Rain Gardens, Swales & Barrels for Homeowners

Shoreline, Septic & Stormwater

Practical, low-cost ways to slow, spread, and soak stormwater so less pollution reaches the lake.

What Are These? (The Basics)

Rain Garden (Infiltration Basin)

A rain garden is a shallow, planted depression—typically 6–12 inches deep—designed to capture and soak up stormwater from your roof, driveway, or yard. Think of it as a purposeful low spot filled with deep-rooted native plants.

How it works: Water flows in during rain events, ponds briefly (usually draining within 24 hours), and infiltrates into the soil. Plant roots create channels that help water soak in while filtering out pollutants. The garden acts like a natural sponge, keeping dirty runoff from reaching the lake.

Vegetated Swale

A vegetated swale is a shallow, gently sloping channel planted with grasses, sedges, or other hardy vegetation. Unlike a ditch that rushes water away, a swale is designed to slow water down and spread it out.

How it works: As stormwater flows through the swale, vegetation slows the flow, allowing sediment to settle and water to infiltrate. Check dams (small ridges of stone or logs) can be added every 10–20 feet to further slow the water. Swales work best on gentle slopes (1–4%) and can move water along property edges or between your driveway and lawn.

Rain Barrel (or Cistern)

A rain barrel is a container—typically 50–100+ gallons—that captures roof runoff from a downspout. Larger systems (cisterns) can hold hundreds or thousands of gallons.

How it works: Instead of letting roof water rush down the driveway or into storm drains, the barrel captures it for later use (watering gardens, washing cars). An overflow valve directs excess water to a safe area like your lawn or a rain garden. Barrels are perfect for small properties or areas with slow-draining soils where infiltration practices aren't feasible.

Why These Practices Work

  • Capture first-flush runoff that carries most nutrients and fine sediment
  • Let soils filter and plants use water before it can reach ditches or shorelines
  • Reduce icing and erosion by keeping water off driveways and slopes

Step 1 — Read Your Site (10-Minute Walk-Through)

  • Where water goes now: Watch roof edges, downspouts, driveways, and paths during a rain
  • Soils: Dig a 12-in-deep hole; fill with water. If it drains in ≤24 hours, infiltration is feasible
  • Setbacks: Stay 10 ft from building foundations, 50+ ft from steep banks, and outside septic tanks/fields
  • Utilities & trees: Call before you dig; plan around roots

Step 2 — Choose the Right Practice

Rain Garden

Best for roofs/driveways on moderate soils and slopes (<10%)

Vegetated Swale

Best for moving and treating water along lot lines or edges; gentle grades (1–4%)

Rain Barrel

Best where space is tight or soils are slow; pair with overflow to lawn or garden

Quick Sizing Rules (Good Starts)

  • Contributing area → garden size: Aim for 5–10% of the roof/driveway area draining to it
  • Depth: 6–12 in from rim to flat bottom; deeper basins need wider side slopes
  • Overflow: Provide a stable spillway to lawn or another practice for big storms
  • Barrels: 50–100+ gallons each; screen inlets and add a bypass/overflow to a safe area

Simple Layouts (Text Diagrams)

Layout 1:
Downspout → splash pad → short swale → rain garden (flat bottom) → overflow to lawn

Layout 2:
Driveway edge → level-spreader stones → vegetated swale with 2–3 check dams → lawn

Building a Rain Garden (Weekend Project)

  1. Outline & dig: Remove sod; excavate to depth with a level bottom; keep topsoil for planting
  2. Shape side slopes: 3:1 or gentler; compact lightly on the sides, not the bottom
  3. Inlet protection: Add a small stone pad where water enters
  4. Soil mix (if needed): Loosen compacted bottoms; blend stockpiled topsoil with compost for structure
  5. Plant densely: Place taller plants toward the rim and center; sedges/rushes where water lingers
  6. Mulch: 1–2 in shredded mulch; keep stems clear
  7. Overflow: Form and stabilize a low point with stone or turf

Vegetated Swales (Do's & Don'ts)

Do:
  • Keep bottoms flat to slightly parabolic
  • Seed with deep-rooted grasses/sedges
  • Install check dams (short stone/log ridges) every 10–20 ft on steeper segments
Don't:
  • Channelize into a straight, eroding ditch—curve gently and widen where space allows

Plant Choices by Function

  • Deep roots (structure): clump-forming grasses and sedges
  • Pollinator support: a mix of flowers with staggered bloom times
  • Edge toughies: low, spreading groundcovers near paths and inlets
  • Shade-tolerant options for north sides or under trees

Cold-Climate Notes

  • Leave stems over winter for snow catch and habitat; cut back in spring to 6–8 in
  • Keep inlets/outlets clear of ice berms
  • Use minimum de-icing salt; sweep up excess in spring

Maintenance (Small Habits, Big Wins)

First season:
Water weekly if no rain; weed monthly
After big storms:
Rake redistributed mulch; check for rills; add stones where water concentrates
Every spring:
Top up mulch lightly; split and re-plant crowded clumps in year 3–4
Barrels:
Drain before hard freeze; clean screens; check overflows

Common Mistakes—and Fixes

  • Too small/no overflow

    Fix: Add a second cell or widen; cut a stable spillway

  • Steep sides

    Fix: Re-grade to gentler slopes; plant densely to hold soil

  • Compacted bottoms

    Fix: Loosen 6–8 in and mix in compost; avoid working wet soils

  • Downspout pointed at pavement

    Fix: Add elbow + splash pad or small swale to route into vegetation

Quick Worksheet (Fill-In)

Roof/driveway area to capture: ______ sq ft
Garden size target (5–10%): ______ sq ft
Soil infiltration test result: ______ hours
Chosen practice(s): Rain Garden / Swale / Barrel(s)
Overflow route: _________________________________
Plant list & quantities: __________________________
Maintenance calendar: ___________________________

Bottom Line

Sized right, planted dense, and given a safe overflow, rain gardens, swales, and barrels soak up the dirtiest runoff and keep your lake clearer—season after season.

Related Topics

Key Takeaways

  • Size gardens to 5-10% of drainage area
  • Test soil infiltration with 24-hour test
  • Always provide stable overflow path
  • Plant densely with deep-rooted natives
  • Keep bottoms flat, sides gentle (3:1)
  • Maintain regularly for best performance

Sizing Quick Reference

Garden Size Formula:

Roof/Driveway Area × 0.05 to 0.10 = Garden Size

Example:

1,000 sq ft roof × 0.08 = 80 sq ft garden (about 8' × 10')

Setback Requirements

  • 10 ft from building foundations
  • 50+ ft from steep banks
  • Outside septic tank/field areas
  • Away from utility lines (call 811)

Plant Selection Tips

  • Choose native species adapted to your region
  • Mix grasses, sedges, and flowering plants
  • Place taller plants at rim, shorter in center
  • Select plants that tolerate wet feet
  • Plan for year-round interest

Need Design Help?

Contact your local conservation district or extension office for site-specific guidance and plant recommendations.

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