Distant Ocean Connection

Green Hill Pond is the only salt pond that has a distant connection to the ocean through another pond. As shown in the aerial photo below, ocean tidal waters first go through the Charlestown Breachway, enter Ninigret Pond, and then pass under the narrow Creek Bridge before entering Green Hill Pond—a distance of about a half mile.

This distant ocean connection keeps the tidal range very moderate and time shifted. The tidal range in the ocean (order of 1 meter) is strongly damped going through the inlet (breachway) into Ninigret Pond (mean tidal range about 20 cm) and further damped going into Green Hill Pond (mean tidal range about 11 cm). * This distant ocean connection also causes a total phase shift of the high and low tides in Green Hill Pond of 4.5 hours later than the ocean.

*Source: Grilli et al, 2018, A Hydrodynamic Model Study to Assess the Impact of Dredging. Ocean Engineering, University of Rhode Island