© BSI 07-1999
17
No. Term Definition
260 7135 zero-crossing wave
period
Average period of all waves with troughs below and crests
above the mean water level.
260 7136 diffraction Spreading of wave energy around the end of a barrier, such as
a breakwater, into the sheltered region behind it.
260 7137 interference peak Wave peak caused when two waves meet each other obliquely.
260 7138 wave shoaling Change in wavelength due to variations of depth in shallow
water.
260 72 Wave action
260 7201 swash
up-rush
deprecated
Rush of water up a beach or other sloping structure as a
result of the action of waves.
260 7202 swash run-up
wave run-up, run-up

deprecated
Difference between swash height and still water level.
260 7203 swash height Maximum elevation of swash.
260 7204 swash zone Area on which swash occurs.
260 7205 overtopping Water that passes over the top of a structure as a result of
wave action or abnormally high water level.
260 73 Currents
260 7301 tidal stream Current in the sea caused by tidal forces.
260 7302 non-tidal current
current
deprecated
Current in the sea other than tidal stream.
260 7303 wind stress current Non-tidal current in the sea generated by wind.
260 7304 surge current Non-tidal current in the sea resulting from surge.
260 74 Tides
260 7401 diurnal tide Tide that has one high water and one low water in a lunar
day.
260 7402 semi-diurnal tide Tide that has two high waters and two low waters in a lunar
day.
260 7403 flood tide That part of a tide when the water level is rising.
260 7404 ebb tide That part of a tide when the water level is falling.
260 7405 high water
high tide
deprecated
Maximum water level reached by each flood tide.
260 7406 low water
low tide
deprecated
Minimum water level reached by each ebb tide.
260 7407 spring tides Tides on the two occasions in a lunar month when the

average range of two successive tides is greatest.
260 7408 neap tides Tides on the two occasions in a lunar month when the
average range of two successive tides is least.
260 7409 mean high water springs
high water springs
deprecated
Average, over a long period, of the heights of two successive
high waters at spring tides.
BS6100-2.6:1991
18
© BSI 07-1999
No. Term Definition
260 7410 mean low water springs
low water springs
deprecated
Average, over a long period, of the heights of two successive
low waters at spring tides.
260 7411 mean high water neaps
high water neaps
deprecated
Average, over a long period, of the heights of two successive
high waters at neap tides.
260 7412 mean low water neaps
low water neaps
deprecated
Average, over a long period, of the heights of two successive
low waters at neap tides.
260 7413 highest astronomical
tide
Highest water level that can be predicted to occur under

average meteorological conditions and under any
combination of astronomical conditions.
260 7414 lowest astronomical
tide
Lowest water level that can be predicted to occur under
average meteorological conditions and under any
combination of astronomical conditions.
260 7415 predicted tide
astronomical tide
deprecated
Water level that can be predicted to occur under average
meteorological conditions.
260 7416 equinoctial tides Highest tides of the year occurring at the spring or autumn
equinox.
260 7417 tidal cycle Variation of water level between two consecutive high waters
or two consecutive low waters.
260 7418 tidal range Difference of level between one high water and the preceding
or following low water.
260 7419 mean sea level Average level of the surface of the sea over a long period,
usually18.6years (one cycle of the moon’s nodes), or the
average level that would exist in the absence of tides.
260 7420 set Direction of tidal stream at a particular time, commonly
related to high water in coastal areas.
260 7421 mean tide level Level midway between mean high water level and mean low
water.
260 7422 tidal limit Point in a tidal length of river at which rise and fall of water
due to tides ceases.
260 7423 chart datum Level to which soundings or elevation of tide heights are
referred, on a stated chart or group of charts, usually taken to
be the lowest astronomical tide.

260 7424 forecast tide Water level that is forecast to occur under predicted
meteorological conditions.
260 75 Results of water action
260 7501 accretion Process of accumulation by flowing water of material such as
silt, sand or gravel.
260 7502 shoreline retrogression Continuing landward movement of the foreshore.
260 7503 beach steepening Increase in slope of a beach under the action of storm waves
that produce an onshore migration of material from the surf
zone.
NOTEIn the United Kingdom this usually occurs in summer.
260 7504 beach flattening Reduction in slope of a beach under the action of storm waves
that produce an offshore migration of material from the surf
zone.
NOTEIn the United Kingdom usually occurs in winter.
BS6100-2.6:1991
© BSI 07-1999
19
No. Term Definition
260 7505 storm ridge High ridge of shingle formed by storms.
260 7506 under run Shingle or sand that leaks under a groyne from the updrift
side to the downdrift side.
260 7507 wash-out Loss of fines from behind a deteriorated embankment
revetment, river wall or sea wall due to the action of currents,
waves or tides.
260 7508 breach Gap in an embankment or dam, caused by failure, that could
allow water to flow through it.
260 76 Offshore structures
260 7601 offshore structure Structure, fixed or mobile, located in the sea beyond the low
water line and not connected structurally to the shore.
260 7602 fixed offshore

structure
Fixed structure intended to remain in one location offshore
supported by the sea bed and not connected structurally to
the shore.
260 7603 mobile offshore
structure
Structure that is moved between locations offshore and that
is either supported by the sea bed or supported by buoyancy
and retained in position by mooring lines.
260 7604 compliant offshore
structure
Fixed offshore structure connected to, or supported on, the sea
bed by an articulated structure or system of tethers, in such a
manner that it moves in sympathy with the action of waves
and wind loading.
260 7605 jack-up structure Mobile offshore structure with spuds that enable the hull of
the structure to be raised above the surface of the water.
260 7606 semi-submersible
structure
Floating mobile offshore structure that is supported by
submerged buoyancy tanks that are below the influence of
waves.
260 7607 gravity platform Fixed offshore structure that is held in position by its weight.
260 7608 drilling platform Offshore structure used in drilling to support a drilling rig
and house support facilities.
260 7609 production platform Offshore structure from which development wells are drilled
on an oil or gas field and that houses the equipment to
process the oil and gas.
260 7610 tethered leg platform Floating production platform held in position by vertical legs
that are kept in tension by the buoyancy of the platform.

260 7611 hybrid platform Offshore structure built with a combination of steel and
concrete, with, for example, a concrete substructure and a
steel superstructure.
260 7612 jacket Support structure of a steel production platform below the
topsides.
260 7613 topsides All necessary operating equipment and accommodation
facilities supported above the surface of the sea on an offshore
structure.
260 7614 offshore module Large component part of an installation, completed on land
and installed in an offshore structure in a single lift.
260 7615 drilling template Steel structure on the sea bed that enables a number of
directional wells to be drilled from a semi-submersible
structure or jack up structure without the need for the drilling
rig to move location for each well.