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;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.
: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.
Arterial Road
A road primarily for through traffic.
Base Flow
The portion of stream flow that is not due to storm runoff and is supported by groundwater seepage into a channel.
BMP or 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
Box like underground concrete structure with openings in curb and gutter designed to collect runoff from streets and pavement.
City
The City of Toronto
Clay (SOILS)
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
A road on which traffic movement and access to property have similar importance.
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 or 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 Control
A structural best management practice thatis located within the drainage system where flows are concentrated and are being conveyed along corridor. Conveyance controls include but are not limited to pervious pipes, roadside ditches, and other similar systems.
Ditch
A long narrow trench or furrow dug in the ground, as for irrigation, drainage, or a boundary line.
Drainage
Natural or artificial means of intercepting and removing surface or subsurface water (usually by gravity).
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
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
Dry Weather flow
Sewage flow resulting from both sanitary wastewater (combined input of industrial, domestic and commercial flows); and infiltration and inflows from foundation drains or other drains occurring during periods with an absence of rainfall or snowmelt.
E. Coli Bacteria
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
A biological community, including humans and their natural environment.
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
Emphasis on improving the value of particular aspects of water and related land resources.
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
(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
Includes the protection of soil from dislocation by water, wind or other agents.
Evapotranspiration (ET)
The quantity of water transpired (given off). Retained in plant tissues, and evaporated from plant tissues and surrounding soil surfaces. Quantitatively it is s
usually expressed in terms of depth of water per unit area during a specified period.
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
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
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., one half inch per impervious City of Toronto Wet Weather Flow Management November 2006 46
area).
Floodplain (100-year)
The area adjacent to a stream that is on average inundated once a century
General Manager
The person appointed by the City from time to time as the General Manager of Toronto Water and his or her successors or his or her duly authorized representative.
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 erosional debris.
Groundwater
The water below the surface, and typically below the groundwater table.
Groundwater Recharge
Increases in groundwater storage by natural conditions or by human activity. See also artificial recharge
Groundwater Table
The upper surface of the zone of saturation, except where the surface is formed by an impermeable body.
Headwater
Referring to the source of a stream or river.
Hierarchical Approach
Implementation of Wet Weather Flow measures following hierarchical approach in the following order:
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. In some guidance documents for Stormwater quality management, this is also known as the treatment train approach.
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
Relating to the properties, distribution and effects of water on and below the earth’s surface, and in the atmosphere.
Infiltration
The slow movement of water into or through a soil or drainage system.
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
Human application of water to agricultural or recreational land for watering purposes. City of Toronto Wet Weather Flow Management November 2006 47
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
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
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
Projects following the philosophy in which terrestrial and aquatic vegetation provides the ability to cleanse water of its contaminants.
Official Plan
The adopted Official Plan of the City of Toronto.
Oil/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
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 Path
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
The greatest volume of stream flow occurring during a storm event.
Permeable
Soil or other material that allows the infiltration or passage of water or other liquids.
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.City of Toronto Wet Weather Flow Management November 2006 48
Pond
A body of water smaller than a lake, often artificially formed.
Precipitation
Any form of rain or snow.
Private Property
Land owned by private individuals or companies.
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
The rate of rainfall in millimeters per hour.
Recharge
The addition of water to ground water by natural or artificial processes.
Receiving Waters
Watercourses and Lake Ontario, to which Stormwater and Combined Sewer Overflows discharge.
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
That potion of the water precipitated onto a catchment area, which flows as
surface discharge from the catchment area past a specified point.
Sand
Natural 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
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
Sewage
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.
The liquid waste from domestic, commercial and industrial establishments. City of Toronto Wet Weather Flow Management Guidelines November 2006 49
Silt
Substrate particles smaller than sand and larger than clay (3 to 60 m)
Soakaway Pit
A pit into which liquids may flow and then percolate slowly into the subsoil.
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
Any person, agency or group who has a direct interest in the purpose of a proposed undertaking.
Stormwater
Surface runoff resulting from rain or snowmelt events.
Stormwater Wetlands
Shallow, constructed pools that capture stormwater and allow for the growth of
characteristic wetland vegetation.
Subwatershed
The drainage area of one or more contributing watercourses to a river.
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
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 (TSS)
:The total amount of particulate matter that is suspended in the water column.
;Unit Response Function (URF)
: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.
;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
: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
:The drainage area of a river.
;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
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
: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.