Erosion Control

[martin888888]

Erosion control blankets are good to stabilize steep slopes to avoid runoff to natural areas. Are they needed in areas like steep slopes within a landfill or the slopes of the internal side of a detention pond, etc.?

 

[Ron]

They are often used for slopes in retention/detention facilities. I have specified them several times for that purpose and for slopes leading to other bodies of water.

 

[cvg]

two kinds of mats are available.

Type 1 (cheap) is used to provide minimal erosion control and mostly helps the vegetation to become established. Seeding is required and the vegetation provides the erosion control. Hydroseed / hydromulch might be a good alternative.

Type 2 (expensive) is a turf reinforcement mat which provides considerable erosion control, even without any vegetation. Seeding and mulching are required.

 

[francesca]

Runoff is going into natural areas regardless. Erosion control blankets stop the erosion and sediment being transported. I can't count the number of detention basins I've seen with gulleys down the side. In a good (e.g. 1 yr return period) storm it doesn't take much to get the velocity required to erode a 3:1 slope... maybe 3 feet. The sediment collects in the bottom of your pond reducing the storage volume. It's a toss-up between sod and a blanket for cost. Sod is cheaper depending where you are and the season.

 

[cvg]

sod is only cheaper if you don't have to mow it. However, goats work cheap

 

[civilman72]

Generally speaking slopes at 4:1 or more gradual should not need blankets. Anything steeper than that, than the soil types, water sources and monitoring schedule should be considered. A good granular soil will limit surface erosion and encourage quick vegetation. A clay soil will erode quickly and will not naturally vegetate quickly. If you can continuously water the slopes and provide regular maintenance/repair of minor slope failures, then slopes steeper than 4:1 may not require blankets.

But most of the time our clients do not maintain the slopes, do not irrigate the slopes, and we very rarely are dealing with non-erosive soils. So, unless you have a project with those unique characteristics, blanketing all soils steeper than 4:1 is a good practice.

 

[msucog]

if the slope is fill, the fill slope should be properly constructed otherwise it's only a bandaid on the problem.