Coastal cliff behaviour & management: Blackgang, Isle of Wight

In January 1994 coastal erosion and landslide activity at Blackgang, Isle of Wight, resulted in a dramatic retreat of the coastal cliffs and landward extension of ground movement. The initial impact of the event involved the destruction of two cottages, an access road, several cars and caravans, and around 12 homes had to be evacuated. The event raised considerable local and national media attention. The initial landslide response was co-ordinated by South Wight Borough Council, with advice from Rendel Geotechnics, and was aimed at ensuring public safety and security in the area. A detailed investigation was subsequently carried out to identify the extent and causes of coastal instability and cliff recession in the context of ‘cliff behaviour units’. An understanding of the characteristic cliff behaviour units has proved the key to assessing future landslide and cliff recession potential as well as identifying options for coastal cliff management at Blackgang. The coastal cliffs have been significantly oversteepened by the latest events and appear to be very sensitive to rainfall, with only relatively moderate to high winter rainfall totals expected to cause further cliff-top retreat and landslide reactivation. Consequently, in the absence of a financially and environmentally acceptable slope stabilization and coast protection scheme, continued managed retreat of cliff-top development and land use is seen as the only viable option.