Terminology

;Adsorption 
;adsorption
:The attachment of gas, vapour or dissolved matter onto the surface of solid materials. 
;Aggregate 
;Aggregates 
;aggregate 
;aggregates
:A broad category of particulate material used in construction, including sand, gravel, crushed stone, slag, recycled concrete and geosynthetic aggregates, and available in various particulate size gradations.
;Antecedent dry period 
;antecedent dry period
;Interevent time 
;interevent time
:The period of time between consecutive storms or rainfall events.
;Aquifer 
;Aquifers 
;aquifer 
;aquifers 
:Layer of rock or soil that holds or transmits water. 
;Arterial road;
;arterial road 
:A road primarily for through traffic. 
;Asphalt 
;asphalt
:A mixture of mineral aggregates bound with bituminous materials, used in the construction and maintenance of paved surfaces. 
;Attenuation 
;attenuation
:Reduction of peak flow and increase of the duration of the flow event. 
;Base flow 
;base flow
:The sustained flow in a channel not from storm runoff, instead arising from groundwater interaction. 
;Basin 
;basin
;Basins 
;basins
:Ground depression acting as a flow control and water treatment structure, that is normally dry. 
;Berm 
;berm
:A compacted earthen wall that diverts runoff or creates shallow ponding of runoff. In some cases, runoff ponds behind the berm and gradually flows through it or is infiltrated.
;Biodegradation 
;biodegradation
:Decomposition of organic matter by micro-organisms and other living things. 
;Biofilter 
;biofilter
;Biofilters 
;biofilters
:A bioretention BMP featuring an impermeable liner and underdrain that prevents infiltration of runoff into the underlying native soil; provides sedimentation and filtration of urban runoff as it passes through the mulch layer, engineered filter media and vegetation root zone.
:A bioretention cell that features an impermeable liner that collects and treats stormwater through sedimentation and filtration only (i.e., no infiltration).
;Bioretention 
;bioretention
:A shallow excavated surface depression containing prepared filter media, mulch, and planted with selected vegetation.
;Bioswale 
;bioswale
;Bioswales 
;bioswales
;Dry swale 
;dry swale
;Dry swales 
;dry swales
:Linear bioretention cell designed to convey, treat and attenuate stormwater runoff. The engineered filter media soil mixture and vegetation slows the runoff water to allow sedimentation, filtration through the root zone, evapotranspiration, and infiltration into the underlying native soil.
;BMP
:Best management practice. State of the art methods or techniques used to manage the quantity and improve the quality of wet weather flow. BMPs include: source, conveyance and end-of-pipe controls. 
;Best Management Practices 
;best management practices
:State of the art methods or techniques used to manage the quantity and improve the quality of wet weather flow. BMPs include Source, Conveyance and End-Of-Pipe Controls. 
;Catchbasin 
;catchbasin
:Box like underground concrete structure with openings in curb and gutter designed to collect runoff from streets and pavement. 
;Catchment 
;catchment
;Source area 
;source area
:The land draining to a single reference point (usually a structural BMP); similar to a subwatershed, but on a smaller scale. 
;Check dam 
;check dam
;Check dams 
;check dams
:Structures constructed of a non-erosive material, such as suitably sized aggregate, wood, gabions, riprap, or concrete; used to slow runoff water. Can be employed in practices such as bioswales and enhanced grass swales.
;Cistern 
;cistern
;Cisterns 
;cisterns
:Tank used to store rainwater (typically roof runoff) for later use.
;Cleanout
;cleanout
;Cleanouts
;cleanouts
;Clean out
;clean out
;Clean-out
;clean-out
;Clean-Out
;Clean Out
:Cleanouts are "a fitting access in a drainage system or venting system that is installed to provide access for cleaning and inspection and that is provided with a readily replaceable air tight cover" (O.Reg 332/12: Building Code, 2022).
;Compost 
;compost
:Decayed organic material used as a plant fertilizer. Compost helps to support healthy plant growth through the slow release of nutrients and the retention of moisture in the soil. 
;Control structure 
;control structure
:Structure to control the volume or rate of flow of water through or over it.
;Conveyance 
;conveyance
:Movement of water from one location to another. 
;Cultivar 
;cultivar
:A cultivated variety of a plant created by horticultural practice, often closed in large numbers from a similar individual. Cultivar names typically appear after the scientific name of a species, e.g. Prunus virginiana ‘Shubert’.
;CVC
:Credit Valley Conservation
;Depression Storage 
;depression storage
:A technique for incorporating shallow depressed areas into urban landscaped areas for storing and infiltrating runoff. Depression storage areas are small and have limited capacity and limited duration of retention in order to address property owner concerns relating to insects, damage to structures and inconvenience of ponded water on their property.
;Detention 
;detention
:The temporary storage of stormwater to control discharge rates, and allow for sedimentation.
;Drainage time 
;drainage time
;Drawdown time
;drawdown time
:The period between the maximum water level and the minimum level (dry weather or antecedent level).
;Dry pond 
;dry pond
;Infiltration basin 
;infiltration basin
:Depressed storage area, designed to capture flood events. 
;Evaporation 
;evaporation
:Abiotic transfer of water vapour to the atmosphere. 
;Evapotranspiration 
;evapotranspiration
:The combined loss of water to the atmosphere from land and water surfaces by evaporation and from plants by transpiration.
;Enhanced grass swale 
;enhanced grass swale
;Enhanced swale 
;enhanced swale
:Vegetated open channel, with check dams; designed to convey, treat and attenuate stormwater runoff. 
;Environmental Impact Report (EIR)
:The evaluation of the possible effects that may arise from a proposed project on the environment, together consisting of the natural, social and economic aspects.
;Exfiltration 
;exfiltration
:Loss of water from a drainage system as a result of percolation or absorption into the surrounding medium (e.g., the infiltration of water into the native soil through a perforated pipe wall as it is conveyed).
;Filter media 
;filter media
:The engineered soil component of bioretention cell or dry swale designs, typically with a high rate of infiltration and designed to retain contaminants through filtration and adsorption to particles.
;Filtration 
;filtration
:The technique of removing pollutants from runoff as it infiltrates through the soil.
;Fines 
;fines
:Soil particles with a diameter less than 0.050 mm.
;First flush 
;first flush
:Initial pulse of stormwater runoff which picks up the pollutants that have settled on surfaces during the dry period. The first flush contains the highest pollutant concentrations.
;FIT
;FIT work
;FIT Work
;FIT (Forensic Inspection and testing)
:FIT work involves the application of a similar set of inspection and testing indicators as those used in Performance Verification inspections, but focuses on diagnosing suspected problems with the following objectives in mind: (1) Confirm whether or not problems with BMP function exist; (2) Identify the causes of confirmed problems; (3) Determine corrective actions needed. 
;Forebay
;forebay
:A pretreatment basin at the inlet of a practice that allow settling out of sediment and associated contaminants suspended in urban runoff.
;Flow path length
:The minimum linear distance of water flow across a surface.
;Fluvial geomorphology
;fluvial geomorphology
:The study of the processes responsible for the shape and form, or morphology, of watercourses; describes the processes whereby sediment (e.g., silt, sand, gravel) and water are transported from the headwaters of a watershed to its mouth.
;Fused grid
;fused grid
:A hybrid neighbourhood and district layout model that combines the geometries of inner city grid road patterns with the loop and cul-de-sac road patterns of conventional suburbs.
;General Use Designation
;General Use Level Designation
;GULD
:The General Use Level Designation (GULD) is provided by the Washington Department of Technology to all technologies that meet the performance goals set out in the TAPE protocol. Performance requirements include 80% TSS removal for influent concentrations from 100-200 mg/L and effluent concentrations <20 mg/L for influent concentrations from 20 to 100 mg/L. See Table 2 in the TAPE protocol for more information.
;Geotextile
;geotextile
:Filter fabric that is installed to separate dissimilar soils and provide runoff filtration and contaminant removal benefits while maintaining a suitable rate of flow; may be used to prevent fine-textured soil from entering a coarse granular bed, or to prevent coarse granular from being compressed into underlying finer-textured soils.
;Granular
;granular
:Gravel, or crushed stone of various size gradations (i.e., diameter), used in construction; void forming material used as bedding and runoff storage reservoirs and underdrains in stormwater infiltration practices.
;Grass swales
;Grass swale
;grass swales
;grass swale
:Vegetated, open channels designed to convey, treat and attenuate runoff. Design variations range from simple grass channels, which are designed primarily for conveyance to more complex treatment and volume reduction designs like enhanced grass swales, and dry swales or bioswales.
;Gravel diaphragm
;gravel diaphragm
:A level spreading device placed at a runoff discharge location, perpendicular to flow, to maintain sheet flow and distribute runoff as evenly as possible across a pervious area or stormwater infiltration practice. A gravel diaphragm acts as a pretreatment device, settling out suspended sediments before they reach the practice.
;Green roof
;green roof
:A thin layer of vegetation and growing medium installed on top of a conventional flat or sloped roof, also referred to as living roofs or rooftop gardens.
;GI
:Green infrastructure
;Green infrastructure
;green infrastructure
:Natural vegetation and vegetative technologies in urban settings such as: urban forests; green roofs; green walls; green spaces; rain gardens; bioswales; community gardens; natural and engineered wetlands and stormwater management ponds; and porous pavement systems. These systems are designed to provide multiple benefits, such as moderate temperatures, clean air and water, and improve aesthetics.
;Groundwater discharge
;groundwater discharge
:The outflow of groundwater to a well, spring, wetland or watercourse.
;Groundwater recharge
;groundwater recharge
:The inflow of surface water to a groundwater reservoir or aquifer.
;Hydraulic conductivity
;hydraulic conductivity
:A parameter that describes the capability of a medium to transmit water.
;Hydrologic cycle
;hydrologic cycle 
:The circulation of water from the atmosphere to the earth and back, through precipitation, runoff, infiltration, groundwater flow and evapotranspiration.
;Hydrologic regime
;hydrologic regime
:The characteristic pattern of precipitation, runoff, infiltration and evaporation affecting the hydrology of a system.
;Hydrologic soil groups
;hydrologic soil groups
:A soil classification system based on the ability to convey and store water; divided into four groups: A,B,C,D
;Impervious
;impervious
:A hard surface area (e.g., road, parking area or rooftop) that prevents or retards the infiltration of water into the soil.
;Infiltration
;infiltration
:Penetration of water through the ground surface.
;Inline
;inline
:Refers to a system that accepts all of the flow from a drainage area and conveys larger event flows through an overflow outlet.
;Introduced species
;introduced species
:Plant species (or non-native species) are those that do not naturally or historically occur in a particular area.
;Interception
;interception
:The interception, storage and eventual evaporation of rainfall from vegetation canopies.
;Invasive plants
;invasive plants
:Typically non-native plants that out-compete native species. These species lack natural predators, grow aggressively and reproduce rapidly and can be problematic in the natural environment. 
;Irreducible concentration
;irreducible concentration
;Irreducible level
;irreducible level
:The pollutant concentration below which further reduction can not be reliably achieved by the treatment technology in question (Schueler, 2000)Schueler, T. 2000. Irreducible Pollutant Concentration Discharged from Stormwater Practices. Technical Note #75, In Watershed Protection Techniques. 2(2), 369-372, Centre for Watershed Protection.
;I/P ratio
:The ratio of the impervious catchment (drainage) area to the pervious (footprint) area of the receiving BMP. 
;LSRCA
:Lake Simcoe Region Conservation Authority
;Landform
;landform
:The natural features of the landscape, dictates flow patterns, runoff velocities and discharge rates.
;Landscape-based approach
;landscape-based approach
:The principle that development form, servicing and stormwater management strategies should be defined by the biophysical, hydrological and ecological attributes of the landscape.
;Loading
;loading
:The net amount of something (e.g. chemical, such as phosphorus), calculated as the product of concentration and volume in a given time. Some BMPs significantly reduce loading of pollutants to the environment by reducing volume more so than concentration. 
;Lot level
;lot level
:The treatment of urban runoff as close to the source area as possible through application of small scale stormwater management practices on individual properties that are linked to downstream conveyance and end-of-pipe practices.
;LID
:Low Impact Development. A stormwater management strategy that seeks to mitigate the impacts of increased urban runoff and stormwater pollution by managing it as close to its source as possible. It comprises a set of site design approaches and small scale stormwater management practices that promote the use of natural systems for infiltration and evapotranspiration, and rainwater harvesting.
;Low impact development
;low impact development
;Low Impact Development
:A stormwater management strategy that seeks to mitigate the impacts of increased urban runoff and stormwater pollution by managing it as close to its source as possible. It comprises a set of site design approaches and small scale stormwater management practices that promote the use of natural systems for infiltration and evapotranspiration, and rainwater harvesting.
;Master Environmental Servicing Plan 
;MESP
:Is a community-scale planning assessment of servicing and environmental considerations for a development project.
;Mulch
;mulch
:a top dressing over vegetation beds that provides suppresses weeds and helps retain soil moisture in bioretention cells, stormwater planters and dry swales. 
;Native plants
;native plants
;Native vegetation
;native vegetation
:Defined as those plants (including grasses, herbaceous species, shrubs, vines and trees) that have historically existed within a particular area. Native plants have co-evolved with the local ecosystems and natural processes.
;Native soil
;native soil
:The natural ground material characteristic of or existing by virtue of geographic origin.
;Offline
;offline
:Refers to a system that when full, stormwater will bypass the practice. Offline systems use flow splitters or bypass channels that only allow the water quality volume to enter the facility. This may be achieved with a pipe, weir, or curb opening sized for the target flow, but in conjunction, create a bypass channel so that higher flows do not pass over the surface of the filter bed.
;Permeable pavement
;permeable pavement
;Permeable paving
;permeable paving
:An alternative practice to traditional impervious pavement, prevents the generation of runoff by allowing precipitation falling on the surface to infiltrate through the surface course into an underlying stone reservoir and, where suitable conditions exist, into the native soil.
;Physiography
;physiography
:The physical features of the land, including topography, morphology and geologic origin. The physical feature of the land has an influence on the surface water movement and the interactions between surface water and groundwater.
;Pollution hot spot
;pollution hot spot
:Areas where certain land uses or activities have the potential to generate highly contaminated runoff (e.g., vehicle fuelling, service or demolition areas, outdoor storage and handling areas for hazardous materials and some heavy industry sites).
;Pollutant load
;pollutant load
;Loading
;loading
:The total mass of a pollutant entering a waterbody over a defined time period.
;Pre-development
;pre-development
:refers to the characteristics and functions of a system prior to urban development.
;Pretreatment
;pretreatment
:Initial capturing and removal of unwanted contaminants, such as debris, sediment, leaves and pollutants, from stormwater before reaching a best management practice; Examples include, settling forebays, vegetated filter strips and gravel diaphragms.
;Rain garden
;rain garden
:A lot level bioretention cell designed to receive and detain, infiltrate and filter runoff, typically used for discharge from downspouts.
;Rainwater harvesting
;rainwater harvesting
:The practice of intercepting, conveying and storing rainwater for future use. Captured rainwater is typically used for outdoor non-potable water uses such as irrigation, or in the building to flush toilets.
;Rational Method
;Rational method
;rational method
:This formula is used to calculate peak rates of runoff when designing drainage LID BMPs in urban area. It is useful in estimating runoff on relatively small areas (roofs, parking lots, medians, road right-of-ways, etc.)
;RWH
:Rainwater harvesting.
;Recharge
;recharge
:The infiltration and movement of surface water into the soil, past the vegetation root zone, to the zone of saturation or water table.
;Riparian
;riparian
:A vegetated ecosystem alongside a waterbody, characteristically have a high water table and are subject to periodic flooding.
;Runoff
;runoff
:Water from rain, snow melt, or irrigation that flows over the land surface.
;Sedimentation
;sedimentation
:Settling-out or deposition of particulate matter suspended in runoff.
;Soakaway
;soakaway
:An excavated area lined with geotextile filter cloth and filled with clean granular stone or other void forming material, that receives runoff and allow it to infiltrate into the native soil; can also be referred to as infiltration galleries, French drains, dry wells or soakaway pits.
;Soil amendment
;soil amendment
:The practice of adding organic material, such as mulch or compost to topsoil to improve fertility, and tilling of the native soils to reverse compaction and restore its water retaining capacity.
;Standing water
;standing water
:Water ponded on the ground surface.
;Stoichiometry
;stoichiometry
:Stoichiometry in the terms of stormwater nutrient ratios is the consequences of mass balance of chemical elements constrained by either biological or ecological factors (i.e. media, sand, vegetation, soils, etc.).
;Stone reservoir
;stone reservoir
;Storage reservoir
;storage reservoir
:An underlying bed filled with aggregate or other void-forming fill material that temporarily stores stormwater before infiltrating into the native soil or being conveyed by an underdrain pipe.
;Stormwater planter
;stormwater planter 
:A vegetated practice that collects and treats stormwater through sedimentation and filtration. Contributions to water cycle/water balance are through evapotranspiration only; no infiltration. 
;Stream channel
;stream channel
:A natural waterway, formed by fluvial processes, that conveys running water.
;TN
:Total nitrogen
;TP
:Total phosphorus
;TRCA
:Toronto and Region Conservation Authority
;TSS
:Total suspended solids
;Time of concentration
;time of concentration
:The time needed for a drop of water to reach the outlet of a catchment from the most remote location within the catchment.
;Treatment train
;treatment train
:A combination of lot level, conveyance, and end-of-pipe stormwater management practices.
;Underdrain
;underdrain
:A perforated pipe used to assist the draining of soils.
;Urbanization
;urbanization 
:The changing of land cover and land uses from rural to urban; the growth of urban settlements.
;Vegetated filter strip
;vegetated filter strip
;filter strip
;Filter strip
;Buffer strip
;buffer strip
:a gently sloping, densely vegetated areas that treat runoff as sheet flow from adjacent impervious areas. They function by slowing runoff velocity and filtering out suspended sediment and associated pollutants, and by providing some infiltration into underlying soils.
;Water balance
;water balance
:The accounting of inflow and outflow of water in a system according to the components of the hydrologic cycle.
;Water cycle
;water cycle
:The continuous movement of water from the oceans to the atmosphere (by evaporation), from the atmosphere to the land by condensation and precipitation, and from the land back to the sea (via groundwater and stream flow); also referred to as hydrologic cycle.
;Water budget
;water budget
:The mathematical expression of the water balance.
;Water quality volume
;water quality volume
:The amount of stormwater runoff from a given area required to be retained by stormwater management practices to reduce pollutant load to an acceptable level.
;Water table
;water table
:Subsurface water level which is defined by the level below which all the spaces in the soil are filled with water; The entire region below the water table is called the saturated zone.
;Watershed
;watershed
:An area of land that drains into a river or a lake. The boundary of a watershed is based on the elevation (natural contours) of a landscape.
 
;Clay
;clay 
:1. A mineral soil separate consisting of particles less than 0.002 millimeter in equivalent diameter. 2. A soil texture class. 3. (Engineering) A fine-grained soil (more than 50 percent passing the No. 200 Sieve) that has a high plasticity index in relation to the liquid limit. (Unified Soil Classification System). 
;Collector road 
;collector road
:A road on which traffic movement and access to property have similar importance. 
;Combined Sewer 
;combined sewer
:A wastewater collection system, which conveys sanitary wastewater (domestic, commercial and industrial wastewaters) and Stormwater runoff through a single-pipe system to a treatment works. 
;CSO 
;Combined sewer overflow 
;combined sewer overflow
:A discharge to the environment from a combined Sewer system that occurs because of a precipitation event when the capacity of the interceptor sewer or treatment plant is exceeded. It consists of a mixture of sanitary wastewater and Stormwater runoff. 
;Conveyance practice 
;conveyance practice
:A structural practice that is located within the drainage system where flows are concentrated and are being conveyed along corridor. Include but are not limited to pervious pipes, swales, and other similar systems. 
;Ditch 
;ditch
:A long narrow trench or furrow dug in the ground, as for irrigation, drainage, or a boundary line. 
;Drainage
;drainage 
:Natural or artificial means of intercepting and removing surface or subsurface water (usually by gravity). 
;Drainage area 
;drainage area
:The total surface area upstream of a point on a stream that drains toward that point. Not to be confused with watershed. The drainage area may include one or more watersheds. 
;Drainage system 
;drainage system
:A system flow of gully inlets, pipes, overland flow paths, open channels, culverts and detention basins used to convey runoff to its receiving waters. City of Toronto 45 Wet Weather Flow Management November 2006 
 
;E. Coli 
:A strain of bacteria found in the gut and waste products of animals. Some strains of this bacterium can be harmful to humans or animals if consumed. Food or water can become contaminated with E.Coli where unsanitary conditions exist. 
 
;Ecosystem 
;ecosystem
:A biological community, including humans and their natural environment. 
;End-of-pipe control
;end-of-pipe control 
:A structural best management practice that is located at the end of a flow conveyance route. End-of-Pipe Controls on surface and below ground but are not limited to wet ponds, constructed wetlands and other similar systems. 
;Enhancement
;enhancement 
:Emphasis on improving the value of particular aspects of water and related land resources. 
;Environment 
;environment
:Refers to the conditions in which an organism lives and survives or the conditions in which an organism resides. These conditions can be described as aspects of a “physical”, “social” or an “economic” environment, depending on the perspective perceived by the observer. 
;Erosion 
;erosion
:(1) The wearing away of the land surface by moving water, wind, ice or other geological agents, including such processes as gravitation creep; (2) Detachment and movement of soil or rock fragments by water, wind, ice or gravity (i.e. Accelerated, geological, gully, natural, rill, sheet, splash, or impact, etc). 
;Erosion control 
;erosion control
:Includes the protection of soil from dislocation by water, wind or other agents. 
;ET
:Evapotranspiation
;Evapotranspiration 
;evapotranspiration
:The quantity of water transpired (given off). Retained in plant tissues, and evaporated from plant tissues and surrounding soil surfaces. Quantitatively it is usually expressed in terms of depth of water per unit area during a specified period. e.g. mm/day
;Exfiltration 
;exfiltration
:The downward movement of water through the soil, the downward flow of runoff from the bottom of an infiltration BMP into the soil. 
;Extended detention
;extended detention 
:A stormwater design features that provides for the gradual release of a volume of water in order to increase settling of pollutants and protect downstream channels from frequent storm events. 
;First flush 
;first flush
:The delivery of a disproportionately large load of pollutants during the early part of storms due to the rapid runoff of accumulated pollutants. The first flush of runoff has been defined several ways (e.g., 10 mm per impervious area). 
;Floodplain (100-year) 
;floodplain
:The area adjacent to a stream that is, on average, inundated once a century 
;Geomorphology 
;geomorphology
:A branch of both physiography and geology that deals with the form of the earth, the general configuration of its surface, and the changes that take place due to erosion of the primary elements and the buildup of sediment. 
;Groundwater 
;groundwater
:The water below the surface, and typically below the groundwater table. 
;Groundwater recharge
;groundwater recharge 
:Increases in groundwater storage by natural conditions or by human activity. See also artificial recharge 
;Groundwater table
;groundwater table
;water table
;Water table 
:The upper surface of the zone of saturation, except where the surface is formed by an impermeable body. 
;Headwater 
;headwater
:Referring to the source of a stream or river. 
;Treatment train
;treatment train
:Stormwater management following the hierarchical approach: Source Control measures, Conveyance Control measure and End of Pipe treatment to achieve the water quality and water balance target for lot level development of the preferred strategy. 
;Hydrologic cycle 
:Also called the water cycle, this is the process of water evaporating condensing, falling to the ground as precipitation and returning to the ocean as run-off. 
;Hydrological
;hydrological 
:Relating to the properties, distribution and effects of water on and below the earth’s surface, and in the atmosphere. 
;Infiltration
;infiltration 
:The slow movement of water into or through a soil or drainage system. 
;Infiltration rate 
;infiltration rate
:The rate at which stormwater percolates into the subsoil measured in inches per hour. 
;I/I 
;Infiltration/Inflow 
:Inflow and/or infiltration of water into a sewer. 
;Irrigation
;irrigation 
:Human application of water to agricultural or recreational land for watering purposes. City of Toronto Wet Weather Flow Management November 2006 47 
 
;Local road 
;local road
:A road primarily for access to property. 
;Low Impact Development 
:Low impact development is a stormwater management and land development strategy applied at the parcel and subdivision scale that emphasizes conservation and use of on-site natural features integrated with engineered, small scale hydrologic controls to more closely mimic pre-development hydrologic functions. 
;Major drainage system
;major drainage system 
:That storm drainage system which carries the total runoff of the drainage system less the runoff carried by the minor system (storm sewer). The major system will function whether or not it has been planned and designed, and whether or not developments are situated wisely with respect to it. The Major Drainage System usually includes many features such as streets, gullies, and major drainage channels. 
;Minor drainage system
;minor drainage system 
;minor system
;Minor system
:That storm drainage system which is frequently used for collecting, transporting, and disposing of snowmelt, miscellaneous minor flows, and storm runoff up to the capacity of the system. The capacity should be equal to the maximum rate of runoff to be expected from the minor design storm which may have a frequency of occurrence of one in 2, or 5 years. The minor system may include many features ranging from curbs and gutters to storm sewer pipes and open drainage ways. 
;Natural systems solutions 
;natural systems solutions
:Projects following the philosophy in which terrestrial and aquatic vegetation provides the ability to cleanse water of its contaminants. 
;Oil/grit separator
;oil and grit separator 
;OGS
:Systems designed to remove trash, debris and some amount of sediment, oil and grease from stormwater runoff based on the principles of sedimentation for the grit and phase separation for the oil. 
;Outfall 
;outfall
:The point, location, or structure where wastewater or drainage discharges from a sewer pipe, ditch or other conveyance to a receiving body of water. 
;Overland Flow 
;overland flow
:Open space floodway channels, road reserves, pavement expanses and other flow paths that convey flows typically in excess of the capacity of the Minor Drainage System. 
;Peak Discharge 
;peak discharge
:The greatest volume of stream flow occurring during a storm event. 
;Permeable 
;permeable
:The property of a material that allows the infiltration or passage of water (or other liquids). 
;Pollutant 
;pollutant
:(1) Something that pollutes, especially a waste material that contaminate air, soil, or water. (2) Any solute or cause of change in physical, chemical or biological properties that render water unfit for a given use.
 
;Pond 
;pond
:A body of water smaller than a lake, often artificially formed.
;Porosity
;porosity
:The porosity (n) of a mixture is the ratio of the volume of void-space to the total or bulk volume of the mixture. It is closely related to the concept of void ratio (e) where void ratio is the ratio of the volume of void-space to the volume of solids. n = Volume of voids/Total volume of mixture = e/(1+e) 
;Precipitation 
;precipitation
:Any form of rain or snow. 
;Private Property 
;private property
:Land owned by private individuals or companies. 
;Public Property 
;public property
:Land owned by the City Toronto or any other level of government or public agency (such as Toronto and Region Conservation Authority, Toronto Transit Commission, school boards). 
;Rainfall Intensity 
;rainfall intensity
:The rate of rainfall in millimeters per hour. 
;Recharge
;recharge 
:The addition of water to ground water by natural or artificial processes. 
;Receiving waters
;receiving waters 
:Watercourses and Lake Ontario, to which Stormwater and Combined Sewer Overflows discharge. 
;Riparian areas
;riparian areas 
:Areas adjacent to a watercourse that are saturated by groundwater or intermittently inundated by surface water at a frequency and duration sufficient to support the growth of vegetation typically adapted for life in saturated soil. 
;Runoff
;runoff 
:The portion of water precipitated onto a catchment area, which then flows as surface discharge from the catchment area past a specified point.
;Sand 
;sand
:Mineral particles which are smaller than 2 mm, and which are free of appreciable quantities of clay and silt. Coarse sand usually designates sand grains with particle size between 0.2 and 0.02 mm. 
;Sediments 
;sediments
;sediment
;Sediment
:Soil, sand and minerals washed from land into water, usually after rain. They pile up in reservoirs, rivers and harbors, destroying fish-nesting areas and holes of water animals and cloud the water so that needed sunlight might not reach aquatic plans. Careless farming, mining and building activities will expose sediment materials, allowing them to be washed off the land after rainfalls. 
;Sedimentation 
;sedimentation
:Deposition of material of varying size, both mineral and organic away from its site of origin by the action of water, wind, gravity or ice. 
;Sewage 
;sewage
:The liquid waste from domestic, commercial and industrial establishments. City of Toronto Wet Weather Flow Management Guidelines November 2006 49 
 
;Silt
;silt 
:Soil or media particles smaller than sand and larger than clay (3 to 60 m) 
;Soakaway
;soakaway
:An underground water storage reservoir into which stormwater is directed and allowed to percolate into the underlying native subsoil. 
;Source control 
;source control
:A practice or structural measure that is usually implemented at the beginning of a drainage system or at the lot level, to reduce the volume of runoff and minimize the concentration of pollution in overland flow from private property and prevent pollutants from entering Stormwater runoff or other environmental media, as described by the Ministry of Environment. 
;Stakeholder 
;stakeholder
:Any person, agency or group who has a direct interest in the purpose of a proposed undertaking. 
;Stormwater 
;stormwater
:Surface runoff from at-grade surfaces, resulting from rain or snowmelt events. 
;STEP
:Sustainable Technologies Evaluation Program
;SWM
:Stormwater Management
;Stormwater wetlands
;stormwater wetlands 
:Shallow, constructed pools that capture stormwater and allow for the growth of characteristic wetland vegetation. 
;Subwatershed 
;subwatershed
:The drainage area of one or more contributing watercourses to a river. 
;Subwatershed plan
;subwatershed plan 
:The result of a study undertaken within the drainage area of one or more watercourses of a specific river following the guidance presented in the MOE Stormwater Management Planning and Design Manual (i.e. Humber Creek subwatershed within the Humber River Watershed). 
;Swale 
;swale
;Swales
;swales
;Grass swale
;grass swale
;Grass swales
;grass swales
;Vegetated swale
;vegetated swale
;Vegetated swales
;vegetated swales
:A shallow constructed channel, often grass-lined, which is used as an alternative to curb and channel, or as a pretreatment to other measures. Swales are generally characterized by a broad top width to depth ratio and gentle grades. 
;Total Suspended Solids 
:The total amount of particulate matter that is suspended in the water column. 
;URF
:unit response function
;Unit Response Function 
:Represents the hydrologic response and water quality response of the area to a pre-determined series of meteorological inputs. 
;UV disinfection 
:A process of disinfecting that involves subjecting the item, object, or instrument to ultraviolet radiation. 
;Void ratio
;void ratio
;Void space ratio
;void space ratio
:The void ratio (e) of a mixture is the ratio of the volume of void-space to the volume of solids. It is closely related to the concept of porosity (n) where porosity is the ratio of the volume of void-space to the total or bulk volume of the mixture. e = Volume of voids/Volume of solids = n/(1-n) 
;Watercourse 
;watercourse
:(a) A natural well-defined channel produced wholly or in part by a definite flow of water and through which water flows continuously or intermittently. Also, a ditch, canal, aqueduct, or other artificial channel for the conveyance of water to or away from a given place, as for the draining of a swamp. 
:(b) A stream or current of water. Legally, a natural stream arising in a given drainage basin but not wholly dependent for its flow on surface drainage in its immediate area, flowing in a channel with a well-defined bed between visible banks or through a definite depression (as a ravine or swamp) in the surrounding land, having a definite and permanent periodic supply of water (the stream may be intermittent), and usually, but not necessarily having a perceptible current in a particular direction and discharging at affixed point into another body of water. 
:(c) A legal right permitting the use of a flow of a stream (especially of one flowing through one’s land) or the receipt of water discharged upon land belonging to another. 
;Water conservation
;water conservation 
:Reduction in applied water due to more efficient water use such as implementation of Urban Best Management Practices or Agricultural Efficient Water Management Practices. The extent to which these actions actually create a savings in water supply depends on how they affect net water use and depletion. 
;Watershed 
;watershed
:The drainage area of a river. 
;Watershed plan 
;watershed plan
:The result of a study undertaken within the drainage area of a specific river following the guidance presented in the MOE Stormwater Management Planning and Design Manual (i.e. Humber River Watershed). 
;Wetland 
;wetland
:A vegetated area such as a bog, fen, marsh, or swamp, where the soil or root zone is saturated for part of the year. 
;Wet weather flow
;wet weather flow 
:Stormwater runoff generated by either rainfall or snowmelt or flow resulting from sanitary wastewater that enters the combined sewer system; infiltration and inflows from foundation drains or other drains are resulting from rainfall or snowmelt.