158
R.H. Charlier and Chr. P. De Meyer
1.2
Causes of Beach Erosion
The term coastal erosion applies to the shoreline proper and to a strip of seafloor
immediately bordering on the coast. The most '~Asible" manifestation is coastline
recession, a phenomenon which is our primary concern here. Cliff erosion in
hard rocks is less obvious than for unconsolidated beaches. Coastal erosion - and
accretion - is subject to significant changes.
Natural causes of shore erosion include sea-level rise, variation in sediment
supply, storm waves, waves and surge overwash, deflation, longshore sediment
removal and transport, and sorting of beach sediment. Such erosion is
exacerbated by anthropic actions.
Other factors responsible for erosion are winds, tides, subaerial processes,
petrologic nature of the coast, climatic, chemical, mechanical conditions and
biological agents.
Anthropic causes of erosion include removal of subsurface resourses leading to
land subsidence, erection of structures interrupting transport of material, that
reduce sediment supply, by improving inlets, channels, dredging and implanting
"hard" coastal protection structures, concentrating wave energy on the beach,
increasing water level variations, modifying nature's coastal protection
arrangements and "mining" the beach for its materials or for minerals they
contain.
Classical examples of coastal erosion by landsliding are provided by the Vesuvius
slope and the Rissa event in Norway. Such coastal landslides can be due to man's
interference. Removal of gIoundwater and lateral support by wave erosion cause
repeated damage to beach line property in Seal Cove (California).
The coast of Bulgaria, north of Varna is another example of erosion by
landslides. Material that slides into the sea acts as temporary natural breakwaters.
Erosion is not due everywhere to a rise in sea-level. The phenomenon appears to
play a more important role, for instance, on the East and Gulf coasts of the
United States than on its West coast. Major causes of erosion are waves, storm
surges, nearshore currents, and tides. Spring tides bring about higher water
levels. Storm surges have a similar effect ; their impact on erosional conditions
are particularly, important on hurricane-prone coasts. Rip currents promote
erosion as well. The usual response of a beach is sand loss, migration off-shore
and berm-width decrease. Critical conditions for erosion involve wave steepness,
sediment fall velocity and beach-bed slope.
R.H. Charlier and Chr. P. De Meyer
1.2
Causes of Beach Erosion
The term coastal erosion applies to the shoreline proper and to a strip of seafloor
immediately bordering on the coast. The most '~Asible" manifestation is coastline
recession, a phenomenon which is our primary concern here. Cliff erosion in
hard rocks is less obvious than for unconsolidated beaches. Coastal erosion - and
accretion - is subject to significant changes.
Natural causes of shore erosion include sea-level rise, variation in sediment
supply, storm waves, waves and surge overwash, deflation, longshore sediment
removal and transport, and sorting of beach sediment. Such erosion is
exacerbated by anthropic actions.
Other factors responsible for erosion are winds, tides, subaerial processes,
petrologic nature of the coast, climatic, chemical, mechanical conditions and
biological agents.
Anthropic causes of erosion include removal of subsurface resourses leading to
land subsidence, erection of structures interrupting transport of material, that
reduce sediment supply, by improving inlets, channels, dredging and implanting
"hard" coastal protection structures, concentrating wave energy on the beach,
increasing water level variations, modifying nature's coastal protection
arrangements and "mining" the beach for its materials or for minerals they
contain.
Classical examples of coastal erosion by landsliding are provided by the Vesuvius
slope and the Rissa event in Norway. Such coastal landslides can be due to man's
interference. Removal of gIoundwater and lateral support by wave erosion cause
repeated damage to beach line property in Seal Cove (California).
The coast of Bulgaria, north of Varna is another example of erosion by
landslides. Material that slides into the sea acts as temporary natural breakwaters.
Erosion is not due everywhere to a rise in sea-level. The phenomenon appears to
play a more important role, for instance, on the East and Gulf coasts of the
United States than on its West coast. Major causes of erosion are waves, storm
surges, nearshore currents, and tides. Spring tides bring about higher water
levels. Storm surges have a similar effect ; their impact on erosional conditions
are particularly, important on hurricane-prone coasts. Rip currents promote
erosion as well. The usual response of a beach is sand loss, migration off-shore
and berm-width decrease. Critical conditions for erosion involve wave steepness,
sediment fall velocity and beach-bed slope.