Gully blocking on the Marsden Moor Estate

Gully blocking on Marsden Moor, West Yorkshire

For 5,000 years peat has been forming below a thin layer of grasses, sedges, rushes and mosses. This vegetation can easily be damaged through overgrazing or quickly removed by fire or through the deterioration of gullies. This bare peat is quickly eroded and will not regenerate without help.

One of the techniques we use to retain the peat is gully blocking. We block the gullies with dams, which help to slow the flow of water, trapping peat and water behind them. This helps to keep the surrounding peat wet and therefore more stable, providing better conditions for re-vegetation in the cloughs. Similar work on other moorlands has also suggested that keeping the moors wetter also has positive benefits on moorland bird populations.
 
Different types of dam are used depending on the ground condition and the angle of the slope. At White Moss, on the southern side of the estate, we have shallow pans of water and the slopes are a very low gradient. We use heather bales here which act as a filter for the peat in the water. All the bales are airlifted out onto site to avoid damaging the ground and then moved by hand to where they are needed. Slots are dug for the bales to fit in and then the peat firmed up against them. On steeper sections we may use stakes to keep them in position.
 
At Buckstones in the north, we have constructed wooden dams as the gullies are much deeper and the gradient is steeper, so the risk of the bales being washed out is increased. Instead, they are made up of two posts driven into the gully and then planks of wood nailed into position. Each dam has a slot cut out to let the water flow over the dam and a splash board to disperse the water which could otherwise cause erosion. There can be over twenty dams in a gully, all helping to hold back the water and collect the peat. On Wessenden Moor there are also lots of dams made of stone, which are useful for trapping sediment in gullies that are quite highly eroded.
 
If you are out walking on the Marsden Moor Estate, you are likely to see signs of our on-going conservation work. Gully blocking on White Moss can be seen if walking along the old Pennine Way, and if you are out for a yomp on Buckstones Moss, you'll hardly be able to miss the wooden dams.