By Sarah Chen · environmental engineer · water, waste and everything that flows downhill
“My first swale held back the flood, but I failed to account for the 300mm annual rainfall in the dry zone, so the vegetation died and the soil washed out.”
— Sarah. Every litre accounted for.
ArticlesCalculatorsSite PlannerShopNo time for theory. Here's how to build swales that actually work on Australian soil. We cover contour mapping, spacing, vegetation, and where to get tools without breaking the bank. All prices in AUD.
By Sarah Chen · environmental engineer · water, waste and everything that flows downhill
“My first swale held back the flood, but I failed to account for the 300mm annual rainfall in the dry zone, so the vegetation died and the soil washed out.”
No time for theory. Here's how to build swales that actually work on Australian soil. We cover contour mapping, spacing, vegetation, and where to get tools without breaking the bank. All prices in AUD.
Swales must follow true contours. Not "close enough" – true. Slope is everything. If you get this wrong, water runs straight off your property.
How to do it (Aussie method):
Don't use A4 paper. It's a waste of time. Get the laser level. It's cheaper than fixing a failed swale.
Spacing depends on slope. Too close? Wasted effort. Too far? Water runs off. Here's the real-world guide:
| Slope | Recommended Spacing | Why |
|---|---|---|
| 0-5% (flat) | 15-20m | Water moves slowly. Less swales needed. |
| 5-10% (typical Aussie slope) | 10-15m | Balance between water capture and labour. AS/NZS 1547:2019 recommends this range for water retention. |
| 10%+ (steep) | 5-10m | Prevents erosion. You'll need more swales. |
Swales aren't just ditches. They're living systems. Plant the right stuff or your swale becomes a muddy hole.
| Plant Type | Why It Works | Australian Supplier (AUD) |
|---|---|---|
| Native Grasses (e.g., Kangaroo Grass) | Deep roots hold soil. Drought-tolerant. No water needed after establishment. | Native Plants Australia ($15-$25 for 100 seeds) |
| Acacia (Wattles) | Nitrogen fixer. Fast growth. Attracts birds. | Perth Native Nursery ($8-$12 per plant) |
| Food Crops (e.g., Kumara) | Planted on the berm (swale wall). Uses captured water. | Local farmers' markets ($3-$5/kg) |
| AVOID: | Exotic grasses (e.g., Couch, Kikuyu) | They'll choke your swale and need constant watering. |
Need a guide? Get The Permaculture Handbook (Aussie author, $45 AUD). Covers swales in detail. No fluff.
Building swales isn't expensive. Here's what you'll actually spend on a 50m swale (typical off-grid block):
Total: $480 AUD for a swale that captures 50,000L+ of rainwater annually. That's cheaper than a single tank.
While many off-grid projects are achievable as DIY, certain situations require licensed professionals:
Always check local regulations and obtain necessary permits before commencing work.
Worth a watch: DESIGNING SWALES - Geoff Lawton visits The Weedy Garden - Swales Part Two. · The Weedy Garden