Size on-contour swales for water infiltration, soil recharge, and overflow management — built for BC soils and slopes.
A swale is a shallow, on-contour trench with a berm on the downhill side. Unlike ditches, swales are not graded to move water — they hold it in place so it infiltrates into the soil. Every drop of rain that enters a swale soaks into the ground rather than running off your property. Over time, this builds a lens of subsurface moisture that feeds trees, pasture, and wells downslope. Brad Lancaster calls this the first principle of water harvesting: slow it, spread it, sink it.
Swales work best on permeable soils (sandy, loam, or sandy loam) at slopes between 2% and 15% where the goal is groundwater recharge and soil moisture improvement. They pair naturally with Yeomans' keyline design — swales capture water at the top of the system, and keyline ripping distributes it laterally across the landscape between ridges and valleys.
Swales are not appropriate for slopes steeper than 15% (landslide risk), heavy clay soils near structures (water pooling against foundations), or sites where you need to move large volumes of water to a pond. In those cases, diversion drains, keyline ripping, or bench terracing are better tools. If your soil is clay-dominant, a pond may store more water more effectively than swales that sit full without infiltrating.
Enter your site conditions and swale dimensions to calculate volume, spacing, berm sizing, and storm capacity.
50 mm is standard for most BC sites. Use 75-100 mm for exposed or high-elevation sites, and Interior rain-on-snow conditions.
Typical 0.6 - 1.8 m
Half as deep as wide
Enter your total property or catchment area to calculate the number of swales needed.
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--Typical on-contour swale with downhill berm. All swales are built level along the contour so water spreads evenly and infiltrates in place.
Every earthwork needs a designed overflow path. The standard cascade runs:
Build sequence (Yeomans): establish the lowest overflow path first, then build swales from the bottom of the system upward.
Swales on private land that do not intercept a stream, seasonal drainage, or wetland likely require no authorization under BC's Water Sustainability Act. However:
Swales are one piece of the puzzle. Use the Water Planner to estimate total capture, storage needs, and system recommendations for your property — or get in touch for a site visit.