Efficiency of wind erosion control measures along Cuona Labe on Qinghai-Tibet railway, western China

The Geerm-Lhasa section of the Qinghai-Tibet railway starts from Geerm City in Qinghai Province,stretches southwards along the Qinghai-Tibet road and reaches Lhasa City of Tibet.The railway is 1 140 km long and suffers from wind erosion for a range up to 260 km.Wind erosion seriously endangers the safety of railway operation. A comprehensive defense system,combining the upright-concrete sand fence,stone checkerboard sand barriers and gravel mulch along Cuona Lake, Ando County of the Tibet Autonomous Region,was selected to evaluate the efficiency of wind erosion control measures based on field investigations of wind speed and the amounts of sand discharged.Three pieces of upright-concrete sand fences were arranged towards windward,with the stone checkerboard sand barriers and gravel mulch alternately arranged to leeward.Upright-concrete sand fences greatly decreased the amount of sand discharged and wind speed compared with that of control.In the middle region between the first and second structures as well as between the second and third structures of the upright-concrete sand fences,the sand discharge ratios were 28.00% and 0.70%,i.e.a reduction of 72.00% and 99.30%.Behind the first structure of upright-concrete sand fence,wind speed decreased by 35.54% to 92.82%,by 8.66% to 92.98% behind the second upright-concrete sand fence,and by 26.84% to 90.13% behind the third upright-concrete sand fence.Stone checkerboard sand barriers and gravel mulch also greatly reduced the amount of sand discharged.Behind the third upright-concrete sand fence,at distances of 50 and 150 m,the sand discharge ratio at the stone checkerboard sand barriers were 0.59% and 0.24%,respectively,and 0.53% and 0.25% at the gravel mulch at distances of 100 and 200 m.