Help:Dictionary

Term	Definition
Accretion	Process by which particles carried by the flow of water or by the wind are deposited and accumulate (opposite is erosion).
Adaptive management	An approach to managing systems with inherent uncertainties that involves learning from the system’s responses to intervention, then using that learning to improve future management
Agri-environment scheme	Land management scheme that provides funding to farmers and other land managers in England to deliver effective environmental management on their land.
Alien species	See invasive non native species.
Anastomosis	This is the reconnection of two streams that previously branched out.
Anastomosing	See page: Anastomosing
Angiosperms	Flowering plants, a Biological Quality Element (BQE) under the Water Framework Directive
Average channel gradient category	Channel gradient is the grade measured by the ratio of drop in elevation of a stream per unit horizontal distance
Average channel gradient	Channel gradient is the grade measured by the ratio of drop in elevation of a stream per unit horizontal distance
Asset	In flood defence, any man-made or natural feature – such as a raised defence, retaining structure, channel, pumping station or culvert – that performs a flood defence or land drainage function
Attenuation	The reduction in the peak discharge of a flood which may occur as the flood passes downriver, including the effects of any flood storage ponds and reservoirs
Backwater	A ‘dead-end’ channel, which is typically a remnant of a previous route of a meandering watercourse
Bagwork	A form of revetment constructed from dry-filled bags of a weak sand-cement mix. The bags are either hessian or plastic and are part-filled with the sand-cement mix. They are then placed on the soil surface to form a revetment, with staggered joints, and tamped into place. The sand-cement mix hardens over time and the bag material ages to give a more natural appearance. Can also be used to form low retaining walls.
Bank Stability	The ability of a river bank to counteract erosion or gravity forces
Bankfull	The bankfull stage is associated with the flow that just fills the channel to the top of its banks and at a point where the water begins to overflow onto a floodplain.
Bed	The area between the banks of a river ordinarily covered by water
Benefit cost ratio	Is the parameter which describes how many €s of societal benefit has resulted from €1 of cost investment. It is calculated by: Benefit cost ratio = present value benefit/present value cost. For example if a project delivers €3k benefits for €1k cost then the benefit cost ratio will be 3/1 = 3.
Benthic	Relating to the bed of a water body or to the organisms that live there.
Berm	A low, often wet, ledge or terrace at the edge of the stream that constricts the flow and allows a vegetated wetland margin to develop.
Biodiversity	All the species living in a particular area
Biological	Relating to life or living organisms
Biota	The total collection of organisms of a geographic region or a time period.
Bund	An embankment, typically earth
Catchment	The land (and its area) which drains (normally naturally) to a given point on a river, drainage system or other body of water
Coir	a natural fibre extracted from the husk of coconuts. It can be formed into mattresses and rolls for use in river bank erosion control and vegetation establishment.
Communities	An assemblage of two or more populations of different species occupying the same geographical area.
Conveyance	For a channel, function of the flow area, shape and roughness of a channel, which can be used as a constant in a formula relating discharge capacity to channel gradient
Cost Effectiveness Analysis	A technique which seeks to identify the least cost option for meeting a particular objective. It enables prioritisation between options, but ultimately does not assess whether an option is economically worthwhile (cost benefit analysis would be employed to do this)
Coppicing	Traditional management of trees and shrubs for wood production by cutting stems close to the base and removing regrowth periodically.
Culvert	A closed conduit carrying a watercourse beneath an obstruction such as a road, railway or canal. The term ‘closed’ implies that a culvert has a hard soffit and invert. The term ‘conduit’ implies the conveyance of water some or all of the time, thereby excluding tunnels and underpasses for vehicles, pedestrians and animals.
Dredging	Underwater excavation, usually including removal of the excavated material
Dominant geology	Classifies the material that predominates in the project area: Calcarous, Organic, Siliceous
Ecoregion	This is a geographically and ecologically large unit of land containing characteristic, geographically distinct assemblages of natural communities, species and environmental conditions. Select from: Iceland; Tundra; Borealic uplands; Fenno-Scandian Shield; Taiga; Great Britain; Ireland and Northern Ireland; Central Plains; Baltic Province; Eastern Plains; Central Highlands; Western Plains; Western Highlands; Alps; Hungarian Lowlands; Carpathians; Pontic Province; Caspic Depression; Pyrenees; The Caucasus; Eastern Balkan; Hellenic Western Balkan; Dinaric Western Balkan; Italy and Corsica; Ibero-Macaronesian
Embankment	A raised structure (as of earth or gravel) used especially to hold back water.
Erosion	Process by which particles are removed by the action of wind, flowing water or waves (opposite is accretion)
Estuary	An estuary is a partly enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea.
Faggot, fascine	A bundle of brushwood tied together into a cylindrical shape. Used to provide temporary erosion protection to a channel bank; to form flow deflectors; and to promote the deposition of sediment in marginal areas.
Fish pass	Structure to enable fish to gain access past a weir, sluice, dam or other structure in a river that would otherwise be impassable. There are a number of approaches to the design of fish passes, which are mostly variations on the themes of steps, slopes and lifts.
Flood Risk Management	The activity of understanding the probability and consequences of flooding, and seeking to modify these factors to manage flood risk to people, property and the environment in line with agreed policy objectives.
Floodplain	Area of land bordering a river that is prone to flooding.
Geomorphology	The scientific study of the evolution and configuration of landforms (earth's land surface features).
Glide	A section of stream characterised by moderately shallow water with an even flow that lacks pronounced turbulence. Although most frequently located immediately downstream of pools, glides are occasionally found in long, low gradient streams with stable banks and no major flow obstructions. The typical substrate is gravel and cobbles.
Groyne	A structure projecting in to the river which is designed to constrict water flow and promote scouring and deposition of sediment
Heavily Modified Water bodies	In the Water Framework Directive water bodies that have been physically altered to fulfil important 'uses' such as flood and coastal risk management are designated as Heavily Modified Waterbodies (HMWBs).  Under the Water Framework Directive these water bodies are set the alternative target of Good Ecological Potential (GEP), which is achieved when all practical GEP Mitigation Measures are in place.
Holt	a resting or breeding site for otters. Often found in the root system of large trees, but can also be constructed using large woody debris.
Hydromorphology	Hydromorphology describes the characteristics of a water body. The hydrological and geomorphological elements and processes of water body systems (i.e. Lakes, Rivers, Transitional Waters and Coasts).
Hydrology	Hydrology is the science of water movement
Invasive non native Species	Many species of plants and animals have been introduced to new countries. Several of these non-native species are invasive and have been causing serious problems to the aquatic and riverine ecology and environment. Problems include detrimental effects on native species, deoxygenation of water causing fish mortalities, blocking of rivers and drainage channels, predation and competition with native species, and in some cases pose health risks to the public or livestock.
Invertebrates	An animal without a skeletal structure.
Land drainage	Limiting the effect of flooding by maintaining surface water and land drainage systems.
Land cover	Land cover is the material that makes up the ground. Land covers include fields, buildings, trees, bare ground, water, etc.
Macroinvertebrates	Organisms that do not have a backbone and are visible without a microscope.
Macrophytes	Large vascular aquatic plants that grow in shallow water along the shorelines of lakes or in the slow-moving reaches of river
Maintenance	Work that sustains the desired condition and intended performance of an asset
Managed realignment	The deliberate removal or breaching of existing seawalls or embankments in order to allow the waters of adjacent coasts or estuaries to inundate the land behind.
Meander	A meander is a bend in a watercourse formed as water erodes the outer bank and deposits the eroded sediments on the inside of the bank.
Mean discharge category	The average discharge of the river over the period of a year
Mean annual discharge (m3/s)	The average discharge of the river over the period of a year
Mitigation of a pressure	The pressure (in DPSIR terms) that was (one of the) reason(s) for starting this project.
Modified water body	where it has been significantly changed to suit a specific purpose such as re-alignment for navigation.
Morphology	The form and structure of the land surface (of relevance being formed by fluvial, coastal or estuarine processes).
Natura 2000 sites	Protected Areas established for the protection of habitats or species under the Birds Directive (79/409/European Economic Commission) (Special Protection Areas) and the Habitats Directive (92/43/European Economic Commission)(Special Areas of Conservation).
Pathways	Route that enables a hazard to propagate from a s ‘source’ to a ‘receptor’, as in the ‘source-pathway-receptor’ concept. A pathway must exist in order for a hazard to be realised. Pathways can be constrained in order to mitigate the risks
Phytobenthos	The plants that live on the bed of the sea, lake or river
Phytoplankton	The photosynthetic or plant constituent of plankton
Physio-chemical	relating to both physical and chemical properties, changes, and reactions.
Planform	The planform is the view of the river channel from above. Rivers are traditionally divided into a number of different planforms such as straight, meandering and braided planforms. For a diagram see: http://www.fgmorph.com/fg_4_17.php
Poaching	River bank damage caused by the hooves of livestock which results in the loss of vegetation and soil erosion.
Pollarding	similar to coppicing, except that the tree is cut at approximately head height to prevent damage by grazing animals. Typically done to manage willows. Trees managed in this way are known as pollards.
Pool	a deep section of stream bed with very little surface flow, typically located at the outside of a bend.
Protected species	Plants and animals that have been designated as requiring special protection under legislation.
Revetment	Works to protect the bed or banks of a channel against erosion.
Riffle	A length of stream with a steep gravel, pebble and/or cobble dominated bed, a fast flow and a broken water surface, where the water flows swiftly over the completely or partially submerged substrate.
Riparian	Along the banks of a watercourse. Riparian zones support riparian vegetation and are of environmental importance, providing diverse habitats and supporting a range of ecological communities
River Basin	A river basin is the area of land from which all surface run-off and spring water flows through a sequence of streams, lakes and rivers into the sea at a single river mouth, estuary or delta. It comprises one or more individual catchments.
River Basin District	A river basin or several river basins, together with associated coastal waters. This definition is used as a description within the Water Framework Directive.
River Corridor	The continuous area of river, riverbanks and immediately adjacent land alongside a river and its tributaries
Run	Differs from a riffle in that, although the water surface is broken, the water depth is typically greater and the slope of the bed is less.
Scour	Erosion of the bed or banks of a watercourse by the action of moving water.
Sediment	Material ranging from clay to gravel (or even larger) that is transported in flowing water and that settles or tends to settle in areas where the flow slows down
Sedimentation	The deposition of sediment in the bed of a channel or within a hydraulic structure
Shoal	Sedimentation within or extending into a stream or other water body, typically composed of sand, silt and/or gravels.
Sinuous	Sinuosity is a measure of deviation of a path between two points from the shortest possible path. A river that meanders is not taking the shortest path downstream and it therefore sinuous.
Site designation
Sluice	An artificial channel for conducting water, with a valve or gate to regulate the flow
Species Richness	The number of different species in an area.
Spiling	The use of thin branches to create a woven ‘fence’ that protects the bank from erosion.
Step-pool	See page: Step-pool
Substrate	The material (e.g. rocks, sand, gravel) that forms the bed of a river or estuary.
Subtidal	Continuously submerged areas of coastal areas
Sustainability	The concept of development that meets the needs of the present without compromising the ability of future generations to meet their own needs
Taxonomic composition	The number and arrangement of distinct species that are found in an assemblage
Tidal	The bottom of the river will be subject to tidal movements in the water level, however the river is still fresh water and has not become an estuary.
Toe (of the riverbank):	Where the riverbed meets the bank.
Unit stream power	This is the rate of energy dissipation against the bed and banks of a river per unit downstream length. You need values for the channel width, mean discharge and channel gradient, to calculate this value.
Water body	Under the Water Framework Directive this is a manageable unit of surface water, being the whole (or part) of a stream, river or canal, lake or reservoir, transitional water (estuary) or stretch of coastal water.
Water body codes	This unique code is given to each water body as part of delivering the Water Framework Directive
Water Quality	The physical, chemical and biological characteristics of water
Weir	A low dam built across a river to raise its water level or divert its flow

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