Slope Surface Roughening

Image from Ohio Rainwater and Land Development Manual

Steep slopes on a construction site can lead to some problems when talking about erosion control and water runoff. Slopes greater than 3:1 allow water to quickly run down the slope leading to erosion and possible water damage downhill. In this month’s development digest, we discuss slope surface roughening techniques and why they are a beneficial practice on an exposed slope during construction.

What is slope surface roughening and what is the purpose? Slope surface roughening is the act of roughening up or raking the surface of a slope horizontally to create grooves, bumps, and depressions. These bumps and depressions on the slope serve multiple purposes including:

• Slowing down water velocity flowing down slope
• Trapping sediment that may wash down the slope
• Providing a better base to grow vegetation

Water running down a slope at a high velocity creates the potential for large soil erosion and damage, and by working grooves into the slope, the water is slowed down at every bump it reaches, resulting in a decreased velocity. The same idea is used when talking about trapping sediment. Like flowing water, the grooves and bumps create somewhat of a barrier for sediment moving downhill and some of the sediment gets trapped on the hill, which means the sediment is not flowing into the creeks and streams. Slope roughening is also good for vegetative growth because the depressions create a great place for the vegetation to establish. A flat, compacted slope creates a difficult surface for the vegetation to establish, and by providing depressions and loosening up some of that soil, the vegetation is more likely to survive and provide ground cover. In fact, according to the Ohio Rainwater and Land Development Manual, any slopes that are steeper than 3:1 are required to be grooved or tracked if vegetation will eventually be installed, so you might as well create those grooves before construction starts for soil erosion control as well!
 
Two main methods to roughen the slope are commonly used:

• Dragging a bucket with teeth along the slope
• Driving tracked machinery horizontally across the slope
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Using a bucket with teeth to drag along the slope is a very simple and effective method to create the grooves and depressions needed to slow down the water velocity. Using tracked machinery is also a good method that can lead to uneven grooves along the slope that will also help slow down water velocity. Both methods can be an effective way to roughen up the soil, however the track method may not be as good of an option depending on the soil because it could lead to soil compaction, which would not be good for vegetative growth. It is best to determine the soil type before choosing one of these methods.
 
Slope surface roughening is a tried and proven practice that works effectively to assist in the battle against soil erosion and water runoff. Whether using a bucket with teeth, equipment tracks, or any other method that roughens the slope, the creation of the grooves and depressions is a great practice to protect the soil and the water during the construction phase of a project. More information and specifications can be found in the Ohio Rainwater and Land Development Manual which is linked below.
 
Have questions about this practice, other best management practices, or other questions in general? Feel free to reach out to our office by calling us at (513) 695-1337 or emailing at [email protected].
 
Ohio Rainwater and Land Development Manual: https://epa.ohio.gov/wps/portal/gov/epa/divisions-and-offices/surface-water/guides-manuals/rainwater-and-land-development
 
Article Written by Seth Byerly, Urban/Ag Technician