Environmental Engineering Reference
In-Depth Information
Hartog et al. (
2008
) used numerical modelling, consisting of analyses of waves,
hydrodynamics, and a morphology to identify the processes that influenced the
performance of renourishment at Delray Beach, Florida. The analyses included an
assessment of the impacts of borrow pit location and size on the renourishment,
changes alongshore, and erosion due to the change in coastline orientation caused
by deposition of the renourishment.
In addition to numerical modeling and laboratory-based assessment, field
experiments have been used to help design and assess performance of beach ren-
ourishments. One such field assessment, sediment tracing, is a useful method for
quantifying the magnitude and direction of littoral sediment flux. Provided the
tracer material faithfully represents the native sediment characteristics (e.g. in par-
ticle size and fall velocity), tracer can indicate littoral transport through monitor-
ing over time and space (McComb and Black
2004
). As well as use in determining
the fate of dredge material (Marsh et al.
1997
) and sediment transport associated
with by-pass systems (Sherman et al.
1990
, Uda et al.
1991
), sediment tracing has
been used in the design of a beach renourishment project by developing a better
understanding of the sediment transport processes (Fig.
4.32
). Sediment tracing
can also be used to evaluate the performance, with tracing material incorporated
into the beach renourishment sediment.
At the Great Egg Harbour inlet in New Jersey on the east coast of the United States,
sediment tracer studies were conducted to understand the fate of beach renourishment
sediment. Tracer material was placed at the low water line on the beach and then the
movement of the tracer monitored over a 30-day period through the collection and
analysis of sediment cores up and down the beach, as well as on the inlet ebb shoal.
Fig. 4.32 a
Indicator sediment (tracer) being released at the start of a study in 2014.
b
Example
of a recovered core including tracer material. © Royal HaskoningDHV/Jon Marsh of ETS
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