British Geological Survey – Written Evidence (RSK0066)

British Geological Survey – Written evidence (RSK0066)

Professor John Rees, Chief Scientist (Multi-hazards and Resilience)1 on behalf of the British Geological Survey

SUMMARY

This submission is from the British Geological Survey (BGS), part of the UK Research and Innovation (UKRI) Natural Environment Research Council (NERC), the UK’s primary provider of data, information and impartial, independent advice on earth hazards. Earth hazard events associated with space weather (specifically geomagnetically induced currents), volcanic eruptions, earthquakes, tsunamis, landslides, subsidence, groundwater drought and groundwater flooding are outlined in response to Questions 1-3. The submission also addresses issues associated with developing resilience capability (Question 10) and lessons to be learned from other countries (Question 11).

Extreme risk varies across hazard types. Whilst most extremes, for planning purposes, are based on historically recorded events, evidence from pre-historical records may better inform worst-case scenarios. The relative importance of these may change over time, because of environmental drivers, such as climate change, as well as changes in exposure and vulnerability. The most significant extreme future risks may not be those of today, particularly when assessed cumulatively, and over longer timeframes.

All earth hazard risks are systemic in nature. They have direct impacts on infrastructure, people or other hazards. Whilst the direct impact of a hazard may be small, a secondary hazard may be extreme. For instance, the most extreme risks associated with earthquakes in the UK relate to possible impacts on infrastructure with a high consequence of failure such as power stations and dams. To substantially improve UK resilience to the risks posed by earth hazards it is important to not only understand, characterize and model the processes driving single hazards, but to better appreciate the interlinkages and interdependencies of multiple hazards, whether they cascade, or are unrelated, yet are synchronous. There is considerable potential for adaptation and tailoring of systemic risk analysis techniques developed in other sectors (e.g. supply chain risk in manufacturing, or contagion in financial risk), as well as disaster risk reduction internationally, to develop systemic UK natural hazard risk analysis.

Characterization of vulnerabilities of UK society, infrastructure and assets to earth hazards is highly immature. In modelling risks, multiple vulnerabilities, many of which are hazard specific, should be assessed. Such evaluation requires joint assessment by multiple actors from different sectors and disciplines.

Scenario analysis has great value, particularly where actors from many different disciplines come together to understand the multiple values of risk owners or to

1 With Vanessa Banks, Brian Baptie, John Bloomfield, Jon Chambers, Louise Clapperton, Ellen Clarke, Colm Jordan, Andres Payo Garcia, Susan Loughlin, and David MacDonald. coordinate action. Enhanced risk communication (including education) to support recognition of risk ownership, responsibility and practices that build resilience, requires greater national focus. The means by which communication, learning and uptake can be maintained - to facilitate responsive actions that are sensitive to changing risks - remains a big research challenge.

SUBMISSION OF EVIDENCE

1. The British Geological Survey (BGS), part of the UK Research and Innovation (UKRI) Natural Environment Research Council (NERC) is the UK’s primary provider of data, information and impartial, independent advice on earth hazards. It works with organisations across the public and private sectors to characterize and mitigate risks associated with these. A fuller description of the role of BGS in Natural Hazard Risk assessment and mitigation is set out in Annex 1. 2. In answer to the questions posed, this submission firstly outlines the UK risks posed by earth hazard events2 – addressing issues such as thresholds (including the nature of significant extreme risks), their systemic character, vulnerability and the evidence base (Questions 1, 2 and 3) on a hazard-by-hazard basis. This information will also have some bearing on other questions (Questions 4-9 and 12), though other organisations may be in a better position to provide fuller answers to these. Following this, the submission focuses on risk issues associated with developing resilience capability (Question 10) and lessons to be learned from other countries (Question 11).

UK EARTH HAZARD RISKS (Questions 1, 2 and 3).

3. The risks associated with natural hazards are a product of the combination of the impact on society and the likelihood of that impact. Extreme risks have both the potential to have a high probability of occurring during a human lifetime and a high societal cost. The relative importance of risks to the UK will change over time, because of both environmental drivers, such as climate change, as well as changes in exposure and vulnerability. The most significant extreme risks in the future may not be those of today, particularly when assessed cumulatively, and over longer timeframes. For instance, the increased losses associated with subsidence resulting from climate change may be cumulatively greater than a single ‘extreme’ event associated with another hazard. 4. All risks stemming from earth hazards are systemic in nature. Recognising the importance of characterizing systemic risk, BGS has built much of its strategy around the measurement and analysis of this (for instance in addressing the relationship between earthquakes and subsequent landslides) within its research programmes. 5. Space Weather - Geomagnetically Induced Currents (GIC) may be generated during a geomagnetic storm in conducting technologies connected to Earth, as a result of a solar coronal mass ejection a number of hours (>=15) earlier. The risks are essentially systemic as the currents

2 Short-term events, usually between hours and months; it excludes longer-term processes, such as erosion. directly impact upon societally-sensitive technologies and infrastructure. During storms, Earth currents are induced that can surge along oil and gas pipelines and high-tension electricity transmission lines, via transformer groundings. For pipelines this can upset the cathodic protection systems designed to protect the pipelines in the long-term from corrosion. For power networks it can damage transformers and interrupt protection systems, resulting in loss of power. GIC pose a significant threat to UK society given the high dependency of the economy on technologies that could be affected. This risk is increased by the northerly latitude (compared with many other countries) of the British Isles. 6. Our understanding of extreme space weather risks have largely been developed around a magnetic storm on 1st – 2nd September 1859, known as the Carrington storm, which is inferred by many to be the largest storm on record, although an exact assessment is not possible due to gaps in measurements made at the time. Nonetheless, it is currently estimated that a storm of this level could recur in the order of once every 100 years. The largest magnetic storm, within the digital recording era, occurred on 13-14 March 1989. This storm resulted in the loss of power in Quebec, Canada, affecting millions of citizens for a sizeable fraction of the storm duration. A storm of this level is expected to recur once every 30-50 years. At UK latitudes, there are approximately 1-2 severe magnetic storms per 11-year solar cycle, where power grid operators might need to be concerned and may need to take mitigating actions. 7. The UK is vulnerable to GICs because the population and economy depends on technologies that would be impacted by a major event. The primary risk associated with GIC is their impacts on the national grid. During a GIC event, direct current (DC) fluctuations are added to the alternating current (AC) in transformer cores. This can lead to transformer saturation, which in turn can lead to an increase in the reactive power absorbed by the transformer, potential voltage collapse, and the creation of substantial voltage harmonics into the power system. Harmonic distortion also leads to tripping of protective relays, which can then cause power outages. The size and impact of GIC in power systems are a complex combination of the processes driving the magnetic storm, the latitudinal proximity of the grid to the auroral electrojet (often overhead in the UK during severe magnetic storms), the underlying surface conductivity structures and the gird network configuration. Whilst science should help disentangle the complexity of the former three, only the latter can be physically changed or controlled. However, in order to reconfigure the network, power engineers require warnings much earlier than is currently possible from the science. 8. The Royal Academy of Engineering report (2013)3 on the impact of severe space weather on UK infrastructure is still widely regarded as authoritative. This will soon be updated under UKRI’s Strategic Priorities Fund space weather programme Space Weather Instrumentation, Measurement, Modelling and Risk (SWIMMR). Within the 2013 RAE report,

3 https://www.raeng.org.uk/publications/reports/space-weather-full-report a description is given of the likely impact of a ‘Carrington-level’ geomagnetic storm on the UK power transmission network. 9. The Government’s approach to GIC risk assessment could be strengthened through better forecasting of events. Forecasting of space weather, in comparison with terrestrial weather forecasting, is still in its infancy. Forecast models rely on basic measurements made in space by ESA and NASA spacecraft. Investment to sustain this fleet of ‘weather watchers’, for example through UK support for the proposed ESA ‘L5’ mission, will likely see long-term benefit to the UK and increased preparedness, for many space weather impacts. Looking forward, accurate prediction of space weather events with longer lead times is the ultimate goal of all Space Weather scientists. Significant and sustained R&D investment will continue to be needed to improve models and prediction algorithms and ensure they are integrated into real-time operational systems, for example within those of the Met Office Space Weather Operations Centre (MOSWOC). Investment is also essential to advance real-time data transfer capabilities, with the goal being measurement to tailored end-user product within seconds. For remote measurement locations such as magnetic observatories, this requires a modern high- speed broadband connection. 10. Volcanic eruptions begin when magma reaches the Earth’s surface. Some but not all eruptions are preceded by a period of ‘unrest’ as magma moves from depth towards the Earth’s surface. Volcanic unrest may comprise high levels of seismicity (earthquakes), ground deformation and other signs that can be detected using monitoring equipment (usually by a ‘volcano observatory’ or monitoring institution)4. Eruptions are highly dynamic, so eruption style and intensity may change significantly over time. For example, an eruption may include phases of slow effusion of lava and phases characterised by violent explosions. The duration of eruptions may vary from hours to decades. Volcanic eruptions are associated with a wide range of volcanic hazards, some of which may cause impacts 1000s kms from source5. 11. There are currently two scenarios in the National Risk Assessment (NRA) for Icelandic volcanoes: Eyjafjalljӧkull 2010 (disruptive ash-rich eruption, likelihood 1 in 5-10 years) and Laki 1783-4 (reasonable worst case, disruptive gas-rich eruption6, likelihood 1 in 250-500 years). These two Icelandic eruption scenarios were established by a SAGE sub-group in 2010. 12. The Volcanic Explosivity Index (VEI) is a logarithmic scale 1-8 that relates erupted volume of tephra (particles of fragmented magma) during explosive eruptions to the height of the explosive column of tephra above

4 Pallister, J. and 10 others. 2019. Volcano observatory best practices (VOBP) workshops – a summary of findings and best-practice recommendations, Journal of Applied Volcanology, 8:2 5Loughlin, S. C., Sparks, S., Brown, S., Jenkins, S. F., Vye-Brown, C. 2015. Global volcanic hazards and risk. Cambridge University Press. 6 Witham, C., Aspinall, W., Braban, C., Hall, J., Loughlin, S., Schmidt, A., Vieno, M., Bealey, B., Hort, M., Ilyinskaya, E., Kentisbeer, J., Roberts, E., Rowe,E., 2015, 'UK Hazards from a Large Icelandic Effusive Eruption', Effusive Eruption Modelling Project Final Report. a vent (Newhall and Self, 1983)7. The overall size of an eruption may also be described using magnitude (M), a function of the total erupted mass (M=log (erupted mass, kg)–7.0) over the duration of an eruption, designed to be similar to the VEI scale8. 13. The relatively small eruption of Eyjafjallajӧkull volcano in 2010 (VEI 4) was dominated by the prolonged impact of tropospheric volcanic ash clouds on air traffic in the North Atlantic and Europe, leading to economic losses of ~$5 billion globally9. Planning and preparedness in the UK has focused on the operational aviation response, improved observations of ash clouds, improved ash cloud dispersion models, near real-time forecasting (and assimilation of data), and understanding of vulnerabilities (e.g. jet engines). 14. The second scenario is based on the Laki fissure eruption from the Grimsvӧtn volcanic system in 1783-84, during which large volumes of lava (‘flood lava’), volcanic ash, gases and aerosols were erupted leading to a persistent veil of sulphuric aerosol over the northern hemisphere for more

than 5 months . The aerosols (H2SO4) were removed as acid precipitation, and caused extreme volcanic pollution (i.e., dry fog) that effected Europe and other regions in 1783, with documented impacts on health and crops10 . In Europe and North America, the annual mean surface cooling that followed the Laki eruption was about −1.3°C and lasted for 2–3 years11. 15. There are 32 active volcanic systems in Iceland12, one of which erupts approximately every 3-5 years. Moderate to large-sized eruptions of Iceland’s volcanoes may directly impact North Atlantic and UK airspace every 5-10 years, as demonstrated during eruptions in 2014-15 (Bar ð arbunga), 2011 (Grimsvӧtn), 2010 (Eyjafjallajӧkull) and earlier eruptions (Ilyinskaya13. 16. The UK has active volcanoes on three populated British Overseas Territories: Montserrat (last eruption 1995-2010, Wadge et al. 2014)14, Tristan da Cunha (last eruption 1961)15, and Ascension Island16. Even volcanic unrest and small eruptions would be disruptive on a small island. There are currently no risk assessments for eruptions in the British Overseas Territories in the NRA.

7 Newhall, C. G. and Self, S. 1982. The volcanic explosivity index (VEI) an estimate of explosive magnitude for historical volcanism. J. Geophys. Res., 87, 1231-1238 8 Pyle, D. M. (2000), Sizes of volcanic eruptions, in Encyclopedia of Volcanoes, edited by H. Sigurdsson, pp. 263– 269, Academic, San Diego, Calif. 9 Oxford Economics—the economics of air travel restrictions due to volcanic ash. Prepared for AirBus Industries. https://www.oxfordeconomics.com/my-oxford/projects/129051. Accessed 1 June 2015 10 Thordarson, T. and Self, S. 1993. The Laki (Skaftár Fires) and Grímsvötn eruptions in 1783–1785. Bull. Volcanol., 55, 233–263. 11 doi/full/10.1029/2001JD002042 12 http://icelandicvolcanos.is/ 13 Ilyinskaya, E. and Loughlin, S. 2015. Frequency of potentially disruptive gas-emitting eruptions in Iceland. British Geological Survey Internal Report IR/15/008 14 https://doi.org/10.1144/M39.1 15 https://doi.org/10.5194/nhess-14-1871-2014 16 https://doi.org/10.1130/G45415.1 17. There are 1500+ active volcanoes on land around the world, roughly 20 of which are erupting at any given time17. UK citizens, interests, airspace, air quality and climate may be affected by large magnitude eruptions anywhere in the world. There are currently no risk assessments for eruptions outside Iceland in the NRA. 18. There is a frequency-magnitude (f-M) relationship for eruptions up to M=718 with smaller magnitude eruptions being far more numerous than larger eruptions. Very large eruptions (M=8+) have a different f-M relationship indicating that these ‘super-eruptions’ are controlled by different processes but they are extreme events (e.g. two per million years19. 19. A risk of concern associated with volcanic ash, volcanic gases and

aerosols (e.g. SO2 and H2SO4), is the disruption of air traffic for several days or longer, leading to cancelled and/or diverted flights. Volcanic ash clouds typically contain gases and aerosols, but sometimes volcanic gas and aerosol clouds may exist separately and contain no ash. 20. The primary vulnerabilities to high concentrations of volcanic ash particles in the atmosphere are related to jet engines where glassy particles can erode turbine compressor blades, clog air filters, block fuel nozzles, disrupt temperature sensors, contaminate oil systems and melt to form coatings on vital engine components. Ash particles may abrade forward-facing surfaces on any plane including windscreen, fuselage surfaces and landing lights, and static discharge may affect radio transmission. Ash clouds may also limit the visibility from the cockpit.

Sulphur dioxide gas (SO2) reacts with water vapour in the atmosphere to

form sulphuric acid (H2SO4) which is corrosive and can damage exposed parts of a plane, sulphate may be deposited in engines. Sulphur dioxide gas, sulphate aerosol and fine ash particles may also penetrate the cabin of an aircraft, affecting visibility, causing odours and potentially causing a health hazard. 21. At ground level, aerosols in particular may impact human health20,21 , 22. Those with pre-existing respiratory conditions may be particularly

17 https://volcano.si.edu/; 18 Deligne, N. I., Coles, S. G. & Sparks, R. S. J. Recurrence rates of large explosive volcanic eruptions. J. Geophys. Res. 115, B06203 (2010) 19 Mason, B. G., Pyle, D. M. & Oppenheimer, C. The size and frequency of the largest explosive eruptions on Earth. Bull. Volcanol. 66, 735–748 (2004). 20 World Health Organisation 2013. Review of evidence on health aspects of air pollution – REVIHAAP project: final technical report. Online http://www.euro.who.int/__data/assets/pdf_file/0004/193108/REVIHAAP- Finaltechnical-report-final-version.pdf.

21 Horwell, C.J., Baxter, P.J. & Kamanyire, R. (2015). Health Impacts of Volcanic Eruptions. In Global Volcanic Hazards and Risk. Loughlin, S.C., Vye-Brown, C., Sparks, R.S.J., Brown S.K. & Jenkins, S.F. Cambridge University Press. 22 Horwell, C., Baxter, P., Hillman, S., Calkins, J., Damby, D., Delmelle, P., Donaldson, K., Dunster, C., Fubini, B. & Kelly, F. 2013. Physicochemical and toxicological profiling of ash from the 2010 and 2011 eruptions of Eyjafjallajökull and Grímsvötn volcanoes, Iceland using a rapid respiratory hazard assessment protocol. Environmental Research, 127, 63-73. vulnerable and pre-existing socio-economic vulnerabilities should be considered. The combined impacts of volcanic and anthropogenic air pollution on health are poorly understood. 22. The UK overseas territories of Tristan da Cunha and Ascension Island are vulnerable should there be volcanic unrest or eruptions onshore or offshore. There is no volcano monitoring to detect signs of unrest, and no early warning systems or formal contingency planning for volcanic eruptions. Volcano monitoring, preparedness and planning would all improve the situation. BGS is engaged in risk reduction activities with island authorities. 23. Vulnerabilities due to a large magnitude eruption anywhere in the world that could affect climate and cause global cooling over several years are poorly understood because there has only been one such event in modern times (Pinatubo, 1991, M=6). However, such events are not so infrequent (Krakatau 1883 M=6; Tambora 1815, M=7). Long-term disruption to travel and humanitarian consequences across broad geographic areas should also be considered. 24. Vulnerabilities due to the disruption of supply chains, trade and travel during a large magnitude eruption in Europe (e.g. Italy, Greece, Canary Islands) or North America also exist. 25. Earthquakes are the result of sudden movement along faults within the Earth's Crust that releases stored up stress and cause the ground surface to shake. Intense ground shaking from earthquakes causes damage to buildings and infrastructure and potentially results in fatalities due to falling masonry or collapse of structures. The area of greatest damage is likely to be restricted to a few tens of kilometres from the epicentre. Earthquakes may cause significant disruption to infrastructure, transport and communications, even if the physical damage is comparatively minor. 26.The UK is characterised by low levels of earthquake activity and low seismic hazard. Historical observations of earthquake activity date back to the 14th century and show that despite many accounts of earthquakes widely felt by people, damaging earthquakes are relatively rare. However, though infrequent, damaging earthquakes do occur and are relatively well documented over the last few hundred years. The largest known British earthquake occurred near the Dogger Bank in 1931, with a magnitude of 5.9 Mw. Although it was 60 miles offshore it was still powerful enough to cause minor damage to buildings on the east coast of England. There have been sixteen earthquakes with magnitudes of 5.0 Mw or greater since 1650. The number of earthquakes in a given time is widely observed to decrease exponentially as magnitude increases. This means that large earthquakes are much less frequent than small ones. Data for the UK suggest that an earthquake with a magnitude of 5 Mw or above occurs approximately every 50 years and a magnitude of 6.0 Mw or above occurs roughly every 500 years. Historical accounts of damaging earthquakes suggest that a moderately damaging earthquake occurs approximately every 25 years and a heavily damaging earthquake every 150 years. 27.Earthquake risk has been considered as part of the National Risk Assessment exercise and are included in the National Risk Register. This process is informed by national seismic hazard maps compiled by the BGS. The 2020 version of the national seismic hazard maps incorporates the latest advances in seismic hazard analysis and will be used in the National Annexes for the latest revision to the Eurocode 8 building code: Earthquake resistant design of structures, which is expected to be published in 2025. The 2020 maps represent the hazard in terms of both peak ground acceleration, which tells us about the acceleration of the ground, and spectral acceleration, which gives an approximation of the possible motion of buildings of different heights. 28.Damage to surface structures due to earthquake shaking is the result of inertial forces, causing the centre of gravity of the building to move relative to its base or foundation. Most buildings in the UK are not constructed with this in mind. Impact will depend upon the age and build- quality and older buildings, e.g., Victorian terrace housing, will be more susceptible to damage. Unreinforced masonry walls and chimneys may be susceptible to collapse, and gable walls may be damaged. Historic buildings such as churches and monuments are also likely to be vulnerable. Falling ceilings and furniture may add to the damage and disruption. Ground shaking may also lead to power outages due to failure of sensitive apparatus along with disruption to transport and communications networks. Safety inspections of high-consequence structures and installations including nuclear power plants, dams and reservoirs, bridges and tunnels are likely to be required. 29.The most extreme risks associated with earthquakes in the UK relate to possible impacts on infrastructure with a high consequence of failure such as power stations and dams. This is already recognised in regulatory regimes; the licensing process for Nuclear Power Plants (NPPs) in the UK requires the licensee to demonstrate adequate protection of the public and the environment from a radiation leak caused by seismic events. Continuous long-term observation and recording of earthquakes by BGS forms the basis for robust assessments of seismic hazard in the UK that helps inform decisions on planning and regulation, particularly for infrastructure with a high consequence of failure such as power stations and dams. BGS has pioneered developments in stochastic modelling (Monte Carlo simulation) for probabilistic seismic hazard assessments to account for the epistemic uncertainties in both the driving forces for earthquake activity and their ground motions. Scientists at BGS are leading global research efforts to improve understanding of earthquake forecasting and triggering. BGS has also contributed to scientific understanding of the hazards from induced earthquakes resulting from shale gas exploration and production that has helped inform regulatory decisions on hydraulic fracturing operations. 30.The Government’s approach to earthquake risk assessment could be improved by quantification of likely damage resulting from UK earthquakes. While there have been significant efforts to understand and map earthquake hazard in the UK and surrounding areas, there have been very few assessments of risk that quantify the probability of loss or damage in terms of number of casualties, monetary loss, or repair costs. Such studies could improve understanding of vulnerability and risk, particularly in urban areas. There are also significant uncertainties associated with the lack of observations of large earthquakes, maximum possible magnitudes, the locations and magnitudes of historical earthquakes, as well as our understanding of the tectonics of the UK region and the location and character of the fault structures on which observed seismicity occurs. Future hazard assessments should address these issues. 31.Tsunamis are a series of gravity waves generated primarily by vertical seabed movement; mainly from earthquakes, but also by downslope seabed sediment movement, which is termed a submarine landslide23. Coastal flooding of the UK from tsunamis is rare, but prehistoric events in the Shetlands up to 20-30 metres in elevation, and historical events in southeast England of several metres, one of which may have caused fatalities, have occurred. 32.Understanding of UK hazard and risk of coastal flooding from tsunamis was last considered in 2005/2006 in response to the 2004 Indian Ocean tsunami24. Tsunami flooding was mainly considered in the context of: a near field earthquake in North Sea (cf. Dogger Bank, 1931); a passive margin earthquake in the western Celtic Sea; a tsunami generated by the Storegga submarine landslide offshore Norway; a plate boundary earthquake west of Gibraltar (e.g. Lisbon earthquake of 1755), and volcanic landslides on the Canary Islands. Of these events a Storegga type tsunami was considered to have the potential to cause the most damage to northern UK, although the last event took place at 8,150 BP with a return period estimated at over 100,000 years. Overall, these reports concluded that the flood risk to the UK from tsunamis was small. Responding to the Japan tsunami, during which the Fukushima nuclear power plant was flooded leading to a reactor meltdown, a further review of UK tsunami hazard, in the context of nuclear power plants25 recommended that a new assessment of UK tsunami risk is required to address advances in understanding of tsunami hazard and risk. This view is supported by a preliminary BGS reassessment of the UK tsunami hazard, which shows the UK risk could be underestimated. 33.Given the very low likelihood of a tsunamigenic event affecting the UK within a human lifetime, the associated tsunami risk is also minor; hence it cannot be considered extreme. The risk is not insignificant, however, and a tsunami could have very high impact. The lack of new UK research

23 International Tsunami Information Centre (2019). Definition of Tsunami. Available at http://itic.ioc-unesco.org. 24 Kerridge, D., 2005. The threat posed by tsunami to the UK. Study commissioned by Defra Flood Management and produced by British Geological Survey, Proudman Oceanographic Laboratory, Met Office and HR Wallingford., p. 167.

25 ONR, 2011. The Japanese earthquake and tsunami: Implications for the UK nuclear industry, HM Chief Inspector of Nuclear Installations September 2011 based on recent advances in understanding from global events outside of the UK has resulted in a limited knowledge base on which to develop protocols for emergency planning and response. More research is needed to assess possible tsunami mechanisms, their magnitude and coastal impact, together with the development of reasonable worst-case risk scenarios for inclusion in the UK National Risk Register. 34.Landslides constitute the mass movement of material, such as rock, earth or debris, down a slope when the force of gravity acting on a slope exceeds the resisting forces of the slope. They can occur suddenly. Triggering is commonly associated with meteorological events (e.g. extreme rainfall26, seismic events and other erosional processes such as flooding, riverbank/ coastal cliff erosion or human activity. The primary risk concerns from landslides are associated with the potential for loss of life (there have been a number of deaths associated with landslides in the UK) and socio-economic costs associated with damage to infrastructure. 35.Risk assessment relies on understanding when and where landslides may interact with people and infrastructure. This is addressed through infrastructure mapping, hazard characterisation (understanding of likely size and runout of a landslide), and identification of areas that are susceptible to landslides, based on ground conditions (including geology, geomorphology, topography). Risk assessment can be particularly challenging for deeper-seated landslides where stability is linked to groundwater conditions, or coastal cliffs where marine processes commonly control events. A sound understanding of processes and monitoring can be used to develop early warning systems; currently the status of these is, however, immature. In relation to coastal landslides, the need for quantitative assessments at a large spatial scale (103 km) and over time horizons of the order 101 to 102 years for coasts have been reinforced by the 2019 Special Report on the Ocean and Cryosphere in a Changing Climate. This concluded that adaptation to a sea-level rise will be needed no matter what emission scenario is followed. BGS maintains the National Landslide Database and is well-placed to focus on this. 36.Subsidence, a lowering or collapse of the ground, results from physical property changes - through compression, clay shrink-swell, piping (grain- by-grain removal of sub-surface, weakly cemented granular sediments), dissolution or collapse, karstic ground dissolution of soluble rocks, or anthropogenic activities, such as mining. Subsidence is commonly triggered by meteorological changes in moisture content affecting physical properties, groundwater changes, ground loading and vibration, changing land-use, mining and tunnelling. It can be gradual, due to slow changes in material properties, or sudden due to collapse, for instance through sudden loss of strength to strata bridging a cave or loss of artificial roof support over a cavity such as a mine. Karstic subsidence is commonly triggered during periods of prolonged weather.

26 Pennington, C., Dijkstra, T., Lark, ., Dashwood., Harrison, A. and Freeborough, K. 2014. Antecedent precipitation as a potential proxy for landslide incidence in South West UK. Proceedings of World Landslide Forum 3, 2-6 June 2014, Beijing. 11 pp. 37.Solitary subsidence events cannot be considered as extreme. However, the impacts of cumulative events are already very large and may increase with climate change. The response of expansive clays to moisture content change means that they are susceptible to climate change impacts and land-use change (e.g. planting or removal of trees); it is estimated that 70 per cent of UK domestic subsidence claims are a result of clay shrinkage (Alex Croydon, Verisk, 2021). Infrastructure is vulnerable to subsidence where this exceeds the tolerance of the structure and results in fracture and damage. It is particularly susceptible to differential settlement in compressible soils as a consequence of differential loading or variation in soil thickness. When associated with piping, collapse or dissolution, it is likely to be a response to the development of non-uniform hydrological conditions. 38. The Government’s approach to landslide risk assessment should be improved through enhanced conceptual understanding of the volume change processes, ground characterisation, understanding of climate and climate change with proportionate engineering design. Engineers rely on soil parameters that can be measured as analogues for actual volume change. Improved risk assessment could be realised through site-specific monitoring of volumetric change and its impact on infrastructure – including a better understanding of subsidence insurance claims in the context of the age and design of building stock, as well as land-use to determine whether existing guidance is fit for purpose. Laboratory and numerical modelling will be required to determine the likely impact of climate change in the context of existing guidance for engineering design. 39.Groundwater drought is a period of below normal groundwater resources associated with a deficit in precipitation (meteorological drought). It is characterised by sustained low groundwater levels, reduced base flow from groundwater to rivers, reduced groundwater flows to springs and groundwater-fed wetlands and reduced yields from boreholes27 . Groundwater droughts can be characterised using Standardised Groundwater level Index SGI28 in terms of their duration, magnitude and intensity. Note that groundwater drought can be considered as distinct from groundwater scarcity (where access to groundwater, for whatever reason, leads to restricted supplies) and from groundwater over- exploitation resulting from a long-term over-abstraction of groundwater. However, groundwater drought typically exacerbates problems associated with groundwater scarcity and groundwater over-exploitation. 40.Due to natural variability in rainfall, the UK episodically experiences droughts, including groundwater droughts. The spatial and temporal extent of droughts varies: small droughts typically effect only small regions of the UK over a relatively short periods, perhaps only one season, whereas major droughts can affect most of the UK and large parts 27 Van Loon, 2015; Marchant, 2018). 28 The Standardised Groundwater level index is an estimate of a standardised deviation of groundwater levels from a long-term monthly mean and enables groundwater drought status to be compared between multiple boreholes and with other standardised drought indices, such as meteorological (Standardised Precipitation index, SPI) and stream flow drought indices https://doi.org/10.5194/hessd-10-7537-2013 of adjoining continental Europe and last multiple years29. The spatio- temporal variation of recent major groundwater droughts have been mapped30 across the UK’s main aquifer, the Chalk. Groundwater droughts, reconstructed for the UK between the 1890s to the 1970s31, show that there were also five major groundwater droughts. The 1975-1976 drought is commonly used as a reference worst-case ‘extreme’ drought from the historic, observational record for planning purposes; it had widespread and deep impacts on the UKs water supplies, including groundwater resources32. 41.No consistent signals in changes in groundwater drought associated with groundwater use have been reported for the UK. Wendt et al., (2020)33 have reported changes in groundwater droughts as a function of the ratio of abstraction to long-term groundwater recharge. However, they also noted the need for more work to better understand the effects of the use of groundwater on future droughts. 42.Monthly groundwater resource status is reported in the BGS/UKCEH’s Monthly Hydrological Summary, for England as part of the Environment Agency’s (EA) water situation reporting, as part of CEH’s water resources portal, and over a one month to one year period by the Hydrological Outlooks service34. As a condition of their license to abstract groundwater, the EA requires water supply companies in England to maintain drought management plans that include an assessment of the risk of droughts to water supply. Details of the risk assessments vary between water companies, depending on the extent and nature of groundwater abstracted. Other UK environmental regulators have drought management plans appropriate to the nation’s needs. 43. Currently, there is very little information, either nationally or internationally, on the vulnerabilities of groundwater drought. For example, in the European Drought Impact Inventory (EDII) there is no specific category for groundwater drought impact data35. However, the impacts of groundwater droughts are diverse and potentially significant, including: reduced yields from water supply boreholes36 resulting in less water available for agriculture (primarily for irrigation) and for industry; reduced flows in or drying up of groundwater dependent wetlands, high baseflow streams, and reduced groundwater flows of wetlands.

29 https://doi.org/10.5194/piahs-383-297-2020 30 Events in 1975–1976; 1988–1992; 1995–1997; 2004–2006; and 2010–2012 https://doi.org/10.1016/j.jhydrol.2018.07.009 31 Droughts in 1900-1910, the ‘long-drought’; 1920-1921; 1943-1946; and 1972- 1974https://doi.org/10.5285/d92c91ec-2f96-4ab2-8549-37d520dbd5fc https://doi.org/10.5285/ccfded8f- c8dc-4a24-8338-5af94dbfcc16 32 Durant, M. 2015 Description of groundwater droughts in the UK: 1890 to 2015. Nottingham, UK, British Geological Survey, 52pp. (OR/15/007).

33 https://doi.org/run/hess-24-4853-2020 34 UKCEH, 2020a,b; EA, 2020; Hydrological Outlook, 2020. 35 https://www.geo.uio.no/edc/droughtdb/ 36 https://doi.org/10.1016/j.jhydrol.2019.123998 44.As already noted, groundwater drought compounds issues of water scarcity. In the UK, the regions of greatest water stress are the south, south-east and east of England. These regions are the warmest and the driest in the UK, are susceptible to the effects of climate change, and in many areas have very high population densities and current relatively high per capita water demand. They also happen to coincide with the Chalk aquifer, the main aquifer in the UK, and the part of the UK with some of the highest proportion of groundwater in public supply. Consequently, it is these areas that are most vulnerable to groundwater drought. In addition, although they constitute only a small fraction of potable water supplies in the UK, private water supplies on minor, local aquifers, for example in parts of rural Wales and the north east of Scotland, are also vulnerable to groundwater droughts. 45.The Government’s approach to groundwater drought risk assessment could be improved by improved monitoring, analysis, modelling and forecasting. Systematic groundwater level measurements are undertaken by the national environment agencies, such as the EA. There is a continued pressure on the monitoring agencies to rationalise their networks. It is essential that the current monitoring network is maintained, but ideally reviewed and extended in areas of the UK most vulnerable to groundwater drought and to underrepresented areas, such as small / minor aquifers. The groundwater level data will increasingly become available through web data streams (APIs). This process needs to be accelerated. BGS and our partners need to continue to develop and refine our web services that report on the current and modelled (forecast) future groundwater resources and drought status ensuring that they meet growing and evolving stakeholder and community needs. Note that BGS with other partners are currently developing a proposal for capital funding for NERC, to be submitted to UKRI in summer 2021, to develop the UK’s first Flood and Drought Research Infrastructure. If successful, this will for the first time develop a network of fixed and mobile observation infrastructure specifically designed to enable the quantification and investigation of hydrological extremes (including groundwater drought) at the national scale. 46.Improved groundwater drought risk assessments could also be facilitated by research into groundwater storage, baseflow to rivers, and groundwater drought impacts. As noted previously, research into storage, baseflow and groundwater drought impacts have been identified as key to improving our ability to strengthen groundwater drought risk assessments. In particular, it has been noted that there is very limited quantitative evidence on the relationship between groundwater drought and the societal impacts of groundwater drought. A scheme needs to be developed to capture the impacts of future groundwater droughts. This is a critical step in the development of comprehensive future groundwater drought risk assessments for the UK. 47.Groundwater flooding is the emergence of groundwater at the ground surface away from perennial river channels, or the rising of groundwater into man-made ground, under conditions where the 'normal' ranges of groundwater level and groundwater flow are exceeded37. The impact of groundwater flooding can occur before water levels reach the ground surface where there is inundation of building basements and buried services, such as sewers, or other assets below ground level. Groundwater levels that rise above ground have the potential to reach low-lying areas protected from fluvial flooding. Large flows from intermittent or dormant springs, also come under the definition of groundwater flooding. These can cause flooding down gradient where surface water drainage channels are inadequate. The characteristic feature of groundwater flooding events is the relatively long duration compared with fluvial flooding. 48.Groundwater flooding, unrelated to climatic drivers, can occur in large urbanised areas where land was developed during periods of suppressed water tables resulting from substantial groundwater pumping for industrial and public supply. As industry moved away from the urban centres, as well as reduced use of groundwater due to urban pollution, groundwater levels rebounded and now can cause the inundation of subsurface infrastructure and low-lying areas38. 49.As groundwater flooding is long-lasting – and therefore of high impact - and is likely to occur within human lifetimes it could be regarded as an extreme event – but only in particular catchments and geology. Long- lasting, often regionally extensive, groundwater flooding can be caused by the water table in unconfined aquifers rising above the land surface as a response to extreme rainfall. Areas on the Chalk outcrop of southern England are particularly vulnerable (Finch et al., 2004)39. In the Chalk, groundwater levels can rise several tens of metres during periods of intense rainfall. However, due to the limited surface river network in these catchments, it can take months for groundwater levels to return to normal ranges. Groundwater flooding caused significant damage to properties in areas of Chalk outcrop in recent years, in particular in the winters of 2000/01 and 2013/1440,41. 50.Groundwater flooding is also associated with shallow unconsolidated sedimentary aquifers which overlie impermeable rocks (Macdonald et al., 2012)42. These aquifers are susceptible to flooding as the storage capacity is often limited, groundwater levels are normally shallow, direct rainfall recharge can be high and the sediments may be very permeable, creating a good hydraulic connection with adjacent river networks. Natural levees

37 Macdonald, D. M. J., Bloomfield, J. P., Hughes, A. G., MacDonald, A. M., Adams, B., & McKenzie, A. A. (2008). Improving the understanding of the risk from groundwater flooding in the UK. 38 For instance, London, Birmingham, Nottingham and Liverpool; Bricker et al., 2017. 39 Finch, J. W., Bradford, R. B., & Hudson, J. A. (2004). The spatial distribution of groundwater flooding in a chalk catchment in southern England. Hydrological Processes, 18(5), 959-971 40 Hughes, A. G., Vounaki, T., Peach, D. W., Ireson, A. M., Jackson, C. R., Butler, A. P., ... & Wheater, H. S. (2011). Flood risk from groundwater: examples from a Chalk catchment in southern England. Journal of Flood Risk Management, 4(3), 143-155 41 Ascott, M. J., Marchant, B. P., Macdonald, D., McKenzie, A. A., & Bloomfield, J. P. (2017). Improved understanding of spatio-temporal controls on regional scale groundwater flooding using hydrograph analysis and impulse response functions. Hydrological processes, 31(25), 4586-4599. 42 Macdonald, D., Dixon, A., Newell, A., & Hallaways, A. (2012). Groundwater flooding within an urbanised flood plain. Journal of Flood Risk Management, 5(1), 68-80. and man-made structures can allow river levels to rise without breaking their banks; groundwater flooding will occur in low-lying areas beyond the banks, preceding any fluvial flooding and lengthening the overall period of flooding. These hydrogeological settings often coincide with large urban areas. 51.The Government’s approach to groundwater flooding risk assessment could be improved by improving the evidence base to support this. UK legislation includes a requirement to assess the risk associated with groundwater flooding43. Datasets for assessing risk are basic due to the challenges created by complex geology and subsurface infrastructure, a limited monitoring network, and a lack of observations of groundwater flood impact against which to validate models. Licensable groundwater flood risk maps are produced by a number of environmental consultancies, and environmental regulators in the UK have maps of groundwater flood likelihood that are used to identify areas of significant risk. Historically, most attention has been given to groundwater flooding on chalk, where up to 138 000 properties in England lie in areas at risk of groundwater flooding44. It is harder to estimate the risk of flooding from groundwater on other aquifers, but up to 152 000 further properties could be affected. While this is significantly fewer than the number that are at risk from other sources of flooding, groundwater flooding is still locally significant in many areas. In localities known to have a history of groundwater flooding in England, the Environment Agency has developed a groundwater flood alert network linked to levels in specific trigger boreholes (all on the Chalk outcrop).

CHALLENGES IN DEVELOPING RESILIENCE CAPABILITY (Question 10)

52.Research gaps and status: The earth hazard synopses set out above outline the importance of probabilistic assessment and forecasting of the temporal and spatial distribution of future hazardous events to UK communities, assets and infrastructure. They also highlight the importance of monitoring changes of hazards and their drivers, particularly as several of these are affected by climate change or resource degradation. The synopses show how BGS has a key role to play in monitoring and assessment. 53.To substantially improve UK resilience to the risks posed by these hazards it is important to not only understand, characterize and model the processes driving single hazards, but to better appreciate the interlinkages and interdependencies of multiple hazards, whether they cascade, or are unrelated, yet are synchronous. To date most risk assessments do not take the interactions of multiple hazards into account, or do so at a very basic level. The BGS strategy highlights the ambition for BGS to drive multi-hazard risk science.

43 Cobby, D., Morris, S., Parkes, A., & Robinson, V. (2009). Groundwater flood risk management: advances towards meeting the requirements of the EU floods directive. Journal of Flood Risk Management, 2(2), 111- 119 44 McKenzie, A. A., & Ward, R. S. (2015). Estimating numbers of properties susceptible to groundwater flooding in England. Nottingham, UK, British Geological Survey, 8pp. (OR/15/016) 54.In appreciating and modelling risks, it is important that the multiple vulnerabilities – many of which are hazard specific - of exposed populations and their assets, are also assessed. Such evaluation requires joint assessment by multiple actors from different sectors and disciplines. Whilst research funders have already recognised the importance of enhanced integration of the science community to address systemic risk in the international arena (reflected by the creation of the UKRI Global Challenges Research Fund, for instance), more is required at a national level. To improve national resilience to natural hazards, systemic risk information (including on multiple scenarios or options – see below) should be made accessible to decision makers over multiple timescales. They should be able to obtain data, information and models to support planning and long-term investment, as well as near real-time management of natural hazard events. There is considerable potential for adaptation and tailoring of systemic risk analysis techniques developed in other sectors (e.g. supply chain risk in manufacturing, or contagion in financial risk) to be applied to natural hazards. 55.National frameworks not only require better characterization of complex risks, but also should support mechanisms to inform appropriate action. The importance of enhanced risk communication (including education) to support recognition of risk ownership, responsibility and practices that build resilience is now acknowledged internationally and requires greater national focus. The means by which communication, learning and uptake can be maintained to facilitate responsive actions that are sensitive to changing risks remains a big research challenge. 56. The role of exercising to test risk preparedness and their utility in the UK: BGS identifies the enormous value of scenario analysis - for instance in understanding risks, vulnerabilities of systems, clarifying responsibilities, testing protocols, testing of protocols, training or coordination of emergency response – is widely recognised. Exercises have been successfully used in relation to planning of possible events in relation to many earth hazards, for instance space weather (led by SEIEG) or multi-hazards (such as for the Welsh Resilience Forum, or local authorities in Dorset). They have enormous utility, particularly where actors from many different disciplines come together to understand the multiple values of risk owners or to coordinate action. Several, developed around tools such as Bayesian Belief networks, have radically changed emergency response plans. Several exercises have shown the value of repeat exercises to explore the sensitivity of management systems and to improve the efficiency of coordination.

LESSONS FROM OTHER COUNTRIES (Question 11)

57.Practices, processes or considerations that could improve the UK’s national risk resilience: The importance of developing and maturing systemic risk analysis has been widely recognised internationally (e.g. by instruments such as the 2015 Sendai Framework, which addresses disaster risk reduction). As a consequence, several major initiatives to support the establishment of good practice and protocols have been developed, including the Global Risk Assessment Framework (GRAF)45 by the UN Office for Disaster Risk Reduction, and the Risk Data Library46 by the Global Facility for Disaster Risk Reduction (GFDRR) of the World Bank, and the hazard classification of the UN Office for Disaster Risk Reduction and the International Science Council47. BGS staff have been core to the development of all of these initiatives. UK engagement in such international initiatives provides a window to explore the utility of approaches to manage systemic risks by recognition of successful schemes in other countries48.

ANNEX 1

1. The British Geological Survey in UK Natural Hazard Risk Management: BGS is the primary UK organisation that monitors and assesses earth hazards that pose risks nationally and internationally. BGS works with Government Departments, agencies (such as the Environment Agency), businesses, charities and the wider UK public, to provide them with data, information, products and services they require. 2. It operates the UK Magnetic observatories, the UK Seismic network, the Global Volcano Model, and monitoring of shallow geohazards and groundwater (including provision of services including the Monthly Hydrological Summaries, Hydrological Outlooks, and UK Water Resources Portal). 3. BGS works with national and international partners to maintain standards, provide data and assessments of hazard status, and provision of advice - including through: the European Space Agency, UK Met Office, INTERMAGNET, the ESA-supported ‘Space Safety’ Geomagnetic Expert Service Centre, the Space Weather Impact Expert Group, UNOSAT, and the Natural Hazard Partnership. 4. BGS provides leads research on UK natural hazards and associated risks. The BGS Strategy ‘Gateway to the Earth’49 sets out three priority risk related topics, and BGS has implemented applied research teams addressing: Multi-hazard Systems (including single hazards, multi- hazards, exposure and vulnerability); Multi-hazard Risk Reduction (including forecasting, hazard and risk communication, resilience and

45 https://www.preventionweb.net/disaster-risk/graf 46 https://understandrisk.org/efficient-risk-data-sharing-a-dedicated-disaster-risk-data-library/ 47 https://www.undrr.org/publication/hazard-definition-and-classification- review#:~:text=The%20UNDRR%2FISC%20Sendai%20Hazard,mechanisms%20and%20renewed%20global%20p artnerships%E2%80%9D. 48 For instance, that developed for North Vancouver by the Canadian Geological Survey. https://wwwstage.dnv.org/sites/default/files/edocs/earthquake-risk-summary.pdf 49 https://www.bgs.ac.uk/download/bgs-science-strategy-2019-2023-gateway-to-the-earth/ recovery, and event response) and Multi-hazard Data Science and Uncertainty.

28 January 2021