The Isaac River is a river and anabranch in Central Queensland, Australia. The headwaters of the river rise south east of Glenden, Queensland and flow in a generally southern direction, crossing the Peak Downs Highway near Moranbah. It continues past Iffley and veers eastward at Leichhardt Downs forming a series of braided channels, and veers south east ag…The Isaac River is a river and anabranch in Central Queensland, Australia. The headwaters of the river rise south east of Glenden, Queensland and flow in a generally southern direction, crossing the Peak Downs Highway near Moranbah. It continues past Iffley and veers eastward at Leichhardt Downs forming a series of braided channels, and veers south east again and flows past the eastern edge of Junee State Forest and then discharges into the MacKenzie River of which it is a tributary.