BEACH NOURISHMENT PROJECTS IN CARBONATE MATERIAL BEACH

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					                                                                    Submitted February, 2006




                           BEACH NOURISHMENT PROJECTS
                           IN CARBONATE MATERIAL BEACH
                    Ryuichiro Nishi 1, Robert G. Dean2 and Mario P. de Leon 1
             1
               Department of Ocean Civil Engineering, Kagoshima University, Japan
            2
              Department of Civil and Coastal Engineering, University of Florida, USA


Abstract

     Hard engineering approaches such as seawalls, groins, detached and submerged breakwaters to stabilize or
restore beaches are used to counteract beach erosion. However, none of these shore protection structures adds
more sand to the beach system to compensate for natural and artificial erosion. Thus, beach nourishment, also
called “artificial nourishment”, “replenishment”, “beach fill”, and “restoration” involves the addition of sand in
designed contours to extend a beach. In the United States, Europe and Australia, beach nourishment has grown
in acceptance as major shore protection and beach restoration measure for more than fifty years. In Japan,
“hard” structures are also commonly used but after a new coastal law was approved in April 2000, beach
nourishment as a legal shore protection work was accepted. However, at present, beach nourishment is not yet
widely used as shore protection method in Japan.
     Specifically, this paper deals with beach nourishment projects in carbonate material (coral reef) beach in
Okinawa, Japan and in Florida, USA. Data on beach fill length, volume, nourishment volume density,
frequency of beach fill, borrow source and cost of beach fill material from different beach nourishment projects
were reviewed, assessed, analyzed and consolidated.Range of values and mean values of nourishment project
parameters were calculated and then were used as basis for the comparative analysis of beach nourishment in
normal sandy and coral sandy beaches. The consolidated results will serve as database for implementing future
restoration projects in coral sandy beaches in tropical and subtropical countries like the Philippines.

Keywords:    Beach nourishment, carbonate material (coral reef) beach, beach erosion, shore protection

Introduction
   Beach nourishment involves the placement of
sediment on a typically eroding beach to advance the
shoreline seaward for the promotion of storm protection,
recreation, and natural habitat. Its design process
determines the quantity, configuration, source and
distribution of the sediment to be placed along a
specific section of the coast. Nourishment projects are
designed as a series of sequential fill placements over
time to account for the long-term erosion process. For
design purposes, the fill placed on a beach comprises of
two components:
   1. The design cross-section which achieves the
        project purpose (storm protection and
        recreational area)
   2. Advanced-fill amount which erodes between
       nourishment events.                                    Figure 1.   Typical beach nourishment in
                                                                          Okinawa, Japan

    It is a standard practice to provide sufficient sand to nourish the entire profile, from the dune to the depth of
significant sand movement, DC. Therefore, the total volume, VT, somehow independent of profile shape since the
shape of the renourished profile will be parallel and similar to the existing natural profile, can be estimated by
                                        VT = ( DB + Dc ) LW                                                        (1)
where DB is the elevation of the berm, L is the length of the nourishment project, and W is the desired amount of
beach widening.
      The geomorphologic characteristic of the beach area significantly affects the amount of nourished sand.
For coral sandy beach, the amount of nourished sand is lesser compared to normal sandy beach. Thus, the
presence of hard coral cover compensates the volume of nourished sand requirement. The quantity and the
distribution of advanced fill can be determined by analyzing the historical erosion and shoreline changes of a
beach and estimating how the project fill will affect coastal processes. The procedures used include the
historical shoreline change method (USACE, 1991b) or analytical (Campbell et al., 1990) or numerical methods
(Hanson and Kraus, 1989). For normal sandy beach, the sediment transport (both for erosion and accretion) is
greater compared to coral sandy beach as a result of current and waves impact with beach sand. Source of
nourished sand may be located offshore or at an onshore area called “borrow area” or “borrow pit” at a relatively
short distance seaward or tens of kilometers from the beach to be nourished. Typical plan areas of the borrow
pit are on the order of 1 km2 to 10 km2 and typical excavated depths on the order of 2m to 10 m. Grain size
distribution of the borrow material affects how a beach erodes and how the nourished beach responds to storms.
Thus, the borrow sand is judged to be compatible if the nourishment grain size distribution is similar to that of the
native sand. Various methods of quantifying compatibility include mean and median diameters, sorting and
equilibrium beach profiles. Approaches which are commonly used for the placement of nourished sand on the
beach include: (1) placing all of the sand as a dune behind the active beach, (2) using the nourished sand to
build a wider and higher berm above the mean water level, (3) distributing the added sand over the entire beach
profile, and (4) placing the sand offshore to form an artificial bar.
      For the past 44 years, the United States has spent about $ 15 million per year to help protect the nation’s
beaches while a number of countries, notably Spain, Germany, Japan and the Netherlands, spend proportionally
from twice the dollars in the Netherlands to 100 times in Japan (Houston, 1995). Design of beach nourishment
projects in the United States has evolved as knowledge of physical beach processes has increased with the
inclusion of design volume, design of advanced fill and analysis of sand compatibility as areas for improvement.
Verhagen (1990) described the beach nourishment design method employed in the Netherlands with substantial
reliance on historical data and design assumptions. Dette et al (1994) described the method employed in
Germany to represent the volumetric losses over time from a beach nourishment project using the assumption that
the volume decays exponentially with time.
      Nishi et al (2004) reviewed the status of beach nourishment projects in Japan and Florida and concluded that
average beach nourishment project in Japan is nearly on the order of 1/19 of average beach nourishment in
Florida in terms of volume. In addition, average length of beach nourishment projects in Japan is nearly 1/17 of
an average length of beach nourishment projects in Florida. On the borrow area (source of sediment), only
10 % of beach nourishment projects use the sediment in the same regional sediment transport system. Because
of this, it is encouraged that Japanese researchers need to conduct more studies on borrow site.
      Hamm et al`s (1998) comparative results in beach fill study in five European countries indicated the big
differences in nourishment fill rates and volumes. Spain and the Netherlands are by far the biggest nourishing
countries in Europe each at 110 x 106 m3in volume. Annual fill rates for selected countries are the following;
France, 0.7 x 106 m3, Italy, 1x 106 m3, Germany, 3 x 106 m3, Netherlands, 6 x 106 m3, Spain, 10 x 106 m3,
Denmark 3 x 106 m3, Great Britain, 4 x 106 m3, Japan, 0.5 x 106 m3, South Africa, 0.5 x 106 m3, Australia, 1 x 106
m3, and USA, 30 x 106 m3.
      Bird (1990) conducted a review of beach nourishment projects in Australia from 1975-1987. Results
showed that the average cost of beach nourishment per km is $A 232,902 (¥19,316,855 and $179,960) based
from a total of eighteen beach nourishment areas with a total beach length of 19.3 km amounting to a total cost of
$A 4,495,000 (¥372,814,588 and $3,473,221). Consolidated data of beach nourishment projects from 1984 to
2000 in Australia indicated a total volume of beach fill equal to 372,000 m3.
      According to Massel et al (2000), the increased economic pressure for development, increased impact from
land-based and marine industries, and increase access to coral reef areas have all lead to the demands to provide a
sound engineering and environmental basis for infrastructure developments in coral reef areas. Such can only
be achieved through comprehensive understanding of the physical processes which shape the reef environment
and control its ecology. Thus, beach nourishment is a viable engineering alternative for shore protection and is a
principal technique for beach restoration.
     In the Philippines, beach nourishment has been considered specifically for the development of beaches for
recreation purposes. Of the 7,107 islands surrounded by bodies of water, major tourism developments are
continuously expanding in coral beaches of Mactan, Cebu, Bohol, Palawan, Boracay and many other islands
where location of hotels and resorts are well set back from the shoreline. The absence of any hard structures in
the coastal zone permeates white sand beaches to extend further. In the efforts to achieve wider and longer
white sand beach front in the potential area for resorts and hotels, beach developers usually manage to import
white sand as nourished fill from neighboring islands within the region.

Materials and Methods
     Beach nourishment project data in coral reef areas from Okinawa, Japan and Florida, USA were obtained
from Department of Civil Engineering, Okinawa Prefectural Government and through literature review. The
data included; (1) length of nourishment project, (2) volume, (3) nourishment volume density, (4) borrow source,
and (5) project cost of beach fill material. Range of values and mean values of the nourishment project
parameters were calculated and used as basis for the comparative analysis to provide estimates and basis for
future implementation of nourishment projects.

Data/Results and Discussion
     Twenty-four (24) beach nourishment projects in carbonate beach for the periods from 1990 – 2010 are
recorded in Okinawa, Japan where six million tourists annually visit and 60 % of them enjoy marine leisure on
a white beach. Figure 1 shows typical beach nourishment in Okinawa, Japan. The same with Florida, white
sandy beach is a valuable resource to attract more tourists. As of 2003, twenty (20) projects were already
completed, two (2) are still partially completed, and two (2) have not been started yet. Data on beach fill length,
volume, cost of beach fill material, frequency of beach fill and borrow source are presented in the following
figures.
                                                 Length of beach fill (m)    Mean length (m)                                                    Volume of beach fill (m3)   Mean volume (m3)

                               1,200m                                                                                           250,000m3


                               1,000m                                                                                           200,000m3
                                                                                                    Volume of beach fill (m3)
    Length of beach fill (m)




                                800m
                                                                                                                                150,000m3

                                600m
                                                                                                                                100,000m3
                                400m

                                                                                                                                 50,000m3
                                200m


                                 00m                                                                                                00m3
                                                                                                                                            0     5       10       15        20      25        30
                                        0        5          10        15         20       25   30
                                                                                                                                                  Beach project areas in Okinawa, Japan
                                                     Beach project areas in Okinawa, Japan

                                            Figure 2. Length of beach fill project                                                      Figure 3. Volume of beach fill

      Figure 2 represents the various nourishment lengths of beach fill projects. The length of beach nourishment
is the most important parameter for longevity of the project in general. Beach fill length ranges from 150 m to
1,000 m with a mean of 441 m. In contrast, the average length of artificial beaches in Japan was on the order of
600 m in 1990.
      Figure 3 indicates the range of volume of beach fill. Beach fill volume ranges from 3,930 m3 to 193,350
  3
m having a mean of 41,581 m3. Nourishment volume density refers to the nourishment volume per unit length
of the beach and is a significant parameter to the actual and/or perceived performance of the project. For coral
sandy beaches, typical volume density ranges from 80 to 100 m3/m. In the case of beach nourishment projects
in Okinawa, the volume density ranges from 20 to 322 m3/m with a mean volume density of 94 m3/m which is
about 38% of the recommended volume density for normal sandy beach in the United States. Volume of beach
fill is a function of berm(DB)and critical water (DC) depths. Thus, the critical water depth in normal sandy
beach is larger compared to carbonate beach due to the presence of coral cover which compensates for the
volume of nourished sand required (Figures 4 and 5). In general, critical water depth in Japan ranges from 6 to
12 m.


                                                                                                                             DB



                 DB

                                 fill                                                                                                        fill
                 DCO
                                                                                                                       DC


                                        where DB   = berm depth                                                                                       where DB = berm depth
                 Coral cover                  DCO = critical water                                                                                          DC = critical water
                                                    depth over a                                                                                                depth
                                                    coral reef


                                                   Thus, DC >> DCO

Figure 4.   Typical cross-sectional view of beach                                                                 Figure 5. Typical cross-sectional view of beach
             nourishment in carbonate beach                                                                                  nourishment in normal sandy beach



                                                                                        Cost of beach fill material per unit volume (JPY/m3)                Mean cost (JPY/m3)

     Figure 6 represents the cost of beach                                                               6,000円
                                                           Cost of beach fill material per unit volume




fill material per unit volume. The actual
cost incurred in the projects ranges from 0 to                                                           5,000円
5,150 JPY/m3 (0 to 44 USD/m3 or 0 to 2,266
PHP/m3). Dredged material from other                                                                     4,000円
coastal projects is an economical factor in
                                                                           (JPY/m3)




nourishment projects. Thus, information                                                                  3,000円
such as port dredging should be properly
circulated      among       multi-government                                                             2,000円
agencies. In general, estimated average
cost is 2,564 JPY/m3 (22 USD/m3 or 1,128                                                                 1,000円
PHP/m3).
                                                                                                           00円
                                                                                                                  0         5         10         15         20        25          30
                                                                                                                                Beach project areas in Okinawa, Japan


                                                                                                                      Figure 6. Cost of beach fill material

      Figure 7 indicates the frequency of beach fill with reference to the volume of nourished sand per year. The
annual average volume of beach fill is 18,000 m3. Of the twenty-four projects, 16 (67%) had beach nourishment
less than 18,000 m3/yr while 8 (33%) had beach fill greater than the annual mean.
      Figure 8 contains information of two borrow sources from which the twenty-four (24) beach projects got the
nourished sand. Twenty-three (95.8%) beach fill projects obtained the borrow sand from the same borrow
source area and only one (4.2%) project got a different borrow source, from a dredged area adjacent to the coast
of which dredged material was donated to the project legally.
                                                   Volume of beach fill per year (m3/yr)                                            Number of beach fill projects using the same borrow source
                           7
                                                                                                                                             25




                                                                                                                   projects using the same
 Frequency of beach fill




                           6




                                                                                                                     Number of beach fill
                                                                                                                                             20




                                                                                                                        borrow source
                           5
                           4                                                                                                                 15
                           3                                                                                                                 10
                           2
                                                                                                                                              5
                           1
                           0                                                                                                                  0
                               0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56                                     Chibishi               By other project
                                                                                3
                                            Volume of beach fill per year (m /yr) x 1000 m
                                                                                                3                                                               Borrow source

                 Figure 7. Frequency of annual beach fill volume                                                                      Figure 8. Source of borrow material

Conclusion
      The continuous implementation of beach nourishment in the US, European countries, Australia, Japan is a
significant index and a concrete evaluation that beach nourishment is a viable engineering alternative for shore
protection and is therefore a principal technique for beach erosion. Thus, beach nourishment is still a favorable
shore protection method in developed countries. However, beach fill can also be the best solution in carbonate
beaches in tropical and subtropical countries for tourism and economic purposes.
Following are the conclusions generated from the review, assessment, analysis and compilation of nourishment
projects in carbonate beaches in Okinawa, Japan, to wit;
   1. Nourishment length, width, berm and critical water depths are functions of volume of beach fill. In the
      carbonate beaches considered, mean length is 441 m in contrast to 600 m in artificial beaches in 1990 while
      volume is on the order of 41,581 m3 which is 7% lower compared to 44,800 m3 in normal sandy beaches in
      Japan.
   2. Volume density of beach fill is 94 m3/m which is within the range for typical coral sandy beach from 80 to
      100 m3/m and is about 38% of the recommended density in normal sandy beaches in the United States.
   3. Cost of beach fill material is dependent upon the borrow source. Dredged material from ports and harbors
      dredging works is an economical means for beach fill provided that compatibility of grain size is satisfied.
      Moreover, geomorphologic characteristic of sandy beaches is a significant factor in the overall cost of beach
fill both in the nourishment and re-nourishment stages. Therefore, project scale and cost of beach nourishment are
mainly dependent on the need and magnitude for shore protection vis-à-vis availability of resources and
environmental impacts.
      It is further recommended that regular monitoring of beach nourishment projects should be conducted for
continuous assessment of performance efficiency and effectiveness as shore protection method.

Acknowledgement:
 The original beach nourishment data was provided by Department of Civil Engineering, Okinawa Prefectural
Government Office. Thus, authors would like to extend their special acknowledgement.

References
Beach nourishment data in Florida (Original data is downloaded from the (super) beach nourishment homepage;
  http://beach15.beaches.fsu.edu/
Bird, E.C.F.. Artificial beach nourishment on the shores of Port Phillip Bay, Australia, Journal of Coastal
  Research Special issue No. 6, 1990 pp. 55-68.
Campbell, T.G., R.G. Dean, A.J. Mehta, and H. Wang. 1990. Short Course on Principles and Application of Beach
  Nourishment. Organized by the Florida Shore and Beach Preservation Association and Coastal and
  Oceanographic Engineering Department, University of Florida.
Dean, Robert G.. Beach Nourishment Theory and Practice, World Scientific, Advanced Series on Ocean
  Engineering – Volume 18, 2002.
Dette, H., A. Fuhrboter, and A.J. Raudiv. 1994. Interdedependence of beach fill volumes and repetition intervals,
  Journal of Waterway, Port, Coastal and Ocean Engineering 120(6):580-593.
Hamm, L., H. Hanson, M. Capobianco, H. H. Dette, A. Lechuga, and R. Spanhoff., 1998. Beach fills in European
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Hanson, H., and N.C. Kraus. 1989. GENESIS: Generalized model for simulating Shoreline change. Report 1:
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Houston, J.R., 1995. Beach nourishment. Shore and Beach 63(1):23-24
Leonard, L. A., Dixon, K. L. and Pilkey, O. H. A comparison of beach nourishment on the U.S. Atlantic, Pacific,
  and Gulf Coasts, Journal of Coastal Research Special Issue No. 6, 1990. pp.127-140.
Massel, S.R. and Gourlay, M.R. On the modeling of wave breaking and set-up on coral reefs, Coastal
  Engineering, An international journal for coastal, harbour and offshore engineers, Volume 39, N0.1, Elsevier,
  2000.
National Research Council. Beach Nourishment and Protection. National Academy Press, 1995.
Nishi, R., Dean, R.G., Tanaka, R. Project scale and cost of beach nourishment in Japan, Annul Journal of Civil
  Engineering in the Ocean. Volume 2, 2005 pp. 355-360.
USACE. 1991b. National economic Development Procedures Manaul Coastal Storm Drainage and Erosion.
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Verhagen , H.J. 1990. Coastal protection and dune management in the Netherlands, Journal of Coastal Research
  6:169-179.

				
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