Formation of parabolic dunes on the shore of Poyang Lake in East China

Abstract

Parabolic dunes can transform from and into other types of dunes in response to environmental changes. The sand hills, including some parabolic dunes, on the shore of Poyang Lake mainly accumulated during the Last Glaciation and are rare inland aeolian landforms in the humid monsoon climate zone in East China. However, the characteristics, distribution and formation of the parabolic dunes in this region are still not clear. Three sand hills with similar scales and wind regimes at Shaling, Jishan and Songmenshan were selected as the research targets. Integrating topographical, hydrological, vegetation and wind data, we found that the development of the parabolic dunes was effectively controlled by both the vegetation cover of the sand hills and the space available downwind of the sand hills. No parabolic dunes were found at Songmenshan and Shaling; the former has too little vegetation cover, favouring the formation of blowouts, and the latter lacks available space since Shaling is surrounded by villages and farmlands. Three types of parabolic dunes that developed sequentially in the downwind direction, namely, type A, type B and type C dunes, are observed at Jishan, and their formation is related to a narrowly unimodal and high-energy wind regime. Different from existing models, type A dunes are found to originate from the wedge-shaped depositional lobes of trough blowouts; type B dunes transform from type A dunes after migration; and type C dunes develop from very low sand drifts. Composite parabolic dunes are formed when the sand supply is plentiful, while simple parabolic dunes appear when the sand supply is limited. The formation of the parabolic dunes occurred approximately 250 years ago, which is close to the documented time when the sand hills were reactivated due to the vegetation being anthropogenically damaged. Therefore, anthropogenic destruction of vegetation is a trigger for producing parabolic dunes in this humid area. This study may shed light on the evolution of aeolian landforms in humid monsoon climate zones.