Solana Beach Coastal Preservation Association
August 20, 1998
Project No. 1831
Although groundwater seepage may locally exist throughout the study area, groundwater
seepage exiting the bluff face was only noted at the back of the sea cave below 205 Pacific
Avenue and in the vicinity of Fletcher Cove at the contact between the upper terrace
deposits and the underlying Pleistocene-age canyon infill.
In its broadest sense, geomorphology deals with land forms and their evolution over time.
Lithology, or the description of the physical character of rocks, can also be used to
estimate the relative erosion resistance of the intact, non-fractured rock. Geologic
structure, which includes structural discontinuities such as jointing and faults, can be used
to estimate variations in erosion resistance within a particular lithologic unit. Coastal
processes include waves impacting upon coastal bluffs. This is the basic source of erosive
energy, which is modified by the nearshore and offshore bathymetry, and by sea level
elevation relative to the nearshore bathymetry. More recently, natural coastal geomorphic
processes have been influenced by anthropic activities.
The methodologies most useful to assess relative rates of coastal erosion are divided into
five general separate categories:
Impact of long-term sea level change; and
Empirical and analytical techniques.
Coastal geologists and geomorphologists traditionally employ the first three techniques,
often relying on interpretation of maps and aerial photographs. However, such historical
data usually cover a short time span and may be limited to small-scale maps and
photographs such that significant errors may occur in estimating the amount and rate of
shoreline change. If the available maps and photographs cover only a quiescent climatic
period, underestimates are likely. The details of each methodology are discussed in the