ecological risk based decision making model

7/30/2019 Ecological Risk Based Decision Making Model

http://slidepdf.com/reader/full/ecological-risk-based-decision-making-model 1/17

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Submission on the strategic review of the impacts of underground mining in the Wyong LGA

Ecological Risk-Based

Decision-Making Model



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Table of Contents

INTRODUCTION................................................................... 3 PROCESS ........................................................................... 3 STREAM RISK MATRIX.......................................................... 6 SWAMP/WETLAND RISK MATRIX............................................ 7 CONSEQUENCE TABLES........................................................ 8

STREAMS ...........................................................................................8 SWAMPS AND WETLANDS .........................................................................9

APPLICATION OF THE MODEL...............................................10 WORKED EXAMPLE 1 - LONGWALL PANEL 50M FROM PERENNIAL RIVER...................10 WORKED EXAMPLE 2 - LONGWALL PANEL DIRECTLY UNDERNEATH STREAM ...............12 WORKED EXAMPLE 3 - LONGWALL PANEL 280M AWAY FROM STREAM.....................14

DEFINITIONS.....................................................................16



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Introduction

DECC has developed an Ecological Risk-Based Decision-Making Model, inconsultation with subsidence and risk assessment experts, as a proposed means for

protecting high value natural features from subsidence impacts.

Note: The model will require further development and is presented here asa conceptual framework rather than a finished product.

Following is a:

• a description of the process

• a risk matrix for streams and swamps• risk matrix consequence tables• definitions of all terms used

• example application of the model on current longwall mining project areas.

Process

Given the uncertainties in the current understanding of the impacts of subsidenceto natural features, the model entails a qualitative risk assessment approach as

outlined. At present, current data available is more amenable to a qualitative riskassessment. However, as the body of monitoring data grows, quantitative

assessments may become preferred.

It is intended that the model would be used by a risk assessment panel, withexpertise in:

• water dependent ecosystems• subsidence

• risk assessment

The model process involves:

1. the identification of natural features or ‘ecological assets’ that have been

identified as falling with the longwall mining project area

Separate risk matrix tables have been developed for the following key types of

natural feature or ‘ecological asset’:•

streams• swamps/wetlands.

2. determining ecological value by assessing: hydrological character, habitatfeatures and biodiversity values

These criteria are set out in a dichotomous key to enable the user to determine

an overall relative ranking of ecological value. Refer to the risk matricespresented below.



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3. the determination of the adverse consequence of impact (see Consequence

Tables below)

The determination of consequence is undertaken by assigning ‘scores/values’ to the

functional values of an ecological asset: hydrological character, habitat features andbiodiversity values.

4. the determination of the likelihood of an impact with the adverse consequencestated

Likelihood Rating is rated as:• High = 3

• Medium = 2

• Low = 1

The likelihood will be a result of the assessment of:

• predicted subsidence•

tilt and strain• upsidence and closure• whether or not the longwall panel passes directly under a stream (or is

within its angle of draw)

• distance the longwall is away from the feature being assessed.

The determination of likelihood of subsidence should be as quantitative as possiblegiven existing data and confidence levels. It is suggested that two models could be

used in determining the likelihood to account for discrepancies between modelsused across the longwall mining industry. Model results should be peer reviewed byexternal subsidence experts for validation. Additionally, the model(s) used should

be validated/confirmed by comparing results with all available data and casestudies from previous mining.



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As a general rule, one or more of the following definitions can be applied in

assigning likelihoods, based on data quality available.

Likelihood

Qualityof under-

pinning dataavailable

High Medium Low

Subjectivedefinition, where judgement is

required due tolack of data andpredictive

capability.

The stated adverseconsequence isreasonably

foreseeable and notunlikely to occur.

The stated adverseconsequence ispossibly but

unlikely to occur.

The statedadverseconsequence is

not reasonablyforeseeable orimpossible.

Statisticaldefinition, where

predictivemodelling ispossible usingextrapolation from

a database of experience.

Quantitative modelspredict that the

stated adverseconsequence has asignificant (≥ 5%)chance of

occurrence.

Quantitative modelspredict that the

stated adverseconsequence has apossible (≥ 0.5% to≤ 5%) chance of

occurrence.

Quantitativemodels predict

that the statedadverseconsequence ishighly unlikely (<

0.5%) chance of occurrence.

Empirical

definition, whereempirical evidence

from the past issufficiently sound

so as to makeassumptions

about the future.

Experience from

similar scenarioshas shown that the

stated adverseconsequence could

have occurred at asignificant

frequency (≥ 5% of comparableobservations where

n ≥ 20).

Experience from

similar scenarioshas shown that the

stated adverseconsequence could

have occurred (≥ 0.5% to ≤ 5% of

comparableobservations wherewhere n ≥ 20).

Experience from

similar scenarioshas shown that

the stated adverseconsequence

could have notoccurred

previously and n≥ 100.

5. Risk Rating: Given Risk = Likelihood x Consequence

6. the determination of the Management Measure to be employed: Prevent Impact,Minimise Impact and Proceed with Caution

The Management Measure is determined by the Risk Rating score. The associatedrelationship between Management Measure and Risk Rating is demonstrated in thefollowing table.

Risk Risk Category Scores Management Measure

High 65-90 Prevent Impact

Medium 35-65 Minimise Impact

Low 10-35 Proceed with Caution



Stream Risk Matrix

AssetHydrological

Character Habitat Features

Biodiversity

Values

Community

Measure

Ecological

Value

Consequence

- Refer to

Consequence

Tables

stream perennial

rock bars, pools, riffles

and/or macrophyte

beds that provide

aquatic habitat

threatened species

present

and/

or

iconic species or

high diversityH

no threatened

species presentand

no iconic species

or high diversityH

no rock bars, pools,

riffles or macrophyte

beds that provide

aquatic habitat

threatened species

present

and/

or

iconic species or

high diversityH

no threatened

species presentand

no iconic species

or high diversityM

intermittent


and/or macrophyte

beds that provide

habitat

threatened species

present

and/

or

iconic species or

high diversityH

no threatened

species presentand

no iconic species

or high diversityM



beds that provide

habitat

threatened species

present

and/

or

iconic species or

high diversityH

no threatened

species presentand

no iconic species

or high diversityL

ephemeral


and/or macrophyte

beds that provide

habitat

threatened species

present

and/

or

iconic species or

high diversityH

no threatened

species presentand

no iconic species

or high diversityL



beds that provide

habitat

threatened species

present

and/

or

iconic species or

high diversityH

no threatened

species presentand

no iconic species

or high diversityL

D et er mi n e C on s e q u en c e ( Hi gh ,M e d i um ,L ow )

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Swamp/Wetland Risk Matrix

AssetHydrological

Character

Habitat

Features

Biodiversity

Values

Community

Measure

Ecological

Value

Consequence

Refer to

Consequence

Tables

wetlands

and

swamps

open water

large, or part of a

system of

wetlands

threatened

species present

and/

or

migratory

species

habitat or

high diversity

H

no threatened

species presentand

no migratory

species

habitat, low

diversity

H

small isolated

wetland

threatened

species present

and/

or

migratory

species

habitat or

high diversity

H

no threatened

species presentand

no migratory

species

habitat, low

diversity

M

swamp that

feeds perennial

stream

part of a

significant cluster

of swamps

threatened

species habitat

present

and/

or

iconic

species or

high diversity

H

isolated swamp

threatened

species habitat

present

and/

or

iconic

species or

high diversity

H

swamp that

feeds

intermittent or

ephemeral

stream

part of a

significant cluster

of swamps

threatened

species habitat

present

and/

or

iconic

species or

high diversity

H

isolated swamp

threatened

species habitat

present

and/

or

iconic

species or

high diversity

H

D et er mi n e C on s e q u en c e ( Hi gh ,M e d i um ,L ow )

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Consequence Tables

Streams

Table 1.1 Hydrological Character

Stream FlowSeverity

RatingDuration of

PotentialImpact

Rating Severity RatingExtent

UpstreCatchm

Perennial

Intermittent

Ephemeral

3

2

1

Permanent

Year

Month

Day

4

3

2

1

Complete loss of surface flow

Partial loss of

surface flow

No detectable loss

3

2

1

Large

Medium

Small

Table 1.2 Biodiversity Values

Severity Rating Threatened Species RatingEndemic to

RegionComplete loss of stream dependent

species

Partial loss of stream dependent species

No detectable loss of stream dependent

species

3

2

1

Yes

No

2

1

Yes

No

Table 1.3 Habitat Features

Severity Rating Duration of Potential Impact Rating Extent of Potentia

Complete loss of habitat

Partial loss of habitat

No detectable loss of habitat

3

2

1

Permanent

Year

Month

Day

4

3

2

1

Large reach/multipl

Medium reach/mult

Small reach/1 habit

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Submission on the strategic review of the impactsof underground mining in the Wyong LGA



Swamps and wetlands

Table 2.1 Hydrological Character

Swamp/WetlandType

Rating

Duration of Potential

ImpactRating Severity Rat

Swamp with Open

Water

Swamp without OpenWater

2

1

Permanent

Year

Month

Day

4

3

2

1

Fracturing of underlying bedrock,

desiccation, gullying and completeloss of wetland

Fracturing of underlying bedrock,desiccation, gullying and partial

loss of wetland

No detectable loss

3

2

1

Table 2.2 Biodiversity Values

Severity Rating Threatened Species Rating Endemic

Complete loss of swamp dependent species

Partial loss of swamp dependent species

No detectable loss of swamp dependent species

3

2

1

Yes

No

2

1

Y

Table 2.3 Habitat Features

Severity Rating Duration Rating Extent

Complete loss of habitat

Partial loss of habitatNo detectable loss of habitat

3

21

Permanent

YearMonth

Day

4

32

1

Large swamp/multiple hab

Medium swamp/multiple hSmall swamp/fewer habita

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Application of the model

Worked Example 1 - Longwall panel 50m from perennial r iver

Consequence to Hydrological Character – see Consequence Table 1.1

Consequence Attribute Decision

Stream flow Perennial

Duration Month

Severity Partial loss

Extent Large

Total Score

Consequence to Biodiversity – see Consequence Table 1.2


Severity No detectable loss

Threatened Species Yes (Macquarie perch)

Endemic Yes

Total Score

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Consequence to Habitat (Geomorpholical features – see Consequence Table 1.3


Severity No detectable loss

Duration Month

Extent Small reach

Total Score

Consequence Score*

* Consequence Score (Hydrological + Biodiversity + Habitat = 10+5+4=19)

Dynamic Range: Maximum Overall Consequence Score = 30. Minimum Overall Consequence

Likelihood Rating - rated as:High = reasonably foreseeable or likely = 3Medium = possible but unlikely = 2Low = not reasonably foreseeable or impossible = 1

For this worked example (longwall panel 50m from river) The likelihood assigned was ‘Medium

Given Risk = Likelihood x Consequence, the Risk Rating = 19 x 2 = 38

Dynamic Range: Maximum Overall Risk Rating Score = 90. Minimum Overall Risk Rating Score

In this approach because the Risk Rating was assessed at 38 it would have fallen in Medium ca

Impact Management Measure.

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Worked Example 2 - Longwall panel directly underneath stream

Consequence to River connectivity – see Consequence Table 1.1


Stream flow Perennial Duration Permanent

Severity Complete loss

Extent Medium

Total Score


Consequence Attribute Decision S

Severity Complete loss 3

Threatened Species Yes (Macquarie perch) 2

Endemic Yes 2

Total Score 7

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Consequence to Habitat (Geomorphological features – see Consequence Table 1.3



Duration Permanent

Extent Medium reach

Total Score

Consequence Score

Likelihood

For this worked example (longwall panel directly underneath a stream), likelihood is scored 3.

Given Risk = Likelihood x Consequence, the Risk Rating = 27 x 3 = 81

In this approach because the overall risk rating was assessed at 81 it would have fallen in HighImpact Management Measure. This would seem appropriate given that the longwall panel goesand is likely (on the basis of past case examples) to cause major damage.

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Worked Example 3 - Longwall panel 280m away from stream

Consequence to River connectivity – see Consequence Table 1.1

Consequence Attribute Decision S

Stream flow Perennial 3

Duration Month 2

Severity Partial loss 2

Extent Large 3

Total Score 1


Consequence Attribute Decision Sc

Severity Partial loss 2

Threatened Species Yes (Dragonfly) 2

Endemic Yes 2

Total Score 6

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Consequence to Habitat (Geomorphological features – see Consequence Table 1.3



Duration Month

Extent Small reach

Total Score

Consequence Score

Likelihood

For this worked example (longwall panel 280m from centre of a stream), the likelihood is score

Given Risk = Likelihood x Consequence the Risk Rating = 21 x 1 = 21

In this approach because the overall risk rating was assessed at 21 it would have fallen in Lowwith Caution Management Measure.

This would seem appropriate given that the longwall panel is 280m away from the stream and are low.



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Definitions

asset: AU ecologically important landscape feature, an ecologicalcommunity, or a species.

consequences: The effect of subsidence impacts (loss of surface water, loss of

swamp groundwater, pollution of water, etc.) to the asset beingassessed, ranked numerically based on severity and persistence of impact.

day: up to 24 hours

ecological value: A relative (high, medium or low) rating applied to sites based on thepresence of endangered species or ecological communities, thepresence of high biodiversity or iconic species, and the importance of the site as habitat for a range of species.

ephemeralstream:

A stream that flows only after rainfall.

habitat features: Within channel features such as rock bars, pools and riffles.hydrologicalcharacter:

Surface water flow throughout reaches of a stream that connectshabitats and allows fish and invertebrate migration.

hydrologicfunction:

A water flow regulation function. Examples are: rock bars creatingpools upstream from the bar; and swamps storing rainwater for slowrelease as perennial flow to streams.

iconic species: A species that the community cares about, for example, Platypus.

intermittentstream:

A stream that stops flowing during dry periods. These streams haveconnectivity during and for some time after rainfall.

key habitats Areas of predicted high conservation value for forest faunal

assemblages, endemic forest vertebrates or endemic invertebrates;spatially depicted as a merging of mapped assemblage hubs,

assemblage hot spots and centres of endemism.

large reach: > 1 km

largeswamp/wetland:

> 1 Ha

likelihood of impact:

The relative likelihood of an impact with the stated adverseconsequence occurring, taking into account past knowledge and

experience. This will be calculated by the amount of subsidencepredicted applied to the susceptibility of the feature to subsidenceimpacts (for example, rock bars and swamp beds are particularly

susceptible to fracturing if subsidence and/or upsidence exceedscertain thresholds).

managementmeasure:

The measure that is required to be applied for each level of risk.

medium reach: 100m to 1km

mediumswamp/wetland:

200m2 to 1Ha

minimise impact: To minimise any impact to an ecological asset, as low as is

reasonably practicable. This may be achieved by a range of measures related to mine geometry and mining methods.

month: 1 to 31 days




multiple habitats: Pools, riffles, macrophyte beds, cascades

perennial stream: A stream that flows all year round except during drought. Note: theperenniality of a stream can be inferred by the macroinvertebratespresent.

permanent: More than 12 months (irreversible)

prevent impact: To prevent impact to the asset that would affect its ecological values.For example, for a stream it would mean to prevent impact to flow

connectivity, rock bars and pools, species diversity and/orthreatened or iconic species. It may be achieved by a range of

measures related to mine layout, mine geometry and miningmethods.

proceed with

caution:

The management measure monitor means to proceed with mining

while regularly monitoring for any impacts to the asset, and to havetriggers and management measures in place in the event of anunintended or unpredicted impact being detected.

risk rating: The risk rating for an asset with particular features is calculated by

multiplying the likelihood of impact by the ecological consequence .

small reach: < 100m

smallswamp/wetland:

< 200m2

stream: The term stream is used to encompass all flowing natural waters,

regardless of size.

threatenedspecies:

Species that are listed as endangered, vulnerable or extinct on theSchedules of the Threatened Species Conservation Act 1995 and theEnvironment Protection and Biodiversity Conservation Act 1999.

wetland orswamp:

Those areas that are inundated or saturated by surface or groundwater at a frequency and duration sufficient to support, and thatunder normal circumstances do support, a prevalence of flora and

fauna typically adapted for life in saturated soil conditions. Wetlandsgenerally include swamps, marshes, bogs and similar areas.

Year: 1 to 12 months

ecological risk based decision making model

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