A gabion wall is beautiful and durable, but its longevity depends on proper drainage. Water is its biggest enemy: it carries fine particles, builds pressure in the backfill, and freezes in winter. The result can be stained stone, deformation, and faster corrosion of the baskets. This article focuses on gabion supporting walls and explains how to choose the right geotextile, how to layer the base, where to run pipes, and what slopes to maintain so you end up with a long‑lasting, dry, and clean gabion.

Why Gabion Drainage Is Critical

Proper drainage protects a gabion from water build‑up and clogging. Without filtration, fine soil particles migrate into the bed behind the basket, clog the drain, and then wash dirt through the stone face. In winter, water in the backfill can freeze, expand, and push baskets outward or create bulges. Prolonged damp contact accelerates wire corrosion, especially where the coating has been damaged. Good drainage is therefore an investment in appearance, stability, and service life.

Geotextiles: Types and How to Choose for Filtration and Separation

A geotextile may be unobtrusive, but it’s decisive. It serves two functions: separation (keeping soil out of the drainage aggregate) and filtration (letting water through while retaining fines).

Nonwoven vs. woven geotextile

• Nonwoven geotextile: Ideal as a filter behind a gabion thanks to higher permeability and the ability to trap fine fractions.
• Woven geotextile: Better suited to subgrade stabilization; it performs worse as a filter behind a gabion.

Recommended specifications and placement

• Weight: 200–300 g/m² for most soils.
• Location: A continuous strip behind the entire back face of the basket and beneath the drainage layer.
• Details: Do not pull the geotextile around to the gabion face. Pin it to the subgrade with nails or ground staples.

Drainage Layers Under and Behind the Gabion

The right layer build‑up provides bearing capacity and drains water. The goal is to intercept water from the terrain into the drainage zone and carry it away safely.

• Base layer: Compacted gravel‑sand (granular) base with a minimum fall of 1–2%.
• Drainage aggregate: Washed gravel 16/32 mm, separated from the native soil with geotextile.

Pipes, Inlets, and Slopes: How to Carry Water Away

• Drain pipe: Perforated DN 100 pipe installed below the bottom edge of the basket.
• Fall: 1–2 % toward the discharge point.

Grading and Discharge

Both the sub‑base and the drainage system must have a clear outflow direction. Never leave a drain pipe without a functioning outlet.

Details for Slopes and Retaining Walls

Water behaves more aggressively on slopes. The essentials are stepping the footing and creating terraces.

The Most Common Mistakes—and How to Avoid Them

• Missing geotextile → rapid clogging and staining of the face.
• Replacing drainage gravel with sand/soil → no filtration.

Installation at a Glance

1. Build the compacted base and install the drain pipe.
2. Form a drainage wedge of gravel.
3. Set and anchor the gabion baskets.
4. Fill with stone in lifts.
5. Connect the drainage to the outlet.
6. Finish grading and protect against surface runoff.

→ Detailed installation instructions for gabion fences!

Maintenance and Drainage Checks

Twice a year, visually inspect outlets and access points; remove leaves and debris.