Glossary E – H

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Ebb Tide

A falling tide - the phase of the tide between high water and the succeeding low water.

Ecosystem Health

Ecosystem health is a new approach used in environmental management [1]. A healthy ecosystem has three main features: vigor, resilience and organization [2]. It is an environment that maintains biodiversity, is relatively stable and is resilient to change [3]. In the ANZECC/ARMCANZ guidelines [6] ecosystem 'health' "refers to the condition and functioning of an ecosystem in comparison to conditions and function that are thought to be normal" [4]. One of the principles to emerge from the United Nation Conference on Economic Development and Environment, was the desire to find the means to protect the health and integrity of the Earth's ecosystems [5].

  1. Costanza, R., B. Norton, B. Haskell (eds.) 1992. Ecosystem Health: New Goals for Environmental Management. Island Press, Washington, D.C.
  2. Mageau, M.T., R. Costanza and R.E. Ulanowicz 1995. The development and initial testing of a quantitative assessment of ecosystem health. Ecosystem Health 1(4):201-213.
  3. Rapport, D.J., C. Gaudet and P. Calow (eds.) 1995. Evaluating and Monitoring the Health of Large-Scale Ecosystems. Springer-Verlag, Heidelberg.
  4. page 3-20 in the ANZECC/ARMCANZ (October 2000) Australian Guidelines for Fresh and Marine Water Quality.
  5. United Nations 1992. Adoption of Agreements on Environment and Development: the Rio Declaration on Environment and Development. UNEPA/CONF.151/5/Rev. 1. 13 June 1992
  6. ANZECC/ARMCANZ (October 2000) Australian Guidelines for Fresh and Marine Water Quality.

Ecosystem Integrity

There are several definitions of ecosystem integrity, and they all reflect the capability of a system to support services of value to humans [1].

  • "the maintenance of the community structure and function characteristic of a particular locale deemed satisfactory to society" [2].
  • "the capability of supporting and maintaining a balanced, integrated, adaptive community of organisms having species composition, diversity, and functional organisation comparable to that of natural habitats of the region." [3].
  • "it is much more useful to characterize in detail the functional and structural aspects of ecosystems to provide a conceptual framework for assessing the impact of human activity on biological systems and to identify practical consequences stemming from this framework." [4].
  • "integrity reflects the ability of ecosystems to sustain services to humans and the identification of those services can best emerge from multisector partnerships, in which all stakeholders seek agreement on the uses to which an ecosystem will be put, recognizing the linkages with other ecosystems." [1].
  1. De Leo, G. and Levin, S,. 1997. The multifaceted aspects of ecosystem integrity, Conservation Ecology [online] 1(1)3.
  2. Cairns, J. 1977. Quantification of biological integrity, pp. 171-187 in R.K. Ballentine and L.J. Guarraia (Eds.), The integrity of Water, U.S. Environmental Protection Agency, Office of Water and Hazardous Materials, Washington, D.C., U.S.A.
  3. Karr, J.R. and Dudley, D.R. 1981. Ecological perspective on water quality goals. Environmental Management 5, 55-68.
  4. Noss (1995a) in De Leo, G. and Levin, S,. 1997. The multifaceted aspects of ecosystem integrity, Conservation Ecology [online] 1(1)3.

Ecosystem/mapping unit

This is broadly equivalent to the extent and resolution of the "Geomorphological Units", that is, typically 100 km2 in extent.

Electrode Potential

The electrode potential (pE) is the negative base-10 log of electron activity (e-):

pE = -log(e-)

It is a dimensionless quantity that measures the tendency of a chemical system to exchange electrons or undergo redox reactions. It is negative in a reducing medium and positive in an oxidizing medium. pE and Eh are related:

Eh = 2.303RT/F * pE

F is Faraday's Constant (96.5 kJ V-1)
R is the gas constant (8.3 x 10-3 kJ K-1 mole-1); and
T is temperature measured in Kelvin (K)

El Nino and La Nina - Southern Oscillation (ENSO)

The El Nino - Southern Oscillation (ENSO) is a global climatic phenomenon marked by see-saw shifts in air pressure between the Indo-Australian and eastern regions of the Tropical Pacific. El Nino and La Nina refer to extreme phases in the 2-7 year cycle. During the warm 'El Nino' phase, the Australian seaboard cools, SE trade winds slacken and extended periods of drought are experienced in Australia. In the cool 'La Nina' phase, the seas around Australia warm, the SE trade winds intensify, and widespread rain and flooding occur in Australia. The strength and phase of ENSO is measure by the Southern Oscillation Index (SOI). Consult the Bureau of Meteorology web site for a more comprehensive discussion of ENSO.


A coastal indentation (or bedrock valley) which has been submerged by rising sea-level, and has not been significantly infilled by sediment. Also: Drowned River Valley. More information.

Energy (hydraulic)

Energy or intensity of water turbulence or movement, current speed.

Environmental flows

Environmental flows (aka environmental water) refers to the amount (and timing) of freshwater that is required to maintain the health of aquatic ecosystems [2]. More information

Environmental Management Framework/System

A management approach which includes organizational structure, responsibilities , planning activities, practices, procedures, resources and processes for developing, implementing, achieving, reviewing and maintaining a management goal. More information

Environmental Management Goals

Environmental objectives arising from policies that governments or organization set out to achieve, and which ideally may be quantified.More information

Environmental Values

Environmental Values are values or uses of a system that we wish to protect [1]."They outline values and beneficial uses of the environment that are important for healthy ecosystems, public benefit, industry and health that require protection from the effects of pollution and waste discharges" [1]. Some examples of environmental values that may require protection are:

  • aesthetics and recreation;
  • drinking water;
  • aquatic ecosystems;
  • cultural and spiritual values;
  • industrial water; and
  • primary industries [1].
  1. Page 6 in the Department of Environment, Water, Heritage and the Arts. Water Quality Targets: A Handbook, Commonwealth of Australia, 2002 (see also Water Quality Targets OnLine).


The Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act) protects Australian biodiversity, integrates management of important natural and cultural places and streamlines the national environmental assessment and approvals process. More information.


Animals that live on the sediment but do not burrow into it. More information.


Breakdown of material (e.g. rock) due to chemical, physical or biological processes.


The seaward limit of a drowned valley which receives sediment from both river and marine sources and contains geomorphic and sedimentary facies influenced by tide, wave and river processes [1].

  1. Boyd R, Dalrymple R, Zaitlin BA. Classification of clastic coastal depositional environments. Sedimentary Geology 1992;80:139-50.


Organisms able to tolerate a wide range of salinity.


Eutrophication is "an increase in the rate of supply of organic matter to an ecosystem" [1].

  1. Nixon, S.W. 1995. Coastal marine eutrophication: A definition, social causes, and future concerns. Ophelia 41, 199-219.
More information


Pertaining to an environment of restricted circulation and stagnant or anaerobic conditions, such as a fjord or a nearly isolated or silled basin with toxic bottom waters. Also, pertaining to the material (such as black organic sediments and hydrogen-sulfide muds) deposited in such an environment or basin, and to the process of deposition of such material (as in the Black Sea). Pertaining to a rock facies that includes black shales and graphitic sediments of various kinds. Etymol: Greek euxenos, hospitable.


Comprehensive analyses to determine how well, and in what ways the policies, strategies and programs are working.More information

Exclusive Economic Zone

The Exclusive Economic Zone is an area beyond and adjacent to the territorial sea. The outer limit of the exclusive economic zone cannot exceed 200 nautical miles from the baseline from which the breadth of the territorial sea is measured. More information


The total area under consideration. This term is often used in three ways:

  • Observational extent: The area covered by a given sensor
  • Representational extent: The area covered by a map/data layer
  • Management extent: The area of interest to a particular management body (e.g. all of Australia’s coasts, or all the waters in a particular NRM region).

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In the context of coastal landforms, their ‘fabric’ refers to what they are composed of, e.g., rock, sand, mud, etc.


Sum total of features that reflect the specific environmental conditions under which a given sediment was formed or deposited. The features may be lithologic, sedimentological, or faunal.

Facies, biological

An identifiable biological and physical unit within a secondary biotope, defined by a biological indicator, or suite of indicator species [1].

  1. Butler, A., P. Harris, et al. (2001). An Interim Bioregionalisation for the continental slope and deeper waters of the South-East Marine Region of Australia., National Oceans Office.


The commonly used abbreviation for Framework for the Assessment of River and Wetland Health.

Fine Sediment

A sediment comprising fine-grained material such as mud or clay particles.


Flocculation in coastal waterways is a process in which particles of clay and organic matter stick together, through chemical interactions with divalent calcium and magnesium ions, to form larger flake-like particles (flocs or floccules) that may come out of solution. Flocculation influences the transport of fine-grained sediment, and enhances its deposition rate [1]. Because particles belonging to various size classes can form flocs, the sediment that is deposited is often poorly sorted [2]. Flocculation contributes to the formation of a turbidity maximum in coastal waterways (Figure 1), and can also cause patches of nutrients to form on the seabed, providing food for micro-organisms.

Conceptual illustration of the flocculation process

Figure 1. Conceptual illustration of the flocculation process (modified from illustration in [4])

  1. Shanks, A. L. and Trent, J. D. (1980). Marine snow: sinking rates and potential role in vertical flux. Deep-Sea Res. Pt. A 27, 137-43.
  2. Kranck, K. and Milligan, T. G. (1983). Grain size distributions of inorganic suspended river sediment. In: Degens, E. T., Kempe, S. and Soliman, H. (Eds) Transport of Carbon and Minerals in Major World Rivers, Pt. 2. Mitt. Geol.-Paläont. Inst. Univ. Hamburg, SCOPE/UNEP Sonderbd. 55, pp. 525-34.
  3. Eisma, D. and Cadee, G.C. (2002). Particulate Matter in Estuaries, In SCOPE 42 - Biogeochemistry of Major World Rivers, accessed November.
  4. Webster, I.T., Ford, P.W., Robson, B., Margvelashvili, N., and Parslow, J.S. 2003. Conceptual Models of the Hydrodynamics, Fine-Sediment Dynamics, Biogeochemistry, and Primary Production in the Fitzroy Estuary. Cooperative Research Centre for Coastal Zone, Estuary & Waterway Management Technical Report #8.

Flood tide

A rising tide - the phase of the tide between low water and the next high tide.


Exchange of water between an estuary or coastal waterway and the ocean.


Pertaining to a river or freshwater source

Framework for a National Cooperative Approach to Integrated Coastal Zone Management

The Framework for a National Cooperative Approach to Integrated Coastal Zone Management (endorsed in October 2003) addresses both development and conservation challenges for coastal Australia that are of national scale and scope. More

Framework for the Assessment of River and Wetland Health (FARWH)

The national Framework for the Assessment of River and Wetland Health developed by The National Water Commission (the Commission) under the National Water Initiative (NWI) as part of the Australian Water Resources 2005 project.

Framework Component

A major element of the assessment framework, such as Audience, Purpose, Scope, Mapping Protocol, Classification Systems (Typology and Trajectory), Vulnerability Assessment, Risk Assessment, Indices (Themes) and Indicators, Reporting (Report Carding)

Framework Structure

The organising principles and overall approach underpinning the framework. For the NEECAF, it consists of the flexible, layered First, Second and Third Passes.


Increased freshwater flow following a recent rain, or artificial floods intended to benefit the aquatic environment (particularly fisheries) in which the discharge is over and above the basic compensation flow.


Water, typically derived from inland or rainfall, with less than 0.03% ionic content.


The function of an estuary is how it acquires the materials and energy needed, processes its waste products, and interacts with adjacent waters and the surrounding landscape.

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The study of the nature and history of landforms and the processes which create them.

Global warming

Global warming is the impact on the climate from the additional heat retained due to the increased amounts of carbon dioxide and other greenhouse gases that humans have released into the earths atmosphere since the industrial revolution.More information

Grab Sampler

A grab sampler is a device that grabs a sample of the topmost layers of the seabed by bringing two steel clamshells together and cutting a bite from the soil. Grab sampling is a common technique used to examine the surface sediment (from 0 to about 10-15 cm deep). Different grab samplers are used depending upon the type of substrate being sampled (soft or hard) and the size of the sample required.

Deployment of a grab, similar to a SHIPEK type grab sample from Keppel Bay

Figure 1 (a). Deployment of a grab, similar to a SHIPEK type; (b) grab sample from Keppel Bay.


grains with diameters between 2 and 4 mm

Gravity drop and piston corers

Gravity corers provide a rapid means of obtaining a continuous core sample in water depths down to several thousand metres. Depending upon their deployment and operating systems, gravity corers can be deployed from a wide range of vessels. A gravity corer consists of a steel tube in which is inserted a plastic liner to retain the core sample. The penetrating end of the tube is fitted with a cutter and a concave spring-steel core-catcher to retain the sample when the corer is retracted from the soil and recovered to the ship. One of the simplest geotechnical devices, the impetus of gravity acting on the heavy, freefalling device is the motive force that drives the corer into the soil.

Greenhouse effect (enhanced)

The enhanced greenhouse effect is the impact on the climate from the additional heat retained due to the increased amounts of carbon dioxide and other greenhouse gases that humans have released into the earths atmosphere since the industrial revolution. More information

Gully Erosion

A gully is a narrow channel eroded into a hill-slope when surface water flow increases in response to clearing and overuse of the land. Other factors that play a role in gully initiation are the type of land use, geology, rainfall, soil texture, slope, hill-slope length and seasonal climatic extremes [1]. Gully erosion is a major land degradation process. Erosion from gullies and streambanks removes valuable soil and can generate as much as 90% of the sediment yield from a catchment [1,2]. The sediment is a major source of turbidity and particulate nutrients in some rivers and coastal waterways [1].

Photo of Inverary Gully in Bungonia, NSW, is an extreme example of gully erosion, in this case exacerbated by highly dispersible soils.

Photo 1. Inverary Gully (a.k.a The Gully From Hell) in Bungonia, NSW, is an extreme example of gully erosion, in this case exacerbated by highly dispersible soils. (photo courtesy of Upper Shoalhaven Landcare Council)

  1. Hughes, A.O., Prosser, I.P., Stevenson, J., Scott, A., Lu, H., Gallant, J., and C. Moran. 2001. Gully erosion mapping for the National Land and Water Resources Audit. CSIRO Land and Water Canberra, Technical Report 26/01.
  2. Olley, J.M., Murray, A.S.. Mackenzie, D.M., Edwards, K. 1983. Identifying sediment sources in a gullied catchment using natural and anthropgenic radioactivity. Water Resources Research 29, 1037-1043.


Mineral formed by evaporation, with the molecular structure: CaSO4.2H2O. More information

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The word habitat is Latin for "it inhabits", and refers to the environment or place where species live. More information

Habitat, geomorphic

In the coastal context, geomorphic habitats are landforms ("geo" = land; morph = shape) or sedimentary environments whose shape and position in the landscape is governed by the effect of physical and biological forces on sediment. More information


Mineral formed by evaporation, composed of NaCl. More information


Salt-tolerant vegetation.


The landward or upstream section of an estuary or coastal waterway

Heavy metals

Heavy metals comprise the block of metals belonging to Groups 3 to 16 of the periodic table, in periods of 4 or greater. The terms 'heavy metals', 'toxic metals', 'trace metals', 'trace elements' and 'trace constituents' are often used interchangeably in the literature, in reference to metals in aquatic systems. More information

Hermit crabs

Hermit crabs are relatively small crustaceans that, for the most part, require the use of empty gastropod shells in order to protect their soft and vulnerable abdomens. More information

High water mark

High water mark is a term generally used to describe the high tide line. Under Common Law this term is usually considered to be Mean High Water. Some Australian States have amended this Common Law understanding via legislation. For example, Queensland has legislation defining the High Water Mark as Mean High Water Springs.


The most recent geologic epoch of the Quaternary period of geologic time, extending from about 10,000 years ago to the present. The Holocene is the latest epoch of the Quaternary period.

Humic Acid Waters

Most organic matter in natural waters and soils consists of humic substances: the mostly stable (or refractory) component that remains after the incomplete decomposition of plants and bacteria. There are three products that result when humic substances are extracted with an aqueous base. These include:

  1. the non-extractable material called 'humin';
  2. 'fulvic acids'; and
  3. 'humic acids'.

The humic and and fulvic acids can form complexes with metals. At very low pH (less than 3) the humic acid-metal complexes may precipitate.


Water with a high concentration of salt, e.g. greater than the ionic content of seawater.


Coastal areas with a high mean tidal range, e.g. equal to - or greater than 6 metres.


Hypoxia occurs when dissolved oxygen concentrations are < 2.0 mg L-1. More information


Hysteresis occurs when the response of an estuary, as a driving variable intensifies, is different to the trajectory as the driving variable subsides (Figure 1). An example is the response of the estuary to increasing loads of nutrients from the catchment. At low loads, seagrass dominates the flora, but as loads increase, phytoplankton gradually increase [1,2]. At a critical load, the phytoplankton concentration increases sufficiently that the seagrass do not have enough light to grow. The seagrass population collapses allowing the phytoplankton to grow to even higher concentrations. Even if the load is reduced to below the critical load, the phytoplankton concentrations remain high enough that seagrass do not return. It is only when loads are reduced considerably below the critical load that seagrass growth returns. This is called hysteresis.

Another important cause of hysteresis in estuaries is the termination of nitrification (hence denitrification) during progressive eutrophication, giving rise to large internal loads of ammonia [3].

Such hysteresis effects and 'alternative stable states' are also observed in shallow lakes [4-7].

Hysteresis in terms of nutrients and turbidity.

Figure 1. Hysteresis in terms of nutrients and turbidity. Submerged aquatic vegetation (including seagrasses) disappears when turbidity exceeds a critical level, and subsequent changes in turbidity with nutrient concentrations follows a different trajectory (modified after Scheffer 2001 [4].

  1. Borum, J. and Sand-Jensen, K. 1996. Is total primary production in shallow coastal marine waters stimulated by nutrient loading? Oikos 76, 406-410.
  2. Murray, A.G. and Parslow, J.S. 1999. Modelling of nutrient impacts in Port Phillip Bay - a semi-enclosed marine Australian ecosystem. Marine and Freshwater Research 50, 597-611.
  3. Harris, G.P. 1999. Comparison of the biogeochemistry of lakes and estuaries: ecosystem processes, functional groups, hysteresis effects and interactions between macro- and microbiology. Marine and Freshwater Research 50, 791-811.
  4. Scheffer, M., Hosper, S.H., Meijer, M-L., Moss, B. and Jeppensen, E. 1993. Alternative equilibria in shallow lakes. TREE 8(8), 275-279.
  5. Scheffer, M. 2001. Alternative attractors of shallow lakes. The Scientific World 1, 254-2634.
  6. Ogden, R. 2000. Modern and historical variation in aquatic macrophyte cover of billabongs associated with catchment development. Regulated Rivers: Research and Management 16, 497-512.
  7. Reid M., Fluin J., Ogden R., Tibby J. and Kershaw P. 2002. Long-term perspectives on human impacts on floodplain-river ecosystems, Murray-Darling Basin, Australia. Verhandlungen der Internationalen Vereinigung für Theoretische und Angewandte Limnologie 28(2), 710-716.


Ralph Ogden, CSIRO Land and Water
Ian Webster, CSIRO Land and Water

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