**2.2 Saco Bay and Casco Bay**

Though situated next to each other, Saco Bay and Casco Bay differ significantly in terms of geography (**Figure 1**). Saco Bay is a 10-mile wide embayment containing the Saco Estuary, Goose Fare Brook tidal inlet, and Scarborough marshes that are fed by Nonesuch River. The mean tidal range of the bay is 2.7 m. During a storm study of Saco Bay, bottom current velocities measured at Higgins Beach and a mooring located just offshore of East Grand Beach reached a maximum of 1.09 m/s across six storm events monitored between January 23 and March 7, 2001 [13]. Many of these hydrodynamic features of Saco Bay have been partially explained by the sheltering of the bay from southerly waves by Biddeford Pool in the south and the presence of the Richmond Island headland in the north acting as a barrier to sediment transport [14]. Much of Saco Bay is very shallow and thus highly sensitive to rises in sea level, in contrast to the steeper shores of Casco Bay.

In this text, Casco Bay is split into northern and southern Casco Bay at the Chebeague Island. As is the case with Saco Bay, the M2 semidiurnal lunar tide is the primary tidal constituent for Casco Bay [14]. The primary freshwater input into the bay is considered as the combined discharge of the Presumpscot and Royal rivers, averaging roughly 40 m3 /s [15]. A salinity gradient is also present in the northern Casco Bay due to the input from the Kennebec [16], a river system comprised of the Kennebec and Androscoggin rivers that has been observed to discharge upward of 4000 m3 /s of freshwater during the spring.
