Abstract
Wind and sand control features are important tools for limiting desertification. Sand barriers are one of the oldest engineering measures used to reduce wind-sand hazards. Their efficacy and exact mechanism by which they work has remained a topic of scientific debate however. Sediment grain-size distributions can help constrain their utility and function. This research analyzed sediment grain size distributions in samples collected from areas around six different types of sand barriers installed along the southeastern margin of the Tengger Desert. Results were compared with sediment from a bare dune area (no barriers) used as a control. The barrier area samples contained high proportions of coarse sand and relatively low proportions of silty sand and very fine sand. Fine and medium sand were present but clay was not. The lower proportions of fine sand and higher proportions of coarse sand relative to bare dunes documented an effective reduction in aeolian transport by the barriers. Samples from the barrier areas also showed poorer sorting relative to bare dune areas. This appeared as lower kurtosis values and wider frequency distribution curves relative to those measured from bare dunes samples. The wider cumulative frequency curves for samples from the barrier areas likely reflects the higher proportion of coarse-grained material. The Straw/1.5 and PLA/1 barrier types hosted greater sediment accumulation than that observed for the other barrier types (Straw/1, PLA/1.5, Mixed/1 and Mixed/1.5). Sediment grain size distributions showed that the base and middle slope areas of the dune experienced deposition, while the top of the dunes experienced erosion. The Straw/1 barrier (straw installed as a 1 × 1 m grid) performed best in terms of installation costs and protective effects for the study area. This study demonstrates how sediment grain size distributions can be used as quantitative proxies for sand barrier performance in reducing desertification.
Highlights
Wind and sand control features are important tools for limiting desertification
Mechanical sand barriers cause a blocking effect that increases the percentage of medium to coarse sand and decreases the percentage of fine sand to cause an overall coarsening of surface sediments[14,15,16]
Mechanical sand barriers installed along marginal areas facing the prevailing wind direction can effectively prevent aeolian desertification
Summary
Wind and sand control features are important tools for limiting desertification. Sand barriers are one of the oldest engineering measures used to reduce wind-sand hazards. This research analyzed sediment grain size distributions in samples collected from areas around six different types of sand barriers installed along the southeastern margin of the Tengger Desert. Adjacent studies of the Tengger desert have interpreted wind-sand flow, particle size distributions and the effectiveness of protective measures. Nearby bare dunes served as a control area for determining the effects of different sand barriers types on sediment grain size distributions as they relate to the different sedimentary processes of erosion, transport and deposition. This research sought to (1) study the effects of three different types of mechanical sand barriers on surface sediment grain size distributions, (2) quantify variation in wind-sand flow and spatial distribution of sediment around sand barriers and (3) determine the protective efficiency of different types of sand barrier for large scale mitigation efforts. This research can inform mitigation efforts in arid environments experiencing desertification and in coastal areas under developmental stress
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