Landslides - look for circular or oval areas of erosion on steep slopes
indicating the scar caused
by a landslide. Commonly, as in the example at left, a depositional area
occurs seaward, or downslope, of the erosional area where the failed material
came to rest.
(Landslides North of San Francisco, Location 1)
Rhythmic Patterns - Look for repeated patterns of erosional areas
adjacent (in a longshore
direction) to accretional areas. These are likely due to the presence of
giant cusps in one of the surveys and either a) giant cusps in the other survey
were not present or b) were shifted alongshore. During storms, wave runup
in low embayments between adjacent cusps may attack dunes, causing net
erosion, whereas landward of prominent cusps the dunes may be protected by
the wide beach.
(Umpqua River, Location 2)
Dune & Cliff Erosion - During severe storms, when runup can reach
the base of cliffs and dunes, the wave impact leads to net erosion of the
dune or cliff face which can be best observed in cross-shore profiles.
In this example, the dune retreated landward 15 m during the El Niño
(Monterey Bay, Location 3)
Longshore Sediment Transport - look for a pattern where an erosional
area is adjacent (in a longshore direction) to an accretional area,
suggesting transport direction. In the example, transport is suggested
from north to south with deposition occurring near the mouth of an inlet.
These patterns are also pervasive at manmade structures designed for
navigation and property protection, but also occur adjacent to natural
irregularities in the coast, such as headlands.
(Point Reyes, Location 1)|
Overwash - look for a pattern where a depositional area occurs
of an erosional area, suggesting overtopping of the beach by wave runup.
This results in erosion of the beach and net sediment transport (and
deposition) landward. In this example, a low-lying spit was overwashed.
This process occurs more extensively on the low-lying barrier islands of
the East and Gulf of Mexico coasts, but there are many examples of overwash
on the West coast during the 1997-98 El Niño winter as well.
(Monterey Bay, Location 1)
River Breakthrough - look for a new channel eroded across the beach.
(Monterey Bay, Location 2)