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Application of Holistic Risk Based Framework

in Floodplain Management

Steven Molino & Steve Roso

Overview

• Background

• Framework – Molino & Roso 2012

• Risk Mapping Results

• Damages Results

• Limitations

• Using the results

Background

• Moreton Bay Regional Floodplain Database Project

• 14 Catchments

• 2,000 km2

• Consistent flood modelling and mapping

• Floodplain risk mapping

Molino Stewart 4

Risk Assessment Approach

• Categories of consequence and categories of likelihood. (NERAG, 2010)

• Acceptable Risk: not necessary to reduce the risk (green)

• Tolerable Risk: reasonably practical measures to reduce risk (yellow)

• Unacceptable Risk: society will not accept this risk and must be reduced to tolerable (red)

Insignificant

Consequence

Significant

Consequence

Severe Consequence

Low probability

Medium probability

High probability

Molino Stewart 5

Risk Types Considered

• Risk of isolation

• Risk to road access

• Risk to personal safety in residential buildings

• Risk to personal safety in non-residential buildings

• Risk to residential property

• Risk to non-residential property

• Risk to critical infrastructure

Topographic Categorisation

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Hydraulic Hazard Categorisation• Base hazard extracted using WaterRIDE for 10, 50,

100, 1000 and PMF events

• Duration that each hazard is exceeded for each

event (used in risk assessment)

Risk Assessment• Utilises the tables presented in Molino and Roso

(2012)

• Some minor modifications as proposed by MBRC and also where data is unavailable.

• Broad scale risk assessment mapping hadn’t been done before, exact methodology was refined in Pilot Study

Event range

(1 in X)

Maximum hazard category of surrounding floodwater

H1

H2 H3-H5

<24

hrs

>24

hrs

<24 hrs >24 hrs

Non

vulnerable

population

Vulnerable

population< 1,000 people > 1,000 people

1,000 - PMF

100-1,000

50 to <100

>10 to <50

10

Risk of

Isolation

Risk to Personal Safety - Residential

Molino Stewart 12

Existing Development

• More than 33,000 buildings in database

• Used database to assess for each:

– Risk to personal safety

– Risk to property

– Risk of isolation

– Tangible damages

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Risk to Personal Safety - Existing

Infrastructure Type Within infrastructure categorisation

Water Supply Local water supply

networkTrunk mains Reservoirs/Towers

Water Treatment Plant

processing infrastructure

Water Treatment Plant

throughput pumps and pipes and mains leading out of WTP

Source (e.g. Dam) and main

trunk

Electricity 11 kV distribution

system33 kV power cables 33/11 kV substation 110 kV power cables 110/33 kV substation

275/110 kV substation &

275kV and higher voltage power cables

TelecommunicationsCables connecting

mini exchangesMini exchanges

Other mobile phone towers cables

connecting terminal exchanges and mobile phone towers to switching

centres and each other

Terminal Exchanges And

critical mobile phone (cellular) transmission towers

intercity cables and cables

between switching centres

Radio transmission

infrastructure used by emergency services.

Telephone switching centres

Emergency Services Minor Evacuation CentreStation (Police/Fire

brigade/Ambulance/SES)

Major Evacuation Centre or

Control Centre (Police/Fire brigade/Ambulance/SES)

Sewage and waste Gravity PipesSewage pumps and waste tips

or landfill

Sewage Water Treatment

Plant

Health services Medical CentresPrivate Hospitals and aged

care facilitiesLocal Public Hospitals Regional Public Hospitals

dddddddddDuration

Event Range<24hrs >24hrs

1,000 - PMF

100-1,000

50 to <100

>10 to <50

10

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Using the Results

• Emergency Planning– Prioritise areas for emergency management– Determine what required to improve risk profile– Check evacuation routes – upgrade?– Work with infrastructure owners– Work with community – education/warning

• Town Planning– Avoid highest risk areas– Determine what features required to make other areas acceptable or

tolerable– Develop appropriate planning controls

• Mitigation Works– Check road and infrastructure impacts and quantify damages– Prioritise locations for flood mitigation or property modification works– Investigate costs and benefits of works (improved risk profile, reduced

damages)