A Study Of Dune Morphology And Its Evolution Based On High Resolution Remote Sensing Data

Based on the 1.5m spatial resolution of SPOT satellite data in August 2013 and September 2015,the period of the wild topographic survey data and wind data,analyzed the parameters of the relationship between morphological characteristics,the form of dunes,and dunes moving speed,direction and mode,drift potential sediment size and direction and its influence on the direction of the sand flow in the right flank of Xiangshui river middle reaches,Inner Mongolia.The study of dune morphology and its evolution characteristics,contributed to understandingandcomprehensionthegeneralmorphological characteristics and movement rules of the active sand dunes in Horqin Sandy Land,the study has theoretical and practical significance to the sand control and sand dunes group management.The result shows that:(1)In study area the number of dune crest lines was 94 in 2013 and83 in 2015,reduced by 11.7%.The total dune crest length decreased from2.23 x 10~4m in 2013 to 2.20 x 10~4m in 2015,however,the average crest length increases by 28.43m.The defect density of dune complex es decreased from 0.0042 in 2013 to 0.0037 in 2015,dune spacing increased from 137.34 to 138.93 during the period.These parameters show that the sand dunes are merged with other sand beds during it's moving,the crest length is prolonged and the number of the dunes is reduced by combined sand dunes.(2)The dunes in study area is made up of 7 dune complexes which orientation is NE-SW,length is unequal and parallel distribution,each dune complex is composed of 2-3-shaped crescent dune chains,the types of sand dunes above the dune complexes are mainly composed of single crescent dunes and longitudinal dunes.The width and the height,leeward slop length and width of sand dunes are moderate positive correlation.Therefor,leeward slop length and height as a week positive correlation.(3)During 2013 to 2015,the sand dunes did not appear to the expansion trend to northeast and southwest,under the southwest and northeast wind the dunes expand to ESE direction.Some changes have taken place in the 7 dune complexes,the increase of the dunes-crest-line curvature and the lateral extension connected with other dunes are the mainly forms.(4)In study area the dunes migrate speed is 6.736-10.03m/a,the type is fast moving sand dunes.The first dune complex due to the height and volume the larger than others it migrate speed is 6.736m/a,the second dune complex moving speed is 10.03m/a which speed is the fastest,the third to seventh dune complexes migrate speeds are closed which between 7.11-7.981m/a.The sand dunes in south of the dune complexes move faster than which in the north,the speed difference is between0.04m-2.982m/a,the reason may be the first dune complex is formed a354 m gap on the south where the wind is greater than the north side,and the sand source is sufficient,promote the rapid movement of dune.(5)In spring NW and WNW direction wind are the highest frequency of sand-driving wind in Xiangshui River middle reaches right flank,account for 46.43%of sand-driving wind,the proportion of SSW wind was 14.63%,the other 13 directions are lower.Drift Potential is given priority to NW and WNW direction,which showed that the sediment transport capacity of WNW and NW directions was the strongest,it's in accord with sand-driving wind.Combined with the direction of the dunes moving statistics which is about 125 degrees,so the dunes migrate in ENE direction.(6)Under the action of sand-driving wind the wind ripples which on the windward slope moving forward by the form of wave,the dune complexes migrate forward by parallel passes.Comprehensive the migrate speed,direction and patterns,regional environment and wind energy,the sand dunes in the right flank of Xiangshui river middle reaches showing a trend of expansion to the ENE direction,and the expansion trend has serious threat to the east of vast pasture.