Dzwonkowski, B.; Wong, K.-C., and Ullman, W.J., 2014. Water level and velocity characteristics of a salt marsh channel in the Murderkill estuary, Delaware.
High-frequency observations of water level and velocity over one year in Murderkill estuary, a tributary estuary of Delaware Bay, are used to examine changes in tidal and subtidal flow characteristics as water propagates from the mouth of the estuary (Bowers site) into a minor channel that connects to a contiguous salt marsh (channel site), a setting where long-term continuous data sets are uncommon. These data provide insight into the flow behavior in marsh channels, the driving mechanisms of water exchange, and the potential for particle and solute exchange between tidal marshes and their adjacent estuaries. At both sites, tidal forcing is normally the dominant driving mechanism in water level and velocity signals with remote wind forcing having a limited contribution. As the tidal signal propagates from the Bowers site into the salt marsh, however, the progressive-type mixed wave is transformed into a standing wave with minor velocity distortions resulting from a reduction in the M2 tidal constituent as well as an amplification of the M4 overtide. The variability at both sites is typically well explained as a linear superposition of high-frequency tidal constituents and remotely forced wind-driven subtidal fluctuations. During storm events at intermediate to spring tides, however, both tidal and subtidal velocity characteristics in the channel are more nonlinear compared to both typical channel conditions and those at the Bowers site. During these events, in response to remote winds, tidal flow in the channel becomes progressive in form and flood dominant, while subtidal velocities are ebbward and nearly an order of magnitude stronger than typical conditions.