Environmental Engineering Reference
In-Depth Information
nourishment strategies and optimise their performance (Hanson et al.
2002
;
Capobianco et al.
2002
). Nevertheless, the complexity of coastal and beach pro-
cesses requires that complete reliance on numerical modelling should be avoided
and predictions of beach renourishment performance should be firmly grounded
on relevant experience and expertise. The use of numerical modelling for all
aspects of beach renourishment has been questioned by several authors, including
Cooper and Pilkey (
2004
), who advocate the use of a conceptual approach as an
alternative to numerical modelling of such a complex system. The authors suggest
seven conceptual alternatives, including past engineering experience on the beach
in question or on neighbouring beaches, global experience on similar beaches, the
use of geo-indicators and field studies.
Numerical models were used in the design of a beach renourishment project
at Salina Bay, Malta (Sect.
4.4.3
, p. 82), where wave patterns and responses were
examined, and the results used to determine an optimum beach configuration for
long-term stability (Firman et al.
2011
).
At West Beidaihe Beach, south of Qinhuangdao in China, removal of a rock
jetty in 2002 for safety and aesthetic reasons resulted in the retreat of the coastline
and the reduction of a renourished beach (Kuang et al.
2011
). Kuang et al. (
2011
)
used numerical models to find that, without further renourishment, West Beidaihe
Beach would cease to provide a subaerial beach area suitable for recreation within
2-3 years. After numerical evaluation of various options it was decided that a
groyne at the eastern end of the beach played a key role in retaining the beach in
the long term. More sand was placed on the beach, and protected by a 250 m long
submerged breakwater.
At Anna Maria Key, Florida project design of the renourishment project com-
pleted in 1993 used modelling and successfully estimated a nine year renourish-
ment interval (Dean
2002
). At Colwyn Bay Beach, Wales numerical modelling
was used to assess alternative options for beach protection. The assessment was
divided in three phases: assessment of beach dynamics, definition of an optimum
recharged beach profile, and long-term modelling of alternative solutions (Oliveira
et al.
2011
). The large quantity of data provided by the assessment of the beach
dynamics was used as input and verification data for the numerical models, which
were then applied to test factors such as profile response to storms for different
berm widths and sediment sizes and to identify an optimum renourishment beach
profile.
Predictions of the direction and quantity of longshore drift formed part of the
design and environmental approval process for the 'sand engine' model (Sect.
4.3.2
, p. 62) (Stive et al.
2013
). Morphodynamic numerical modelling was used to
obtain projections of the temporal and spatial evolution of the large-scale renour-
ishment, 3, 5, 10, 15 and 20 years after renourishment.
Models have been used in the United States to estimate the impacts of dredge
site (borrow pits) on adjacent beaches (Benedet et al.
2013
), providing valuable
information about how different dredge pit designs interact with the adjacent
shore. With such information adjustments to the design of these features can be
made to minimise impacts on the adjacent coast.
