 According to the United States Census Bureau, the village has a total area of , of which is land and (0.69%) is water.South Branch Township occupies the southeast corner of Crawford County and is bordered by Oscoda County to the east and Roscommon County to the south.The township takes its name from the South Branch of the Au Sable River, which flows nearly the length of the township, from the southwestern corner north and east to its mouth at the Au Sable River in the northern part of the township.