Erosion and run-off on a sloped garden
Soil Washing Off a Sloping Garden
Water moving down a bare slope carries material with it. The steeper and barer the slope, the faster it goes — which is why mulch ends up on the patio every autumn.
The answer is to slow the water and hold the surface.

Terracing
Breaking a slope into level terraces with sleeper or block retaining converts one long run into a series of flat areas. It stops erosion and turns unusable ground into space you can actually stand on.
Each terrace needs drainage behind the retaining, not just the bottom one.
Planting and ground cover
Deep-rooting ground cover binds soil far more effectively than annual bedding. Established planting is the cheapest long-term stabilisation there is.
Jute or coir matting holds the surface while planting establishes on steeper banks.
Surfaces and edging
Loose gravel migrates on any noticeable slope; bark washes even more readily. Where a path crosses a slope, resin-bound or paved surfaces with proper edge restraint stay put.
Cross-falls and channels intercept water before it gathers speed.
Frequently asked questions
How steep is too steep for gravel?
Anything beyond a gentle gradient will migrate; bound surfaces are the practical alternative.
Do I need permission to terrace a garden?
Usually not for modest landscaping, but significant level changes near boundaries warrant checking locally.
What holds a bank best?
A combination — retaining at the steepest points and dense planting elsewhere.
Related reading
Slope washing away?
We terrace, retain and plant sloping gardens across Essex.