Afflux: the rise in water level on the upstream side of a constriction in a stream or channel caused by that constriction.


AHD: Australian Height Datum is the datum level to which reduce survey levels are based upon. Generally referred to as the level above the average sea level.


Allowable Site Discharge: the volume of fluid per unit of time flowing along a pipe or channel as allowed by the most restrictive point within the site.


Backwater: the part of a stream where the water level is kept above normal due to some controlling influence downstream.


Biological Integrity: a natural, self regulating ecosystem.


Bushland: land on which there is vegetation which is either a remainder of the natural vegetation of the land or, if altered, is still representative of the structure and floristics of the natural vegetation.


Catchment: an area of land from which all run-off water flows to a low point (river. creek. harbour, etc.).


Conservation: Use, management and protection of resources so that they are not degraded, depleted or wasted and are available on a sustainable basis for present and future generations.


Consolidated Stormwater Flows: Where several sources of stormwater flow are funneled into the same path. and the volume and flow rate is increased.


Constructed Wetland: shallow water body containing aquatic plants installed to receive and treat contaminated stormwater run-off.


Council's stormwater system: This refers to the system of pipes, channels and overland flow paths which drain water run-off (stormwater), not including those on private property. The system is designed to discharge the water into receiving waters.


Detention systems: are holding storages which temporarily store stormwater to control and reduce downstream flow rates. They are designed to retard stormwater during intense rainfall and to empty once the peak of the storm has passed.


Developer: Any person or organisation who carry out development of land.


Development: includes the erection of any building. the subdivision of land and the carrying out of any work, and the use of the land or building or work thereon for a purpose which is different from the purpose for which the land or building or work was last being used.


Drainage Easements: common law rights attached to land whereby another parcel of land has the right to use part or all of the land for the purpose of draining water.


Drainage Reserves: lands vested in Council and reserved for drainage purposes.


Erosion Control Devices: are measures to assist in minimising erosion and sedimentation at a site, and include catch drains. diversion drains. banks and energy dissipaters.


First Flush: the entire run-off received at a downstream location up to the time when the whole catchment is contributing, this is generally the 3 monthly ARI event.


First Flush Device: a device attached to a rainwater tank or downpipe to divert the initial runoff captured (20mm) away from the tank to reduce contaminants entering the tank.


Floodplain: relatively level part of a river valley, adjacent to a river or creek channel formed from sediments deposited by the river during periods of flooding.


Flood Standard is the higher water surface level generated for:


1. The 100 year event with subsurface drainage systems operating; and


2. The five (5) year event with subsurface systems fully blocked.


Floodways: the many controlled and uncontrolled routes taken by stormwater in the event of blockage of the underground system or its capacity being exceeded. Land inundated by the flood standard.


Footpath Converters: a structure that directs stormwater from drainage pipe systems into the kerb and gutter (also referred to as a Converter Pit).


Freeboard: the height between water level and the underside of a structure or top of an embankment/channel wall. Generally being 300mm, or 500mm in higher risk areas.


Gross Pollutant Trap (GPT): is a structure which acts as the initial water pollution control measure typically located on the trunk drainage system. They act to intercept and retain coarse sediment, trash and debris.


Impervious: surfaces that do not allow water to penetrate, such as roof, driveways, paths, gravel beds, stepping stones, paving etc...


Impervious Footprint is the outline of the impervious area (this includes driveways. tennis courts, swimming pools, houses, etc.) on a land parcel.


Inter-allotment Drainage: common stormwater drainage system that serves one or more private properties.


Non perennial: intermittent running water throughout the year or years.


Nutrients: Compounds required for growth by plants and other organisms present in the soil. Major plant nutrients are phosphorus and nitrogen.


Orifice: An opening sized up to restrict the flow to a desired rate, in order to reduce the runoff onto public property. Generally a metal plate with a hole varying in diameter (typically 25mm -300mm) placed on the wall of a control pit, over the outlet pipe.


Perennial: Continuous running water throughout the year, or many years, including natural springs


Pervious: surfaces that allow water to soak in, generally turfed areas and landscaped beds.


PMF: Probable Maximum Flood, if the atmosphere reached its saturation point.


Permitted Site Discharge: the rate of discharge determined from the developed surface area of a property and a multiplying factor for the suburb.


Principal Certifying Authority: the Principal Certifying Authority appointed under Section 109E of the Environmental Planning and Assessment Amendment Act 1997.


Property Drainage: the stormwater drainage pipe system that lies within private property and carries only run-off from private property.


Public Reserve: land zoned or reserved for public open space purposes.


Restriction as to User: a restrictive covenant on the transfer of land and is a binding promise to restrict the use of the land or some part of it in a specified manner, such as a Positive Covenant or Deed of Charge.


Riparian Zone: consists of 5 metres either side from the top of the bank of a non-perennial watercourse. or 20 metres either side from the top of the bank of a perennial watercourse, or within the 100 year flood plain, whichever is greater.


Sedimentation Basins: permanent structures located to receive and treat all sediment-Iaden run-off.


Sediment Control Devices: devices to remove sediment from run-off before it leaves the site and include temporary measures such as straw bale barriers. sediment/geo-textile fabric fences and semi-permanent measures such as sediment traps and sedimentation basins.


Sediment Traps: structures located on construction sites to receive contaminated run-off from disturbed areas and retain sediment.


Standard Junction Pit: a structure used in the drainage system to assist with changes in pipe slope or alignment and includes a sealed lid at ground level for inspection.


Street or Secondary Drainage System: the smaller feeder pipe system along streets with pipes generally smaller than 600 mm diameter.


Stormwater: Rain water which runs off land, frequently carrying various forms of pollution, such as rubbish, animal droppings and dissolved chemicals. This untreated water is carried in stormwater channels and discharged directly into creeks, rivers, the harbour and the ocean. Stormwater includes run-off from rainfall, spring, soakage and seepage.


Stormwater Detention: Temporary storage of stormwater, with a controlled release into the drainage system.


Stormwater Drainage Systems: include:


1 Roof and property drainage. including subsoil drainage. detention and retention systems;


2 Street drainage. including both surface open channel and piped systems;


3 Trunk drainage generally located on land reserved for drainage purposes or within easements; and


4 Receiving waters. They may be:


i. Natural depressions. watercourses. creeks and rivers;


ii. Excavated earth and constructed open channels; and


iii. underground systems with pipes. culverts, pits, inlets, outlets. and energy dissipation structures.


Stormwater Quality Control Structures: devices designed to improve the quality of the stormwater which passes through it.


Stormwater Retention: Retaining and storing water for later use on-site. Commonly known as Rainwater Tanks for Basix Compliance.


Stormwater system: The system of pipes, overland flow paths, creeks, canals and other channels used to carry stormwater to bodies of water, such as rivers or oceans.


Subsoil cut-off drains: a perforated field drain laid below ground surface and covered with granular material to intercept ground water to protect structures.


Total Catchment Management: The coordinated and sustainable use of land, water. vegetation and other natural resources on a water catchment basis so as to balance resource utilisation and conservation.


Trunk drainage: the stormwater drainage system that links property, inter-allotment and street drainage with the receiving waters and is greater than 600 mm in diameter.


Unit Development: A building or group of buildings containing two or more units occupied or used or so designed. constructed or adapted as to be capable of being occupied or used as a separate domicile and includes a group dwelling but does not include a dwelling house.


Waste Water: Excess or used water.


Watercourse: any natural or artificial waterway area, whether perennial or intermittent, used to convey flow including a creek, stream or river, any constructed waterway, channel or canal.


Water Re-use: The use of water more than once, following treatment of waste water- to an appropriate quality standard and delivery to the point of use.


Wet Retention Systems: similar to detention systems. but retain some or all of the run-off from a site detaining sediment and improving the quality of run-off.