Controlling windblown sand problems by an artificial gravel surface: A case study over the gobi surface of the Mogao Grottoes

In arid regions, gravel surfaces are usually known for protecting the soil from wind erosion, trapping the sand and dust carried by the wind, thereby forming a sink of sediment. However, gravel surfaces with a suitable gravel size and coverage density can also act as the source of sediment under unsaturated wind flow. A dynamically equilibrated gravel surface can be built to prevent potential windblown sand problems in the Dunhuang Mogao Grottoes in northwestern China. Unlike previous studies that suggested constructing a high coverage (50% or more) gravel surface on the gobi land on top of the Mogao Grottoes, a much lower value of 30% is recommended. This kind of artificial gravel surface can protect the underlying sand materials from wind erosion and trap the invading westerly windblown sand. At the same time, the deposited sand over the artificial gravel surface can be transported to the western megadunes by the easterly wind. Under the multidirectional wind regime, the gravel surface can remain from sand burial over the long term.