Ponding of local drainage by ice during the retreat phase of the Main Glaciation has left very few overflow channels incised into solid rock in the Lagan Valley area. One of the largest overflow valleys is the one followed by the Lagan Navigation Canal at Soldierstown near Moira. It drained Glacial Lough Lagan into Glacial Lough Neagh. The intake at Boyle's Bridge just east of Moira is at about 43m O.D. and the outfall at about 21m. The broad flat floor is now partially obscured by the disused Lagan Canal and by the Broad Water lake. The overflow may have been partially re-activated later by melt waters from the Antrim Coast re-advance.
