Ironbridge Gorge Geomorphological Mapping August 2009 Jacobs Engineering UK Limited, Telford Hollinswood House, Stafford Park 1, Telford, Shropshire TF3 3DD Registered Office: Jacobs House, 427 London Road, Reading, Berkshire, RG6 Document Control Sheet Client: Telford and Wrekin Council Project: Ironbridge Gorge Study Project No: B1100100 Document(1), (2) Geomorphological Mapping Ref. 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Telford and Wrekin Council Ironbridge Gorge Geomorphological Mapping Contents 1 Introduction 1 1.1 Terms of Reference 1 1.2 Study Area 1 1.3 Previous Work 1 2 Geology 3 2.1 Solid 3 2.2 Superficial 3 2.3 Made Ground 4 3 Hydrology and Hydrogeology 5 3.1 Hydrology 5 3.2 Hydrogeology 6 4 Mining 7 4.1 Introduction 7 4.2 Coal 7 4.3 Ironstone 8 4.4 Clay 8 4.5 Limestone and Sandstone 8 5 Geomorphological Mapping 9 5.1 Methodology 9 5.2 Landslide Landsystems 9 5.3 Structural Defects 12 6 Descriptive Summaries 13 6.1 Introduction 13 6.2 Jiggers Bank 13 6.3 Benthall Edge 14 6.4 Ladywood 14 6.5 Lloyds Coppice 15 6.6 Jackfield 15 6.7 Blists Hill 17 6.8 Coalport 17 7 Hazard Zonation 19 7.1 Application of Hazard Zonation 19 7.2 Specific Areas of Instability 20 7.3 Review of Existing Information 22 8 Summary and Conclusion 23 i Telford and Wrekin Council Ironbridge Gorge Geomorphological Mapping Tables 1 Planning Guidance Zonation Scheme 2 2 Index of Maps 8 3 Classification of Structural Defects 12 Drawings Study Area Key Plan – Drg No. 1100100/G Geology and Geological Structure- Drg No. 1100100/01 Landslide Maps (title indicates extent of OS SJ sheet study area) Drg. No. Landslide 1100100G-SJ 6503 - 6603 Drg. No. Landslide 1100100G-SJ 6504 - 6604 Drg. No. Landslide 1100100G-SJ 6505 - 6605 Drg. No. Landslide 1100100G-SJ 6702 - 6802 Drg. No. Landslide 1100100G-SJ 6703 - 6803 Drg. No. Landslide 1100100G-SJ 6901 - 7001 Drg. No. Landslide 1100100G-SJ 6902 - 7002 Drg. No. Landslide 1100100G-SJ 6903 Planning Guidance Maps (title indicates extent of OS SJ sheet study area) Drg. No. Planning 1100100G-SJ 6503 - 6603 Drg. No. Planning 1100100G-SJ 6504 - 6604 Drg. No. Planning 1100100G-SJ 6505 - 6605 Drg. No. Planning 1100100G-SJ 6702 - 6802 Drg. No. Planning 1100100G-SJ 6703 - 6803 Drg. No. Planning 1100100G-SJ 6901 - 7001 Drg. No. Planning 1100100G-SJ 6902 - 7002 Drg. No. Planning 1100100G-SJ 6903 Appendices A Summary of Geological Sequence Drg. Stratigraphy B Ironbridge Gorge Mining Desk Study Drawings C040 D040 E040 F040 I040 J040 K040 P040 Q040 ii Telford and Wrekin Council Ironbridge Gorge Geomorphological Mapping C Line Geomorphology Plans Drg. Line Geomorph Rev A 6503-6603 Drg. Line Geomorph Rev A 6504 - 6604 Drg. Line Geomorph Rev A 6505 - 6605 Drg. Line Geomorph Rev A 6702 - 6802 Drg. Line Geomorph Rev A 6703 - 6803 Drg. Line Geomorph Rev A 6901- 7001 Drg. Line Geomorph Rev A 6902 - 7002 Drg. Line Geomorph Rev A 6903 D Structural Defects Plans Drg. Struc Defects Rev A 6503-6603 Drg. Struc Defects Rev A 6702 - 6802 Drg. Struc Defects Rev A 6703- 6803 Drg. Struc Defects Rev A 6902 - 7002 Drg. Struc Defects Rev A 6903 E List of Recent Planning Applications List of Recent Planning Applications Table E1 Inspected Planning Applications F Photographs F1 Jiggers Bank F2 Lloyds Coppice F3 Jackfield F4 Coalport iii Telford and Wrekin Council Ironbridge Gorge Geomorphological Mapping 1 Introduction 1.1 Terms of Reference 1.1.1 Jacobs Engineering UK Ltd have been commissioned by Telford and Wrekin Council (TWC) to undertake geomorphological mapping of the Ironbridge Gorge World Heritage Site. The purpose of the mapping is to provide base data for the formulation of ground instability hazard plans and planning guidance plans. These plans will be used by TWC to assist in development control and to ensure that an appropriate level of geotechnical investigation is provided with planning applications. In addition, the mapping work contributes to the understanding of slope instability within the Gorge, and will also help with prioritising future actions. 1.2 Study Area 1.2.1 The study area comprises the full extent of the World Heritage Site (Drawing 1100100/G), which covers an area of approximately 8 km2, but it excludes Ironbridge Town, which has already been mapped (see section 1.3 below). The study area includes the following seven districts, which from west to east are: • Jiggers Bank • Benthall Edge • Ladywood • Lloyds Coppice • Jackfield • Blists Hill • Coalport 1.3 Previous Work 1.3.1 This work follows on from the High-Point Rendel (HPR) Ground Behaviour Study (2005), which looked at instability hazards in Ironbridge Gorge and Coalbrookdale. The study combined desk study work reviewing ground conditions information, the history of past ground movement and the development of the study area, with engineering geomorphological field mapping and structural damage surveys, to produce a planning guidance map. The map classified the study area according to a five point scale of increasing potential instability hazard, and this was related to the level of information required to be submitted with planning applications. 1.3.2 The current study has used the HPR planning guidance zonation scheme (Table 1) in order to ensure that planning guidance remains compatible throughout contiguous areas and across the gorge as a whole. 1 Telford and Wrekin Council Ironbridge Gorge Geomorphological Mapping Table 1 Planning Guidance Zonation Scheme Zone Development Plan Policy Development Plan Proposals Development Control 1 Area suitable for Ground movement does not No Stability Report required. development in accordance impose any constraints on with the development plan. site development. 2 Area likely to be suitable for Ground movement does not An Outline Stability Report development in accordance impose significant would normally be required, with the development plan. constraints, although some prepared by a Competent mitigation/ stabilisation Person. measures may be required to ensure the stability of the site and surrounding land. 3 Area likely to be suitable for Ground movement imposes A Standard Stability Report development in accordance constraints that would would normally be required with the development plan generally require which may include subsurface provided the developer mitigation/stabilisation investigation and ground undertakes appropriate measures to ensure the movement monitoring and mitigation and stabilisation stability of the site and where appropriate details of measures. surrounding land. proposed stabilisation methods, prepared by a Competent Person. 4 Area unlikely to be suitable Ground movement imposes A Detailed Stability Report for development in accordance significant constraints that would normally be required with the development plan would generally require large- including detailed subsurface unless the developer scale mitigation/stabilisation investigation and ground undertakes appropriate measures to ensure the movement monitoring and mitigation and stabilisation stability of the site and where appropriate details of measures.