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Rural floodplain management plans

Draft Technical Manual for plans developed under the Water Management Act 2000

Published by the NSW Department of Primary Industries, Office of Water

Title: Rural floodplain management plans - Draft Technical Manual for plans developed under the Water Management Act 2000

First published September 2014

www.dpi.nsw.gov.au

JTN 13126

© State of New South Wales through the Department of Trade and Investment, Regional Infrastructure and Services, 2014. You may copy, distribute and otherwise freely deal with this publication for any purpose, provided that you attribute the NSW Department of Primary Industries as the owner.

Disclaimer: The information contained in this publication is based on knowledge and understanding at the time of writing (September 2014). However, because of advances in knowledge, users are reminded of the need to ensure that information upon which they rely is up to date and to check currency of the information with the appropriate officer of the Department of Primary Industries or the user’s independent adviser.

http://www.dpi.nsw.gov.au/

Rural floodplain management plans - Draft Technical Manual for plans developed under the Water Management Act 2000

i NSW Office of Water, September 2014

Contents Abbreviations ............................................................................................................................ 3

Background ............................................................................................................................... 4

Legislative and policy framework ............................................................................................ 5

Water Management Act 2000 .................................................................................................. 5

Other legislation and policy ...................................................................................................... 6

Rural floodplain management planning .................................................................................. 6

Consultation .............................................................................................................................. 9

Step 1: Define the floodplain boundary ................................................................................... 9

Step 2: Identify existing flood works ..................................................................................... 10

Step 3: Review existing rural floodplain management arrangements ................................. 11

Step 4: Determine the floodway network............................................................................... 14

Design floods ......................................................................................................................... 14

Hydraulic models ................................................................................................................... 15

Mapping the floodway network .............................................................................................. 16

Flooding regimes and the floodway network .......................................................................... 18

Step 5: Identify and prioritise floodplain assets ................................................................... 18

Ecological assets ................................................................................................................... 20

Prioritisation of ecological assets ........................................................................................... 20

Cultural assets ....................................................................................................................... 24

Prioritisation of cultural assets ............................................................................................... 25

Site sensitivity to flood works ................................................................................................. 25

Step 6: Socio-economic profile .............................................................................................. 25

Step 7: Delineate management zones ................................................................................... 26

Major flood discharge zone .................................................................................................... 26

Flood storage and secondary flood discharge zone ............................................................... 27

Flood fringe and existing developed areas zone .................................................................... 27

Approach to delineate management zones ........................................................................... 27

Hydraulic criteria .................................................................................................................... 28

Ecological and cultural criteria ............................................................................................... 30

Cultural Criteria – cultural assets identified by the community ............................................... 35

Summary of approach ........................................................................................................... 36

Step 8: Determine draft rules ................................................................................................. 37

Types of flood works .............................................................................................................. 37

Rules – authorised flood works .............................................................................................. 38

Rules – assessment criteria ................................................................................................... 39


ii NSW Office of Water, September 2014

Rules - advertising requirements ........................................................................................... 40

Step 9: Consider existing floodplain management arrangements ...................................... 40

Consideration of existing flood works ..................................................................................... 42

Step 10: Assess socio-economic impacts ............................................................................ 42

Phase one: preliminary assessment of socio-economic impacts ............................................ 42

Phase two: socio-economic impact analysis .......................................................................... 43

Other considerations ............................................................................................................. 43

Exemptions ............................................................................................................................ 43

Flood monitoring .................................................................................................................... 43

Flood monitoring guidelines for landholders ........................................................................... 44

Flood monitoring for local councils ......................................................................................... 45

Flood monitoring for the OEH ................................................................................................ 45

Environmental monitoring ...................................................................................................... 46

Environmental data ................................................................................................................ 47

Other considerations ............................................................................................................. 47

Existing works ....................................................................................................................... 47

Exemptions ............................................................................................................................ 48

Hotspots ................................................................................................................................ 48

References............................................................................................................................... 49

Appendix 1 Rural floodplain management planning approach under the Water Management Act 2000 ............................................................................................................ 50

Glossary .................................................................................................................................. 51


3 NSW Office of Water, September 2014

Abbreviations AEP Annual Exceedance Probability

AHIMS Aboriginal Heritage Information Management System

ASDST Aboriginal Sites Decision Support Tool

ATWG Aboriginal Technical Working Group

DVP Depth Velocity Product

FMP Floodplain Management Plan

IRP Interagency Regional Panel

MDB Murray-Darling Basin

NSW New South Wales

OEH NSW Office of Environment and Heritage

TAG Technical Advisory Group

WMA 2000 Water Management Act 2000

WA 1912 Water Act 1912



Background Floodplains are essentially areas of land subject to inundation by flooding. Many of the rural floodplains in the north of the Murray-Darling Basin contain western-flowing river systems. Flood waters from these systems are typically slow moving and spread over wide shallow floodplains, remaining on the floodplain from weeks to months. Flooding behaviours are also highly variable. This means that while overbank floods will occur reasonably often, their timing, volume and extent is unpredictable.

Flooding replenishes floodplain ecosystems and agricultural land with water, carbon, sediment and nutrients. The fertile soils and water resources made abundant during floods contribute to floodplains being classed as some of the most productive lands in Australia. For instance, in the Murray-Darling Basin, rural floodplains contribute about US$15 billion dollars annually, earning it the name ‘Australia’s bread basket’ (Dahm et al. 2013).

The ecological character of wetlands and many other ecosystems that reside on floodplains is dependent on flooding. Flood water can trigger the germination of native plants and disperse seeds; provide opportunities for spawning for native fish such as silver perch; and provide waterbird habitat for feeding and breeding. There are many nationally and internationally important wetlands residing on floodplains, such as Ramsar wetlands, that require flooding for their long-term survival. Flooding is also important for recharging shallow groundwater aquifers.

Floodplains are important to Aboriginal people because food, tools and medicinal items are plentiful during and following flood events. Places and objects on the floodplain that contribute to Aboriginal customary law, traditions, history and current practices often require flooding or their value to Aboriginal people is dependent on flooding. Floodplain flora and fauna also contribute to the social and ceremonial aspects of Aboriginal life as living scarred trees or as totem species.

In rural floodplains where land use is dominated by grazing, dryland cropping and irrigated cropping, works have been built on the floodplains to enhance agricultural productivity. Works, such as levees, earthworks, banks and channels (flood works) have been built to protect crops, stock and properties from flooding; provide on-farm access; and to manage irrigation, stock and domestic water.

In many instances, flood works have positively contributed to the agricultural productivity of land in Australia. However, when flood works are built in an uncoordinated way, they can cause major changes to traditional flood patterns. Flood flows may be redirected onto adjacent properties or flood levels and velocities may be increased. These changes can result in crop losses, erosion and scour and flood damages being experienced in areas that were traditionally relatively flood-free. In some instances, major flood works can influence flows many kilometres upstream and downstream beyond the original work location. Changes to flooding behaviour can also negatively impact floodplain ecosystems by blocking or redirecting flow away from flora and fauna that require flooding or towards species or cultural sites that are impacted by flooding.

The NSW Government has been actively involved in managing flood-work development on rural floodplains in the Murray-Darling Basin since the 1970s. To date, rural floodplain management has primarily focused on areas with intensive irrigation development where strategic management was required after major flood events revealed problematic changes to flooding behaviour caused by flood works. The history of rural floodplain management has shown strategic planning to provide



positive outcomes for maintaining and restoring a flooding regime that benefits floodplain ecosystems, cultural values and socio-economic functions. To build on the planning work done so far, new rural Floodplain Management Plans (FMPs) are being prepared for floodplains in the Murray-Darling Basin in accordance with the floodplain planning and environmental protection provisions under the Water Management Act 2000 (WMA 2000). These new rural FMPs aim to coordinate flood-work development to protect flooding behaviour while minimising risk to life and property from the effects of flooding. The new rural FMPs consolidate existing floodplain management arrangements and like existing rural FMPs made under the Water Act 1912 (WA 1912), the new rural FMPs aim to prevent flood-works from causing or exacerbating flooding problems and to maintain flood connectivity to floodplain assets. The new rural FMPs will use management zones and rules to coordinate flood-work development across the extent of major flooding in a floodplain. This technical manual seeks to inform local landholders and the wider community on how the new rural FMPs are being developed in the Murray-Darling Basin and how the plans will coordinate flood-work development. New rural FMPs are currently being prepared for the northern Murray-Darling Basin floodplains of the Barwon-Darling, Gwydir, Macintyre (Border Rivers), Macquarie and Namoi valleys.

Legislative and policy framework Water management in New South Wales is governed by Commonwealth and State legislation. The WMA was introduced in 2000, as part of the ongoing Council of Australian Governments-driven national water reform process (COAG 2004). The NSW Office of Water is beginning the process of transitioning from the floodplain management plan and controlled works provisions of Part 8 of the WA 1912 to the equivalent provisions under the WMA 2000. The NSW Floodplain Harvesting Policy (2013) will assist New South Wales to sustainably manage water on floodplains in rural areas of the Murray-Darling Basin in the context of the water management framework provided by the Basin Plan. The water management framework is being used to coordinate water extraction, environmental water, water quality and the development of flood works on floodplains. Rural FMPs align with and support the NSW 2021 State Plan. For instance, Goal 28, aims to increase the number of floodplain risk management plans available to support emergency management planning and Goal 22 aims to protect our natural environment and improve the environmental health of wetlands and catchments through actively managing water for the environment.

Water Management Act 2000 The object of the WMA 2000 is the sustainable and integrated management of the state’s water for the benefit of both present and future generations.

The WMA 2000 consolidates most of the Acts previously covering water management in New South Wales. The WMA 2000 is being phased in gradually as water sharing plans are developed and commenced for particular water sources. Rural FMPs will be developed to satisfy the objects and principles of the WMA 2000.

Part 3, Division 5 of the WMA 2000 specifies core provisions that must be dealt with in a floodplain management plan made for a water management area, as well as additional provisions that may



be dealt with. Division 1 of the WMA 2000 outlines water management principles that should be addressed in general by water management plans, as well as water management principles that relate specifically to floodplain management.

Other legislation and policy Other legislation and policy relevant to floodplain management that are to be considered in the preparation of rural FMPs include:

Acts • Commonwealth Environment Protection and Biodiversity Conservation Act 2000 • Commonwealth Water Act 2007 • NSW Environmental Planning and Assessment Act 1979 • NSW Fisheries Management Act 1994 • NSW National Parks and Wildlife Act 1974 • NSW Native Vegetation Act 2003 • NSW Threatened Species Conservation Act 1995

Policies and strategies • Japan-Australia Migratory Bird Agreement (1974), China-Australia Migratory Bird Agreement

(1986) and Republic of Korea-Australia Migratory Bird Agreement (2006) • Murray-Darling Basin Plan (2012) • NSW Biodiversity Strategy (1999) • NSW Floodplain Harvesting Policy 2013) • NSW Flood Prone Land Policy (NSW Government 2005) • NSW State Rivers and Estuaries Policy (1993) • NSW Strategic Regional Land Use Policy (2012) • NSW Wetlands Management Policy (1996).

Rural floodplain management planning The rural floodplain management planning approach has been revised primarily in response to changes to the legislative and policy framework which governs water management in New South Wales. The rural floodplain management planning approach was made to satisfy the provisions of Part 3 of the WMA 2000. The WMA 2000 is the culmination of the NSW water-reform process driven by the Council of Australian Governments to sustainably integrate management for all water-based activities. The previous generation of rural floodplain management plans were made and gazetted under the amended Part 8 of the WA 1912. The floodplain management provisions of the WMA 2000 relate closely to the provisions of the amended Part 8.

The new rural floodplain management planning approach integrates existing floodplain management planning measures into a single strategic plan that covers the extent of major flooding in a valley. Existing management measures include levee/floodway schemes captured in first generation Floodplain Development Guidelines, which were used to guide the location of flood works constructed by landholders for cropland protection while maintaining unimpeded passage for floodwaters. Existing management measures also include existing rural FMPs which are second generation statutory plans developed under the amended Part 8 of the WA 1912. These plans are



strategic in nature and were developed to overcome difficulties with the assessment of works on an ad-hoc basis.

The new rural FMPs consider community understanding of existing floodplain management arrangements, and ensure implementation and compliance with these arrangements. Ultimately, the new rural FMPs will supersede existing rural floodplain management plans in each valley.

The new rural FMPs provide hydraulic modelling based on the latest flooding knowledge to build on the information contained in the floodway networks of existing floodplain management measures. This hydraulic information, as well as the best available information on floodplain assets and socio-economic factors is used to develop management zones, which are areas in the designated floodplain that have specific rules to define the purpose, nature and construction of flood works.

The new rural floodplain management planning approach is an important next step in strategically coordinating flood-work development, and will:

• provide future certainty to landholders about where they can construct flood works • fast track the approval process for new flood-works • increase awareness of and minimise adverse risk to life and property from the effects of

flooding • maintain flood connectivity to existing floodplain assets, including ecological and cultural assets • assist with floodplain management for the whole of rural New South Wales. • effect the orderly passage of flood waters through the floodplain • contribute to the protection of ecological, cultural, heritage and spiritual features that are

significant to Aboriginal people and other stakeholders. The floodplain management planning approach for FMPs developed under the WMA 2000 involves ten steps (Figure 1).



Figure 1. Ten steps used to develop rural floodplain management plans under the Water Management Act 2000

Step 1 is undertaken to define the floodplain boundary pertaining to the rural FMP.

Steps 2-6 are primarily information-gathering exercises that involve developing a data compendium, identifying and filling data gaps and documenting key aspects of the floodplain in a way that they can be used for decision-making.

Steps 7-9 are decision-making steps that involve using the information gathered in the previous steps to develop the management zones and rules. Step 10 ensures consideration of the potential socio-economic impacts during Steps 7-9.

Community consultation undertaken during targeted consultation and public exhibition may require earlier steps to be revisited to refine the management zones and rules to have a more equitable product. In this way, the process for developing the rural FMP is iterative.

The following sections describe in detail the ten steps for developing the management zones and rules in rural FMPs. Appendix 1 contains a detailed flow diagram of the 10 steps including the input/process and output/outcome related to each step.



Consultation Engagement and consultation strategies for developing rural FMPs ensure that all stakeholders and interested parties have opportunity to examine and comment on the outcomes of the floodplain management assessment and planning.

During the preparation of the technical content of the rural FMPs, the NSW Office of Environment and Heritage (OEH) consults with Technical Advisory Groups (TAG), which are created to provide expert knowledge and technical advice on the rural FMPs. TAGs are made up of NSW Government agencies and other key agencies involved in water management in New South Wales, including the Office of Water, Fisheries NSW, Agriculture NSW, Local Land Services, regional councils, the Queensland Murray Darling Committee, the Murray-Darling Basin Authority, and the Commonwealth Environmental Water Office. Consultation with the TAG aims to collect all available knowledge relevant to floodplain management planning in a particular valley, such as information gathered during historic flood events as well as data on ecological and cultural assets. The TAGs also help to develop scientifically rigorous methods for the technical assessments undertaken as part of developing the proposed rural FMPs.

Each proposed FMP is presented to an Interagency Regional Panel (IRP) comprising of members from a range of agencies that represent water management, agricultural, fisheries and environmental interests. The IRP consider the proposed FMP to ensure that management rules achieve the objects of the WMA 2000 and to provide information and analysis from a whole-of-government perspective. IRPs include decision-makers who are regional staff from the Office of Water, NSW Department of Primary Industries and OEH. The IRP also includes observers from State Water and Local Land Services.

The IRP consider the proposed FMP before it is released to key stakeholders for their input via a targeted consultation process. OEH engages with community-based stakeholders (particularly local landholders and water users) to seek and consider feedback on the proposed management zones and rules in a draft rural FMP before the plan is put on public exhibition. For instance, the community might suggest areas where further analysis or data gathering is required. This local input is essential in the finalisation of plans.

The IRP then reconvenes to make any necessary modifications based on stakeholder input. The revised draft FMP is then presented to the wider community via a public exhibition process. During the formal public exhibition of a draft rural FMP, the Minister for Natural Resources, Lands and Water invites submissions on the draft plan and in particular will seek comment on a range of key issues. The IRP is reconvened after public exhibition to review outcomes and to recommend changes to management zones and rules based on community feedback.

The FMP is finally submitted to the Minister for Natural Resources, Lands and Water for endorsement who is required to seek concurrence of the Minister for the Environment to proceed.

Step 1: Define the floodplain boundary A floodplain is an area of land that is subject to inundation by floods. Legally, a floodplain is any land that is designated by an order in force under section 166(1) of the WA 1912 and land declared to be a floodplain by the regulations within the WMA 2000.



A floodplain is typically defined by investigating the nature and extent of flooding over time (DIPNR 2005). Hydrologic and hydraulic data are collected to determine the nature and extent of flooding for large flood events.

Other information that is considered for defining the floodplain boundary includes:

• existing floodplains designated under Part 8 of the WA 1912 • areas of floodplain harvesting • administration boundaries of current water sharing plans • cadastral relevance • statutory boundaries and infrastructure features that facilitate licensing administration. These

include property, county, parish and LGA boundaries, roads and railways.

Step 2: Identify existing flood works Step 2 is undertaken to identify information on existing flood works, which is used in the hydraulic modelling to develop management zones. This information is also used to tailor the proposed rules and assessment criteria to ensure that the type of works likely to be approved will be fit-for-purpose.

The core provisions of the WMA 2000 that relate to floodplain management require the identification of existing flood works in the area and the way they are managed, their benefits in terms of the protection they give to life and property, and their ecological impacts, including cumulative impacts.

Flood works are defined in the WMA 2000 as:

a work (such as a barrage, causeway, cutting or embankment):

• that is situated: o in or in the vicinity of a river, estuary or lake, or o within a floodplain, and

• that is of such a size or configuration that, regardless of the purpose for which it is constructed or used, it is likely to have an effect on: o the flow of water to or from a river, estuary or lake, or o the distribution or flow of floodwater in times of flood.

And includes all associated pipes, valves, metering equipment and other equipment, but does not include any work declared by the regulations not to be a flood work.

On the ground, this definition is generally taken to include the following types of flood works:

• access roads: to ensure landholders have basic provisions to access property • below-ground supply channels: to ensure supply channels reach water sources so landholders

can access water rights • infrastructure protection works: to minimise risk to life and property. • stock refuges: to account for animal welfare and to minimise landholder’s potential to lose stock

to flood waters • other flood works: such as levee banks that are generally used for crop and land protection

against floods.



Where an application for a new water supply work, including floodplain harvesting works, falls within an FMP area, the application will be assessed against the FMP rules and assessment criteria to ensure that the application does not conflict with the FMP or result in adverse impacts on flood behaviour. This assessment process may result in additional conditions being placed on the water supply work approval to ensure the work is consistent with the FMP. Generally, existing flood works are identified in the new rural FMPs by mapping the area of land protected by flood works (developed areas) as well as the number of flood-work licenses in the floodplain.

This is done using various data sources, including: • licensed works provided by the Office of Water • canal watercourse lines and floodwater storages (OEH, Bureau of Meteorology, Australian

Hydrological Geospatial Fabric database • land use mapping • spatial layers from previous floodplain management arrangements • other topographical data (including LiDAR survey) • aerial photography, oblique aerial photography, and satellite imagery from flooding and dry

periods to verify existing flood works. A thorough review of the developed areas is also conducted by experts from the OEH and Office of Water. Developed areas are areas bound by identified existing flood works that comply with previous floodplain management arrangements. Developed areas are included in hydraulic modelling and used to assist the delineation of the floodway network (Step 4) and are considered when delineating the management zone (Step 7).

Step 3: Review existing rural floodplain management arrangements Step 3 is undertaken to ensure that the new rural FMPs consider existing rural floodplain management arrangements in the context of the history of rural floodplain management (Figure 2).

As part of the development of new rural FMPs, there needs to be adequate consistency between past and present floodplain management planning (Step 9). To assist with this, rural floodplain management arrangements were analysed to identify:

• floodplain management principles • ecological considerations • cultural heritage considerations • floodway networks/flowpaths • hydraulic models • design flood events • assessment criteria for permitting new flood works • advertising requirements for flood-work applications. These key aspects of existing floodplain management arrangements were considered in light of how the strategic management of flood works in the Murray-Darling Basin has evolved. For instance, flood-work management has evolved in response to changes in community needs; changes to land and water use; an increased awareness of the importance of floodplain ecology and changes to the legislative and policy framework which govern water management.



In response to major flood events, the NSW Government has been actively involved in managing flood-work development on rural floodplains in the Murray-Darling Basin since the 1970s. Since then, the location of existing flood works on rural floodplains has been guided by one or more of following floodplain management arrangements:

• first generation rural floodplain development guidelines (non-statutory) Floodplain development guidelines were developed by the NSW Government following the enactment of the then Water Resources Commission Act 1976. Under the provisions of this legislation, Guidelines, which were levee/floodway schemes, were prepared for the worst flood-affected areas in the Murray-Darling Basin. The approach aimed to provide floodways of adequate hydraulic capacity and continuity, by restoring or maintaining, as far as practical, the natural pattern of flood channels for the effective conveyance of flood flows. Flood protection of developed land was accomplished by the construction of levees bordering the floodways and was funded and implemented by the benefiting landholders. These Guidelines were used as a reference for coordinating floodplain development and described areas where development was and was not appropriate. In some areas, the Guidelines were superseded by rural Floodplain Management Plans which are statutory.

• second generation rural floodplain management plans prepared under the WA 1912 In 1999, Part 8 of the WA 1912 was amended to allow for more strategic coordination of controlled works through the preparation of statutory rural floodplain management plans to manage floodwaters. Up until this point, the floodplain development guidelines produced were not statutory.

The rural floodplain management plans are statutory documents developed under the principles of the NSW Floodplain Development Manual (DIPNR 2005) and in consultation with a community-based floodplain risk management committee. These plans are similar to the new rural FMPs. The main difference between these plans is that the coverage of the rural floodplain management plans is substantially smaller and so the planning is more property-specific. Existing floodplain management plans describe environmental assets, identify areas where flood water passage is impeded, the nature and extent of flood works that are permissible on the floodplain, as well as propose remediation actions that aim to improve flood connectivity.

• outcomes from flood studies (non-statutory) In some instances flood studies were undertaken in response to development pressures on rural floodplains. However, management plans were not developed in light of these flood studies. These studies are considered to be non-statutory.



Figure 2. Legislative and policy evolution in floodplain management



Step 4: Determine the floodway network Step 4 is undertaken to spatially determine the floodway network, which is designed to have adequate hydraulic capacity and continuity to effectively convey flood waters. The floodway network is comprised of:

• a coordinated and integrated network of floodways where a significant discharge of floodwater occurs during floods

• the inundation extents of small and large design floods • areas that preserve floodplain connectivity • areas that provide sufficient temporary pondage of flood water. The floodway network is the hydraulic basis for determining the management zones and rules. Step 4 involves selecting floods of different magnitudes (design floods) and constructing hydrologic and hydraulic models to simulate the movement of those floods through the river channels and floodplain. This modelling data as well as additional data, such as flood imagery, is used to map the floodway network. Maps of the floodway network generally show two hydraulic categories:

• floodways, which are areas where a significant discharge of floodwater occurs • inundation extent, which includes areas of the floodplain that are important for the temporary

storage of floodwaters during the passage of a flood.

Design floods Modelled design floods are usually based on recorded historical events that are (preferably) within the living memory of a local community. This approach enables the community to comprehend the magnitude of the flood events being modelled. Where no suitable historical floods are available, a probabilistic design flood is setup using hydrologic models.

Design floods are selected to account for the social, economic and ecological consequences associated with floods of different severities. A flood frequency analysis is undertaken to assist with the selection of the historic design floods. Flood frequency can be expressed as Average Recurrence Interval (ARI - years), or Annual Exceedance Probability (AEP). The flood frequency analysis uses available flooding information, which may include records from when the flooding regime was relatively natural, as well as information that encompasses the existing flooding regime. The AEP for all historic events is calculated and small and large events are selected. The event referred to as the ‘large design flood’, usually has an AEP of around 1 in 20-30 years or may be larger if a historical flood has a greater recurrence interval and has been previously accepted by the community as a basis for design. This ‘large design flood’ is used to delineate the limits of the floodway network and the floodway areas. The basis for selecting a large historic flood includes;

• it is the most recent large flood • it is representative of large floods in the valley • there is a significant amount of information available for the event • it has been previously used and widely accepted as the design flood. The flood event referred to as the ‘small design flood’ is a smaller-scale event that has an AEP of generally less than one in eight years. This event is used to simulate events that are likely to be more frequent than the large design event. This smaller event is used to check that critical flow paths to floodplain assets are identified within the floodway network.



For probabilistic simulations, the design flood is calculated using a chosen AEP and is often used in conjunction with a hydrologic model (also known as rainfall runoff models) which simulate runoff from rainfall on a catchment. The models convert a design storm rainfall of a chosen AEP to flow hydrographs using a procedure known as runoff routing. A loss model is used to determine the rainfall excess by subtracting catchment losses, such as soil and surface storage, from the total rainfall. Rainfall excess is then routed through the catchment storage to produce discharge hydrographs at key locations (Mein and Nathan 2010). Similarly, ungauged catchment inflows for historical floods are calculated using a hydrology model and recorded rainfall. Alternatively, inflows for the probabilistic design flood can be derived for the selected return interval from flood frequency analysis at a gauge.

Modelling of the inundation extent for a 1 in 100-year flood provides additional hydraulic information. This information is useful for assessing the hydraulic impacts of proposed flood works on floodplain areas that are outside the inundation extent of the design flood. The 1 in 100-year flood extent is an estimate only to assist the hydraulic analysis of flood works and is not normally mapped for rural floodplain planning purposes. This information is retained by the Office of Water and is made available to landholders where additional supporting information such as hydraulic modelling is required to support applications for flood works.

The gauged historic flood flows and flood flows derived from the hydrological modelling for the small and large design floods are represented by inflow hydrographs which serve as inputs to the hydraulic models at boundary locations.

Hydraulic models Computer-based hydraulic models are used to simulate the movement of water for the large and small design floods. The gauged inflows and the inflows derived from the hydrological modelling for the small and large design floods are used as inputs into the hydraulic models. The hydraulic models are generally combinations of one-dimensional (1D) river systems, which model channel flow and two-dimensional (2D) grids, which simulate water flowing over floodplains. Flow within the model domain is described by the shallow water (saint-venant) equations, which consider both the conservation of mass and momentum. The location of flow paths in the models are determined using digital elevation models, flood aerial photography, satellite imagery, watercourse layers, flood marks and local knowledge.

Hydraulic model outputs used include:

• discharge, velocity and depth at key locations and flow distribution maps • a depth-velocity product map from the large design flood • inundation extents of the small and large design floods. These outputs are used to determine the appropriate size of each floodway in the floodway network. Floodways have been traditionally viewed as areas of high velocity and depth that convey a significant proportion of floodwaters. Hydraulic models calculate the product of depth and velocity at each model calculation point. The highest depth-velocity product values are then mapped for each point. Floodways to include in the floodway network are then quantitatively identified by applying a meaningful threshold to the mapped depth-velocity product values (Figure 3). If depth-velocity product mapping is not available, thresholds are set on the modelled discharge or velocity along flowpaths.



Figure 3. Example of a depth-velocity product from the large design flood in the Gwydir floodplain.

Model calibration

Hydraulic models are calibrated against hydraulic parameters including water depth or water surface elevation, discharge and velocity using selected historic flood events that are around the design flood magnitude and have caused all likely flow paths to be active.

The models are calibrated against a range of data sources, particularly:

• peak flood heights at gauge locations • available flow distribution calculations for existing floodplain development guidelines • the peak discharge magnitude and timing at gauge locations • flood extents from satellite imagery and aerial photography. A sensitivity analysis is also undertaken on key model parameters, such as surface roughness and inflows, by varying the parameter values and calculating the impact of these changes on the results.

The hydraulic models utilise the best available data, including representation of the developed areas (Step 2). The final choice of appropriate models is governed by availability of data and complexity of the floodplain. The outputs of these models are then mapped.

Mapping the floodway network The floodway networks are delineated from modelled hydraulic parameters. Hydraulic model outputs used in floodway network determination include:

• depth-velocity product maps for large design floods • discharge and velocity values along flow paths • inundation extents for small and large design floods.



These outputs are used to determine the appropriate size of each floodway and the overall floodway networks (see Table 1 and Figure 4). Where reliable flood extents can be produced from each floodplain’s large design event, the outer limits are used to determine the extent of the floodway networks (Figure 4). However, where topographic data is not sufficient to accurately map the extents of the floods, the limits to the floodway networks are determined by using aerial and satellite flood imagery captured for the design events.

Hydraulic modelling outputs may not always account for all of the important floodways. This is often due to the chosen scale for computational points within the model setup. Here additional data is used to ensure that the floodway networks represent on-ground conditions. This data includes:

• flood aerial photography and satellite imagery • spatial watercourse layers and topographical mapping • previous floodplain management plans and development guidelines • local knowledge obtained from floodplain communities, and floodplain and environmental

managers. The floodway networks are finalised to spatially capture flood behaviour in the floodplain and used to inform the hydraulic criteria for the management zones.

Table 1. Summary of criteria used to delineate the hydraulic categories in the floodway network

Hydraulic category Criteria

Floodways • Areas that have a depth-velocity product of a selected threshold (varies for each floodplain) for the large design flood

• Parts of the small design flood extent that ensure continuity of floodways

Inundation extent • Flood extent up to the large design flood

• Does not include areas categorised as floodways

Areas outside floodway network

• Flood fringe area outside large design flood extent

• Existing licensed developed areas.



Figure 4. Example of the floodway network from the Gwydir floodplain.

Flooding regimes and the floodway network The core provisions of the WMA 2000 that relate to floodplain management require the existing and natural flooding regimes in the area to be identified in terms of the frequency, duration, nature and extent of flooding. The mapping of the floodway network integrates information from design flood analysis and hydraulic modelling to address these core provisions in the following ways:

• frequency – a flood frequency analysis is undertaken to select small and large design floods to use when modelling the floodway network. The flood frequency analysis uses flooding information from when the flooding regime was relatively natural, as well as information that encompasses the existing flooding regime

• nature – the hydraulic models that underpin the floodway networks for each floodplain contain information on the nature of flooding, including the size and roughness of floodways and connections between floodways. The models represent rivers, streams, overland flowpaths and wetlands to simulate the movement of flood water through the floodplain

• extent – modelled inundation extents of a small and large design flood are represented in the floodway networks.

Step 5: Identify and prioritise floodplain assets Floodplain assets are ecological assets, such as semi-permanent wetlands and cultural assets, such as scarred trees which are Aboriginal values. Cultural assets also include heritage sites, such as heritage-listed bridges. Floodplain assets can be flood-dependent, such as fish nursery grounds on the floodplain that require inundation to be accessed and utilised by native fish or those which are flood-impacted, such as Aboriginal burial sites which can be damaged by scour and erosion caused by flooding.



Step 5 is undertaken to identify and prioritise the many unique and diverse floodplain assets found on the focus floodplains. The floodplain assets are then used to inform the design of the management zones and rules in the rural FMPs.

High-priority floodplain assets are considered in the design of the management zones, which aim to ensure that flow paths kept free from flood works that may prevent water from reaching assets or redirect flow onto assets susceptible to damage from erosion (Step 7). To further minimise adverse impacts associated with flood-work development, all floodplain assets, regardless of their level of priority, are considered when determining the rules for the management zones (Step 8). In this way, the rural FMPs can protect flood connectivity to assets to help meet the following two objectives:

• to contribute to the protection and improvement of the environmental health of wetlands, other floodplain ecosystems, and groundwater recharge

• to contribute to the protection of ecological, cultural, heritage and spiritual features that are significant to Aboriginal people and other stakeholders.

Floodplain assets are defined to reflect the floodplain features that require protection and restoration under the water management principles of the WMA 2000. These floodplain features include:

• floodplains and dependent ecosystems, including groundwater and wetlands • habitats, animals and plants that benefit from water or are potentially affected by managed

activities • geographical and other features of indigenous significance • geographical and other features of major cultural, heritage or spiritual significance. Most of the identified floodplain assets are dependent on the many benefits of flooding for their structure, function and long-term survival. Flooding is a vital natural process that replenishes floodplain ecosystems with water, carbon, sediment and nutrients, which drive pulses of ecological productivity. To meet the core provisions of the WMA 2000, the ecological benefits of flooding are listed in the FMP. The ecological benefits of flooding generally include flood waters maintaining or improving the structure, condition and diversity of wetland and riverine ecosystems. Specific ecological benefits of flooding may include:

• contributing to sediment, nutrient and carbon cycling • promoting growth and recruitment of vegetation, including flowering, seeding and germination • providing breeding habitat for waterbirds, amphibious fauna and fish • recharging groundwater reserves • replenishing drought refuges such as waterholes The cultural benefits of flooding generally include:

• cultural processes that are triggered by flooding o harvesting resources during a flood o undertaking cultural activities that can only occur during a flood o visitation and access during flooding

• continuation of cultural practises o preservation and longevity of Aboriginal values



o maintaining potential for cultural renewal o maintaining spiritual connection with the floodplain landscape.

Rural FMPs aim to promote the ecological and cultural benefits of flooding. The process for identifying and prioritising ecological assets and cultural assets varies and is described in detail below.

Ecological assets Ecological assets are a wetland or other floodplain ecosystem, including watercourses that depend on flooding to maintain their ecological character. Areas where groundwater reserves are recharged by flood waters are also considered to be ecological assets. For the purpose of the rural FMPs, ecological assets are spatially explicit and are set in the floodplain landscape.

Ecological assets include floodplain ecosystems that provide habitat for fish, amphibians, reptiles, water and woodland birds and mammals, as well as invertebrate and microbial biota. Ecological assets can also provide other valuable ecosystem services such as drought refuge, nutrient cycling, carbon storage and groundwater recharge. Flood-dependent ecological assets are reliant on regular flooding and floodplain connectivity provides opportunities for watering of assets during flood flows. Flooding can flush a system of excess nutrients and sediment, improving water quality and providing opportunities for flora and fauna to disperse and breed over the floodplain.

The rural FMPs consider three types of ecological asset:

• wetlands • other floodplain ecosystems • areas of groundwater recharge. Within these ecological assets, biodiversity features of conservation significance recognised in national, state and local legislation, policies and programs are considered. These biodiversity features include listed species, communities and habitats, wetlands identified by the Ramsar Convention on Wetlands of International Importance and bilateral migratory bird agreements.

Other information used to identify ecological assets is sourced by reviewing relevant government programs and management plans, including the Murray-Darling Basin Authority’s Key Environmental Assets, Directory of Important Wetlands Australia and environmental watering plans. Ecological assets are also identified by consulting refereed scientific and government literature, environmental specialists, and by conducting spatial analyses of existing environment data sets. Data sets that may be considered include inundation gradients, vegetation mapping, soil mapping (including type and infiltration) and flora and fauna occurrence data.

The level of flood dependency of assets is a key consideration when making management decisions. Once identified, wetlands and other floodplain ecosystems are categorised according to the level of flood dependency of vegetation communities.

Prioritisation of ecological assets Ecological assets are prioritised to select the assets that best represent biodiversity in the focus floodplains. By considering high-priority assets in the design of management zones, the FMPs aim to maximise the ecological benefits of flooding. The selection of high-priority ecological assets is guided by decision-support software that considers conservation planning principles including comprehensiveness, adequacy, representativeness, adequacy and efficiency.



Floodplain landscapes are highly complex and there is a large diversity of plants, animals and microscopic organisms. To represent this floodplain biodiversity, several key surrogates that comprise ecological assets are chosen for input into the prioritisation process. The surrogates are representative of biodiversity patterns across the floodplain and hence have varying degrees of flood dependency. Surrogates are spatially definable components of biodiversity patterns that may include, but are not limited to, mapped information on vegetation communities, water birds, fish, amphibians, aquatic macroinvertebrates and aquatic flora. Surrogates also include areas of conservation significance, such as the habitats of rare and threatened species associated with floodplain environments as well as ecosystems afforded special protection or consideration such as Ramsar wetlands.

Identification of priority ecological assets is undertaken using a conservation planning decision support software known as Marxan (Ball and Possingham 2000; Possingham et al. 2000; Ball et al. 2009). Marxan is used to address core systematic conservation planning principles, including comprehensiveness, representativeness, adequacy and efficiency, to efficiently group parts of the landscape so that biodiversity features complement each other (Margules and Pressey 2000). Marxan operates on the minimum-set problem, which can be described as the algorithms objective to meet defined target amounts of conservation features for the lowest possible cost.

The prioritisation approach involves:

• partitioning the floodplain into planning units, which are used to group features of biodiversity (surrogates)

• using local and expert knowledge to set targets, which are conservation objectives that specify the amount and/or distribution of a surrogate that needs to be conserved

• developing a spatial layer that represents the ability to physically connect flood water to ecological assets to constrain the selection of priority planning units. For this exercise, the more difficult it is to connect flood water to an ecological asset the greater the cost of selecting that asset.

The decision-support software is then run using a simulated annealing optimisation method to determine the planning units that best meet the conservation targets with the least cost (Ball and Possingham 2000).

Typically, the decision-support software is run using one million iterations across 100 runs. The single best solution across 100 runs is chosen to identify priority planning units (Figure 5).



Figure 5. Priority planning units selected in Marxan - example

The ecological assets are then prioritised by relating the prioritised planning units to natural landscape patterns, which are generally mapped vegetation boundaries. The final product is a map of high-priority ecological assets (Figure 6).

Figure 6. Prioritised assets are identified by relating prioritised planning units to natural landscape patterns – in this example, to floodplain vegetation.



Another output of Marxan is the selection frequency score (Figure 7). The number of times a planning unit was selected in each of the 100 runs was counted to measure the relative importance of planning units (Figure 7).

The selection frequency score provides feedback on how likely an area will be included in an efficient solution. When a planning unit is never selected it is attributed with a frequency score of 0, while those that are always selected will have a selection frequency equal to the number of runs of the Marxan software (e.g. the highest possible frequency score for a planning unit is 100, based on 100 runs). Areas with a high frequency score are consistently important in the solutions. They are highly irreplaceable and have fewer substitutes if conservation objectives are to be achieved efficiently (Figure 7). Planning units that are rarely selected do not contribute efficiently in meeting conservation targets.

Figure 7. Areas identified as important based on their selection frequency of planning units by Marxan.. Summary of 100 Marxan runs. Colours indicate the number of times a particular planning unit was part of a solution.

This information is used to assist with justifying the adjustment of management zones to better protect flood connectivity to ecological assets in Step 6.

Information from the ecological prioritisation is considered in combination with flood behaviour to inform the design of management zones that would adequately protect the passage of flood water to ecological assets and to help ensure the persistence of floodplain ecosystems (see Step 6 for more information).



Cultural assets Cultural assets are objects, places or values that are important for people to maintain their connections, beliefs, customs, behaviours and social interactions. Within the rural FMPs two categories are used to address cultural assets:

• cultural assets that are dependent on flooding • cultural assets that are impacted by the effect of flood works on flooding. Both categories include Aboriginal values and heritage sites.

Aboriginal values Aboriginal values concern cultural assets that Aboriginal people identify as being important to them. Aboriginal values are intricately connected with the landscape. That connection concerns the physical landscape (land, water, flora and fauna), objects and places that were used by Aboriginal people in the past (archaeological sites), and places that are imbued with significance today and into the future (places with spiritual significance, places of significant events and places connected with memory).

For the purpose of the rural FMPs, Aboriginal values are defined by their relationship to flooding. Flood-dependent Aboriginal values are dependent on flooding for longevity and can include:

• ecological asset(s) that: o have been culturally modified: scarred tree

tree carvings

o are recognised for their spiritual and/or cultural significance o are or contain resources that are or were utilised in cultural activities o are associated with places that are used for contemporary cultural activities

• Places or sites that are or could be used for cultural activities that benefit from flooding: o fish traps: (e.g. stone or stick fish traps).

Flood-impacted Aboriginal values may be adversely impacted by changes in flood-flow distribution caused by flood works and may include those that are vulnerable to erosion by water flow, such as camp sites and burial sites.

Aboriginal community consultation helps identify intangible values, such as spiritual places, knowledge, songs, stories or the abundance of flora or fauna used to continue cultural practices that are relevant to the management of the floodplain.

Flood-dependent and flood-impacted Aboriginal values were identified at a regional scale using:

• consultation with cultural heritage experts and the local Aboriginal community • site records from the Aboriginal Heritage Information Management System (AHIMS) database • predicted site occurrence from the Aboriginal Sites Decision Support Tool.

Heritage sites Heritage sites are cultural assets that are on Commonwealth, State and local government heritage registers. These registers include:

• the OEH web portal www.environment.nsw.gov.au/Heritage/searchesdirectories.htm

http://www.environment.nsw.gov.au/Heritage/searchesdirectories.htm



• the Historic Heritage Information Management System • AHIMS - see www.environment.nsw.gov.au/licences/. Heritage sites include both Aboriginal and European heritage sites. Heritage sites are identified by conducting a search of these registers. Sites identified through these heritage registers are then assessed to determine whether they are flood-dependent or flood-impacted. Heritage sites such as bridges, buildings and cemeteries may be sensitive to erosion during flooding.

Hydraulic modelling was used to identify sites potentially at risk from changes in flood behaviour.

Prioritisation of cultural assets The rural FMPs provide a framework so that cultural assets on the floodplain incur minimal impacts from flood work activities. Protection of cultural assets is afforded by not permitting flood works to be developed in areas where flow paths to flood dependent assets would be obstructed, or where diverted floodwaters would cause significant damage.

The first step for prioritising cultural assets is to determine whether and how cultural assets are affected (dependent or impacted) by floodwater. Non-Aboriginal sites are determined to be flood-dependent or flood-impacted by assessing the associated documentation with heritage listings.

To prioritise cultural assets associated with Aboriginal values, an Aboriginal Technical Working Group (ATWG) was established. The working group comprised of Aboriginal people with knowledge of and/or connection with the floodplains. The ATWG is then consulted with regarding issues that require their expertise.

Site sensitivity to flood works The installation or modification of flood works poses a risk to existing and yet un-identified cultural assets. Such cultural assets are those that are sensitive to ground disturbance. Examples of Aboriginal cultural assets that would be irreparably damaged by earth works include, Aboriginal camp sites; burial grounds; middens; or scarred trees (in the case of land clearing). Within the rural FMPs, existing areas with a high potential for unidentified assets that are sensitive to land disturbance were identified. This step enables any unidentified assets to be included for further assessment and consideration within the rural FMPs as part of any flood works approvals process.

Step 6: Socio-economic profile Step 6 involves preparing a profile of socio-economic factors. A baseline profile is developed for the rural FMPs to provide a ‘snapshot’ of the current socio-economic factors in the floodplain area.

The water management principles of the WMA 2000 require that planning on floodplains considers the socio-economic impacts of proposed flood-work management strategies to maximise the social and economic benefits to the community; to avoid and minimise the impacts of flood works on other water users, and to minimise the existing and future flood risk to human life and property arising from occupation on floodplains.

The rural FMPs will contain management zones and rules that provide an equitable and consistent approach to coordinating development on the floodplain. The management zones and rules will be designed to minimise the impact that flood-work development may have on neighbouring properties, which will help to minimise the risk to life and property from the effects of flooding. A socio-economic profile of the area is required to be able to effectively do this.

http://www.environment.nsw.gov.au/licences/



Before options for future water resource management are developed, it is important that the floodplain area is well understood and the ability of communities to absorb change is appreciated.

The focus of the profile of the socio-economic factors is to assemble existing key socio-economic data which will provide a general picture of the catchment in terms of its socio-demographic and economic structures. Developing the profile, or ‘snapshot’, involves documenting the biophysical, social and economic conditions of the valley to help understand the floodplain. The main types of socio-economic information that inform the baseline profile include:

• geographies that are relevant to the socio-economic discussion of water use on the floodplain • demographic information • employment by industry • income statistics • production statistics. Information from this assessment will be used in a socio-economic impact analysis to identify and take into account potential socio-economic impacts associated with implementation of the rural FMPs. The socio-economic impact analysis is undertaken in coordination with the development of management zones and rules for a valley. The socio-economic profile analysis informs Steps 7,8 and 9.

Step 7: Delineate management zones The rural FMPs contain management zones to coordinate the development of flood works on the floodplains to protect the passage of flood waters. A management zone is an area in the floodplain that has specific rules and assessment criteria to define the type and nature of flood works that can occur in that area. The rules for each management zone are determined in Step 8.

In accordance with the floodplain planning provisions and environmental protection provisions of the WMA 2000, management zones are developed to deal explicitly with proposals for the construction of new flood works and the amendment of existing flood works. The objective across each of the floodplains is to prevent future flood works from causing or exacerbating flooding problems and to maintain connectivity to floodplain assets.

In Step 7, management zones are delineated by grouping together common requirements for managing flood works on a rural floodplain. Step 7 generally results in at least three different management zones, including:

• major flood discharge zone • flood storage and secondary flood discharge zone • flood fringe and existing developed areas zone. A general description of these three management zones is provided below.

Major flood discharge zone This zone typically:

• includes floodways that convey significant floodwater discharge during the small and large design floods

• is important for the conveyance of floodwater to floodplain assets during large and small flood events, including environmental flow releases and along natural flood flow corridors



• would be adversely impacted in by uncoordinated flood-work development in terms of flood behaviour

• ensures a reduction in the risk to life and property by limiting flood-work developments to prevent flood flow redistribution, increased flood velocities and flood levels

• ensures there is continuity of flow and flowpaths and assists in maintaining the overall flow distribution on the floodplain.

Flood storage and secondary flood discharge zone This zone typically:

• includes areas of the floodplain that are important for the temporary storage of floodwaters during the passage of a flood

• has an outer boundary defined by the inundation extent of the large design flood • is important for the conveyance of flood water to floodplain assets during larger flood events • is important to manage the cumulative and local impact of works on flood behaviour.

Flood fringe and existing developed areas zone This zone typically:

• includes areas outside of the inundation extent of the large design flood and existing developed areas

• contains flood-fringe areas where flood-work development is unlikely to have a significant effect on flood behaviour

• will require flood works to be assessed and approved to protect the health of the floodplain environment.

Approach to delineate management zones A three-stage approach is typically implemented to determine the nature and location of the zones in each of the floodplains. These stages include:

1. establish preliminary management zones based on hydraulic criteria. Criteria is to be based on flood behaviour and results from modelling

2. adjust management zones based on ecological criteria. Criteria is to determine which zone the ecological assets should be incorporated into and methods for adjusting management zones accordingly

3. adjust management zones based on cultural criteria. Criteria is to determine which zone the cultural assets should be incorporated into and methods for adjusting management zones accordingly.

The three-stage approach for developing the management zones considers the impact of existing and future development on flooding in rivers and floodplains; the flood risk to life and property; the flood connectivity of floodplain assets and the social and economic impacts of restricting flood-work development.

As required by the WMA 2000, this approach aims to strike an optimal balance between hydraulic, ecological, cultural, social and economic considerations. The zones and rules are designed to address local impacts as well as cumulative impacts. Furthermore, the number and type of zones is the minimum required to meet the management objectives.



Hydraulic criteria Preliminary management zones are established based on hydraulic criteria, which is developed from information on flood behaviour contained in the floodway networks.

Typically, three primary hydraulic categories are identified from the floodway networks (Figure 8 and 9):

• floodways: areas where a significant discharge of floodwater occurs during small and large design floods, such as in active river channels, adjacent floodplain flood runners and major overland flowpaths

• flood extent up to the large design flood: areas of the floodplain that are important for the temporary storage of floodwaters during the passage of a flood. The outer boundary is defined by the inundation extent of the large design flood.

• flood fringe and developed areas: areas outside of the floodway network that are typically outside the extent of the design floods and include the flood fringe as well as existing licensed developed areas.

Figure 8. Example of the floodway network from the Gwydir floodplain



Figure 9. Example of how the floodway network is translated into management zones based on hydraulic criteria only in the Gwydir floodplain

The preliminary management zones are founded on these three categories so that (Figure 9):

• the floodways becomes the most restrictive zone in terms of coordinating flood works (major flood discharge zone)

• the flood extent up to the large design event becomes the zone that would require detailed assessment to determine the potential impacts of flood works but would be less restrictive than the floodways (flood storage and secondary flood discharge zone)

• the flood fringe and developed area becomes the least restrictive zone in terms of coordinating flood works (flood fringe and existing developed areas zone).

The hydraulic criteria for management zones based on flood behaviour spatially captured in the floodway network are presented in the table below (Table 2).



Table 2. The hydraulic criteria for management zones based on flood behaviour.

Management zone

Hydraulic description Typical hydraulic criteria

Major flood discharge

Areas represented by significant discharge of floodwaters during small and large design floods.

Uncontrolled flood work development can have a high impact on flood behaviour.

This zone includes:

• areas that exceed the appropriate hydraulic threshold in a large design flood. Typically depth velocity product or discharge and velocity criteria have; and,

• parts of the small design flood extent that ensures continuity of the floodways.

Flood storage and secondary flood discharge zone

Inundation extent of the small and large design floods.

Uncontrolled flood work development has a moderate impact on flood behaviour; however, cumulative impacts can be significant.

This zone includes areas flooded by the large design flood events that are not classified as being in the high impact management zone.

Floodwater passage is dominated by major temporary floodwater pondage areas.

Some active flow paths are present.

Flood fringe and existing developed areas zone

Areas outside the floodway network.

Uncontrolled flood work development has a low impact on flood behaviour; however, cumulative impacts can be significant.

This zone includes areas of the floodplain that lie outside the extent of the large design flood.

Ecological and cultural criteria The refinement of management zones using ecological and cultural criteria uses the assessment outputs from identifying and prioritising floodplain assets in Step 4. The purpose of this refinement is to give key consideration to the risk that future development will impact flood connectivity to assets. This is because negative impacts may occur when floodwaters are blocked or diverted from reaching assets that are dependent on flooding.

This stage involves grouping high-priority assets with similar requirements for flood flows into common management zones. Cultural assets that are sensitive to disturbance from the installation or modification of flood works are not dealt with in the design of the management zones. Where identified, these assets will be an additional consideration for licensing staff when assessing flood-work applications.

Refinements to management zones were typically made based on the following:

Ecological criteria • ecological water flow corridors • ecological asset mapping recommendations for management zones



Cultural criteria • cultural assets identified by the community • Aboriginal values associated with living flood-dependent vegetation. If assets are not captured in the recommended zone, the management zones are generally amended to include unimpeded connectivity to the desired asset if there is hydraulic justification to do so. If the management zones cannot be amended then there are opportunities for developing rules that aim to protect flood connectivity to the asset (Step 7).

Ecological Criteria - ecological water flow corridors Ecological water flow corridors are tracts of floodplain land identified as important for conveying significant floodwater discharge during smaller flood events (less than 1 in 8 year ARI) through the floodplain and for watering connected flood-dependent communities.

The purpose of identifying the ecological water flow corridors is to include the corridors in the most restrictive management zone to protect the passage of water during smaller flood events. Where applicable, the ecological water flow corridors are consistent with the efforts of the OEH to implement environmental watering plans and consider ecological assets and values identified by the state.

The majority of all flood events that are likely to flow through the ecological water flow corridors will be derived from natural and regulated river flow. However, these corridors will also protect the passage of flood water actively managed by licensed environmental water deliveries in floodplains with environmental water allocations. It is the intention of the OEH Regional Water Team that the flow rates of delivered environmental water will be such that the delivered flow will be contained within the ecological water flow corridors. The rural FMPs do not control flow volumes or timing, but coordinate the development of flood works to protect the passage of water through the ecological water flow corridors.

Ecological Criteria - Ecological asset mapping recommendations The rural FMPs aim to ensure flood connectivity to wetlands, watercourses, floodplain ecosystems and areas of groundwater recharge is maintained or improved through coordination of new flood work developments or modifications of existing flood work developments.

All vegetation communities in the focus floodplains are dependent to a greater or lesser extent on flooding. This has led to the broad vegetation groups of the floodplains being distributed across the landscape according to their relative water requirements. The distribution of vegetation in the floodplains can be related to flooding patterns at two time-scales; in the short-term (months) driven by individual flood events and in the long-term (decades) driven by inundation frequency (Thomas et al. 2010).

For the purposes of the rural FMPs, ecological assets are categorised by taking into account priority assets identified by Marxan and their level of flood dependency, which is inferred by how frequently they are required to be flooded to maintain their ecological character (Figure 10). The flood dependency of ecological assets is then used to recommend a management zone (Figure 11). Management zones are recommended to reduce the risk of flood-work development adversely impacting on the frequency of flooding by blocking or diverting flows to assets. For instance, if an asset is a floodplain wetland that requires flooding every one to five years, it will be recommended to be in the most restrictive management zone.



The ecological refinement recommendations are compared to the management zones based on hydraulic criteria (Figure 12). Where there are inconsistencies, the management zones are generally only refined based on ecological mapping recommendations if the high priority asset:

• has a high selection frequency in the Marxan output or is identified as ecologically significant during consultation with regional and expert staff

• is flooded by the small design flood • can be connected to a flowpath identified through analysis of flood imagery • is adjacent to the recommended management zone. In all cases, these adjustments would be made because there is sufficient hydraulic justification (Figure 13 and 14).

Figure 10. Flood-dependent vegetation ecological values categorised according to flood dependency.



Figure 11. Management zone recommendations based on flood dependency

Figure 12. Comparison of recommendations with management zones based on hydraulic criteria



Figure 13. Comparison of ecological recommendations with flood imagery from a February 2000 flood event.

Figure 14. Final management zone refinements based on ecological and hydraulic criteria.



Cultural Criteria – cultural assets identified by the community High-priority cultural assets that were assessed as flood dependent or vulnerable to the passage of flood water are recommended for appropriate management zones. Generally, high-value cultural assets identified by the community were recommended for the major flood discharge zone.

Cultural Criteria – Aboriginal values associated with flood-dependent vegetation High-priority Aboriginal values, such as scarred trees, that are associated with living flood-dependent vegetation were referred to a management zone based on the level of flood dependency of the associated vegetation (see ecological asset mapping recommendations).



Summary of approach

Table 3 provides a general overview of the types of management zone criteria likely to be implemented as a result of the three-stage approach.

Zone Floodway network Hydraulic criteria Ecological assets criteria Cultural assets criteria

Major flood discharge zone

Floodways: areas where a significant discharge of floodwater occurs during small and large design floods

Areas that meet the threshold for the mapped depth-velocity product

Parts of a small design flood extent that ensures continuity of the floodways.

High-priority assets that have a high flood dependency, such as water courses and semi-permanent wetland

Places identified as high value by the community that are dependent on flooding

Flood-dependent assets, such as scarred trees that are in close proximity to floodways

Flood storage and secondary flood discharge zone

Flood extent: inundation extent of the small and large design floods

Areas flooded by small and large design flood events that are not classified as the Major flood discharge zone.

Assets that have a moderate flood dependency, such as flood-dependent woodland

Assets that have a moderate flood-dependency.

Flood fringe and existing developed zone

Flood fringe: areas outside the floodway network

Areas of the floodplain that were not flooded by a large design flood event.

Non flood-dependent vegetation is likely to occur.

Cultural assets that are impacted by flooding are likely to occur.



Step 8: Determine draft rules The management zones and rules together provide the legal framework for the Office of Water to determine flood-work applications. Step 8 is undertaken to develop specific rules to define the type and nature of flood works that can be constructed in each management zone. These authorised flood works are detailed in this step. The rules vary between management zones to reflect differences in flooding behaviour and the floodplain environment.

Existing flood-works are categorised into types of flood works, so that the rules can be tailored to ensure works likely to be approved would be fit-for-purpose. Categorising the types of flood works provides important information on the socio-economic benefits of flood works as well as the risk that a flood-work type would impact on flooding behaviour. This information is considered when developing the rules for each of the rural FMPs.

The rules can be split into three general types, including:

• flood works authorised, which relate to the physical nature of flood works • assessment criteria, which relate to the acceptable impacts of flood works • advertising requirements. The rules are developed by weighing up the socio-economic impacts of development controls against the potential for different types of flood works to impact on flooding behaviour.

Potential socio-economic impacts associated with management zones and rules will be mitigated by:

• defining flood works that can be applied for in each zone with respect to the social and economic impacts of development controls

• refining rules to coordinate the development of any new flood works • ensuring the proposed rules are reasonably consistent with existing floodplain management

arrangements. State-wide flood-work exemptions are also considered when developing the rules and assessment criteria for each management zone.

The rural FMPs are also supported by assessment guidelines to assist the Office of Water licensing officers when assessing flood-work applications against the rules.

Types of flood works For the purpose of the rural FMPs, flood works built on rural floodplains are categorised according to their nature and/or purpose. In this way, rules and assessment criteria can be tailored to ensure that the type of works likely to be approved would still be fit-for-purpose. The rules also ensure that landholders can, within reason, build flood works typically used to protect life and property.

Generally, six types of flood works are identified for the floodplains. The types of flood works and a brief description of their purpose are listed below:

• access roads: to ensure landholders have basic provisions to access property • below-ground supply channels: to ensure supply channels reach water sources so

landholders can access water rights • infrastructure protection works: to minimise risk to life and property.



• stock refuges: to provide for animal welfare and to minimise landholder’s potential to lose stock to flood waters

• other flood works: such as levee banks that are generally used for crop protection against larger floods.

Rules – authorised flood works The types of flood works that can be applied for in each management zone are determined by considering the optimal balance between hydraulic, ecological, cultural, social and economic considerations on the floodplain. Where there is a high risk that flood works will impact on flooding behaviour, restrictions are placed on the types of flood works that are authorised, such as in the major flood discharge zone. The restrictions on the types of flood works that are authorised are made to minimise the risk that flood works will impact flooding behaviour whilst being sympathetic to landholder needs. These decisions are checked against:

• the works likely to be approved under existing floodplain management planning arrangements

• targeted consultation with the community and interagency officers. For the major flood discharge zone, works will be able to be applied for where their purpose is critical for reducing the potential negative socio-economic impacts of flooding. Depending on the local issues in the floodplain, such works may be limited to flood works that have minimal impacts on hydraulic, ecological, cultural and socio-economic factors. Examples of the types of flood works that are likely to be authorised in the major flood discharge zone (albeit with restrictions) include:

• access roads • below-ground supply channels • infrastructure protection works • stock refuges. The flood storage and secondary flood discharge zone and flood fringe and existing developed areas zone are likely to allow for all types of flood works to be authorised. However, restrictions will depend on the specific flooding issues in the floodplain.

The rules in the FMPs also provide more detailed specifications for construction and nature for flood works that can be applied for. Table 4 provides examples of such management rule requirements.



Table 4. Management rule requirements that can apply to different types of flood works in the rural FMPs.

Work application Management rule requirements

Access road • specified height limits • causeway requirement. The number of causeways including spacing

distances may be stipulated.

Infrastructure protection work

• maximum size of work permitted may be based on property size • construction of a flood work must not block a floodway

Supply channel • specified height limits • structures may be required in the proposed flood work to permit passage of

flood water (e.g. siphon) • spoil removal requirement. Rule may stipulate how spoil should be managed

after a flood work has been constructed

Stock refuge • maximum size of work permitted may be based on property size • construction of a flood work must not block a floodway

Rules – assessment criteria These rules will follow a merit-based approach to assessing the potential impact of the specific flood-work on flooding behaviour. Rules relating to the acceptable impacts of flood works will be designed to consider the potential for a flood work to have:

• ecological and cultural impacts • drainage impacts • hydraulic local impacts • hydraulic cumulative impacts. The potential impacts to be assessed when determining a flood-work approval will depend on the type of flood work applied for and the management zone the flood work is located in.

Each rural FMP will consider flood behaviour, ecological, cultural and socio-economic factors when developing these types of rules. Consideration is also given to existing floodplain management plans and guidelines to identify existing assessment criteria and their applicability to the new rural FMP. Existing assessment criteria will be incorporated into the rural FMPs where possible.

The main factors considered when developing assessment criteria relating to the acceptable impacts of flood works are outlined in Table 5.



Table 5. Factors considered when developing assessment criteria.

Flood Behaviour Ecological and Cultural Socio-economic

• passage, flow and distribution of flood waters

• existing dominant flood ways and exits from flood ways

• rate of flow, floodwater levels and duration of inundation

• upstream and downstream water flows and levels

• spatial and temporal variability of flooding

• cumulative and local impacts of floodplain development on flood behaviour

• floodplain assets, such as wetlands and flood-dependent sites identified as important

• risk to flood connectivity of floodplain assets posed by existing and future development

• risk to fish passage and habitat for breeding and feeding

• the economic dependence of the local community on floodplain development

• risk to life and property from the effects of flooding

Rules - advertising requirements In the rural FMPs, some proposed management rules may have advertising requirements. These requirements will depend on the management zone that a proposed flood work is located in, as well as the nature and construction of the work. That is, whether the proposed works could cause or exacerbate flooding problems. Here local landholders have the opportunity to comment on flood-work applications that could adversely impact on flood behaviour. Landholders applying to construct flood works of a more minor nature will not be required to advertise their proposed works.

If a flood-work application will be required to be advertised, the application will be open to third-party objections. Third-party objections will be required to be considered by the Office of Water licensing officers when determining approvals. Advertising of applications will therefore be:

• positive for third parties who require opportunity to comment on flood works that may potentially impact a feature of the floodplain important to them

• potentially time-consuming and costly for applicants who receive objections to their applications and have to partake in mediations that may result in the work not being approved or changes being made to the work that was originally proposed.

Step 9: Consider existing floodplain management arrangements This step aims to ensure that there is adequate consistency between existing and proposed floodplain management planning measures. Here FMPs that are within the floodplain boundaries, as defined in Step 1, will be reviewed with respect to their development guidelines and flood studies. Table 6 lists examples of previous floodplain management arrangements that are being considered in the development of the rural FMPs.

New rural FMPs will supersede existing floodplain management plans. However, the new rural FMPs will be required to consider how flood work development has been managed by these plans to date. The rural FMPs will endeavour to be consistent with existing floodplain management arrangements.



Table 6. Key aspects of previous floodplain management arrangements considered in FMPs

Key aspect FMP management arrangements considered in FMPs

Floodplain management principles

Following FMP principles are considered:

• Defined flow paths must possess adequate hydraulic capacity and continuity to enable the orderly passage of floodwaters through the floodplain.

• Velocities of flood flows in defined flow paths should be minimised and be of an order that would not cause erosion or increased siltation under different land uses.

• Have due regard for current government policy and legislation.

• There should be no adverse impact from floodplain development on any individual landholder or community infrastructure. This includes increases in peak flood levels and increased drainage times. The exit of floodwaters from flowpaths should be at rates and depths similar to those that would be experienced under natural or historical conditions and should discharge as closely as possible to the natural or historical location.

Ecological and cultural heritage considerations

• As part of the identification and prioritisation of ecological assets, flood-dependent ecosystem mapping in the FMPs is considered.

• Information on Aboriginal and other heritage sites in the FMPs is considered.

Floodway networks/flowpaths

• Floodways identified in floodplain development guidelines are considered in the hydraulic design of the conceptual floodway network.

• Floodway networks and flow paths specified in the FMPs are integrated into the FMP floodway network to align them with management zones that restrict flood work development.

Hydraulic models • Hydraulic models underpinning FMPs are reviewed during FMP modelling studies.

Design flood event • Design floods in the FMPs are considered for adoption as large design floods in the FMPs subject to analysis of subsequent floods.

Types of works considered for approval

• The types of works considered for approval under current floodplain management arrangements are considered

Advertising requirements applications

• Floodplain areas where flood work applications require advertising under adopted FMPs will be considered for inclusion in management zones with rules that require advertising for flood works.

Assessment process/criteria for assessing flood work applications

• Assessment criteria for flood works in the FMPs are considered when proposing management rules for individual valleys with particular attention to incorporating hydraulic criteria that specify quantifiable limits.



Consideration of existing flood works Flood works on the floodplain that have been approved and constructed under existing floodplain management planning arrangements are considered in the proposed criteria for the delineation of management zones. Wherever possible, areas with existing flood work developments are incorporated into the flood fringe and existing development zone to prevent negative socio-economic impacts associated with flood-work development controls.

Step 10: Assess socio-economic impacts Step 10 is undertaken to determine if the combined impact of the proposed management zones and rules are equitable and to give due consideration to the social and economic impact of flood-work development in the floodplain and flood risk to life and property.

Socio-economic assessments measure the broad range of effects which may arise from changes in policy or practice. Balanced decision-making requires the integration and explicit recognition of social, economic and environmental impacts.

Socio-economic assessment is a tool used to predict the future effects of policy decisions upon people and can be used to assist in managing change. It provides a better understanding of the scale and distribution of costs and benefits of change and seeks to maximise positive effects and minimise negative effects resulting from this change.

In the preparation of the rural FMPs, socio-economic impact analysis is undertaken in two phases to ensure that the community has the opportunity to provide feedback on the potential socio-economic impacts and the mitigation strategies of the rural FMPs. The two phases are:

• phase one – preliminary assessment of socio-economic impacts, incorporating socio-economic feedback from targeted consultation

• phase two – socio-economic impact analysis, incorporating socio-economic feedback from public consultation.

These two phases will draw from the targeted consultation and public feedback processes undertaken in preparation and finalisation of the rural FMP and contribute to other steps undertaken in development of the plans. Preliminary socio-economic assessment includes targeted stakeholder consultation to identify concerns. This preliminary socio-economic assessment precedes and informs the draft plan, which will then be placed on public exhibition and feedback from interested stakeholders invited. Input from public consultation will contribute to revision of socio-economic assessment and development of impact mitigation strategies as required.

Phase one: preliminary assessment of socio-economic impacts The preliminary assessment of socio-economic impacts is coordinated with Steps 7, 8 and 9. This preliminary assessment ensures that socio-economic impacts are considered in the development of draft management zones and rules, and in the development of impact management and mitigation strategies where required.

The preliminary socio-economic impact analysis will involve:

• identifying likely sources of economic and social impact • evaluating issues and options by assessing social and economic effects of changes on the

community



• identifying potential effects of issues and options on the community • undertaking socio-economic impact assessment of proposed management zone scenarios

compared with the baseline assessment which represents the current situation i.e. pre rural FMP

• determining preferred options based on an understanding of goals and the relative benefits of each option and their distribution throughout the community. Consideration will also be given to ecological, cultural and hydraulic factors to ensure that a balanced outcome is achieved (see Step 8)

• documenting potential socio-economic impacts and options identified by the targeted community consultation.

A base-case is determined to compare the reform options against. The effect of a particular option is the difference between the socio-economic condition of the region under that option and the socio-economic condition of the region under the base-case, which is the ‘no reform’ scenario. The base case scenario provides a common reference point, or baseline, for comparison of diverse management options and evaluation of net impacts. It is needed to provide a basis for evaluating options.

Phase two: socio-economic impact analysis Phase two is undertaken following public consultation processes. This analysis will inform the refinement of the management zones and rules of the final rural FMP.

Community consultation will occur as part of public exhibition of the draft Plans. The community will have the opportunity to provide feedback on potential socio-economic impacts of the draft management zones and rules.

Presentation of draft plans for public review and feedback on the planning process will be used to verify and improve the accuracy of the data used, socio-economic impact predictions and to provide information so that adjustments and/or modifications can be made if necessary. Potential socio-economic impacts and/or options identified by the community through public consultation processes will undergo a socio-economic impact analysis. Effects initiated by changes in water management regimes will be identified and then the social and economic effects likely to occur if the identified options were implemented can be considered and addressed as required in the finalisation of the plan.

Other considerations

Exemptions Exempt works are those works declared by the Water Management (General) Regulation 2011 not to be a flood work and these works will not need approval under the WMA 2000.

Flood monitoring Monitoring of hydraulic flood behaviour should be undertaken to identify any problem areas and whether any changes to management zones or rules may be required. Depending on the size of the flood, monitoring would range from simple observation to measuring of flows and levels followed by additional hydraulic analyses.

For the larger floods, nearing the design flood levels, monitoring should be undertaken in more detail. In particular, as the hydraulic modelling has a significant degree of reliance upon flow estimates, especially peak flows, it will be important to collect data to verify these estimates. An effective monitoring program is to include:



• OEH undertaking aerial photography, collection of satellite imagery, survey, stream gauging and flow measurements, and

• where safe to do so, local councils and landholders observing flooding behaviour, including marking high flood levels, estimating flow velocities and taking photographs.

Following floods, landholders should estimate flood damage, including crop and fencing losses and damage to private roads. Council should provide an estimate of flood damage to public roads and infrastructure.

Flood monitoring guidelines for landholders The following advisory notes specify monitoring activities that should be undertaken by landholders, local councils and the OEH. The collected monitoring data will assist the rural FMP review process at the required five yearly intervals and after major flooding events. Where necessary, modifications to the rural FMP can be recommended based on the findings of the review process.

(a) Hydrologic and hydraulic data Flood event characteristics • note rainfall depths from private rain gauges throughout the storm event in order to obtain

total depth and temporal pattern. • note the start and finish times of flooding, as well as when the flood peak arrived. • note the duration of the flood peak (how long the peak lasted prior to receding). • compare the flooding with other flood events experienced.

Data near stream-flow gauging stations • note peak water levels from staff gauges (an average of a number of readings should be

taken). • take photographs illustrating flood extent and flow pattern.

Floodplain data • where possible peg flood peaks across the floodplain (e.g. flood marks or debris on strainer

posts, trees, farm sheds or dwellings). • note the extent and width of the flooding. • estimate surface flow velocities (usually expressed in metres per second) and where

possible note flow pattern. Velocities can be estimated by timing the movement of floating debris over an approximated length of travel.

• where possible measure flood water slope by pegging water levels over a length of one kilometre.

• note any obstructions to the passage of flood flow (e.g. roads, levees, banks), and where possible obtain estimated difference in water levels upstream and downstream of the obstruction.

• take photographs illustrating flow paths, flooded areas and dry areas, and flow near obstructions.

Note: Select floodplain monitoring sites that are near hydraulic controls such as roads, levees, major overbank flow breakouts, and at defined floodways.



Data along roads and at causeways or floodways • where flooded – estimate flow velocities and flow width over the road, as well as the

difference in water levels upstream and downstream of the road. • where dry – estimate the height out of water.

(b) Flood damage After a flood event, information is normally sought to assist in determining the nature and cause of any flood damage. Notes and sketches provided by landholders can aid this process.

Farm loss incurred • note the location of any damage and estimate the loss of crops and fencing.

Road damage • note the location and extent of pavement damage and silt over roads. • where possible estimate the length of road cuts.

Erosion and siltation • symptoms of stream bed lowering include vertical headcuts in the stream bed, • symptoms of stream bed lowering include vertical headcuts in the stream bed, extensive

bank erosion on both sides of the stream, headcuts in tributary streams and gullies, exposed gravel or rock beds, exposed pipe capping on bridge piers, and undermining of causeways.

• causes of stream bank erosion include flood flows and abrupt changes in channel alignment, gullying where overland flow enters streams, bed lowering, and obstructions to stream flow such as weirs or low level crossings.

• causes of floodplain erosion include unsustainable land-use practices (e.g. clearing), overflows from perched streams, or flow concentration due to floodplain development.

• causes of floodplain siltation include hill-slope erosion or reduced capacity of the main channel (bridge crossings, excessive vegetation or regrowth, influx of sediment), which result in in-stream sediment being deposited onto the floodplain.

Flood monitoring for local councils Road structures • note the head difference across the structure at peak and critical levels. • note the depth of flow over causeways. • estimate the flow velocity through or across the structure. • note whether the structure is affected by debris. • note the time when flow commences and finishes. • photograph the structure in flood. Following floods, Council should assess flood damage to roads and infrastructure: • note the location and extent of pavement damage and silt over roads. • estimate the length of road cuts where possible. • note damage to other infrastructure such as culverts or bridges.

Flood monitoring for the OEH Flood photography • undertake and obtain on-ground photography of the flood event. • if necessary, undertake oblique aerial photography of the flood event. • if necessary, organise vertical aerial photography of the flood event.



• obtain available satellite imagery of the FMP floodplain under flood.

Survey data • collate existing survey data undertaken or organised by DECCW, landholders, or local

councils. • if necessary, obtain additional survey data, particularly in the vicinity of new flood control

works (storages, levees, channels, etc.) and structures (bridges, culverts, weirs).

Consultation activities • undertake consultation activities with stakeholder groups (landholders, government agencies,

local councils, and other interest groups) to source their opinion on the flood event and the performance efficiency of the FMP floodway network.

• undertake field investigations after flood events to view identified problem areas.

Flow data • obtain flood heights and discharge records from gauging stations within the vicinity of the

floodplain. • if necessary, obtain rainfall data from the Bureau of Meteorology and the Office of Water

records.

Environmental monitoring Environmental monitoring during and after floods will help to determine if the rural FMP is adequately providing flood flow connectivity to ecological and cultural assets and help to assess the ecological impacts of local flooding. Environmental data would mainly consist of observations with supporting photography wherever possible. The scale of flooding would influence the extent of data collected. For example, in a large flood, observations of wetland inundation, waterbirds and fish would be extensive in comparison to a relatively small flood. The OEH should collate environmental data from local councils, landholders and other agencies. Council and landholders could observe, for their areas of the floodplain:

• wetland inundation • waterbirds and fish presence, and • regeneration of floodplain vegetation.

Wetland data • note and photograph any changes to the flooding and drying patterns of the wetland. • note how long the wetland holds water after a flood event. • measure and note how deep the water is in the wetland at different times. • note and photograph the condition and variety of wetland plant species over time.

Floodplain vegetation (black box, river red gum, lignum) data • note and photograph the extent of floodplain vegetation regeneration over time. • note and photograph the extent of flood inundation in the vicinity of floodplain vegetation.

Waterbird and fish observations • at key sites, such as wetlands, note the abundance and diversity of waterbird species. The

easiest method is to group the waterbirds into ducks, grebes, cormorants, etc. and count by 10s, 50s or 100s.

• at key sites, such as wetlands and waterways, note the abundance and diversity of fish species. Dip-netting is the simplest way to monitor small fish in wetlands.



For more information on monitoring wetlands, waterbirds and fish refer to the NSW Murray Wetlands Working Group (2002) document titled Wetlands Watch: A Field Guide for Monitoring Wetlands in the Southern Section of the Murray–Darling Basin. Environmental monitoring for the OEH.

Environmental data Fish and aquatic invertebrates • obtain information regarding fish abundance and diversity within the vicinity of the floodplain.

This data can be sourced from Industry and Investment NSW (Fisheries) who undertake sampling on a regular basis.

• obtain information regarding the abundance and diversity of macroinvertebrates within the vicinity of the FMP floodplain. This data can be sourced from the existing program titled AusRivAS (Australian River Assessment System), which generates health assessments for river sites based on the presence of macroinvertebrates.

Vegetation • based on flood photography and field investigations, assess changes in floodplain vegetation

following flood events. Additional data • approach government agencies in order to source any relevant environmental data gathered

by them in response to a flood event. This may include data in relation to fish, water quality, floodplain vegetation, waterbird observations and wetlands.

Other considerations

Existing works The Office of Water is beginning the process of transitioning from the floodplain management plan and controlled works provisions of Part 8 of the WA 1912 to the equivalent provisions under the WMA 2000.

Under the WMA 2000, flood work approvals replace approvals for controlled works under Part 8 of the WA 1912. Other than this change in terminology, the process for applying for a flood work approval is similar to the process for applying for a Part 8 approval.

The WMA 2000 includes transitional provisions to ensure that actions taken and approvals granted under Part 8 of the WA 1912 remain valid once the WMA 2000 comes into effect. In effect, controlled work approvals granted under the WA 1912 will convert to flood work approvals under the WMA 2000.

No action on the part of the holder of a controlled work approval is needed to maintain the validity of their approval.



Exemptions The Office of Water is proposing exemptions from the requirement to hold a flood work approval for certain minor flood works or flood works that are important for the protection of life or property. Those exemptions would apply statewide and would become part of the Water Management (General) Regulation 2011. Flood works proposed to be exempt are:

• Flood works constructed by the State Emergency Service. This exemption is proposed to apply to all management zones in floodplain management plans and is an existing exemption under the WA 1912.

• All flood works within a town boundary defined as the boundary shown on the plans held by Lands Titles Office. This exemption is proposed to apply to all management zones in floodplain management plans.

• Earthworks less than 150 mm above natural surface level including farm tracks and check banks. This exemption is proposed to apply only outside of recognised floodways in floodplain management plans published prior to 1 January 2015 and outside of management zones A and D in floodplain management plans made on or after 1 January 2015.

• Ring embankments around homes and farm infrastructure enclosing not more than 2 hectares in area and comprising not more 10% of the total property area (whether individually or as a collection of embankments). Farm infrastructure is to be defined as sheds and storage silos. This exemption is proposed to apply only outside of recognised floodways in floodplain management plans published prior to 1 January 2015 and outside of management zones A and D in floodplain management plans made on or after 1 January 2015.

• Public roads and railways. This exemption is proposed apply to all management zones in floodplain management plans.

The NSW Office of Water will publish the proposed exemptions on its website www.water.nsw.gov.au and request comment before finalising the exemptions.

Hotspots Hotspots are areas of the floodplain where existing flood works may be creating adverse impacts on flood flow behaviour, and may also adversely impact cultural and/or ecological assets. Subject to receipt of funding, a strategy for investigating and prioritising hotspot areas identified through the floodplain management planning process will be developed during Stage 2 of the NSW Healthy Floodplains project. Identified hotspot areas may be targeted for remediation work in order to minimise the impacts on flood flows. Stage 2 of the Healthy Floodplains Project may also provide financial assistance for implementing remedial actions to hotspot areas.

http://www.water.nsw.gov.au/



References Ball IR and Possingham HP. (2000). MARXAN (V1.8.2): Marine Reserve Design Using Spatially Explicit Annealing, a Manual. University of Queensland, St Lucia Q.

Ball, I.R., Possingham, H.P. and Watts, M. (2009). Marxan and relatives: Software for spatial conservation prioritisation. Chapter 14: Pages 185-195 in Spatial conservation prioritisation: Quantitative methods and computational tools. Eds Moilanen, A., K.A. Wislon, and H.P. Possingham. Oxford University Press, Oxford, UK.

Council of Australian Governments (COAG) (2004) International Agreement on a National Water Initiative.

Dahm C, Bouton A, Correa L, Kingsford R, Jenkins K, Sheldon F (2013). The Role of Science in Planning, Policy and Conservation of River Ecosystems. In River Conservation Challenges and Opportunities. S Sabater and A Elosegi (Eds). ISBN 978-84 -92937 -47 -9.

Department of Infrastructure, Planning and Natural Resources (DIPNR) (NSW), (2005). Floodplain Development Manual: the management of flood liable land. Crown Copyright. ISBN 0 7347 5476 0

Mein R and Nathan R (2010). Runoff Routing Program. RORB Version 6.14. Monash University and Sinclair Knight Mertz. http://eng.monash.edu.au/civil/research/centres/water/rorb/

Margules CR and Pressey RL. (2000). Systematic conservation planning. Nature 405: 243–253.

Possingham HP, Ball I, and Andelman SJ (2000). Mathematical Methods for Identifying Representative Reserve Networks. Pages 291-305 In Quantitative Methods for Conservation Biology. S Ferson and MA Burgman (Eds). Springer-Verlag, New York.

Thomas, R., Bowen, S.F., Simpson, S., Cox, S., Sims, N., Hunter, S. and Lu, Y. (2010). Inundation response of vegetation communities of the Macquarie Marshes in semi-arid Australia. Pages 137-150 in N. Saintilan and I. Overton, editors. Ecosystem response modelling in the Murray-Darling Basin. CSIRO Publishing, Collingwood.

http://eng.monash.edu.au/civil/research/centres/water/rorb/



Appendix 1 Rural floodplain management planning approach under the Water Management Act 2000



Glossary Aboriginal values are sites, objects, landscapes, resources and beliefs that are important to Aboriginal people as part of their continuing culture.

Annual Exceedance Probability is the chance of a flood of a given or larger size occurring in any one year, usually expressed as a percentage (%) or a likelihood of 1 flood in x years. For example, a flood with an AEP of 5% means there is a 5% chance that a flood of same size or larger will occur in any one year or 1 every 20 years.

borrow is an area of land where material is excavated or removed to construct a flood work at another location. The removal of material from this area results in a depression or ‘hole’ in the ground. connectivity refers to the unimpeded passage of floodwater through the floodplain. Connectivity is important for instream aquatic processes and biota and the conservation of natural riverine systems. cultural asset is an object, place or value that is important for people to maintain their connection, beliefs, customs, behaviours and social interaction.

design flood is a flood of known magnitude or annual exceedance probability (AEP), that can be modelled. A design flood is selected to design floodway networks which are used to define management zones for the planning and assessment of the management of flood works on floodplains. The selection is based on an understanding of flood behaviour and associated flood risk. Multiple design floods may be selected to account for the social, economic and ecological consequences associated with floods of different magnitudes.

discharge (or flow) is the rate of flow measured in volume per unit of time (e.g. megalitres per day = ML/day). ecological assets are a wetland or other floodplain ecosystem, including watercourses that depend on flooding to maintain their ecological character. Areas where groundwater reserves are recharged by flood waters are also considered to be ecological assets. Ecological assets are spatially explicit and are set in the floodplain landscape. ecological values are surrogates for biodiversity that were used to prioritize the ecological assets and included fauna and fauna habitat, vegetation communities and areas of conservation significance

ecosystem is a biological system involving interactions between living organisms and their immediate physical, chemical and biological environment. fish passage refers to connectivity that facilitates the movement of native fish species between upstream and downstream habitats (longitudinal connectivity) and adjacent riparian and floodplain areas (lateral connectivity). Areas that are important for fish passage include rivers, creeks and flood flow paths. flood-dependent assets refers to assets that have been identified in the plan as having important ecological or cultural features which rely on inundation by floodwaters to sustain essential processes.

flooding regime refers to the frequency, duration, nature and extent of flooding. floodways are areas where a significant discharge of floodwater occurs during small and large design floods.

groundwater recharge areas are areas where water from a flood event leaks through the soil profile into the underlying aquifers heritage sites are cultural heritage objects and places as listed on Commonwealth, State and local government heritage registers.



infrastructure protection works refer to flood works that are for the protection of houses, stock yards and other major infrastructure, such as machinery sheds.

management zones are areas in the floodplain that have specific rules to define the purpose, nature and construction of flood works that can occur in those areas. natural surface level is the average undisturbed surface level in the immediate vicinity.

recharge means the addition of water, usually by infiltration, to an aquifer. windrow refers to a row or line of material.

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