Preprints
https://doi.org/10.5194/egusphere-2022-829
https://doi.org/10.5194/egusphere-2022-829
 
22 Sep 2022
22 Sep 2022

A climate-conditioned catastrophe risk model for UK flooding

Paul D. Bates1,2, James Savage2, Oliver Wing1,2, Niall Quinn2, Christopher Sampson2, Jeffrey Neal1,2, and Andrew Smith2 Paul D. Bates et al.
  • 1School of Geographical Sciences, University of Bristol, Bristol BS8 1SS, UK
  • 2Fathom, Square Works, 17-18 Berkeley Square, Bristol, BS8 1HB, UK

Abstract. We present a climate-conditioned catastrophe flood model for the UK that simulates pluvial, fluvial and coastal flood risks at 1 arc second spatial resolution (~20–25 m). Hazard layers for ten different return periods are produced over the whole UK for historic, 2020, 2030, 2050 and 2070 conditions using the UKCP18 climate simulations. From these, monetary losses are computed for Great Britain only for five specific global warming levels (0.6, 1.1, 1.8, 2.5 and 3.3 °C). The analysis contains a greater level of detail and nuance compared to previous work and represents our current best understanding of the UK’s changing flood risk landscape. Validation against historical national return period flood maps yielded Critical Success Index values of 0.65 and 0.76 for England and Wales respectively, and maximum water levels for the Carlisle 2005 flood were replicated to an RMSE of 0.41 m without calibration. This level of skill is similar to local modelling with site specific data. Expected Annual Damage in 2020 was £730M, which compares favourably to the observed value of £714M reported by the Association of British Insurers. Previous UK flood loss estimates based on government data are ~3x higher and lie well outside our modelled loss distribution, which is plausibly centred on the observations. We estimate that UK 1 % annual probability flood losses were ~6 % greater in the average climate conditions of 2020 than for the period of historical river flow and rainfall observations (centred approximately on 1995) and can be kept to around ~8 % if all countries’ COP26 2030 carbon emission reduction pledges and ‘net zero’ commitments are implemented in full. Implementing only the COP26 pledges increases UK 1 % annual probability flood losses by ~23 % above recent historical values, and potentially ~37 % if climate sensitivity turns out to be higher than currently thought.

Paul D. Bates et al.

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Referee Comment on egusphere-2022-829', Anonymous Referee #1, 24 Oct 2022
    • AC1: 'Reply on RC1', Paul Bates, 01 Nov 2022
  • RC2: 'Comment on egusphere-2022-829', Anonymous Referee #2, 02 Nov 2022
    • AC2: 'Reply on RC2', Paul Bates, 07 Nov 2022

Interactive discussion

Status: closed

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Referee Comment on egusphere-2022-829', Anonymous Referee #1, 24 Oct 2022
    • AC1: 'Reply on RC1', Paul Bates, 01 Nov 2022
  • RC2: 'Comment on egusphere-2022-829', Anonymous Referee #2, 02 Nov 2022
    • AC2: 'Reply on RC2', Paul Bates, 07 Nov 2022

Paul D. Bates et al.

Viewed

Total article views: 836 (including HTML, PDF, and XML)
HTML PDF XML Total Supplement BibTeX EndNote
579 241 16 836 75 3 2
  • HTML: 579
  • PDF: 241
  • XML: 16
  • Total: 836
  • Supplement: 75
  • BibTeX: 3
  • EndNote: 2
Views and downloads (calculated since 22 Sep 2022)
Cumulative views and downloads (calculated since 22 Sep 2022)

Viewed (geographical distribution)

Total article views: 772 (including HTML, PDF, and XML) Thereof 772 with geography defined and 0 with unknown origin.
Country # Views %
  • 1
1
 
 
 
 
Latest update: 30 Jan 2023
Download
The NHESS paper “A climate-conditioned catastrophe risk model for UK flooding” by Bates and colleagues presents and validates a new flood model for the UK that simulates pluvial, fluvial and coastal flood risks at a resolution of 20 to 25 metres. The authors then use their scheme to estimate the probability-loss distribution for UK flooding under various future climate and policy scenarios. Their paper provides the most detailed and realistic analysis to date of current and future flood risk in the UK. The key findings of their work are: (1) Previous UK flood losses based on government data and used in national climate change risk assessments are overestimated by a factor of about 3. (2) Official UK estimates lie well outside the paper's modelled loss distribution, which is plausibly centred on the observations. (3) The UK 1% annual probability flood losses were only about 6% greater in the average climate conditions of 2020 than for the period of historical river flow and rainfall observations (centred approximately on 1995). (4) Increases in risk can be kept to around ~8% if all COP26 2030 carbon emission reduction pledges and ‘net zero’ commitments are implemented in full. (5) Implementing only the COP26 pledges increases UK 1% annual probability flood losses by ~23% above recent historical values, and potentially ~37% if climate sensitivity turns out to be higher than currently thought.
Short summary
In this work we present and validate a new flood model for the UK that simulates pluvial, fluvial and coastal flooding. We show that previous UK flood losses based on government data and used in national climate change risk assessments are overestimated by a factor of ~3. These official estimates lie well outside our modelled loss distribution, which is plausibly centred on the observations.