The Au Sable River runs through the northern edge of Big Creek Township, and the Mio Dam and its reservoir are located within the township.

As of the census[1] of 2000, there were 3,380 people, 1,422 households, and 968 families residing in the township.

There were 3,089 housing units at an average density of 21.8 per square mile (8.4/km2).

The racial makeup of the township was 97.49% White, 0.06% African American, 0.50% Native American, 0.12% Asian, 0.03% Pacific Islander, 0.15% from other races, and 1.66% from two or more races.

26.6% of all households were made up of individuals, and 13.2% had someone living alone who was 65 years of age or older.