ecological risk based decision making model
TRANSCRIPT
7/30/2019 Ecological Risk Based Decision Making Model
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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
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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
rock bars, pools, riffles
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
no rock bars, pools,
riffles 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
ephemeral
rock bars, pools, riffles
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
no rock bars, pools,
riffles 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
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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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
Consequence Attribute Decision
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
Consequence Attribute Decision
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
Consequence Attribute Decision
Stream flow Perennial Duration Permanent
Severity Complete loss
Extent Medium
Total Score
Consequence to Biodiversity – see Consequence Table 1.2
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
Consequence Attribute Decision
Severity Partial loss
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 to Biodiversity – see Consequence Table 1.2
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
Consequence Attribute Decision
Severity Partial loss
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
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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