Drivers and compounding factors of temporal sedimentation rate variations over the past 100 years in a human‐impacted mountainous catchment, Korea

Sediment profiles of various sedimentary environments can provide important information on hydrological changes in watersheds, including the impacts of human activities, precipitation and other factors. In this study, fluctuations in sedimentation rates in the Sijeon Stream, which flows through the Sajapyeong wetlands in Korea, were reconstructed using 210 Pb dating of sediment cores collected from slackwater deposits, which yielded dates of the years 1912–2019. These reconstructions were used to identify the key watershed factors driving sedimentation rate changes. The results indicate three distinct periods with distinct sedimentation properties: Period 1 (1912–1963), Period 2 (1969–2000) and Period 3 (2001–2019). These periods align with the following three land‐use phases, as reconstructed through the analysis of aerial photographs and satellite images: (i) a quasi‐natural phase (up to the early 1960s), (ii) an intensive agriculture phase (mid‐1960s to mid‐1990s) and (iii) a multiple anthropogenic intervention phase (early 2000s onwards). Notable correlations between sedimentation rate and precipitation were observed during each period. In particular, the rapid and continuous increase in sedimentation rate after 2015 (i.e., the latter part of Period 3) was attributed to the occurrence of artificial channel modifications and earthquakes. These results demonstrate that changes in land use exert long‐term influences on sedimentation rates in streams, whereas precipitation, artificial channel modification and earthquakes have relatively short‐term effects. Moreover, it was shown that when these three factors occur simultaneously, their impacts can be compounded and amplified, potentially resulting in a significant increase in the sedimentation rate. These results are expected to enhance the understanding of the temporal effects of various watershed factors on sediment transport and contribute towards effective watershed soil management for sustainable reservoir and wetland maintenance.