Mud and sand dynamics as revealed by wavelet analysis

What is it about?

Understanding suspended sediment dynamics and their controlling factors is essential for successful watershed management. The spatiotemporal patterns of suspended sediment were examined over a 20-year period for small, nested watersheds with diverse land-use and widely different channel boundary materials. It has been shown that an overall decrease in fines (silts + clays) and sand loads over seasonal and annual time scales is due to the decreased cultivation, which led to less frequent erosive flows. However, the spatiotemporal patterns of sediment concentration are more complicated. While fine sediment concentration (FSC) patterns reflect how watershed and channel conditions interact (e.g., pond locations, presence of gullies, and in-channel sediment storage), sand concentration patterns reflect channel state, which depends on bank materials, riparian vegetation growth stage, and in-channel sand availability. Additionally, we found that sandy channels were less sensitive to erosion control measures than gravelly channels, suggesting that they were major sources of fine sediment. As cultivation decreased upland of gravelly channels, peaks of sediment concentration signal lagged those of flow, indicating a shift in sediment supply mechanisms. Wavelet analysis can be utilized to detect complex patterns embedded in sediment time series. Thus, it can be used as a tool for evaluating sediment reduction measures.

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Photo by Jeremy Bezanger on Unsplash

Photo by Jeremy Bezanger on Unsplash