Problem
On sloping land, erosion caused by runoff can kill the soil. It also creates uneven distribution of rainwater over the land, which naturally does less for plant life than it could if it were unevenly distributed.
Solution
On all land which slopes—in fields, in parks, in public gardens, even in the private gardens around a house—make a system of terraces and bunds which follow the contour lines. Make them by building low walls along the contour lines, and then backfilling them with earth to form the terraces.
Related Patterns
… this pattern helps to complete Site Repair (104). Where there are buildings, it ties into the Building Edge (160) and can help form it; and it helps create the Connection to the Earth (168). If the ground is sloping at all, this pattern tells you how to handle the slope of the ground in a way that makes sense for the people in the building, and for the plants and grasses on the ground.
Plant vegetables and orchards on the terraces - Vegetable Garden (177), Fruit Trees (170); along the walls which form the terraces, plant flowers high enough to touch and smell - Raised Flowers (245). And it is also very natural to make the walls so people can sit on them - Sitting Wall (243) …
Alexander, Christopher. A Pattern Language: Towns, Buildings, Construction. Oxford University Press, 1977, p. 790.