Centennial-scale sedimentation dynamics and their controlling factors in a human-modified mountainous catchment, Korea

Sedimentary archives preserved in fluvial and wetland environments offer valuable insights into how watershed systems respond to hydrological variability and human disturbance. Here, we reconstruct centennial-scale changes in sedimentation rates along the Sijeon Stream, which traverses the Sajapyeong wetlands in Korea, using ²¹⁰Pb dating of sediment cores obtained from slackwater deposits. The resulting chronology spans the period from 1912 to 2019 and enables an assessment of the principal watershed controls on sediment accumulation. The reconstructed record reveals three successive intervals that are statistically distinguishable in terms of sedimentation rates: Period 1 (1912–1963), Period 2 (1964–2000), and Period 3 (2001–2019). These intervals correspond closely with distinct phases of land-use history identified from aerial photographs and satellite imagery, including a quasi-natural phase until the early 1960s, a phase of intensive agricultural activity from the mid-1960s to the mid-1990s, and a period marked by multiple forms of anthropogenic intervention beginning in the early 2000s. Across all periods, sedimentation rates exhibit clear associations with precipitation variability. A particularly pronounced and sustained rise in sediment accumulation after 2015, during the late part of Period 3, coincides with the implementation of artificial channel modifications and the occurrence of earthquakes. This pattern indicates that land-use change governs long-term trends in sedimentation, whereas precipitation extremes, channel alterations, and seismic events primarily exert short-lived influences. Furthermore, when these drivers act concurrently, their combined effects can substantially amplify sedimentation rates. The findings improve the understanding of the temporal effects of interacting watershed factors on sediment transport and emphasize the importance of considering these interactions in developing strategies for sustainable reservoir and wetland management.