Happisburgh Landslide Observatory

BGS Research — Landslides

Happisburgh, on Norfolk’s North Sea coast, is a village with a population of 1400 people in about 600 houses. The village contains a notable stone church dating from the 14th century, an impressive manor house, listed buildings and a famous red-and-white striped lighthouse.

Although now a coastal village, Happisburgh (pronounced haze-bruh) was once some distance from the sea, parted from the coast by the parish of Whimpwell, long since eroded away. Historic records indicate that over 250 m of land were lost between 1600 and 1850.

More recently, the village was affected by the tragic floods of 1953 that claimed the lives of 76 Norfolk residents.

Coastal defences built at Happisburgh have slowed down the rate of retreat. However, large sections are now in disrepair. Sea-level rise and climate change, including increased storminess, may also increase the rate of erosion.

Agriculture and tourism contribute significantly to the economy of the village and surrounding hinterland, although this is threatened by the receding cliff line. Prior to the construction of a rock embankment at the northern end of the survey site, the erosion had claimed at least one property per year plus significant quantities of agricultural land.

Geology

The cliffs at Happisburgh range in height from 6 to 10 m and are composed of a layer-cake sequence of several glacial tills, separated by beds of stratified silt, clay and sand (Hart, 1987; Lunkka, 1988; Hart, 1999; Lee, 2003).

The basal unit within the stratigraphical succession at Happisburgh is the How Hill Member of the Wroxham Crag Formation. These deposits are typically buried beneath modern beach material but are periodically exposed following storms. They consist of stratified brown sands and clays with occasional quartzose-rich gravel seams that are interpreted as intertidal or shallow marine in origin.

Unconformably overlying these marine deposits are a series of glacial lithologies deposited during several advances of glacier ice into the region during the Middle Pleistocene (around 780 to 430 ka BP) (Lee et al., 2002; Lee et al., 2004). The survey site has a tripartite geological succession.

The Happisburgh Till Member crops out at the base of the cliffs and its base is frequently obscured by modern beach material: it has a maximum thickness of 3 m. The Happisburgh Till Member is a dark grey, highly consolidated till with a matrix composed of a largely massive clayey sand with rare (<1 per cent) pebbles of local and far-travelled material.

The upper surface of the till undulates and comprises a series of ridges and troughs upon which the overlying ‘Ostend Clay’ crops out. This unit is between 2.3 and 3.4 m thick and consists of thinly laminated, light grey silts and dark grey clays.

In turn, these beds are overlain by 2 to 4 m of weak, stratified sand (Happisburgh Sand Member) with occasional silty-clay horizons.

The geology of the cliffs at Happisburgh.
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The geology of the cliffs at Happisburgh.

Coastal erosion

It is likely that the Norfolk cliffs have been eroding at the present rate for about the last 5000 years, when the sea level rose to within a metre or two of its present position (Clayton, 1989). Therefore, the future predictions of sea-level rise and storm frequency due to climate change are likely to have a profound effect on coastal erosion and serious consequences for the effectiveness of coastal protection and sea-defence schemes in East Anglia in the near future (Thomalla and Vincent, 2003).

Rapid erosion of the cliffs at Happisburgh means that we can observe processes that may normally take thousands of years at other sites. This means that we can look for patterns in the erosion at Happisburgh, which may help our understanding of sites elsewhere that are eroding more slowly.

Surveying activity

As part of a programme of work monitoring coastal erosion and landsliding at several sites around the coast of Great Britain, we are surveying the cliffs adjacent to the village of Happisburgh in Norfolk with terrestrial LiDAR scanning. The resulting computer model enables volume calculations and observations to be made as to the way in which the coast is eroding. The results from the survey provide data for models of coastal recession.

From this survey, the following conceptual model has been proposed:

  1. In winter, erosion caused by groundwater (as seen in the gullying of the cliff face), coupled with increased seasonal storminess, causes small-scale, frequent, shallow landsliding in the Happisburgh Sand Member. The Happisburgh Sand Member is easily eroded and undercutting of the cliff toe reduces slope stability and cliff failure occurs. The beach surface is low and scouring of the upper surface of the till extends the till platform.
  2. In summer, the beach surface is higher and covers the ‘winter platform’. Wave attack is the dominant form of erosion accompanied by landsliding in the Happisburgh Sand Member.

The cliff surface profiles show that the erosion process is non-uniform, involving the cyclic formation of a series of embayments that continually enlarge. This could infer landsliding processes involving block falls, mudflows and running sand.

References

Hobbs, P R N, Pennington, C V L, Pearson, S G, Jones, L D, Foster, C, Lee, J R, and Gibson, A. 2008. Slope Dynamics Project Report: Norfolk Coast (2000-2006), British Geological Survey Open Report OR/08/018. (Nottingham, UK: British Geological Survey.) (Unpublished.)

Poulton, C V L. 2004. Disappearing coasts. Planet Earth, Vol. Summer 2004, 26–27.

Poulton, C V L, Lee, J R, Jones, L D, Hobbs, P R N, and Hall, M. 2006. Preliminary investigation into monitoring coastal erosion using terrestrial laser scanning: case study at Happisburgh, Norfolk, UK. Bulletin of the Geological Society of Norfolk, No. 56, 45–65.

Contact the Landslide Response Team

Tel: 0115 936 3143 Email: landslides@bgs.ac.uk

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