Wet ground: drainage, ditches and channels

In short

• Diagnosis before the spade: a test pit after rain, a percolation test, plants and soil colour.
• Water from the slope is caught with a cut-off ditch; water perched on a compacted layer needs loosening and raised beds; a high water table needs drainage or plants that tolerate it.
• Every drain needs a fall and an outlet: at least 0.5 % (5 mm per metre), better 1 %.
• French drain for a garden: trench 30–40 cm wide, 60–90 cm deep, a 100 mm (4 in) pipe in gravel and geotextile.
• Don't send water onto a neighbour or the road. Check for buried services before you dig.
• Don't go into a trench deeper than 1.2 m without support: the sides collapse without warning.

What's inside

Chapters

1. Where the water comes from
2. Rules about neighbours and water
3. Without digging channels
4. How to measure the fall
5. Open channels and ditches
6. French drains
7. Where the water goes: outlets and soakaways
8. Water around the house and outbuildings
9. Maintenance
10. Common mistakes
11. Printable checklist

Worksheets

• Wet-ground diagnosis
• Drainage plan
• Drainage and soakaway calculator
• Water-level log
• Drainage and ditch calendar