198
R+H. Charlier and Chr. P. De Melter
A field of groins will maintain a stable beach, when filled to capacity with sand
but will not provide full protection against storm-driven waves. However, it
usually triggers downdrift erosion which can be somewhat mitigated by using
beach fill in the groin field. When placed too close together groins cause waves to
stir up material and current will carry material offshore.
Wave energy is absorbed by sand movement, seawards or landward, and rushing
up gradually sloping sand expanses.
Sand trapped by groins may be severely missed downdrift, and the latter areas
continued to be stripped of their sand. A wider beach is built just above the groin,
but no further.
To counteract longitudinal sand transport which resulted in silting of Lagos
harbor entry near Victoria Island (Nigeria), two groins were constructed between
1907 and 1916 (fig. 17). The actual consequence was sediment accumulation
west of Lighthouse Beach's groin but east of the harbor, near Victoria Beach's
groin erosion took a considerable toll with the shoreline retreating 1.25 km
(0.775 mi) J4. To redress the situation groins were lengthened and artificial
nourishment of I million tons of sand per year carried out. Yet, shoreline retreat
has continued, depending on the site, at a rate of 5 to 9 m (16 to 30 r) a year.
-'14) e e
OiRECTION OF
LONGSHORE 0RIFT
A
Fig. 14 : Beach stabilization
R+H. Charlier and Chr. P. De Melter
A field of groins will maintain a stable beach, when filled to capacity with sand
but will not provide full protection against storm-driven waves. However, it
usually triggers downdrift erosion which can be somewhat mitigated by using
beach fill in the groin field. When placed too close together groins cause waves to
stir up material and current will carry material offshore.
Wave energy is absorbed by sand movement, seawards or landward, and rushing
up gradually sloping sand expanses.
Sand trapped by groins may be severely missed downdrift, and the latter areas
continued to be stripped of their sand. A wider beach is built just above the groin,
but no further.
To counteract longitudinal sand transport which resulted in silting of Lagos
harbor entry near Victoria Island (Nigeria), two groins were constructed between
1907 and 1916 (fig. 17). The actual consequence was sediment accumulation
west of Lighthouse Beach's groin but east of the harbor, near Victoria Beach's
groin erosion took a considerable toll with the shoreline retreating 1.25 km
(0.775 mi) J4. To redress the situation groins were lengthened and artificial
nourishment of I million tons of sand per year carried out. Yet, shoreline retreat
has continued, depending on the site, at a rate of 5 to 9 m (16 to 30 r) a year.
-'14) e e
OiRECTION OF
LONGSHORE 0RIFT
A
Fig. 14 : Beach stabilization