Swales: TTT

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TTT.png

Swale element in TTT menu
Weir elements may be incorporated as checkdams

It is recommended that all swales be modelled as a 'Swale', which has it's own menu button in the TTT. For detailed scenarios of enhanced swales, the weir element can be incorporated for checkdams.

Parameters for 'Swale' elements in the TTT
Name User-assigned swale name
Upstream Node Name of node on the inlet end of the swale (which is normally the end at higher elevation)
Downstream Node Name of node on the outlet end of the swale (which is normally the end at lower elevation)
Length (m) Length of the swale
Manning's Roughness Manning's roughness coefficient
Upstream Invert Offset (m) Depth of swale invert above node invert at inlet end of the swale
Downstream Invert Offset (m) Depth or elevation of the swale invert above the node invert at the outlet end of the swale
Depth (m) Depth of the swale
Bottom Width (m) Bottom width of the trapezoidal swale (i.e., open channel)
For a triangular channel, enter 0
Left Side Slope (m/m) Left side slope (run/rise)
Right Side Slope (m/m) Right side slope (run/rise)
Seepage (mm/hour) Rate of seepage loss into the surrounding soil

The TTT also includes an 'enhanced swale' element within the LID toolbox. In version 1.0 this element does not incorporate checkdams and doesn't account for any infiltration capacity.

Parameters for 'enhanced swales' in the LID toolbox of the TTT
Surface
Berm 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 LID 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 infiltration, and slow flow to reduce erosion.
Swale side slopes (run/rise) Suggested value of 3 or 4 if design permits Enhanced swales
  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.