The Tred Avon River encompasses all the waters of the Tred Avon River and its tributaries northeasterly of a line beginning at a point, at or near Lat. 38° 40.250' N., Long. 76° 11.867' W., then running 73° (True) to a point, at or near Lat. 38° 40.550' N., Long. 76° 10.617' W.