Bundaberg Regional Council, Stormwater Management Strategy

BRC STORMWATER MANAGEMENT STRATEGY

GEOFF WILMOTH BEST PAPER AWARD

Available in ANNUAL CONFERENCE PROCEEDINGS

Tim Fichera Bundaberg Regional Council

Jordan Maultby AECOM Australia Pty Ltd

The Bundaberg region has typically developed areas where communities are exposed to overland flood risk. The community has varying levels of tolerability and expectation, resulting in Council receiving a large volume of stormwater complaints every year. Currently, Council’s management of stormwater infrastructure is driven by the “loudest voice”, leading to highly reactive investment decisions and potentially unsustainable solutions that are not coordinated.

To break out of this unsustainable regime, Council engaged in a collaborative partnership with AECOM to create an overarching Stormwater Management Strategy (BRCSMS) for the Bundaberg region. The Strategy seeks to define a clear level of service and employ risk-based decision making to inform longterm investment decisions. It also brings a holistic vision for stormwater management in the region by increasing awareness and education within the community, capturing social and environmental values, and identifying critical infrastructure needs. To achieve this, the project team engaged with community leaders and an interdepartment working group to achieve consensus through workshops – a foundation of the Strategy’s success. Key stakeholders compared local knowledge against patterns of complaints and flood damage. This information was used to define clusters of risk and inform new capital projects which could then be prioritised using a Multi-Criteria Assessment tool. The Strategy saw the commencement of a condition assessment programme which inspected asset condition and evaluated those most at risk. Utilising this data, Council was able to create a 10-year pipeline of stormwater investment projects.

The Strategy further addressed the need for a level of service framework based on community values and Council’s strategic intent. Using this framework, Council can justify an agreed level of stormwater investment and manage community expectations.

The Strategy delivers an immediate way forward for Council to address wide-ranging challenges and is currently reshaping Council’s service. The BRCSMS project highlights the value of collaborative partnerships and sets the precedent for the management of stormwater in the region.

Introduction

Background The Bundaberg Regional Council Local Government Area (BRC LGA) is situated approximately 360km north of Brisbane and covers an area of more than 6,400 square kilometres. Like most, the Bundaberg region has typically developed in areas where communities are increasingly exposed to localised stormwater drainage issues. Furthermore, stormwater drainage infrastructure and overland flow paths used to reduce the impact of stormwater drainage, may pose a risk to the safety of people and property due to existing condition and levels of service. Council’s historical management of renewals and upgrades was highly reactive due to limited knowledge, strategy, and budget.

To move towards proactive risk management and investment, Council and AECOM prepared the BRC Stormwater Management Strategy (BRCSMS) which enables Council to respond to the challenge of servicing future growth while making provision for the maintenance and augmentation of existing stormwater infrastructure.

The Strategy sets Council’s future direction with actions to manage localised stormwater drainage issues to minimise

the consequences to life, assets, community wellbeing, the environment, and the economy. It also addresses the need to ensure that Council spends money on stormwater infrastructure in the most appropriate areas to demonstrate that Council is actively managing localised stormwater drainage issues, on a risk basis. The Strategy also makes provision for the environmental health of waterways, social amenity, pollution control, affordability and impacts of a changing climate and aligns with Council’s overarching Corporate Plan designed to build Australia’s best regional community.

Challenges Historically, there had been little formal analysis undertaken to determine a strategy to sustain existing stormwater infrastructure by matching future maintenance and renewal expenditure with future income projections. As a result, expenditure was generally reactive, whilst not necessarily reducing overall risk. These and many other challenges faced by Council are summarised below: • Developing an infrastructure pipeline (Councils 1, 3 and 10year Capital Investment Plan); • High demand volumes for customer requests / complaints with finite resources, which are ongoing with or without rain events (and exacerbated by the latter); • What Level of Service does the existing stormwater network provide and is this enough? • Enabling urban growth in a sustainable manner which doesn’t repeat problems of the past; • Balancing budget, risk and performance of the network; • Harnessing new technology in overcoming current and future challenges; • Implementing best-practice water quality treatment and investment; • Ensuring Council is working towards becoming an

Integrated, Water Sensitive City; • Managing de-naturalised, urban creeks and integrating them with the community; and • Proactively managing public safety, infrastructure resilience and environmental protection, now and into the future.

Strategy Justification Effective management of Council’s stormwater network required identification and prioritisation of areas most at risk, exploring levels of service and developing integrated, risk mitigations which offer a range of benefits. The Strategy enables Council to be proactive, forward looking and risk orientated, as shown in Figure 1 below.

The benefits of the Strategy include: • A consistent and transparent approach to identify and prioritise future expenditure.

This will ensure a defendable and balanced approach to progressively reduce risk affecting the community (such as asset failure or flood risk). • Ensuring a level of consensus is reached at all levels of Council by taking them ‘on the journey’ and ensuring they can actively participate in the Strategy development process. • Confirming a commitment to progressively reduce risk with clear actions the community and stakeholders can understand. • Data stocktake and collation, offering Council a GIS database and methods for future use. • Governance provisions and accountabilities clearly outlined. • Budget expenditure can be

forecast in the short and longer term, based on agreed service criteria and risk targets. This will provide more certainty and ensure high risk assets are targeted first and overall risk reduced over time. • All outputs developed to ensure that the Strategy is adaptable and can be continuously improved / realigned.

Objectives The objectives of the Strategy are as follows: 1. Manage stormwater infrastructure in an integrated, sustainable way which prioritises public safety. 2. Demonstrate consistent, longterm risk mitigation and value for money. 3. Incorporate social, cultural, and environmental values in financial investment. 4. Manage demands for growth in line with the Vision. 5. Raise community awareness regarding stormwater management and potential risk. 6. Continuously improve methods and practices.

Stakeholder Engagement

A targeted approach to engagement was used in the development of the Strategy. The Strategy includes the values and perspectives of key stakeholders, with engagement activities focused on Council’s internal staff (managers, technical officers, and maintenance crews) and Councillors, who represent the community voice.

Figure 1. Historical Approach vs This Strategy’s Approach

Technical Working Group Successful delivery of the

Strategy could only be achieved by obtaining broad consensus from the various stakeholders within Council. For this purpose, a Technical Working Group comprising Council staff from various departments was developed to ensure that each stakeholder: • Understands the Strategy. • Has an opportunity to contribute inputs and establish the strategic direction. • Takes ownership of the Strategy and advocates for its outcomes.

Councillor Sessions Early engagement was undertaken with Councillors to present the objectives of the Strategy, gather concerns and establish community expectations regarding the appropriate Levels of Service. To facilitate discussion, the following questions were provided to Councillors prior to meeting in person. 1. What is your vision for stormwater assets for the next 10 years? 2. How does stormwater currently impact the community? 3. What are the key issues impacting Council’s ability to manage stormwater? 4. What are the most important prioritisation factors – safety, environment, social, feasibility, financial, others? 5. What should Council do more of, less of, start doing or stop doing? 6. Levels of service – what are the most valuable metrics from your perspective?

Recurring themes seen throughout the Councillor sessions were: 1. Public safety is paramount. 2. Demonstrate value for money. 3. Community education to management expectations. 4. Address community anxiety. 5. Lack of maintenance resources. 6. Better communication. 7. Holistic approach. 8. Change the approach to CRM’s.

Data Analysis

Customer Request Management (CRM) Council’s Customer Request Management (CRM) system is designed to efficiently manage service requests from the public. The CRM data includes a range of attributes which enabled intuitive analysis of the trends in data, both spatially and temporally. The information captured within the CRM database spans between Jan 2013 and Dec 2019 and included the following primary attributes: • Easting / Northing (parcel centroid). • Date Received (Opened). • Date Completed (Closed). • Category.

Two approaches were employed to extract understanding from the CRMs, which are detailed below.

Temporal Temporal analysis was undertaken with the intent of establishing the relationship (if any) between rainfall and complaints as well as the historic performance in resolution. This was completed by establishing a complaint duration (date completed minus date received) and comparing the frequency of complaints with rainfall events from the regional pluviograph (39128 Bundaberg Aero). The output is shown in Figure 2 below with together with the statistics from the analysis. Based on the analysis, the following key observations were seen: • Base supply of CRMs is independent of rainfall with more than two-thirds received during dry months. • Rainfall results in a short-term 200-300% increase in CRMs received. • The average CRM duration is heavily skewed by a minority (3%) of outliers which remain open for more than 6-months.

Spatiotemporal In addition to the temporal analysis, CRMs were located spatially together with other attributes to understand spatial patterns in complaints, particularly during known rainfall events. This objective of this analysis was to understand the relationship (if any) between predicted flood damage, drainage features (such as pitpipe network, drain or creek) and locale over the captured timeperiod.

Data was converted to a point format and symbolised using a hotspot template which enables construction of a heatmap design to exclude noise (isolated instances) and highlight repeat, clustered occurrences. This analysis was presented to the Technical Working Group during workshops as both an animation and static map to benchmark the findings. A sample of the animation is shown in Figure 3. The exercise confirmed the

Figure 2. CRM Temporal Analysis

following: • Most predicted hotspots aligned with local understanding and experience. • Hotspots follow urban creeks and major tributaries, or older developments that don’t have a formalised stormwater drainage network.

Flood Damage Flood damages have been estimated through the application of stage-damage curves to building footprints based on flood modelling results. These curves provide damage value as a function of water depth and are used to estimate direct flood damages for individual buildings based on the peak flood depth that the building experiences during a flood event.

The assessment has been undertaken using 1% AEP rainon-grid results for the LGA (prepared by BMT in 2019) to establish a comparative assessment of flood damage across the region during local catchment / overland flooding events.

The results of the flood damage assessment were analysed based on cluster density (damage heatmap) and summarised by locality. The heatmap approach for CRMs was adopted for flood damage to filter noise from the assessment (which is important given the preliminary nature of the data) and allowed broader trends to be identified. With reference to Figure 4 and Figure 5, the analysis yielded the following outcomes: • 10 suburbs make up more than 50% of the total damage.

• Bargara and Bundaberg West contribute 20% of the total damage. • Most of the damage is on residential lots, particularly in older localities (such as

Bundaberg West, Norville,

Walkervale etc) where a creek has been historically filled in or adjusted to facilitate development.

Figure 3. CRM Spatiotemporal Animation Sample (Brighter = higher intensity of CRMs)

Figure 4. Flood Damage Hotspots Sample

Figure 5. 1% AEP Tangible Flood Damage per Suburb

• CRM hotspots did not always align with flood damage hotspots. This may be due to the preliminary nature of the analysis, but also indicates a proportion of repeat CRMs may not be related to tangible flood risk.

New/Upgrade Projects Using the local knowledge (collected in technical working group workshops) together with the CRM and flood damage

heatmaps, the team identified Precincts where there were ‘areas showing one or more clusters of unaddressed CRMs, flood damage, maintenance issues or other issues raised through local knowledge’.

At a first pass this process identified a total of 117 precincts which can be managed by Council’s Core Team and updated as datasets develop, and detailed risk analysis is undertaken follow appropriate flood modelling.

Following this, each precinct was investigated at a desktop level to identify the likely cause of flood risk (such as insufficient capacity). Mitigation measures were proposed and costed (such as stormwater infrastructure upgrades) to reduce flood risk, which resulted in a list of potential projects for further detailed assessment for consideration in Council’s 10-year Capital Infrastructure Plan.

Condition Assessment of the Existing Stormwater Network Understanding the current asset condition and inherent risk from the condition is a significant driver to determining a sustainable operational and renewal program, capital works program and a longterm sustainable budget position. Council’s existing stormwater management assets can be broadly divided into three portions: 1. Underground stormwater network – consisting of inlets, access chambers and pipes (of various type, age, and condition). Flood gates, backflow prevention devices and other ancillary infrastructure are also used. 2. Open channels – generally concrete lined or grass lined. 3. Stormwater bunds – consisting of earthen levees of various age.

A Gap Analysis undertaken confirmed several issues associated with Council’s asset management systems and processes. Data relating to the current condition of stormwater

Figure 6. Identification of Precincts to Projects

Figure 7. Risk Assessment Framework Sample – Subsurface Pipes

Figure 8. Risk Assessment Framework Sample – Open Channels

ID Structural Condition score Serviceability condition score Fourth Quantity Estimated Quantity Indicative Cost Project Location

XX00021 5.00 25 10.00 $ 512,200.00 Washpool Creek to Hargreaves St XX00030 5.00 3.00 15 8.00 $ 428,600.00 Pitt St to Creek St XX00022 5.00 3.00 15 8.00 $ 290,800.00 Hargreaves St to Ford St XX00106 5.00 1.00 5 6.00 $ 222,100.00 Moncrieff St culvert XX00105 5.00 1.00 5 6.00 $ 363,300.00 De Gunst St to Moncreiff St

XX00027 5.00 1.00 5 6.00 $ 565,300.00 Boundary St culvert XX00023 5.00 1.00 5 6.00 $ 121,700.00 Approach to Ford St Bridge

XX00025 5.00 1.00 5 6.00 $ 81,300.00 Past Ford St Bridge

XX00028 5.00 1.00 5 6.00 $ 400,900.00 Boundary St to Pitt St

management assets was largely unavailable (outside major road culverts) and separate contracts were called by Council during the development of the Strategy to undertake condition assessments for portions of the underground stormwater network.

Renewals (High Risk Asset Condition) Data from the asset condition assessment was collected and restructured within IPWEA’s risk assessment framework for each asset type (subsurface pipes and open channels). The assets score was set alongside its criticality rating and ranked in order of highest to lowest risk. Extracts of each tool are shown below in Figure 7 and Figure 8. The risk assessment framework provides a ranked list of high priority interventions based on observed risk which is used to inform Council’s future programme of works.

Prioritisation

MCA Framework To help inform Council’s investment, a Multi Criteria Assessment (MCA) Framework was developed to capture the benefits, deficits and costs associated with each project. Ultimately, this framework enables transparent, consistent prioritisation which can be used to inform and justify financial investment in a risk-based manner.

Development of the framework was the most critical part of the process and involves determination of categories and associated weightings based on stakeholder values. To capture stakeholder values and design weightings accordingly, an Analytical Hierarchy Process (AHP) was adopted. This process allows users to assess the relative weight of multiple criteria or multiple options against given criteria using a pairwise approach. This established a consistent way of converting such pairwise comparisons (X is more important than Y) into a set of numbers representing the relative priority of each of the criteria.

The AHP was carried out using the following elements: 1. MCA Workshop with the

Technical Working Group. 2. Discussion to agree on included / excluded criteria. 3. Mentimeter to facilitate anonymous weighting of paired criteria combinations. 4. AHP Calculation tool, which provides an average weighting and associated confidence limits.

The MCA framework was been developed using the criteria and weightings as agreed within the

Key Findings The scoring exercise and MCA tool provided an overall scoring to guide recommendations for stormwater infrastructure by taking into consideration benefits, risk mitigation, deficits and costs of each option using weightings generated from values within the Technical Working Group. Analysis of these

Technical Working Group, presented in Figure 9.

Figure 10. Project Scoring Breakdown

outcomes revealed the following key findings, which can be used to guide future use of the process: • Projects with a broad range of benefits in addition to

Flooding and Public Health &

Safety generally float towards the top of the ranking.

• Most existing projects within the CIP and previous investigations provided limited benefits to flooding or public health and safety, which limits their upper score threshold. • Projects with strong, but isolated benefits generally struggle to move beyond the median score, which supports the case for integrated solutions in line with the

Strategic Vision. • Deficits (e.g. projects with a poor environmental outcome, increased maintenance or low resilience) have a strong effect on the overall ranking of the project.

Levels of Service

As an organisation, Council provides services to its community, some of which are facilitated by infrastructure assets. BRC have acquired infrastructure assets by ‘purchase’, by contract, construction by Council staff and by transfer of assets constructed by developers and others to meet the needs of the community. The goal in managing infrastructure assets is to meet the defined level of service in a risk-based, costeffective manner for present and future consumers.

In addition to infrastructure assets, Levels of Service will also guide the investment in technical resources and initiatives required to achieve the Objectives of the Corporate Plan and community expectations (as provided by the Councillors). Consequently, Levels of Service form a critical element of the Strategy as it justifies a pathway of actions designed to achieve Council’s service to the community.

The Levels of Service Framework has been developed collaboratively between Council departments. The process of establishing the framework involved: 1. Establishing key community values consistently raised by

Councillors. 2. Extracting Strategic Outcomes and Objectives from Council’s

Corporate Plan and Planning

Scheme. 3. Aligning the above items against generalised

Community Levels of Service. 4. Supporting each community value with one or more

Technical Levels of Service. 5. Scoring the current performance of the

Community and Technical

Levels of Service (where possible). 6. Identifying actions and investment required to meet aspirational targets and (ultimately) deliver customer values in accordance with

Council’s Plan. The framework itself is structured to capture seven Customer Values which were derived from the recurring themes discussed during the Councillor Sessions: 1. Health and Safety 2. Community Involvement 3. Responsiveness 4. Sustainability (Environmental

Standards) 5. Functionality 6. Capacity / Utilisation 7. Financial Sustainability

As demonstrated in Figure 11, these Customer Values (e.g. Health and Safety) were used as a foundation to define Customer Levels of Service and Performance Criteria (e.g. Protect Life and Property). These Levels of Service were then linked to a Technical Levels of Service and Performance Criteria (e.g. no above floor flooding during the defined major storm event) and prescribed resources in order to understand Council’s current performance and what needs to be done to achieve the desired Level of Service. Altogether, Council are evaluating performance of the current stormwater network against 31 Technical Level of Service targets, derived from the seven Customer Values.

Figure 11. Strategic Framework Structure

Intervention Triggers

As they currently stand, CRMs present a complex challenge for Council to effectively manage. Some of the challenging elements include: • Most complaints are qualitative. • Many complaints originate from unreasonable expectations. • The base incoming volume of complaints is independent of rain events.

Council is often faced with complaints regarding consistent ‘pain points’, such as: • Civil issues associated with inter-allotment drainage and neighbourhood disputes. • Nuisance flooding, ponding accessibility that doesn’t affect habitable rooms or pose risk to life. • Rural drainage flow paths where landowners don’t want

‘Council’s water’. • Uncontrolled rural erosion and sedimentation (from private landowners). • The sight of stormwater within roads & drainage corridors, with the view that ‘it should all be piped’. • Any breakage within kerb and channel.

To assist in responding to complaints, ‘decision trees’ (Figure 12) have been prepared based on proposed Intervention

Triggers (Table 1). This will provide a consistent guide for managing enquiries and assist Council Staff in identifying how to manage the enquiry, provide clarity for residents on the next steps and how their enquiry will be managed. Improved and consistent use of Customer Relationship Management will help manage expectations and minimise issues escalation to the media and elected representatives.

Table 1. Proposed Intervention Triggers

ID Proposed Criteria Underlying Logic

1 Any instance of above floor flooding / risk to life (including asset failure) Aligns with BRC’s Corporate Plan and Planning Scheme.

2

If nuisance flooding within private property (i.e. not above floor flooding / no risk to life): Depth ≥300mm Post-rainfall ponding water duration is ≥ 24hrs Excluding instances Flood Hazard Class 1 (H1) generated eventual consensus within the Technical Working Group, noting that H1 is accepted within industry as “generally safe for people, vehicles and buildings”. Therefore: H1 maximum flood depth = 300mm. Duration of post-rainfall ponding is based on the time expected for stormwater to stagnate / impact to vegetation.

3 Access to property restricted for ≥ 2 hrs post-rainfall 4 Standing water within BRC assets ≥ 5 days 5 BRC asset (channel, structure or inlet) blocked by ≥ 50%

Longer interruptions to access are expected to significantly increase disruption and associated impacts.

Based on time for mosquitos to breed.

50% blockage based on QUDM design advice.

6

Kerb & Channel blocked by ≥ 50% and/or or vertically displaced by >75mm

Conclusion

To move towards proactive risk management and investment, Council required a forwardlooking

Stormwater Management Strategy to enable response to current and future challenges. The Strategy sets Council’s future direction with a course of action that will manage localised stormwater drainage issues to minimise the consequences to life, assets, community wellbeing, the environment, and the economy. It also addresses the need to ensure that Council spends money on stormwater infrastructure in the most appropriate areas to demonstrate that Council is actively managing localised stormwater drainage issues proactively, on a risk basis.

Figure 12. Proposed CRM Workflow

Acknowledgements

Ben McMaster AECOM Australia Pty Ltd

Dwayne Honor Regional Council

References

AECOM. (2020). Bundaberg Regional Council Stormwater Management Strategy Technical Report. Rockhampton: AECOM Australia Pty Ltd.