Pictorial Dictionary of Terms
(Compliments of Erosion Technology Consulting)

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Abrasion Removal of streambank soil as a result of sediment-laden water, ice, or debris rubbing against the bank.

Anti-Scour Protection Apron. An apron in front of a revetment to help protect the revetment against underscour.

Armor To protect, protective covering, shield.

Backfill. The process of filling a cavity with soil, gravel rock or other material of choice.

Backshore That zone of the shore or beach including the berm or berms which lies between the foreshore and the dunes or bluffs. The backshore is acted upon by waves only during severe storrns, especially when combined with exceptionally high water.

Backwater area The low-lying lands adjacent to a stream that become flooded during periods of high water.

Bank The part of the soil next to a stream, lake or body of water where the soil elevation adjacent to the water is higher than the water level. Sometimes called an embankment.

Bank Slip When the bank of a stream or body of water slips downward because of erosion & stress.

Bar A sand or gravel deposit found on the bed of a stream that is often exposed only during low water periods.

Beach A deposit of unconsolidated sand along the edge of a sea that extends landward to the base of the dunes or bluff. The zone of sedimentary material that extends landward from the low water line to the place where there is marked change in material or form, or to the line of permanent vegetation (usually the effective limit of storm waves). The seaward limit of a beach--unless otherwise specified--is the mean low water line. A beach includes foreshore and backshore.

Bed The bottom of a channel, creek, river, stream, or other body of water.

Bed slope The inclination of the channel bottom.

Bend A change in the direction of a stream channel.

Berm A nearly horizontal part of the beach or backshore formed at the high water line by waves depositing material. Some beaches have no berms, others have one or several.

Blanket Material placed on a streambank to cover eroding soil.

Bluff A high, steep bank or cliff.

Breakwater A structure protecting a shore area, harbor, anchorage, or basin from waves.

Bulkhead A partition to retain or prevent sliding of the land. A secondary purpose is to protect the upland against damage from wave action. Often referred to as: Seawall, Retaining wall, Revetment and occasionally as Armor (like in, to armor the embankment).

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Catchment An area confined by drainage divides usually having only one streamflow outlet. * In the UK, the term "catchment" refers to what we call the drainage divide. They use the term "catchment" to refer to what we would call a watershed.

* Credit: Richard B. Winston (Wetlands & Hydrology)

Caving The collapse of a streambank by undercutting due to wearing away of the toe or an erodible soil layer above the toe.

Channel A natural or man-made waterway that continuously or periodically passes water.

Check dam A structure placed bank to bank downstream from a headcut.

Clay Cohesive soil whose individual particles are not visible to the unaided human eye. Soil can be molded into a ball that will not crumble.

Cliff A high, steep face or rock; a precipice.

Coast The strip of land, of indefinite width (up to several miles), that extends from the shoreline inland to the first major change in terrain features.

Cohesive soil Microscopic soil particles that have natural resistance to being pulled apart at their point of contact.

Current The flow of water through a stream channel.

Cutbank The outside bank of a bend, often eroding and across the stream from a point bar.

Cutoff A channel cut across the neck of a bend.

Deadman A log or block of concrete, or other material buried in a streambank that is used to tie in a revetment with cable, chain, or steel rods.

Dike (groin, palisade, spur, jetty, deflector) A structure designed (1) to reduce the water velocity as streamflow passes through the dike so that sediment deposition occurs instead of erosion (permeable dike) or (2) to deflect erosive currents away from the streambank (impermeable dike).

Discharge The volume of water passing through a channel during a given time, usually measured in cubic feet per second.

Distressed streambank A bank that has (or is) suffering erosion or failure.

Downdrift The longshore direction of predominant movement of littoral materials.

Dredge material Soil that is excavated from a stream channel, lake or other body of water.

Dunes Ridges or mounds of loose, wind-blown material, usually sand.

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Eddy current A circular water movement that develops when the main flow becomes separated from the bank. The eddy current may then be set up between the main flow and the bank.

Embankment The part of the soil next to a stream, lake or body of water where the soil elevation adjacent to the water is higher than the water level. Usually referred to as the "bank."

Erosion In the general sense, the wearing away of the land by wind and water. As used in this subject material, the removal of soil particles from a bank slope primarily due to water action.

Failure Collapse or slippage of a large mass of bank material into a stream.

Fetch The area in which seas are generated by a wind having a rather constant direction and speed.

Fill material Soil, rock, gravel or other matter that is placed at a specified location to bring the ground surface up to a desired elevation.

Filter Layer of fabric, sand, gravel, or graded rock placed between the bank revetment or channel lining and soil for one or more of three purposes: to prevent the soil from moving through the revetment; to prevent the revetment from sinking into the soil; and to permit natural seepage from the streambank, thus preventing buildup of excessive groundwater pressure. If a filter is used by a landowner or local government, technical assistance should be obtained to properly match the filter with the soil.

Fine particles (or Fines) Silt and clay particles.

Flanking Streamflow between a structure and the bank, possibly occurring because the structure was not properly tied into the bank. See Wingwall

Foreshore The part of the shore lying between the crest of the berm (or upper limit of wave wash at high tide) and the ordinary low-water mark, that is ordinarily traversed by the uprush and backrush of the waves as the tides rise and fall.

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Gabion Baskets (usually made of wire) filled with rock or broken pieces of concrete.

Gabion Basket A basket (usually made of wire) for building gabion structures for erosion control.

Geotextile Fabric A man made fabric used in the control of soil erosion. The fabric is available in roles of various widths and lengths, (color standards are usually white, black or gray) and usually vary from one manufacturer to the other. Various specifications are available for varying soil types and applications. The product is sometimes referred to as "filter fabric".

Gravel Soil particles ranging from 1/5 inch to 3 inches in diameter.

Greenbelt Strip of trees and shrubs growing parallel to a stream that prevents overuse of the top bank area by man, animals, and machinery. This strip of vegetation also retards rainfall runoff down the bank slope and provides a root system which binds soil particles together.

Groin A shore protection structure built (usually perpendicular to the shoreline) to trap littoral drift or retard erosion of the shore.

Groundwater flow Water that moves through the subsurface soil and rocks.

Groundwater table The depth below the surface where the soil is saturated; that is the open spaces between the individual soil particles are filled with water. Above the groundwater table and below the ground surface the soil either has no water between the particles or is partially saturated.

Headcutting The action of an upstream moving waterfall or locally steep channel bottom with rapidly flowing water through an otherwise placid stream. These conditions often indicate that a readjustment of a stream's discharge and sediment load characteristics is taking place.

Impermeable material A soil that has properties which prevent movement of water through the material.

Infiltration That portion of rainfall or surface runoff that moves downward into the subsurface rock and soil.

Jetting A method of placing piles or sheeting by forcing water around and under a pile or sheeting to displace and lubricate the surrounding soil, allowing the pile or sheeting to sink to the desired position.

Launching Process where stone stockpiled along top bank is undercut and slides down slope thus protecting the bank against future erosion.

Life An estimated time period over which a structure will function if limited only by deterioration of materials.

Littoral Of or pertaining to a shore, especially of the sea.

Littoral Drift The sedimentary material moved in the littoral zone under the influence of waves and currents.

Littoral Material See Littoral Drift.

Littoral transport The movement of littoral drift along the shoreline by waves and currents. Includes movement parallel (longshore transport) and perpindicular (on-offshore transport) to the shore.

Longshore Parallel to and near the shoreline.

Lower bank That portion of the streambank below the elevation of the average water level of the stream.

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Marsh An area of soft, wet, or periodically submerged land, generally treeless and usually characterized by grasses and other low vegetation.

Microscopic soil particles Clay and silt; particles that cannot be observed by the unaided human eye.

Navigable streams Waterways of sufficient depth and width to handle a specified traffic load.

Neap tide A tide having about 10 or 30 percent less range than the average, occuring about the time of quarter moons.

Noncohesive soil Soil particles that have no natural resistance to being pulled apart at their point of contact, for example, silt, sand, and gravel.

Nourishment The process of replenishing a beach. It may be brought about naturally, by accretion due to the longshore transport, or artificially, by the deposition of dredged materials.

Offshore The direction away from the shore, toward a large body of water.

Onshore The landward direction, away from the water.

Overbank drainage Water flow over top bank and down the slope.

Overtopping The passing of water over the top of a natural or man-made structure as a result of wave runup or surge.

Palisade A barrier

Perched Beach A beach retained above the otherwise normal profile level by a submerged sill.

Permit A document granting permission to do something. A Corps of Engineer's permit is a document issued by the Department of the Army expressing the assent of the Federal Government so far as concerns the public rights of navigation and the general public interest of certain works on or adjacent to navigable waters of the U.S. Often required by cities, municipalities, flood control authorities, county governments, river authorities, and civic associations.

Pile A long, heavy timber, pipe, or section of concrete or metal to be driven or jetted into the earth or seabed to serve as a support for a bulkhead.

Pile Rot The rotting of wood pile caused by being exposed to the weather.

Pile, sheet A pile with a slender flat cross section to be driven into the ground or seabed and meshed or interlocked with similar sheets to form a bulkhead. May be aluminum, fiberglass, steel, vinyl, wood or other suitable materials.

Piping Flow of groundwater through subsurface conduits in the bank.

Place Synonym for construct; for example, to say that "a rip rap revetment was placed on the streambank" is the same as saying "a rip rap blanket was constructed on the streambank."

Point bar The bank in a bend that has built up due to sediment deposition.

Project As used in this subject matter, the planning, construction, and maintenance of a revetment or river training works placed to protect a streambank.

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Rapid drawdown Lowering the elevation of water against a bank faster than the bank can drain leaving a pressure imbalance that may cause the bank to fail.

Reach A section of a stream's length.

Revetment A facing of stone, bags, blocks, pavement, etc., used to protect or armor a bank against erosion.

Rill Erosion Removal of soil particles from a bank slope by surface runoff moving through relatively small channels.

Riprap A layer, facing, or protective mound of stones, randomly placed to prevent erosion or scour at a structure or embankment,- also the stone so used.

Rubble Rough, irregular fragments of broken rock or concrete, (rip rap).

River training works Structures placed in a stream to direct the current into a predetermined channel.

Rock Soil particles greater than 3 inches in diameter.

Rooted Expression indicating that a bank has been excavated and the end of a structure (check dam, dike, etc.) has been placed in the cavity, thus retarding future streamflow around the end of the structure (flanking).

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Rubble Rough, irregular fragments of rock or concrete. Runup The rush of water up a beach or structure, associated with the breaking of a wave. The amount of runup is measured according to the vertical height above still water level that the rush of water reaches.

Sand Soil particles ranging from 3/1000 inch to 1/5 inch in diameter; 3/1000 inch is the normal lower limit at which the unaided human eye can distinguish an individual particle.

Sand/Cement Bag Revetment A retaining wall (bulkhead) built of sand/cement bags.

Scour The erosive action of flowing water in streams that removes and carries away material from the bed and banks.

Scour pockets The erosive action of flowing water in streams that removes and carries away material from the bed and banks in a particular area or pocket.

Seawall A structure separating land and water areas, primarily designed to prevent flooding and erosion due to wave action. Bulkhead, revetment, or retaining wall.

Shore The narrow strip of land in immediate contact with the sea, or other body of water, including the zone between high and low water lines. A shore of unconsolidated material is usually called a beach.

Sediment Soil particles that have been transported away from their natural location by wind or water action.

Sediment deposition The accumulation of soil particles on the channel bed and banks.

Sediment load The soil particles transported through a channel by streamflow.

Seepage Groundwater emerging on the face of a streambank.

Shear Force parallel to a surface as opposed to directly on the surface. An example of shear would be the tractive force that removes particles from a streambank as flow moves over the surface of the slope; on the other hand, a floating log that directly strikes the bank would not be a shear force.

Sheet erosion The removal by surface runoff of a fairly uniform layer of soil from a bank slope.

Sheet pile A pile with a generally slender, flat coss-section that is driven into the ground or bottom of a water body and meshed or interlocked with like members t form a wall or bulkhead.

Shore The narrow strip of land in immediate contact with the water, including the zone between high and low water lines. See also backshore and foreshore.

Sill See check dam.

Silt Noncohesive soil whose individual particles are not visible to the unaided human eye. Soil will crumble when rolled into a ball.

Sloughing (or sloughing off). Movement of a mass of soil down a bank into the channel (also called slumping). Sloughing is similar to a landslide.

Soil Soil finer than sand but coarser than clay, but not so fine that it can remain suspended in water for long periods. The grain size is considered to be less than .0625 mm.

Specifications A detailed description of particulars such as size of stone, quality of materials, contractor performance, terms, quality control, etc.

Spring tide A tide that rises highest and falls lowest from mean sea level, occuring at new or full moon.

Storm Surge An increase in water level above the normal water level on the open coast due to the action of wind stress and atmospheric pressure on the sea surface.

Streambank The side slopes of a channel between which the streamflow is normally confined.

Streambank protection works Structure(s) placed on or near a distressed streambank to control bank erosion or to prevent failure.

Streambed See bed.

Streamflow The movement of water through a channel.

Streambank erosion Removal of soil particles from a bank slope primarily due to water action. Climatic conditions, ice and debris, chemical reactions, and changes in land and stream use may also lead to bank erosion.

Streambank failure Collapse or slippage of a large mass of bank material into the channel.

Surface runoff That portion of rainfall that moves over the ground toward a lower elevation and does not infiltrate the soil.

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Texture Refers to relative proportions of clay, silt, and sand in soil.

Tide The periodic rising and falling of water that results from gravitational attraction of the moon and sun acting on the rotating earth.

Tie-back A variety of techniques used to secure the bulkhead, seawall, or revetment in place against the bank.

Tied in An expression used to indicate that a revetment or dike is constructed to prevent or minimize streamflow between the structure and the bank. See Wingwall.

Toe The break in slope at the foot of a bank where the bank meets the bed.

Top bank The break in slope between the bank and the surrounding terrain.

Tractive force The drag on a streambank caused by passing water which tends to pull soil particles along with the streamflow.

Updrift The longshore direction opposite that of the predominant movement of littoral materials.

Unravel To lose material from the edges of a revetment.

Updrift The direction opposite that of the predominant movement of littoral materials.

Upper bank That portion of the streambank above the elevation of the average water level of the stream.

Velocity (of water in a stream) The distance that water can travel in a given direction during an interval of time.

Wale Structural element of a bulkhead, fixed horizontally between the vertical piles on the seaward side and the sheet piles on the landward side.

Waters of the United States Includes all dry land and water-covered areas below the ordinary high water marks on navigable and nonnavigable streams.

Water Level The elevation of the free water surface of a body of water above or b@low any datum. Mean water level is the average water elevation at a particular place and time.

Watershed An area confined by drainage divides usually having only one streamflow outlet. * In the UK, the term "watershed" refers to what we call the drainage divide. They use the term "catchment" to refer to what we would call a watershed.
(see catchment)
* Credit: Richard B. Winston (Wetlands & Hydrology)

Wave attack Impact of waves on a streambank.

Wave length The horizontal distance between similar points on two successive waves (for example, crest to crest or trough to trough), measured in the direction of wave travel.

Wave height The vertical distance between a wave crest and the preceding trough.

Weathering Physical disintegration or chemical decomposition of rock due to wind, rain, heat, freezing, thawing, etc.

Weephole Opening left in a revetment or bulkhead to allow groundwater drainage.

Wingwall The end portion of a bulkhead, seawall, or revetment that cuts back in toward the bank, usually at a right angle to the main structure. The purpose of a wingwall is to help retard or prevent flanking.

Wood Bulkhead with it's components identified.

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