Filter strips: TTT

Vegetated filter strips are found within the LID toolbox

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. See Turf
Surface slope (%)	If the slope > 3%, consider using level spreaders to reduce erosion of the surface under high flow velocities.
Soil (native underlying soil, or amended topsoil)
Thickness (mm)	If topsoil has been amended Absorbent landscapes
Porosity (fraction)	Suggest range 0.35 – 0.4, unless otherwise tested
Field capacity (fraction)	Will vary according to native or amended topsoil
Wilting point (fraction)
Conductivity (mm/hr)
Conductivity slope
Suction head (mm)
Design drawdown time (hrs)	?

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.

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.

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)

The period between the maximum water level and the minimum level (dry weather or antecedent level).