It is known for having been the home of Dylan Thomas from 1949 until his death in 1953, and is thought to have been an inspiration for the fictional town of Llareggub in his play “Under Milk Wood.
This cache is about the natural topography and man's impact on it, through the choice of flood defences in the estuary. Is it a blessing or a curse?
Carmarthen Bay is formed by the estuaries of the rivers Taf, Tywi and Gwendraeth where they enter the sea between the Carboniferous Limestone headland of Worms Head on the Gower Peninsula and Caldey Island. It has the second highest tidal range in the world after the Bay of Fundi, in Canada.
Carmarthen Bay has perhaps the most varied assemblage of coastal features in the British Isles and is one of the few sites with limited anthropogenic disturbance. There are major dunes, sand spits and barrier beaches, both hard-rock and easily eroded cliffs, rias, emerged (‘raised') beaches, extensive intertidal sand-flats and some of the most important salt marshes in England and Wales.
You are standing close to the mouth of an estuary which is a partly enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. It is one of the few areas in the UK exposed directly to the Atlantic Ocean.
It was formed by rising sea levels, when river valleys were flooded and thus forming a drowned river valley or coastal plain estuaries, and by the movement of sand and the formation of sandbars which enclosed bodies of water along the coastline and formed lagoon-type or bar-built estuaries.
Most local estuaries were formed during the Holocene epoch with the flooding of river-eroded or glacially scoured valleys when the sea level began to rise about 10,000–12,000 years ago
Some flood risk management improvements have recently been undertaken including individual flood protection and flood warnings to local properties.
There remains a strong risk of coastal flooding (and erosion) to Laugharne village since a surge barrier was not constructed, as the local community were primarily concerned with the associated aesthetic impact on the village
The shoreline management plan accepted by Laugharne recommends mainly “managed realignment”, to allow the dune system and mud flats to function naturally.
It's a fascinating landscape, and some of this land has been reclaimed from the sea using a series of drainage ditches or 'reens' built in the 1600s . The mud flats are rich in wildlife with all kinds of visiting wading birds, fish and seals and the occasional peregrine falcon.
However in January 1607, there was flood devastation which was particularly severe, extending from Laugharne in Carmarthenshire to above Chepstow in Monmouthshire
Floods resulted in the drowning of an estimated 2,000 or more people, with houses and villages swept away, an estimated 200 square miles (51,800 ha) of farmland inundated and livestock destroyed, wrecking the local economy along the coasts of the Bristol Channel and the Severn Estuary
The cause of the flood remains disputed, insofar as contemporary, (1607), explanations blamed God.
Subsequent scientific explanations ignored much of the written evidence and blamed bad weather, until recent research suggests a tsunami. Traditionally it had been believed that the floods were caused by a storm surge, a combination of meteorological extremes and a high tide.
Written evidence from the time describes events that were similar to those that unfolded in the 2004 Indian Ocean Tsunami, including the sea receding before the wave arrived, a wave of water that rushed in faster than men could run, sparks coming off the top of the wave, and a crowd of people who stood and watched the wave coming towards them until it was too late to run. Some of the most detailed accounts also state that it had been a sunny morning
A BBC programme exploring the theory, “The Killer Wave of 1607”, was made as part of the "Timewatch" series. You may be able to watch this on YouTube?
Haslett and Bryant found significant evidence for the tsunami hypothesis. This included: massive boulders that had been displaced up the beach by enormous force; a layer up to 8 inches (20 cm) thick composed of sand, shells and stones within an otherwise constant deposit of mud that was found in boreholes from Devon to Gloucestershire and the Gower Peninsula; and rock erosion characteristic of high water velocities throughout the Severn Estuary
There are however similarities to descriptions of the 1953 Floods in East Anglia which were caused by a storm surge. Some of the original sources frequently referred to the high spring tide and strong winds from the southwest, classic conditions for a storm surge. Horsburgh and Horritt have shown that the tide and probable weather at the time were capable of generating a surge that is consistent with the observed inundation.
Laugharne’s chosen policy is of “managed realignment” in order to allow natural coastal evolution, whilst continuing to manage flood and erosion risk to Laugharne village.
Managed realignment is a relatively new soft engineering strategy undertaken to provide sustainable coastal defences, re-create intertidal habitats or a combination of these two aims.
It involves designing new intertidal areas, created from formerly flood defended areas of coastal land in order to provide sustainable flood defences, new intertidal habitats or a combination of these.
Existing ‘hard’ defences such as concrete walls and embankments are often expensive to maintain and have been identified as a contributing factor to the erosion and subsequent loss of salt marshes and mudflats around the coastline.
In a natural undefended coastline, marshlands would react to changes in sea level or erosion by shifting position to a more suitable location in the tidal range, but this is constrained where such migration is impeded by flood defence structures. This erosion has been discovered to not just be a loss of intertidal habitat, but also of serious consequence to flood defence engineering, as salt marshes reduce the erosive force and overtopping potential on flood defence structures (Brampton, 1992).
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THE OPTIONS ( You might find these helpful in responding to the first task)
Hard engineering
Building a sea wall - A wall built on the edge of the coastline
Protects the base of cliffs, land and buildings against erosion. Can prevent coastal flooding in some areas.
Disadvantages
Expensive to build. Curved sea walls reflect the energy of the waves back to the sea. This means that the waves remain powerful. Over time the wall may begin to erode. The cost of maintainance is high
Building groynes - A wooden barrier built at right angles to the beach.
Prevents the movement of beach material along the coast by longshore drift.
Allows the build up of a beach. Beaches are a natural defence against erosion and an attraction for tourists.
Disadvantages
Can be seen as unattractive and is costly to build and maintain
Rock armour or boulder barriers - Large boulders are piled up on the beach.
Advantages
Absorb the energy of waves.
Allows the build up of a beach.
Disadvantages
Can be expensive to obtain and transport the boulders
Soft engineering
Soft engineering options are often less expensive than hard engineering options. They are usually more long-term and sustainable, with less impact on the environment. There are two main types of soft engineering;
Beach management
This replaces beach or cliff material that has been removed by erosion or longshore drift.
The main advantage is that beaches are a natural defence against erosion and coastal flooding. Beaches also attract tourists.
It is a relatively inexpensive option but requires constant maintenance to replace the beach material as it is washed away.
Managed retreat
Areas of the coast are allowed to erode and flood naturally. Usually this will be areas considered to be of low value - eg places not being used for housing or farmland.
The advantages are that it encourages the development of beaches(a natural defence) and salt marshes (important for the environment) and cost is low.
Managed retreat is a cheap option, but people will need to be compensated for loss of buildings and farmland.
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DO GO to the coordinates and assess the problem for yourself. Log the cache, and email you response to the following. I will reply as quickly as possible. (PICTURES ARE WELCOMED BUT please don’t post photos which would allow others to complete the cache from home!!)
LOGGING TASKS
Look towards the sea. What do you see, in front of you, that looks a deliberate attempt at flood prevention?
What are the risks of the flood defence solution chosen in Laugharne?
Why do you think has this solution been actively selected? What's your view? A blessing or a curse?
Locate the flood gauge. It has been moved to the left of the car park entrance. What is the “red zone” danger range, and what is its unit of measurement?
...Well done .... Jabawokee... on your FTF in abysmal weather too!!!...
