Appears to be deer feeding damage to me, very common in winter. Cedars and arborvitae are deer favorites but they will eat just about anything when challenged for winter food sources. They can and do strip plants/trees/shrubs clean of leaves.
The hedge appears to be an arborvitae hedge and there was so much of it that they either didn't have to bend down to eat the bottom leaves or more likely the remaining bottom leaves were covered by snow when they were actively feeding.
Erecting barriers and erecting them properly is the most effective method of keeping deer out, barriers that they cannot reach over or jump over. Best material is black poly hard-to-see netting. Arborvitae can recover but very slowly over a period of years. Here are a couple of links to Extension resources about deer feeding damage and deer-resistant plants: