Swales: TTT

From LID SWM Planning and Design Guide
Revision as of 20:05, 18 September 2017 by Jenny Hill (talk | contribs)
Jump to: navigation, search

TTT.png

SwaleA 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. element in TTT menu
Weir elements may be incorporated as checkdams

It is recommended that grass and enhanced grass swales be modelled using the 'SwaleA 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.' element in the TTT. A 'swaleA 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.' has to connect two existing elements within the TTT For detailed scenarios of enhanced swalesA 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., the weir element can be incorporated for checkdams. At this time the weirs are seperate elements which must be placed within several distinct swalesA 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. along a single reach.

The alternative is to use the 'enhanced swaleVegetated open channel, with check dams; designed to convey, treat and attenuate stormwater runoff.' within the 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. toolbox, but this incorporates fewer design parameters (and also excludes check damsStructures 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.).


A 'swaleA 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.' as a conveyance element in the TTT (key parameters)
General Info
Upstream Node Name of node on the inlet end of the swaleA 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. (higher elevation)
Downstream Node Name of node on the outlet end of the swaleA 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. (lower elevation)
Manning's Roughness Lower numbers indicate less surface obstruction and result in faster flow.
Suggested range for mown grass (dependent on density) 0.03 – 0.06 [1]
Upstream Invert (m) Depth of swaleA 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. invert above node invert at inlet end of the swaleA 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.
Downstream Invert (m) Depth or elevation of the swaleA 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. invert above the node invert at the outlet end of the swaleA 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.
X Section
Maximum Depth (m) Depth of the swaleA 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.
Bottom Width (m) Bottom width of the trapezoidal swaleA 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.
For a triangular channel, enter 0
Left Side Slope (m/m) Left side slope (run/rise). Suggested value of 3 or 4 if design permits. Enhanced swales
Right Side Slope (m/m) Right side slope (run/rise). Suggested value of 3 or 4 if design permits.
Seepage (mm/hour) Infiltration rateThe rate at which stormwater percolates into the subsoil measured in inches per hour. of native (or amended) soil

The TTT also includes an 'enhanced swaleVegetated open channel, with check dams; designed to convey, treat and attenuate stormwater runoff.' element within the 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. toolbox. In version 1.0 this element does not incorporate checkdams and doesn't account for any infiltration capacity.

Parameters for 'enhanced swalesA 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.' in the 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. toolbox of the TTT
Surface
BermA 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. height (mm) This is the height of the curb which constrains the overland sheet flow of water. Where the bottom of the slope discharges directly into another 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. facility without impedance, the value is 0.
Surface roughness (Manning’s n) Lower numbers indicate less surface obstruction and result in faster flow.
Suggested range for mown grass (dependent on density) 0.03 – 0.06 [1]
Surface slope (%) If the slope > 3%, consider using small Checkdams or weirs to permit temporary ponding, increase infiltrationThe slow movement of water into or through a soil or drainage system.Penetration of water through the ground surface., and slow flow to reduce 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)..
SwaleA 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. side slopes (run/rise) Suggested value of 3 or 4 if design permits Enhanced swales
  1. 1.0 1.1 Oregon State Univ., Corvallis. Dept. of Civil, Construction and Environmental Engineering.; Environmental Protection Agency, Cincinnati ONRMRL. Storm Water Management Model Reference Manual Volume I Hydrology (Revised). 2016:233.https://nepis.epa.gov/Exe/ZyPURL.cgi?Dockey=P100NYRA.txt Accessed August 23, 2017.