Topanga Creek drains Topanga Canyon and is the third largest watershed entering the Santa Monica Bay. The creek is one of the few remaining undammed waterways in the area, and is a spawning ground for steelhead trout. The area typically receives about of rain annually. Topanga Beach lies on the coast at the outlet of Topanga Creek. Topanga Canyon Boulevard, State Route 27, is the principal thoroughfare, connecting the Ventura Freeway (US 101) to the north with Pacific Coast Highway (SR 1) on the south. The southern portion of the boulevard largely follows Topanga Creek. North of the Old Topanga Canyon Road intersection, the boulevard traverses the Santa Monica Mountains.