A rise in volume of more than 16 times the flow a week apart is testament to how quickly the face of the river can change.
(A rise in volume of more than 16 times the flow; is; testament to how quickly the face of the river can change) (the face of the river; can change; )
A rise in volume of more than 16 times the flow the face of the river
is can change
testament to how quickly the face of the river can change