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Glossary A Class tide gauge One of a UK network of tide gauges maintained to the highest and most consistent standards. Accretion Gain of material on the shore leading to increased levels, the growth of sand dunes on sandy shores and the expansion of marshes on muddy shores. Apron Layers of stone, concrete or other material to protect the toe of a structure such as a seawall. Armour unit Large quarried stone, or concrete block, used as protection against wave action. Backshore Coastal area between the beach head and high water, potentially affected by large waves during high tides. Barrier beach A sand or shingle bar above high tide, parallel to the coastline and separated from it by a lagoon. Bathymetry Seabed topography. Beach A deposit of non-cohesive mobile material (e.g. sand, gravel) situated on the interface between dry land and the sea (or other expanses of water). Beach face From the beach crest out to the limit of sediment movement. Beach head Ridge, cliff, dune or sea defence forming the landward limit of the potentially active beach Beach profile Beach cross-section perpendicular to the shore, which may extend from the backshore, across the foreshore and into the nearshore zone. Beach recharge Mechanical addition of imported sediment to a beach, also known as beach replenishment/nourishment. Berm Beach: near horizontal plateau above high water, formed by deposition of beach material by wave action or by mechanical plant as part of a beach recharge scheme. Structure: near horizontal area, often separating the upper part of a seawall or revetment from the lower part. Binding Use of chemical glues to create a skin across a sediment surface. Usually applied by spraying. Blowout Wind-eroded area within a dune system. Boghole The Bog Hole is the remnant of a former channel in the Ribble estuary inshore of the Horse Bank. The bed of the Bog Hole was once many metres below low-water. It has filled with sediment during the past two centuries and now its lowest bed level is one metre below the height of the lowest neap tides. Boulder A rounded rock on a beach, greater than 250mm in diameter. Breaching Failure of the beach head or defence structure allowing flooding by tidal action. Breaker zone The zone within which waves approaching the coastline commence breaking, typically in water depths of between 5 and 10 metres. Breastwork Vertically faced or steeply inclined structure built parallel to the shoreline, at or near the crest of the beach, to resist erosion, usually timber. Breakwater Large coastal structure designed to protect an area from wave action, either for navigation or coastal defence. Can be connected to or detached from the shoreline. Bypassing Moving beach material from the updrift to the downdrift side of an obstruction to longshore drift i.e. harbour breakwater, estuary or river mouth. Chart datum The level to which both tidal levels and water depths are reduced - on most UK charts this level is approximately the predicted lowest astronomical tide level (LAT). Coast protection Works or management operations intended to control coastal erosion Coastal cell A division of the shoreline with geographic limits set by the boundaries of natural physical processes, usually coastal sediment movement. See Sediment cell Coastal defence A generic term embracing both “coast protection” which is the protection of land from coast erosion and “sea defence” which is the protection of land from flooding by the sea. Coastal group A coastal-cell partnership of coastal defence operating authorities, environmental organisations, land owners and conservation groups that shares knowledge and experience of shoreline management issues and helps to define objectives for the future management of the shoreline. Coastal processes Collective term covering the action of natural forces on the shoreline, and nearshore seabed. Coastal squeeze The effect when hard defences (including beaches fixed in position by control structures) interrupt the natural response of the shoreline to sea level rise, restricting landward retreat and resulting in loss of the intertidal habitat. Coastline The linear interface between land and sea. Cobble A rounded rock on a beach, with diameter ranging from about 75 to 250mm - see also boulder, gravel, shingle. Cohesive sediment Sediment containing significant proportion of clays, the electromagnetic properties of which cause the sediment to bind together. Community Plants and/or animals living together under characteristic, recognisable conditions. Core An inner, often much less permeable portion of a breakwater, or barrier beach. Crest Highest point on a beach face, breakwater or seawall. Cross-shore Perpendicular to the shoreline. Deflation Erosion of dunes by wind action. Design wave condition Usually an extreme wave condition with a specified return period used in the design of coastal works. Detached breakwater A breakwater without any constructed connection to the shore. Diffraction Process affecting wave propagation, by which wave energy is radiated normal to the direction of wave propagation into the lee of an island or breakwater. Distribution The spatial range of a species, usually on a geographic but sometimes on a smaller scale, or the arrangement or spatial pattern of a species over its habitat Disturbance mso-bidi-font-size:10.5pt; mso-bidi-font-family:Arial;mso-ansi-language:EN-GB'>In community ecology, an event that removes organisms and opens up space which can be colonised by individuals of the same or different species Dominant winds Winds with greatest effect on shoreline processes. Downdrift Direction to which material is being transported in the littoral zone. Dunes Accumulations of windblown sand on the backshore, usually in the form of small hills or ridges, stabilised by vegetation or control structures. Dune face The seaward face of a dune system where coastal processes may cause erosion or accretion. Ebb Period when tide level is falling; often taken to mean the ebb current that occurs during this period. Ebb tide delta Area of sediment deposition caused by a decrease in velocity of tidal currents where there is interaction with more open nearshore conditions. Typically such deltas form at the mouths of estuaries and restricted channels where they enter the sea Ecology The study of the interactions of organisms with their physical environment and with one another Ecosystem All of the organisms of a given area and the encompassing physical environment Embankment A bank protecting land from flooding. Embryo dune Erosion Loss of material from the shore leading to reduced levels and, in the absence of a hard line of defence, landward recession of the coastline. Estuary A semi-enclosed coastal body of water within which seawater is measurably diluted with fresh water derived from land drainage. Extreme The value expected to be exceeded once, on average, in a given (long) period of time. Fetch Distance over which a wind acts to produce waves - also termed fetch length. Fetch-limited Situation in which wave energy (or wave height) is limited by the size of the wave generation area (fetch). Fixed dune Dune with a surface stabilised by vegetation. Foredune Developing dune which lies nearest the sea in a prograding system, also embryo-dune. Foreland Backshore area formed by the deposition of sediment which is no longer part of an active coastal process system Foreshore Shore between high and low water - see also intertidal. Freeboard The height of the crest of a structure above the still water level. Gabion Wire mesh baskets filled with rock. Geotextile Synthetic or natural fabrics used in engineering to separate layers of granular material. Gravel Beach material usually well rounded and between about 2mm and 75mm in diameter - see also shingle. Grey dune Well.vegetated fixed dune with mosses, lichens, grasses and herbs. Groyne Narrow, shore-normal (approximately) structure built to reduce longshore currents, and/or to trap and retain beach material. Most groynes are of timber or rock, and extend from the beach head across the foreshore. Groyne bay The beach compartment between two groynes. Habitat The recognisable area or type of environment in which an organism normally lives. Hard defences General term applied to impermeable coastal defence structures of concrete, timber, steel, masonry etc, which reflect a high proportion of incident wave energy. cf. Soft defences Headland Hard feature (natural or artificial) forming local limit of longshore extent of a beach. High-water line The highest line on the shore or at the coastline to which tides rise and advance landward. Horsebank The Horsebank is a broad-crested bank of sand that appears on 19th and 20th charts of the coast. Its crest, about 2 metres above the level of the adjoining shore, is roughly parallel to and about 2 kilometres distant from the Southport coastline.  The crest is covered by 85% of tides. Intertidal The zone between high and low tide lines - see also foreshore. Joint probability The probability of two (or more) events occurring together. Leach The process by which percolating water removes nutrients from the soil Littoral drift Movement of beach material in the littoral zone under the influence of waves and currents. Littoral zone Zone from the beach head seawards to the limit of wave induced sediment movement. Longshore drift Movement of (beach) sediments approximately parallel to the coastline. Low-water line The lowest line on the shore to which tides fall and retreat seaward. Macro-tidal Tidal range greater than 4m. Managed realignment The setting back of existing coastal defences in order to achieve environmental, economic and/or engineering benefits. Typically being undertaken in estuarine systems to combat the issue of coastal squeeze Meso-tidal Tidal range between 2m and 4m. Micro-tidal Tidal range less than 2m. Migration The movement of individuals and commonly whole populations from one area to another Mobile Dune Mud flat An area of fine silt usually exposed at low tide but covered at high tide, occurring in sheltered estuaries or behind shingle bars or sand spits. Mulching Mixing organic material into the sediment surface to reduce erosion, moisten the surface and fertilise the soil. Natural succession The process by which one community of organisms gives way to another in an orderly series from colonisers to climax. Neap tide A tide of lower range than an average (“ordinary”) tide due to the sun’s and moon’s gravitational forces acting on the sea at an angle to each other. Nearshore Areas where waves are transformed by interaction with the sea bed. Numerical modelling Refers to the analysis or prediction of coastal processes using computational models. Offshore The zone beyond the nearshore zone where sediment motion induced by waves alone effectively ceases and where the influence of the sea bed on wave action has become small in comparison with the effect of wind. Overtopping The process where water is carried over the top of an existing defence due to wave activity Overwash The effect of waves overtopping a beach, often carrying sediment landwards Physical modelling Refers to the investigation of coastal processes using a scaled model. Pocket beach A beach located between two headlands. Population Any group of individuals, usually of a single species, occupying a given area at the same time Prevailing winds Winds of greatest frequency, often but not always the dominant winds. Prograding Developing along the shore or into open water. Psamosere The succession of plants on sand especially dunes systems Reef A ridge of rock, or other material, lying seawards of the low water line. Refraction Process by which the direction of a wave moving in shallow water at an angle to the bathymetric contours is changed so that the wave crests tend to become more aligned with those contours. Regrading The mechanical movement of beach sediment from the lower foreshore to the upper foreshore -see also reprofiling. Reprofiling The mechanical movement of beach sediment from downdrift to updrift - see also regrading. Return period Average period of time between occurrences of a given probability event. Revetment Structural reinforcement on the seaward slope of a coastal embankment. Rhizome Fleshy root.ball of plant from which roots and side shoots develop. Run-up, Run-down The upper and lower levels reached by a wave on a beach or coastal structure, relative to still. water level. Salient Coastal formation of beach material developed by wave refraction and diffraction and longshore drift comprising a bulge in the coastline towards an offshore island or breakwater, but not connected to it as in the case of a tombolo. Salt marsh Intertidal area having characteristic vegetation adapted to saline soils and to periodic submergence in sea water. Sand Sediment particles, mainly of quartz, with a diameter of between 0.062mm and 2mm, generally classified as fine, medium, coarse or very coarse Sea defence Works or management operations intended to prevent coastal flooding Sea level rise The general term given to the upward trend in mean sea level resulting from a combination of local or regional geological movements and global climate change Seawall Solid near vertical coastal defence structure built parallel to the coastline, usually of concrete or masonry. Sediment Granular material of which a shore, riverbed or seabed is comprised.  Sediment is moved on to, along and away from the shore by wind, waves and currents. It can be transported by air or water currents over the ground or seabed or may be carried in suspension in air or water.  Fine sediment (silt or mud) settles slowly in low energy environments.  Coarse sediment (sand or gravel) settles quickly and is transported in higher energy environments. Sediment cell In the context of a strategic approach to coastal management, a length of coastline confined by natural or artificial barriers around which no sand or shingle can be transported — also know as coastal cell. Sediment sink Point or area at which beach material is irretrievably lost from a sediment cell, such as an estuary, or a deep channel in the seabed. Sediment source Point or area on a coast from which beach material arises, such as an eroding cliff, or river mouth. Shingle Coarse grained beach sediment dominated by gravel but including some sand. Shoreline One characteristic of the coast, often poorly defined, but essentially the interface between land and sea. Shingle ridge Feature of the upper beach, comprising built up deposits of shingle often fronting lower lying backshore Shore Inter-tidal land between the high and low water marks of spring tides. Shoreline A zone that encompasses near-shore coastal waters, the shore, the coastline and its immediate hinterland Shoreline Management Plan or SMP SMPs have been produced for the whole coastline of England and Wales with limits determined by natural physical processes to enable operating authorities to identify long-term sustainable policies for the coastal defence of the shoreline.  Sefton has two of the SMPs: - Liverpool Bay (Great Orme to Formby Point) and Ribble Estuary (Formby Point to the River Wyre). Significant wave Measured as the average height of the highest third of the waves in a sea, and is approximately height the visually observed wave height (H, or H). Sill Continuous shore parallel structure, submerged at high tide. Silt Sediment particles with a grain size between 0.004mm and 0.062mm i.e. coarser than clay particles but finer than sand. Slack Area within dune system where the surface is at or near the ground water level. Soft defences Usually refers to managed beaches, salt marshes or mudflats that provide protection to the shoreline, but may also include rock structures which dissipate waves rather than opposing them. cf. Hard defences Spring tide A tide of greater range than an average (“ordinary”) tide due to the sun’s and moon’s gravitational forces acting on the sea approximately in line with each other. Spring and neap tides occur in sequence following a lunar half-monthly cycle of approximately 15 days.  There are also longer-term cycles that vary according to astronomic circumstances. Spit A long, narrow accumulation of sand or shingle, lying generally in line with the coast, with one end attached to the land and the other protecting into the sea or across the mouth of an estuary. Strand line Line of debris formed at the limit of wave run up along the upper foreshore. Surge Changes in water level as a result of meteorological forcing (wind, high or low barometric pressure) causing a difference between the recorded water level and that predicted using harmonic analysis; may be positive or negative. Succession The orderly progression of changes in a community composition that occurs during development of vegetation in any area from initial colonisation to the attainment of the climax typical of a particular geographic area Suspended load A mode of sediment transport in which the particles are supported, and carried along by water. Swash zone The zone of wave action on the beach, which moves as water levels vary, extending from the limit of run-down to the limit of run-up. Swell (waves) Remotely wind-generated waves. Swell characteristically exhibits a more regular and longer period and has longer crests than locally generated waves - see also wind sea. Surf zone The zone of wave action extending from the water line (which varies with tide, surge, set-up, etc.) out to the most seaward point of the zone (breaker zone) at which waves approaching the coastline commence breaking, typically in water depths of between 5 and 10 metres. Tidal current Horizontal motion of water responding to changes in sea level during a tidal cycle Tidal range The vertical distance (height or amplitude) between sea level at low-water and sea level at high-water during a single tide.  The maximum range of spring tides at Southport is approximately 10 metres and the minimum range of neap tides is approximately 4.5 metres. Tide Vertical movement of the sea caused by the gravitational attraction of sun and moon.  Each tidal cycle (from high-to low-to high) takes approximately 12.5 hours. Tombolo Coastal formation of beach material developed by refraction, diffraction and longshore drift to form a ‘neck’ connecting a coast to an offshore island or breakwater - see also salient. Thatching Covering of brushwood laid down to protect dune grasses and help trap sand. Updrift Direction from which material is being transported in the littoral zone. Vegetated shingle Plant communities on shingle ranging from pioneer plant species on fringing shingle beaches through to lichen-rich turf to gorse scrub on disturbed or marginal areas and where grazed to a species-rich turf. Water table Level below which the soil is waterlogged. Wave climate The seasonal and annual distribution of wave height, period and direction. Wave direction Mean direction of wave energy propagation relative to true North. Wave height Vertical distance from wave trough to crest. Wave period Time taken for the passage of successive waves past a point. Wave spectrum Distribution of wave energy as a function of wave frequency and direction. Wave transformation Change in wave energy due to the action of physical processes. Wind rose Diagram showing the long term distribution of wind speed and direction. Wind sea Wave conditions directly attributed to recent winds - see also swell. Wind set-up Elevation of the water level over an area directly caused by wind stress on the water surface. Yellow dune Incompletely vegetated dune with bare sand frequently exposed between plan Home Page - Top www.seftoncoast.org.uk

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