Loe Bar

Loe Bar is the ridge of sand and shingle between Loe Pool and the Atlantic sea. Loe Bar is recognised as a site of outstanding historical, geomorphological and conservation interest.

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Formation of Loe Bar

Legend of Jan Tregeagle

Legend of Jan Tregeagle pouring sand

Until recently there has bee little agreement about the bar’s origins and exactly how and when it was formed. Old folk tales tell of the ghost of Jan Tregeagle dropping a bag of sand across the mouth of the Cober.

The formation of Loe Bar is now believed to be linked to changes much further back in history. During the last Ice Age the sea level was over 100 metres lower than today; as the earth warmed up, the massive ice sheets covering the land began to melt and they deposited millions of tonnes of eroded materials which had been carried within the ice.

As the ice continued to melt, sea levels began to rise and as a result these deposits, now part of the sea, were gradually moved back towards the land. Although this movement of material was a  very gradual  process, the original blocking of the River Cober to form the bar is likely to have been the result of a series of dramatic storms over a few winters. These would have thrown up the materials that had built up off shore into the mouth of the River Cober, beginning the formation of Loe Bar. Thus the bar’s origins are likely to date back some 5-6,000 years, when the sea level around Cornwall reached its present height.

Loe Bar is growing

There are a number of processes and factors which have modified Loe Bar over the centuries. The process of longshore drift plays a significant part. On every tide a strong south easterly current runs along the beach system which links Porthleven to Gunwalloe, depositing shingle on the bar. However, the ebb current of the tide does not run directly opposite to this, so as a result the bar is actively being built (accreting) with new material. Winter storms also add to the process of accretion of new material. Enormous waves produced by Atlantic weather systems can deposit hundreds of tonnes of new material onto the bar and on occasion will over top it completely, again adding new material and continuing the process of stabilisation.

Breaking the Bar

Breaking the Bar in 1979

Breaking the Bar in 1946

As the bar became wider and more consolidated it became more impermeable and less fresh water was able to percolate through to the sea. The water level of the pool would often increase and then break out suddenly and spontaneously. These events were often linked to winter storms blocking the original drainage adit between the bar and the sea, causing a backup of water and leading to flooding in the lower parts of Helston.

As a result the bar would also be breached artificially to let water drain from the pool more quickly in an attempt to prevent any floods. The Mayor of Helston, in an ancient ritual, would apply to the Lord of Penrose Manor for permission to cut the bar. Permission obtained, the men of Helston shovelled a channel through the bar, allowing the water to rush out to sea. The bar would remain breached until naturally sealed by shingle movement.

Original adit

Old adit

During the time it remained open, salt water and sea creatures could enter the Loe. During the sixteenth century economic pressures caused the bar to be cut artificially when the town mills were stopped by the backlog of water during the winter. Between 1848 and 1874 the bar broke or was cut about once every two years.

After the breaking of the bar in 1874 it was recorded that ‘a great part of the bed of the lake may be traversed on foot; the eastern creek called Carminowe alone remains a large body of water and a river of considerable depth still flows out through the channel…whilst the channel [through the bar] remains open herrings, flounders and shrimps find their way into the lake and are shut in.’ The time it took to flush the lake of saline water was dependent on the degree of rainfall within the river catchment. Flooding and bar cutting continued late into the nineteenth century.

Construction of adit in 1986

Construction of modern adit

Some flood water relief was provided by the tunnel or adit cut through the rock at the northern end of the bar. This was originally cut in 1790 by the miners at nearby Castle Wary silver mine to prevent their workings from flooding. As the width of the bar increased this adit became blocked from time to time until Captain Rogers enlarged it in 1887. The resulting flow of water from the lake kept the adit generally free from blockage.

However, the adit did continue to block and channels had to be bulldozed through the bar by South West Water in 1979 and 1984. Finally in 1986 the Water Authority provided the adit with a smooth bore concrete lining to improve its flow. In addition, they lengthened the tunnel by 100 metres and provided the upgraded sluice gate which controls the water flow from, and levels of, the pool. This sluice gate is clearly visible at the northern boundary of pool and bar.

Adit in Loe Bar to control water levelsOver the course of time the shape of the bar was dictated by the frequent breakages with the narrowest and weakest section being the site of both natural and man-made channels today. An indented profile on the inner side of the bar illustrates where the 1984 channel was cut. Many of the visible irregularities on the surface are a result of sediment splays caused by large storm waves.

However, the end of cutting has allowed the bar to return to its natural growth through onshore deposition (accretion). In turn this renewed increase in shingle accumulation, combined with the clogging effect of huge quantities of mining waste, has meant less water loss through the bar. Essentially all the lake overflow now travels through the adit.

Managing a Shifting Shoreline

Coastlines are dynamic, and constantly changing as a result of the sea’s actions. This dynamism is likely to increase in the future because of climate change and sea level rise. In recent years, there has been growing recognition that the shifting nature of coastlines must be accepted and that there must be limits to the amount of coastal defence carried out. This philosophy underpins the National Trusts Shifting Shores Policy, which is explained here in a video narrated by Kate Humble.

A shifting shoreline will have a number of implications for Loe Bar, Loe Pool and the National Trusts Penrose estate.

  • Accretion, or the building up of new material at Loe Bar, may produce new wildlife habitats which in turn can protect access, land and buildings.
  • Access may be adversely affected through the loss of footpaths or car parks.
  • Buildings may be lost, or demolished for reasons of safety. For example, increasing coastal erosion in the area of Bar Lodge could present an interesting dilemma for the future. Would the National Trust surrender the building to the sea, demolish it or invest in its repositioning?
  • Archaeological features may be affected. In some cases these may be lost as a result of erosion, in others they may be exposed and become available for study.

Whatever the outcome of coastal erosion there are considerable public relations consequences. Some of the effects of erosion will be permanent, but others may be temporary. The provision of access may be in the latter category, providing that facilities such as footpaths can be replaced. However, replacement may only be practical if provision for erosion is made in advance, for example by ensuring that land is available on which to locate a new footpath.

Acceptance of the dynamic nature of the coast implies the acceptance that land in the Trust’s care will change with time. This deliberate yielding of land is called ‘managed retreat’. On first impressions this could be seen as contrary to ‘permanent preservation’, but the Trust has had to accept that it cannot protect everything for ever.

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