This earthcache is on a public beach and is available 24 hours a
day.
Introduction
In 90s, state of Louisiana was trying to find a way to slow the
erosion of the beach which was jeopardizing Highway 82. They began
with six breakwaters – five using timber and tires and one using
stone rubble. After looking at the results, they found the stone
rubble seemed to work the best, so from 1990 to 1994,
numerous more along the coast line to help slow erosion.
Since then, the area has seen the re-introduction of viable beach
for public use, as well as an increased protection of the adjacent
highway and marshlands beyond.
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History
The area between Holly Beach and Ocean View Beach was once a
beautiful beach, with natural dunes protecting it from State
Highway 82 and adjacent coastal marshland. However, since 1947, the
area has seen significant erosion. In fact, the average loss of
beach was 1.8 feet per year.
This can be attributed to the decrease in sedimentation from the
Mississippi River, plus changes in the Atchafalaya River, the
Calcasieu River and the Mermentau River. Plus, the Jetties
associated with the Calcasieu Ship Channel deflect what little
material that exists away from the project area.
Due to this erosion, State Highway 82 has been relocated inland
several times. In the 1960s and 70s, revetments were constructed
further protect the highway from destruction, however, maintenance
of the revetments became a costly endeavor. |
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The importance of Highway 82
The highway is an integral transportation artery to the
southwestern Louisiana coast and serves as a hurricane evacuation
rout for the communities of Holly Beach, Constance Beach, Peveto
Beach, Ocean View Beach and Johnson’s Bayou. The highway sits on a
chenier, the only barrier between the Gulf of Mexico and 31,000
acres of marshland. Without this protective effort, the loss of
more than 11,000 acres of marsh was predicted over the next 20
years, creating a devastating destruction of habitat for fish,
wildlife and waterfowl.
The Solution
In 1985, six experimental breakwaters were constructed to test
beach response. Five of the six were timber and tires, the sixth
was a rock rubble mound structure. Data was collected for eight
months, and the rock rubble construction was seen as the best
solution for erosion control.
In 1991, construction began on what was then the largest
breakwater system in the United States. A total of 34 breakwaters
were constructed in 1991, 21 breakwaters were constructed in 1992,
21 breakwaters were constructed in 1993, and nine breakwaters were
constructed in 1994 between Calcasieu Pass and Holly Beach,
Louisiana.
In August, 2002 the Holly Beach Sand Management Project began
with the removal of the first six breakwaters, followed by 1.75 M
cubic yard beach nourishment to protect State Highway 82 and the
coastal communities of Holly Beach and Gulf Breeze. The project
also consisted of installation of sand fencing to promote sand dune
creation.
The Results
Hard structures such as a segmented breakwater field were built to
trap sediment and reduce damage to the beach ridge.
The breakwater field has reduced wave energies but the deficit
of materials moving within the littoral transport system has caused
limited deposition and increased erosion rates downdrift.
The revetments, designed to protect the ridge and highway on top
of the ridge, has already been undermined in some sections and is
in danger of collapse.
The collapse of this barrier would lead to the introduction of
direct wave attack and saltwater intrusion into the fragile coastal
wetlands protected by the ridge. (Source: Louisiana
Department of Natural Resources, Holly Beach to Constance
Beach Segmented Breakwaters Sand Management Project (CS-01),
Project Fact and Information Sheet for Wetland Value Assessment
Coastal Wetlands Planning, Protection, and Restoration Act 9th
Priority List Complex Project)
Definitions
Chenier – A beach ridge, usually composed of
sand-sized material resting on clay or mud.
Revetment – A facing of wood, stone, or any other
material, to sustain an embankment when it receives a slope steeper
than the natural slope; also, a retaining wall.
Breakwater – An artificial offshore structure
protecting a beach from water waves. Breakwaters intercept
longshore currents and tend to prevent beach erosion. Over the long
term, however, the processes of erosion and sedimentation cannot be
effectively overcome by interfering with currents and the supply of
sediment. Deposition of sediment at one site will be compensated
for by erosion elsewhere; this phenomenon occurs whether one
breakwater or a series of such structures is erected.
Logging the Cache
The waypoint will bring you to a breakwater along Holly Beach.
Using your best method, measure the following:
- The length of the breakwater
- The distance between the breakwater and the south side of State
Highway 82
You must also take a picture of your self with the breakwater in
the background and post it with your log.
Please e-mail us your responses to the measurement requirements.
Do not include them in your logs, even if encrypted.
Resources:
Dictionary.com
Louisiana Department of Natural Resources
CONGRATULATIONS TO SpankySCRC FOR FIRST TO FIND!!!