Vegetated filter strips

Gallery

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  Unmown wildflower meadow roadside filter strip/verge in Delft

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  Filter strips are a common practice in rural road cross sections

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  Filter strips between the bioretention facility and the adjacent parking lot reduce sediment loading to the surface of the bioretention cell. Dennis Ave Health Center, Wheaton, MD. Photo credit: Moreau1

Modeling

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 for ideas of a good number according to mowing practices.
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 around 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)	Will be determined by regulatory authority, often 48 - 72 hours to reduce nuisance from mosquitoes

a gently sloping, densely vegetated areas that treat runoff as sheet flow from adjacent impervious areas. They function by slowing runoff velocity and filtering out suspended sediment and associated pollutants, and by providing some infiltration into underlying soils.

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.

The total mass of a pollutant entering a waterbody over a defined time period.

The net amount of something (e.g. chemical, such as phosphorus), calculated as the product of concentration and volume in a given time. Some BMPs significantly reduce loading of pollutants to the environment by reducing volume more so than concentration.

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).