Deriving bottom sediment grain size in tidal channels using remote sensing and numerical modeling

Abstract Bottom sediments in tidal estuaries influence organic matter and nutrient cycling, habitat suitability, and geomorphological processes. Characterizing the grain size distribution of bottom sediments is essential for predicting sediment transport, channel stability, and ecosystem health. However, this information can be challenging to acquire over large areas as traditional in situ approaches provide only point‐based observations that are spatially limited. This study addresses this limitation by applying the sediment balance equation to remotely sensed maps of total suspended solids concentration and numerical model outputs to derive a high‐resolution, spatially explicit sediment grain size distribution within a tidal channel of a New England mesotidal estuary. Results reveal a distinct gradient in sediment grain size, with coarse sediments near the inlet transitioning to finer sediments landward. Fine sand covers over 85% of the channel bottom, while medium and coarse sand occupy 14% and 1%, respectively. Peaks in settling velocity identify zones of sediment convergence controlled by tidal forcing and river inflows. The positive correlation between , estimated through the depth integrated suspended sediment continuity equation, and bottom grain size confirms the effectiveness of this approach for sediment classification in estuarine environments.