**Parking: There is plenty of parking in Wexford near the earthcache. All parking in Wexford is Paid Parking.
Coastlines are in constant flux; coastal erosion and coastal deposition will alter the coastline over time, often quite significantly. Depending on the land use the erosion/deposition can have an economic or ecological impact and should, therefore, be managed.
Coastal management includes creating defences against flooding and erosion and also techniques that stop erosion. It is not possible to completely stop the power of nature. Prior to the 1950s, hard structures were used to protect against beach erosion or storm damage. Nowadays, projects attempt to replicate the protective characteristics of natural beach and dune systems, this is economically viable and more environmentally friendly. The choice of strategy is always site-specific - many factors are taken into consideration: pattern of sea-level change, geomorphological setting, sediment availability, erosion, along with social, economic and political factors.
Local Authorities have a number of options:
Holding the line involves hard engineering techniques: seawalls, groynes, breakwaters and revetments along with soft engineering techniques: supporting natural processes/elements such as dunes and vegetation.
Managed retreat is used when the land adjacent to the sea is low in value. The land is allowed to erode and flood, creating new shoreline habitats. In some cases, armouring is used to protect land beyond the area to be flooded.
Moving Seaward. If the sea rises, infrastructure along/close to the shoreline will experience ‘coastal squeeze’ - ecological or geomorphological zones that would normally retreat landwards encounter solid structures and can migrate no further. Wetlands, salt marshes and freshwater wetlands are vulnerable to squeeze.
Limited intervention often includes the succession of salt marshes and sand dunes. This normally results in protecting the land behind the salt marsh, as wave energy dissipates through the accumulated sediment and additional vegetation in the new habitat.
Hard Engineering Methods
Groynes are small wooden/stone walls perpendicular to the coastline placed to trap the sedimentation of longshore drift. The material builds up on the downdrift side, creating a wider and a more plentiful beach. The coast is protected because the sand material filters and absorbs wave energy. However, there is a corresponding loss of beach material on the updrift side, requiring another groyne there. Groynes do not protect the beach against storm-driven waves and if placed too close together create currents that carry material offshore. They are cost-effective, require little maintenance and are one of the most common defences. Though they also prevent longshore drift from bringing material to other nearby places; a problem known as terminal groyne syndrome.
Old-style vertical Seawalls reflected all the waves’ energy back out to sea. They were often given recurved crest walls which increased local turbulence, which increased entrainment/transport of sand and sediment. During storms, sea walls assist longshore drift.
Modern seawalls re-direct most of the energy in the form of sloping revetments, resulting in low reflected waves and much reduced turbulence. Seawalls use porous designs of rock and concrete armour with flights of steps for beach-access. They can cause beaches to dissipate and their presence also alters the landscape that they are trying to protect.
Revetments are slanted or upright blockades, built parallel to the coast, towards the back of the beach to protect the area beyond. Basic revetments consist of timber slants with a possible rock infill. Waves break against the revetments, where the energy is dissipated and absorbed. The shoreline is protected by the beach material held behind the barriers, as the revetments trap some of the material. They may be watertight, covering the slope completely, or porous, to allow water to filter through. Most revetments do not significantly interfere with transport of longshore drift. Since the wall absorbs energy instead of reflecting, the surf progressively erodes and destroys the revetment; therefore, maintenance is ongoing.
Rock armour is large rocks placed at the sea edge using local material. This is used to absorb wave energy and hold beach material. While it is effective, it is aesthetically unattractive. Longshore drift is not hindered. Rock armour has a limited lifespan, and can be undermined in storms.
Gabions: Boulders and rocks are wired into mesh cages and placed in front of areas vulnerable to erosion: sometimes at cliffs edges or at right angles to the beach. When the waves crash on the gabion, the water drains through leaving sediment, while the structure absorbs a moderate amount of wave energy. They need to be securely tied to protect the structure.
Offshore breakwater: Concrete block/boulders are sunk offshore to alter wave direction and to filter wave and tide energy. The waves break further offshore and therefore lose erosive power. This leads to wider beaches, which further absorb wave energy. Dolos (complex geometric concrete block) has become more popular in recent years; it is more resistant to wave action and requires less concrete.
Cliff Stabilisation can be accomplished through drainage of excess rainwater or through terracing, planting and wiring to hold cliffs in place.
Entrance Training Walls are built to constrain a river as it discharges across a sandy coastline. The walls stabilise and deepen the channel which benefits navigation, flood management, river erosion and water quality, but can cause coastal erosion by interrupting longshore drift.
Storm Surge Barriers/Floodgates prevent damage. They are habitually open and allow free passage, but close under threat of a storm surge.
Soft Engineering Methods
Beach Replenishment/nourishment involves importing sand from elsewhere and adding it to the existing beach. The imported sand should be of a similar quality to the existing beach material so it can meld with the natural local processes and without adverse effects. Beach nourishment can be used in combination with groynes. The scheme requires repeated applications on an annual or multi-year cycle.
Dune Stabilisation can help protect beaches by catching windblown sand, increasing natural beach formation. This involves public amenities such as car parks, footpaths, Dutch Ladders and boardwalks to reduce erosion and the removal of sand by humans. Noticeboards explain to visitors how to avoid damaging the area. Fences can allow sand traps to create blowouts (sandy depressions in dunes caused by wind erosion) and increase windblown sand capture. Plants such as Marram grass can bind the sediment.
Beach Drainage lowers the water table beneath the beach face. This causes accretion of the sand (growth by gradual accumulation of layers).
Beach water tables have an important bearing on deposition/erosion across the foreshore. Beach drainage systems have been installed in many locations around the world to halt and reverse erosion trends in sand beaches.
The Future
Coastal management is hugely important as the position of the shoreline in the past, at present and where it is predicted to be in the future is useful for in the design of coastal protection, to calculate and predict sea-level rise, to map hazard zones and to regulate coastal development.
This cache
To log this earthcache please answer the following questions and send them via the messanger.
- Which option has Wexford County Council adopted in their Coastal Management?
- In doing this what elements of coastal management are evident in this general vicinity?
- Are they hard or soft engineering methods?
- In order to prove you were at GZ, please tell me what Rule 5 states on the Warning Sign.
- A photo of you along Wexford’s Coast would be nice, though not compulsory.