Riparian woodland is found along watercourses. Cal Poly Pomona has no watercourses with year-round aboveground flow, but below-ground water supports areas of riparian woodland in the mouth of Box Canyon above Building 1 (where there are permanent springs), the mouth of the canyon system above J Lot, and the drainage below the reclaimed water reservoir above M Lot.
The commonest species in the riparian woodland are aliso (Plantanus racemosa) and arroyo willow (Salix lasiolepis). The western black willow (Salix gooddingii) occurs on campus, but not in the riparian areas. Two introduced plants, California fan palm (Washingtonia filifera) and peppertree (Schinus molle) are frequent. Species that occur in nearby riparian areas, but which are not present on campus, include Frémont cottonwood (Populus fremontii), red willow (Salix laevigata), and yellow willow (Salix lucida).
The spring-fed woodland in Box Canyon could support a greater diversity of riparian species, but parts of it are heavily planted with ornamental trees, and the flow from the springs is diverted into an undeground drainage channel.