Green Neighbourhoods • AIPH

Water runoff

Image credit: Niek Roozen

Integrate water into planning and design

Surface storm water management solutions should be integrated into the overall design and planning of an area and involve a multidisciplinary team of professionals. This addresses technical and aesthetic issues in all design phases. Consider maintenance requirements in the design and budgets in order to guarantee performance and quality.

Use nature-based solutions for water management

Combine water management solutions with the need for recreation and nature in the city, and introduce other green city solutions such as green roofs and green streets. Be sure that the solution appropriately meets land use. Make stormwater visible in the design of public and private open spaces. Water features add to the amenity value of urban public green space. Create ways to not only buffer water but also to use in times of drought.

Compensate paving with water

All newly paved surfaces should be compensated by extra open water which equals at least 10% of the paved surface area.

Use trees to catch water runoff

Trees are very effective at slowing runoff. They intercept peak rainfall, improve the infiltration capacity of the soil, and can improve the quality of the water that is buffered. Trees can bring groundwater up to the surface where some evaporates, and the soil is kept moist. Conifers are 3x more effective than deciduous trees.

Use plants to help purify water

Biofiltering wetlands can be designed as functional and aesthetic solutions to surface water pollution. As water gradually filters through the plants into a series of basins, pollution sediments settle to the bottom. Careful attention to plant selection is essential.

Solve runoff problems closer to the source in urban areas with surface storm water management instead of draining all the water into the sewer system.

Green City Guidelines Home Green City Case Study Collection Green City Briefing: Water Management

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Techniques and technical solutions for surface storm water management

Technique	Description	Function	Application
harvesting	above or underground cisterns	rainwater use	fountains, pools, etc
bioretention	shallow landscaped depressions which drain by filtering through the vegetation and soil	water treatment	landscaped element
biotopes	ecologically stable landscape of plants and animals	water treatment	wetland, biofiltering wetlands
gravel/sand filters	above or below ground chambers to treat runoff	water treatment	edging along green spaces, channels, buildings
rooftop retention	extensive or intensive green roofs or brown roofs	detention + infiltration	green roofs
permeable paving	paving that allows water to pass to a gravel subgrade where it can evaporate, infiltrate or be drained	detention + infiltration	parking areas, paved areas
infiltration zones	planted areas with layers for retention, filtration	detention + infiltration + infiltration	open spaces trenches and parks
swales	linear planted drainage feature which allows water to travel downstream or infiltrate	detention + infiltration	open spaces and parks
geocellular systems	prefab underground structures to store and slowly infiltrate water	detention + infiltration	use in high density urban settings
detention pond (dry)	surface storage basin holds storm water and slowly drains and settles particulates (otherwise dry)	detention + infiltration	landscape and recreational uses
detention pond (wet)	surface storage basin stores/holds rainwater and circulates through other treatment techniques	detention + infiltration	ponds, lakes, recreation
channels	open storm water channels instead of sewerage	conveyance pipes underground	channels, streams, canals
passive	all green spaces with vegetation evapotranspiration	evapotranspiration	urban green spaces, gardens
active	use water to directly influence temperature or evapotranspiration	evapotranspiration air quality	rainwater walls, pools, fountains

Benefits of water runoff using green solutions

Reduces impervious surfaces in the city
Increases public awareness of water
Microclimate is cooler and more humid
Decreases the risk of flooding and storm sewer overflow
Less stormwater needs to be transported and processed in the sewerage system

New and existing developments

In new development:

Consider surface storm water management needs and solutions from the beginning of the planning and design process in order to provide the best integrated solutions for future runoff.

In existing development:

Reduce the area of impervious surfaces by replacing them where possible with the surface stormwater techniques (see next page) based on size, capacity, budget and surrounding development.

Plants with a high capacity to intercept water runoff

Conifer trees used in the Netherlands:

Abies, Picea, Pinus, Pseudotsuga menziessii

Deciduous trees used in the Netherlands:

Acer, Aesculus, Fagus, Quercus, Tilia, Ulmus

Plants used in biofiltering wetlands in The Netherlands

Lysimachia nummularia, Sagittaria sagittifolia,

Phragmites australis, Carex, Menyanthes trifoliata,

Pontederia cordata, Sparganium emersum

Combining the use of native plants and biofiltering capacity in landscapes, research in Australia provides a list of plants and their suitability and tolerance for managing water runoff.

Biofilter vegetation guidelines