- Email: [email protected]
Geohazard information to meet the needs of the British public and government policy
ARTICLE IN PRESS
Quaternary International 171–172 (2007) 179–185
Geohazard information to meet the needs of the British public and government policy Jennifer Catherine Walsby British Geological Survey, Kingsley Dunham Centre, Information Directorate, NickerHill Keyworth Nottinghamshire, NG12 5GG, UK Available online 3 March 2007
Abstract Environmental information is increasingly valued and understood by government, commercial business and the general public. At the same time, the Environmental Information Regulations enable access to a huge amount of information, which may not be in a userfriendly format. Since 2000, the British Geological Survey has been developing nationwide geo-environmental datasets that identify the potential for subsidence and geochemical hazards. This information is provided as GIS datasets or in easy-to-use report format to meet the different needs of local and central government, commercial data providers and individuals. The information is geared to answer questions posed by the UK Planning Guidance, the EU Water Framework Directive and the UK Home Information Pack. New developments aim to provide information on groundwater flooding, soil erosion potential and mining hazards to meet growing concerns about the impact of climate change and in response to incoming mine waste regulations. The provision of digital geohazard information has enabled BGS to inform the British public and policy makers of potential hazards, and helped them to understand the relevance of environmental information to their lives. r 2007 Elsevier Ltd and INQUA. All rights reserved.
1. Introduction It has long been a goal of the British Geological Survey (BGS) to provide geoscience information in a format that can be easily understood and used by non-geoscientists. This has been reinforced in recent years by a greater public interest in environmental conditions and polices that enable wider access to government information. In addition, the demand for geological data by local government offices has increased due to planning policy guidelines in relation to unstable land and flooding. Many applied analogue geological maps and reports have been produced over the years (Smith and Ellison, 1999), but since the mid1990s the challenge has been to provide digital data. The development of a digital mapping system in 1989 and the subsequent production of a nationwide digital geological map database at 1:50 000 scale (DiGMapGB-50) in 2001 provided the basis from which digital applied geology could be generated. DiGMapGB-50 is a full GIS data set: polygons, lines and points are all attributed with their geological definitions (Jackson and Green, 2003). Tel.: +44 1158363271; fax: +44 1159363150.
E-mail address: [email protected].
Between 2000 and 2005, BGS invested approximately £2 million in devising new methodologies and generating digital data that identifies areas where there is a potential for natural geological hazards (geohazards), in terms of ground movement, geochemistry and groundwater activity. Bedrock geology and superficial deposits, including anthropogenic deposits, were reclassified in terms of geohazard potential and, where data existed, validated with recorded hazard occurrences. The new methods combined geological knowledge with topographic data and other information and each polygon is attributed with its potential to be a geohazard. These geohazard datasets are corporately maintained, improved and delivered. Information about potential geological hazards is now being actively used to assist decision-making in locating and designing commercial and private buildings and utilities, building control, in land remediation, for house purchases and for setting insurance premiums.
2. Natural geohazards and planning in Great Britain Unlike some of its European neighbours, Britain rarely suffers from catastrophic geological hazards, such as
1040-6182/$ - see front matter r 2007 Elsevier Ltd and INQUA. All rights reserved. doi:10.1016/j.quaint.2007.02.015
ARTICLE IN PRESS J.C. Walsby / Quaternary International 171–172 (2007) 179–185
180
damaging earthquakes. However, those that do occur can be costly in terms of structural damage, insurance payments and blight. Local and central government, commercial organisations and individuals are eager, therefore, to have as much information as possible to reduce costs and risk. In response to the effects of geohazards in the built environment, a number of government planning guidelines were implemented in the 1990s to highlight to local government planners the importance of geology. The guidelines inform developers and the general public about the form and location of potential geohazards. BGS has for some time provided information and expertise on geohazards for individual and large-scale enquiries. However, national, high-resolution digital data for specific physical and chemical geohazards have been generated only recently. In the 1990s, radon legislation led to the provision of radon hazard map data that identifies where protective measures may be needed in new dwellings. Geology was recognised as the most important overall control on the concentration of radon in dwellings (Appleton et al., 2000; Appleton and Miles, 2005). Geological radon potential digital map data at 1:250 000 scale were generated for England and Wales and in limited areas at 1:50 000 scale. These were then converted into 5 km grid square maps that indicate where a geological assessment (Fig. 1) may need to be carried out to determine whether radon protective measures are required in new dwellings (BRE, 1999). The subsequent creation of the high-resolution DiGMapGB-50 has enabled the development of digital radon potential
mapping at 1:50 000 scale for all England and Wales, leading to the recent production of a more detailed radon potential data set in collaboration with the Health Protection Agency—Radiation Protection Division. Similarly, planning policy guidance on unstable land was aimed at identifing areas prone to subsidence such that the impacts could be minimised through remedial or preventative measures (PPG14: 1990, 1996, 2002). This guidance refers to mining and other industrial activites as well as subsidence due to natural cavities, landslides and other geological phenomena. Of main concern are the risks and costs to human safety, construction and building stability. Planners are advised to take potential natural ground instability into consideration and provide local plans identifying constraints on development. BGS has for a long time provided information on potential ground instability to local planners for many parts of Britain, but until 2002 there was no consistent country-wide digital data set at an appropriate scale. Reattribution of the 1:50 000 scale digital geology in terms of ground instability has been a major breakthrough in BGS’s ability to rapidly provide medium-scale digital data and ground stability reports for any part of England, Wales and Scotland. 2.1. Physical geohazards data The geohazard datasets generated include:
NT NX
NU
NZ
NY
SD
SE
TA
SH
SJ
SK
TF
TG
SM
SN
SO
SP
TL
TM
SR
SS
ST
SU
TQ
TR
SW
SX
SY
SZ
TV
Swell-shrink clays, clay-rich soils and rocks that absorb water and can shrink or swell with changes in moisture content. Landslides, the outward or downward movement of rock or soil on a slope. Soluble rocks that occur in gypsum, salt, limestone and chalk. The minerals dissolve creating underground cavities that can collapse. Running sand, the flow of sand into a hole under the influence of water pressure. Compressible ground, fluid is squeezed out when the material is loaded and can cause rapid compression. Collapsible deposits, these are wind blown silts and sands (loess) found in southern England that can suddenly collapse when wetted under load. Groundwater flooding, where water levels below the ground rise, flooding normally dry land and causing flow in streams that are usually dry.
2.2. Chemical geohazards data The geochemical hazard data generated include:
Fig. 1. Areas in England and Wales where a geological assessment may need to be carried out to determine whether radon protective measures are required in new dwellings (Revised and recoloured version of Map 2, Annex B, BR211, BRE, 1999). Basic radon protection may be required if the development site is in a pale shaded square; full or basic radon protection may be required if site is in a dark shaded square). Topographyr Crown copyright. All rights reserved.
Radon, a naturally occurring radioactive gas that can cause lung cancer; it is produced by the radioactive decay of radium and uranium. Methane and carbon dioxide, gases that are asphyxiants and the former is explosive; both are potentially
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BGS has concentrated on naturally occurring geohazards but human influence on ground stability and contamination is considered where information is available, for example, in relation to land use and pollution, notably associated with mining, farming, building, waste disposal and industrialisation. 3. Method of geohazard classification BGS geoscientists have extensive knowledge of the different ground conditions in Britain through surveying and research. However, historical mapping specifications and varied applied geology requirements meant that in the past geohazards have not been consistently or routinely recorded countrywide. Data on occurrences of hazards, such as landslides and solution features have been well recorded in areas with recognised problems and geochemical samples have been taken across Scotland, Wales and two-thirds of England. Given the variability in coverage, it was decided to develop new and comprehensive methodologies to classify the mapped geological units in terms of the potential for specific geohazards to occur. This classification would draw on the knowledge and expertise of the geoscientists who surveyed and sampled the land and watercourses. Recorded occurrences of hazard features were then used to validate the classified map data. A team of geoscientists and Information System experts devised a deterministic methodology that could be run in a GIS environment to produce digital geohazard polygons for England, Scotland and Wales. The deterministic approach looks at the presence of factors that bring about a hazard at the site being assessed. Causative factors are identified; the three key factors used are geology, topography and water; each factor is given a rating according to their relative importance in causing each hazard. These rating values are then combined for each geological polygon and run against a series of rules to create a hazard susceptibility ‘score’ for the polygons. The more factors that are present and the greater their magnitude, the greater the level of potential hazard, where A is the lowest and E is the highest (Fig. 2). For example, when considering the potential for running sands, a site is assessed through combining the most important factors: lithology and groundwater conditions. Running conditions can only occur in superficial deposits of loose, non-cohesive material of sand or silt grade, in bedrock where sands have not been cemented or locked, or in sandstones that have had their intergranular cement removed by weathering or alteration. Running conditions
E
Level of Hazard
hazardous to life. Particularly associated with formations containing coal and peat geology. Natural oil seeps, at the surface and underground generally but of low hazard in GB. Potentially harmful elements, including arsenic, nickel, lead, chromium and cadmium, may be a risk to human health where concentrations are high.
181
D
C
B
A Increasing number or severity of causative factors Fig. 2. The relationship between causative factors and the level of potential geohazard.
can occur naturally below the water table, or if water drains through the ground from the surface or, for example, from a broken water pipe (Fig. 3). Influencing factors vary with the geohazard. For landslides, the slope of the ground is one of the major controlling factors. For this methodology, slope was derived directly from a digital terrain model of Britain, generated from an airborne survey. The high resolution of this dataset enabled local variations in height and individual morphological features, including many existing landslide features, to be identified. For landslides, in particular, the availability of databases of occurrences has enabled a high level of validation and proved the methodology. There is good agreement between the GIS model and distribution of recorded landslides and more recent events such as the 2004 landslide near Lochearnhead (Wildman and Forster, 2005; Winter et al., 2005). The digital data predicted a highly susceptible area (Fig. 4) and in August 2004 the deposits in this area mobilised following heavy rain and formed two debris flows that blocked the A85 and trapped 54 people in their vehicles. All were subsequently rescued. As concerns grow over climate change and the implications for ground instability, the causative factors approach to hazard mapping will enable us to incorporate additional factors, or change the emphasis of the importance of certain factors (Forster and Culshaw, 2004). 4. Output of geohazard information 4.1. The requirement UK government policies and EU directives (e.g. Directive 2000/6o/EC) increasingly take into account environmental considerations and subsequent planning guidelines take steps to reduce risks to health and costs of repair. UK planning guidance, in particular, refers to the consideration of ground stability, flooding and geochemistry through its Planning Policy Guidance (PPG) 14: Development on
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Running Sand Flow Chart Superficial
Artificial
Cohesive
BedRock
Non-Cohesive
Gravel
Cemented
Not Cemented
Sand
Fig. 3. Schematic of the algorithm for Running Sands potential.
stream and ground waters (Appleton, 1995). These examples emphasise the importance of not only highlighting potential natural hazards to members of the British public, but also how their actions can activate or mitigate geohazards (Fig. 5). 4.2. Output formats
Fig. 4. Landslide hazard model of the area around Lochearnhead, Scotland. Areas shown in cross-hatch are class D: Slope instability problems are probably present or have occurred in the past. (Wildman and Forster, 2005).
Unstable Land, PPG20: Coastal Planning, PPG23: Planning and Pollution Control, PPG25: Development and Flood Risk, and Part 2A of the Environmental Protection Act covering contaminated land and radioactivity. UK policies, combined with the Statutory Environmental Assessments, and national regulations transposed from EU Directives, prompted BGS to review the type of geohazard information provided. New data users include the general public, insurers, builders, government advisors, planners, engineers and health workers. Personal health and safety, the stability of constructions and the cost of build, maintenance or repair are increasingly high priority considerations for all these groups. BGS determined that, for those without the appropriate geoscience or ground engineering training, the information needed not only to be user-friendly but also user-specific. Thus, we developed several styles of advice for each hazard type and user. It is notable that even for those areas with the greatest potential for ground movement, it is human interaction with the ground that is often the trigger for subsidence and thus the greatest cause for concern. Similarly, contamination from potentially harmful elements is of concern when there is local disturbance, for example, from mine workings or tunnels that could lead to widespread dispersal into
Technological advancements and the rapidly reducing costs of high performance computing now enable BGS to process national datasets more comprehensively than ever before. However, in the early 2000s this was a barrier and limits on processing functionality led to the data being cut into manageable portions. Initially, vector polygons datasets were used, but these were found to be unmanageable and the data were converted to grids for the multicriterion analysis (Wildman and Forster, 2005). Fuzzy errors, which are increased as processing continues, were reduced by using grids. The grids are output as polygon files and, although less attractive, the pixellated appearance has the advantage of emphasising the resolution of the data. Developing methodologies and creating digital datasets are time-consuming and are the technically difficult parts of building information products. However, customer interaction and market research are also vital to ensure the provision of geoscience output that is of value to the user. BGS has worked with existing and potential customers to identify the way in which this information is needed. Users vary from those with limited access to digital systems and a strong preference for paper products, to those desiring web-enabled delivery of information or using highly complex GIS and 3D modelling systems. Therefore, we offer the data in several forms: (1) in the ESRI ArcGIS gridded format in which it is created, for all GB or cut to user-specified areas, (2) merged with postcode polygons using a weighted average for use in address searches, (3) as online web responses to location queries and (4) in paper (or PDF) reports that collate the data and output maps and information for each geohazard (http://shop.bgs.ac.uk/ georeports/). Some users, such as commercial valued-added resellers (VAR) incorporate the national GIS datasets into their own reporting service and provide paper reports to their customers. A VAR is a company that adds some feature to
ARTICLE IN PRESS J.C. Walsby / Quaternary International 171–172 (2007) 179–185 Hazard rating
Implications for Planners
A
No indicators for slope instability identified.
No constraints to land use due No maintenance or use to slope instability within site. implications due to slope instability.
B
Slope instability problems are unlikely to be present.
No constraints to land use due No maintenance or use to slope instability within site. implications due to slope instability.
C
Slope instability problems may be present or anticipated.
Reporton implications for stability should be submitted if changes to drainage, construction or excavation are proposed.
Some consideration of implications for stability should bemade if changes to drainage, construction or excavation areplanned.
D
Slope instability problems are probably present or have occurred in the past.
Land use changes involving, loading, excavation or changes to drainage will affect stability and mitigation measures should accompany application.
Do not dispose of surface drainage to the ground. Do not undercutor load slopes.
E
Slope instability problems almost certainly present.
Permission for development may require remedial works as part of development. Permission for development may not be possible.
Consider obtaining specialist advice to advise on need for stabilisation work and/orland management plan tomaintain stability.
183
Advice to Householders
Fig. 5. Advice to planners and householders in regard to landslide potential, supplied as attributes of the landslide GIS data.
an existing product and then sells it, usually to end users, as a new package. Others use the datasets in their own decision support systems, such as local government GI systems used to respond to planning applications. Growing use of GIS by local authorities has given BGS the opportunity to emphasise the potential for land instability assessments and ground contamination in aiding local planning. Increasingly, customers want products oriented to their particular working practices; for example, BGS has set up a web service that provides ground stability information for a company for specific house locations, which they use to check whether land is suitable for building a conservatory extension. BGS has also created joint products in partnership with other leading environmental organisations and as mentioned above we are working with the Health Protection Agency—Radiation Protection Division to develop a radon potential product (Miles and Appleton, 2005). This will ensure protective measures are included in new and existing properties in radon prone areas, and inform householders and their legal advisors when a radon enquiry is made in England and Wales as part of property searches (Con29 (2002): Standard Enquiries of Local Authority). Similarly, BGS is in partnership with the Coal Authority to develop a joint ground stability service that incorporates both natural geohazards and ground movement due to coal mining. 4.3. Data issues and intellectual property rights In Britain, while public sector organisations (such as the BGS) receive a significant portion of their funds from
government, they are also encouraged to recover costs from users of their services. Thus, it is important that datasets and scientific expertise used to generate products for sale or license are protected under copyright laws. Cost recovery can be a frustration for scientists who, historically, are used to freely sharing their data widely, especially with academics in the same field. However, the incentive to recover costs to maintain the organisations financial stability has resulted in increased focus on client needs and delivery of more useable and valued products. A professional approach to data and its IPR has also provided an unambiguous basis for partnerships and future initiatives with many organisations. 5. The future 5.1. Updates and maintenance The unglamorous, but highly important task of maintaining the geohazard datasets will continue to be a significant cost to the BGS. But the work will ensure both long-term digital storage and updates to the datasets as new information is gathered through research projects and geological mapping. These updates are vital to ensuring that both individuals and local planning authorities have the most up-to-date information to aid decision making, including any changes to hazard ratings. The suite of geohazard datasets will also be updated through the addition of new data as new requirements emerge. Groundwater flooding is the first of these. The availability of DiGMapGB-50 has provided the means for a new groundwater hazard data set to be built. Robins
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et al. (2003) highlight the importance of such information for identifying areas of potential pollution, foundation stability, recharge, tunnel, and other flooding. Hydrogeological conditions also impact on other geological hazards: slope instability, dissolution of karst, clay swelling, and subsidence of loess. Currently government guidelines with regard to flooding, as implemented and monitored by the Environment Agency and the Scottish Environmental Protection Agency, concentrate on river flooding. Although less destructive, groundwater flooding can have a long-term negative impact and is influenced by any change in the climate and therefore needs to be included in the planning process. It is not only different datasets that will be required in the near future, but also data at different resolutions. In greatest demand are geohazard data at the largest scale possible in urban areas. BGS is currently developing methodologies to enable the provision of the six ground stability hazards at 1:10 000 scale in urban areas, where more modern geological mapping is in place. Digital data will be increasingly supplied through the World Wide Web, making it easier to provide up-to-date information and make it directly accessible to customers. Currently, some data are being supplied in 3D format to meet the demands of expert users. Increasingly, geologists, utilities companies and some land developers are using digital 3D models to better understand the subsurface and provision of 3D information would meet many future needs (see in the recommendations of Rosenbaum and Culshaw, 2003), that building a 3D model of ground conditions in advance of site investigation would allow better planning and reduce uncertainty with regard to ground instability. 5.2. Government policies One particular government policy is likely to have a significant impact on the demand for geohazard information in Great Britain. This is known as the Home Information Pack (2006)—essentially a report that the seller must provide to a buyer on the condition of their home—which will be introduced in 2007. At the time of writing, geohazards other than radon are listed as ‘authorised’ rather than ‘required’ information. This is expected to result in an increase in the demand for geohazard information from the current 600 000 reports per year. It is possible that all geohazard information may become ‘Required’ (i.e. mandatory); this could mean that as many as 1.4 million reports a year would need to be delivered. Efficient digital (web-based) delivery systems will be needed to cope with such demand. 6. Conclusions There is a proven need for geological hazard information to be readily available as easy to understand digital and paper products. The development of such products has
revealed a number of issues in relation to product-build costs, long-term maintenance and, in particular, the understanding of user need and the relevance of geology to everyday activities, and of the complexity of geological terminology. Government departments and environmental specialists have long acknowledged the importance and application of geohazard information. However, it is the more recent recognition of their value by commercial organisations, such as VARs, in answering house-buyers’ and developers’ questions with regard to ground stability and gas emissions, which has accelerated the demand for geohazard data. This has precipitated a change from complex scientific geological text into more easily understood language, which has, in turn, enabled greater and wider understanding of geohazard potential. Following the creation of high-resolution digital geology (DiGMapGB-50) a suite of national digital geohazard datasets has been developed and provided to a variety of users. These datasets are being maintained and updated to ensure users continue to have the most up-to-date and best quality information the BGS can provide. The methodologies will be reviewed and updated as data coverage improves and databases of occurrences expand enabling better quality control and validation of the potential hazards. In addition, new datasets will be added to meet the growing demand for information about a wider range of geological hazards and the existing hazard data will be provided at the larger 1:10 000 scale for urban and priority development areas. Acknowledgement This paper is published with the permission of the Executive Director of the British Geological Survey (NERC). References Appleton, J. D., 1995. Radon, methane, carbon dioxide, oil seeps and potentially harmful elements from natural sources and mining areas: characteristics, extent and relevance to planning and development in Great Britain: summary report: British Geological Survey, Analytical Geochemistry Series. Technical Report WP/95/4. Appleton, J.D., Miles, J.C.H., 2005. Radon in Wales. In: Bassett, M.G., Deisler, V.K., Nichol, D. (Eds.), Urban Geology in Wales: 2. Cardiff, National Museum of Wales Geological Series No. 24, pp. 117–129. Appleton, J.D., Miles, J.C.H., Scivyer, C.R., Smith, P.H., 2000. Dealing with radon emissions in respect of new developments. Summary report and recommended framework for planning guidance. British Geological Survey Research Report, RR/00/7, 26pp. Building Research Establishment (BRE), 1999. Radon: Guidance on Protective Measures for New Dwellings, 1999 ed. BR211, CRC Ltd., London, UK. Directive 2000/60/EC of the European Parliament and of the Council of 23 October 2000 establishing a framework for Community action in the field of water policy (WFD). Official Journal L 327, 22/12/2000, pp. 0001–0073. Forster, A., Culshaw, M.G., 2004. Implications of climate change for hazardous ground conditions in the UK. Geology Today 20 (2), 61–67.
ARTICLE IN PRESS J.C. Walsby / Quaternary International 171–172 (2007) 179–185 Jackson, I., Green, C., 2003. DigMapGB—the digital geological map of Great Britain. Geoscientist 13 (2), 4–7. Miles, J.C.H., Appleton, J.D., 2005. Mapping variation in radon potential both between and within geological units. Journal of Radiological Protection 25, 257–276. Planning Policy Guidance Note 14: Development on Unstable Land, 1990. Department of the Environment, UK. Planning Policy Guidance Note 14: Development on Unstable Land. Annex 1: Landslides and Planning, 1996. Department of the Environment, UK. Planning Policy Guidance Note 14: Development on Unstable Land. Annex 2: Subsidence and Planning, 2002. Department of Transport Local Government and the Regions, UK. Planning Policy Guidance Note 25: Development and Flood Risk, 2001. Department of Transport Local Government and the Regions, UK. Robins, N.S., Forster, A., Lewis, M.A., Butcher, A.S., 2003. Shallow and perched groundwater hazards and hazard mapping in the UK. In: Rodriguez, R., Civita, M., de Maio, M. (Eds.), Aquifer Vulnerability
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and Risk: Proceedings of the First International Workshop. Salamanca, Mexico, No. 2, pp. 251–259. Rosenbaum, M.S., Culshaw, M.G., 2003. Communicating the risks arising from geohazards. Journal of the Royal Statistical Society Series A: Statistics in Society 166 (2), 261–270. Smith, A., Ellison, R.A., 1999. Applied geological maps for planning and development: a review of examples from England and Wales, 1983–96. Quarterly Journal of Engineering Geology 32, S1–S44. The Home Information Pack Regulations (HIP), 2006. Office of the Deputy Prime Minister. Draft for Publication, 31 October 2005. Statutory Instruments, Housing, England and Wales /http:// www.odpm.gov.uk/index.asp?id=1161272S. Wildman, G., Forster, A., 2005. Using GIS to create a Landslide Hazard Assessment Map for Great Britain. In: Proceedings of the Annual Conference of the AGI. Association for Geographical Information, London. Winter, M.G., Macgregor, F., Shackman, L. (Eds.), 2005. Scottish Road Network Landslide Study. Scottish Executive /http://www.scotland. gov.uk/Publications/2005/07/08131738/17395S.
Quaternary International 171–172 (2007) 179–185
Geohazard information to meet the needs of the British public and government policy Jennifer Catherine Walsby British Geological Survey, Kingsley Dunham Centre, Information Directorate, NickerHill Keyworth Nottinghamshire, NG12 5GG, UK Available online 3 March 2007
Abstract Environmental information is increasingly valued and understood by government, commercial business and the general public. At the same time, the Environmental Information Regulations enable access to a huge amount of information, which may not be in a userfriendly format. Since 2000, the British Geological Survey has been developing nationwide geo-environmental datasets that identify the potential for subsidence and geochemical hazards. This information is provided as GIS datasets or in easy-to-use report format to meet the different needs of local and central government, commercial data providers and individuals. The information is geared to answer questions posed by the UK Planning Guidance, the EU Water Framework Directive and the UK Home Information Pack. New developments aim to provide information on groundwater flooding, soil erosion potential and mining hazards to meet growing concerns about the impact of climate change and in response to incoming mine waste regulations. The provision of digital geohazard information has enabled BGS to inform the British public and policy makers of potential hazards, and helped them to understand the relevance of environmental information to their lives. r 2007 Elsevier Ltd and INQUA. All rights reserved.
1. Introduction It has long been a goal of the British Geological Survey (BGS) to provide geoscience information in a format that can be easily understood and used by non-geoscientists. This has been reinforced in recent years by a greater public interest in environmental conditions and polices that enable wider access to government information. In addition, the demand for geological data by local government offices has increased due to planning policy guidelines in relation to unstable land and flooding. Many applied analogue geological maps and reports have been produced over the years (Smith and Ellison, 1999), but since the mid1990s the challenge has been to provide digital data. The development of a digital mapping system in 1989 and the subsequent production of a nationwide digital geological map database at 1:50 000 scale (DiGMapGB-50) in 2001 provided the basis from which digital applied geology could be generated. DiGMapGB-50 is a full GIS data set: polygons, lines and points are all attributed with their geological definitions (Jackson and Green, 2003). Tel.: +44 1158363271; fax: +44 1159363150.
E-mail address: [email protected].
Between 2000 and 2005, BGS invested approximately £2 million in devising new methodologies and generating digital data that identifies areas where there is a potential for natural geological hazards (geohazards), in terms of ground movement, geochemistry and groundwater activity. Bedrock geology and superficial deposits, including anthropogenic deposits, were reclassified in terms of geohazard potential and, where data existed, validated with recorded hazard occurrences. The new methods combined geological knowledge with topographic data and other information and each polygon is attributed with its potential to be a geohazard. These geohazard datasets are corporately maintained, improved and delivered. Information about potential geological hazards is now being actively used to assist decision-making in locating and designing commercial and private buildings and utilities, building control, in land remediation, for house purchases and for setting insurance premiums.
2. Natural geohazards and planning in Great Britain Unlike some of its European neighbours, Britain rarely suffers from catastrophic geological hazards, such as
1040-6182/$ - see front matter r 2007 Elsevier Ltd and INQUA. All rights reserved. doi:10.1016/j.quaint.2007.02.015
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180
damaging earthquakes. However, those that do occur can be costly in terms of structural damage, insurance payments and blight. Local and central government, commercial organisations and individuals are eager, therefore, to have as much information as possible to reduce costs and risk. In response to the effects of geohazards in the built environment, a number of government planning guidelines were implemented in the 1990s to highlight to local government planners the importance of geology. The guidelines inform developers and the general public about the form and location of potential geohazards. BGS has for some time provided information and expertise on geohazards for individual and large-scale enquiries. However, national, high-resolution digital data for specific physical and chemical geohazards have been generated only recently. In the 1990s, radon legislation led to the provision of radon hazard map data that identifies where protective measures may be needed in new dwellings. Geology was recognised as the most important overall control on the concentration of radon in dwellings (Appleton et al., 2000; Appleton and Miles, 2005). Geological radon potential digital map data at 1:250 000 scale were generated for England and Wales and in limited areas at 1:50 000 scale. These were then converted into 5 km grid square maps that indicate where a geological assessment (Fig. 1) may need to be carried out to determine whether radon protective measures are required in new dwellings (BRE, 1999). The subsequent creation of the high-resolution DiGMapGB-50 has enabled the development of digital radon potential
mapping at 1:50 000 scale for all England and Wales, leading to the recent production of a more detailed radon potential data set in collaboration with the Health Protection Agency—Radiation Protection Division. Similarly, planning policy guidance on unstable land was aimed at identifing areas prone to subsidence such that the impacts could be minimised through remedial or preventative measures (PPG14: 1990, 1996, 2002). This guidance refers to mining and other industrial activites as well as subsidence due to natural cavities, landslides and other geological phenomena. Of main concern are the risks and costs to human safety, construction and building stability. Planners are advised to take potential natural ground instability into consideration and provide local plans identifying constraints on development. BGS has for a long time provided information on potential ground instability to local planners for many parts of Britain, but until 2002 there was no consistent country-wide digital data set at an appropriate scale. Reattribution of the 1:50 000 scale digital geology in terms of ground instability has been a major breakthrough in BGS’s ability to rapidly provide medium-scale digital data and ground stability reports for any part of England, Wales and Scotland. 2.1. Physical geohazards data The geohazard datasets generated include:
NT NX
NU
NZ
NY
SD
SE
TA
SH
SJ
SK
TF
TG
SM
SN
SO
SP
TL
TM
SR
SS
ST
SU
TQ
TR
SW
SX
SY
SZ
TV
Swell-shrink clays, clay-rich soils and rocks that absorb water and can shrink or swell with changes in moisture content. Landslides, the outward or downward movement of rock or soil on a slope. Soluble rocks that occur in gypsum, salt, limestone and chalk. The minerals dissolve creating underground cavities that can collapse. Running sand, the flow of sand into a hole under the influence of water pressure. Compressible ground, fluid is squeezed out when the material is loaded and can cause rapid compression. Collapsible deposits, these are wind blown silts and sands (loess) found in southern England that can suddenly collapse when wetted under load. Groundwater flooding, where water levels below the ground rise, flooding normally dry land and causing flow in streams that are usually dry.
2.2. Chemical geohazards data The geochemical hazard data generated include:
Fig. 1. Areas in England and Wales where a geological assessment may need to be carried out to determine whether radon protective measures are required in new dwellings (Revised and recoloured version of Map 2, Annex B, BR211, BRE, 1999). Basic radon protection may be required if the development site is in a pale shaded square; full or basic radon protection may be required if site is in a dark shaded square). Topographyr Crown copyright. All rights reserved.
Radon, a naturally occurring radioactive gas that can cause lung cancer; it is produced by the radioactive decay of radium and uranium. Methane and carbon dioxide, gases that are asphyxiants and the former is explosive; both are potentially
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BGS has concentrated on naturally occurring geohazards but human influence on ground stability and contamination is considered where information is available, for example, in relation to land use and pollution, notably associated with mining, farming, building, waste disposal and industrialisation. 3. Method of geohazard classification BGS geoscientists have extensive knowledge of the different ground conditions in Britain through surveying and research. However, historical mapping specifications and varied applied geology requirements meant that in the past geohazards have not been consistently or routinely recorded countrywide. Data on occurrences of hazards, such as landslides and solution features have been well recorded in areas with recognised problems and geochemical samples have been taken across Scotland, Wales and two-thirds of England. Given the variability in coverage, it was decided to develop new and comprehensive methodologies to classify the mapped geological units in terms of the potential for specific geohazards to occur. This classification would draw on the knowledge and expertise of the geoscientists who surveyed and sampled the land and watercourses. Recorded occurrences of hazard features were then used to validate the classified map data. A team of geoscientists and Information System experts devised a deterministic methodology that could be run in a GIS environment to produce digital geohazard polygons for England, Scotland and Wales. The deterministic approach looks at the presence of factors that bring about a hazard at the site being assessed. Causative factors are identified; the three key factors used are geology, topography and water; each factor is given a rating according to their relative importance in causing each hazard. These rating values are then combined for each geological polygon and run against a series of rules to create a hazard susceptibility ‘score’ for the polygons. The more factors that are present and the greater their magnitude, the greater the level of potential hazard, where A is the lowest and E is the highest (Fig. 2). For example, when considering the potential for running sands, a site is assessed through combining the most important factors: lithology and groundwater conditions. Running conditions can only occur in superficial deposits of loose, non-cohesive material of sand or silt grade, in bedrock where sands have not been cemented or locked, or in sandstones that have had their intergranular cement removed by weathering or alteration. Running conditions
E
Level of Hazard
hazardous to life. Particularly associated with formations containing coal and peat geology. Natural oil seeps, at the surface and underground generally but of low hazard in GB. Potentially harmful elements, including arsenic, nickel, lead, chromium and cadmium, may be a risk to human health where concentrations are high.
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D
C
B
A Increasing number or severity of causative factors Fig. 2. The relationship between causative factors and the level of potential geohazard.
can occur naturally below the water table, or if water drains through the ground from the surface or, for example, from a broken water pipe (Fig. 3). Influencing factors vary with the geohazard. For landslides, the slope of the ground is one of the major controlling factors. For this methodology, slope was derived directly from a digital terrain model of Britain, generated from an airborne survey. The high resolution of this dataset enabled local variations in height and individual morphological features, including many existing landslide features, to be identified. For landslides, in particular, the availability of databases of occurrences has enabled a high level of validation and proved the methodology. There is good agreement between the GIS model and distribution of recorded landslides and more recent events such as the 2004 landslide near Lochearnhead (Wildman and Forster, 2005; Winter et al., 2005). The digital data predicted a highly susceptible area (Fig. 4) and in August 2004 the deposits in this area mobilised following heavy rain and formed two debris flows that blocked the A85 and trapped 54 people in their vehicles. All were subsequently rescued. As concerns grow over climate change and the implications for ground instability, the causative factors approach to hazard mapping will enable us to incorporate additional factors, or change the emphasis of the importance of certain factors (Forster and Culshaw, 2004). 4. Output of geohazard information 4.1. The requirement UK government policies and EU directives (e.g. Directive 2000/6o/EC) increasingly take into account environmental considerations and subsequent planning guidelines take steps to reduce risks to health and costs of repair. UK planning guidance, in particular, refers to the consideration of ground stability, flooding and geochemistry through its Planning Policy Guidance (PPG) 14: Development on
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Running Sand Flow Chart Superficial
Artificial
Cohesive
BedRock
Non-Cohesive
Gravel
Cemented
Not Cemented
Sand
Fig. 3. Schematic of the algorithm for Running Sands potential.
stream and ground waters (Appleton, 1995). These examples emphasise the importance of not only highlighting potential natural hazards to members of the British public, but also how their actions can activate or mitigate geohazards (Fig. 5). 4.2. Output formats
Fig. 4. Landslide hazard model of the area around Lochearnhead, Scotland. Areas shown in cross-hatch are class D: Slope instability problems are probably present or have occurred in the past. (Wildman and Forster, 2005).
Unstable Land, PPG20: Coastal Planning, PPG23: Planning and Pollution Control, PPG25: Development and Flood Risk, and Part 2A of the Environmental Protection Act covering contaminated land and radioactivity. UK policies, combined with the Statutory Environmental Assessments, and national regulations transposed from EU Directives, prompted BGS to review the type of geohazard information provided. New data users include the general public, insurers, builders, government advisors, planners, engineers and health workers. Personal health and safety, the stability of constructions and the cost of build, maintenance or repair are increasingly high priority considerations for all these groups. BGS determined that, for those without the appropriate geoscience or ground engineering training, the information needed not only to be user-friendly but also user-specific. Thus, we developed several styles of advice for each hazard type and user. It is notable that even for those areas with the greatest potential for ground movement, it is human interaction with the ground that is often the trigger for subsidence and thus the greatest cause for concern. Similarly, contamination from potentially harmful elements is of concern when there is local disturbance, for example, from mine workings or tunnels that could lead to widespread dispersal into
Technological advancements and the rapidly reducing costs of high performance computing now enable BGS to process national datasets more comprehensively than ever before. However, in the early 2000s this was a barrier and limits on processing functionality led to the data being cut into manageable portions. Initially, vector polygons datasets were used, but these were found to be unmanageable and the data were converted to grids for the multicriterion analysis (Wildman and Forster, 2005). Fuzzy errors, which are increased as processing continues, were reduced by using grids. The grids are output as polygon files and, although less attractive, the pixellated appearance has the advantage of emphasising the resolution of the data. Developing methodologies and creating digital datasets are time-consuming and are the technically difficult parts of building information products. However, customer interaction and market research are also vital to ensure the provision of geoscience output that is of value to the user. BGS has worked with existing and potential customers to identify the way in which this information is needed. Users vary from those with limited access to digital systems and a strong preference for paper products, to those desiring web-enabled delivery of information or using highly complex GIS and 3D modelling systems. Therefore, we offer the data in several forms: (1) in the ESRI ArcGIS gridded format in which it is created, for all GB or cut to user-specified areas, (2) merged with postcode polygons using a weighted average for use in address searches, (3) as online web responses to location queries and (4) in paper (or PDF) reports that collate the data and output maps and information for each geohazard (http://shop.bgs.ac.uk/ georeports/). Some users, such as commercial valued-added resellers (VAR) incorporate the national GIS datasets into their own reporting service and provide paper reports to their customers. A VAR is a company that adds some feature to
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Implications for Planners
A
No indicators for slope instability identified.
No constraints to land use due No maintenance or use to slope instability within site. implications due to slope instability.
B
Slope instability problems are unlikely to be present.
No constraints to land use due No maintenance or use to slope instability within site. implications due to slope instability.
C
Slope instability problems may be present or anticipated.
Reporton implications for stability should be submitted if changes to drainage, construction or excavation are proposed.
Some consideration of implications for stability should bemade if changes to drainage, construction or excavation areplanned.
D
Slope instability problems are probably present or have occurred in the past.
Land use changes involving, loading, excavation or changes to drainage will affect stability and mitigation measures should accompany application.
Do not dispose of surface drainage to the ground. Do not undercutor load slopes.
E
Slope instability problems almost certainly present.
Permission for development may require remedial works as part of development. Permission for development may not be possible.
Consider obtaining specialist advice to advise on need for stabilisation work and/orland management plan tomaintain stability.
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Advice to Householders
Fig. 5. Advice to planners and householders in regard to landslide potential, supplied as attributes of the landslide GIS data.
an existing product and then sells it, usually to end users, as a new package. Others use the datasets in their own decision support systems, such as local government GI systems used to respond to planning applications. Growing use of GIS by local authorities has given BGS the opportunity to emphasise the potential for land instability assessments and ground contamination in aiding local planning. Increasingly, customers want products oriented to their particular working practices; for example, BGS has set up a web service that provides ground stability information for a company for specific house locations, which they use to check whether land is suitable for building a conservatory extension. BGS has also created joint products in partnership with other leading environmental organisations and as mentioned above we are working with the Health Protection Agency—Radiation Protection Division to develop a radon potential product (Miles and Appleton, 2005). This will ensure protective measures are included in new and existing properties in radon prone areas, and inform householders and their legal advisors when a radon enquiry is made in England and Wales as part of property searches (Con29 (2002): Standard Enquiries of Local Authority). Similarly, BGS is in partnership with the Coal Authority to develop a joint ground stability service that incorporates both natural geohazards and ground movement due to coal mining. 4.3. Data issues and intellectual property rights In Britain, while public sector organisations (such as the BGS) receive a significant portion of their funds from
government, they are also encouraged to recover costs from users of their services. Thus, it is important that datasets and scientific expertise used to generate products for sale or license are protected under copyright laws. Cost recovery can be a frustration for scientists who, historically, are used to freely sharing their data widely, especially with academics in the same field. However, the incentive to recover costs to maintain the organisations financial stability has resulted in increased focus on client needs and delivery of more useable and valued products. A professional approach to data and its IPR has also provided an unambiguous basis for partnerships and future initiatives with many organisations. 5. The future 5.1. Updates and maintenance The unglamorous, but highly important task of maintaining the geohazard datasets will continue to be a significant cost to the BGS. But the work will ensure both long-term digital storage and updates to the datasets as new information is gathered through research projects and geological mapping. These updates are vital to ensuring that both individuals and local planning authorities have the most up-to-date information to aid decision making, including any changes to hazard ratings. The suite of geohazard datasets will also be updated through the addition of new data as new requirements emerge. Groundwater flooding is the first of these. The availability of DiGMapGB-50 has provided the means for a new groundwater hazard data set to be built. Robins
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et al. (2003) highlight the importance of such information for identifying areas of potential pollution, foundation stability, recharge, tunnel, and other flooding. Hydrogeological conditions also impact on other geological hazards: slope instability, dissolution of karst, clay swelling, and subsidence of loess. Currently government guidelines with regard to flooding, as implemented and monitored by the Environment Agency and the Scottish Environmental Protection Agency, concentrate on river flooding. Although less destructive, groundwater flooding can have a long-term negative impact and is influenced by any change in the climate and therefore needs to be included in the planning process. It is not only different datasets that will be required in the near future, but also data at different resolutions. In greatest demand are geohazard data at the largest scale possible in urban areas. BGS is currently developing methodologies to enable the provision of the six ground stability hazards at 1:10 000 scale in urban areas, where more modern geological mapping is in place. Digital data will be increasingly supplied through the World Wide Web, making it easier to provide up-to-date information and make it directly accessible to customers. Currently, some data are being supplied in 3D format to meet the demands of expert users. Increasingly, geologists, utilities companies and some land developers are using digital 3D models to better understand the subsurface and provision of 3D information would meet many future needs (see in the recommendations of Rosenbaum and Culshaw, 2003), that building a 3D model of ground conditions in advance of site investigation would allow better planning and reduce uncertainty with regard to ground instability. 5.2. Government policies One particular government policy is likely to have a significant impact on the demand for geohazard information in Great Britain. This is known as the Home Information Pack (2006)—essentially a report that the seller must provide to a buyer on the condition of their home—which will be introduced in 2007. At the time of writing, geohazards other than radon are listed as ‘authorised’ rather than ‘required’ information. This is expected to result in an increase in the demand for geohazard information from the current 600 000 reports per year. It is possible that all geohazard information may become ‘Required’ (i.e. mandatory); this could mean that as many as 1.4 million reports a year would need to be delivered. Efficient digital (web-based) delivery systems will be needed to cope with such demand. 6. Conclusions There is a proven need for geological hazard information to be readily available as easy to understand digital and paper products. The development of such products has
revealed a number of issues in relation to product-build costs, long-term maintenance and, in particular, the understanding of user need and the relevance of geology to everyday activities, and of the complexity of geological terminology. Government departments and environmental specialists have long acknowledged the importance and application of geohazard information. However, it is the more recent recognition of their value by commercial organisations, such as VARs, in answering house-buyers’ and developers’ questions with regard to ground stability and gas emissions, which has accelerated the demand for geohazard data. This has precipitated a change from complex scientific geological text into more easily understood language, which has, in turn, enabled greater and wider understanding of geohazard potential. Following the creation of high-resolution digital geology (DiGMapGB-50) a suite of national digital geohazard datasets has been developed and provided to a variety of users. These datasets are being maintained and updated to ensure users continue to have the most up-to-date and best quality information the BGS can provide. The methodologies will be reviewed and updated as data coverage improves and databases of occurrences expand enabling better quality control and validation of the potential hazards. In addition, new datasets will be added to meet the growing demand for information about a wider range of geological hazards and the existing hazard data will be provided at the larger 1:10 000 scale for urban and priority development areas. Acknowledgement This paper is published with the permission of the Executive Director of the British Geological Survey (NERC). References Appleton, J. D., 1995. Radon, methane, carbon dioxide, oil seeps and potentially harmful elements from natural sources and mining areas: characteristics, extent and relevance to planning and development in Great Britain: summary report: British Geological Survey, Analytical Geochemistry Series. Technical Report WP/95/4. Appleton, J.D., Miles, J.C.H., 2005. Radon in Wales. In: Bassett, M.G., Deisler, V.K., Nichol, D. (Eds.), Urban Geology in Wales: 2. Cardiff, National Museum of Wales Geological Series No. 24, pp. 117–129. Appleton, J.D., Miles, J.C.H., Scivyer, C.R., Smith, P.H., 2000. Dealing with radon emissions in respect of new developments. Summary report and recommended framework for planning guidance. British Geological Survey Research Report, RR/00/7, 26pp. Building Research Establishment (BRE), 1999. Radon: Guidance on Protective Measures for New Dwellings, 1999 ed. BR211, CRC Ltd., London, UK. Directive 2000/60/EC of the European Parliament and of the Council of 23 October 2000 establishing a framework for Community action in the field of water policy (WFD). Official Journal L 327, 22/12/2000, pp. 0001–0073. Forster, A., Culshaw, M.G., 2004. Implications of climate change for hazardous ground conditions in the UK. Geology Today 20 (2), 61–67.
ARTICLE IN PRESS J.C. Walsby / Quaternary International 171–172 (2007) 179–185 Jackson, I., Green, C., 2003. DigMapGB—the digital geological map of Great Britain. Geoscientist 13 (2), 4–7. Miles, J.C.H., Appleton, J.D., 2005. Mapping variation in radon potential both between and within geological units. Journal of Radiological Protection 25, 257–276. Planning Policy Guidance Note 14: Development on Unstable Land, 1990. Department of the Environment, UK. Planning Policy Guidance Note 14: Development on Unstable Land. Annex 1: Landslides and Planning, 1996. Department of the Environment, UK. Planning Policy Guidance Note 14: Development on Unstable Land. Annex 2: Subsidence and Planning, 2002. Department of Transport Local Government and the Regions, UK. Planning Policy Guidance Note 25: Development and Flood Risk, 2001. Department of Transport Local Government and the Regions, UK. Robins, N.S., Forster, A., Lewis, M.A., Butcher, A.S., 2003. Shallow and perched groundwater hazards and hazard mapping in the UK. In: Rodriguez, R., Civita, M., de Maio, M. (Eds.), Aquifer Vulnerability
185
and Risk: Proceedings of the First International Workshop. Salamanca, Mexico, No. 2, pp. 251–259. Rosenbaum, M.S., Culshaw, M.G., 2003. Communicating the risks arising from geohazards. Journal of the Royal Statistical Society Series A: Statistics in Society 166 (2), 261–270. Smith, A., Ellison, R.A., 1999. Applied geological maps for planning and development: a review of examples from England and Wales, 1983–96. Quarterly Journal of Engineering Geology 32, S1–S44. The Home Information Pack Regulations (HIP), 2006. Office of the Deputy Prime Minister. Draft for Publication, 31 October 2005. Statutory Instruments, Housing, England and Wales /http:// www.odpm.gov.uk/index.asp?id=1161272S. Wildman, G., Forster, A., 2005. Using GIS to create a Landslide Hazard Assessment Map for Great Britain. In: Proceedings of the Annual Conference of the AGI. Association for Geographical Information, London. Winter, M.G., Macgregor, F., Shackman, L. (Eds.), 2005. Scottish Road Network Landslide Study. Scottish Executive /http://www.scotland. gov.uk/Publications/2005/07/08131738/17395S.