River Mole rises in Baldhorns Copse to the south of the village of Rusper in West Sussex. The river flows initially southwards for to a small lake at Baldhorns Park, before running eastwards through a largely rural area towards Crawley. The first tributaries to join the young river drain the northernmost part of St Leonard's Forest, between Horsham and Crawley, although much of the forest is in the catchment area of the River Arun. The Mole skirts the northern suburbs of Crawley where it is joined by its first major tributary, Ifield Brook, which drains Ifield Mill Pond.