Impact of Historical Channel Deepening on Tidal Hydraulics in the Delaware Estuary

Anthropogenic modifications of estuarine morphology such as navigational channels have changed tidal dynamics in many estuaries. The implications of deepening may include shifts in tidal range, sediment transport, pollutant dispersal, and changes in flood risk, among others. Here, we use a numerical model to study how channel deepening has altered tidal elevation, currents, and energy fluxes in the Delaware, a convergent estuary on the east coast of the United States. Historical (1848) and modern (2014) depth soundings were digitized and gridded for a numerical model of the estuary. Numerical experiments indicate a doubling in tidal range, shifts in the arrival time of high water, and changes in elevation‐velocity phase. A historical increase in the upstream conveyance and transmission of energy is consistent with bigger amplitudes, swifter currents, and more progressive wave dynamics in the navigational channel. Changes in local topography were key in the modulation of tidal energy transmission upstream, especially in the tidal river. Plain Language Summary Channel deepening is a common engineering practice in many estuaries, rivers, and harbors worldwide. Although the benefits of shipping channels are evident in terms of commerce and recreation, the adjustment of water level and currents to a deeper channel involves hydrodynamic feedbacks that have been scarcely studied. The response of tides to channel deepening can also vary depending on basin geometry and coastline configuration, and it is necessary to study a wide range of estuarine systems to better understand the direct and indirect impacts induced by humans. We use a numerical model to study how a century of dredging impacted tidal flows and water level in the Delaware Estuary. We found that the reduction of friction associated with channel deepening doubled the tidal range in the upstream limit of the estuary. Key Points Channel deepening led to significant tidal amplification in the tidal Delaware River Local topography modulates tidal energy fluxes along theestuary