Sediment dynamics in a large shallow lake characterized by seasonal flood pulse in Southeast Asia

Highlights: • Tonle Sap Lake is a large and shallow lake influenced by a flood pulse system. • Sediment dynamics were investigated in this lake and its floodplain vegetation. • Floodplain vegetation showed a reduction of sediment resuspension. • Tonle Sap Lake had two distinct characteristics: sink and source of the sediment. Most of studies on sediment dynamics in stable shallow lakes focused on the resuspension process as it is the dominant process. However, understanding of sediment dynamics in a shallow lake influenced by flood pulse is unclear. We tested a hypothesis that floodplain vegetation plays as a significant role in lessening the intensity of resuspension process in a shallow lake characterized by the flood pulse system. Therefore, this study aimed to investigate sediment dynamics in this type of shallow lake. The target was Tonle Sap Lake (TSL), which is a large shallow lake influenced by a flood pulse system of Mekong River located in Southeast Asia. An extensive and seasonal sampling survey was conducted to measure total suspended solid (TSS) concentrations, sedimentation and resuspension rates in TSL and its 4 floodplain areas. The study revealed that sedimentation process was dominant (TSS ranged: 3–126 mg L⁻¹) in the high water period (September–December) while resuspension process was dominant (TSS ranged: 4–652 mg L⁻¹) only in the low water period (March–June). In addition, floodplain vegetation reduced the resuspension of sediment (up to 26.3%) in water. The implication of the study showed that resuspension is a seasonally dominant process in shallow lake influenced by the flood pulse system at least for the case of TSL.