IV. Retreating Shorelines
Chapter I : Coastal Erosion
155
PREFACE
Coastal erosion, of beach and cliff alike, is not only the result of a complex
interaction of natural processes, it is furthered, markedly, by man's actions. The
so-called anthropic factor takes several aspects. It results from a general migration
towards coasts and ensuring demands for space and habitat. The explosion of
tourism and water-related recreation has increased the stress placed on the coastal
zone. A search for easily accessible materials, sand and gravel, has contributed to
exploitation of marine aggregates. Marine coastal mining has come of age.
Railroads and highways have been built close to shorelines. Dunes have been
bulldozed to accommodate developments. It has been reported that not a single
stretch of the Italian coastline has been left unmodified by man.
Railroad trestles across gullies and cations, or crossing channels, can be built to
span channels without altering much drainage patterns (example A.T. and S. RR
along the California coast). However, when highway construction requires
installation of culverts to control surface runoff, consequences are considerable as
erosion of gullies is intensified. In California new canyons were cut as a result.
Bluffs can be degraded by cuts made in rocks or drain pipes laid along former
drainage paths. Bluff-top grading for construction, removal of protective
vegetation and case-hardening surface materials affect erosion progress.
Beach mining for sand or gravel or cobbles results evidently in the removal of a
volume of material but, additionally, and as a consequence sand mining
contributes to beach erosion. This involves off-shore as well as onshore sand
removal and has been illustrated by a long list of cases ranging from Lebanon and
Israel to Morocco and the United States. On the Oregon Coast (Siletz Spit) 72,000
m 3 (2.543 million cu.ft) of sand were removed from Schoolhouse Creek beach :
reduction of sand volume reduces its buffer effectiveness for the land. Prior to the
mining operations the beach was stable. The mining permit has not been renewed
since 1972. The demand for construction and road paving material has
encouraged off-shore dredging. Beach exploitation is common. The
environmental consequences have been recently reviewed by Charlier (1990).
However, destruction of coral reefs to supply omamental material is equally
damaging, both ecologically and dynamically, as it enhances beach erosion by
removing "natural breakwaters".
The chapters that follow stress the natural factors of coastal erosion, an inexorable
phenomenon, and leave aside man's impact, except where directly pertinent. It
will consider causes and processes of erosion, beach response and approaches to
alleviate the problem.
Chapter I : Coastal Erosion
155
PREFACE
Coastal erosion, of beach and cliff alike, is not only the result of a complex
interaction of natural processes, it is furthered, markedly, by man's actions. The
so-called anthropic factor takes several aspects. It results from a general migration
towards coasts and ensuring demands for space and habitat. The explosion of
tourism and water-related recreation has increased the stress placed on the coastal
zone. A search for easily accessible materials, sand and gravel, has contributed to
exploitation of marine aggregates. Marine coastal mining has come of age.
Railroads and highways have been built close to shorelines. Dunes have been
bulldozed to accommodate developments. It has been reported that not a single
stretch of the Italian coastline has been left unmodified by man.
Railroad trestles across gullies and cations, or crossing channels, can be built to
span channels without altering much drainage patterns (example A.T. and S. RR
along the California coast). However, when highway construction requires
installation of culverts to control surface runoff, consequences are considerable as
erosion of gullies is intensified. In California new canyons were cut as a result.
Bluffs can be degraded by cuts made in rocks or drain pipes laid along former
drainage paths. Bluff-top grading for construction, removal of protective
vegetation and case-hardening surface materials affect erosion progress.
Beach mining for sand or gravel or cobbles results evidently in the removal of a
volume of material but, additionally, and as a consequence sand mining
contributes to beach erosion. This involves off-shore as well as onshore sand
removal and has been illustrated by a long list of cases ranging from Lebanon and
Israel to Morocco and the United States. On the Oregon Coast (Siletz Spit) 72,000
m 3 (2.543 million cu.ft) of sand were removed from Schoolhouse Creek beach :
reduction of sand volume reduces its buffer effectiveness for the land. Prior to the
mining operations the beach was stable. The mining permit has not been renewed
since 1972. The demand for construction and road paving material has
encouraged off-shore dredging. Beach exploitation is common. The
environmental consequences have been recently reviewed by Charlier (1990).
However, destruction of coral reefs to supply omamental material is equally
damaging, both ecologically and dynamically, as it enhances beach erosion by
removing "natural breakwaters".
The chapters that follow stress the natural factors of coastal erosion, an inexorable
phenomenon, and leave aside man's impact, except where directly pertinent. It
will consider causes and processes of erosion, beach response and approaches to
alleviate the problem.