Leeds: a geological background for planning and development : 1:10000 sheets SE23NW, NE, SE and SE33NW, NE, SW, SE: parts of 1:50000 geological sheets 69 (Bradford), 70 (Leeds), 77 (Huddersfield) and 78 (Wakefield)

This study, carried out between 1989 and 1991, was commissioned by the Department of the Environment and funded jointly by the Department and the British Geological Survey. Its principal aim was to produce a synthesis of geological information relevant to the land-use planning for development and redevelopment for a large part of the Leeds district. This report is aimed at those involved in planning and development. Much of the information is provided on a series of thematic maps, each of which concentrates on a specific aspect of the geology relevant to landuse. These are suitable for use in forward planning for development and conservation, and as a background to desk studies, prepared in advance of specific development proposals. However, they must not be used in place of results of adequate site investigations when development is being considered. In addition to the information contained in the report, sources of other more detailed data are indicated

Absolute fixing of tide gauge benchmarks and land levels : the BGS contribution to a report on a study of the London and Thames estuary region

This report comprises material submitted as the British Geological Survey (BGS) contribution to the final report of a project measuring changes in land and sea levels using high precision global positioning system (GPS) surveying, absolute gravimetry (AG), persistent scatterer interferometry (PSI) and tide gauge records. Data was collected during the period 1997 to 2005 for a National study of changes around the coast of Great Britain, and a Regional study of changes along parts of the Thames Estuary and the River Thames at London. Since 2003, the national study has been funded by the Joint DEFRA/EA Flood and Coastal Erosion Risk Management R&D Programme, and a regional study, funded by the Environment Agency Thames Estuary 2100 project. The national study was carried out jointly by the Proudman Oceanographic Laboratory (POL) and the University of Nottingham’s Institute of Engineering Surveying and Space Geodesy (IESSG). The regional study was led by IESSG and carried out jointly by IESSG, POL, Nigel Press Associates Ltd. (NPA) and the British Geological Survey (BGS). The item in the project research plan relevant the main BGS input is Objective 08: ‘The estimates of changes in absolute ground level for the regional network of 13 GPS stations and a few thousand PSI points (output from 07) will be analysed, and geological interpretations presented using the geological database and other available information’. The final project report includes a condensed version of this material, with only a few of the figures. That is due to be published as Environment Agency R&D Technical Report FD2319/TR. The geological setting of the London region is described in a report for the EA/NERC CONNECT B project (Bingley et al., 1999), and by Ellison et al. (2004)

Rapid methods of landslide hazard mapping : Fiji case study

A landslide hazard probability map can help planners (1) prepare for, and/or mitigate against, the effects of landsliding on communities and infrastructure, and (2) avoid or minimise the risks associated with new developments. The aims of the project were to establish, by means of studies in a few test areas, a generic method by which remote sensing and data analysis using a geographic information system (GIS) could provide a provisional landslide hazard zonation map. The provision of basic hazard information is an underpinning theme of the UN’s International Decade for Natural Disaster Reduction (IDNDR). It is an essential requirement for disaster preparedness and mitigation planning. This report forms part of BGS project 92/7 (R5554) ‘Rapid assessment of landslip hazards’ Carried out under the ODA/BGS Technology Development and Research Programme as part of the British Government’s provision of aid to developing countries. It provides a detailed technical account of work undertaken in a test area in Viti Levu in collaboration with Fiji Mineral Resources Department. The study represents a demonstration of a methodology that is applicable to many developing countries. The underlying principle is that relationships between past landsliding events, interpreted from remote sensing, and factors such as the geology, relief, soils etc provide the basis for modelling where future landslides are most likely to occur. This is achieved using a GIS by ‘weighting’ each class of each variable (e.g. each lithology ‘class’ of the variable ‘geology’) according to the proportion of landslides occurring within it compared to the regional average. Combinations of variables, produced by summing the weights in individual classes, provide ‘models’ of landslide probability. The approach is empirical but has the advantage of potentially being able to provide regional scale hazard maps over large areas quickly and cheaply; this is unlikely to be achieved using conventional ground-based geotechnical methods. In Fiji, landslides are usually triggered by intense rain storms commonly associated with tropical cyclones. However, the regional distribution of landslides has not been mapped nor is it known how far geology and landscape influence the location and severity of landsliding events. The report discusses the remote sensing and GIS methodology, and describes the results of the pilot study over an area of 713 km2 in south east Viti Levu. The landslide model uses geology, elevation, slope angle, slope aspect, soil type, and forest cover as inputs. The resulting provisional landslide hazard zonation map, divided into high, medium and low zones of landslide hazard probability, suggests that whilst rainfall is the immediate cause, others controls do exert a significant influence. It is recommended that consideration be given in Fiji to implementing the techniques as part of a national strategic plan for landslide hazard zonation mapping

The accuracy of ASTER digital elevation models : a comparison with NEXTMap Britain

In many overseas geological surveying projects an accurate elevation model is often required for analysis, image orthorectification, navigation and the generation of contours. Acquiring an accurate elevation model can be a difficult and expensive task. One possible solution is to generate a digital elevation model (DEM) from Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) satellite imagery. However, to fully understand the potential of ASTER DEMs the accuracy of these models needs to be established. The DEM was created using the Sulsoft ASTER DTM add-on ENVI module. NEXTMap provides an ideal reference dataset for comparison. In this study the accuracy of an ASTER generated DEM was assessed for a 50×50 km area in central Wales. A total of 2.4 million points were compared. Visual and statistical assessments were made, including profile and contour comparisons, allowing the spatial variation in accuracy to be explored. A mean vertical difference of –0.98 m and a standard deviation of c. 9 m were calculated. This suggests that 95% of the ASTER DEM points are within ±20 m of the NEXTMap DEM. Considering these accuracy levels, contours from ASTER can be generated at 40 m intervals

Evaluation of ENVI feature extraction for geological mapping in arid environments

Object-Based Land Analysis Meeting, University of Nottingham, 7-8 April 2009 Arid environments provide ideal conditions for evaluating emerging technologies for geological mapping. This is due mainly to the lack of vegetation that otherwise covers the geological materials and prevents them from direct observation. The most common approach to geological mapping by remote sensing involves: (i) calibration of image DN values to radiance; (ii) conversion to spectral reflectance and (iii) spectral analysis, commonly by Principal Component techniques or by comparing spectral signatures of image pixels with spectral libraries of known geological materials. Although the PC technique provides good spectral separation it is often difficult to generate suitable boundaries between the spectrally diverse units as they often become disjointed with the introduction of errors on application of region smoothing algorithms. Spectral signature analysis is often more temperamental where slight variations in spectral signatures from the reference libraries can result in small inliers of unclassified material that are clearly from the same geological unit. The ENVI Feature Extraction module enables segmentation of multi-band images into spectrally diverse components by including both spectral characteristics and surface texture in the analysis. There is also an option to include topographic information. Multiband spectral images have been obtained for several geological settings, mainly from arid environments: (i) Morocco, Saudi Arabia & Afghanistan, in a complex setting of sedimentary and metamorphic geology with igneous intrusions; (ii) Algeria, over a sedimentary sequence; (iii) Ethiopia, over rifting volcanic terrain, and (iv) Tristan-da-Cunha, a volcanic island in the South Atlantic Ocean. ASTER images for each of these areas have been ortho-rectified and atmospheric effects removed from the radiometrically calibrated data using the FLAASH algorithm, with the resultant reflectance images used to evaluate the ENVI Feature Extraction Module. For some of these areas, detailed geological information has recently been obtained through extensive geological mapping expeditions, thus providing good base geological data with which to compare the results of the ENVI Feature Extraction procedure. We present results from the ENVI Feature Extraction for these different geological settings

Rapid methods of landslide hazard mapping : Papua New Guinea case study

A landslide hazard probability map can help planners (1) prepare for, and/or mitigate against, the effects of landsliding on communities and infrastructure, and (2) avoid or minimise the risks associated with new developments. The aims of the project were to establish, by means of studies in a few test areas, a generic method by which remote sensing and data analysis using a geographic information system (GIS) could provide a provisional landslide hazard zonation map. The provision of basic hazard information is an underpinning theme of the United Nations International Decade for Natural Disaster Reduction (IDNDR). It is an essential requirement for disaster preparedness and mitigation planning. This report forms part of BGS project 92/7 (R5554) ‘Rapid assessment of landslip hazards’ carried out under the ODA/BGS Technology Development and Research Programme as part of the British Government’s provision of aid to developing countries. It provides a detailed technical account of work undertaken in a test area in the highlands of Papua New Guinea (PNG) in collaboration with the Geological Survey Division. The study represents a demonstration of a methodology that is applicable to many developing countries. The underlying principle is that relationships between past landsliding events, interpreted from remote sensing, and factors such as the geology, relief, soils etc. provide the basis for modelling where future landslides are most likely to occur. This is achieved using a GIS by ‘weighting’ each class of each variable (e.g. each lithology ‘class’ of the variable ‘geology’) according to the proportion of landslides occurring within it compared to the regional average. Combinations of variables, produced by summing the weights in individual classes, provide ‘models’ of landslide probability. The approach is empirical but has the advantage of potentially being able to provide regional scale hazard maps over large areas quickly and cheaply; this cannot be achieved using conventional ground-based geotechnical methods. In PNG, landslides are usually triggered by earthquakes or intense rain storms. Tectonic instability and the extreme ruggedness of the terrain make the highlands very susceptible to landsliding, but the extent to which regional factors influence the distribution and severity of landsliding is uncertain. The report discusses the remote sensing and GIS methodology, and describes the results of the pilot study over an area of approximately 4 500 km2 in the Kaiapit/Saidor districts of the Finisterre mountain range. The landslide model uses geology, elevation, slope angle, lineaments and catchments as inputs. The resulting provisional landslide hazard zonation map, divided into 5 zones of landslide hazard probability, suggests that regional controls on landslide occurrence do exist and are significant. It is recommended that consideration be given in PNG to implementing the techniques as part of a national strategic plan for landslide hazard zonation mapping

Regional appraisal of the potential for stratabound base-metal mineralisation in the Solway basin

The Carboniferous Solway-Northumberland extensional basin covers an area of 6500 krn in northern England and southern Scotland (Figure 1.1). The basin, which is up to 7 k.m thick, developed due to N-S extension with major fault-controlled subsidence during the Courceyan-Holkerian (syn-extension phase), followed by more gradual post-extension regional subsidence during the later Carboniferous. It straddles the trace of the Iapetus Suture which marks the collision zone of the palaeo-North American and palaeo-European continents during Caledonian times. The major Irish lead-zinc deposits, including the world-class Navan deposit lie along the western extension of the Iapetus Suture. The basin is poorly exposed away from the margins and is covered by later Penno-Trias sediments. Much of the basin is also mantled with extensive drift deposits. Minor lead-zinc vein and replacement mineralisation occurs along the northern boundaJy of the basin, close to the contact with the underlying Lower Palaeozoic rocks of the Southern Uplands and vein style mineralisation carrying barite and minor base metals occurs along the southern margin at the contact with the Lower Palaeozoic rocks of the Lake District. More extensive syn-diagenetic mineralisation of Sedex style found in Ireland may occur adjacent to the major basin-controlling faults. Investigations of the regional geochemistry. geophysics and deep geology, together with Landsat imagery, show that the basin could be prospective for this style of mineralisation, but that the most likely rocks, in tenns of chronostratigraphy, are likely to be at considerable depth on the southern margin. However, suitable conditions for the emplacement of this mineralisation may be found in several areas close to the northern margin and in the Bewcastle Anticline