What is the fine-grained topic of the following text: This area of ​​Sonoma County, Northbound San Francisco, is a rugged coastal area characterized by Grassy viewshed, bounded at its upper edge by residues from forestry, descending, gentle topography seaward, the constant surge of small cliffs edge and strong wind incidence. Only return the topic.
Geographical Features of Sonoma County, Northbound San Francisco