National and Regional Risk Exposure in Low-Lying Coastal Areas Areal Extent, Population, Buildings and Infrastructure
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National and regional risk exposure in low-lying coastal areas Areal extent, population, buildings and infrastructure Prepared for the Parliamentary Commissioner for the Environment October 2015 Prepared by : R.G. Bell R. Paulik S. Wadwha For any information regarding this report please contact: Rob Bell Programme Leader: Hazards & Risk Coastal & Estuarine Processes +64-7-856 1742 [email protected] National Institute of Water & Atmospheric Research Ltd PO Box 11115 Hamilton 3251 Phone +64 7 856 7026 NIWA CLIENT REPORT No: HAM2015-006 Report date: October 2015 NIWA Project: PCE15201 Quality Assurance Statement Reviewed by: Dr Michael Allis (Coastal Engineer) Formatting checked by: Alison Bartley Approved for release by: Dr Sam Dean (Chief Scientist) © All rights reserved. This publication may not be reproduced or copied in any form without the permission of the copyright owner(s). Such permission is only to be given in accordance with the terms of the client’s contract with NIWA. This copyright extends to all forms of copying and any storage of material in any kind of information retrieval system. Whilst NIWA has used all reasonable endeavours to ensure that the information contained in this document is accurate, NIWA does not give any express or implied warranty as to the completeness of the information contained herein, or that it will be suitable for any purpose(s) other than those specifically contemplated during the Project or agreed by NIWA and the Client. Contents Executive summary ............................................................................................................. 9 1 Introduction ............................................................................................................ 19 1.1 Backdrop ................................................................................................................. 19 1.2 The purpose of the report ...................................................................................... 20 1.3 General assumptions and scope ............................................................................. 20 1.4 Scenarios versus elevation bands ........................................................................... 21 1.5 Report structure ..................................................................................................... 22 2 Counting the risk exposure: snapshot of the main results .......................................... 23 2.1 Coastal risk exposure .............................................................................................. 23 2.2 Results using the national topographic coverage ................................................... 23 2.3 Results using high-resolution LiDAR topography where available ......................... 25 3 Coastal hazards and climate-change: scenarios or elevation bands? .......................... 28 3.1 Introduction ............................................................................................................ 28 3.2 Coastal-inundation hazard processes ..................................................................... 29 3.3 Scenarios versus elevation bands ........................................................................... 35 4 Topography dataset processing ................................................................................ 39 4.1 Background to land elevation DEMs available nationally ...................................... 39 4.2 National DEM .......................................................................................................... 41 4.3 Regional LiDAR datasets ......................................................................................... 42 4.4 MHWS and MSL offsets around A-NZ ..................................................................... 51 5 Asset exposure and demographic processing ............................................................ 56 5.1 Asset data ............................................................................................................... 56 5.2 Asset exposure processing and outputs ................................................................. 57 5.3 Demographic processing from the 2013 Census .................................................... 59 6 Results for coastal-risk exposure: national DEM (0–3 m) ........................................... 60 6.1 Introduction ............................................................................................................ 60 6.2 Areal coverage of 0–3 m coastal elevation zone .................................................... 60 6.3 Population normally resident in 0–3 m coastal elevation zone ............................. 62 6.4 Land-use and parcels in 0–3 m coastal elevation zone .......................................... 64 6.6 Summary ................................................................................................................. 75 National and regional risk exposure in low-lying coastal areas 7 Results for coastal-risk exposure: LiDAR DEM elevation bands .................................. 76 7.1 Introduction ............................................................................................................ 76 7.2 Population normally resident in coastal-elevation bands (LiDAR) ......................... 76 7.3 Land-cover and parcels for the incremental coastal-elevation bands (LiDAR)....... 82 7.4 Built and infrastructure assets in coastal elevation bands (LiDAR) ........................ 88 8 Conclusions and gaps ............................................................................................. 119 8.1 Findings ................................................................................................................. 119 8.2 Gaps and recommendations ................................................................................. 124 9 Acknowledgements ............................................................................................... 127 10 Glossary of abbreviations and terms ...................................................................... 128 11 References ............................................................................................................. 130 Appendix A MHWS-10 heights around A-NZ ...................................................... 135 Appendix B Local MSL offsets ............................................................................ 140 Appendix C Result tables: buildings for the 0–3 m national DEM (regional, TLA and urban areas) ............................................................................ 141 Appendix D Result tables: infrastructure assets for the 0–3 m national DEM (regional, TLA and urban areas) ...................................................... 155 Appendix E Result tables: land assets for the 0–3 m national DEM (regional and TLA areas) ............................................................................... 164 Appendix F Result tables using LiDAR: Buildings for the 0–0.5 m, 0.5–1 m, 1–1.5 m elevation bands and aggregated 0–1.5 m zones (regional, TLA and urban areas) ...................................................................... 169 Appendix G Result tables: infrastructure assets for the aggregated 0–1.5 m LIDAR zone (regional, TLA and urban areas) .................................... 227 Appendix H Result tables: land assets for the aggregated 0–1.5 m LiDAR zone (regional, TLA and urban areas) ...................................................... 236 Appendix I Result tables: buildings for the aggregated 0–3 m LiDAR zone (regional, TLA and urban areas) ...................................................... 242 Appendix J Result tables: infrastructure assets for the aggregated 0–3 m LiDAR zone (regional, TLA and urban areas) .................................... 257 Appendix K Result tables: land assets for the aggregated 0–3 m LiDAR zone (regional, TLA and urban areas) ...................................................... 265 National and regional risk exposure in low-lying coastal areas Tables Table 4-1: Metadata, where available, on regional LiDAR DEMs or point cloud datasets supplied and used for this Project. 45 Table 4-2: Elevation bands for which GIS polygons were extracted and identifiers used for plotting results (by band or the cumulative elevation zones). 50 Table 5-1: RiskScape building inventory count and additional buildings identified within 10 m above MHW. 56 Table 5-2: Outline of procedure for aggregating various RiskScape building types into more general building use categories used for this Project. 58 Table 5-3: Outline of aggregation of various land cover types into the three general categories used in this Report. 59 Table 6-1: Regional distribution of coverage of the 0-3 m national DEM elevation- band polygons. 61 Table 6-2: Regional distribution of resident population in the 0-3 m elevation zone of the national DEM. 63 Table 6-3: Distribution by region of land-use by areas (0-3 m national DEM). 65 Table 6-4: Distribution of No. of land parcels for different land-cover types (0–3 m national DEM). 67 Table 6-5: Distribution by region of the No. of buildings for different classes. 70 Table 6-6: Regional distribution of replacement costs for residential and all building types and mean unit costs within the 0-3 m national DEM (2011 NZ$B). 71 Table 6-7: Regional distribution of length (km) of different classes of road (0-3 m national DEM). 72 Table 6-8: Regional distribution of railway length (km) in the 0-3 m national DEM. 73 Table 6-9: Regional distribution