Sowbridge Branch (Primehook Creek tributary)  Sowbridge Branch is a long 2nd order tributary to Primehook Creek in Sussex County, Delaware. According to the Geographic Names Information System, it has also been known historically as:   Sowbridge Branch rises on the Gravelly Branch divide about 0.5 miles southeast of Ellendale, Delaware. Sowbridge Branch then flows generally east to meet Primehook Creek at Waples Pond. Sowbridge Branch drains of area, receives about 45.4 in/year of precipitation, has a topographic wetness index of 649.54 and is about 19% forested.