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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 standardized a number of grass mixes[1]. The 'Salt Tolerant Mix' is of particular value for low impact developmentA 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. applications alongside asphaltA mixture of mineral aggregates bound with bituminous materials, used in the construction and maintenance of paved surfaces. roadways and paved walkways.

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 [2]. For optimal long term health and resiliency, this turf should be cut no shorter than 7 cm. [3] 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 [4]
'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)

  1. Ontario Provincial Standard Specification. (2014). Construction Specification and for Seed and Cover OPSS.PROV 804. Retrieved from http://www.raqsb.mto.gov.on.ca/techpubs/ops.nsf/0/3a785d2f480f9349852580820062910a/$FILE/OPSS.PROV 804 Nov2014.pdf
  2. OMAFRA Lawn Establishment July 2008 http://www.omafra.gov.on.ca/english/crops/facts/08-025w.htm#turf Accessed Dec 19, 2017
  3. Karen Panter, Turf and Water, Sept 12, 2013 https://www.slideshare.net/kpanter/turf-and-water Accessed Dec 19, 2017
  4. Arcement, G.J., Schneider, R. Guide for Selecting Manning's Roughness Coefficients for Natural Channels and Flood Plains U.S.G.S. WATER-SUPPLY PAPER 2339, 1989 http://eh.sdsu.edu/usgs_report_2339.pdf Accessed Dec 19 2017