Proponents are encouraged to use the tool in its current form, and only unlock it if they have a specific reason (e.g. incorporating bespoke elements, adding more options etc.). For any queries on the use of the tool please contact the Flood Team via floodteam@environment.nsw.gov.au Data and Resources DT01 Flood Damage Assessment and CBA toolzip (22.2 MB) This zipfile contains 2 files. One is the tool without data filled in. One is an example with example data filled in which may help inform implementation of the tool for your particular case. Explore More information Download

Proponents are encouraged to use the tool in its current form, and only unlock it if they have a specific reason (e.g. incorporating bespoke elements, adding more options etc.).

For any queries on the use of the tool please contact the Flood Team via floodteam@environment.nsw.gov.au

The purpose of this tool is to calculate damages associated with flooding and facilitate cost benefit assessments of potential floodplain risk management measures. The tool has been jointly developed by NSW Department of Planning and Environment (Environment and Heritage Group) and NSW Treasury. The tool should be used in conjunction with the Flood Risk Management - Management Measures guideline (MM01) associated with the Flood Risk Management Manual (DPE, 2023). This is found at https://www.environment.nsw.gov.au/research-and-publications/publications-search/flood-risk-management-manual Additional guidance on the use of the tool for CBA and monte carlo elements can be found in the NSW Treasury Guidance at https://www.treasury.nsw.gov.au/finance-resource/guidelines-cost-benefit-analysis Updates to the tool may occur from time to time. A change log will be available with future updates.

Management of flood risks to the community can involve a combination of prevention, preparedness, response, and recovery activities.

The Wellington FRMS 2013 covers the following topics: The Summary and Recommendations preceding this report summarises this report and presents the recommended flood mitigation options for Wellington. Chapter 2 The Wellington Floodplain, describes the existing situation in relation to the physical setting and flood producing mechanism, flood extents and resulting flood damages, transport linkages, planning instruments and the existing flood emergency system. It draws upon previous investigations including the Wellington Flood Study carried out by the Department of Land and Water Conservation (DLWC) in 1995, as well as data supplied by Council and a revised estimate of extreme flood conditions at Wellington. Chapter 3 Flood Planning Levels and Flood Risk Precincts, details the issues which were evaluated in preparing recommendations for the Flood Planning Levels and Flood Risk Precincts. Chapter 4 Status of the 1996 Plan Implementation, contains an assessment of the progress of the implementation of the 1996 FRMP. Chapter 5 Potential Floodplain Management Measures, presents an appraisal of potential measures which may be incorporated in the FRMP. Chapter 6 Selection of Floodplain Management Measures, outlines a range of considerations to be taken into account in the selection of the mix of measures recommended for inclusion in the FRMP. Chapter 7 The updated Flood Risk Management Plan 2013, summarises the recommended elements for inclusion in the FRMP and provides information on funding and implementation. Several technical appendices have been prepared which provide background information: Appendix A A description of the flood conditions in the Macquarie and Bell Rivers, including review of the 1995 Flood Study and the results of additional hydraulic modelling undertaken for the 2013 study Appendix B A review of the effects of Burrendong Dam in attenuating floods Appendix C An assessment of urban flood damages in Wellington Appendix D An appraisal of existing emergency management procedures Appendix E Recommended amendments to Wellington LEP 2012 and DCP 2013 Appendix FReport on the Aspley Drainage Study Appendix G Background to the selection of floodplain management measures Appendix H Candidates for Voluntary Purchase and House Raising Schemes

INTRODUCTION

In recent years, small duration heavy intensity rainfall events associated with thunder storms have shown that the Griffith Aerodrome and associated infrastructure are exposed to some potentially destructive, and certainly disruptive, flood risk. In order to quantify the flood risk and then to propose measures which may protect the aerodrome and associated facilities in the event of a flood, Griffith City Council (GCC) have appointed WMAwater to carry out a flood study. The Department of Environment, Climate Change and Water (DECCW) is providing financial assistance towards the flood study.

The main objective of this study is to:

• Define the overland flow flood behaviour within the aerodrome catchment (refer to Figure 1 for the location of the study area). The principle focus is on those buildings that adjoin the aerodrome facility, i.e. hangers and administrative buildings, as well as the runway itself, and
• Preliminary assessment of mitigation measures.

The study seeks to establish suitable hydrologic and hydraulic model tools, demonstrate their capacity to emulate local flood behaviour via calibration/validation (as data allows) and then apply these tools to establish the existing flood risk for a range of design flood event probabilities in conjunction with a range of event durations. Following design flood modelling for the existing conditions, a damages assessment for the aerodrome will be carried out. The above work will establish the flood liability of the aerodrome under exisiting conditions.

The model will then be utilised to test preliminary mitigation measures. Mitigation measures will seek to reduce the degree of inundation of the aerodrome and associated infrastructure and therefore reduce the flood damages associated with an extreme event. Mitigation options could potentially be quite varied however two that spring to mind in this case are detaining flood water upstream of the aerodrome or diverting it prior to its entry into the aerodrome area.

This report details the investigations, results and findings of the Flood Study. The key elements of which include: * a summary of available data; * model development; * calibration of the hydraulic model; * definition of the design flood behaviour for existing conditions through the analysis and interpretation of model results; and * testing limited mitigation options.

A flood study of the Newport Beach catchment has been undertaken to define the nature and extent of flooding in the area for a range of design rainfall events. The study has been carried out for the existing catchment conditions. The study was first completed in November 1999. This revision to the Newport Beach Flood Study incorporates new topographic survey data for the purpose of more accurately representing the flow regimes in critical areas of the catchment. Refinements to the modelling systems utilised include the revision of the North, Robertson Road and Barrenjoey Road branches of the hydraulic model, as well as re-schematisation of the North branch, Barrenjoey Road and West branch confluence. Additional flow paths were also incorporated for Howell Close, Foamcrest Avenue and Coles Parade. The hydraulic model (MIKE11) was also transferred and upgraded to a newer release of software. The Newport Beach catchment has an area of 1.79 square kilometres. The catchment is fully urbanised with residential and commercial land uses. Floodwaters from the catchment accumulate near the commercial area and discharge into the ocean. In the past many major flooding events have occurred, which have caused extensive damage to public and private property, restricted access and have been a general inconvenience to the residents. Above-floor flooding in the lower reaches of the catchment caused extensive damage during the events of March 1977, October 1987 and May 1988. Estimation of flooding behaviour was undertaken by developing two mathematical models to simulate the hydrologic and hydraulic aspects of flooding. The hydrological modelling package RAFTS (1994) was utilised to determine catchment runoff and for routing flows downstream through the catchment. Predicted hydrographs from RAFTS were then input to the hydraulic model MIKE-11 (2000) for the determination of peak flood levels, velocities and flood extents for various design rainfall events. These events included the 1%, 2%, 5%, 20% annual exceedance probability events (AEP) together with the Probable Maximum Flood (PMF). Both surface and trunk drainage pipe flows were modelled. Three historical flood events were selected for calibration and validation. The flooding events were chosen on the basis of flood level information obtained from the resident survey and the available rainfall data. Design rainfall intensities and temporal patterns for the required rainfall events were obtained from Australian Rainfall and Runoff (1987). The model results reflect the observed flooding regime of the area. The area adjacent to the main concrete lined drain in the lower portion of the catchment is severely affected. This area includes commercial areas on Barrenjoey Road, residential areas in Ross Street and Council’s car park near Bramley Avenue. Barrenjoey Road is also flooded where it intersects the main drain near The Boulevard for design storm events with a frequency of 20% AEP and rarer. The impact of ocean water levels on flooding was considered. The results indicate that catchment flooding is insensitive to the ocean water levels. Only during rare and very severe floods is ocean water level likely to impact on drainage capacity and cause a small increase in flood level. However, it is important to note that flooding is also possible as a result of ocean inundation by wave overtopping of the frontal dune. This flooding mechanism is not considered in this report. Limits of predicted flooding extents for the PMF, 1% AEP, 2% AEP, 5% AEP and 20% AEP events and the 1% AEP + 0.5m extent are provided on a cadastral plan. Tabulated modelling results, which include predicted flood levels, velocities and flows at a number of locations in the floodplain, are also provided. This study provides the management tool in the form of a hydraulic model for assessing floodplain management options in the study area under the next stage of the Floodplain Management Process - the Floodplain Risk Management Study.

Bewsher Consulting Pty Ltd was originally commissioned by Liverpool City Council, in\r conjunction with Fairfield City Council and the Department of Land and Water\r Conservation (now the Department of Infrastructure, Planning and Natural Resources),\r to undertake a floodplain management study for Cabramatta Creek.\r \r A number of working papers were prepared during the course of the study and a draft\r main report issued in May 1999 [Bewsher Consulting, 1999].\r \r The draft report was not finalised at the time, largely due to uncertainties associated\r with a major highway proposal (referred to as the WSO project in this report) that\r bisects the Cabramatta Creek catchment. The proposed highway and associated\r compensatory flood mitigation works has a significant impact on Liverpool Council’s\r detention basin strategy – in particular, whether or not an earlier proposal to construct a\r large multi-purpose basin in the middle of the catchment, known as Basin 22, would\r be feasible.\r \r By late 2002 many of the uncertainties regarding the proposed WSO and Basin 22 had\r been resolved. Subsequently, Liverpool and Fairfield Councils requested that the draft\r Cabramatta Floodplain Management Study be updated.\r \r This floodplain management study and plan is based on the previous draft report\r submitted in May 1999, updated where appropriate to account for changes that have\r occurred since this time.\r \r Bewsher Consulting has been assisted by Don Fox Planning (town planning advice), the\r University of NSW Water Research Laboratory (hydraulic modelling), Nelson Consulting\r (environmental matters) and Southern Aerial Surveys (aerial mapping).\r \r The study was overseen by both Liverpool Council’s floodplain management committee\r and Fairfield Council’s floodplain management committee. These committees consisted\r of Councillors and staff from both Councils, community representatives, and officers\r from other organisations, such as the Department of Land and Water Conservation\r (now DIPNR), State Emergency Services and the Department of Urban Affairs and\r Planning.\r \r

Principal Outcomes\r

The outcomes of this study include:\r \r - a comprehensive set of aerial photography and detailed contour mapping of the\r catchment;\r - revised flood information in the form of maps showing flood contours and flood\r extents for a range of flood events, in digital format for incorporation into both\r Councils’ GIS computer systems and as hard copy plans;\r - a comprehensive assessment of floodplain management measures, including a\r review of planning controls, flood mitigation works and other measures to reduce\r potential flood problems within the catchment;\r - a range of working papers on specific issues investigated throughout the study,\r which have been progressively presented to the floodplain management\r committees;\r - the Main Report (this document) which summarises the working papers that have\r been undertaken, and presents an overall outline of the floodplain management\r study and the recommended floodplain management plan; and\r - an Executive Summary which provides a concise summary of the study and\r recommended floodplain management plan.\r

Flood Behaviour\r

Flood behaviour has been analysed using the RAFTS hydrologic model to simulate\r flows throughout the creek systems, and the RMA-2V two dimensional hydraulic model\r to simulate the extent and depth of flooding within the catchment. Both models were\r calibrated to floods that were recorded in August 1986 and April 1988. These models\r provide the necessary tools to assess the impact of catchment development,\r compensatory flood mitigation works, and other potential flood mitigation works to\r alleviate existing flooding problems.\r \r The floodplain has been divided into three flood risk precincts (high, medium and low)\r as part of the updated study. Different development controls are also proposed for the\r catchment depending on the type of development and the flood risk precinct that the\r development is located. These controls are included in a planning matrix to be attached\r to Flood Risk Management Development Control Plans that have been proposed for\r both Liverpool and Fairfield Councils.\r \r A flood damages database of potentially flood affected properties has been prepared as\r part of the study. The database provides details of those properties likely to be\r inundated in different sized floods and allows the quantification of potential flood\r damages. Key results from the database indicate that:\r \r - 2,838 residential homes and 218 commercial/industrial buildings would be flooded\r above floor level in the PMF;\r - In the Liverpool LGA, 74 homes and 80 commercial/industrial buildings would be\r flooded above floor level in the 100 year flood;\r - In the Fairfield LGA, 50 homes and 24 commercial/industrial buildings would be\r flooded above floor level in the 100 year flood;\r - The predicted flood damage in the 100 year flood is $16M for Liverpool, and $4.8M\r for Fairfield.\r

Community Consultation\r

Community consultation has also been a major component of the study. This has\r included liaison with community groups and authorities, regular presentations to both\r Councils’ floodplain management committees, two community newsletters and\r questionnaires, two public meetings, and the intended public exhibition of the draft\r Main Report and Executive Summary.\r \r \r

The Floodplain Management Plan\r

A recommended floodplain management plan showing preferred floodplain\r management measures for Cabramatta Creek is presented in Table 11.1 and also\r shown on Figure 11.1. The preferred measures have been determined from a range of\r available measures, after an assessment of the impacts on flooding, as well as\r environmental, social, and economic considerations.\r Recommended options that modify flood behaviour include:\r \r - a revised detention basin strategy for Liverpool City Council;\r - three other detention basins to provide compensatory flood storage for the proposed\r WSO highway;\r - a further detention basin on Brickmakers Creek at Amalfi Park and/or channel\r improvement measures downstream of Amalfi Park;\r - channel works, culvert amplification, and creek rehabilitation works in Brickmakers\r Creek, between Homepride Avenue and Elizabeth Drive;\r - improved flood access along major arterial roads;\r - a package of works in the Elizabeth Drive/Tresalam Street area; and\r - the preparation of bushland management plans and the clearing of rubbish and\r debris from the creek waterways.\r \r Recommended options that modify property include:\r \r - voluntary house raising;\r - flood proofing individual buildings; and\r - controls on new development through a planning matrix approach, which provides\r guidance on appropriate land uses and other development controls.\r \r Recommended options that modify people’s response to flooding include:\r \r - a flood awareness program;\r - improved flood warning system and emergency response management; and\r - the preparation of flood action plans.\r

Timing and Funding\r

Timing of the proposed works will depend on each Council’s overall budgetary\r commitments, and the availability of funds from other sources. Funding will be\r available through a number of sources, as identified in Table 11.1. Components of the\r Plan will be able to be carried out directly by either Liverpool Council or Fairfield\r Council, whilst other components that affect both Council areas will need to be carried\r out jointly.

Introduction Cessnock City Council (Council) to commissioned a Floodplain Risk Management Study (FRMS) and a Floodplain Risk Management Plan (FRMP) for the Black Creek Catchment. This FRMS has been …Show full descriptionIntroduction Cessnock City Council (Council) to commissioned a Floodplain Risk Management Study (FRMS) and a Floodplain Risk Management Plan (FRMP) for the Black Creek Catchment. This FRMS has been undertaken to define the existing flooding behaviour and associated hazards and to investigate possible management options to reduce flood damage and risk. A number of floodplain management options have been examined as part of this FRMS to manage flooding within the Black Creek Catchment. The identification and examination of these options was done in accordance with the NSW Floodplain Development Manual: The Management of Flood Liable Land (NSW Government, 2005). The FRMP (Chapter 15) represents the proposed implementation plan of actions for the management of flood risks in the Black Creek Floodplain. Purpose The purpose of the study is to: Review Council’s existing environmental planning policies and instruments including Councils longterm planning strategies for the study area; Identify works, measures and restrictions aimed at reducing the social, environmental and economic impacts of flooding and the losses caused by flooding on development and the community, both existing and future, over the full range of potential flood events; Assess the effectiveness of these works and measures for reducing the effects of flooding on the community and development, both existing and future; Consider whether the proposed works and measures might produce adverse effects (environmental, social, economic or worsened flooding) and whether they can be minimised; Inform the amendment and/or preparation of planning policies relating to flood risk management; Examine the present flood warning system, community flood awareness and emergency response measures in the context of the NSW State Emergency Service's development and disaster planning requirements; Identify modifications that are required to current policies in light of the investigations. The purpose of the plan is to set out the proposed approach to implementation of actions to be undertaken to manage flood risks. Project Objectives The specific objectives of the study and plan are to: Identify measures to reduce the flood hazard and risk to people and property in the community in the present day, and to ensure future development is controlled in a manner consistent with the flood hazard and risk; Identify measures to reduce private and public losses due to flooding; Where possible, identify measures to protect and enhance waterways and the floodplain environment; Be consistent with the objectives of relevant state policies, in particular, the Government’s Flood Prone Land and State Rivers and Estuaries Policies and satisfy the objectives and requirements of the Environmental Planning and Assessment Act 1979; Recommend actions for incorporation in the floodplain risk management plan to reduce flood risk; Ensure actions recommended for incorporation in the floodplain risk management plan are sustainable in social, environmental, ecological and economic terms.

This study investigates floodplain management issues for the village of Molong within the Cabonne local government area. Molong is situated adjacent to Molong Creek in the central west of New South Wales, about 35 km north west of Orange. This report has identified practical measures to minimise the impacts that floods have on the community. A range of possible measures was examined to find those most suited to Molong based on economic, technical, social and environmental criteria, and the likely level of community support for each measure. As a result of this process, a Draft Floodplain Management Plan for Molong has been prepared. The principal aim of this Floodplain Management Study is to develop a Floodplain Management Plan for Molong that addresses the existing, future and residual flood problems. Key components of this study have included: collection and review all previous reports, surveys and maps relevant to the study; development and implementation of a community consultation strategy, to ensure community input is obtained at key times throughout the study; identification of the existing flood behaviour, flood problems, the flood hazards and the cost to the community that can be expected from flood damage; review of the existing land use within the study area, having regard to the flood hazard; review of the existing framework of planning and development controls that are relevant to formulation of planning instruments and assessments of building and development applications.

NRRA requested surge team to develop a means to produce a defensible, evidence-based estimate of total economic impact of disasters for the recent flood events in Northern NSW and southern Queensland in February and March 2022 . Although the primary objective was to be quantify the total economic impact for the entire flood event, the team developed an approach that would enable estimation of value at risk and value impacted at higher spatial resolution or granularity that could also be used to inform policy and program design.

The aim was to develop a minimum viable product (MVP) for immediate use by the NRRA.

An approach was developed to estimating economic value at risk for administrative areas and then use flood extent to calculate percent of each administrative area impacted by the hazard, to estimate economic value impacted. Gross Value Added (GVA) by each administrative area (ASGS SA2 level) was selected as the headline economic value at risk figure. The GVA for each administrative area can be aggregated to a headline figure of total economic impact. The approach was intended to be rapid and robust, and to provide a preliminary view of direct impacts soon after a disaster occurs.

The outputs include:

A) An Economic value-at-risk data stack (including a range of economic data - jobs, productivity by worker, property reconstruction value, inter-regional and sectoral economic activity and built environment data)

B) A calculation sheet to calculate value impacted based on value at risk (GVA) and input parameters to quantify hazard within each administration unit

Both outputs are contained within a Microsoft Excel document.

Acknowledgement: This publication was developed by the CSIRO on behalf of the Australian Climate Service, a Type F Commonwealth entity hosted by the Bureau of Meteorology and delivered through a partnership between the Bureau of Meteorology, Australian Bureau of Statistics, CSIRO and Geoscience Australia.

Important disclaimer: CSIRO advises that the information contained in this publication comprises general statements based on scientific research. The reader is advised and needs to be aware that such information may be incomplete or unable to be used in any specific situation. No reliance or actions must therefore be made on that information without seeking prior expert professional, scientific and technical advice. To the extent permitted by law, CSIRO (including its employees and consultants) excludes all liability to any person for any consequences, including but not limited to all losses, damages, costs, expenses and any other compensation, arising directly or indirectly from using this publication (in part or in whole) and any information or material contained in it. Lineage: 1.\tData collection  •\tDiscussion around potentially relevant data with ABS and GA •\tSubsequent requests for data from data providers GA and ABS 2.\tData wrangling, cleansing, integration, formatting, etc.  •\tData stack architecture built in r and reproduced in Excel format  •\tFully integrated data structure for all of Australia by SA2 by year produced from all available data (note that not all geographies or years were available for all metrics) •\tCreation of full data list including source, type, description, geography, time period(s), and format(s) of data included in the data cube 3.\tIdentification of Gross Value Added (GVA) as headline ‘economic value at risk’ indicator   •\tGVA represents the value of goods and services produced minus intermediate consumption (i.e. the value of inputs into their production such as raw materials, rent, and labour costs).  •\tGVA per worker per industry was only available at the LGA level. Using the count of workers per industry per SA2, an estimate of total GVA per industry per SA2 was calculated using the LGA GVA per worker data applied to all SA2s within the given LGA. Where SA2s were split between LGAs, a weighted average GVA per worker by industry was calculated, with weighting related to the percentage of SA2 land area in the relevant LGAs.  •\tGVA informs the calculation of Gross Regional Product, but excludes the influence of taxes and subsidies.  4.\tSelection and analysis of relevant data  •\tCalculation of GVA per industry per SA2  •\tSelected data taken from most recent year available  5.\tIntegration of ‘% of impacted land’ as an input function 6.\tInput flood extent table by % of each SA2 to calculate annual economic value at risk in $m (real) 

The flood risk in many urban catchments is poorly understood. Legacy stormwater infrastructure is often substandard and anticipated climate change induced sea level rise and increased rainfall intensity will typically exacerbate present risk. In a Department of Climate Change and Energy Efficiency (DCCEE) funded collaboration between Geoscience Australia (GA) and the City of Sydney (CoS), the impacts on the Alexandra Canal catchment have been studied. This work has built upon detailed flood hazard analyses by Cardno commissioned by the CoS and has entailed the development of exposure and vulnerability information. Significantly, the case study has highlighted the value of robust exposure attributes and vulnerability models in the development of flood risk knowledge.

The paper describes how vulnerability knowledge developed following the 2011 Brisbane floods to include key building types found in the inner suburb of Sydney. It also describes the systematic field capture of building exposure information in the catchment area and its categorisation into 19 generic building types. The assessment of ground floor heights using the Field Data Analysis Tool (FiDAT) developed at Geoscience Australia is also presented.

The selected hazard scenario was a 100 year ARI event with 20% increased rainfall intensity accompanied by a 0.55m sea level rise in Botany Bay. The impact from the selected scenario was assessed in terms of monetary loss for four combinations of vulnerability model suite (GA and NSW Government) and floor height attribution method (assumed 0.15m uniformly and evaluated from LiDAR and street view imagery).

It was observed that the total loss is higher in the case of assumed floor heights compared to FiDAT processed floor heights as the former failed to capture increased floor heights for newer construction. However, the loss is lower when only two vulnerability models developed by NSW Government are applied for the entire building stock in the region as two models could not reliably represent the whole building stock.

The township of Henty is located in the Greater Hume Shire Local Government Area situated in the Riverina region of southern New South Wales. It has a population of 882 people (2011 census) and is located on the Olympic Highway, 17km north of Culcairn. \r \r FRMS objectives:\r \r * Review of Council’s existing environmental planning policies and instruments including Council’s long term planning strategies for the Study Area;\r * Obtain damage estimates under the range of design floods mentioned under existing conditions;\r * Identification of works, measures and restrictions aimed to reduce the social, environmental and economic impacts of flooding and the losses caused by flooding on development and the community, both existing and future, over the full range of potential flood events;\r * To assess the effectiveness of the works and measures for reducing the effect of flooding on the community and development, both existing and future;\r \r FRMP objectives:\r \r * Reduce the flood hazard and risk to people and property in the community and to ensure future development is controlled in a manner consistent with the flood hazard and risk;\r * Reduce private and public losses due to flooding;\r * Protect and, where possible, enhance watercourses/creeks and floodplain environment;\r * Be consistent with the objectives of relevant State policies, in particular, the Government’s Flood Prone Lands and State Rivers and Estuaries Policies and satisfy the objectives and requirements of the Environmental Planning and Assessment Act, 1979;

Cardno was commissioned by Wingecarribee Shire Council to undertake a Floodplain Risk Management Study and Plan (FRMSP) for the Burradoo BU2 Catchment. This FRMSP has been prepared to define the existing, future and continuing flood behaviour and associated hazards, and to investigate possible management options to reduce flood damage and risk. It has been prepared in accordance with the NSW Government Floodplain Development Manual (2005).

Burradoo BU2 Catchment is a sub-catchment of Mittagong Creek which is a tributary of the Wingecarribee River. The total catchment area is approximately 244 hectares within the suburb of Burradoo with land use being predominantly rural-residential. Figure 1-1 shows the general location of the Catchment.

The Burradoo BU2 Catchment Assessment Study – Stage 1 Flood Study Report was prepared by Cardno in 2010. The Flood Study defined flood behaviour in the Catchment under existing and future climate change conditions for the 20% AEP, 5% AEP, 2% AEP, and 1% AEP events and the Probable Maximum Flood (PMF).

Study Objectives

The overall objective of this study was to assess flooding risk, investigate floodplain risk management options and develop a management plan that addresses the existing and future flood risk and minimises the continuing flood risk in the Burradoo BU2 Catchment. This was undertaken in accordance with the NSW Government's Flood Prone Land Policy as detailed in the Floodplain Development Manual (2005). Objectives of the Burradoo BU2 Floodplain Risk Management Study and Plan were to:

• Ensure that the most up-to-date flood-related information is available within the study area to investigate existing, future and continuing flood behaviour including consideration of potential catchment and climate change conditions as well as hydraulic and true hazard categories and the continuing risk for the community.
• Review Council’s existing environmental planning policies and instruments, including Council’s long term planning strategies for the study area.
• Identify works, measures and restrictions aimed at reducing the social, environmental and economic impacts of flooding and the losses caused by flooding on development and the community, both existing and future, over the full range of potential flood events. Innovative solutions to the management of the flood hazards within the study area were being sought, along with effective community consultation and participation throughout the Study.
• Evaluate the effectiveness of these works and measures for reducing the effects of flooding on the community and development, both existing and future. It also considered the social, environmental and economic impact of these measures.
• Examine and recommend measures to improve community flood awareness and emergency response measures in the context of the NSW State Emergency Service's developments and disaster planning requirements.
• Undertake risk category mapping based on four zones (High, Medium, Fringe Low and Low) in line with Bowral Floodplain Risk Management Study and Plan (Bewsher Consulting, 2004).

Report Outline

In order to achieve the objectives above, the report is outlined as follows:

• Community consultation (Section 3);
• Environmental and social characteristics of the catchment (Section 4);
• Defining the existing flood behaviour, including flood levels, depths, velocities, hazard zones and hydraulic categories (Section 5);
• Assessment of economic impact of flooding (Section 6);
• Review of current emergency response arrangements (Section 7);
• Review of development controls (Section 8);
• Assessment of floodplain risk management options (Section 9);
• Economic assessment of flood management options (Section 10);
• Multi-criteria assessment of flood management options (Section 11); and
• Floodplain risk management plan (Section 12).

This study summarises the available information relating to flooding in the three townships of\r Murrurundi, Blandford and Willow Tree. It describes the physical setting and flood producing\r mechanisms, identifies the flood extentand the resulting flood damages for floods of various average\r recurrence intervals (ARI). The transport linkages, planning instruments and the eXisting flood\r emergency system are also examined. The study draws upon previous investigations including the\r Murrurundi, Blandford and Willow Tree Flood Study completed in 1997 by Lyall & Macoun Consulting\r Engineers, as well as historic flood data supplied by Council.\r Detailed analysis of flood flows and levels throughout the three townships together with a survey of\r the floor level of each building within the floodplain indicates that most of the properties affected by\r flooding are located in Murrurundi. Table S-1 summarises the numbers of properties within each\r township which are "affected" by the 100 year ARI flood. These are shown in column A and include\r properties where flood water is on the land as well as those where flood water is above floor level.\r Also shown, in column 0, are the numbers of properties which are "damaged", that is, flood water\r above floor level.

The township of Culcairn is located in the Greater Hume Shire Local Government Area situated in the Riverina region of southern New South Wales (NSW). GHSC is surrounded by the LGA’s of Wagga Wagga, Urana, Tumut, Corowa, Tumbarumba, Albury and Indigo. The main objective of this FRMS&P is to identify floodplain risk, test amelioration strategies for the management of risk and to put forward priorities and approximately costed recommendations in regards to flood risk mitigation at Culcairn.\r \r FRMS objectives:\r \r * Review of Council’s existing environmental planning policies and instruments including Council’s long term planning strategies for the Study Area\r * Obtain damage estimates under the range of design floods mention under existing conditions\r * Identification of works, measures and restrictions aimed to reduce the social, environmental and economic impacts of flooding and the losses caused by flooding on development and the community, both existing and future, over the full range of potential flood events\r * To assess the effectiveness of the works and measures for reducing the effect of flooding on the community and development, both existing and future\r \r FRMP objectives:\r \r * Reduce the flood hazard and risk to people and property in the community and to ensure future development is controlled in a manner consistent with the flood hazard and risk\r * Reduce private and public losses due to flooding\r * Protect and, where possible, enhance watercourses/creeks and floodplain environment\r * Be consistent with the objectives of relevant State policies, in particular, the Government’s Flood Prone Lands and State Rivers and Estuaries Policies and satisfy the objectives and requirements of the Environmental Planning and Assessment Act, 1979

The Wellington FRMS 2013 covers the following topics:

The Summary and Recommendations preceding this report summarises this report and presents the recommended flood mitigation options for Wellington.

Chapter 2 The Wellington Floodplain, describes the existing situation in relation to the physical setting and flood producing mechanism, flood extents and resulting flood damages, transport linkages, planning instruments and the existing flood emergency system. It draws upon previous investigations including the Wellington Flood Study carried out by the Department of Land and Water Conservation (DLWC) in 1995, as well as data supplied by Council and a revised estimate of extreme flood conditions at Wellington.

Chapter 3 Flood Planning Levels and Flood Risk Precincts, details the issues which were evaluated in preparing recommendations for the Flood Planning Levels and Flood Risk Precincts.

Chapter 4 Status of the 1996 Plan Implementation, contains an assessment of the progress of the implementation of the 1996 FRMP.

Chapter 5 Potential Floodplain Management Measures, presents an appraisal of potential measures which may be incorporated in the FRMP.

Chapter 6 Selection of Floodplain Management Measures, outlines a range of considerations to be taken into account in the selection of the mix of measures recommended for inclusion in the FRMP.

Chapter 7 The updated Flood Risk Management Plan 2013, summarises the recommended elements for inclusion in the FRMP and provides information on funding and implementation.

Several technical appendices have been prepared which provide background information:

Appendix A A description of the flood conditions in the Macquarie and Bell Rivers, including review of the 1995 Flood Study and the results of additional hydraulic modelling undertaken for the 2013 study

Appendix B A review of the effects of Burrendong Dam in attenuating floods

Appendix C An assessment of urban flood damages in Wellington

Appendix D An appraisal of existing emergency management procedures

Appendix E Recommended amendments to Wellington LEP 2012 and DCP 2013

Appendix FReport on the Aspley Drainage Study

Appendix G Background to the selection of floodplain management measures

Appendix H Candidates for Voluntary Purchase and House Raising Schemes

Objectives\r

The objective of this Study is to define the nature of the existing flood behaviour in the\r Burradoo BU2 catchment.\r To achieve the objective, the following tasks were undertaken:\r \r * Collate available flood-related data,\r * Define existing catchment condition flood behaviour for mainstream flooding in the\r catchment,\r * Define design flood levels, velocities and flow distributions for the catchment,\r * Define the extent of flooding the 5 year, 20 year, 50 year, and 100 year ARI and PMF\r events for the catchment,\r * Define provisional flood hazard for the flood-affected areas,\r * Define the hydraulic categories for the flood-affected areas,\r * Assess impacts of climate change,\r * Preliminary assessment of flood damages for the flood-affected areas,\r * Identify preliminary remedial options.\r \r

Methodology\r

This Study was carried out using computer-based hydrologic and hydraulic modelling.\r Two numerical modelling tools were developed:\r \r * A hydrologic model was utilised to convert rainfall on the catchment to runoff. The\r hydrologic model RAFTS was used, which combines rainfall information with local\r catchment characteristics to estimate runoff hydrographs.\r * A hydraulic model was utilised to convert runoff hydrographs into water levels and\r velocities in the study area. The model simulates the hydraulic behaviour of the water\r within the study area by accounting for flow in the major channels as well as potential\r overland flowpaths, which develop when the capacity of the channels is exceeded. It\r relies on boundary conditions, which were the runoff hydrographs produced by the\r hydrologic model and downstream boundary conditions from the creek into which it\r discharges. The TUFLOW modelling system was used for this purpose.\r \r The Study details are grouped together under the following sections of the report:\r \r * Section 3 provides a general description of the catchment\r * _ Section 4_ discusses the content and sources of relevant data, which were utilised for\r the study. Historical rainfall and flood data used in the calibration of the established\r hydrologic and hydraulic models and survey data used are detailed.\r * Section 5 discusses the catchment characteristics and describes the hydrologic model\r setup for the study.\r * Section 6 describes the hydraulic model utilised for the study, its verification and\r subsequent use for design rainfall events.\r * Section 7 details results for the design flood events.\r * Section 8 reviews the sensitivity of the model to the data used.\r * Section 9 identifies the provisional flood hazard.\r * Section 10 identifies the hydraulic categorisation.\r * Section 11 reviews the impacts of climate change.

The Mona Vale - Bayview Catchment has a total area of approximately 5.2km2 with two major sub-catchments subdividing the catchment into the Mona Vale Drain subcatchment of 1.6km² and the Cahill Creek catchment at Bayview of. 3.6km². A large proportion of the catchment is urbanised with a mix of residential, commercial, light industrial and a smaller proportion of forested areas. Bayview Golf Course is a major feature of the Cahill Creek floodplain. Flooding in the Mona Vale - Bayview floodplain has historically resulted in inundation of and damage to, private and commercial property and has restricted road and property access. The recognition of these flooding issues has prompted Pittwater Council, through the Pittwater Coastal, Estuary and Floodplain Management Committee to prepare a Flood Risk Management Plan for the Mona Vale - Bayview floodplain. The Mona Vale - Bayview Flood Study is the first part of the Flood Risk Management process, which aims to reduce the impact of flooding and flood liability for flood prone land in the catchment. A flood study of the Mona Vale - Bayview floodplain was undertaken to determine the existing flood behaviour of flood prone areas for a range of flood risk levels from the 20% Annual Exceedance Probability (AEP) event through to the Probable Maximum Flood (PMF). Data has been collated for the Flood Study from a variety of sources. This information includes data describing historical flood behaviour that has occurred on the floodplain and data essential for the development and verification of the hydrologic and hydraulic modelling tools. The advice of the local residents ·of the floodplain was sought via a community newsletter and survey circulated in January 2001 for the purpose of collecting historical flood information and community opinion regarding flooding and drainage on the floodplain. Design rainfall intensities and temporal patterns for the required range of flood risk events were obtained from 'Australian Rainfall and Runoff', Institution of Engineers Australia, (2001) and 'The Estimation of Probable Maximum Precipitation in Australia: Generalised Short-Duration Method,' Bureau of Meteorology (1994). Flood behaviour was determined for flood prone areas using mathematical modelling tools developed specifically for the study. Catchment runoff was estimated using the hydrological model, RDII, DHI (2001). Predicted catchment flows from the RDII model along with tide levels for the Pittwater were then used as boundary conditions to the hydraulic model MIKE11, DHI (2001), for the determination of flood levels, flows and velocities in the flood prone areas. The models were calibrated to the April 1998 flood event, which was considered the most suited event for model calibration because of available rainfall and· historical flood records (Pittwater Council). The models were verified using the October 1987 and January 1989 flood events. The flood model predictions indicate that in many areas of the floodplain the capacity of existing flow channels, major piped stormwater drainage conduits and road culverts are exceeded resulting in overland flooding for a range of simulated flood events. In the Cahill Creek catchment, overland flood flows occur in the WaIter Road area at shallow depths for the 20% AEP and larger flood events. Overland flooding may also occur when the Peninsula Gardens Detention Basin capacity is exceeded with flood flows passing through several residential properties in Old Samuel Street, Samuel Street and Parkland Road. If the basin outlet remains unblocked, the basin capacity is predicted to be exceeded for events greater than the 5% AEP flood event. Should the basin outlet become completely blocked, flooding of properties downstream of the basin would occur for all the design events tested. While blockage of the basin outlet by debris has exacerbated flooding in past flood events, there is evidence to suggest that blockage of the outlet has not been an issue for every historical flood. Design flood levels presented for the basin in this report are for the unblocked case. Further downstream on the Cahill Creek floodplain, the Bayview Golf Course and several properties along its periphery in Kunari Close and Parkland Road are predicted to be inundated. Parkland road and Cabbage Tree Road are predicted to be impassable to traffic in several locations under 1% AEP conditions. Pittwater Road is predicted to be inundated for events greater than 1% AEP on the southern side of the floodgates on Cahill Creek. In the Mona Vale Drain catchment, property flooding is predicted to occur in Darley St East, Seabeach Avenue, Heath Street and Bassett Street on the eastern side of Barrenjoey Road due to flows exceeding the capacity of the existing stormwater drainage system for events including the 20% AEP event and greater. On the western side of Barrenjoey Road, the light industrial area is likely to be flooded for events including the 20% AEP flood event and greater when the capacity of the open channel behind Polo Avenue is exceeded. Anecdotal evidence suggests that the culverts at the downstream end of the open channel behind Polo Avenue block each time there is a storm event with a combination of rubbish, reeds and sediment. The design flood levels are presented in this study with the culverts on the downstream end of the Polo Avenue open channel blocked to approximately 5% of their total capacity. All other stormwater pipes and culverts are modelled at 100% capacity for the presented design flood levels. Inundation plans showing the approximate extent of flooding for the 1% AEP, 2% AEP, 5% AEP 20% AEP and the PMF events are included as Appendix D (Volume1). Tabulated model results are also provided for reference in Appendix I (Volume 2). These results quantify the predicted existing flood behaviour in terms of flood level, flood depth, flow distribution and flow velocity. The developed flood modelling tools and reported flood behaviour for existing catchment conditions can be used as the basis for developing a Flood Risk Management Plan for the floodplain. The hydraulic model developed for the flood study may generally be used to assess the hydraulic impact of any proposed structural flood mitigation works on flood behaviour. However the suitability of the model to assess individual options should be assessed.

The Wallsend-Plattsburg catchment, located in Newcastle’s western suburbs, covers an\r area of approximately 12.4 km2 (see Figure 1). Catchment elevation varies from 42m to\r Australian Height Datum (AHD) near Rankin Park to 0.5m AHD on the Hexham\r Swamp side of Minmi Road. The catchment is drained by Ironbark Creek and its\r tributary streams and collects runoff from the suburbs of Rankin Park, Cardiff Heights,\r New Lambton Heights, Elermore Vale and Wallsend before discharging the flow to\r Hexham Swamp. The creek channels vary from a near natural condition in the upper\r catchment reaches, to a formalised concrete lined channel in the lower reaches through\r the Wallsend Business District (WBD). The catchment responds quickly to large storm\r events, with floodwaters rising and falling in a matter of hours. Floodwaters converge\r on the WBD at the lower end of the catchment, and while by no means the sole site of\r flooding in the catchment, the WBD is the focus of catchment flood damage. \r \r Ironbark Creek, which drains the Wallsend-Plattsburg catchment, has experienced\r numerous and major floods since settlement. Most recently significant overbank\r flooding in April 1988, February 1990 and June 2007 caused extensive property and\r infrastructure damage in and around the Wallsend Business District and damage to\r residential properties further upstream on Ironbark Creek’s numerous tributaries. \r \r The recent devastating floods of June 2007 have, however, provided Council with a\r somewhat unique opportunity to take stock of proposed floodplain management\r initiatives by reviewing these initiatives in the context of this major flood event on the\r existing floodplain. Changes to the floodplain in the ensuing period since the April\r 1988 flood, including up-catchment sub-division and major road infrastructure upgrades\r such as the Thomas Street and Cowper Street bridges, and the development of the\r Wallsend Shopping Centre etc., while designed to minimise any influence on flooding,\r nevertheless provide some uncertainty on contemporary floodplain behaviour. Data\r collected by Council post the June 2007 flood event has provided information and\r insight into flooding behaviour in the catchment as it presently exists. \r \r Flood modelling of the Wallsend Plattsburg catchment has been undertaken to\r determine the existing flood behaviour of flood prone areas for a range of flood risk\r levels including the 0.2% Annual Exceedance Probability (AEP), 1%, 10% AEP events\r and the Probable Maximum Flood (PMF). \r \r Flood behaviour was determined for flood prone areas using mathematical modelling\r tools developed specifically for the study. Catchment runoff and overland flows were\r calculated using XP RAFTS and MIKE Flood (version 2008) modelling software.\r The model was successfully calibrated to two historical storm event, these being the\r evening event of 27th April 1988 and the Pasher Bulker flood of 7-9 June 2007.\r Design rainfall intensities and temporal patterns for the required range of flood risk\r events were obtained from ‘Australian Rainfall and Runoff’ (Institution of Engineers\r Australia, 2001) and ‘The Estimation of Probable Maximum Precipitation in Australia:\r Generalised Short-Duration Method’ (Bureau of Meteorology, 2003).\r The flood model predictions indicate that in many areas of the catchment the capacity of\r existing flow channels and road culverts are exceeded resulting in overland flooding for\r a range of simulated flood risk levels.\r Longitudinal profiles along the main tributary channels and plans showing the approximate\r extent of overland flooding for the range of design flood events are provided in\r Appendices D and E. Flood mapping in Appendix E is provided as inundation maps of\r peak water level, maximum water depth and maximum flood speed (velocity). Note\r that mapping shows envelopes of peak values, which would not necessarily be coincidental\r in space or time, and therefore are not indicative of actual ‘moments in time’ for\r the design events. The sensitivity of the model outputs to a range of model inputs and\r model parameters is summarised in Appendix F.\r The developed flood modelling tools and reported flood behaviour for existing catchment conditions can now be used as the basis for developing a Flood Risk Management Plan for flood prone land in the catchment. The hydraulic model developed for the flood study may generally be used to assess the hydraulic impact of any proposed structural flood mitigation works on flood behaviour.