Can steep slopes be effectively stabilized?
Written by
Kiana Okafor
Reviewed by
Prof. Samuel Fitzgerald, Ph.D.Stabilizing steep slopes requires special evaluation and methods that encompass not only the immediate dangers but also conditions that may affect the hill in the long run. Slopes that exceed 25% lose water extremely rapidly. Rain events create a situation where soil particles are drawn downhill due to gravity. Unless measures are taken to control erosion, these slopes can lose several inches of topsoil each year, leading to the formation of hazardous gullies.
Terracing Systems
- Build stone walls 0.6-1.2m high spaced 5-10m apart
- Reduces erosion 90% on slopes up to 45% gradient
- Costs $20-50 per linear meter with 15-30 year lifespan
- Requires annual inspection after heavy rainfall events
Vetiver Grass Hedgerows
- Plant deep-rooted vetiver grass along contour lines every 3-5m
- Roots penetrate 3-4m anchoring soil within 6 months
- Withstands water flows up to 0.8m³/sec on 35% slopes
- Establishment costs $2-5 per linear meter
Geotextile Installation
- Lay biodegradable jute/coconut fiber mats on exposed slopes
- Provides 75% immediate erosion control while vegetation establishes
- Degrades naturally over 2-5 years requiring no removal
- Costs $1-3 per square meter covering any slope angle
The most effective means of achieving an optimal response in a complex area is through the use of hybrid methods. In particular, the immediate blanket cover provided by geofabrics and hydroseeding while grass roots become established, as well as Vetiver grass between terrace walls, which provides permanent biological root strength, should be used. The result of these integrative methods can yield 80 - 95% surface and subsurface net erosion control throughout the slopes.
Structural alternatives are necessary for slopes exceeding 40%. Gabion walls built of local stone cost $15-25 per linear meter. For wooded areas, crib walls of interlocking timber are suitable. Soil nails let into the bedrock will stabilize the unstable regions. Consult geotechnical engineers for any slope greater than 45%.
Proper maintenance leads to long-lasting effectiveness. Inspect terraces after 50mm/hour of rainfall. Replant vegetation in bare spots every spring/summer. Remove debris from drainage channels each season. Well-maintained systems will last decades without slope failure, saving costly repairs.
Read the full article: 10 Soil Erosion Prevention Methods That Work
