Beach Nourishment 29.8 Summary and Conclusions 649
Part C | 29.8
the adjacent Sanibel Island. Captiva Island has two terminal groins to help reduce losses from the island.
29.7.3 Treasure Island, FL
Treasure Island is a 5:3 km barrier island bordered
by Johns Pass to the north and Blind Pass (a different Blind Pass than adjacent to Captiva Island) to the
south. Treasure Island grew to its present size after
a tidal inlet at the north end of the island closed and
the southern migration of Blind Pass caused the island
to lengthen. Development of resorts on the island began
in the 1920s followed by a surge in development in the
1950s. By the 1960s, the island was facing serious erosion problems. In response, the city of Treasure Island
constructed 56 concrete (originally timber) groins and
a rubble mound jetty on the north side of Blind Pass. At
the time, the average erosion rate was determined to be
52 000 m
3
=year [29.27].
The first nourishment project on the west coast of
Florida was on Treasure Island in 1969. After the initial
construction and repair following Hurricane Gladys in
1968, Treasure Island was renourished every 2–3 years.
The material used for the nourishments was sourced
from Blind Pass, Johns Pass, and an offshore sand pit
parallel to the island. Sunshine and Sunset beaches required frequent nourishment.
Sunshine Beach, at the north end of Treasure Island,
is historically erosional as a result of inlet effects. The
only times that Sunshine Beach has been accretional
was after a nourishment in the 1970s when dredge material deposited in shallow offshore waters migrated
onshore. In 1989, an angled structure was constructed
to protect development to the south [29.28]. No evidence was found on why or when it was removed.
A terminal groin was constructed on the south side of
Johns Pass in 2000 to limit the end losses from Sunshine Beach to the inlet. Prior to its construction, the
shape and beach width at Sunshine Beach fluctuated
significantly. After the groin construction, the beach
was fixed and straight, limited by the effective length
of the groin.
29.8 Summary and Conclusions
Large-scale designed beach nourishment projects are
the result of a relatively young technology and thus issues expected to be dominant in the next century or so
are still evolving. However, the major emerging issues
are discussed below.
Energy Costs
Dredging is a process requiring fairly large amounts
of energy. High velocities must be maintained in the
pipeline delivering the sand–water mixture to prevent
sand from settling and blocking the pipe. Some projects
are located at substantial distances from the borrow areas and may require a booster pump which increases the
energy costs. Currently (2012), in the United States, energy costs are approximately one-third of the total. Although future innovations in dredging technology may
reduce energy costs per volume of sand delivered a specific distance, these improvements are not expected to
reduce energy requirements by more than 25%.
Environmental Issues
Beach nourishment has been shown to both temporarily impact and to be a long-term benefit to the beach
environment. Certainly a nourished sandy beach provides more benefits to the biota than an armored beach
which could be either a seawall or a revetment. In the
State of Florida where many sea turtles nest, it has been
found that, compared to prenourishment nesting density, usually a reduction in nesting density will occur for
several years after which the turtles will return to their
prenourishment nesting activities. Beach nourishment
and society would benefit by a more balanced environmental assessment of the beneficial and adverse impacts
of beach nourishment including the adverse impacts of
a do-nothing approach.
Limited Sand Resources
The availability of offshore sand resources varies
widely with location depending on its geologic history.
The relatively large deposits of sand in ebb tidal shoals
have been utilized for nourishment in some projects. In
some areas, the volumes of good quality offshore sand
resources are quite abundant whereas at others, quantities are quite limited. In southeast Florida, limited sand
resources tend to be located between offshore reefs that
are generally approximately parallel to the shoreline.
Along some counties in this area, the offshore sources
of large quantities of readily available, good quality
sand have been nearly depleted. In some areas, sand
from previous nourishments has evolved to uneven distributions along the project area, resulting in programs
to redistribute the sand along the project rather than provide additional sand. In other areas, additional sand has
been provided by truck haul from inland sources as discussed earlier. The limitations of truck haul and damage
to roads have been discussed. One possibility would be
to deliver sand from inland quarries to the shore by dedicated pipelines and then transport this sand by dredge
Part C | 29.8
the adjacent Sanibel Island. Captiva Island has two terminal groins to help reduce losses from the island.
29.7.3 Treasure Island, FL
Treasure Island is a 5:3 km barrier island bordered
by Johns Pass to the north and Blind Pass (a different Blind Pass than adjacent to Captiva Island) to the
south. Treasure Island grew to its present size after
a tidal inlet at the north end of the island closed and
the southern migration of Blind Pass caused the island
to lengthen. Development of resorts on the island began
in the 1920s followed by a surge in development in the
1950s. By the 1960s, the island was facing serious erosion problems. In response, the city of Treasure Island
constructed 56 concrete (originally timber) groins and
a rubble mound jetty on the north side of Blind Pass. At
the time, the average erosion rate was determined to be
52 000 m
3
=year [29.27].
The first nourishment project on the west coast of
Florida was on Treasure Island in 1969. After the initial
construction and repair following Hurricane Gladys in
1968, Treasure Island was renourished every 2–3 years.
The material used for the nourishments was sourced
from Blind Pass, Johns Pass, and an offshore sand pit
parallel to the island. Sunshine and Sunset beaches required frequent nourishment.
Sunshine Beach, at the north end of Treasure Island,
is historically erosional as a result of inlet effects. The
only times that Sunshine Beach has been accretional
was after a nourishment in the 1970s when dredge material deposited in shallow offshore waters migrated
onshore. In 1989, an angled structure was constructed
to protect development to the south [29.28]. No evidence was found on why or when it was removed.
A terminal groin was constructed on the south side of
Johns Pass in 2000 to limit the end losses from Sunshine Beach to the inlet. Prior to its construction, the
shape and beach width at Sunshine Beach fluctuated
significantly. After the groin construction, the beach
was fixed and straight, limited by the effective length
of the groin.
29.8 Summary and Conclusions
Large-scale designed beach nourishment projects are
the result of a relatively young technology and thus issues expected to be dominant in the next century or so
are still evolving. However, the major emerging issues
are discussed below.
Energy Costs
Dredging is a process requiring fairly large amounts
of energy. High velocities must be maintained in the
pipeline delivering the sand–water mixture to prevent
sand from settling and blocking the pipe. Some projects
are located at substantial distances from the borrow areas and may require a booster pump which increases the
energy costs. Currently (2012), in the United States, energy costs are approximately one-third of the total. Although future innovations in dredging technology may
reduce energy costs per volume of sand delivered a specific distance, these improvements are not expected to
reduce energy requirements by more than 25%.
Environmental Issues
Beach nourishment has been shown to both temporarily impact and to be a long-term benefit to the beach
environment. Certainly a nourished sandy beach provides more benefits to the biota than an armored beach
which could be either a seawall or a revetment. In the
State of Florida where many sea turtles nest, it has been
found that, compared to prenourishment nesting density, usually a reduction in nesting density will occur for
several years after which the turtles will return to their
prenourishment nesting activities. Beach nourishment
and society would benefit by a more balanced environmental assessment of the beneficial and adverse impacts
of beach nourishment including the adverse impacts of
a do-nothing approach.
Limited Sand Resources
The availability of offshore sand resources varies
widely with location depending on its geologic history.
The relatively large deposits of sand in ebb tidal shoals
have been utilized for nourishment in some projects. In
some areas, the volumes of good quality offshore sand
resources are quite abundant whereas at others, quantities are quite limited. In southeast Florida, limited sand
resources tend to be located between offshore reefs that
are generally approximately parallel to the shoreline.
Along some counties in this area, the offshore sources
of large quantities of readily available, good quality
sand have been nearly depleted. In some areas, sand
from previous nourishments has evolved to uneven distributions along the project area, resulting in programs
to redistribute the sand along the project rather than provide additional sand. In other areas, additional sand has
been provided by truck haul from inland sources as discussed earlier. The limitations of truck haul and damage
to roads have been discussed. One possibility would be
to deliver sand from inland quarries to the shore by dedicated pipelines and then transport this sand by dredge