LID opportunities on residential land

Take a look at a typical home. What opportunities exist to implement LID?

On residential lands, hard surfaces such as the roof, patio, walkways and driveways can all be targeted to collect, treat, and infiltrate runoff. The practices you choose will vary depending on neighbourhood and site constraints and landscape ideals identified during market research

This chapter will provide examples of residential landscape alternatives and LID retrofits that are options for a municipal program. For a good “how to” resource for homeowner LID installation, see TRCA’s Greening Your Grounds: A Homeowners Guide to Stormwater Landscaping Projects, available for purchase at TRCA.on.ca. For more technical information and design guidance on LID practices, see the Low Impact Development Stormwater Management Planning and Design Guide, available at bealeader.ca

Landscape alternatives

Landscape alternatives can be established in any green space. They are most frequently established in front yards. (Source: Region of Peel)

Landscape alternatives capture rainfall in leafy green foliage. This allows for infiltration, filtration, and evapotranspiration of rainfall and runoff. Landscape alternatives can be designed to require little maintenance and less
irrigation after establishment than sod lawns. They are a great water conservation tool. Landscape alternatives allow homeowners to customize their property’s landscape to their liking. A guiding principal when designing
landscape alternatives is “the right plant for the right place”. Use of both native and non-native plants is acceptable as long as the non-native plants are not invasive and do not require frequent watering.
There are various landscape alternatives available, including:

• Fusion Landscaping®
• Xeriscaping
• Tree Clusters

Fusion Landscaping®

A great example of a landscape alternative is the Region of Peel’s Fusion Landscaping® program. Fusion Landscaping® combines the lush splendour of traditional gardens with modern, eco-friendly plants.
This program uses local market research and social marketing to promote behavioural change, address residents’ unique needs, and reduce outdoor water use.

Xeriscaping

Xeriscaping refers to landscaping, plantings and gardening practices that reduce or eliminate the need for watering. Synonymous with terms such as water-conservative, xeriscaping was originally promoted in areas with perennial water shortages. With xeriscaping, plants are selected based on their ability to survive with little water. Additional benefits include reducing water bills, lower maintenance requirements, better plant survival and aesthetics during drought periods. Xeriscaping can be used alone or it can be combined with a larger residential LID program.

Tree clusters

Tree clusters are another residential landscape alternative. They provide some of the function of forested areas by intercepting rainfall and allowing for evapotranspiration and infiltration of stormwater runoff.

Residential rain gardens are a great way to reduce runoff from both landscape surfaces. (Source: Fern Ridge Landscaping)

Tree clusters improve water quality, generate organic soils, absorb greenhouse gases, and provide shade for homes. Tree clusters require larger lot sizes and preferably no overhead wires. They can be planted as a standalone feature or part of a larger residential LID landscape.

Rain gardens

On the outside, rain gardens look like a typical garden. However, their function is much greater than a normal garden Rain gardens are landscaped areas that include a surface depression of approximately
150 mm (6 inches) that allows runoff from residential property to collect and easily absorb into the ground. Within the rain garden a special type of soil, referred to as bioretention soil media, can be used to
improve the amount of water that gets absorbed by the garden and On the outside, rain gardens look like a typical garden. However, their function is much greater than a normal garden Rain gardens are
landscaped areas that include a surface depression of approximately 150 mm (6 inches) that allows runoff from residential property to collect and easily absorb into the ground. Within the rain garden a special
type of soil, referred to as bioretention soil media, can be used to improve the amount of water that gets absorbed by the garden and infiltrated into the native soils. Location is very important to a functioning rain garden.
When looking at potential locations, look for low areas where runoff can be easily be directed into the garden. Rain gardens are a great option for residential LID retrofits because homeowners can customize
the garden to suit their desired style. They can be planted with a variety of vegetation including shrubs, grasses and flowers.

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Rain gardens are frequently at the outlet of downspouts. (Source: Aquafor Beech)

A well-designed rain garden can be maintained with minimal care which is a great marketing point for homeowners. In the first two years, the plants will need watering to ensure they become established.
After this establishment period, the garden should only need simple maitenance such as weeding.

Permeable pavement

Permeable pavement are surfaces that encourage infiltration. They can be used in place of conventional asphalt or concrete pavement. These alternatives contain pores, spaces or joints that allow stormwater to pass through to a stone base where it is infiltrated into the underlying native soil or temporarily detained. Types of permeable pavement include:

• Pervious concrete
• Porous asphalt
• Permeable interlocking concrete pavers (PICP, or just permeable pavers)

Permeable pavement can be used for both driveways and walkways. When infiltrating driveway runoff, confirm whether your residential neighbourhood is in a wellhead protection area. Driveway runoff should not be infiltrated if in a wellhead protection area due to the risk of groundwater contamination. Contact your local Conservation Authority for more information on wellhead protection areas.
Focus on aesthetic appeal when marketing permeable pavers to homeowners. They come in a variety of colours and shapes, and can be laid out to form patterns or designs that enhance the landscape of residential properties.
Permeable pavement may also appeal to homeowners because it typically has a longer life span that traditional asphalt. As well, light coloured pavers typically require less winter maintenance. Water and snow generally seep through the joints of the pavers before ice can form. This reduces the amount of salt homeowners need to use on their driveways, walkways or patios.

Soakaways and infiltration trenches

Soakaways, also known as infiltration galleries and dry wells, are excavations in native soil that are filled with geotextile fabric and clean granular stone. Soakaways are typically designed with a perforated pipe inlet from a relatively clean water source, such as a roof or pedestrian area. When possible, soakaways should be installed in areas where native soils allow for infiltration. If poorly draining soils are present, an underdrain can be installed to remove standing water.
Soakaways can be designed in many shapes and sizes. Larger pits can be used on residential lots with lots of available space.Where lot size is a constraint, a linear variation known as an infiltration trench can be used. This technique may be appropriate for sites where retrofit space is limited to long strips between buildings or along property lines.

Rainwater harvesting

Rainwater harvesting is the process of collecting and storing rainwater for future use. Harvested water can be used for a variety of indoor and outdoor non-potable uses with minimal treatment. Rainwater harvesting provides an easy and lowcost option for homeowners to reduce the volume of runoff conveyed from their properties to the municipal storm sewer system.

Rainwater harvesting systems

Rainwater harvesting systems collect rainwater from roof runoff and store it until it is needed. These systems are typically used for irrigation, however with additional equipment and proper treatment this water can be used for indoor purposes like toilet flushing and laundry. By using rainwater around the home residents can reduce their water bills while also reducing the amount of stormwater runoff entering the storm sewer system. Rainwater storage tanks come in a variety of dimensions and shapes to accommodate both the size and desired aesthetics of residential properties. They can fit unobtrusively against the home, buried underground, or even placed below a deck.

Rain barrels

While they provide similar functions to rainwater harvesting systems, rain barrels have much more limited storage space. Rain barrels are installed at the outlet of downspouts and intercept water draining down roofs. Water collected in rain barrels can be used for irrigation. Rain barrels come in a variety of shapes, sizes and styles. Residents can choose a style of rain barrel that is best suited to their home and personal tastes. For example, rain barrels can be decorated to create garden art.

The portion of water precipitated onto a catchment area, which then flows as surface discharge from the catchment area past a specified point.

Water from rain, snow melt, or irrigation that flows over the land surface.

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.

Toronto and Region Conservation Authority

Low impact development is a stormwater management and land development strategy applied at the parcel and subdivision scale that emphasizes conservation and use of on-site natural features integrated with engineered, small scale hydrologic controls to more closely mimic pre-development hydrologic functions.

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.

Surface runoff from at-grade surfaces, resulting from rain or snowmelt events.

The slow movement of water into or through a soil or drainage system.

Penetration of water through the ground surface.

The technique of removing pollutants from runoff as it infiltrates through the soil.

The quantity of water transpired (given off). Retained in plant tissues, and evaporated from plant tissues and surrounding soil surfaces. Quantitatively it is usually expressed in terms of depth of water per unit area during a specified period. e.g. mm/day

The combined loss of water to the atmosphere from land and water surfaces by evaporation and from plants by transpiration.

Human application of water to agricultural or recreational land for watering purposes. City of Toronto Wet Weather Flow Management November 2006 47

Defined as those plants (including grasses, herbaceous species, shrubs, vines and trees) that have historically existed within a particular area. Native plants have co-evolved with the local ecosystems and natural processes.

A lot level bioretention cell designed to receive and detain, infiltrate and filter runoff, typically used for discharge from downspouts.

A shallow excavated surface depression containing prepared filter media, mulch, and planted with selected vegetation.

An alternative practice to traditional impervious pavement, prevents the generation of runoff by allowing precipitation falling on the surface to infiltrate through the surface course into an underlying stone reservoir and, where suitable conditions exist, into the native soil.

A mixture of mineral aggregates bound with bituminous materials, used in the construction and maintenance of paved surfaces.

The natural ground material characteristic of or existing by virtue of geographic origin.

An alternative practice to traditional impervious pavement, prevents the generation of runoff by allowing precipitation falling on the surface to infiltrate through the surface course into an underlying stone reservoir and, where suitable conditions exist, into the native soil.

Filter fabric that is installed to separate dissimilar soils and provide runoff filtration and contaminant removal benefits while maintaining a suitable rate of flow; may be used to prevent fine-textured soil from entering a coarse granular bed, or to prevent coarse granular from being compressed into underlying finer-textured soils.

Gravel, or crushed stone of various size gradations (i.e., diameter), used in construction; void forming material used as bedding and runoff storage reservoirs and underdrains in stormwater infiltration practices.

A perforated pipe used to assist the draining of soils.

Water ponded on the ground surface.

The practice of intercepting, conveying and storing rainwater for future use. Captured rainwater is typically used for outdoor non-potable water uses such as irrigation, or in the building to flush toilets.

The practice of intercepting, conveying and storing rainwater for future use. Captured rainwater is typically used for outdoor non-potable water uses such as irrigation, or in the building to flush toilets.