Riparian woodlands occur along canyon and valley bottoms with perennial or intermittent streams in nutrient rich soils, or within the drainage of steep slopes. Of all the plant communities in the Santa Monica Mountains, the riparian community contains the greatest species diversity. Also unlike other communities, riparian woodlands have multi-layered vegetation, with both an under and overstory. Dominant species may include arroyo willow (Salix lasiolepsis), California black walnut (Jugalns californica), sycamore (Platanus racemosa), Mexican elderberry (Sambucus mexicana), California bay laurel (Ubellularia californica), and mule fat (Baccharis salicifolia).
Four kinds of riparian communities are easily identifiable in the Santa Monica Mountains.
Big Sycamore Canyon in Point Mugu State Park, Malibu Creek, or Medea Creek in Cheeseboro Canyon contain good examples of riparian woodland.