Turf

Longer grass has biodiversity benefits as well as slowing flow on sloped surfaces.

Resilient turf grasses are particularly useful in the design of vegetated filter strips, dry ponds and enhanced grass swales. The Ministry of Transportation have standardised a number of grass mixes. Of particular value for low impact development applications is the 'Salt Tolerant Mix'.

Canada #1 Ground Cover (salt tolerant mix)

Common name	Scientific name	Proportion
Tall Fescue	Festuca arundinacea	25 %
Fults Alkali Grass	Puccinellia distans	20 %
Creeping Red Fescue	Festuca rubra	25 %
Perennial ryegrass	Lolium perrenne	20 %
Hard Fescue	Festuca trachyphylla	10 %

Best practices for mowing

Close mowing removes leaves and increases shoot production, leading to a denser 'velvety' appearance. But the damage also reduces the plant's photosynthetic processes and stunts its growth. Notably, when grass is stressed by close pruning, it doesn't have the resources to develop deeper roots. The shallow roots in turf grass make it particularly susceptible to drought conditions and significantly weakens the resiliency of the grass. Any pruning (including mowing) introduces cut edges on the leaf blades, increasing the potential for disease. Turf grass mixtures in Ontario often containa high proportion of Kentucky Bluegrass . For optimal long term health and resiliency, this turf should be cut no shorter than 7 cm. Permitting the grass to grow longer also increases the roughness of swales or vegetated filter strips which are turfed.

Manning's n of vegetated surfaces

n value range	Good condition turf grass	Other
0.002 - 0.010	Where the average depth of flow is at ≥ 2 times the height of the vegetation	Supple tree seedlings such as willow or cottonwood growing where the average depth of flow is at ≥ 3 times the height of the vegetation
0.010 - 0.025	Where the average depth of flow is between 1 - 2 times the height of the vegetation	Moderately dense weeds, or tree seedlings growing where the average depth of flow is from 2 -3 times the height of the vegetation
0.025 - 0.050	Where the average depth of flow is about equal to the height of the vegetation	8- to 10-year-old willow or cottonwood trees inter-grown with some weeds and brush (none of the vegetation in foliage)
0.050 - 0.100	Where the average depth of flow is < 0.5 times height of the vegetation	bushy willow trees about 1 year old inter-grown with weeds along side slopes (all vegetation in full foliage)

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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.