Quantitative analysis on the dynamic characteristics of megadunes around the Crescent Moon Spring, China

The Crescent Moon Spring is a precious natural heritage. However, the dynamic characteristics of megadunes around the Crescent Moon Spring are not well known. This paper quantitatively studied the character- istics and changes of megadunes around the Crescent Moon Spring by interpreting aerial photographs taken in 1985 and 2004 and analysing the dune crestlines and the wind data collected from 2011 to 2012. Results revealed that pyramid dunes were formed by a complex wind regime. The Crescent Moon Spring was not buried by shifting sands because of the stable wind regime and relative stability of pyramid dunes. The crestlines of the dunes around the spring moved northward between 1985 and 2004. The south-facing slip faces were also exposed to wind ero- sion, whereas the other faces were under deposition, thus indicating that the southerly wind was relatively en- hanced. Limiting the scale of tall windbreaks and architectures in the Dunhuang oasis at the north of the spring was necessary to maintain the dynamic equilibrium of the wind regime and sand transport.

Effects of gravel mulch on aeolian transport:a field wind tunnel simulation

The shape,size and coverage of gravels have significant impacts on aeolian sand transport.This study provided an understanding of aeolian transport over the gravel mulching surfaces at different wind velocities by means of a mobile wind tunnel simulation.The tested gravel coverage increased from 5% to 80%,with a progressive increment of 5%.The gravels used in the experiments have three sizes in diameter.Wind velocities were measured using 10 sand-proof pitot-static probes,and mean velocity fields were obtained and discussed.The results showed that mean velocity fields obtained over different gravel mulches were similar.The analysis of wind speed patterns revealed an inherent link between gravel mulches and mean airflow characteristics on the gravel surfaces.The optimal gravel coverage is considered to be the critical level above or below which aeolian transport characteristics differ strongly.According to the present study,the optimal gravel coverage was found to be around 30% or 40%.Threshold velocity linearly increased with gravel coverage.Sand transport rate first increased with height above the wind tunnel floor（Hf）,reaching a peak at some midpoint,and then decreased.

Progress on research and mitigation of wind-blown sand risk in Dunhuang Singing Sand Mountain and Crescent Spring Scenic area,China

The Singing Sand Mountain and Crescent Spring Scenic Spot in Dunhuang,Northwest China is a world-renowned desert attraction that is also an integral component of the Dunhuang UNESCO Global Geopark.This scenic area underwent a 30-year transformation,i.e.,from a severe sand risk with spring water threatened by sand burial due to dune deformation,to restoration of the original sand flow field and mitigation of the sand burial problem.The current paper summarizes the research on the intensive monitoring of the dynamic change of star dunes near the spring,observation of wind and sand flow movement,and then restoring the harmonic vibration of the sand particles(singing sand)that were previously silenced.The existing and prospective impacts of anthropogenic and natural forces on the deformation of the sand dunes are investigated by integrated methods,guiding the implementation of mitigating measures with significant ameliorative effects.Contrast to common sand control practices that aim to reduce wind speed and stop blown sands,our research highlights the importance of maintaining the natural wind flow field in stabilizing surrounding dunes.These mitigation measures consist of removing excessive vegetation and newly constructed buildings to recover the original wind flow field and sand transport activity.Such research and mitigation efforts ensure the scientific protection and restoration of the special desert landform,and contribute to the mutual enhancement of the conservation and exploitation of this desert scenic spot and similar sites.

Aeolian processes on sandy desertification of an alpine meadow: A wind tunnel experiment

In recent years,the desertification of alpine meadows has become a serious ecological problem and has gradually become a threat to regional economic activities in Maqu County.To reveal the mechanism for sandy desertification of alpine meadows,we conducted wind tunnel experiments on aeolian processes over sandy alpine meadows.Results show that the sandflux profile of mix-sized sediment decays exponentially with increasing height.However,the profile pattern of a group of uniform-sized particles depends on the experimental wind speeds.The profile pattern of all the groups studied can be expressed by exponential decay functions when the wind speed is less than or equal to 16 m/s.while that for all the groups studied can be expressed by a Gaussian distribution function when the wind speed is above 16 m/s.The average saltation heights of mixed sands at wind speeds of 12 m/s,16 m/s,20 m/s,and 24 m/s were 2.74,4.19,5.28,and 6.12 cm,respectively.The mean grain size basically first decreases and then increases with increasing height under different wind speeds.The sorting improves with increasing wind speed,while the kurtosis and skewness show relationships with only the characteristics of the parent soil.