IV. Retreating Shorelines
277
Patented in the U.S. under the trade-name "Stabeach" the system involves buried
components : a porous filter drain pipe (inserted in the beachface), a return pipe
to the sump, the sump-, and a discharge pipe from sump to a water disposal area ;
the sump pump itself is submerged. The principle is simple and has been
enunciated from 1948 0d.S. Grant, 1948, Influences of the water table on beach
aggradation and degradation : J. Mar. Res. 7, 655-660) through 1989 0 a. Bruun,
1989, the coastal drain, what it can do and not do : J. Coast. Res. 5, 1, 123) :
when the water table under a beach is lower than ocean level, the water '1"lows"
(drains) into the beaclfface depositing sand in the process consolidating it. By
draining then the beach, the table is kept l~low sea level, at low water the
seaward flow abandons material and the wave backswash does not take sand from
the beach. Furthermore, the water flow into the beach sand condenses it, thereby
giving it more erosion resistance.
Monitoring the effects of dewatering in Denrnark and Florida has shown that
treated areas fare much better than adjoing ones and that no downdrift erosion
was provoked.
Drainage has also been used for friable cliff stabilization (clay, chalk, sandstone).
Though unrelated to dewatering, the 'Plates system" alternative can be
mentioned at this time. This approach has been tested in Barcelona (Spain) about
1993. Little has been heard about the system since then. By attaching at depths of
a few fathoms horizontal plates to poles driven into the sea bed, it is expected to
reduce wave energy. The large water mass kept in oscillation produces a kinetic
energy which creates another wave movement in a phase opposite to that of the
incoming waves. The two movements are to cancel one another.
3.5
Feeder Berms
Sand reserves will help natural processes and they have been established on- and
off-shore. Berm-feeding consists in establishing such a reserve on the beach-berm
so that a supply of material is available for said processes.
Feeder berms consist in the placement of appropriate sediments on the submerged
part of the beach slope at waterdepths (below L.W.) ranging from - 1 m to - 8 m
(- 3,28 to 26 fl). Feeder berms are a cheap method of placing material close to the
beach. Onshore wave action/transport is expected to move the material to the
beach according to the equilibrium profile.
277
Patented in the U.S. under the trade-name "Stabeach" the system involves buried
components : a porous filter drain pipe (inserted in the beachface), a return pipe
to the sump, the sump-, and a discharge pipe from sump to a water disposal area ;
the sump pump itself is submerged. The principle is simple and has been
enunciated from 1948 0d.S. Grant, 1948, Influences of the water table on beach
aggradation and degradation : J. Mar. Res. 7, 655-660) through 1989 0 a. Bruun,
1989, the coastal drain, what it can do and not do : J. Coast. Res. 5, 1, 123) :
when the water table under a beach is lower than ocean level, the water '1"lows"
(drains) into the beaclfface depositing sand in the process consolidating it. By
draining then the beach, the table is kept l~low sea level, at low water the
seaward flow abandons material and the wave backswash does not take sand from
the beach. Furthermore, the water flow into the beach sand condenses it, thereby
giving it more erosion resistance.
Monitoring the effects of dewatering in Denrnark and Florida has shown that
treated areas fare much better than adjoing ones and that no downdrift erosion
was provoked.
Drainage has also been used for friable cliff stabilization (clay, chalk, sandstone).
Though unrelated to dewatering, the 'Plates system" alternative can be
mentioned at this time. This approach has been tested in Barcelona (Spain) about
1993. Little has been heard about the system since then. By attaching at depths of
a few fathoms horizontal plates to poles driven into the sea bed, it is expected to
reduce wave energy. The large water mass kept in oscillation produces a kinetic
energy which creates another wave movement in a phase opposite to that of the
incoming waves. The two movements are to cancel one another.
3.5
Feeder Berms
Sand reserves will help natural processes and they have been established on- and
off-shore. Berm-feeding consists in establishing such a reserve on the beach-berm
so that a supply of material is available for said processes.
Feeder berms consist in the placement of appropriate sediments on the submerged
part of the beach slope at waterdepths (below L.W.) ranging from - 1 m to - 8 m
(- 3,28 to 26 fl). Feeder berms are a cheap method of placing material close to the
beach. Onshore wave action/transport is expected to move the material to the
beach according to the equilibrium profile.