Open Geosci. 2018; 10:452–460 Research Article Open Access Zhengyao Liu*, Zhibao Dong, and Xujia Cui Morphometry of lunette dunes in the Tirari Desert, South Australia https://doi.org/10.1515/geo-2018-0035 Received May 23, 2018; accepted July 31, 2018 1 Introduction Abstract: Morphometry and formation processes are key Morphometry and formation processes are key research research problems in the study of aeolian sandy land- problems for the study of aeolian-driven sandy landforms; forms. Based on morphometric parameters inferred from its theoretical basis is that the process determines the form satellite images and the calculation of the drift poten- and the form reflects the process [1]. In different areas, tial (DP), we examined general characteristics of lunette aeolian-driven sand transportation processes are affected dunes in the Tirari Desert, South Australia, along with by different factors, such as varying wind regimes, ecolog- their morphometry and formation processes to determine ical systems, and hydrological systems, which result in dif- how this landform type initially formed and its relation- ferent dune morphology [2]. ship to surrounding linear dune distribution. Results show Australia has the second largest subtropical desert that the morphometric parameters of lunette dunes and area in the world. These deserts are covered by enor- connective lake systems exhibit moderate correlations. It mous, counter-clockwise turbine-shaped linear dunes [3, suggests that the morphology of these dunes is controlled 4], which have subsequently aroused widespread atten- by the lakes. Spatially, the lunette dunes present regular tion and research interest by aeolian geomorphologists. arrangement, and the strike of their alignment are approxi- Much research has been conducted thus far on the mor- mately in accordance with the linear dunes. The calculated phology and formation of linear dunes. For instance, Was- DP implies that the lunette dunes developed under a low- son et al. [5] studied the type, spacing, and orientation of wind-energy environment, which is a wind regime similar linear dunes; Fitzsimmons et al. [4] researched the tim- to that required for the formation of the surrounding linear ing of linear dune activity; and Telfer et al. [6] discussed dunes. Even though, the resultant DP demonstrates that the morphodynamics, boundary conditions, and pattern the summer wind should be responsible for the growth evolution within a vegetated linear dune field. In addition of the lunette dunes. However, accompanied with the re- to linear dunes, Australian deserts are also composed of peated drying of lakes and even its disappearance during transverse dunes and irregular dunes, such as crescent the dune development process, it not only contributes to dunes [7] and lunette dunes [8], but, in general, there the development of lunette dunes but also promotes their has been little research on these dune types [10]. Lunette transformation to linear dunes. dunes are sand dunes that typically form on the lee- ward side and feature a wind-sculpted crescent shape [8], Keywords: Lunette dunes, Morphometric parameters, such as the megadunes and lake systems found in the Drift potential, Tirari Desert, South Australia Badain Jaran Desert in China [10, 11]. Compared to these megadunes, lunette dunes are relatively small and their edges are flanked by a wide range of linear dunes. Thus, why do lunette dunes form around linear sand dunes, and how do they relate to linear dunes? Based on these ques- tions, we selected lunette dunes in the Tirari Desert as the research object of this study. It is hypothesized that this type of dune-lake system is likely to assist in the develop- *Corresponding Author: Zhengyao Liu: School of Geography ment of linear sand dunes, especially in arid climates. As and Tourism, Shaanxi Normal University, No.620 West Chang’an proposed by Hesse et al. [12], in early 25,000 BP water lev- Avenue, 710119, Chang’an District, Xi’an, Shaanxi Province, China, E-mail: [email protected] els in arid areas of central Australia decreased, and the de- Zhibao Dong, Xujia Cui: School of Geography and Tourism, gree of soil salinization subsequently increased, resulting Shaanxi Normal University, No.620 West Chang’an Avenue, 710119, in the formation of clay-rich sandy sediments, which laid Chang’an District, Xi’an, Shaanxi Province, China Open Access. © 2018 Zhengyao Liu et al., published by De Gruyter. This work is licensed under the Creative Commons Attribution- NonCommercial-NoDerivs 4.0 License. Morphometry of lunette dunes in the Tirari Desert, South Australia Ë 453 of Cooper Creek are extreme, being one of the hottest and driest places in Australia. The average annual rainfall is 125 mm; the annual average temperature is 22.6∘C (Fig. 2a), and the interannual variability is very high for both pre- cipitation and temperature [15]. The average wind speed is 4.6 m s−1, which is strong in the winter (5.2 m s−1) and weak in the summer (3.2 m s−1); the strongest winds occur in January and February. The mean sea-level pressure is 1015 hPa, the highest pressure occurring in July (1021 hPa) and the lowest occurring in December (1008 hPa). Despite the harsh environment, this desert still harbors unique biological communities that have adapted to such con- ditions, namely, deep-rooted or xerophilic vegetation, in- cluding Acacia ligulata and Zygochloa paradoxa, and typ- Figure 1: The location of the study area ical Australian desert animals, such as lizards, snakes, in- sects, and koalas [16]. The lunette dunes investigated in this study are located to the north of Lake Koolkootinnie, the foundation for the formation of large-area linear sand which is a large playa lake around Lake Eyre. It is 108.14 km dunes as well as novel and unique geomorphological fea- long with an area of 104.85 km2, having formed by means tures. of palaeodrainage, surrounded by a wide range of lin- In this study, we used data obtained from satellite im- ear sand dunes [17]. These linear dunes are approximately agery to study the morphological characteristics of lunette 5 km long, 30 m wide, and approximately 1 m high. They dunes in the Tirari Desert. The aim of this study was to move in a northwest to southeast direction and slowly east- understand the relationship between this dune-lake sys- ward [18]. tem and try to explain its relationship to linear dunes. This study could provide new information to further discern the formation and evolution of linear dunes in Australia. 3 Materials and methods 2 Regional setting 3.1 Morphological parameters 3.1.1 Parameter measurement The Tirari Desert is located in South Australia and covers an area of 15,250 km2 (Fig. 1). It stretches 212 km from north In this study, we mainly used WorldView-2 satellite to south and 153 km from east to west. The desert is ad- imagery (http://www.zj-view.com) at a resolution of jacent to the Simpson Desert to the north, the Strzelecki 0.5 × 0.5 m and Google Earth images in ArcGIS 10.2 Desert to the southeast, and the Sturt Stony Desert to the (www.esri.com) to draw and measure morphological pa- east. The western, eastern, and northern section of this rameters. Squares were randomly selected in the northern desert is bordered by Lake Eyre, and Cooper Creek flows section of Lake Koolkootinnie, which is situated far from through its interior. Because little research has been con- potential disturbances. The study area is located at 27∘ S ducted on the Tirari Desert to date, some scholars have in- and 137∘ E. In total, the study area is composed of 60 sand cluded it in studies related to the Strzelecki Desert [4, 13], dunes and 60 lakes. We measured the left wing length, while other scholars have regarded it as an extension of right wing length, width, center angle, direction, area, the Simpson Desert [14]. In contrast to these studies, be- and spacing of each dune, as well as the length, width, cause the Tirari Desert exhibits unique hydrological and and area of the lake (Fig. 2). However, due to technical geomorphological characteristics that are distinctly differ- limitations, we did not measure sand dune height. In- ent from those of the adjacent deserts [13], we regarded the stead, we measured the average area of two adjacent sand Tirari Desert as a separate entity. This desert is character- layers according to (area 1 + area 2)/2, which was used ized by large dune fields orientated in a north-south direc- to define the relationship between sand area and dune tion and a myriad of salt lakes in the northeastern and east- spacing [10, 19, 20]. ern sections of Lake Eyre. The environmental conditions 454 Ë Zhengyao Liu et al. Figure 2: Temperature and sea-level pressure of the study area age value, and the stability is better. When the CV is greater than 1, the average amplitude of the change in the thresh- old estimation value is greater than the average value, and the stability is poor. The specific calculation is as follows: s n 1 P 2 n−1 (xi − x¯) σ i=1 C = * 100% = * 100% v x¯ x¯ where n is the number of samples; σ is the standard devi- ation of the samples; xi is the value of the morphological parameter; and x is the average of the morphological pa- rameter. Subsequently, correlation analysis was conducted on the various lunette dune and lake parameters. Finally, the Figure 3: Illustration of the geometric parameters used to study SPSS 24.0 canonical correlation analysis (CCA) feature was sand areas (a, b, c, d, and e) and associated lakes (f and g) used to further reflect the typical variables in the relation- ship between the two variable groups.