Hilltops Council (Council) commissioned the Floodplain Risk Management Study and Plan for the township of Boorowa. The overall objectives of the Floodplain Risk Management Study (FRMS) were to assess the impacts of flooding, review existing Council policies as they relate to development of land in flood liable areas, consider options for the management of flood affected land and to develop a Floodplain Risk Management Plan (FRMP) which: i) Proposes modifications to existing Council policies to ensure that the development of flood affected land is undertaken so as to be compatible with the flood hazard and risk. ii) Proposes Flood Planning Levels for the various land uses in the floodplain. iii) Sets out the recommended program of works and measures aimed at reducing over time, the social, environmental and economic impacts of flooding. iv) Provides a program for implementation of the proposed works and measures. The FRMS focuses on Main Stream Flooding from the Boorowa River, Ryans Creek and Ryans Tributary, as well as two major un-named tributaries, Minor Tributary Flooding caused by high flows in the minor un-named tributaries which drain to the aforementioned watercourses, and Major Overland Flow areas which occur in the urbanised parts of Boorowa and its immediate surrounds.

Hilltops Council (Council) commissioned the Floodplain Risk Management Study and Plan for the township of Boorowa. The overall objectives of the Floodplain Risk Management Study (FRMS) were to assess the impacts of flooding, review existing Council policies as they relate to development of land in flood liable areas, consider options for the management of flood affected land and to develop a Floodplain Risk Management Plan (FRMP) which: i) Proposes modifications to existing Council policies to ensure that the development of flood affected land is undertaken so as to be compatible with the flood hazard and risk. ii) Proposes Flood Planning Levels for the various land uses in the floodplain. iii) Sets out the recommended program of works and measures aimed at reducing over time, the social, environmental and economic impacts of flooding. iv) Provides a program for implementation of the proposed works and measures. The FRMS focuses on Main Stream Flooding from the Boorowa River, Ryans Creek and Ryans Tributary, as well as two major un-named tributaries, Minor Tributary Flooding caused by high flows in the minor un-named tributaries which drain to the aforementioned watercourses, and Major Overland Flow areas which occur in the urbanised parts of Boorowa and its immediate surrounds.

Hilltops Council (Council) commissioned the Floodplain Risk Management Study and Plan for the township of Boorowa. The overall objectives of the Floodplain Risk Management Study (FRMS) were to assess the impacts of flooding, review existing Council policies as they relate to development of land in flood liable areas, consider options for the management of flood affected land and to develop a Floodplain Risk Management Plan (FRMP) which: i) Proposes modifications to existing Council policies to ensure that the development of flood affected land is undertaken so as to be compatible with the flood hazard and risk. ii) Proposes Flood Planning Levels for the various land uses in the floodplain. iii) Sets out the recommended program of works and measures aimed at reducing over time, the social, environmental and economic impacts of flooding. iv) Provides a program for implementation of the proposed works and measures. The FRMS focuses on Main Stream Flooding from the Boorowa River, Ryans Creek and Ryans Tributary, as well as two major un-named tributaries, Minor Tributary Flooding caused by high flows in the minor un-named tributaries which drain to the aforementioned watercourses, and Major Overland Flow areas which occur in the urbanised parts of Boorowa and its immediate surrounds.

Objective This Floodplain Management Study defines the nature and extent of the flood hazard in the three catchments. It also identifies and assesses strategies and measures aimed at reducing the impact of flooding on both existing and future development, and measures to prevent future development from making flooding worse. The results of this Floodplain Management Study are being used to prepare a Floodplain Management Plan (FPMP). The objective of the FPMP is to establish a cost-effective floodplain management strategy for the area and to recommend a programme for implementation of the Plan. The Study Brief is attached as Appendix A. What is in the Study The Floodplain Management Study and Plan will not totally eliminate flooding. Flooding is a natural phenomenon which cannot be fully controlled by human works. In fact, excessive artificial controls are likely to be very costly and to have adverse environmental effects. Therefore the Floodplain Management Study and Plan aim to provide a package of best management practices which give a balance between reducing flood hazard and flood damages, allowing appropriate development, and protecting and enhancing the environment of the floodplain. This Report has been divided into the following sections: Section 1: Introduction (page 1) Establishes the context and basis for the plan. Section 2: Background (page 5) Describes the study process, including previous studies, and the background technical information which is available. It includes a review of the previous Muddy Creek Flood Studies. Section 3: Existing Flood Behaviour (page 15) Summarises the available data and modelling results concerning flood behaviour. Section 4: Social and Economic Impacts of Flooding (page 23) Examines the potential flood damages and other social and economic effects of flooding for a range of flood events, including an extreme flood. Section 5: Choosing the Designated Flood (page 28) Discusses the issued to be considered by Council in choosing a designated flood for Rockdale, and recommends that the 1% AEP flood be adopted. Section 6: Available Floodplain Management Options (page 35) Describes in broad terms the range of flood mitigation and other management works and other measures available to address the existing, future and residual flooding problems in the study area. Sections 7, 8 and 9: Options for Management Areas (page 48) These three sections describe in detail, for the Muddy Creek, Spring St Drain and Scarborough Ponds catchments respectively, the feasible options and their likely benefits and costs. Section 10: Assessment of Management Options (page 86) Reviews the financial aspects and the justification for the proposed management measures, identifies priorities and possible sources of funding. These issues will be further addressed in the future Floodplain Management Plan. Section 11: References (page 90) Technical detail which supports the main report is provided in the Appendices, in Volume 2.

Drains used for model inputs

This report comprises an overview of the work that has been undertaken by WMAwater on the Manly Lagoon Floodplain Risk Management Study and Plan. It builds on prior stage reports and, in accordance with the Brief, it additionally includes a discussion of: • hydraulic and hazard categorisation; • future development scenarios; • review of climate change; • flood damages assessment; and • emergency management.