Sometimes the trees of these communities are tall enough and dense enough to form a forest, and at other times the trees are more scattered. The extent of the vegetation away from the watercourse depends on the size and nature of the banks and the flood plains, the amount of water carried by the stream or present in the lake and very importantly on the depth and lateral extent of subterranean aquifers. Additionally, historical patterns of land use often determine the actual extent of the riparian corridor. Along small stream channels a riparian community may form a very narrow band, whereas along larger streams or in broad valleys with meandering stream courses, the riparian woodland or forest areas may be quite extensive. Today less than one percent of California is occupied by riparian communities, but in pre-colonial times these communities occupied considerably larger areas.
Riparian areas are dynamic and ever-changing environments.
Stream-channels may be swept clean of vegetation during floods as sediments are shifted from place to place. Fast-cutting water may cut into the banks of a stream, undercutting existing vegetation. Classification of California's riparian communities is difficult because of the diversity and complexity of the communities and the great alterations imposed by human activities. Each of these is variable. Riparian Plants Click on the name of a plant for a larger view.