Abstract The UK is perhaps unique globally in that it presents the full spectrum of geological time, stratigraphy and associated lithologies within its boundaries. With this wide range of geological assemblages comes a wide range of geological hazards, whether geophysical (earthquakes, effects of volcanic eruptions, tsunami, landslides), geotechnical (collapsible, compressible, liquefiable, shearing, swelling and shrinking soils), geochemical (dissolution, radon and methane gas hazards) or related to georesources (coal, chalk and other mineral extraction). An awareness of these hazards and the risks that they pose is a key requirement of the engineering geologist. This volume sets out to define and explain these geohazards, to detail their detection, monitoring and management, and to provide a basis for further research and understanding, all within a UK context.

Abstract Tsunami present a significant geohazard to coastal and water-body marginal communities worldwide. Tsunami, a Japanese word, describes a series of waves that, once generated, travel across open water with exceptionally long wavelengths and with very high velocities before shortening and slowing on arrival at a coastal zone. Upon reaching land, these waves can have a devastating effect on the people and infrastructure in those environments. With over 12 000 km of coastline, the British Isles is vulnerable to the tsunami hazard. A significant number of potential tsunami source areas are present around the entire landmass, from plate tectonic boundaries off the Iberian Peninsula to the major submarine landslides in the northern North Sea to more localized coastal cliff instability which again has the potential to generate a tsunami. Tsunami can be generated through a variety of mechanisms including the sudden displacement of the sea floor in a seismic event as well as submarine and onshore landslides displacing a mass of water. This review presents those impacts together with a summary of tsunami triggers and UK case histories from the known historic catalogue. Currently, apart from some very sensitive installations, there is very little in the UK in the way of tsunami management and mitigation strategies. A situation that should be urgently addressed both on a local and national level.

Abstract Metastable soils may collapse because of the nature of their fabric. Generally speaking, these soils have porous textures, high void ratios and low densities. They have high apparent strengths at their natural moisture content, but large reductions of void ratio take place upon wetting and, particularly, when they are loaded because bonds between grains break down upon saturation. Worldwide, there is a range of natural soils that are metastable and can collapse, including loess, residual soils derived from the weathering of acid igneous rocks and from volcanic ashes and lavas, rapidly deposited and then desiccated debris flow materials such as some alluvial fans; for example, in semi-arid basins, colluvium from some semi-arid areas and cemented, high salt content soils such as some sabkhas. In addition, some artificial non-engineered fills can also collapse. In the UK, the main type of collapsible soil is loess, though collapsible non-engineered fills also exist. Loess in the UK can be identified from geological maps, but care is needed because it is usually mapped as ‘brickearth’. This is an inappropriate term and it is suggested here that it should be replaced, where the soils consist of loess, by the term ‘loessic brickearth’. Loessic brickearth in the UK is found mainly in the south east, south and south west of England, where thicknesses greater than 1 m are found. Elsewhere, thicknesses are usually less than 1 m and, consequently, of limited engineering significance. There are four steps in dealing with the potential risks to engineering posed by collapsible soils: (1) identification of the presence of a potentially collapsible soil using geological and geomorphological information; (2) classification of the degree of collapsibility, including the use of indirect correlations; (3) quantification of the degree of collapsibility using laboratory and/or in situ testing; (4) improvement of the collapsible soil using a number of engineering options.

Abstract The late third century Roman fort at Lympne in Kent, one of a series known as the Saxon Shore forts, is one of the earliest substantial stone-built fortifications in SE England. It was sited on the lower slopes of an escarpment, the remnant of a former coastal slope, eroded principally into Early Cretaceous clays capped with sandy limestones. At this location, the escarpment rises to c . 100 m above sea-level. Several episodes of landslip damage during the 17 centuries since its construction can be distinguished, based on evidence of various kinds: notably, the reconstruction of its original layout; the results of both geotechnical and archaeological site investigations; historical evidence; and analogy with sites and experience in adjacent lengths of the escarpment. The landslip damage manifests itself through the toppling and displacement of the curtain wall and projecting towers or bastions of the fort. The specific engineering geological interest arising from discoveries on site is the attribution of the damage to a small number of episodes of major movement rather than to creep; the magnitude of the movements associated with each episode; and the evidence as to their nature and date.

Abstract The viability of any fort or garrison depends on the availability of a reliable water supply. The source of choice is an underlying aquifer, reached by a secure on-site well or borehole. Unfortunately, at coastal and maritime sites, seawater intrusion can cause problems. In the late eighteenth century a deep well was sunk to supply the garrison at Sheerness, Kent, which successfully exploited sands beneath the London Clay. At Landguard Fort in Suffolk, a shallow gallery was designed to skim freshwater overlying saline water within loose sand and shingle. In the mid-nineteenth century, a network of forts was built to defend the Royal Dockyard at Portsmouth, which included some offshore forts on the Spithead shoals. Boreholes were drilled beneath these forts to abstract water from the Chalk thought to lie beneath. The Chalk proved to be at too great a depth, but the Bracklesham Group yielded a sustainable supply from <200 m. In carrying out these projects, military engineers sank wells and drilled speculative boreholes, taking financial risks, unacceptable in other parts of the public sector. They developed new technologies and their innovative ideas and discoveries led to an increased understanding of the distribution and use of groundwater.

Abstract Tsunami catalogues provide important datasets in assessing the risk from infrequent but potentially high-impact events. Although the UK is located away from subduction zones (the most common origin of tsunamis), tsunamis have struck its shores, most notably those triggered by the prehistoric Storegga submarine landslide and the 1755 Lisbon earthquake. Since the major events of 2004 (Indian Ocean) and 2011 (Japan) tsunamis are in the public psyche, even if the risks to UK coasts are not. Due to this heightened awareness, many reported events are claimed to be tsunamis and the potential for tsunamis is increasingly included in risk planning; understanding the true frequency of tsunamis is therefore important. Within the UK, the evidence for tsunamis includes tide gauge readings, reported visual observations and interpretation of sedimentological features. Catalogues need to consider whether the event is a true tsunami in order to avoid a plethora of claims that confound risk assessments; for example, recent well-documented events generated by weather systems (meteotsunamis) provide a possible explanation for some historical events. A detailed examination of the impact of tsunamis upon the UK coast is provided, including examples of events triggered by the three primary causes of tsunamis: seismicity, submarine landslides and coastal landslides.