Understanding Contour Swales: A Guide for Australian Landscape Architects

As urban landscapes across Australia face increasing pressure from climate variability, regulatory compliance, and public expectations of sustainability, water-sensitive design has moved from a ‘nice-to-have’ to a design essential.

One of the most underutilised, yet remarkably effective tools in this space is the contour swale—a subtle earthwork that turns stormwater from a liability into an asset. These elements behave completely differently to bioswales, rain gardens and other blue infrastructure.

This article introduces the core principles behind contour swales, explores their applications in Australian public, private, and commercial landscapes, and outlines key resources to support confident specification.

What Is a Contour Swale?

A contour swale is an (often shallow) vegetated channel dug on contour—that is, following the natural level lines of the land rather than running downhill. Unlike a drain or gully that removes water from a site, a swale is designed to capture, slow, spread, and infiltrate surface runoff where it falls.

Water enters the swale, spreads evenly along its length, and infiltrates slowly into the surrounding soil profile—hydrating plant roots, restoring subsoil moisture, and reducing pressure on built drainage systems.

While the concept is centuries old, it has gained new relevance in Australia’s urban context, particularly in relation to WSUD (Water Sensitive Urban Design) and green infrastructure goals.

Why Use Swales in Urban Landscapes?

Contour swales offer multiple co-benefits for urban and peri-urban sites:

• Passive irrigation: By keeping root zones moist after rain events, swales reduce the need for supplementary watering.
• Improved drainage: They relieve hard surfaces and compacted soil by providing infiltration zones that reduce localised flooding and runoff velocity.
• Stormwater filtration: Vegetated swales trap sediment and pollutants, improving water quality before it reaches natural waterways or stormwater networks.
• Soil and plant health: Swales help restore the natural soil sponge, encouraging microbial life and deeper rooting systems.
• Low visual impact: Properly integrated, swales can be made virtually invisible, blending into lawn depressions, rain gardens, or mulched beds.
• Climate resilience: They help landscapes cope with both intense rainfall and prolonged dry periods.

The ‘Tide’ Within a Swale

One of the more fascinating aspects of swale hydrology is the way water moves within it. When a swale is constructed correctly on contour, water doesn’t rush from one end to the other. Instead, it rises evenly along the entire length, like a gentle tide, and then slowly soaks into the soil.

This process—slow, spread, sink—is what makes swales so powerful. Rather than concentrating flow in one location, water is evenly distributed across a broader area, giving it time to infiltrate and hydrate without erosion.

Common Urban Applications

In an urban setting, contour swales can be adapted to:

• Street verges or median strips
• Public parks, especially on gentle slopes
• Commercial precincts or green car parks
• Rain gardens or bioswales adjacent to buildings
• Domestic landscapes, especially where waterlogging or dry zones persist

Importantly, they can be incorporated into retrofitting projects, as their depth and footprint can be tailored to existing infrastructure constraints.

As they are dictated by the landscape’s contours, they can be incorporated as a single swale across a whole site (usually, the lowest point on the highest boundary will give you the longest swale), or they can be replaced by multiple micro bunds (small strategic depressions) where they can fit into an existing landscape.

Design Considerations

While swales are low-tech in principle, successful outcomes require attention to detail:

• Slope and elevation: Laser levels or A-frames can help mark contour lines accurately.
• Soil type: Clay soils may infiltrate more slowly, but swales can still be highly effective if given time and adequate surface area.
• Vegetation: Contour swales are often thought of as tree-growing systems, however deep-rooted grasses/strappies, groundcovers, or shrubs that tolerate both wet and dry conditions can also be incorporated.
• Overflow planning: Include discreet overflow points to direct excess water during heavy rainfall into a connected bioswale, basin, or drain.

How Are They Different to Bioswales?

While a bioswale is used primarily to slow and filter water, with ground infiltration being a secondary function, contour swales are intended to capture the maximum amount of water possible within the ground water table. Contour swales make use of rainwater as a resource, instead of a waste product to be ‘dealt with’ and discarded.

Further Learning Resources

For landscape architects wishing to delve deeper, consider the following:

1. WSUD Guidelines – Check local council or state government publications (e.g. Melbourne Water, Brisbane City Council).
2. Soils for Life – Real-world case studies on landscape hydrology and soil repair.
3. Permaculture Research Institute – While rooted in rural contexts, the design principles are widely transferable.
4. Water by Design – Resources specifically for South East Queensland urban water management.
5. OzGREEN and Catchment Management Authorities – Regional organisations may offer site-specific swale and stormwater guides.

Daniel’s Wrap

Contour swales offer a highly scalable, cost-effective, and ecologically sound approach to modern landscape water management. Far from being rustic or rural, they can be refined, integrated, and designed to enhance both the function and form of urban outdoor spaces.

As landscape architects rise to the challenge of designing resilient, water-wise landscapes across Australia, contour swales should be part of every designer’s toolkit.