The Santa Barbara Channel region offers a rich diversity of watersheds for experimental and observational study that typify the types of watersheds found in most Mediterranean climates. About 40 catchments, ranging in size from small drainages (< 10 km2) flowing directly into the ocean to the Santa Clara River drainage basin which encompasses ~4000 km2, drain into the Santa Barbara Channel.
The watersheds feeding into the Santa Barbara Channel are complex with a mix of land uses and nutrient and sediment sources to streams. Steep mountain slopes composed of easily eroded material and strongly seasonal rainfall create the conditions for substantial erosion and sediment inputs to streams and the coastal ocean. The intermittent occurrence of fire in the catchments further enhances temporal variation in the export of sediments and nutrients. Modifications of the frequency or intensity of droughts due to climate change or ENSO events are strongly expressed in the Mediterranean climate of the region.
The catchments of the Santa Barbara region also vary widely in the extent and intensity of agricultural and urban development, which differentially contribute nutrients and pollutants to runoff. The degree of agricultural and urban development generally varies with elevation in most of the watersheds, with most intense development in the coastal plains and foothills (see map at left). Most drainages start in the mountains, which are generally covered in chaparral and coastal sage scrub that burn episodically. The foothills are a mix of grazed grassland/oak woodland, agricultural land, and suburban development. Lower yet, the coastal plain includes foothill land uses, but also urbanized areas. Finally, there are the coastal marshes, sloughs, or lagoons at sea level.