Geomorphologic patterns of dune networks in the Tengger Desert,China

Dune networks are widely distributed in the world＇s deserts,which include primary ridges and secondary ridges.However,they have not been sufficiently studied in a systematic manner and their origins and spatial and morphological characteristics remain unclear.To provide information on the geomorphology of dune networks,we analyze the software geomorphologic patterns of the dune networks in China＇s Tengger Desert using matrix and laboratory to process remote-sensing images.Based on analysis of image features and their layout in a topographic map,we identify two types of dune networks （square and rectangular dune networks） with different size and morphological structures in the Tengger Desert.Four important geomorphic pattern parameters,ridge length,spacing,orientation and defect density,are analyzed.The length of primary ridges of dune networks decreases from northwest of the desert to the southeast,resulting an increasing spacing and a transition from rectangular dune networks to square dune networks.Wind regime and sediment supply are responsible for the variation in pattern parameters.We use the spacing and defect density data to estimate the construction time of dune networks and found that the dune networks in the Tengger Desert formed since about 1.3 ka BP.

Morphological Profiles of Sand Dunes from ICESat-2 Geolocated Photons

Aeolian process leads to the transportation and accumulation of sand particles that result in sand dune landforms. The structure and shape of the sand dunes are driven by the parameters of interacting wind force and the material composition of sand within. Cross-section profiles over the sand dunes will essay the geomorphological parameters through which the steady state and rate of sand transport can be computed. National Aeronautics and Space Administration’s novel satellite namely Ice, Cloud and land Elevation Satellite-2 (ICESat-2) hosts a solo sensor namely Advanced Topographic Laser Altimeter System (ATLAS) which is a photon counting instrument that measures the round-trip time of the light pulse being emitted and reflected back from the surface determines the true height of the topographic feature on the Earth. In this article, cross-section profiles generated from the beams of ICESat-2 ground-tracks acquired over sand dunes of the Thar Desert region were analysed for detecting the geomorphological parameters. Observations from the cross-section profiles have resulted in giving unprecedented details about the shapes and morphological settings of various types of sand dunes like barchanoids, parabolic, longitudinal, and transverse dunes. Morphological parameters of sand dunes like the length of the stoss slope, crest height, slip face details, inter-arms spacing, height of the trailing arms, length of the depositional lobes, and sinuosity of the recurring crest lines were retrieved with ease from the Level-2A data product namely ATL03 of ICESat-2/ATLAS.

Planform characteristics and development of inter- channel wetlands in a gravel-bed anastomosing river, Maqu Reach of the Upper Yellow River

Both interchannel wetlands and multi-channels are crucial geomorphologic units in an anastomosing river system. Planform characteristics and development of interchannel wetlands and multi-channels control the characteristics of anastomosing rivers. To under- stand the role that interchannel wetlands play in the development of anastomosing rivers, a study was conducted on the Maqu Reach of the Upper Yellow River （MRUYR）, a gravel-bed anastomosing river characterized by highly developed interchannel wetlands and ana- branches. Geomorphologic units in the studied reach were extracted from high resolution satellite imagery in Google Earth. The size distributions of interchannel wetlands and inter- channel wetland clusters （IWCs）, a special combination of interchannel wetlands and ana- branches, were investigated. Geomorphologic parameters, including the ratio of interchannel wetland area to IWC area （P）, shoreline density （DL）, and node density （Dn） were used to analyze planform characteristics of IWCs and the development of multi-channels in the stud- ied reach. The results suggest that small or middle sized interchannel wetlands and large or mega sized IWCs are more common at the study site. The area of IWC （Su） is highly cor- related with other geomorphologic parameters. P increases with increasing Su, and the upper limit is about 80%, which indicates that the development of interchannel wetlands and ana- branches in the IWC is in the equilibrium stage. In contrast, D~ and D, show a tendency to decrease with increasing Su due to diverse evolution processes in IWCs with different sizes. There are three main reasons leading to the formation of IWCs： varying stream power due to the meandering principal channel; development of the river corridor due to the weakening of geologic structure control; and high stability of interchannel wetlands due to conservation by shoreline vegetation.