Natural hazards known knowns and known unknowns Richard - - PowerPoint PPT Presentation

▶
natural hazards known knowns and known unknowns
SMART_READER_LITE
LIVE PREVIEW

Natural hazards known knowns and known unknowns Richard - - PowerPoint PPT Presentation

Dec 29, 2022 384 likes •673 views

Natural hazards known knowns and known unknowns Richard Reinen-Hamill Business Leader Natural Hazards There are known knowns. These are things we know that we know. There are known unknowns. That is to say, there are things that we

slide-1
SLIDE 1

Natural hazards – known knowns and known unknowns

Richard Reinen-Hamill Business Leader – Natural Hazards

“There are known knowns. These are things we know that we know. There are known unknowns. That is to say, there are things that we know we don't know. But there are also unknown unknowns. There are things we don't know we don't know.” Donald Rumsfeld

slide-2
SLIDE 2

Overview

  • Natural hazards and how do they affect NZ
  • Four examples of Natural Hazards and their impacts:

Canterbury Earthquake Sequence – climate change Tsunami Inundation risk in Tauranga Coastal erosion – addressing uncertainty and precautionary Landslide and fluidization

slide-3
SLIDE 3

Natural Hazards

Natural Hazard

A potential damaging physical event that may cause loss of life, injury or other health impacts, property damage, social and economic disruption,

  • r environmental damage.

Risk

The probability of harmful consequences, or expected losses resulting from interactions between hazards and vulnerable conditions R = Likelihood of a hazard x consequence is the most common NZ definition.

Disaster = Emergency in CDEM Act

slide-4
SLIDE 4

Top 10 Natural Disasters in NZ from 1900 to 2014 by fatalities

slide-5
SLIDE 5

Top 10 Natural Disasters in NZ from 1900 to 2014 by total affected

slide-6
SLIDE 6

Top 10 Natural Disasters in NZ from 1900 to 2014 by economic damage costs

slide-7
SLIDE 7
slide-8
SLIDE 8

The numbers

slide-9
SLIDE 9

SHAKING LIQUEFIES SATURATED FINE SAND/ SILTY SAND SETTLEMENT DAMAGE LIQUEFIED SAND EJECTS THROUGH CRUST

GROUNDWATER LEVEL

slide-10
SLIDE 10

Sea Level Rise

slide-11
SLIDE 11

LSN > 25 SEVERE LAND DAMAGE LSN 16 to 25 MINOR/MODERATE LAND DAMAGE LSN < 1 6 NONE/MINOR LAND DAMAGE

22% 27% 38%

SEVERE MODERATE MINOR

0m SLR 0.5m SLR 1.0m SLR

LAND DAMAGE:

MINOR MINOR MINOR

slide-12
SLIDE 12

LAND DAMAGE 22%

MINOR MINOR

38%

MINOR

0m 0.5m 1.0m

27% 26% 33% 44%

> 50% 20% to 50% < 50%

BUILDING DAMAGE

$ Repair Cost $ Replacement

SEA LEVEL RISE

slide-13
SLIDE 13

Key findings

  • Liquefaction hazard

risk varies with ground water level

  • Sea level rise is likely

to increase the severity of liquefaction effects in low lying coastal plains and reclaimed land

slide-14
SLIDE 14

Tauranga tsunami evacuation planning

slide-15
SLIDE 15
  • Modelled maximum probable tsunami

from Kermedec Fault

  • Travel time approx. 50 minutes to reach

coast

  • Wave heights up to 14m over Papamoa

frontal dunes but height varied along the coast

  • Inundation up to 2 km inland
  • Up to 90 minutes to flood to maximum

inland extents

Tsunami modelling

slide-16
SLIDE 16
slide-17
SLIDE 17

Key findings

  • Nearfield tsunamis make it

difficult for managed evacuation

  • Shore parallel roads do not help
  • Combination of improved

education and urban design features will help self evacuation

  • Depth and velocity information

useful for both damage and harm assessments

slide-18
SLIDE 18

Coastal erosion

  • Historically components summed

assuming complete dependence – increases conservatism

  • Uncertainty is included within a

factor of safety – increases conservatism

  • Have previously been used to derive

maximum potential extents

  • Not consistent with risk-based

approach

  • Difficult to define different levels of

likelihood as required under NZCPS

slide-19
SLIDE 19

Probabilistic CEHZ Assessment Approach

 

] [ SL T LT DS ST CEHZBeach     

slide-20
SLIDE 20

Probabilistic CEHZ Assessment Approach

  • Example – Waipu Cove 2115
  • Probabilistic hazard zone defined
slide-21
SLIDE 21

Probabilistic CEHZ Assessment Approach

Example – Waipu Cove 2115

Probabilistic hazard zone defined

How do we relate to terminology of NZCPS? Likely - Probability exceeded by 66% of events Potential

MfE (2008)

– exceeded by 5% of events

slide-22
SLIDE 22

Probabilistic CEHZ Assessment Approach

Example – Waipu Cove 2115

Probabilistic hazard zone defined

How do we relate to terminology of NZCPS? Likely - Probability exceeded by 66% of events Potential – exceeded by 5% of events

P66% ‘Likely’

P5% ‘Potential’

slide-23
SLIDE 23

Matata Debris Flow – 17 to 18 May 2008

slide-24
SLIDE 24
slide-25
SLIDE 25

Catchment response

100 100 year ear (m (m3/s) 18 18 May (m3/s) Deb Debris Fl Flood Deb Debris Fl Flow Pik Pikowai 68 135 Oh Ohinekoao 61 85 210 Awatarariki 44 66 325 Waim imea 7 Waim imea sou southern trib ibutary 4 11 20 to 30 Wait itepuru 14 180 to 270

slide-26
SLIDE 26

Key findings

  • Rainfall maybe 20 % greater than

expected 100 year rainfall

  • Water flows in streams up to twice

expected 100 year flows

  • Water and debris flows up to

maybe twenty times 100 year flood flows

slide-27
SLIDE 27

Questions?