Technique of the Week: Hagg Reprofiling
The second entry to our new ‘series’ of blogs and content here at CCC – every so often we’ll talk about a peatland restoration technique in a short blog, shedding light on what is a very unknown subject. Check out the first ToTW, Plastic Piling, here.
A quick recap: why do we need to restore peatland?
Peatland is a hugely important habitat for so many reasons – take a look at our blog here which talks about a few.
Damaged peatland can worsen climate change due to the carbon released, increase flood risk, decrease the quality of water downstream, and threaten many rare, highly adapted species.
On degrading peatlands, sometimes features can develop due to erosion by weather, stock, and water flow. One of these features is the hagg (see above).
A hagg is a bare face of peat, fairly steep and almost like a mini cliff. These are often eroded further by stock which shelter against the wind here, and rub more of the oxidised peat away.
It’s hugely important to treat bare peat due to the high rates of erosion within these features. This type of restoration is primarily to stop this erosion and encourage revegetation rather than to improve the hydrology of the area, like the plastic piling aims to do.
Although the specifics will change based on the site, generally the hagg will be reprofiled so it is less steep (typically 30-35 degrees maximum), and then fresh, healthy turves will be borrowed (usually from a nearby area, which is then reinstated by ‘stretching’ the healthy turves from around the borrow pit to cover any bare peat left) and placed onto the hagg.
Turves are laid bridging the break-in-slope at the top of the hagg, typically by an excavator on low pressure tracks with a toothed bucket. This prevents slumping, as otherwise water can get behind the turves and “wash” the fresh turves down the slope.
In this technique it is important to make sure the turves are compacted so they knit together properly and remain stable, and that the turves are fairly deep so they have a healthy root system and can survive in their new home.
In addition to this reprofiling, contractors may need to ask why this feature developed and take steps to combat these pressures – is the path of water simply going to erode any restoration work done? Will high densities of stock move through the area and damage the restoration work unless given a suitable crossing point? What other measures need to be taken to protect the restoration area?
Hagg reprofiling can be a big win in terms of visual improvements and erosion reduction in a fairly short space of time.