Inlets

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Concentrated flow inlets are associated with LIDLow 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. practices such as Bioretention, Stormwater planters, Infiltration trenches and chambers. Sheet flow alternatives include level spreaders, gravel diaphragms and vegetated filter strips. Practices such as permeable paving and green roofs receive precipitationAny form of rain or snow. directly, whilst exfiltration trenches are connected directly to conventional storm sewers.

Inlets for BMPs in the right of way should be located:

  • At all sag points in the gutter grade
  • Immediately upgrade of median breaks, crosswalks, and street intersections.

It is good practice to have several inlets sized to split higher flow between a number of smaller BMPs or along the length of a linear pratice (Offline overflow).

Trench drains Curb cuts Inlet sumps Depressed drains
  • A long, covered channel that collects directs water into the BMPBest 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..
  • An excellent solution for streets where walking across the entire surface is to be encouraged. They can be designed as detectable edges or part of a detectable edge, and may be used to help define curbless or 'complete streets'.
  • Trenches may either be shallow (where runoffThat potion of the water precipitated onto a catchment area, which flows as surface discharge from the catchment area past a specified point.Water from rain, snow melt, or irrigation that flows over the land surface. volume is less of an issue) or deep and covered by a metal grate. Deeper trench drains may gather sedimentSoil, 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. and require frequent maintenance.
  • Drains may be configured either perpendicular or parallel to the flow direction of the roadway, collecting runoffThat potion of the water precipitated onto a catchment area, which flows as surface discharge from the catchment area past a specified point.Water from rain, snow melt, or irrigation that flows over the land surface. and directing to a single inlet in the BMPBest 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..
  • Inlet aprons or depressions increase inflow effectiveness of curb cuts.
  • Steeply angled aprons can be hazardous, especially to people bicycling. Curbside and protected bike lanes along concrete aprons should be at least 1.8 m to give cyclists adequate clear width from the curb and any pavement seams. Aprons can also be marked visually to indicate their perimeter.
  • For aprons into bioretention, the curb may angle into the cell to improve conveyance of gutter flow into the facility. Aprons typically drop 50 mm into the bioretentionA shallow excavated surface depression containing prepared filter media, mulch, and planted with selected vegetation. cell, with another 50 mm drop behind the curb to maintain inflow as debris collects.
  • A depressed concrete apron can be cast in place or retrofitted in by grinding down the existing concrete pavement.
  • Where the curb alignment along the street is straight, the curb opening may optionally have a bar across the top of the inlet.
  • An inlet sump is recommended to settle and separate sedimentSoil, 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. from runoffThat potion of the water precipitated onto a catchment area, which flows as surface discharge from the catchment area past a specified point.Water from rain, snow melt, or irrigation that flows over the land surface. where a large amount of debris is expected.
  • Water drains into a catch basinGround depression acting as a flow control and water treatment structure, that is normally dry., where debris settles in its sump. After pretreatment, water drains via a pipe or opening into the BMPBest 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..
  • The sump can be directly connected to a perforated underdrain pipe to distribute the flow to the bioretention, supported soil cells or underground practices such a trenches or chambers .
  • Sump inlets should not be sited where pedestrians will have to negotiate with them.
  • RunoffThat potion of the water precipitated onto a catchment area, which flows as surface discharge from the catchment area past a specified point.Water from rain, snow melt, or irrigation that flows over the land surface. in the gutter drops into a grate-covered drain before flowing into the BMPBest 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.. Drain covers must be compatible with bicycling and walking; grid covers are preferred.
  • Depressed drains are a potential solution for bioretentionA shallow excavated surface depression containing prepared filter media, mulch, and planted with selected vegetation. cells on sloped streets where directing runoffThat potion of the water precipitated onto a catchment area, which flows as surface discharge from the catchment area past a specified point.Water from rain, snow melt, or irrigation that flows over the land surface. into the cell is a challenge.
  • This style of inlet can be combined with a curb cut, to maintain capacity in case debris clogs the grate.
Depressed drains: Gallery

External links

https://nacto.org/publication/urban-street-stormwater-guide/stormwater-elements/bioretention-design-considerations/inlet-design/