How to Build a Swale System Step-by-Step for Small Properties

 

Swales are simple earthworks that slow runoff, soak water into the ground & rebuild soil. This guide walks you step by step through mapping contours, sizing & digging a swale, planting the right trees & shrubs, and keeping it working long term. Expect clear tools list, practical tips, and safety notes for small to large sites.

Key Takeaways

• Start with a simple site check: slope, soil, trees and where water flows — then mark contours and size your swales to match the catchment.

• Swales slow and spread water to soak into the soil, cut erosion and help nearby plants stay healthy.

• Use the right tools for the job: A-frame or laser level, clinometer app, shovel or mini‑excavator, tamper and mulch — small properties usually need shallower, narrower swales.

• Learn permaculture the simple way with guides, tools, zone mapping, food forests, and companion planting methods that work in any climate or space.

• Keep an eye on maintenance and rules: check after big rains, clear spillways, fix gullies and confirm local permits, it saves time and keeps the system working

Site assessment & goals

Before touching soil, be clear about goals. Swales can slow and spread water, recharge groundwater, reduce erosion and support trees and gardens. On small lots the aim is usually to capture roof and yard runoff, protect structures and feed food-producing trees.

Quick checklist before design

• Define goals: tree establishment, orchard irrigation, stormwater control, erosion reduction
• Identify hard points: house, septic, power lines, neighbor boundaries
• Note existing vegetation: mature trees to keep, invasive patches to remove
• Access and mowing: where will equipment and people move?

Measure slope

Small properties still need accurate contour lines. Two easy methods:

• A-frame level: cheap, accurate for short runs. Build from three sticks and a string with a plumb bob; walk across yard to mark equal-level points.
• Laser level / line level: faster, excellent if you can rent one. Use stakes and flagging to mark the level line.

Tip: If you have a slope under 15% a typical swale on contour works well. Above that, consider terraced swales or check dams.

Map catchment with Google Earth

• Open Google Earth, sketch rough roof outlines and impermeable areas
• Draw flow arrows downhill and estimate catchment area (m2 or ft2)
• Mark likely inflow points (downspouts, driveways, gutters)
• Print or screenshot a map and draw rough contour lines from your A-frame marks

Simple percolation test

You need to know how fast the soil absorbs water. 1. Dig a test hole 30 cm (1 ft) wide and 30–60 cm (1–2 ft) deep. 2. Fill with water and let it drain fully. 3. Refill and time the drop over 1 hour. Rates: fast (>60 mm/hr), moderate (10–60 mm/hr), slow (<10 mm/hr).

• If slow, make shallower, more frequent swales, add organic matter, or plan overflow routes.

Note existing drains, pipes and access

Locate underground utilities before excavating. Call local utility locating service. Mark known drains and surface inlets on your plan. Plan movement paths for wheelbarrows and machines.

Design and sizing

Swales must sit on contour and be sized to match rainfall and catchment. For small properties keep designs simple.

Choose contour-aligned swales

• Swales run along contour so water spreads laterally and soaks in.
• For narrow lots consider short swales in series (terracing) rather than one long swale.

Typical swale cross-section

A simple swale has:

• A bench or flat top at the upstream edge (optional)
• Ponding zone (where water sits)
• Downhill berm built from excavated soil
• Overflow spillway along the berm low point

Diagram (visual idea):

• Upslope | ponding zone (shallow) | berm (compacted) | downslope

Size by catchment area and ponding depth

Use a simple target: store 25–50% of a 1-hour storm from your catchment area in on-site swales.

• Calculate catchment area (roof + hard surfaces). Convert to meters squared.
• Estimate expected rainfall depth for 1-hour design storm (local data or conservative 25mm/1in).
• Desired ponding depth on swale (typical 10–40 cm / 4–16 in). Deeper means fewer, larger swales but requires space.

Plan overflow spillways and neighbor flow

• Always design a safe overflow path at the lowest point of the berm — rough rock lined or gravel to prevent erosion.
• Check patios, garages and neighbor yards — never direct overflow to cause harm.
• For small lots consider directing overflow to storm drains only if allowed locally.

Construction step-by-step

This section focuses on small property methods (hand tools and small machinery).

Mark contours and stake bench line

1. Use your A-frame or laser level to walk the proposed swale line. Mark with flagging at 1–5 m intervals. 2. Drive stakes at each flag. Draw the bench/center line with string for a visual guide.

Excavate

• Hand tools: mattock, shovel and wheelbarrow for short swales (under 10 m).
• Machine: rent a mini-excavator for longer or deeper swales. A 1-ton to 3-ton machine fits small yards.

Steps: 1. Start at the highest point and work downhill. 2. Dig a shallow channel (target ponding zone depth). Keep excavated soil downhill to form the berm. 3. Make slopes gentle: outside berm slope 1:3 or flatter for stability and ease of planting.

Shape berms and compaction

• Build the berm directly from excavated soil. Shape to a rounded top or gentle slope.
• Compact in layers (10–15 cm lifts) using a hand tamper or plate compactor. Compaction prevents seepage through the berm and protects against burrowing.
• Leave a low point in the berm for the spillway — mark it clearly.

Add spillway material where needed

• For concentrated flows use a gravel or rock spillway 30–60 cm wide packed into the berm low point.
• Line the spillway with landscape fabric under rock to reduce erosion in very sandy soils.

Finish with mulch

• Cover bench and berm with a thick layer of mulch (10–15 cm). Mulch reduces evaporation, prevents crusting and protects soil life.
• If using wood chip mulch, keep it shallow where seeds are to be established.

Planting and soil building

Swales are structures for plants. Choose species that stabilize, build soil and serve your goals.

Plant palette for swale zones

• Swale ponding zone (drought-tolerant but water-tolerant): willows, alder, poplar cuttings (for fast uptake, in suitable climates)
• Berm top: deep-rooted trees (fruit and nut trees) and nitrogen-fixers (acacia, tagasaste, or local equivalents)
• Berm face and outer slope: native shrubs and hardy perennials
• Edge & berm toes: groundcovers and sedges to trap sediment and protect from splash

Useful plant mix:

• Overstory: deep-rooted fruit trees (apple, pear, olive in Mediterranean climates, citrus where frost-free)
• Support trees: nitrogen-fixers and dynamic accumulators (comfrey, tagasaste)
• Shrubs: berry shrubs, native buds
• Groundcovers: clover mixes, dymondia, oenothera, sedges

Soil building

• Add compost into the top 10–20 cm of soil on the berm and bench. A 2–5 cm layer incorporated initially speeds establishment.
• Use mulch heavily — wood chip or straw — and topdress with compost in the second year.
• Plant dynamic accumulator crops (comfrey, borage) to pull minerals up and provide mulch material.

Nurse plants & watering during establishment

• Young trees may need some watering the first 1–2 years. A swale reduces irrigation needs but doesn’t eliminate them for saplings.
• Use temporary drip lines or water bags near roots for critical dry spells.
• Plant faster-growing nurse shrubs that tolerate wetter conditions and provide shade for young trees.

Maintenance, permits and small-property hacks

Swales are low maintenance but need occasional checks — especially after big storms.

Routine maintenance tasks

• Inspect after heavy rain: watch for overflow points, erosion, or gullies on berms
• Remove sediment build-up in the ponding zone every 1–5 years depending on catchment
• Reseed or replant bare spots; replace mulch annually
• Repair berm compaction or animal burrow holes promptly

Permits and regulations

• Check local council or municipality for stormwater and excavation permits — especially near property boundaries and public drains.
• If altering drainage into public systems, you may need approval.
• Call utility locators before digging to avoid underground services.

Small-property hacks

• Narrower swales: reduce width and increase number in series — keeps water shallow and safer on small lots.
• Terraced swales: short swales separated by small drops work on steep small yards.
• Combine downspout diverters into swale inlets using pop-up drains or armored inlet boxes.
• Plan mow access: make berms low and flat on top so they can be mowed if needed.
• Use raised beds behind berms for crops that want more drainage.

Tools & measurements

Practical tools and what they’re used for.

• A-frame level — low-cost accurate contour finding
• Laser level / line level — faster, good for longer lines
• Clinometer or slope apps — quick slope measurements on phone
• Soil probe / auger — for percolation checks and soil depth
• Google Earth — for catchment mapping and distances
• Mini-excavator rental (1–3 ton) — for bigger jobs, fast digging
• Wheelbarrow, shovels, mattock — for handwork and shaping
• Plate compactor or hand tamper — for berm compaction
• Landscape fabric, gravel, rocks — for spillways
• Mulch (wood chips, straw) and compost — for finish and soil building

Templates and simple calculations

• A basic spreadsheet: list catchment areas, expected rainfall, desired ponding depth, then compute required swale volume and approximate length.
• Simple A-frame build plan: 3 sticks at 1–1.5 m and string with plumb bob — many online how-tos
• Percolation test sheet: hole depth, first fill time, refill and drop per hour, classification fast/moderate/slow

Quick resources to read more

• For conservation practice basics see the USDA NRCS practices and fact sheets: USDA NRCS
• Practical soil and water guidance and extension materials: Oregon State University Extension
• Tips for small-space permaculture, plant palettes and companion methods: Permaculture for small spaces - 10 Ways to Grow More

Conclusion

Quick recap: swales slow runoff, hold water and build soil. Main takeaways — map contours, size swales to your catchment, and plant deep-rooted trees plus groundcovers. Watch spillways and do small repairs early, don't wait. For step-by-step help try Permaculture Assistant — they teach permaculture the simple way with guides, tools, zone mapping, food forests and companion planting methods that work in any climate or space. Next: sketch your contours and dig a small test swale.

Related Posts

• Permaculture for Small Spaces: 7 Strategies to Create an Abundant Urban Garden
• Permaculture for small spaces - 10 Ways to Grow More
• Worm Composting Kits (Vermiculture): A Step Towards Zero-Waste Gardening
• Beekeeping Starter Kits: Your First Step Into Sustainable Beekeeping

Frequently Asked Questions (FAQs)

What is a swale and why should I build one on a small property?

A swale is a shallow, level-bottomed trench dug on the contour with a berm on the downhill side. It slows, spreads and soaks rainwater into the soil rather than letting it run off. On small properties swales help recharge soil moisture, reduce erosion, and boost garden or food-forest growth — without needing lots of space.

How do I size a swale for a small yard and what simple tools do I need?

Size it by the area draining to the swale (catchment) and how much rainfall you want to hold. For small yards start shallow (20–40 cm deep) and keep the berm narrow so it fits your space. Use an A-frame level or a laser/clinometer app to find contours; a soil probe or spade checks soil depth. For easy how‑tos and tool tips see the Permaculture Research Institute (https://www.permaculturenews.org/) and simple contour tools guides — they show how to measure slope and mark bench lines step by step.

Do I need permits or checks before digging a swale on a small property?

Often yes — check local building and drainage rules, easements, and utility lines. Call your local planning or public works office, and have underground services located before you dig. Also consider neighbors and where excess water will go; a quick check can keep you out of trouble.

What plants work best on a swale for a small property — and how can I learn permaculture the simple way?

Use deep-rooted trees on the berm and nitrogen-fixing shrubs to build soil; around the bench put water-loving shrubs, herbs and groundcovers to reduce weeds. Good picks: fruit trees (dwarf where space is tight), comfrey, legumes, sedges, and native grasses. To learn permaculture the simple way with guides, tools, zone mapping, food forests and companion planting methods that work in any climate or space, try practical step-by-step resources like Permaculture Assistant (https://www.permacultureassistant.org/) — they offer zone mapping tools and planting plans, plus clear guides for small sites.

How do I keep a swale working well and fix common problems on a small site?

Inspect after heavy rain; clear any bird-nest blockages in spillways and remove big sediment build-up from the ponding zone. If water starts cutting gullies, slow the flow with rocks, logs or a temporary sandbag bench, then replant. Add mulch and compost to the berm to help plants establish, and check tree roots before they get too big near structures. Regular small fixes keep swales effective and low-maintenance.