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| Glossary ยป A |
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GlossaryThis glossary is copied from the Stormwater Manual of Western Australia Chapter 11: Further Information. References are available from this chapter. A B C D E F G H I J K L M N O P Q R S T U V W X Y Z AAdaptive environmental management: A type of environmental management where the approach to managing water resources in urban areas will evolve over time as new ideas, information, drivers for change and technologies emerge. Adsorption: The adhesion of a substance to the surface of a solid or liquid; often used to extract contaminants by causing them to be attached to adsorbents such as activated carbon or silica gel. Hydrophobic or water repulsing adsorbents are used to extract oil from waterways when oil spills occur. Heavy metals such as zinc and lead and nutrients such as phosphorus often adsorb onto sediment. Aeration: The injection of air through diffusers into water bodies, or rapid mixing (e.g. via riffles) of the surface of water bodies to promote transfer of atmospheric air into the water column. A treatment process adopted in situations of high loading of oxygen demanding substances. (ARMCANZ & ANZECC 2000.) Aerobic or oxic zone: An environment in which there is free oxygen (ARMCANZ & ANZECC 2000). Anaerobic or anoxic zone: An environment devoid of oxygen (ARMCANZ & ANZECC 2000). Aquifer: A geological formation or group of formations capable of receiving, storing and transmitting significant quantities of water (Water and Rivers Commission 2000a). Armouring or stabilisation: The use of rock, geotextile and/or vegetation to bind the soil forming the bank or bed of channels such as to resist erosion by elevated flow velocities (ARMCANZ & ANZECC 2000). Atmospheric deposition: Contaminants accumulating across urban surfaces as a result of deposition of fine airborne solids (ARMCANZ & ANZECC 2000). At-source controls: Non-structural or structural best management practices implemented at the site where stormwater runoff is created, to minimise the generation of excessive stormwater runoff and/or pollution of stormwater. Attenuation: The reduction in the magnitude of flows, concentrations or loads of contaminants (ARMCANZ & ANZECC 2000). Average recurrence interval (ARI): ARI is defined as the average, or expected, value of the periods between exceedances of a given rainfall total accumulated over a given duration. When designing urban stormwater management systems, ARI events can be grouped into:
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