EXETER TONEWTON ABBOT GEO - ENVIRONMENTAL RESILIENCE STUDY Dawlish-Teignmouth Cliffs Unmanned Aerial Vehicle (UAV) Survey Interpretation Report Prepared for Network Rail October 2016 Halcrow Group Ltd. Burderop Park Wroughton SN4 0QD Exeter to Newton Abbot Geo-Environmental Resilience Study Dawlish-Teignmouth Cliffs Unmanned Aerial Vehicle (UAV) Survey Interpretation Report October 2016 Notice This document and its contents have been prepared and are intended solely for Network Rail’s information and use in relation to the Exeter to Newton Abbot Geo-Environmental Resilience Study. CH2M assumes no responsibility to any other party in respect of or arising out of or in connection with this document and/or its contents. Document History Version Date Description Created by Verified by Approved by 1 Oct 2016 Draft Oliver Dabson Roger Moore Peter Barter DAWLISH-TEIGNMOUTH CLIFFS UAV SURVEY INTERPRETATION REPORT Contents Section Page Contents ....................................................................................................................................... i Acronyms and abbreviations ........................................................................................................ ii 1. Introduction .................................................................................................................... 1 1.1 Summary ....................................................................................................................... 1 1.2 Data processing and quality control ............................................................................. 2 1.3 Visualisation software and interpretation approach .................................................... 4 2. Interpretation of UAV dataset .......................................................................................... 5 2.1 CBU 06 ........................................................................................................................... 5 2.2 CBU 07 ........................................................................................................................... 7 2.3 CBU 08 ........................................................................................................................... 8 2.4 CBU 09 ........................................................................................................................... 9 2.5 CBU 10 ......................................................................................................................... 10 2.6 CBU 11 ......................................................................................................................... 11 2.7 CBU 12 ......................................................................................................................... 12 2.8 CBU 14 ......................................................................................................................... 14 2.9 CBU 15 ......................................................................................................................... 15 2.10 CBU 16 (part)............................................................................................................... 17 2.11 CBU 17 ......................................................................................................................... 18 2.12 CBU 18 ......................................................................................................................... 20 2.13 CBU 19 ......................................................................................................................... 22 2.14 CBU 20 ......................................................................................................................... 23 2.15 CBU 21 ......................................................................................................................... 25 2.16 CBU 22 ......................................................................................................................... 28 2.17 CBU 23 ......................................................................................................................... 31 2.18 CBU 28 ......................................................................................................................... 34 2.19 CBU 29 ......................................................................................................................... 36 2.20 CBU 30 ......................................................................................................................... 38 3. Summary and Recommendations ................................................................................... 39 Appendix A: Location of CBUs .................................................................................................... 41 Appendix B: Baseline Report CBU Proformas .............................................................................. 45 Appendix C: UAV data capture areas .......................................................................................... 66 Appendix D: UAV Survey Scope .................................................................................................. 70 Appendix E: Specification of UAV Survey .................................................................................... 74 DAWLISH-TEIGNMOUTH CLIFFS UAV SURVEY INTERPRETATION REPORT I Acronyms and abbreviations BGS British Geological Survey CBU Cliff Behaviour Unit DEM Digital Elevation Model DPC Dense Point Cloud GCP Ground Control Point GPS Global Positioning System LiDAR Light Detection and Ranging NR Network Rail OS Ordnance Survey SSSI Site of Special Scientific Interest TGP Tony Gee and Partners UAV Unmanned Aerial Vehicle UTX Under-Track Crossing DAWLISH-TEIGNMOUTH CLIFFS UAV SURVEY INTERPRETATION REPORT II 1. Introduction 1.1 Summary This report provides an overview and the results of a survey by Unmanned Aerial Vehicle (UAV) of the coastal cliffs at Dawlish, which overlook or are adjacent to Network Rail (NR) infrastructure and operations. This builds on the assessment of these cliffs undertaken by CH2M in March 2015, which provided a systematic assessment of the geotechnical asset defects or “hazards” over the same area for the first time using archive aerial photography and LiDAR data. In the context of the assessment, the geotechnical assets of interest include both natural and engineered slopes that form the high cliffs alongside the up main line and above the tunnel portals between Dawlish Warren and Teignmouth stations (denoted Sections 2 to 4 in preceding CH2M reports, see Figure 1-1). The geotechnical asset outside of this prioritised section, including the coastal defence structures adjacent to the down main line, were specifically excluded from this assessment but were covered in other CH2M studies through 2015 and 2016. Figure 1-1: Extent of study area. UAV survey extent between Dawlish Warren and Teignmouth Stations DAWLISH-TEIGNMOUTH CLIFFS UAV SURVEY INTERPRETATION REPORT 1 The 2015 baseline report was a high-level report informed by a comprehensive review of available NR reports and datasets supplemented by published data available through regional and national archives, and along with CH2M’s own records, the reports and data have been collated into a fully georeferenced ArcGIS database. These data were supplemented by site observations and records obtained by CH2M geotechnical experts over the period January to March 2015 to characterise the geotechnical asset into discrete units based on cliff morphology and geology – known as Cliff Behaviour Units (CBUs). Following the mapping of the CBUs, a hazard rating for each was determined by an expert panel comprising NR and CH2M geotechnical and geomorphological experts. This classified each CBU into one of three hazard classes: 1. High (red), where the line may be affected for >48 hours or where there is a potential loss of life; 2. Medium (yellow) where the line is affected for <48 hours; or 3. Low (green) which has negligible impact to the line. Locations of each CBU are presented as Appendix A. Detailed proformas of each were documented to compile the hazard ranking, morphology characteristics, historical events, and other key attributes of each CBU, presented in Appendix B. The observations from this baseline report were made using limited data, particularly in Section 3 (Kennaway Tunnel to Parsons Tunnel) where there is no public access alongside the track and a track possession is required to view the cliffs. A UAV survey was proposed as a feasible method of remotely viewing the site at higher resolution and in more detail, to characterise the cliff morphology, geology, vegetation cover and condition, and provide further insight into the cliff instability processes which have occurred in the recent past and could occur in the future. In August 2015, CH2M prepared a Specification and Scope of Works for the UAV survey which detailed capture areas and target resolutions for the UAV imagery. The intention was to capture each CBU as a capture area, and also to capture the intervening headlands where marine erosion may impact the stability or integrity of tunnelled sections of the track; these areas can be viewed in Appendix C. However, a number of issues (which are explained further in Section 1.2 below) including unfavourable weather, technical issues with the aerial equipment, and lack of viewable control points affected the quality of the imagery captured. Data processing effort and interpretation was focused upon CBUs 16 to 23