Short term sediment accumulation rates reveal seasonal time lags between sediment delivery and deposition in an oxbow lake

Abstract

Recent sedimentation rates are useful for quantifying how changes in a watershed affect soil erosion; however, typical geochronological methods for dating sediments are limited in temporal resolution, particularly for newly deposited sediments. We used sediment traps to measure short-term sediment accumulation rates in a natural oxbow lake whose watershed has a mix of agricultural and forested land. Precipitation data from a local Soil Climate Analysis Network (SCAN) site and water quality measurements from Beasley Lake were used to explain intra-annual patterns in sediment deposition. We found that sediment accumulation in the traps was highest in July and August, while the highest rate of runoff, indicated by increased precipitation and total suspended solids, occurred in late winter and early spring (February-April). Our results indicate that the trapping efficiency of Beasley Lake may be lower than expected due to timing of particle settling predominantly in the summer months. The rate and timing of sediment accumulation in Beasley lake was highly seasonal and occurred when water temperature and pH increased, potentially through interactions with algal blooms. Our findings contribute new understanding of the interactions between suspended sediments, algal biomass, and water chemistry in a natural oxbow lake and provide support for using sediment traps to measure intra-annual variability in sedimentation rates in oxbow lakes.