USGS

1982-83 El Niño Coastal Erosion: San Mateo County, California

Kenneth R. Lajoie and Scott A. Mathieson

Navigation table:

INTRODUCTORY TEXT

SAN MATEO CTY. COASTAL STABILITY MAP

SAN MATEO CTY. CRITICAL COASTAL EROSION MAP

COASTAL EROSION MAPS

COASTAL GEOLOGY MAPS


COASTAL STABILITY MAP: Explanation below

Coastal Stability Map

Segments of the San Mateo County coast are classified as stable and unstable based on the inherent resistance of the exposed rocks to wave erosion and slope failure. The stable coastal segments in the northern part of the county are backed by resistant granitic rocks, which form high bluffs (maps 5 and 6) to low cliffs (map 7). The stable coastal segments in the southern part of the county (see coastal erosion and geology maps 20 to 24) are backed by resistent sedimentary rocks that form low cliffs. Coastal segments of intermediate stability are backed by moderately resistent sedimentary rocks that form high bluffs (maps 4 and 16) and low-to-high cliffs (maps 7 to 9, 12 to 18, 25, and 26).

Unstable coastal segments are backed by weakly indurated or highly fractured sedimentary rocks that form high bluffs (maps 1 to 2, and 8), weakly indurated terrace deposits that form low cliffs (maps 3, 4, 6, 7, 9 to 12, and 23 to 25), and loose beach and dune sand that forms spits and low cliffs (maps 4, 9, 10, 19, and 23 to 25). Along much of the San Mateo County coast, fragile terrace and loose dune deposits overlie resistent to moderately resistent bedrock. In those areas the base of the cliff is stable and the upper part is unstable. If the cliff is sufficiently high that wave surge does not erode the terrace deposits exposed in the upper part of the cliff face, that coastal segment is classified as stable (maps 7, and 18 to 23).

To see the detailed maps that are discussed in the paragraphs above, continue on to the "Coastal Erosion Maps" Index or "Coastal Geology Maps" Index.

For further information, contact Ken Lajoie


USGS El Niño Home Page

http://walrus.wr.usgs.gov/elnino/SMCO-coast-erosion/coaststabl-lg.html,
6-May-1998,
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