Emergency Action Plan - data.dnrm.qld.gov.audata.dnrm.qld.gov.au/eap/gordon-road-eap.pdf · Gordon Road Bardon Detention Basin (GRBDB) is located in the suburb of Bardon in Brisbane

Emergency Action Plan

Gordon Road Bardon Detention Basin

Referable Dam ID: # 2608

Version: 1.3

Dam Owner: Brisbane City Council

September 2019

RM Ref: CA18/164487

WIDTJ

Text Box

Approved by the delegate of the Chief Executive, Department of Natural Resources, Mines and Energy until 1 June 2022

CA18/164487 Gordon Road Bardon Detention Basin Emergency Action Plan Page 2 of 71

Emergency Actions – Quick Reference Summary

Dam Hazard and

Document Reference

Activation Stage

Alert Lean Forward Stand Up Stand Down

Decision Authority Flood Officer

Event Response Coordinator

Dam Owner


Dam Owner

Event Response Coordinator Event Response Coordinator

Activation trigger for dam hazards (See section 6)

Dam Crest Flood Failure

See section 6.4

Warning issued by BoM for

rainfall greater than 100mm

and possible flash flooding

WL at or above 72.6 m AHD

and rising.

Further rain is predicted

WL at or above 75 m AHD and

rising.

Evidence of seepage or other

damage to integrity of dam.

WL fallen below dam crest: (76

m AHD) and dropping

predictably

AFC Overtopping Failure

See section 6.5

Warning issued by BoM for

rainfall greater than 100mm

and possible flash flooding

WL at or above 72.6 m AHD

and rising.

Further rain is predicted

WL at or above 75 m AHD and

rising.

Further rain predicted.

WL fallen below dam crest (76

m AHD) and dropping

predictably.

Earthquake

See section 6.6

Earthquake greater than 5.5

Modified Mercalli (MM)

reported

Inspection confirms cracking,

movement or other damage to

integrity of dam and heavy

rainfall event is predicted.

Heavy rain continuing.

Water levels rising and

inspection indicates seepage,

erosion or movement is

substantial

Risk assessment has

determined that failure risk has

reduced

High Energy Impact/

Terrorist Activity

See section 6.7

Impact/activity reported Inspection confirms cracking,

movement or other damage to

integrity of dam and heavy

rainfall event is predicted.

Heavy rain continuing.

Water levels rising and

inspection indicates seepage,

erosion or movement is

substantial

Risk assessment has

determined that failure risk has

reduced


Revision Status

Rev No. Issue Date Revision Description

0.72 March 2018 Original Draft – For review by Council staff and LDMG

1.0 July 2018 Version 1 issued to DDC, LDMG & CEO for endorsement prior to

lodgement with DSR

1.1 August 2018 Amended to ensure consistency with LDMP after consultation with

LDMG and DMO.

1.2 November 2018 Revised after consultation with DNRME re roles and responsibilities

and local government notice by CEO Brisbane City Council.

1.3 September 2019 Updated contact details for key personnel in Appendix C.

1/10/2019


Distribution Control Sheet (Controlled Hard Copies)

Copy Position Organization/Location

1 Manager, Natural Environment Water and

Sustainability (NEWS),

Level 7, Brisbane Square, Brisbane, QLD

4000

2 Unit Manager, Flood Management, City

Projects Office

Level 1, Green Square Close, South Tower,

Fortitude Valley, QLD 4006

3 Manager, Asset Services, Level 10, Brisbane Square, Brisbane, QLD

4000

4 Regional Manager, West Region Regional Business Centre, 681 Fairfield Rd.

Yeerongpilly, QLD 4105

5 Manager, Disaster Management Level 23, Brisbane Square, Brisbane, QLD

4000

6 Coordinator, Disaster Management Level 23, Brisbane Square, Brisbane, QLD

4000

7 Senior Operations Officer, Disaster

Management


4000

8 CEO, Brisbane City Council Level 23, Brisbane Square, Brisbane, QLD

4000

9 Local Disaster Management Group

(LDMG)


4000

10 District Disaster Management Group

(DDMG)

Queensland Police, Brisbane

11 Emergency Management Coordinator Queensland Fire and Emergency Services

12 Dam Safety Regulator Department of Natural Resources Mines and

Energy, George Street, Brisbane, QLD 4000


Common Abbreviations and Definitions

The following abbreviations and definitions are common in EAPs and disaster management documents.

Note: Some Brisbane City Council specific abbreviations and definitions are noted (BCC) in parenthesis.

Other definitions associated with the regulation of referable dams in Queensland are listed in Appendix E.

The Act The Water Supply (Safety and Reliability) Act 2008

AEP Annual Exceedance Probability

AFC The Acceptable flood capacity (of a referable dam)

AHD Australian Height Datum

ANCOLD Australian National Committee on Large Dams

BoM Bureau of Meteorology

BCC Brisbane City Council

CEO Chief Executive Officer (BCC)

CPO City Projects Office (BCC)

DCF Dam crest flood – design flood event which just overtops the crest

DDMG District Disaster Management Group

DDC District Disaster Coordinator

DEWS Former Qld Dep’t of Energy and Water Supply responsible for dam safety – see DNRME

DM Disaster Management (BCC)

DM Act Disaster Management Act 2003

DMDO Disaster Management Duty Officer (BCC)

DMSPF Disaster management strategic policy framework

DNRME Department of Natural Resources, Mines and Energy

DOMM Detailed Operations and Maintenance Manual for a referable dam

DSR Dam Safety Regulator – See Appendix E

EA Emergency Alert messaging service operated by QFES through the SDCC

EER Emergency Event Report

EHSOT Emergency Human Services Operational Team (BCC)

EMAF The emergency management assurance framework

ERC Event Response Coordinator

EWA Early Warning Alert messaging service operated on behalf of BCC

FIC Flood Information Centre – (BCC)

FIS Failure Impact Statement – See also Appendix E

FSL Full supply level

GRBDB Gordon Road Bardon Detention Basin – (BCC)

GS Gauging station

GIS Geographic Information System

IC Incident Controller


LDC Local Disaster Coordinator

LDCC Local Disaster Coordination Centre

LDMG Local Disaster Management Group

LDMP Local Disaster Management Plan

ML Mega litre

m AHD metres elevation above Australian Height Datum

MDM Manager, Disaster Management (BCC)

MNEWS Manager, Natural Environment, Water and Sustainability (BCC)

NEWS Natural Environment, Water and Sustainability Group (BCC)

PAR Population at Risk

PMPDF Maximum realistic design flood resulting from probable maximum precipitation event

PPRR Prevention, preparedness, response and recovery

QDMA Queensland disaster management arrangements

QDSMG Queensland dam safety management guideline

QFCoI Queensland Floods Commission of Inquiry

QFES Queensland Fire and Emergency Services

QPS Queensland Police Service

RL Reduced level (relative to fixed height datum, usually AHD)

RIMTs Regional Incident Management Teams

RPEQ A Registered Professional Engineer. Queensland

SDCC State Disaster Coordination Centre

SDMG State Disaster Management Group

SES State Emergency Service

SITREP Situation Reports

SOP Standing Operating Procedure

IGEM The Office of the Inspector-General Emergency Management

Notes:

Source: Department of Natural Resources, Mines and Energy Emergency Action Plan for Referable Dam Guideline 2017

BCC specific references annotated (BCC)

Some additional definitions applicable to the licence are included with a copy of the licence conditions in Appendix F


Table of Contents

Emergency Actions – Quick Reference Summary ........................................................................................ 2

Approval and Authorisation ........................................................................... Error! Bookmark not defined.

Revision Status .............................................................................................................................................. 3

Distribution Control Sheet (Controlled Hard Copies) ..................................................................................... 4

Common Abbreviations and Definitions ........................................................................................................ 5

Table of Contents .......................................................................................................................................... 7

List of Appendices ......................................................................................................................................... 8

List of Tables ................................................................................................................................................. 9

List of Figures ................................................................................................................................................ 9

1.0 Dam Information .............................................................................................................................. 10

1.1 Introduction .................................................................................................................................. 10

1.2 Development of an Emergency Action Plan ................................................................................ 10

1.3 Objective of the Emergency Action Plan ..................................................................................... 11

1.4 Updating the Emergency Action Plan .......................................................................................... 11

1.5 DNRME Referable Dam Data Summary Sheet ........................................................................... 11

1.6 Dam Location, Access and Evacuation Routes .......................................................................... 12

2.0 Gordon Road Bardon Detention Basin – Performance and Operation ........................................... 14

2.1 Design and As-Constructed Dam Performance Data .................................................................. 14

2.2 Dam Inflow/Outflow and Water Levels for Design Flood Events ................................................. 15

2.3 Storage-Discharge Details ........................................................................................................... 16

3.0 Dam Safety Management ................................................................................................................ 19

3.1 The Emergency Management Framework .................................................................................. 19

3.2 Maintenance and Management of the Detention Basin .............................................................. 19

3.3 Water Level Measurement and Rainfall Records ........................................................................ 19

3.4 Emergency Events ....................................................................................................................... 20

3.5 Relationship to Other Plans ......................................................................................................... 20

4.0 Key Roles and Responsibilities ....................................................................................................... 21

5.0 Warning and Communication Plan .................................................................................................. 24

5.1 Purpose of the Communication Plan ........................................................................................... 24

5.2 Limitations Associated with PAR Notifications ............................................................................ 24

5.3 Notification to External Agencies ................................................................................................. 24

5.4 Notification to Population at Risk (PAR) ...................................................................................... 24

6.0 Assessment of Dam Hazards and Emergency Situations ............................................................... 29

6.1 Dam Hazards ............................................................................................................................... 29

6.2 Gordon Road Bardon Detention Basin – Failure Impact Assessment (FIA) ............................... 29

6.3 Possible Flood–related Failure Mechanisms Considered for the Gordon Road Detention Basin29


6.3.1 Sudden Collapse Due to Seepage Under the Basin ............................................................... 30

6.3.2 Erosion and Undermining of the Foundation ........................................................................... 30

6.3.3 Cracking and Development of Uncontrolled Seepage ............................................................ 30

6.4 Situation 1 – Dam Crest Flood (1 in 50 AEP) with Structural Failure .......................................... 30

6.5 Situation 2 -- Dam Crest Overtopping With Structural Failure ..................................................... 36

6.6 Situation 3 - Damage to the Basin as a Result of Earthquake .................................................... 41

6.7 Situation 4 – Terrorist or High Energy Impact ............................................................................. 41

7.0 Activation of the EAP ....................................................................................................................... 42

7.1 Emergency Management to Identify and Minimise Risk ............................................................. 42

7.2 Stages of Emergency Services Activation ................................................................................... 42

7.3 Initiation of an Emergency ........................................................................................................... 43

7.4 Notifications on Activation of the EAP ......................................................................................... 44

7.5 Emergency Situation - Alert Triggers ........................................................................................... 44

7.6 Pre-approved Wording of the Agreed Notification and Warning Messages ................................ 47

8.0 Emergency Event Report (EER) ...................................................................................................... 48

9.0 Dam Event Public Warning and Education Protocol ....................................................................... 49

9.1 Public Education .......................................................................................................................... 49

9.2 Staff Training and Exercises ........................................................................................................ 49

List of Appendices

APPENDIX A – Population at Risk and Inundation Mapping ...................................................................... 50

APPENDIX B – Summary of EAP Activation and Alert Triggers ................................................................. 57

APPENDIX C – Contact Lists for PAR and Key Council Officers ............................................................... 58

APPENDIX D – Modified Mercalli Earthquake Intensity Scale – Damage Guide ....................................... 62

APPENDIX E - Definitions/Glossary ............................................................................................................ 63

APPENDIX F – DNRME License Conditions .............................................................................................. 66

APPENDIX G – DRAWINGS - Gordon Road Bardon Detention Basin – General Layout .......................... 69

APPENDIX H – Reference Documents ....................................................................................................... 71


List of Tables

Table 1 – DNRME Referable Dam Data Summary Sheet .......................................................................... 11

Table 2 - BCC Dam Design and As-constructed Data Summary ................................................................ 14

Table 3 - Stage/Storage and Discharge Data for the Gordon Road Bardon Detention Basin .................... 16

Table 4 – Inflow / Outflow and Dam Water Levels for Design Floods, Including Extreme Event ............... 17

Table 5 – Key Roles and General Responsibilities ..................................................................................... 21

Table 6 – Contact Details for Notification of Relevant External Agencies ................................................... 27

Table 7 - Situation 1 – Dam Crest Flood EAP Response (Possible Structural Failure) .............................. 32

Table 8 - Situation 2 – Dam Crest Overtopping EAP Response ................................................................. 37

Table 9 – EAP Escalation Levels ................................................................................................................ 43

Table 10 – Summary of Pre-approved Emergency Communication Messaging to the PAR ...................... 47

List of Figures

Figure 1 – Location Map .............................................................................................................................. 13

Figure 2 – Gordon Road Detention Basin Catchment ................................................................................. 13

Figure 3 – Gordon Road Detention Basin Stage – Storage Curve ............................................................. 18

Figure 4 – Gordon Road Detention Basin Stage – Discharge Relationship ............................................... 18

Figure 5 – Agreed Internal and External Communication Flow ................................................................... 26

Figure 6 – Inflow, Outflow and Peak Water Levels in GRBDB for 1 in 50 AEP Event ................................ 45

Figure 7 – Catchment Rainfall and Peak Water Levels in GRBDB for 1 in 50 AEP Event. ........................ 45

Figure 8 – Gordon Road Bardon Detention Basin - Emergency Situation Alert Triggers ........................... 46

Figure 9 – Dam Event Public Warning and Notification Protocol ................................................................ 49


1.0 Dam Information

1.1 Introduction

Gordon Road Bardon Detention Basin (GRBDB) is located in the suburb of Bardon in Brisbane. The original

structure consisted of an earth-fill embankment with a large culvert opening through the main embankment

of the basin, which permitted floodwater to flow downstream through a defined open earth channel. The

open channel finishes upstream of 54 Gordon Road where it drains into an 1800 mm diameter circular

culvert near the properties at risk.

The basin was reconstructed in 2017/2018 to provide enhanced stormwater detention and flood mitigation

functions. The newly re-constructed detention basin includes works of raising the crest level and reducing

the size of its outlet to restrict outflow so it matches the capacity of the downstream stormwater pipe. Figure

1 shows the location of the basin and Figure 2 the contributing catchment.

The basin is to be kept safe, and be maintained and operated in accordance with the attached Dam Safety

Schedule and current versions of the following guidelines issued in Queensland under the Water Supply

(Safety and Reliability) Act 2008 and the Water Legislation (Dam Safety) Amendment Act 2017, including:

• Queensland Dam Safety Management Guidelines

• Guidelines for Failure Impact Assessment (FIA) of Water Dams

• Guidelines on Acceptable Flood Capacity (AFC) for Dams

The current Dam Safety Regulator in the State of Queensland is the Chief Executive, Department of

Natural Resources, Mines and Energy (DNRME) or the Department’s Delegate Officers.

1.2 Development of an Emergency Action Plan

The approved FIA has been carried out based on the design of the enhanced GRBDB under the provisions

of the Water Supply (Safety and Reliability) Act 2008.

The FIA identified the GRBDB as a Category -1 Referable Dam (2 or more persons at risk).

DNRME has issued a licence and a set of draft licence conditions based on their assessment of the FIA and

classified the basin as a referable dam.

Further information on guidelines associated with these dams are available in the website

www.dnrme.qld.gov.au.

Both the Act and the licence conditions issued pursuant to the Act require the dam owner (BCC) to develop

an EAP and have that plan endorsed and approved by the Dam Safety Regulator.

The EAP is a tool for the dam owner, relevant disaster management groups, local government and

emergency management agencies to effectively coordinate the management of risk and consequences of

a dam hazard /emergency event.

In preparing the EAP, the following has been considered:

• Identification of dam hazard, hazard events and dam emergency events;

• Identification of people who may be affected/harmed as a result of dam hazard;

• State processes to be followed to minimise risk of harm to people/property if such an event happens;

• Identification of relevant entities, roles and responsibilities of all parties during planning, activation

and testing for an event;

• Identification of who (in priority order), when and how the notification and warning messages are to

be delivered to persons who may be at risk and whose properties are at risk;

• The types of notification/messages to be delivered and who will deliver those;

• Ensure training is provided to the staff and relevant officer involved in handling EAP;

• Testing the effectiveness of the EAP in an exercise.

http://www.dnrme.qld.gov.au/


1.3 Objective of the Emergency Action Plan

This document is intended to guide responsible personnel through identifying and responding to hazardous

conditions associated with the Gordon Road Detention Basin. Emergencies are dynamic events which

evolve rapidly, usually under adverse weather conditions, and this plan does not cover all possible

combinations of events.

Emergency response personnel should maintain situational awareness at all times, and exercise their best

judgment in their response. The safety of the public and all emergency response personnel should not be

compromised in implementing this plan.

1.4 Updating the Emergency Action Plan

The Emergency Action Plan (EAP) will be reviewed for adequacy every five years or alternate timeframe as

advised in writing from the Department of Natural Resources Mines and Energy.

Telephone contact details will be updated annually or as required with changes to State and Local

Government contact details.

Following any update to the Plan, it will be distributed as per the Distribution Control Sheet.

1.5 DNRME Referable Dam Data Summary Sheet

Note: The following summary information is provided in accordance with the dam licence conditions. It is

based on design drawings submitted with the Failure Impact Statement for assessment by the Dam Safety

Regulator. A copy of the licence conditions is included in Appendix F.

Table 1 – DNRME Referable Dam Data Summary Sheet

Category Assessment

Dam Name Gordon Road Bardon Detention Basin

Referable Dam ID: #2608

Failure Impact Rating 1

Population at Risk1 (PAR) 34.8 ( DCF - 1 in 50 AEP Flood Failure)

Date Assessment accepted 18 May 2017

Hazard Category (ANCOLD) High C1

Acceptable Flood Capacity (AFC): 1 in 34,800 AEP

Current Dam Crest Flood Capacity (DCF): 1 in 50 AEP

Timing of Minimum AFC Upgrade/s: N/A

Location

Coordinates 27°27’31.53” S, 152°57’58.96” E

Property description (Primary Location) Lot 1324 S31983

Lot 699 S31294

Lot 701 S31294

1 For the purposes of this EAP, PAR is the total population at risk if a dam failure event was to occur, including transient populations as well as those at residences and businesses.


Category Assessment

Lot 12 RP45087

Local Authority Brisbane City Council

Basic Characteristics of the Dam

Purpose Flood Detention

Embankment

Construction Type Reinforced concrete wall with rock protection facing

Total Length 70 m

Maximum Embankment Height 4.8 m

Storage Capacity 17.7 ML

Surface Area 1.1 Ha

Catchment area 51.1 Ha

Full Supply Level No permanent storage available

Dam Crest Level 76.0 m AHD

Spillway

Description Nil

Control level -

Discharge Capacity 7.3 m3/s (1.2 m x 1.2 m box culvert at toe – Invert

Level ; 71.38 m AHD)

1 High C – This Consequence Category is based on the maximum PAR of 34.8 estimated in the Gordon

Road Bardon Detention Basin Failure Impact Assessment dated 28 February 2017 and utilising the Minor

to Medium ‘Severity of Damage and Loss’ in accordance with DNRME Guidelines on Acceptable Flood

Capacity for Water Dams dated August 2016.

1.6 Dam Location, Access and Evacuation Routes

General access to the Gordon Road Detention Basin is via the unsealed service track at the western end of

Gordon Road. The access track is unsealed and potentially unusable in wet weather. It is deemed unsafe

to try to access the dam during a flood event.

Gordon Road is accessed from Simpson’s Road, Bardon. Local roads in this area are winding and flood

prone, with a high likelihood that residents would be cut off and isolated by road closures at many locations.

It is therefore likely that an event large enough to trigger a Level 3 activation of the EAP will be sufficient to

ensure the community is isolated by local floodwater for a couple of hours until floodwaters recede.

Due to the short response time between the start of rainfall and the onset of flooding sufficient to trigger a

Level 2 alert, access to the dam and evacuations of the Population at Risk downstream of the dam will not

be possible. The population at risk (PAR) will therefore need to be flood resilient and remain in place until

after a flooding event is over.

The only viable means of evacuation for the PAR will be to evacuate to a safe refuge in place, at least 1.2

m above the floor.

This means taking refuge in a safe place in a flood proof structure (house) above the highest possible flood

level.


Figure 1 – Location Map

Figure 2 – Gordon Road Detention Basin Catchment


2.0 Gordon Road Bardon Detention Basin – Performance and Operation

2.1 Design and As-Constructed Dam Performance Data

The following data has been compiled from surveyed as-constructed details and may differ slightly from the

data sheet details held by DNRME which was based on the preliminary design data.

Table 2 - BCC Dam Design and As-constructed Data Summary

Description Data

Name of Dam Gordon Road Bardon Detention Basin

Location UBD Ref: 158/G6

Lat: 27.450 S; Long: 152.970 E

Lot on plan Lot 1324 on S31983

Referable Dam Register No: #2608

Dam Owner Manager, Natural Environment Water and Sustainability

(NEWS), Brisbane City Council

Owners Contact number 07 3403 8888

Owners Site Contact No site based personnel.

Emergency Contact Name Regional Manager, West

Emergency contact Regional Business Centre,

Ground level, 681, Fairfield Road

Yeerongpilly

07 3403 8888

Watercourse: Tributary of Ithaca Creek

Original construction Circa 1980

Construction upgrade completed 25 January 2018

Type of dam Reinforced concrete cantilever wall with rock armouring and

gabion protection of downstream watercourse.

Purpose of dam Urban stormwater detention basin

Dam height 4.8m

Width of dam crest 3.5m

Side slopes 2H : 1V (both US and DS faces are rock protected)

Dam length at crest 70m (Approximately)

Dam crest level 76.0 m AHD

Full supply level (FSL) No permanent storage available.

Storage capacity at dam crest level 18.7 ML

Surface area at dam crest level 0.75 Ha

Spillway type and width

Design width of crest-overtopping

Dam Overflow (at 76.00 m AHD crest level),

Approximately 40m


Description Data

Outlet works: 1.2m wide x 1.2m high RCBC

Outlet works: U/S & D/S invert levels 71.38 & 71.03 m AHD – culvert barrel length 19.2 m

Discharge capacity 7.3 m3/s at 76m AHD (in 1 in 50 AEP flood)

Dam Crest Flood 1 in 50 AEP flood

Acceptable Flood Capacity 1 in 34800 AEP flood

Catchment area (contributing) Approx. 52 Ha

PMF Design Flood Approx. 62 m3/s

Population at risk (PAR) Approx. 35

2.2 Dam Inflow/Outflow and Water Levels for Design Flood Events

Gordon Road Detention Basin is located on a tributary of Ithaca Creek, in the greater catchment of Breakfast

Creek. The contributing catchment area is approximately 52 hectares. Discharge from the basin is through

a reinforced concrete box culvert of 1200mm x 1200mm at the toe of the basin wall. The culvert upstream

and downstream invert levels are 71.38 and 71.03 m AHD. The length of the discharge culvert is 19.2 m.

Maximum culvert discharge capacity is approximately 7.3 m3/s with basin water level at the dam crest level

of 76m AHD. Storage capacity of the basin at dam crest level is 18.7 ML.

During detailed design, ARUP (2015) assessed the Acceptable Flood Capacity of the basin using a

TUFLOW-2D hydraulic model of the proposed upgrade. A 2m model grid was adopted extending from the

basin to the residential development downstream. Hydrological information regarding design inflow data

was obtained from the WBNM hydrology model developed by Council.

As designed, the upgraded basin can hold runoff up to a 1 in 50 (2%) AEP event. The critical storm duration

is 60minutes (102mm of rainfall in an hour) and a Dam Crest Flood results from this event. Design flood

events rarer than a 1 in 50 AEP event would overtop the dam crest.

The Acceptable Flood Capacity event was identified as the 1 in 34800 AEP flood event. This event would

result in a flood level of approximately 76.58 m AHD and was used as the extreme event for design of the

detention basin wall.

Inflow and outflow hydrographs for the detention basin, including water level variation with time for a wide

range of design flood events are included in the Dam Data Book.

The inflow and outflow hydrograph for the 1 in 50 AEP event is reported in Figure 6.


2.3 Storage-Discharge Details

A stage-storage plot for GRBDB is presented in Figure 3. Stage-storage and spillway discharge data is

included in Table 3 and dam characteristics against various AEP events in Table 4.

Table 3 - Stage/Storage and Discharge Data for the Gordon Road Bardon Detention Basin

Dam Level Basin Storage Discharge Comments

(m AHD) (m3) (m3/s)

71.38 28 0.0 Outlet culvert-invert

71.50 50 0.1

71.75 205 0.5

72.00 409 1.0

72.25 843 1.7

72.50 1277 2.4

72.75 1949 3.1 LEAN FORWARD – Trigger Level 1

Outlet culvert running full 1 in 10

AEP

73.00 2621 3.6

73.25 3488 4.2

73.50 4355 4.7

73.75 5466 5.2

74.00 6576 5.6

74.25 7848 5.9

74.50 9120 6.2

74.75 10529 6.5

75.00 11938 6.8 STAND UP - Trigger Level 2

1 m below Dam Crest –

75.25 13523 7.1

75.50 15108 7.3 See Note:

75.75 16936 7.6*

76.00 18764 7.9* Basin wall crest – 1 in 50 AEP flood

76.25 20773 16.2 1 in 200 AEP flood

76.35 21577 21.9 STAND UP – Trigger Level 3

1 in 500 AEP flood

76.40 21980 25.3 1 in 1000 AEP flood level

76.46 22460 31.0 1 in 2000 AEP flood level

76.50 22783 31.0 Water level above design flood

76.58 22783 36.9 1 in 34,800 AEP flood

76.75 24965 50.2

76.88 Approx. 26000 62.1 PMF

77.00 27147 72.9 Water level above PMF

Note: * Outflows above 7.3 m3/s are pressurised culvert flows with no allowance for blockage.


Table 4 – Inflow / Outflow and Dam Water Levels for Design Floods, Including Extreme Event Event

ARI

Event

AEP

Rainfall

Depth

(WBNM)

Peak Inflow

Peak

Outflow

Peak

Water

Level

Time to

peak

(Years)

(Critical storm

duration

minutes)

(%) (mm) (m3/s) (m3/s) (m AHD) (minutes)

20 (90min) 5 62 11.2 7.1 75.25 86

50 (60min) 2 102 14.4 7.3 75.97 74

100 (60min) 1 113 17.1 12.7 76.15 60

200 (60min) 0.5 130 19.7 16.5 76.25 58

500 (60min) 0.2 150 23.9 21.9 76.35 50

1000

(60min)

0.1 165 26.9 25.3 76.4 49

2000

(60min)

0.05 180 30.1 28.9 76.46 47

34800

(60min)

2.87x10-3 243 37.2 36.9 76.58 45

PMF

(60min)

1x10-5

380 62.1 62 76.88 40

The AFC event was identified as the 1 in 34,800 AEP flood event. This event would result in a flood level of

approximately 76.6 m AHD and was used as the dam overtopping flood event to assess failure impacts

downstream.

A plot of the spillway-rating curve is shown in Figure 4.


Figure 3 – Gordon Road Detention Basin Stage – Storage Curve

Figure 4 – Gordon Road Detention Basin Stage – Discharge Relationship

70

71

72

73

74

75

76

77

78

79

80

81

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0

m A

HD

Storage-ML

Gordon Road Basin- Storage/Elevation Plot

Storage-elevation

70

71

72

73

74

75

76

77

78

79

0.00 10.00 20.00 30.00 40.00 50.00 60.00 70.00 80.00 90.00 100.00

Ba

sin

Ele

va

tio

n -

m A

HD

Culvert Discharge and Overflow - m3/s

Gordon Road Basin-Rating Curve


3.0 Dam Safety Management

3.1 The Emergency Management Framework

This Emergency Action Plan (EAP) is a tool used to define the communication protocols and procedures

that should be followed to manage incidents in the Gordon Road, Bardon Detention Basin catchment.

Very heavy rainfall and extensive flooding can occur in the catchment of Ithaca and Breakfast Creek

resulting in significant stream rises and flash flooding in the upper reaches of the creek systems. When such

flood emergency develops that affects the Gordon Road Detention Basin, close co-operation needs to be

maintained with the Local Disaster Management Group.

The Detention Basin does not overtop until the rainfall event equates to a 1 in 50 (2%) AEP event, a very

major event. When that happens, the Local Disaster Management Group and emergency management

personnel may already be activated with flooding all over the area. A failure in the dam embankment will

surcharge those flood levels, potentially worsening the flooding downstream to the junction of Ithaca Creek.

Modelling associated with the preparation of the Dam Failure Impact Analysis shows that for a flood up to a

1 in 500 AEP magnitude (approx. 350 mm above the Dam Crest Flood), while there will be downstream

flood impacts, the PAR identified in the worst case dam failure modelling will not be at risk. At this water

level, the discharge is well within the structural safety limits allowed for in design and no failure of the

structure is anticipated.

Nevertheless, assuming is possible, Council considers that water levels rising within 1 m of overtopping the

Dam Crest will require Stand Up status. The 1 in 500 AEP (i.e. 76.35 m AHD) water level is considered to

be the trigger level for taking action to issue automated EA messaging to PAR as described in this EAP.

The 52 Ha creek catchment above the detention basin is relatively steep, and so the time for the Local

Disaster Management Group and emergency management personnel to react will be short – less than an

hour. This coupled with the lack of safe evacuation routes will make responding to an emergency event

associated with the basin a challenge for all emergency personnel.

3.2 Maintenance and Management of the Detention Basin

Gordon Road Bardon Detention Basin (GRBDB) is owned by Council and the responsible officer is the

Manager, NEWS.

Day-to-day management of the Basin is carried out under the overall responsibility of the Dam Asset

Manager (Regional Manager West).

Regular inspections and asset maintenance is carried out by the Dam Asset Manager as required, in

accordance with the GRBDB Asset Maintenance and Management Plan (Detailed Operating and

Maintenance Manual).

The Asset Maintenance and Management Plan (Detailed Operating and Maintenance Manual) of the

GRBDB sets out procedures to follow and provides guidance on actions required to maintain the basin

ensuring the operation of the basin is in accordance with the design parameters and the licence conditions.

3.3 Water Level Measurement and Rainfall Records

To assist with the monitoring and alerting requirements of managing the basin, a stream height gauge is

located near the right bank of the basin wall (looking downstream) which is connected to Council’s telemetry

network. This gauge provides continuous 24 hour-7days per week monitoring of water levels in the basin to

enable automatic alert messaging to the PAR.

There are two ALERT rainfall gauges in close proximity to the basin providing continuous live reporting of

nearby catchment rainfall to Council’s telemetry network.


• The nearest gauge (I_R512) is located 2km south-west of the basin wall in the suburb of Mount

Coot-tha in the Ithaca Creek catchment;

• The second gauge (TWR 279) is located 2.73 km south-east of the basin wall in the Toowong

Creek catchment.

Both gauges have a 1 mm resolution and report instantaneously. Rainfall accumulations are monitored

continuously in Council’s FloodWise Information System. Because of the short catchment response time

between rainfall and the onset of flooding, a series of automatic alerting protocols have been set up to

enable notifications to the PAR in accordance with this EAP. The automatic rainfall and water level alert

triggers and messaging are summarised in Table 10.

A limitation with this system is that there may be a slight delay of up to five to ten minutes for the system to

update the latest rainfall data. Any alerts to the PAR need to take this delay into account.

3.4 Emergency Events

The flood hazards resulting from the release of water via the dam spillway and/or controlled release from

the low flow culvert is managed by Council under normal daily operations in response to flooding incidents

and by on-call personnel after hours.

The emergency events catered for in this document include:

• dam crest flood breach failure (1 in 50 AEP event) inundation downstream of the detention basin;

and,

• dam overtopping collapse associated with the acceptable flood capacity event (1 in 34,800 AEP

event).

Other non-flooding related conditions which may influence the safety of the basin are covered in Section 6.

3.5 Relationship to Other Plans

This plan is subordinate to the Brisbane District Disaster Management Plan.

Information presented here is intended to assist with the management of a flooding emergency in the

catchment of Gordon Road and the upper reaches of Ithaca Creek that may be affected by the condition of

the Gordon Road Detention Basin.


4.0 Key Roles and Responsibilities

In managing a dam hazard event, close collaboration between the Dam Owner and internal as well as

external stakeholders is required. All parties who have a role in the implementation of the EAP are required

to agree on their respective roles and responsibilities.

Table 5 lists the personnel and agencies which have designated roles and responsibilities in the

implementation and management of the EAP response. Notification arrangements and contact details for

external agencies are discussed in Section 5 and contact details for key Council officers provided in

Appendix C2.

Table 5 – Key Roles and General Responsibilities

Role/Position EAP Dam Release Hazard Responsibility

EAP Non-emergency Response Planning and Non-urgent Responsibility

Dam Owner

(Manager NEWS)

Notify priority stakeholders about the

situation.

Respond in accordance with the approved

EAP in all dam relevant incidents.

Activate the EAP and maintain an incident

log (including visual inspection of the dam

and any notifications that have been

made).

Provide timely and accurate notifications

to all relevant parties mentioned in the

notification list in a relevant dam hazard

event or emergency event.

Report all incidents and failures in writing

to the chief executive within forty-eight

(48) hours of becoming aware of the

incident or failure.

Prepare Emergency Event Report (EER)

and submit to the chief executive within 30

business days after the end of the

emergency event.

Develop an emergency action plan in

consultation and collaboration with local

government and disaster management group/s

who may be affected by a dam hazard identified

in the plan.

Provide a copy of the EAP to each disaster

management group who may be affected by a

dam hazard identified in the plan.

Submit the EAP to the chief executive for

assessment.

Maintain and update documents annually

(before 1 October each year)

Distribute current approved EAP to all parties

listed in the distribution list.

Ensure adequate funds and resources available

to manage the dam.

Ensure the Population at Risk (PAR) have an

appropriate evacuation plan in the event of a

dam failure.

Ensure the Population at Risk (PAR) have an

understanding of the purpose of the warning

and notifications in the event of a dam

emergency or dam hazard.

Ensure appropriate training for all personnel

with responsibilities under the EAP.

Undertake periodic testing of EAP to ensure

telephone numbers are correct and the

notification priority list is logical. Make

appropriate dam safety related decisions based

on advice from a consulting engineer where

appropriate.

Authorise any immediate expenditure so that

urgent repair work will not be delayed.

The dam owner is responsible for conducting a

safety evaluation of the dam and to identify any

deficiency in the dam’s safety. Where

deficiencies exist, the dam owner is required to

take appropriate steps to minimise the potential

risk of dam failure from these deficiencies.




Dam Asset Manager

(Regional Manager,

West)

Undertake inspections in response to developing dam hazard event.

Coordinate relevant repairs if time permits and if safe to do so.

Monitor events on site when safe to do so.

Coordinate day-to-day asset management functions including inspections, maintenance and repairs to ensure dam is safe and fit for purpose

Event Response

Coordinator

(Depending of the scale

and phase of the event

this role is filled by:

• Disaster

Management Duty

Officer;

• Manager, Disaster

Management; or

Incident Controller, Local

Disaster Coordination

Centre)

Coordinate Council’s response to the hazard event.

Review the emergency information received and advise the LDMG of the developing hazard situation.

Issue Alert/advice to the emergency response groups and requirements for mobilisation of emergency resources and actions.

Liaise with the Dam Owner in implementing EAP actions and the local disaster management plan and check the requirements

Issue Emergency Alert messages via the SDCC Watch Desk

Mobilise and convene the Local Disaster Management Group (LDMG) and assign resources required to manage the event

Mobilise disaster response from internal and external organisations in accordance with the Qld Disaster Management Arrangements.

Mobilise State assistance if the situation escalates beyond control of local community.

Establish LDCC and organise resources.

Organise LDMG and manage functions.

Maintain a log of all communications and data records

Ensure that the GRBDB EAP has been prepared in consultation with other response agencies and is in accordance with the Qld. Disaster Management Guidelines.

Flood Officer

(FIC Duty or Technical

Officer)

Monitor BoM weather forecasts, flood warnings, recorded rainfall and dam water levels

Advise Dam Owner and Event Response Coordinator (ERC) of the developing hazard conditions

In case of a developing emergency event, Identify the trigger levels and follow up on the automated FloodWise alerts to Dam owner or representative

Update the Dam Owner and ERC as required

Maintain a log of all communications and data records

Monitor BoM weather forecasts, warnings, Flood-wise gauge readings and dam water level readings

Be aware of and report to ERC any emerging situation that could trigger a dam emergency event.

Corporate

Communication

(Duty Officer)

Liaison with relevant emergency management entities including LDMG

Follow up with repeat public messaging in authorised media channels and on social media.

Assist Dam Owner with Public Education and Awareness communication

Ensure a high level of participation in Council’s OPT-IN messaging service.




Local Disaster

Coordinator (LDC)

(BCC Chief Executive

Officer)

Exercise Delegated Responsibility in case of an emergency event related to the dam as per the Qld. Disaster Management Act.

Exercise primary responsibility for disaster management with in boundaries as per the Queensland Disaster Management Act

Contact Centre Receives calls coming into Brisbane City Council via the Contact Centre

Works with Contact Centre team and the Corporate Communication Team to update scripting on the situation

Receives calls coming into Brisbane City Council via the 24 hour Contact Centre

Field Services Disaster

Response Officer

Coordinate Field Services resourcing e.g. water over road signs, road closure signs and earthmoving equipment as required

Activate Regional Incident Management Teams as required

Coordination of Field Services resources to support disaster operations

Brisbane Metropolitan

Transport

Management Centre

Advise Translink about potential impacts to public transport

Liaise with the FIC and DM on potential and actual road closures

24 hour monitoring and reporting of incidents on the road network.

Advise Translink about potential impacts to public transport

LDMG Set priorities for the LDCC Provide input/feedback on the EAP

SDCC

Coordination of state level operational response during disaster operations

Issue authorised preconfigured Emergency Alert Warnings in accordance with the EAP

Maintain a 24/7 watch desk

QLD Police Initiate appropriate emergency actions to protect PAR

First response and initial evacuation

Public safety

QFES Coordinate swift water rescue if required

Carry out general rescue and recovery, including confined space rescue and recovery in the event of structural collapse of buildings, bridges, etc.

Public safety

DNRME

Dam Safety Regulator

Liaise with SDCC re dam safety emergency requirements

Administer Dam safety licencing & regulations.

Review and approve EAPs.


5.0 Warning and Communication Plan

5.1 Purpose of the Communication Plan

There are high community expectations that all dam owners will provide timely warnings and notifications

of a dam hazard event or emergency event. For this reason, the Act requires the Dam Owner to state within

the EAP when and how PAR and relevant entities (internal and external) will be contacted in the event of a

dam emergency (including priority order).

Possible hazards identified with GRBDB which may require notifications and warning are outlined in more

detail in Section 6.

The purpose of emergency warnings is to inform the PAR of an impending or current threat and promote an

appropriate responsive action.

Depending on the location of the dam and the number of PAR that may need to be notified of warning it

may be appropriate that the warning is issued via a personalised phone call or personal visit.

5.2 Limitations Associated with PAR Notifications

The primary purpose of issuing public notifications during an emergency event is to enable a suitable, safe

and timely action from the PAR.

It has already been identified that the rainfall event likely to cause water levels to rise above the nominated

trigger levels will be greater than a 1 in 20 AEP rainfall event. During such events, access to local roads and

to the PAR will be severely constrained and the safest action may well be to “shelter in place” because safe

evacuations may not be possible. Messaging to the PAR has been carefully constructed around this central

idea.

Note: In the event of forecasted intense storm events, it may not be possible to tell when or where the

rain will fall until it starts to rain. As the response time of the catchment is so short, the time to issue

warnings is limited and it is essential that the alerting procedure be highly automated.

Notwithstanding the time constraints on issuing warnings, provision exists for early alerts to be activated

based on rainfall and rate-of-rise triggers.

In managing a dam hazard event in accordance with the response protocols identified, the safety of

emergency services personnel is of paramount importance.

5.3 Notification to External Agencies

The communications flow chart as given in Figure 5 describes the agreed information flow surrounding the

management of a dam hazard or hazard event. This flow chart has been developed in consultation with

other internal units and external agencies.

Note that due to the rapid response of the catchment, a dam hazard event may develop a short period after

the commencement of rainfall in the catchment. For this reason, many of the actions listed on the flow chart

will need to occur concurrently.

Contact details and notification requirements for relevant external agencies and roles associated with the

implementation of the EAP are provided in Table 6.

5.4 Notification to Population at Risk (PAR)

The Dam Owner is responsible for the continuous monitoring of the status of the dam in accordance with

the EAP, and provision of timely and accurate notifications to all relevant parties in the event of an

emergency event at GRBDB.

Modes of communication may include:


• Personalised calls or door knocks if practical and appropriate;

• Mass notification and warning messages via voice messages to land lines and SMS to mobile

phones. Dam owners are required to prepare and submit polygons and pre-formatted wording to

the State Disaster Coordination Centre (SDCC);

• Media news coverage (i.e. radio and television), if time permits;

• Social media (i.e. websites, Facebook, Twitter);

• Sirens or other direct means.

The PAR is encouraged to register to receive notifications by phone (landline or mobile) or by SMS

via the Brisbane City Council Early Warning Alert (EWA) Service.

Note: During extreme rainfall situations, severe degradation of mobile phone and SMS services

may be experienced. Fostering an aware, self-reliant community is desirable to ensure

maximum effectiveness and safety.

If time permits, targeted telephone-based emergency warnings may be issued to the PAR within the

geographical area likely to be affected via the national Emergency Alert (EA) system.

The area likely to be affected by the possible emergency event is shown in Appendix A, Figure A-6. This

area was determined to be the area covered by the PMF dam failure flood outline expanded to the nearest

road crest.

Contact details for potentially impacted downstream properties are listed in Appendix C1.


Figure 5 – Agreed Internal and External Communication Flow


Table 6 – Contact Details for Notification of Relevant External Agencies

Person/Agency Name Contact Details Notification Requirement

(What this role needs to know)

Contact

priority

Contacted by

Local Disaster

Management

Group

Coordinated through Disaster Management

Manager Disaster Management

Disaster Management Duty Officer

LEAN FORWARD: Confirmation of a decision to activate the EAP

STAND UP: Advice on the severity of the situation and the likely

response required

1 Event Response

Coordinator

District Disaster

Management

Group /

Queensland

Police Service

District Disaster Management Group

Executive Officer

LEAN FORWARD: Advice on the severity of the event and status

of the dam.

STAND UP: Advice on the severity of the situation and the need

for a response including the likelihood of the need for evacuations

2 Event Response

Coordinator

Queensland Fire

and Emergency

Services (QFES)

Emergency

Management

Coordinator

Contact via SDCC

Watch Desk

STAND UP: Advice on the severity of the situation and the

likelihood of the need for rescue and swift water rescue

STAND DOWN: Request recovery operations if necessary

3 Event Response

Coordinator

SDCC Watch Desk Duty Officer 24 hours

LEAN FORWARD: Advise the EAP has been activated

Notify Emergency Management Coordinator

STAND UP: Request issue of pre-approved emergency

notices/warnings via sms and voice messaging to downstream

residents

4 Event Response

Coordinator


Brisbane Metropolitan Transport Management Centre (BMTMC)

Shift Leader/

Duty Officer

STAND UP: Advice on the situation and request that all

notification services are utilised to advise the public of impacts to

the road network

5 Event Response

Coordinator

Dam Safety Regulator (DSR), DNRME

STAND UP: Advice of details of activation of EAP to ‘Stand-up’

level of activation.

Informed of any changes in dam status as emergency situation

develops.

Notify any incidents or failures in accordance with safety conditions

applied to the dam.

6 Dam Owner


6.0 Assessment of Dam Hazards and Emergency Situations

6.1 Dam Hazards

For the purpose of this document:

Dam Hazards as defined by the Water Supply (Safety and Reliability) Act 2008 include hazard situations

arising from either the controlled release of water from the dam, or failure of the dam, where failure includes

collapse of the dam and/or the uncontrolled release of water from the dam.

An uncontrolled release from the Dam (Basin) can be associated with natural flooding and caused by

water that has flowed naturally into the Dam (Basin), filling it and making it overflow. An uncontrolled release

need not be associated with a failure of the Dam (Basin) structure.

A Dam (Basin) structural failure/collapse is associated with an uncontrolled release of water from the

Dam caused by a failure of the Dam structure. In such an event, the flood impacts downstream of the Dam

(Basin) may be worsened by the natural flooding.

A Sunny Day Failure of the Dam (Basin) structure is one that occurs when no natural flooding is occurring.

Emergency Events as defined by the Water Supply (Safety and Reliability) Act 2008 include any event

where persons or property may be harmed because of the event and a coordinated response involving 2 or

more relevant entities are likely to be required. For the purpose of this EAP an emergency event is taken to

be when the operational state of LEAN FORWARD is reached based on the triggers defined in this EAP.

Dam Safety Emergency Event triggers are associated with the potential for a Dam (Basin) structural failure.

6.2 Gordon Road Bardon Detention Basin – Failure Impact Assessment (FIA)

During the design of the basin, a Preliminary Failure Impact Study was prepared (ARUP, 2015) in

accordance with Queensland government guidelines (DEWS, 2012). Possible failure mechanisms and risks

to the PAR downstream of the basin were investigated.

ARUP identified and investigated two possible breach scenarios, a large breach and a confined breach.

Both of these resulted from an overtopping failure triggered by water level reaching EL 76.00 m AHD. The

design 1 in 50 AEP flood was identified as the Dam Crest Flood Event while the 1 in 34800 AEP event was

identified as the Acceptable Flood Capacity event.

A licence for a referable dam was issued in February 2018 setting out the approved conditions to be met by

the Dam Owner in operating and managing the dam. A copy of the licence conditions is included in

Appendix F.

6.3 Possible Flood–related Failure Mechanisms Considered for the Gordon Road

Detention Basin

Possible failure cases for GRBDB are:

• Breach failure from a Dam Crest Flood (1 in 50 AEP – approx. 102 mm rainfall in an hour);

• Dam collapse due to overtopping in an extreme event (up to 1 in 34,800 AEP event or between 102

to 243mm rainfall in 1 hour)

Sunny Day Failure is not identified as a possible threat to the community as the dam does not contain a

permanent storage component other than a small wetland in the base of the basin.

Other potential failure mechanisms considered include:

• Damage or collapse of the dam as a result of earthquake/tremors or high impact events (including

terrorist activity);


• Sudden collapse due to associated structural failures, either seepage under the basin wall leading

to foundation failure, sliding, overturning or structural failure;

• Erosion and undermining of the foundation;

• Long-term damage to the basin wall including cracking /deformation /sliding due to other reasons.

6.3.1 Sudden Collapse Due to Seepage Under the Basin

Sudden collapse from seepage under the basin is not considered a possibility for this structure, as there is

no permanent storage in the basin. Even with the basin full, there is insufficient head to cause seepage

through a foundation which is primarily on rock. Any evidence of seepage through bedrock joints should be

detected during annual maintenance inspections and could be grout injected to remove it in the future. Any

increase in outflow due to seepage is not considered a threat and would be unlikely to cause serious damage

to the downstream community.

6.3.2 Erosion and Undermining of the Foundation

This failure mechanism has not been investigated in detail as the basin is founded on competent rock. There

will be no permanently stored water in the basin to provide the required hydraulic head to initiate seepage

through the foundation. Evidence of wet areas in the downstream channel and banks or any evidence of

slumping or movement of the structure (which may initiate cracking of the concrete parapet), should be

reported and investigated. Prompt repairs and remedial works will ensure the ongoing integrity of the

structure.

6.3.3 Cracking and Development of Uncontrolled Seepage

Any evidence of cracking of the concrete weir or parapet walls should be investigated thoroughly and repairs

made as soon as possible. Cracking of the parapet walls may be difficult to detect and the rock protection

work may have to be partially removed to facilitate this. Inspections should carefully examine any differential

movement of the weir slab as it may indicate an underlying problem with the wall that cannot be readily

seen. However, as there is no permanent storage, it is unlikely that cracking could develop into a sudden

failure in the limited time the basin is holding water.

6.4 Situation 1 – Dam Crest Flood (1 in 50 AEP) with Structural Failure

A Dam Crest Flood is likely to result from a 1 in 50 AEP rainfall event, equivalent to the runoff from 102mm

rainfall in an hour. In the preliminary FIA, the failure mechanism considered was a breach from dam crest

level to the toe level at 71.75 m AHD.

Two breach shapes were tested. One was a larger breach having a width of 51m at the dam crest reducing

to 4m at the toe. The other was a confined breach in trapezoidal shape having 12.5m width at the crest and

reducing to 4m width at the toe.

The confined breach resulted in a total discharge (including culvert flow) of 19.3 m3/s from failure during a

dam crest flood. The amount of material removed to form the breach was 495 m3.

In both design scenarios, commencement of the breach occurs when the basin fills. Breach development

takes 22 to 27 minutes giving peak basin outflows (including culvert flow) within 1.25 hours of the start of

the design rainfall event.

GRBDB is located in a remote location and it will not be possible to attend the site during a rainfall event,

therefore the only way Council can confirm the integrity of the dam wall is to infer it from the water level

record.

A water level drop of more than 1 m in 6 minutes should alert officers to the possibility that the structural

integrity of the wall has been compromised. Unfortunately, by the time Council receives and alert of this

nature, the resulting flood flow will have reached and potentially impacted the downstream properties.


A breach event is expected to impact up to 15 houses which may be directly impacted with depths of flooding

of up to 300mm.

Potential inundation and impact areas for this event have been mapped and are presented in Appendix A,

Figure A2. The FIA for GRBDB also undertook sensitivity analysis using the 1 in 500 AEP event. Inundation

extents for this event are presented in Figure A3.

Actions in response to the Dam Crest Flood failure scenario are provided in Table 7.


Table 7 - Situation 1 – Dam Crest Flood EAP Response (Possible Structural Failure)

EAP Phase Alert Lean Forward Stand Up Stand Down

Trigger ID Monitor Trigger 1 Trigger 2 Trigger 3 Trigger 4

Event Data

Water Level Status Warning issued by BoM for rainfall greater than 100mm and possible flash flooding

WL at or above 72.6 m

AHD and rising

(1 in 10 AEP)

WL at or above 75.0 m AHD (i.e. 1 m below crest) and rising

(1 in 20 AEP)

WL at 76.35 m AHD

(1 in 500 AEP)

WL <72.6 m AHD and

dropping predictably

Rainfall Status 40 mm in 30 minutes

1 in 20 AEP rain

70 mm in 30 min

1 in 50 AEP rain

100 mm in 60 min

1 in 100 AEP rain

150 mm in 60m

1 in 500 AEP rain

No rain for last two hours

Dam Status Catchment runoff beginning to enter basin

Observed structural issues with dam such as seepage, cracking or evidence of erosion or movement

WL above culvert obvert and rising

Basin expected to overflow within 20 to 30 mins

If no structural issues dam failure not expected.

If structural issues, anticipate possible failure. Use Dam Crest Flood extents (Figure A2) to estimate impacts

Dam is overflowing with 350 mm over crest.

Refer Situation 2

WL below triggers

Response Actions

Internal Alerts Automated rain and WL trigger alerts to Flood Officer and ERC

Automated rain and WL trigger alerts to Flood Officer and ERC



None

Population at Risk messaging

BoM preliminary advice only

BoM Flash Flood and severe storm warnings only

Pre-worded EWA

Media and social media messaging

Pre-worded EWA and Warning EA with SEWS





Dam Owner Activate EAP Advise CEO of Stand-up

Advise CEO, Councillors and Lord Mayor and DNRME of event status


Authorise relevant inspections and repairs as necessary

Prepare EER and submit to DSR

Dam Asset Manager Coordinate relevant pre-event inspections and repairs if time permits and it is safe to do so.

Advise ERC of status

Remove resources from site once it is unsafe to continue.

Receive advice from ERC

Monitor developing situation

Ready resources for deployment when safe to do so.




Coordinate relevant inspections and repairs as necessary when safe to do so.


Liaise with Flood Officer and Dam Asset Manager

Liaise with QPS and SES and Dam Asset Manager re status of dam

Advise Dam Owner, internal and relevant external parties of event status


Implement appropriate Disaster Response Plan including PAR warnings


Flood Officer Monitor rainfall and dam WL

Monitor rainfall and dam WL

Advise ERC of Lean Forward

Actively monitor rainfall, inflows, outflows and dam WL

Ensure PAR messaging has been sent

Advise ERC of Stand Up trigger



Report likely impacts to ERC


Advise ERC of Stand Down trigger

Report on potential impacts

BMTMC Provide up to date public

messaging through the

131940 hotline and

website, variable message

signs (VMS) messages and

radio broadcasts on road

closures and incidents on

the road network

Provide up to date public


131940 hotline and





the road network



131940 hotline and





the road network

Liaise with the FIC and DM

on potential and actual

road closures;



131940 hotline and





131940 hotline and website,

variable message signs (VMS)

messages and radio

broadcasts on road closures

and incidents on the road

network;





the road network;

Advise Translink about

potential impacts to public

transport



transport;


Receives calls coming into Brisbane City Council via the Contact Centre



Receives calls coming into

Brisbane City Council via the

Contact Centre

Field Services Proactive coordination of field resources as required

Coordinate field resources as required for recovery

SDCC 24/7 Duty Officer Monitor developing situation


Issue pre-worded Emergency Alert voice and text warnings with SEWS

Coordinate relevant resources as needed.

QPS Receive advice from ERC






Assist with recovery phase as needed when safe to do so.

QFES Receive advice from ERC






Assist with rescue and recovery phase as needed when safe to do so.

DNRME Receive advice from ERC


Monitor situation and liaise with Dam Owner

Review EER



6.5 Situation 2 -- Dam Crest Overtopping With Structural Failure

Any outflow events rarer than 1 in 50 AEP will cause uncontrolled discharges, which are likely to exceed the

capacity of the downstream drainage system, have the potential to cause property damage and pose a risk

to the safety of the PAR. The preliminary FIA investigation work undertaken by ARUP (2015) routed the 1

in 100 AEP (116mm rain in 1 hour) and the 1 in 500 AEP (150mm rain in 1 hour) design events through the

dam. These events overtopped the dam.

As designed, uncontrolled outflows from the basin may occur due to overtopping in events rarer than 1 in

50 AEP. All overtopping flows greater than the 1 in 50 AEP event will pass through the basin without any

mitigation. Water levels at the upstream end of the piped drainage system are expected to peak within five

to ten minutes of overtopping.

It should be noted that the duration of overflows and the volume of the hydrograph for floods exceeding the

dam crest flood are typically short and for flows up to the 1 in 500 AEP event, are not expected to cause

significant downstream impacts provided the basin wall remains in place.

The 1 in 34,800 AEP rainfall event (approximately 243 mm in 1 hour) was nominated as the Acceptable

Flood Capacity (AFC) event. This results in a design water level of 76.6 m AHD at the basin crest with

overtopping occurring approximately 45 min from the start of the storm. The basin wall has been designed

and constructed to withstand a flood of this magnitude. The annual chance of a flood greater than that

magnitude occurring is less than 0.003%.

Note: A 1-hour PMP (Probable Maximum Precipitation) storm event (approximately 380 mm in 1 hour) in

the basin catchment will also fill and overtop the dam. The PMF (Probable Maximum Flood), assumed to

result from the PMP rainfall is estimated to reach a peak basin water level of 76.88 m AHD. The

corresponding design discharge from the PMF would be in the order of 62 m3/sec.

Failure of the basin wall at the AFC has been assessed. The potential inundation and impact areas for this

event have been mapped and are presented in Appendix A Figure A4

Actions in response to the AFC overtopping failure scenario are provided in Table 8.


Table 8 - Situation 2 – Dam Crest Overtopping EAP Response


Trigger ID Monitor Trigger 1 Trigger 2 Trigger 3 Trigger 4

Event Data

Water Level Status Warning issued by BoM for rainfall greater than 100mm and possible flash flooding

WL at or above 72.6 m

AHD and rising

(1 in 10 AEP)

WL at or above 75.0 m AHD (i.e. 1 m below crest) and rising

(1 in 20 AEP)

WL at 76.35 m AHD

(1 in 500 AEP)

WL <72.6 m AHD and

dropping predictably

Rainfall Status 40 mm in 30 minutes

1 in 20 AEP rain

70 mm in 30 min

1 in 50 AEP rain

100 mm in 60 min

1 in 100 AEP rain

150 mm in 60m

1 in 500 AEP rain

No rain for last two hours

Dam Status Catchment runoff beginning to enter basin

WL above culvert obvert and rising

Basin expected to overflow

If no structural issues dam failure not expected.

If structural issues, anticipate possible failure. Use Dam Crest Flood extents (Fig A2 and A4) to estimate impacts

Dam is overflowing with 350 mm over crest

WL below triggers

Response Actions

Internal Alerts Automated rain and WL trigger alerts to Flood Officer and ERC




None

Population at Risk messaging

BoM preliminary advice only

BoM Flash Flood and severe storm warnings only

Pre-worded EWA


Pre-worded EWA and Warning EA with SEWS





Dam Owner Activate EAP Advise CEO of Stand-up



Authorise relevant inspections and repairs as necessary

Prepare EER and submit to DSR

Dam Asset Manager Coordinate relevant pre-event inspections and repairs if time permits and it is safe to do so.

Advise ERC of status

Remove resources from site once it is unsafe to continue.







Coordinate relevant inspections and repairs as necessary when safe to do so.


Liaise with Flood Officer Liaise with QPS and SES and Asset Manager re status of dam


Advise Dam Owner, internal and relevant external parties of event status.

Implement appropriate Disaster Response Plan including PAR warnings


Flood Officer Monitor rainfall and dam WL


Advise ERC of Lean Forward



Advise ERC of Stand Up



Advise ERC of Activation

Report likely impacts


Advise ERC of Stand Down

Report on potential impacts

BMTMC Provide up to date public


131940 hotline and






131940 hotline and






131940 hotline and




Liaise with the FIC and DM

on potential and actual

road closures;



131940 hotline and



131940 hotline and







the road network


the road network


the road network





the road network;



transport


the road network;



transport;






Field Services Proactive coordination of field resources as required

Coordinate field resources as required

SDCC 24/7 Duty Officer Monitor developing situation


Issue pre-worded Emergency Alert voice and text warnings with SEWS

Coordinate relevant resources as needed.

QPS Receive advice from ERC






Assist with recovery phase as needed when safe to do so.

QFES Receive advice from ERC






Assist with rescue and recovery phase as needed when safe to do so.

DNRME Receive advice from ERC


Monitor situation and liaise with Dam Owner

Review EER



6.6 Situation 3 - Damage to the Basin as a Result of Earthquake

While South East Queensland does not have a history of moderate or major earthquakes, they are possible,

albeit rare occurrences. An earthquake equal to or stronger than magnitude 5.5 may cause slight damage

to the concrete structure. However, it is unlikely that the basin wall will sustain sufficient damage in an

earthquake of up to magnitude 6.0 to result in a serious leakage problem or to trigger a sudden collapse.

Even if there was serious damage to the basin wall from an earthquake, the dam needs to be full at the time

of the event to pose any risk at all.

The maximum amount of damage likely to occur from a mild-moderate tremor would be cracking or

differential movement of the concrete parapet walls (particularly at the abutment cut/fill line, or where the

retaining wall changes direction). Such damage is unlikely to occur while the basin is full. Therefore, the

possibility of this failure mechanism occurring can be mitigated by regular inspections.

Nevertheless, given the time it may take to enact repairs following any earthquake damage, vigilance around

the monitoring of any adverse rainfall events is to be maintained. The worst case scenario from such a

situation is best described by the Dam Crest Flood breach failure – refer Situation 1.

The following steps are recommended to be undertaken following an earthquake event.

• Undertake an inspection of the structural concrete work within thirty days of any earth tremors of

less than 5.5 magnitude;

• Undertake immediate inspection of the structural concrete work within five working days of any earth

tremors greater than 5.5 magnitude;

• Carry out any maintenance or repairs necessary as a matter of priority in accordance with the

Detailed Operations and Management Manual.

6.7 Situation 4 – Terrorist or High Energy Impact

Any identified sabotage or vandalism should be treated seriously and the following actions are

recommended:

• Immediately report the incident to Queensland Police Service by calling 000

• Report the incident to National Security Hotline by calling 1800 123 400.

• Take photographs of the damage or incident site

• If possible and safe to do so, record and photograph unusual vehicle details including registration,

description, time, date etc.

• Barricaded the area to enable the incident site to be inspected and investigated

• Conduct a dam safety inspection

Such an event would only represent a risk to the downstream community should a significant rainfall event

occur whilst the basin is in a damaged state. The worst-case scenario from such a situation is best described

by the Dam Crest Flood breach failure – refer Situation 1.


7.0 Activation of the EAP

7.1 Emergency Management to Identify and Minimise Risk

Whenever a severe weather event is forecast by the Bureau of Meteorology (BoM) or any situation develops

within the catchment which might require a heightened response, close monitoring of BoM advice and

Council’s flood information systems are to be undertaken by authorised and trained BCC Flood Information

Centre (FIC) personnel. They are to be alert to potential hazard developments and maintain vigilance during

large and extreme rainfall events with reference to the hydraulic functioning of the basin.

Regular maintenance of the basin wall and inspection of relevant areas prior to such warnings as

scheduled/planned would help to assure that there is no structural impediment to the design function of the

basin wall during a storm event.

Analysis of runoff patterns has demonstrated that water level in the basin could rise rapidly to the crest level

if 102mm of rainfall falls within one hour (1 in 50 AEP-1hour duration design storm event). In this design

scenario, basin water levels are expected to peak approximately within 60-75 minutes from the start of the

storm.

If one hourly rainfall is more intense and likely to exceed 100mm in one hour, water levels are likely to peak

in less than an hour and will almost definitely overtop the dam wall. Therefore, the effective warning time

available to issue warnings and alert notifications during intense storm events is limited.

The effectiveness of actions taken during and after an event will depend largely on how effective the pre-

event community education has been. Ongoing community awareness and education programs aimed at

increasing awareness of possible hazards in the surroundings, identifying safe refuge locations, and safe

evacuation routes in accordance with Council’s adopted Dam Event Public Warning and Education Protocol

are essential. Such programs can enhance community resilience and ensure the PAR can become self-

reliant and proactive during and after a dam hazard event.

7.2 Stages of Emergency Services Activation

The EAP should be activated when there is a developing dam hazard event or when an emergency event

is occurring at the dam and there is a potential to place people and property at risk.

Full activation may not be possible or even required for minor incidents such as cracking, small slips, sink

holes if they occur near the basin wall. Such events are likely to be detected during routine inspections and

are unlikely to coincide with elevated water levels in the basin.

However, these incidents need investigation, repair and adequate monitoring to prevent further

deterioration. Refer to the Detail Operation and Management Manual for details.

Activation of the EAP in response to a Dam Hazard Event will follow the following sequence as the event

develops:

• Alert

• Lean Forward

• Stand Up

• Stand Down

The stages are summarised in Table 9.


Table 9 – EAP Escalation Levels

Level Conditions

Alert ▪ A heightened level of vigilance due to the possibility of a major event in the

GRBDB catchment.

▪ Preventative action is recommended at this stage and residents in the

evacuation area already experience overland flooding in their streets with

anything over a 1 in 10 AEP (10%) rainfall event.

▪ Duration of this level is dependent on the rate of development of the

potential failure condition.

▪ During the alert level, agreement on the need for and frequency of

situational reports should be discussed with the ERC.

▪ No further action may be required. However, the situation may need to be

monitored by someone capable of assessing the potential of the threat

Lean Forward ▪ A heightened level of situational awareness of a potential dam hazard event.

▪ Commence moving into a state of operational readiness. Disaster coordination

centres are placed on standby, prepared but not activated. Information is

received that the area may be impacted by an emerging dam hazard event.

▪ At this stage, the relevant agencies, are requested to Lean Forward and

confirm contact details. The Local Disaster Coordination Centre (LDCC) is

checked for operational readiness.

Stand Up ▪ The operational state following Lean Forward whereby resources are ready

to be mobilised, personnel are activated and operational activities

commenced. Disaster coordination centres are activated. Information is

received to confirm that the impact of a disaster situation within the area is

imminent.

▪ Relevant members are requested to Stand Up. The LDCC should be now

operating on a 24-hour basis. There should be ongoing liaison between the

LDMG, DDMG and QDMC (if activated), including release of situation reports

(SITREPs), as required by the reporting requirements of the Local Disaster

Management Plan.

Stand Down ▪ Transition from responding to an event back to normal core business and/or

recovery operations. There is no longer a requirement to respond to the event

and the threat of a disaster has passed.

▪ When the requirements of disaster operations have been completed to the

stage that the LDCC are no longer required to be activated, they may be stood

down.

7.3 Initiation of an Emergency

Key members of the Brisbane City Council, including the Flood Duty Officer and Council’s Disaster

Operations staff receive advance warnings from the Bureau of Meteorology of impending extreme weather

events.

It is acknowledged that due to the flash flood nature of this catchment, advance warning of significant rain

producing weather systems cannot be guaranteed. In the event that the BoM predicts high rainfall totals and

advance warning is received of likely flash flood producing rain in the catchment, the Flood Officer is to

inform the Event Response Coordinator (initially the Manager, Disaster Management or the Disaster

Management Duty Officer). If the LDCC is not yet stood up, the Manager, Disaster Management or the

Disaster Management Duty Officer may initially fill the role of the LDCC Incident Controller.


During this period and until the situation has stabilised and the threat passed, key operational staff are to

remain in a state of heightened awareness of developing weather conditions and act in accordance with the

requirements set down in the EAP.

Persons that become aware of a structural deficiency associated with the basin, either during a rainfall event

or at any other time during an impending flood emergency or other non-flood related issues are to contact

the Council Customer Service Centre or After Hours Emergency Centre on 07 3403 8888 and direct their

enquiry to the Regional Manager, West.

7.4 Notifications on Activation of the EAP

In the case of an emergency situation, the Dam Owner after advising the ERC, will make a decision (in

consultation) to activate the Emergency Action Plan and request the ERC:

o Notify the Local Disaster Coordinator; then

o Notify District Disaster Management Group;

o Notify the Local Disaster Management Group – Brisbane City Council;

o Notify Queensland Fire and Emergency Services;

o Notify Queensland Police Service;

o Notify the Corporate Communications and the Contact Centre if public information and warnings are

required;

o Notify the Brisbane Metropolitan Transport Management Centre about actual and potential road

closures;

o Notify other persons/organisations listed in the Relevant Agencies Listing Table. Refer Table 6 and

Figure 5.

7.5 Emergency Situation - Alert Triggers

The water level triggers presented in Figure 8 are incorporated into Council’s Alert protocols in accordance

with the pre-approved messages in Section 7.6 of this EAP.

For reference, the design 1 in 50 AEP:60 minute inflow and outflow hydrographs, and cumulative rainfall

and predicted water levels are also shown in Figure 6 and Figure 7, respectively.


Figure 6 – Inflow, Outflow and Peak Water Levels in GRBDB for 1 in 50 AEP Event

Figure 7 – Catchment Rainfall and Peak Water Levels in GRBDB for 1 in 50 AEP Event.

71.00

72.00

73.00

74.00

75.00

76.00

77.00

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

16.00

0 50 100 150 200 250

1 in

Infl

ow

& O

utf

low

(m

3/s

)

Time(mins)

1 in 50 AEP - 60min Inflow, Outflow & Water Level

Inflow-q50 60m Outflow Stage

71.00

72.00

73.00

74.00

75.00

76.00

77.00

0.0

20.0

40.0

60.0

80.0

100.0

120.0

0 50 100 150 200 250m

AH

D

Rai

nfa

ll(m

m)

Time(m)

1 in 50 AEP - 60min - Rainfall & Water Level

50y 60m rain Stage


Figure 8 – Gordon Road Bardon Detention Basin - Emergency Situation Alert Triggers

77

76

75

74

73

72

71

70

Gordon Road Bardon - Detention Basin

Culvert sill level= 71.38 mAHD

Water level = above 72.6 mAHD

Water level= 75 mAHD - 1m below Basin crest

Lean Forward - Monitor water levels - Trigger-1 : Internal messaging

STANDUP -Trigger 2 - External messaging

Basin crest76.0 mAHD

Basin base= 70.5m AHD

Culvert outlet = 71.03 mAHD

Culvert obvert level = 72.58 mAHD

Water level = 76.35 mAHD - 350mm over Basin crest Trigger 3 - Emergency Actions- As in EAP


7.6 Pre-approved Wording of the Agreed Notification and Warning Messages

A notification provides appropriate information and advice on a heightened risk to enable those potentially

involved to make informed decisions about preparedness and safety.

A warning is the dissemination of an urgent message signalling an imminent hazard event, or emergency

event and provides advice on protective measures.

The warning messages involve more than notifying people about the technical nature of a release of water

from the dam. The message includes telling people if, when, and potentially even how, they need to act to

protect life or property.

Warning messages inform those at risk, or whose property is at risk, of an impending escalation of an emergency event and aims to prompt an appropriate response or action from those persons. The required action is contained in the warning message, for example, ‘seek further information’, ‘take shelter’, ‘evacuate’ or ‘activate your personal emergency plan’.

The pre-approved wording of notification and warning messages to be issued under this EAP are presented in Table 10.

Table 10 – Summary of Pre-approved Emergency Communication Messaging to the PAR

Dam

warning type

Trigger Level 1 Trigger Level 2 Trigger Level 3

Gordon

Road

Detention

Basin

Water Level rising

> RL72.6 (above

box culvert

obvert)

Water Level 1 m below basin

crest – RL 75.0 m AHD

Water over basin crest - > RL 76.35 m AHD

(350 mm above crest) – water level now

exceeding the 1 in 500 AEP flood.

EWA

Messaging

*No Public

Messaging at this

stage.

Internal Heads-up

alert to FIC Duty

Officer generated

by FloodWise.

Consult EAP to

check triggers

Phone Voice Message:

{104 characters}

Gordon Road Bardon - heavy rain

– flash flooding possible in next 20-

30 minutes. Stay out of flood water

SMS – Twitter Text: {104

characters}

Gordon Road Bardon - heavy rain

– flash flooding possible in next 20-

30 minutes. Stay out of flood water

Phone Voice Message: {87 characters}

Gordon Road Bardon – dam now spilling – flash

flooding likely. Stay out of flood water

SMS – Twitter Text: {87 characters}

Gordon Road Bardon – dam now spilling – flash

flooding likely. Stay out of flood water

EA

Messaging

NA NA Voice Warning (Priority 1): {348 characters}

Emergency Emergency. This is a dam failure

warning from Queensland Fire and Emergency

Services. Gordon Road Detention Basin is at

imminent risk of failure. Move immediately to high

ground away from Gordon Road. You should warn

neighbours. For more information listen to local

radio or visit w w w dot Brisbane dot q l d dot gov

dot a u

SMS Warning (Priority 1): {157 characters}

Warning.GordonRoadDetentionBasin imminent

failure risk. Move immediately from GordonRoad

to high ground. Warn others. Radio or

www.brisbane.qld.gov.au

Note: The Standard Emergency Warning Signal (SEWS) will be activated when a priority 1 EA message is sent.

http://www.brisbane.qld.gov.au/


8.0 Emergency Event Report (EER)

The dam owner is required to prepare an emergency event report (EER) and submit it to the chief executive

(dam safety regulator) within 30 business days (or another period agreed in writing with the chief executive)

at the conclusion of an emergency event which has resulted in the activation of the EAP, where:

• a person or property has been or may have been harmed because of the event; and

• any of the following applies -

(i) a coordinated response involving two or more relevant entities;

(ii) an event arose because of disaster situation declared under the Disaster Management Act;

(iii) an entity performing functions under the State Disaster Management Plan, required the dam

owner to provide information about the event,

An emergency event ends when the dam hazard that triggered the event, no longer presents a material risk

to persons or property.

The EER should provide a timeline of events, including monitoring and inspection data (rainfall, storage

level, seepage, etc.), which were used to make EAP activation decisions.

The EER should also outline responsibilities associated with emergency communications between the dam

owner, governments (local and state), disaster management groups (local and district) and the PAR and the

wider community (if relevant).

The EER should include photographs of the event.


9.0 Dam Event Public Warning and Education Protocol

Figure 9 – Dam Event Public Warning and Notification Protocol

9.1 Public Education

Council’s Public Warning and Education Protocol (Figure 9) shows Council’s adopted protocol to ensure

regular community education programs are in place to keep the PAR fully aware of issues related to the

safety and management of the basin.

To facilitate public education, the following programs have been put in place:

• Signage will be erected in the area near Gordon Road Detention Basin to advise the PAR to contact

Council if they have any concerns about the dam;

• The PAR will receive a letter from Council on an annual basis advising them about the dam and

inviting them to subscribe to the Early Warning Alert service to receive alerts if the dam is at risk of

over topping;

• In the event that the dam is at risk of over topping an early warning alert message will be sent to

subscribers;

• In an extreme event (such as a 1 in 500 AEP rain event), a pre-worded Emergency Alert will be sent

to the PAR and people in the vicinity of the dam. See draft alerting polygon, Appendix A – Figure

A.5);

• The pre-prepared message and alert polygon will be saved at the State Disaster Management

Centre for use during an emergency event. A summary of the pre-worded alert messages is

included in Section 6.8 and summarised in Table 9.

9.2 Staff Training and Exercises

Regular joint exercises will be held involving Council officers and other authorities involved in implementing

the EAP to test and strengthen the EAP procedures described herein.

The EAP will reviewed and updated to incorporate learnings from the training and to reflect changes in best

management practices.


APPENDIX A – Population at Risk and Inundation Mapping


Figure A1 – Gordon Road Bardon Detention Basin – Catchment Plan

Blank Page


Figure A2 – Gordon Road Bardon Detention Basin – Inundation for 1 in 50 AEP Dam Crest Flood Failure


Figure A3 – Gordon Road Bardon Detention Basin – Inundation Extent for 1 in 500 AEP Dam Crest Flood Failure


Figure A4 – Gordon Road Bardon Detention Basin – Inundation Extent for 1 in 34,800 AEP Dam Overtopping Flood with Structural Failure


Figure A5 – Gordon Road Bardon Detention Basin – Flood Depth in 1 in 34,800 AEP Dam Overtopping Flood Failure


Figure A6 – Gordon Road Bardon Detention Basin – Emergency Messaging Polygon


APPENDIX B – Summary of EAP Activation and Alert Triggers

77

76

75

74

73

72

71

70

Gordon Road Bardon - Detention Basin

Culvert sill level= 71.38 mAHD

Water level = above 72.6 mAHD

Water level= 75 mAHD - 1m below Basin crest

Lean Forward - Monitor water levels - Trigger-1 : Internal messaging

STANDUP -Trigger 2 - External messaging

Basin crest76.0 mAHD

Basin base= 70.5m AHD

Culvert outlet = 71.03 mAHD

Culvert obvert level = 72.58 mAHD

Water level = 76.35 mAHD - 350mm over Basin crest Trigger 3 - Emergency Actions- As in EAP


APPENDIX C – Contact Lists for PAR and Key Council Officers

Appendix C has been redacted


APPENDIX D – Modified Mercalli Earthquake Intensity Scale – Damage

Guide

Earthquake Magnitude

Typical Maximum Modified Mercalli Intensity

1.0 – 3.0 I

3.0 – 3.9 II – III

4.0 – 4.9 IV – V

5.0 – 5.9 VI – VII Prioritise repairs with resource availability but generally within 60 days.

6.0 – 6.9 VII – IX – URGENT REPAIRS May be needed to concrete structures around spillway pipes.

7.0 and higher VIII or higher

Abbreviated Modified Mercalli Intensity Scale

I Not felt except by a very few under especially favourable conditions.

II Felt only by a few persons at rest, especially on upper floors of buildings.

III Felt quite noticeably by persons indoors, especially on upper floors of buildings. Many people do not recognize it as an earthquake. Standing motor cars may rock slightly. Vibrations similar to the passing of a truck. Duration estimated.

IV Felt indoors by many, outdoors by few during the day. At night, some awakened. Dishes, windows, doors disturbed; walls make cracking sound. Sensation like heavy truck striking building. Standing motor cars rocked noticeably.

V Felt by nearly everyone; many awakened. Some dishes, windows broken. Unstable objects overturned. Pendulum clocks may stop.

VI Felt by all, many frightened. Some heavy furniture moved; a few instances of fallen plaster. Damage slight.

VII Damage negligible in buildings of good design and construction; slight to moderate in well-built ordinary structures; considerable damage in poorly built or badly designed structures; some chimneys broken.

VIII Damage slight in specially designed structures; considerable damage in ordinary substantial buildings with partial collapse. Damage great in poorly built structures. Fall of chimneys, factory stacks, columns, monuments, walls. Heavy furniture overturned.

IX Damage considerable in specially designed structures; well-designed frame structures thrown out of plumb. Damage great in substantial buildings, with partial collapse. Buildings shifted off foundations.

X Some well-built wooden structures destroyed; most masonry and frame structures destroyed with foundations. Rails bent.

XI Few, if any (masonry) structures remain standing. Bridges destroyed. Rails bent greatly.

XII Damage total. Lines of sight and level are distorted. Objects thrown into the air.


APPENDIX E - Definitions/Glossary

Reference: https://www.dews.qld.gov.au/__data/assets/pdf_file/0018/84015/eap-guideline.pdf

The Act Water Supply (Safety and Reliability) Act 2008

(EAP) Activation

Is defined as actions undertaken by the dam owner as per the EAP in response to a dam

event if:

1. persons or property may be harmed, because of the event

2. a coordinated response involving two or more of the following relevant entities is likely

to be required to respond to the event:

• each local group (LDMG) and district group (DDMG) for the emergency action plan

• each local government whose local government area may be affected if a dam

hazard event or emergency event were to happen for the dam

• the DNRME chief executive

• another entity the dam owner considers appropriate i.e. QPS, QFES.

Alert

The first stage of emergency response whereby a heightened level of vigilance is maintained

due to the possibility of an emergency event occurring. Action is required to ensure the

situation is monitored by someone capable of assessing the potential of the threat.

Approved emergency

action plan

An emergency action plan that is approved under s 352I(1)(a) or taken to be an approved

emergency action plan under s 352Q(2).

(Refer s 352A of the Act.)

Approval period (for

an EAP)

The period of approval for the EAP can be for a period of no more than five years and must

be stated in the approved EAP (refer s 352K(2)).

Chief Executive

In this guideline, unless otherwise specifically given a different meaning, references to the

‘chief executive’ or the Dam Safety Regulator are to be interpreted as references to the

Director-General of the Department of Natural Resources, Mines and Energy or the Director-

General’s delegate.

Correspondence to the Director-General’s delegate can be sent to:

Chief Executive

Department of Natural Resources, Mines and Energy

Water Supply Division

PO Box 15216, City East QLD 4002

or via email to: [email protected]

Controlled document Having an EAP issued as a ‘controlled document’ means that specified copies of a document

are kept up to date in a controlled manner using a system that distributes updated

versions/pages of the document as they are issued and retrieves superseded versions/pages

of the document as they become redundant. In this way, only the current version of the

document is used during any event.

A controlled document requires the following metadata to be recorded in the document and

securely archived:

• contents, versions and dates of versions

• name and role of the person approving each version and details of any prior

consultation undertaken

• names and roles of persons issued with copies.

Dam hazard Dam hazard, for a dam, means a reasonably foreseeable situation or condition that may:

a) cause or contribute to the failure of the dam, if the failure may cause harm to

persons or property

or

b) require an automatic or controlled release of water from the dam, if the release of

the water may cause harm to persons or property.


Dam hazard event An event arising from a dam hazard if persons or property may be harmed because of the

event and

a) a coordinated response involving 2 or more of the relevant entities

b) mentioned in paragraphs (b) to (d) of the definition relevant entity is unlikely to be

required to respond to the event

c) the event is not an emergency event.


https://www.dews.qld.gov.au/__data/assets/pdf_file/0018/84015/eap-guideline.pdf


Dam Safety Team Group of engineers and professionals working in the administering state government agency

District group

DDMG

District disaster

management group

The district group for an emergency action plan, means a district group established under the

Disaster Management Act 2003 (DM Act), s 22 whose disaster district under that Act could,

under the plan, be affected by a dam hazard.

District disaster management group/s established under the DM Act, comprise

representatives from regionally based Queensland Government agencies, which provide and

coordinate whole-of-government support and resource gap assistance to disaster-stricken

communities. The district group/s perform a 'middle management' function within the disaster

management arrangements by coordinating the provision of functional agency resources

when requested by local group/s on behalf of local government/s.

Disaster management

plan (DMP)

A local or District Disaster Management Group’s disaster management plan under the DM

Act.

Disaster risk

assessment

The process used to determine risk management priorities by evaluating and comparing the

level of risk against predetermined standards, target risk levels or other criteria (Council of

Australian Governments (COAG), Natural Disasters in Australia: Reforming mitigation, relief

and recovery arrangements: 2002).

Incorporates the processes of risk identification, risk analysis and risk evaluation (refer to ISO

Guide 73:2009 Risk management - Vocabulary).

Dam Safety Regulator

(DSR)

Refer to the ‘chief executive’ above.

Emergency alert

(EA)

The emergency alert (EA) system is a national telephone warning system administered in

Queensland by the Queensland Fire and Emergency Service.

The EA system provides emergency authorities with a rapid mass notification service to

deliver preformatted messages via landline and mobile telephones within a defined

geographic area.

Emergency

event

An event arising from a dam hazard if persons or property may be harmed because of the

event, and any of the following apply:

i. A coordinated response where two or more of the relevant entities, mentioned in

paragraphs (b) to (d) of the definition relevant entity, are likely to be required to

respond to the event.

ii. The event may arise because of a disaster situation declared under the DM Act.

iii. An entity performing functions under the State disaster management plan may,

under that plan, require the owner of the dam to give the entity information about

the event.

(Refer s 352A of the Act)

Emergency event

interim report

An interim report on the performance of the dam and the functioning of the EAP during an

emergency event, which is submitted to the chief executive prior to the end of the event at the

request of the chief executive.

(Refer s 352U(2)(a) of the Act)

Emergency event

report (EER)

A report on the performance of the dam and the functioning of the EAP during an emergency

event, which is presented to the chief executive following the end of the event.

(‘End’ of an emergency event means when the dam hazard giving rise to the event is no

longer a risk to persons or property.)

(Refer s 352T(2) of the Act)

Failure (of a referable

dam)

Means — (a) the physical collapse of all or part of the dam; or (b) the uncontrolled release of

any of the dam’s contents.

Failure impact

assessment

(FIA)

It is a process used under the Act to determine the number of people whose safety could be

at risk should the dam fail.

The FIA must be certified by a Registered Professional Engineer Queensland (RPEQ) in

accordance with the Act.

Failure impact rating

(FIR)

A failure impact rating is a measure of the population at risk should the dam fail. There are

two categories for referable dams:

• category 1: 2 to 100 people at risk if the dam were to fail;

• category 2: more than 100 people at risk if the dam were to fail.

Flood mitigation

manual

A manual of the operational procedures for flood mitigation for a dam that complies with s

371D of the Water Supply (Safety and Reliability) Act 2008


Hazard A source of potential harm, or a situation with a potential to cause loss (Emergency

Management Australia, 2004).

Lean forward The stage of emergency response prior to ‘stand-up’ whereby a heightened level of

situational awareness of a disaster event (either current or impending) is maintained and a

state of operational readiness is developed. Personnel at dam are on standby, ready to

activate the EAP.

Local disaster

coordinator

An officer appointed under the DM Act who is responsible for the coordination of disaster

operations for the local disaster management group.

Local disaster

management group

Local disaster management groups are established to support local government disaster

management activities. The local group is supported by the relevant district group if and when

disaster management activities exceed the capacity of a local group. The functions of the

local group include (but are not limited to):

• developing, regularly reviewing and assessing effective disaster management

• assisting local government for its area to prepare a local disaster management

plan

• ensuring the community is aware of ways of mitigating the adverse effects of an

event, and preparing for, responding to and recovery from a disaster

• identifying and coordinating the use of resources that may be used for disaster

operations

• managing disaster operations in the area under policies and procedures decided

by the State group

• ensuring disaster management and disaster operations in the area are

consistent with the State group’s strategic policy framework for disaster

management for the State.

Notice A statement provided to the dam owner from the local government and/or the disaster

management group on the outcomes of the assessment and review of the EAP.

Notice response A statement of reply from the dam owner to the local government and/or disaster

management group on the information provided within the notice of assessment.

Early warning

notification system

Non-government, commercial subscription based warning/alert system that provides SMS,

landline, email, and social media alert messages. Members of the public are required to

register to receive the notification service.

Population at risk

(PAR)

The number of people calculated under the failure impact assessment guideline, whose

safety will be at risk if the dam, or the proposed dam after its construction, fails. For the

purposes of this EAP, PAR is the total population at risk if a dam failure event was to occur,

including transient populations as well as those at residences and businesses.

Probable maximum

precipitation (PMP)

The theoretical greatest depth of precipitation for a given duration that is physically possible

over a particular drainage basin.

Probable maximum

flood (PMF)

The flood resulting from PMP, snowmelt, coupled with the worst flood-producing catchment

conditions that can be realistically expected in the prevailing meteorological conditions.


APPENDIX F – DNRME License Conditions

The following conditions were issued by DNRME and are attached to the licence for the dam:

Condition DS 1 - Documentation

1. Any documentation prepared in order to comply with these conditions must be stored securely until

such time as the dam is decommissioned.

2. The documentation must be made available to Dam Safety Regulator for inspection within five (5)

business days of a written request for access being received by the dam owner.

3. On change of ownership of the dam, these conditions and all documentation prepared and stored

in compliance with these conditions must be transferred to the new owner.

Condition DS 2 - Incidents and Failures

1. In addition to the requirements detailed within the approved Emergency Action Plan (EAP), the dam

owner must report all incidents and failures as defined in the Queensland Dam Safety Management

Guidelines to the Dam Safety Regulator within two (2) calendar days of becoming aware of the

incident.

2. The Dam Owner must provide a report on the incident including any remedial actions to the Dam

Safety Regulator within twenty (20) business days of the incident or failure.

Condition DS 3 - Design

1. Design Report/s and any identified design and construction documentation must be referenced in the

Data Book.

Condition DS 4 - Construction

1. Any construction works must be carried out in accordance with current engineering best practice to

ensure that the dam remains generally in accordance with the documentation included in the Data

Book.

2. Proposed construction works require a design report to be submitted to the Dam Safety Regulator

at least twenty (20) business days before the commencement of construction works.

Condition DS 5 - As Constructed

1. All construction works must produce as-constructed drawings certified by a Registered Professional

Engineer (RPEQ) for inclusion in the Data Book in accordance with the Dam Safety Management

Guidelines.

2. These drawings must be provided to dam safety regulator within sixty (60) business days of practical

completion of construction of the dam.

Condition DS6 - Spillway Adequacy

N/A

Condition DS 7 - Data Book

1. The dam owner must prepare a data book within sixty (60) business days of practical completion of

construction of the dam.

2. The dam owner must maintain a data book in accordance with the current published version of the

Queensland Dam Safety Management Guidelines.

3. The data book must be reviewed and if necessary updated each calendar year. A written notification

confirming that the Data Book has been reviewed and if necessary updated must be submitted to

the dam safety regulator by 1 July each calendar year thereafter.


Condition DS 8 - Standing Operating Procedures (SOPs)

1. The dam owner must prepare standing operating procedures (SOPs) within sixty (60) business days

of practical completion of construction of the dam.

2. The Dam Owner must maintain SOPs in accordance with the current published version of the

Queensland Dam Safety Management Guidelines.

3. The dam owner must ensure the SOPs are reviewed and if necessary updated each calendar year.

A written notification confirming that SOPs have been reviewed and if necessary updated must be

submitted to the dam safety regulator by 1 July of each calendar year thereafter.

Condition DS 9 - Detailed Operating and Maintenance Manual (DOMM)

1. The dam owner must prepare detailed operation and maintenance manual within sixty (60) business

days of practical completion of construction of the dam.

2. The dam owner must maintain detailed operation and maintenance manuals in accordance with the

current published version of the Queensland Dam Safety Management Guidelines.

3. The dam owner must ensure the manuals are reviewed and if necessary updated each calendar year.

A written notification confirming that the manuals have been reviewed and if necessary updated must

be submitted to the dam safety regulator by 1 July each calendar year thereafter.

Condition DS 10 - Periodic Inspections

Not applicable.

Condition DS 11 - Comprehensive Inspections

1. The dam owner must carry out a comprehensive inspection of the dam in accordance with the

current published version of the Queensland Dam Safety Management Guidelines. The inspection

is due on or before 25 January 2023.

2. The dam safety regulator must be advised in writing at least five (5) business days prior to the date

of the inspection and may elect to observe any or all procedures involved in the inspection process.

3. A Comprehensive Inspection Report must be submitted to the dam safety regulator within sixty (60)

business days after completion of the inspection.

4. Further comprehensive inspections are to be carried out at five (5) year intervals. When a

comprehensive inspection falls in the same year that a safety review is required, this inspection

shall be undertaken as part of the safety review.

Condition DS 12 - Safety Review

1. The dam owner must carry out a safety review in accordance with the current published version of

the Queensland Dam Safety Management Guidelines. The safety review is due on or before 25

January 2038.

2. The dam safety regulator must be advised in writing at least five (5) business days prior to the date

of inspection and may elect to observe any or all procedures undertaken in the inspection process.

3. A Safety Review Report must be submitted to the dam safety regulator within sixty (60) business

days after completion of the review.

4. Further safety reviews are to be carried out at twenty (20) year intervals, but may be required by

the dam safety regulator at more regular intervals.

Condition DS 13 - Special Inspections

1. When directed by the dam safety regulator, a special inspection must be carried out in accordance

with the current published version of the Queensland Dam Safety Management Guidelines. The

cost of this inspection is the responsibility of the dam owner.


Condition DS 14 - Decommissioning

1. The dam must not be taken out of service (decommissioned) without a decommissioning plan that

has been prepared in accordance with the current published version of the Queensland Dam Safety

Management Guidelines and accepted by the dam safety regulator.

2. Following acceptance of the plan, the dam safety regulator must be advised within twenty (20)

business days of completion of the decommissioning.

Definitions

AFC’—acceptable flood capacity—the overall flood discharge capacity required of a dam determined in

accordance with these guidelines including freeboard as relevant, which is required to pass the critical

duration storm event without causing failure of the dam.

‘Dam’ means:

(a) works that include a barrier, whether permanent or temporary, that does or could impound water; and

(b) the storage area created by the works.

(c) an embankment or other structure that controls the flow of water and is incidental to works mentioned in

item (1)(a).

‘Dam Safety Regulator’ is the chief executive, or their delegate, of the Department or Agency administering the Water Supply (Safety and Reliability) Act 2008 or, if that Act is repealed, such later legislation as addresses dam safety.

‘FSL’ - for a dam, means the level of the water surface of the dam when the water storage is at maximum

operating level and the dam is not affected by flood.

‘Owner of a dam’ is the owner of land on which the referable dam is constructed, or is to be constructed.

‘PAR’ is the number of persons, calculated using FIA guidelines, whose safety will be at risk if the dam, or

the proposed dam after its construction, fails. Persons are considered to be at risk if they are within the

failure impact zone.

‘Practical completion of construction’. For the purpose of these conditions, the dam construction shall reach the stage of “practical completion of construction” when:

1. the dam embankment is capable of storage to full capacity; and 2. the inlet/outlet works are operational (minor components may not necessarily be installed).

‘Registered Professional Engineer of Queensland’: A professional engineer registered under the Professional Engineers Act 2002 in Queensland.


APPENDIX G – DRAWINGS - Gordon Road Bardon Detention Basin – General Layout


Gordon Road Bardon Detention Basin – Embankment Sections


APPENDIX H – Reference Documents

The following list of all design documents, as constructed plans, Failure Impact Statement and other

reference documents will be included in the Dam Data Book.

Design & Flood Modelling:

G:\BI\CD\Proj11\110209_Gordon_Rd_Relief_Drainage\FloodManagement\Calculations\Hydrology\WBNM

\CW_Enquiry

G:\BI\CD\Proj11\110209_Gordon_Rd_Relief_Drainage\cad\3-received\from-ARUP\20150615-GRDB

Preliminary Design Report 15 June 2015A\ GRDB_Preliminary Design Report_15June15 DAS.pdf

CA16/484711 DGE - Report - Detailed Design Appendix D Failure Impact Assessment - GRBDB_FIA

CA18/69146 DGE - GRDB - Impact of amended culvert levels - ARUP Response 23 Jan 2018

Development Permit:

CA17/607889 PLN - Approval - DA - Development Permit for Operational Work (Referable Dam) - Gordon

Road Referable Dam - 7 July 2017

CA17/459418 : DGE - Letter - Gordon Rd Detention Basin - DEWS Notice

Asset Management Plan

CA16/484554 DGE - Report - Asset Maintenance Management Plan GRBDB_AMMP

As-Constructed Drawings:

CA18/185680 Construction - Civil - North - Sch 72 - Detention Basin Gordon Road Drawings - As

Con_Form 16_Geotech & Structural Engineers Cert - 28 Feb 2018

CA18/59734 Construction - Civil - North - Sch 72 - Detention Basin Gordon Road QA - Lots Confirming

Doval 22 Jan 2018

B17065-LTR-S-0001.pdf (not registered in RM) – RPEQ Structural Certification of Construction Works –

email attachment from Chris Wilson 26/02/2018

Mapping:

G:\BI\CD\Proj18\180614_Gordon_Rd_Detention_Basin\ArcGIS\Gordon_Rd_Detention_Basin_Map_Dam_

Crest.pdf

G:\BI\CD\Proj18\180614_Gordon_Rd_Detention_Basin\ArcGIS\Gordon_Rd_Basin_50yr_60m_Dam_Brea

k_S1.pdf

G:\BI\CD\Proj18\180614_Gordon_Rd_Detention_Basin\ArcGIS\Gordon_Rd_Detention_Basin_Maps_Q34

800_S1.pdf

Draft EAP