Hawke Bay Coastal Hazard Strategy Meeting 2: Defining objectives - - PowerPoint PPT Presentation

Meeting 2: Defining objectives and parameters

Hawke Bay Coastal Hazard Strategy

Objectives

• Agree natural hazards to consider
• Agree approach – multi-hazard or individual risk,

qualitative/quantitative, full risk or specified return periods

• Agree return periods (range and number) for

each hazard

• Agree elements at risk to consider
• Agree scale and spatial extent

Refresher!

Natural hazards

Types of Natural Hazards

Atmospheric Seismic Hydrologic Geologic/ hydrologic Volcanic Wildfire Global

Hail storm Fault ruptures Coastal flooding Debris avalanche Tephra Brush Acid rain Hurricane Ground shaking Desertification Expansive soils Gases Forest atmospheric pollution Tornado Lateral spreading Salinization Landslides Lava flows Grass Global warming Cyclone Liquefaction Drought Rock falls Mud flows Savannah Sea level rise Tropical storms Tsunami Erosion and sedimentation Submarine slides Projectiles and lateral blasts El Nino Seiches Catchment flooding Subsidence Pyroclastic flows Storm surges

Suggested hazards to consider

• Coastal erosion (hydrologic)
• Storm surge and sea inundation

(atmospheric/hydrologic)

• Tsunami (seismic)
• Effect of sea level rise (global)

Additional hazard to consider

• Catchment flooding? (atmospheric)

Types of risk analysis

Types of risk analysis

Qualitative risk assessment

Quantitative Risk Assessment

Quantitative – Loss Exceedance Curves

Area under this curve gives the Average Annual Loss (AAL)

Annualised loss example

Event RP AEP (likelihood) Damage (Consequence) Annualised loss (AEP x Damage)

Storm 6/12/2012 - Auckland 60 0.0166667 $ 9,100,000 $ 151,667 Storm 18/05/2005 - BOP 500 0.002 $ 72,000,000 $ 144,000 Earthquake - Christchurch 2500 0.0004 $ 15,000,000,000 $ 6,000,000

Example of risk assessment in risk management

200 400 600 800 1000 1200 0.1 0.2 0.3 0.4 0.5 0.6

Cost $ AEP

Flood mitigation options

Without mitigation Scenario I Scenario 2

Average annual risk Risk reduction PRESENT 25.927 SCENARIO 1 19.315 6.612 SCENARIO2 9.7375 16.1895

Return periods

Return periods

• For risk based assessments need to consider at

least 3 return periods for each hazard event

• Alternative approach is to choose specific return

periods for each hazard

Design risk

Return periods

Term AS/NZS 4360 (2004) Landslide (Moon & Wilson, 2004) Australian Geomechanics Society, 2000 Extreme 1 <5 10 Very likely 5-10 Likely 3 50-500 100 Possible 10 500 - 5,000 1,000 Unlikely 30 > 5,000 10,000 Very unlikely 100 >>>5,000 100,000 Ultimate limit states Serviceability limit states Design working life Type Wind Earthquake 50 years Normal 1/500 1/500 1/25 Community 1/1000 1/1000 1/25 100 years Normal 1/1000 1/1000 1/25 Community 1/2500 1/2500 1/25

Traditional Hazard Assessment Approach

• Deterministic formula providing explicit hazard value
• Clarity as to effect of individual parameters and method of

derivation

• Well tested in New Zealand and internationally
• Modified for different coastal types
• Allows future modifications of individual components with new data,

methods or guidance

 

FS SL T LT DS ST CEHZBeach       ] [

Probabilistic Hazard Assessment Approach

• Probabilistic assessment
• No. of samples

 

SL T LT DS ST CEHZBeach     

• Probabilistic assessment –Waipu Cove 2115

P66% ‘Likely’ P5% ‘Potential’

Probabilistic CEHZ Assessment Approach

Elements at risk and vulnerability

Elements at risk

All objects, persons, animals, activities and processes that may be adversely affected by the hazard, directly or indirectly:

• Physical elements
• Essential facilities
• High potential loss facilities
• Transportation facilities
• Lifelines
• Population
• Socio-economic aspects
• Economic activities
• Environmental elements

Scale: Land use the most important spatial attribute

Vulnerability – types of losses

Methods for physical vulnerability assessments

Increased computational cost and effort

Expressing vulnerability

• Vulnerability indices
• Fragility curves
• Vulnerability curves
• Vulnerability tables

Scale and scenarios

Scale: Land use the most important spatial attribute

Risk reduction or mitigation options

Avoidance Eliminate the risk by modifying the hazard Reduce Mitigate the risk by modifying the vulnerability to damage and disruption Transfer Outsource or insure and modify the financial impact of hazards Accept Accept and budget for the expected damages

Risk reduction Structural Seawalls, levees, dams, building strengthening, etc. Non-structural Policy/planning Legal and regulatory Organization structures Resources Research Preparedness and contingency planning Early warning Emergency planning Information and communication Education and training Public awareness

Possible scenarios

• Divide area into units (wards/suburbs/areas etc)
• Carry out hazard mapping for selected hazards

and scenarios (3 for current day and 3 for each future sea level rise scenarios)

• Risk assessment to identify average annual loss

for current day and future scenarios

• Identify responses/treatments
• Re-run to evaluate cost/benefit of options

Round-up

Check on progress

• Agree natural hazards to consider
• Agree approach – multi-hazard or individual risk,

qualitative/quantitative, full risk or specified return periods

• Agree return periods (range and number) for

each hazard

• Agree elements at risk to consider
• Agree scale and spatial extent