Overall efficiency of a V-shaped nylon net fence inpreventing sand damage to the Mogao Grottoes

A V-shaped nylon net fence installed in 1990 on top of the Mogao Grottoes is shown to be effectively resisting aeoliansand damage to the grottoes. The structure guides and causes deposition of sand from westerly wind (the primary hardwind), but to some extent hinders the inverse function of easterly wind carrying sand away from the grottoes towardMount Mingsha. The gobi side by the fence experiences higher wind speed, so that on which are easily formed undercuttingpits, and the deposited sands on it generally form double-peak structures due to abundant sand sources. If theearth surface characteristics in gobi areas by both sides of the fence are quite varied, the erosion and deposition featuresof the accumulating sand section are similar in different seasons; however, if the earth surface characteristics are similar,the features become irregular in different seasons. Sand depositions with long slope feet are formed along the south andnorth sides of V-shaped nylon net fence. Disrupted by strong westerly wind and northwesterly wind, sand accumulationsby north of the fence are in form of single peaks. Although the operation duration of the V-shaped nylon net fence hasexceeded its design life (10 years), our observations indicate that it is still effective in reducing wind-driven sanddamages to the Mogao Grottoes, so it should not be withdrawn.