At the back of our garden is a high rocky area. It makes a great back wall – beautiful, fun to climb, and a sanctuary for lots of birds, geckos and plants. When it rains, the water rushes off these rocks and erodes a lot of soil from the gently sloping field at the foot.
One technique that is used to prevent erosion is digging swales and building berms – that is, digging a ditch and piling the mud next to it on the downhill side. The water rolling downhill lands in the ditch, soaks into the ground under the berm, watering trees or shrubs that are planted in the berm, and soaking into the water table. The water is slowed down as it goes downhill so that the land can benefit from it, and so that the soil is not eroded.
Another permaculture technique that involves making hills is Hugelkultur – farming in a hill. The hill is made by piling branches or tree trunks and putting soil and plants over then. The wood breaks down, supplying nutrients to the plants, and it also absorbs water like a sponge which it stores for the plants to access even in times of drought.
A principal of permaculture is that each element should perform many functions. So, I am combining hugelkultur and swales/berms to slow down water off the rocks at the back of the garden. I’m calling it a Hugelberm!
In a recent storm, a tree fell down quite near this area, which was handy!
the garden, chopped the branches off so I could use them for the Hugelberm.
These are the useful wild plants that I transplanted from the base of the rocks to the top of the Hugelberm.
Finally (for now) I covered the berm with some straw from my goat house, rich in urine and goat manure. This is to stop the soil being washed away the next time it rains.
-Observe and photograph the Hugelberm in a rainstorm and adapt as necessary.
-Build up the soil and plant life on the Hugelberm, possibly adding other plants like bananas.
-Build up the soil downhill from the Hugelberm by covering the exposed rock with compost.
-Observe the effectiveness of the Hugelberm to 1) slow water 2) prevent soil erosion 3) act as a source of water to trees planted in it throughout the dry season 4) act as a green barrier in the face of bushfires coming down from the rocks in the dry season.
UPDATE 11th Sept 2015
The week after the Hugelberm was finished, we had some showers of rain, but then on Friday 11th we had a huge storm which gave me the opportunity of photographing the ditch at full capacity – it works!
On the right of each photo you can see how the rain washing down the rocks is being held back in the ditch rather than rushing across the cornfield. It will seep gently under the Hugelberm and soak down into the water table. There were a few leaks on the downward side which I will plug with some more soil and possibly rocks, but on the whole, I was very pleased at how it held the water back in such a big storm.