Foster Brook is a 4.88 mi (7.85 km) long third-order tributary to Tunungwant Creek.

[2] Foster Brook rises about 1.5 miles (2.4 km) southeast of Gilmore and then flows northwest to meet Tunungwant Creek at Foster Brook, Pennsylvania.

Foster Brook drains 12.26 square miles (31.8 km2) of area, receives about 44.9 in/year (114 cm/year) of precipitation, and is about 87.64% forested.

[3]