Critical erosion is here defined as any coastal erosion that threatens or damages man-made structures. Cliff erosion that does not threaten or damage man-made structures is not classified as critical, even though it might be severe. Most critical coastal erosion occurs in the northern part of San Mateo County where development is much denser than in the southern part (see critical erosion map).
For further information, contact Ken Lajoie http://walrus.wr.usgs.gov/elnino/SMCO-coast-erosion/criteros-lg.html,