Rill erosion results from the concentration of surface water (sheet erosion) into deeper, faster-flowing channels. As the flow becomes deeper the velocity increases detaching soil particles and scouring channels up to 30cm deep. Rill erosion represents the intermediate process between sheet and gully erosion.
- Particular concern in raised bed cropping systems
- Concentrated flow is able to detach and transport soil particles
- Channels form up to 30cm deep
- Intermediate process between sheet and gully erosion.
Prevention and Control
Once runoff has been initiated, rill erosion can be prevented by either reducing flow velocity, or hardening the soil to erosion.
Reducing Flow Velocity (settle suspended particles)
Flow velocity can be reduced by either reducing the flow volume or roughening the soil surface. Increasing surface roughness through the use of grassed waterways and grassed filter strips causes entrained soil particles to fall out of suspension. Flow volume can be reduced by not allowing sheet flow to accumulate. Techniques such as ripped mulched lines and contour drains prevent runoff building up enough volume and speed to detach and entrain soil particles.
- Rough surface, ie grassed waterways, grass filter strips
- Breaking the slope length, ie contour drains and ripper mulcher lines.
Hardening Soil Surface (prevent detachment)
Where options to reduce runoff volume or velocity are limited, surface soils may be protected from scouring by hardening the surface.
- Compact surface soils
- Paving and concrete lining
- Rock rip rapping.