Abstract:

Desertification is one of the most severe environmental problems facing human beings, and mechanical sand barriers are a critical measure for sand prevention and control. Taking the plant fibermesh and geotextile bag sand barriers on the migratory dunes at the western edge of the Tengger Desert, northwest China as research objects, three-dimensional laser scanning technology combined with traditional measurement methods was used to measure the microtopography and morphology within the sand barriers. For the most part, MATLAB and RiSCAN PRO were used to analyze the data, describe the surface erosion morphology changes within the sand barrier, and draw the surface erosion morphology map. The results demonstrated the following: (1) The erosion depth, wind erosion amount, and wind erosion surface area of the two kinds of sand barrier all exhibited a gradually increasing trend along the main wind direction. The erosion depth, erosion amount, and surface area of the geotextile bag sand barriers on the ridge’s windward side and at the dune’s midline were larger than those of the fibermesh sand barriers. The erosion depth of the former was 20%-40% deeper than the latter, and the erosion amount was 45%-70% higher. (2) Both sand barrier types showed signs of severe damage in the central and southern parts of the region, where they were 30%-50% higher than in the other areas. Because the geotextile bags were damaged by wind erosion, the scope and degree of the geotextile sand barrier damage were greater than those of the fibermesh sand barrier damage. (3) For the most part, the maximum erosion depth in the sand barrier grid was not located at the grid’s center. The N-NE-E-SE azimuth zone was an erosion and weak deposition zone, and the center and west were a strong deposition zone. (4) The erosion depth of the geotextile sand barrier area was greater than that of the fibermesh sand barrier area, and the damage rate of the fibermesh sand barriers was much lower than that of the geotextile sand barriers. Accordingly, it can be concluded that the fibermesh sand barriers are more durable and effective than the geotextile sand barriers. One previous study found that the maximum erosion depth was not located at the center of the grid. However, the corresponding results on the erosion and accumulation areas differed from the results obtained in this article. The reasons for the difference in results may be the inconsistency in the slope and direction of the dunes as well as deviations in the leading wind direction, sand barrier specifications, and degree of manual intervention. Particularly, these may have resulted in different effects on the wind because of changes in the landform conditions, ultimately leading to the occurrence of the lowest erosion depth position. Still, further exploration and discovery are necessary to determine the sand barrier’s microtopography and morphological erosion rules. For microtopography and morphology inversion, three-dimensional laser scanning technology and the associated software can be used not only to accurately measure the erosion depth but also to calculate the amount of erosion and the surface area of the erosion surface, providing a new model for a detailed study of microtopographies in the fields of wind-sand landforms and sand control tools and methods. Additionally, it can provide a scientific basis for research on the sand-fixing and sand-resisting abilities of sand barriers.

Key words: sand barrier, three-dimensional laser scanning technology, erosion and deposition status, micro-topography morphology, sand blocking effect