Suspended Sediment Transport at North Campus Open Space: Freshwater Inputs in the 2023 Water Year

Coastal wetlands provide essential ecosystem services and are important sinks for atmospheric CO2. With climate change and sea level rise, coastal wetlands are threatened. Studying sediment accretion rates is important for predicting a wetland's resilience to sea-level rise. Sediment accretion, driven by local sediment availability contributes to the vertical growth of a wetland, which is important for the wetland to be able to keep up with rising sea-level. Sediment can accumulate in a wetland from a variety of sources, one of the most important being freshwater tributaries which bring sediments from the local watershed into the wetland system. This study focuses on two freshwater tributaries, Phelps Creek and Whittier Channel, which drain into Devereux Slough, the larger wetland system whose upper portion is located in University of California, Santa Barbara’s North Campus Open Space (NCOS), and their potential for contributing to the restored wetland’s sediment accretion. We processed stormwater samples from both streams in the laboratory to obtain their suspended sediment concentrations for the 2023 water year. Analysis of samples showed a higher concentration of suspended sediments in Phelps Creek when compared to Whittier Channel. We believe this is because of physical differences in the stream paths of both tributaries and the dynamics of their respective watersheds. Suspended sediment measurement in the solitary wetland output stream needs to be sampled to determine how much sediment is leaving the system and additionally how much of this study’s sediment is remaining in the system. While this study is useful for determining how much sediment was carried into Devereux Slough during the 2023 water year, the study should be extended over a longer timescale to gain insight to how this sediment input is changing over time.