sentences:  From there the River Twyver formed a moat as the earthwork followed it north-west to Alvin Gate then on to the river's junction with the Old Severn.This easternmost channel of the River Severn had dried up by the 19th century, but at the time of the civil war it was still a navigable river.The earthwork then followed the Old Severn south-west to a point a short distance north of Westgate Street, from where it was extended the other side of the Old Severn to the River Severn just above the west gate.