The following orthophoto was created using Geographical Information Systems Software. Plum Island is the long, linear barrier beach island within the communities of Newburyport, Newbury, Rowley, and Ipswich. The Merrimack, Parker, and Ipswich rivers are the three major rivers that drain into the Great Marsh. The mouth of the Merrimack River is seen to the north of Plum Island, the Parker River is seen along the southern edge of the town of Newbury, and the Ipswich River is seen draining to the southern tip of Plum Island. Plum Island Sound is the waters contained behind Plum Island and form portions of the Plum Island River.