NAMOI RIVER STYLES REPORT River Styles, Indicative Geomorphic Condition and Geomorphic Priorities for River Conservation and Rehabilitation in the Namoi Catchment, North-West, NSW

SEPTEMBER, 2004

Guy Lampert and Amalia Short

Namoi River Styles i Namoi River Styles ii Table of Contents

SECTION ONE: EXECUTIVE SUMMARY...... 1

SECTION TWO: INTRODUCTION...... 3

SECTION THREE: METHODS...... 5

SECTION FOUR: REGIONAL AND CATCHMENT SETTING...... 7 4.1 OVERVIEW...... 7 4.2 GEOLOGY AND LANDSCAPE UNITS………………………………………………………….……..……….7 4.3 VEGETATION AND LAND USE ...... 13 4.4 CLIMATE...... 15 4.5 HYDROLOGY……………………………………………………………………………………………….16

SECTION FIVE: DEFINITION AND INTERPRETATION OF RIVER STYLES IN THE NAMOI CATCHMENT ...... 19

SECTION SIX: THE DISTRIBUTION OF RIVER STYLES IN THE NAMOI CATCHMENT ...... 117

SECTION SEVEN: INDICATIVE CONDITION OF STREAMLINES IN THE NAMOI CATCHMENT ...... 126

SECTION EIGHT: GEOMORPHIC PRIORITIES FOR RIVER CONSERVATION AND REHABILITATION IN THE NAMOI CATCHMENT...... 139

SECTION NINE: CONCLUSIONS AND RECOMMENDATIONS...... 148

REFERENCES…………………………………………………………………………………………………152

APPENDIX 1: RELATIVE ABUNDANCE OF RIVER STYLES IN EACH LANDSCAPE UNIT…………………………………………………………………………...…155

APPENDIX 2: LONG PROFILES FOR SELECTED STREAMLINES…………………………..………159

APPENDIX 3: THE RIVER STYLES APPROACH TO PRIORITISATION……………….…………165

Namoi River Styles iii Acknowledgments

This report was funded by the Nation Action Plan for Salinity and Water Quality as an interim priority project from the Namoi Catchment Blueprint (Namoi Catchment Management Board, 2003). The Department of Infrastructure, Planning and Natural Resources (DIPNR) provided in-kind support which included financial management, office space and access to resources such as vehicles and aerial photography.

Thanks are due to several people from the Department of Infrastructure, Planning and Natural Resources (DIPNR) in the Barwon Region who assisted in the production of this report. We would like to acknowledge the assistance of Angela McCormack and Katherine Kerr who provided GIS support, Stephen McLane from Inverell Resource Centre for the timely provision of aerial photography, David Outhet from CNR and Kirstie Fryirs from Macquarie University for their technical input and review, Sue Powell for initial project management and Neal Foster for his discussions on all things riverine. Special thanks also to Nathan Penny, Tim Watts, Peter Dawson, Glenn Bailey and Robert Albert for the input of their local knowledge on riparian issues. Lastly, we would like to thank George Schneider from the Hunter Region for the excellent discussions regarding the setting of priorities for river rehabilitation and management.

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Namoi River Styles iv Section One: Executive summary River Styles

River Styles provides a geomorphic summary of river character and behaviour primarily based on the relationship between channel and valley morphologies and broader landscape controls. This provides a physical template upon which a range of other biophysical attributes can be analysed. In conjunction with an assessment of the indicative geomorphic condition of rivers, such a biophysical framework provides a sound basis for developing river conservation and rehabilitation priorities within a catchment.

River Styles in the Namoi Catchment

The River Style analysis of the Namoi catchment has assessed around 10 thousand kilometres of named stream length. From this, 23 different River Styles have been identified in the Namoi catchment. These have been divided into four broad categories based largely on valley morphology. Namely confined, partly-confined, laterally-unconfined and discontinuous.

Indicative Geomorphic Condition of River Styles in the Namoi Catchment

A broad-brush assessment of geomorphic condition was undertaken of the streamlines examined in this study. As this was largely an assumptive process the term “indicative condition” was adopted, based on three broad categories of condition – good, moderate and poor. From this assessment approximately 20% of the assessed streamlines in the Namoi catchment are in good indicative condition, 50% are in moderate indicative condition and 30% are in poor indicative condition.

Geomorphic priorities for river conservation and rehabilitation in the Namoi catchment

In this report, the determination of River Style and indicative condition of assessed streamlines in the Namoi catchment has provided for a geomorphic basis for prioritising river conservation and rehabilitation efforts. While this process has only considered the geomorphic basis for setting priorities, it is acknowledged that further filters should be applied to account for triple bottom line considerations. The geomorphic filters used to prioritise streamlines in the Namoi catchment can be condensed into four main categories:

• Conservation Priority filters • Strategic Priority filters • High Priority Rehabilitation filters • High Priority Remeditation filters • Moderate/Low Priority Remeditation filters

As the Namoi catchment is spatially large, it is recommended that conservation and rehabilitation actions be targeted initially at areas where the greatest success and continuity of effort is most likely to be achieved. These are, as determined by areas where there is a concentration of Conservation and Strategic Priority reaches:

• Upper Macdonald: the Macdonald River and its tributaries upstream of the confluence with Spitzbergen Creek. • Cockburn River tributaries: the Cockburn River and its tributaries upstream of the confluence with Mulla Mulla Creek. • Upper Ironbark Creek: Ironbark Creek and its tributaries upstream of the confluence with Nangahrah Creek. • Maules Creek: Maules Creek and its tributaries upstream of the confluence with Horsearm Creek. • Pillaga Outwash streams: this covers most streamlines crossing the Pillaga Outwash landscape unit from Mollee (or Nuable) Creek in the east to Box Creek in the west.

Namoi River Styles 1 Due to the relatively coarse resolution of this assessment, it is recommended that these areas be initially assessed in greater spatial detail. This would determine stream recovery potential and the exact nature of threats and pressures, allowing for more specific management actions to be developed for the high priority areas. Of these areas, priority for further assessment and action should be given to the Pillaga outwash streams and the Upper Macdonald as these areas contain a high proportion of fragile and rare River Styles respectively.

It is tendered that the five main priority categories can be used as a basis for allocating funds for river conservation and rehabilitation activities. It is recommended that funding in the short term be apportioned with a bias towards Conservation and Strategic Priority reaches to account for the more detailed assessments required in the high priority areas. However, in the longer term, allocating funds equally to the four main priority categories will ensure a balance between the needs of the rivers and those of the local communities in the Namoi catchment.

Additionally, in order to define catchment-framed goals for river rehabilitation in the Namoi catchment, the following general river management recommendations are made:

1. Encourage and support river management actions that protect identified Conservation reaches through the removal of threatening processes.

2. Encourage the implementation of appropriate rehabilitation and preventative actions in Strategic reaches.

3. In High Priority Rehabilitation reaches promote low cost rehabilitation works such as fencing, revegetation and weed management that maximise improvements to river condition and work with natural river processes.

4. In High Priority Remediation reaches efforts should be made to slow or stop degradation through appropriate changes in land management.

5. Discourage activities that are known to greatly exacerbate channel instability including gravel extraction, snag removal, riparian vegetation disturbance and channel and flow diversions.

6. In Moderate/Low Priority Remediation reaches rehabilitation efforts should only be initiated once they are considered a priority after other triple-bottom line filters have been applied. Furthermore, these reaches will not improve in condition without significant, costly intervention. The geomorphic character and behaviour of these reaches is poor and in some cases irreversibly altered. Realistic management goals should be established once degrading influences have been removed or after the successful rehabilitation of adjoining reaches.

7. Where available use the good condition reaches of each River Style to guide target conditions for river rehabilitation efforts in more disturbed river reaches, ensuring that the local setting and catchment position is appropriate (eg similar catchment areas, gradients, hydrologic and sediment regimes). Along regulated rivers, rehabilitation goals must account for the altered hydrologic regimes

8. Where major engineering rehabilitation works are proposed a cost-benefit analysis and risk assessment should be undertaken to determine whether investing in such works is of the public interest. Any analysis must account for triple-bottom line considerations and be consistent with the principles of Economical Sustainable Development.

Namoi River Styles 2 Section Two: Introduction

This report provides an assessment of the geomorphic character and behaviour of the major rivers and streams in the Namoi River catchment, north-west NSW. The procedures employed follows Stage 1 of the River Styles framework as detailed in Brierley and Fryirs (2003). The primary objectives of a Stage 1 River Styles assessment are: • Collation, analysis and presentation of relevant catchment characteristics such as geology, landscapes, climate, hydrology, land use and vegetation cover. • Identification and interpretation of river character and behaviour (River Style) within the catchment. • Presentation and assessment of the distribution and controls on River Styles within the catchment.

Additionally, this report provides a preliminary, ‘broad-brush’ assessment of the geomorphic condition of major streamlines in the Namoi catchment. Although neither comprehensive nor detailed, this condition assessment has been used to identify high priority areas to be assessed to Stage 4 of the River Styles procedure.

Purpose

River Styles provides a geomorphic summary of river character and behaviour primarily based on the relationship between channel and valley morphologies and broader landscape controls. This provides a physical template upon which a range of other biophysical attributes can be analysed. In conjunction with an assessment of the indicative geomorphic condition of rivers, such a biophysical framework provides a sound basis for developing river conservation and rehabilitation priorities and improving river management decision-making within a catchment.

Scope

It is necessary to appreciate the resolution at which this assessment has been undertaken. The scales at which maps are produced in this report are unable to display variations of less than several kilometres. Hence, this assessment has not been carried out at a reach scale and does not cover every single streamline within the Namoi catchment. Furthermore, as a general rule, this assessment has endeavoured to consolidate rivers with similar character and behaviour, rather than split river character and behaviour into an unwieldy, multitude of different types.

For the purpose of improving mapping resolution, the Namoi catchment has been split into five sub- catchments as displayed in Figure 1.1. This report presents maps of River Styles, indicative geomorphic condition and geomorphic conservation and rehabilitation priorities at varying scales for each of the five sub-catchments as follows:

• the Peel sub-catchment; • the Mooki sub-catchment; • the Macdonald/Manilla sub-catchment; • the Middle Namoi sub-catchment and; • the Lower Namoi sub-catchment.

Namoi River Styles 3 Namoi River Styles 4 Section Three: Methods

Office-based assessment

Broad-scale maps (1:100 000 and 1:250 000) are used to analyse catchment scale data including regional geology, drainage networks and topography. These investigations provide an initial ‘feel’ for the region and the distribution of landscape units within the catchment. Other influences including climate, hydrology, vegetation and land use are also considered during this stage. Following initial analyses, long profiles are produced, using Arcview and Excel, for selected river courses to analyse downstream changes in elevation and gradient. The final step in this stage of assessment is the analysis of 1:25 000 and 1:50,000 topographic maps to observe valley morphology, channel planform and floodplain shape prior to air photograph interpretation.

Aerial photograph interpretation

Aerial photographs are used to break river courses down into their respective valley settings (confined, partly-confined, laterally-unconfined and discontinuous). Within each valley setting, River Styles are identified on the basis of channel and floodplain character. The steps used in this process are outline in Figure 3.1 which shows that valley setting or channel continuity are the first level of assessment. Once this is determined, more specific attributes are examined to establish specific River Styles for each streamline in the assessment. Observed boundaries are pencilled-in on a topographic maps (1:25 000 or 1:50,000), these boundaries note changes in River Styles. It is important to note that not all geomorphic units can be picked out from the air photographs either due to the scale of resolution, an obstruction (eg vegetation or cloud) or subtle changes in relief (eg levees).

Confined valley Partly-confined valley Laterally-unconfined valley Discontinuous setting setting setting (absent or discontinuous (>90% of channel abuts (10-90% of channel abuts (<10% of channel abuts valley channel) valley margin) valley margin) margin)

presence/absence of degree of lateral confinement river planform geomorphic units floodplain pockets and valley configuration (straight vs irregular vs sinuous)

geomorphic units river planform geomorphic units valley floor texture

bed material texture geomorphic units bed material texture

bed material texture

Figure 3.1: The River Styles Procedural Tree (adapted from Brierley and Fryirs, 2003)

A broad-scale assessment of river condition (termed indicative condition) is also undertaken at this stage. This requires significant geomorphic insight and is based on the expected or natural range of variability for different River Styles. For example, channel erosion is natural along some rivers and is therefore part of its natural range of behaviour. Indicative condition is assessed from observable features including channel stability (eg. eroding banks), geomorphic features (eg. sediment slugs) and presence/condition of riparian vegetation.

Namoi River Styles 5 Field analysis

Field reconnaissance of the catchment is then carried out. Important outcomes from this stage of assessment include an improved understanding of the dynamics of the entire catchment, and further ratification of River Styles and condition boundaries identified earlier from the map and air photograph interpretation. The steps outlined in Figure 3.1 are also followed during this stage of assessment. Changes to original boundaries are made if aerial photograph interpretation does not match attributes observed in the field.

The second step in field analysis is the selection and assessment of representative reaches. A representative reach is selected for each River Style and a range of attributes noted. These include channel dimensions, bed and bank sediments, vegetation type and coverage, valley width and the type and assemblage of geomorphic units. This data is recorded on a standard proforma sheet. In most cases representative reaches exhibit good indicative geomorphic condition, display the range of geomorphic units for the River Style and have good site accessibility.

Post field analysis

Collected data is collated and catchment-scale maps of the distribution of River Styles and indicative condition are produced in Arcview. During this process air photographs may be revisited to reconfirm boundaries in inaccessible areas. Stream power estimates for each representative reach were calculated using the Geomorphic Assessor developed by Adolphe Parfait. This program uses the channel cross-section and Mannings N estimates to derive a stage-discharge rating from which stream powers can be calculated. Several tables and graphs are produced to analyse relationships between River Styles, indicative condition, landscape units and sub-catchments. These provided insights into patterns and controls on the distribution of River Styles within the Namoi catchment. This information is then used to develop catchment-wide priorities for river conservation and rehabilitation based on the philosophies and principles (Appendix 4) of Brierley and Fryirs (2000).

Namoi River Styles 6 Section Four: Regional and catchment setting

4.1 Overview

The Namoi catchment (Figure 4.1) is located in the central north of New South Wales within the Murray-Darling Basin. The catchment extends 350km west from the Great Dividing Range to the Barwon River and drains a catchment area of approximately 43,000km2 (Olley and Scott, 2002). It is bounded by the Gwydir catchment to the north, the Macleay and Manning catchments to the east, the Hunter catchment to the south-east and the Macquarie and Castlereagh catchments to the south. The Namoi River is a major left bank tributary of the Barwon River contributing an average 800,000 ML yr-1 (Thoms, 1998) to the Murray-Darling system.

TAMWORTH

SYDNEY



050 100 200 300 400 Kilometers

Figure 4.1: Location of the Namoi catchment within New South Wales.

4.2 Geology and Landscape Units

There is a complex and dynamic relationship between rivers and the landscapes over which they flow. Over long time frames, in the context of Eastern Australian, rivers and streams are the principle agents of landform change, shaping landscape features such as slope, relief and valley width. While over shorter time frames, these landscape features in turn affect stream morphology, influencing stream energy, sediment availability/transport and the ability for rivers to develop floodplains and deform their channels. This interdependence means that an understanding of river character is best determined by analysing river morphology in context with the regional landscapes in which they occur.

The landscape units in the Namoi catchment were determined by analysing slope classes derived from a 25 metre DEM (Digital Elevation Model) and a generalised geology layer of the catchment within a GIS environment. The output of this analysis is shown in Figure 4.2. From this, 7 broad landscape units were delineated within the Namoi catchment (Figure 4.3). A summary description of the

Namoi River Styles 7 attributes of each landscape unit in the Namoi catchment is provided in Table 4.1, while a brief qualitative description of each landscape unit is presented below:

Uplands: This relatively high elevation landscape is largely drained by the Macdonald River and its tributaries. It is dominated by granitic geologies with meta-sediments and some basalts occupying the upper part of the Macdonald River catchment (ie upstream of Woolbrook). Topography is variable, with some areas being relatively rugged with steep, high relief hills (eg Moonbi Gap area), while other areas have a more subdued morphology of rolling, moderate relief hills (eg Woolbrook area). As a result, valley morphologies are also variable ranging from steep, bedrock confined channels to relatively wide, alluvial valleys. This results in a mixed denundational/ aggradational landscape, where in some places rivers are actively incising into the landscape, providing a source of sediments, other areas are sites for sediment storage over moderate to long time frames (ie > 1000 years).

Rugged Meta-sediments: This landscape unit occupies the west facing escarpment of the Great Dividing Ranges and is dominated by meta-sediment geologies. It is a denundational landscape of high relief with narrow ridge crests and steep hillslopes. Valley floors are generally narrow (< 100 m) but can be up to 1000 m along the major streams (eg Peel and Cockburn Rivers). The steep slopes result in considerable delivery of sediments to streams which flow within generally confined and partly confined valleys. The steep slopes and shallow regolith/soils combine to give this landscape relatively high runoff rates resulting in highly variable discharges with peaked flood hydrographs. Floodplains are absent or discontinuous in this landscape, resulting in limited sediment storage.

Rugged Volcanics: This landscape unit occupies the ridges and hills of the Liverpool, Warrumbungles and Mt Kaputar Ranges. Although similar in morphological characteristics to the Rugged Meta-sediments landscape unit, it is dominated by volcanic geologies (sandstones can outcrop on the lower slopes, especially in the Mt. Kaputar area). These geologies tend to have greater infiltration rates resulting in reduced runoff rates and more attenuated flood discharges. However, the steep slopes and confined valleys combine to generate relatively highly peaked flows. Again, steep slopes result in the significant delivery of sediments to valley floors, which are often mantled by coarse cobble and boulder deposits. Sediment storage is usually limited to small pockets of floodplain that can be reworked over short to moderate timeframes (ie 10 – 1000 years).

Middle to Lower Peel: This is a low to moderate relief landscape dominated by meta-sediment geologies occupying an area between Tamworth and the Melville Range that extends from upper Goonoo Goonoo Creek in the south to Borah Creek in the north. It is a mixed denundational/ aggradational landscape with gently to moderately inclined hillslopes and rounded ridge crests. Valley floor widths are generally between 50 to 200 metres, but can be up to 2000 metres along the Peel River. Due to the gentle hillslopes, relatively small amounts of sediment are delivered to the streams with most stored in local sinks, though these can be subject to reworking, especially when disturbed. Stored sediments along the major streamlines have been largely sourced from the upstream Rugged Meta-sediments landscape unit. Although hillslopes are gentle, the relatively thin regolith/soils mean that runoff rates can be relatively high resulting in peaked and variable stream discharges.

Liverpool Plains: This landscape unit is largely aggradational and is dominated by the relatively flat, low-lying alluvial sediments that make up the Liverpool Plains. Outcropping from the alluvium are numerous bedrock outliers, largely composed of either volcanic geologies (eg Mullaley Hills) or sandstones (eg Trinkey Hills). These outcrops exhibit rolling to steep hillslopes with local relief ranging from 20 to 400 metres. Alluvial fans occupy the footslopes of these bedrock outliers, as well as the lower slopes of the Liverpool Ranges.

Pillaga/ Pillaga Outwash: The area generally known as the Pillaga consists of two distinct landscapes, the dissected Pillaga sandstone plateau and the alluvial Pillaga outwash. The former is a denundational landscape of rolling to steep hills with local relief of up to 150 metres. Valley floor widths are generally narrow but can be up to 500 metres wide along Baradine Creek where the stream has incised through the Pillaga Sandstone to expose the less erosion resitant Purlawaugh Formation.

Namoi River Styles 8 The steep slopes and shallow regolith/soils combine to give this landscape relatively high runoff rates resulting in highly variable discharges with peaked flood hydrographs.

The Pillaga Outwash is an aggradational landscape, being the product of tens of thousands of years of the deposition of sediment sourced from the erosion of the Pillaga Sandstone plateau (Hesse and Humphreys, 2001). It is a low lying landscape of undulating alluvial sediments, where local relief does not exceed 10 metres. It is traversed by numerous south to north-west trending drainage lines, many being abandoned palaeo-channels reflecting changes in climatic conditions during the Quaternary period. Most sediment within the streams of this landscape is derived from upstream or as a result of reworking of the broad outwash plain.

Lowland Plain: This is an aggardational landscape of low relief consisting of flat to gently undulating alluvial plains. It consists of expansive alluvial deposits traversed by a network of generally west trending abandoned and present day river channels. The abandoned Quaternary river systems, have remnants slightly elevated with respect to the modern systems, and are the most extensive component of the present day plains landscape (RACAC, 2002). These palaeo channels provide evidence of a dynamic and continually changing river system, where the Namoi River has migrated widely across its floodplain moving progressively southwards over time (Young et al., 2002). Sediment along contemporary channels has been derived from upstream or as a result of reworking of the expansive floodplains.

Namoi River Styles 9 ao ie tls10 Styles River Namoi Figure 4.2: Generalised geology and slope class association of the Namoi Catchment. ao ie tls11 Styles River Namoi

Figure 4.3: Distribution of Landscape Units in the Namoi catchment. ao ie tls12 Styles River Namoi

Table 4.1: Summary attributes of Landscape Units in the Namoi Catchment.

Landscape Uplands Rugged Rugged volcanics Middle to lower Pillaga/ Pillaga Liverpool plains Lowland plain Units metasediments Peel Outwash

Attributes

Landscape Rolling to steep Moderate to steep Moderate to steep Gently undulating to Low lying plateau Flat, low-lying Flat, low-lying character granite and metasediment volcanic escarpment, rolling hills on meta- dissected with plains with outlying alluvial plains metasediment escarpment, ranges ranges and foothills sediments relatively shallow hills and ranges uplands and foothills and and associated valleys with gently associated valleys valleys sloping outwash plain Landscape Tablelands/ Upper to middle Upper catchment Middle catchment Middle catchment Middle catchment Lower catchment, position Moonbi Range catchment positions positions occupying position position occupying occupying the west of Narrabri occupying dominantly the ridges dominantly the area Liverpool Plains dominantly the and escarpments of known as the Pilliga area Melville, Moonbi and the Liverpool Nandewar Ranges Ranges, Warrumbugles and Mt Kaputar Geology Dominantly Dominantly meta- Volcanics Meta-sediments Sandstones and Alluvial plains with Alluvial plains granites with meta- sediments with some conglomerates, with outlying hills and sediments and granite in the Moonbi outwash composed of ranges composed of some volcanics area alluvial sediments. dominantly occupying the sandstones and upper Macdonald volcanics catchment Relief upto500m 200–600m 200–650m 50–150m <150m <400m <10m Elevation >800 400to1000 500to1000 300to700 200to600 200to600 130to 200 Hill(mASL) Slopes >3 >3 >3 <5 1-5 >3 <1 Valley Slopes Flat to <5 Flat to <5 Flat to <5 Flat to <3 Flat to <3 Flat Flat Valley Widths 5–1000m <500m <500m <2000m <500m Upto10km Upto75km 4.3 Vegetation and Land use

Role of Vegetation It is widely recognised that vegetation has a significant influence on river form and processes. At a catchment scale, vegetation on slopes and floodplains slow surface flows and protect the soil from erosion. Removal of vegetation from a catchment leads to less interception and infiltration of rainfall. The flow on effects are: • more peaky runoff • higher energy flows • more erosive power • channel degradation/expansion • disconnection of channel from floodplain

Riparian vegetation, which is any vegetation that is adjacent to a watercourse, has a more direct impact on river geomorphology. It is the final layer of protection and if continuous, adequately wide and structurally intact, it can buffer the impacts of broad-scale clearing of surrounding slopes and floodplains. A structurally intact riparian corridor will slow run off and trap sediment, reducing the erosive power and sediment reaching the channel. It also has several important roles once the water is in the channel: • stabilises the toe of bank and protects it from erosion • protect banks and benches from erosion • prevents bank collapse by promoting drainage • stabilises instream features including islands and benches • instream trees add roughness to the channel and create flow and bed form diversity • source of LWD which creates flow and bed form diversity • add organic matter to the soil increasing the cohesion of clays • improves the recovery potential of a reach

These roles have a direct impact on river morphology, creating variations in bed form and flow, providing habitat diversity that is essential for healthy river systems.

Vegetation in the Namoi Catchment Prior to European settlement there was a complex array of vegetation communities within the Namoi catchment. This was associated with variations in altitude, temperature, rainfall, moisture availability, geology and soil (Thoms, 1998; Caitecheon et al., 1999). Since European settlement the majority of the catchment has been cleared or thinned for cropping and grazing. Remnant vegetation is now limited to areas where agriculture is restricted, due to inaccessibility (eg tablelands) or low soil fertility (eg Pilliga forest). Along many streamlines riparian vegetation corridors are thin and discontinuous or non-existent. Where a riparian corridor has been maintained it is often structurally compromised and/or dominated by exotics (eg. willows).

A brief summary of past and current vegetation in the Namoi catchment is provided below for each sub-catchments.

Peel sub-catchment : The steep slopes of the upper catchment are timbered, with either remnant or regrowth wet sclerophyll forests which are dominated by Eucalyptus fastigata (Brown Barrel), E. obliqua (Messmate) and E. viminalis (Manna Gum). This area also supports periodically logged Pinus radiata (Radiata Pine) plantations. A complex pattern of Red Stringy Bark (Eucalyptus macrorhyncha), White Box (E. albens) and Yellow Box (E. melliodora) communities was found across the rugged to gently undulating hills of the middle to lower catchment (SCSNSW, 1979). The majority of this area has been cleared or thinned for grazing, the forest and woodland systems have typically been reduced to scattered trees. A wide riparian corridor of Blakely’s Red Gum (E. blakelyi) or Yellow Box-White Box-Blakely’s Red Gum community was present along major streamlines (SCSNSW, 1979). Today, a narrow discontinuous riparian corridor is usually all that is maintained, this is often dominated by Casuarina cunninghamiana (River Oak) and is rarely structurally intact.

Namoi River Styles 13 Along the floodplains of the major streamlines, including the Cockburn and Peel rivers lucerne crops often extend to the top of the bank. Refer to Tamworth Technical Manual (SCSNSW, 1979) for a detailed map and description including species lists for the vegetation communities mentioned.

Macdonald/ Manilla sub-catchment: The main forest associations in the eastern tablelands are Messmate, Eucalyptus macrorhyncha (Red Stringy-bark), Manna Gum and E. stellulata (Black Sallee) (Caitecheon et al., 1999). A significant proportion of the tablelands is still timbered (approximately 21%), this is mainly on the steep slopes where soil fertility and inaccessibility have limited agricultural development (Donaldson, 1996). In the western section of the catchment around Barraba and Manilla, there are two distinct vegetation communities. The Red Stringbark/Red Gum Dry Sclerophyll Forest and Tall Woodland along the north and east edges and a White Box- Tall Woodland and Savannah Woodland community through the middle. Only remnants of the original vegetation remain, as the vast majority has been cleared for agriculture. Streamlines with structurally intact riparian zone are restricted to the upper parts of the sub-catchment. Refer to Manilla District Technical Guide (SCSNSW, 1972) and Barrabra District Technical Manual (SCSNSW, 1973) for a detailed map and description including species lists for the vegetation communities mentioned.

Mooki sub-catchment: The rugged terrain of the Liverpool Ranges in the upper Mooki catchment still support near intact Grey box- White Box-Yellow Box- Blakely’s Red Gum community (SCSNSW, 1975; Caitechton et al., 1999). The lower slopes of these hills have been almost completely cleared. Prior to European settlement the flat country of the Liverpool Plains was predominantly Plains grass community (Stipa aristiglumis) with White Box community and White Box-Cypress Pine (Callitris hugelli) community on more elevated ground (SCSNSW, 1980; SCSNSW, 1976). The grasses were long enough to be plaited above the neck of a horse, they were therefore very effective slowing floodwaters (Wallbrink et al., 1999). Today only isolated stands of these communities remain on alluvial fans and in flood prone areas (Caitechton et al., 1999). Most of this area has been cleared for cropping which often extends to the stream edge, subsequently little riparian vegetation remains (Caitecheon et al., 1999; Olley & Scott, 2002). Refer to Murrurundi District Technical Manual (SCSNSW, 1975), Quirindi Technical Manual (SCSNSW, 1980) and Gunnedah District Technical Manual (SCSNSW, 1976) for a detailed map and description including species lists for the vegetation communities mentioned.

Middle Namoi sub-catchment: In the northern section of this catchment the rugged terrain of the basalt ranges supports the intact vegetation communities of Mount Kaputar National Park. The rest of the catchment, which is predominantly the broad alluvial Liverpool plains supported Plain grass community and Yellow Box- White Box- Bimble Box (E. populnea) community until the 1950’s when large areas were replaced with dryland cropping or cleared for grazing (SCSNSW, 1976; Caitecheon et al., 1999). Today small remnants of Plains grass are rare and Box communities are limited to travelling stock/roadside reserves and only isolated stands in paddocks. The White Cypress Pine community associated with the sandy skeletal soils of the Pilliga Sandstone has been left relatively intact. Refer to Gunnedah District Technical Manual (SCSNSW, 1976) for a detailed map and description including species lists for the vegetation communities mentioned.

Lower Namoi sub-catchment: The Lower Namoi comprises two distinct areas, the Pilliga scrub and the lowland plains. Prior to European settlement the Pilliga was dense scrub periodically burned by aborigines. The Pilliga is now the largest remaining area of tree cover in the catchment (Donaldson, 1996). The area is largely covered with regrowth forest, dominant species include White Cypress Pine, Eucalyptus creba (Narrow-leaved Ironbark), E. trachyphoia (Brown Bloodwood), Blakely’s Red Gum, E. pilligaensis (Pilliga Box) and Casuarina luehmannii (Bull Oak) with an extensive variety of hardy understorey species (Donaldson, 1996; Thoms, 1998; Caitechton et al., 1999). In the past this area was heavily logged, today, much of the forest has regrown and is protected within the Pilliga Nature Reserves and National Parks. Smaller forestry operations continue within the Pilliga State Forest. In recent times the outwash has been cleared to allow more intensive grazing.

The alluvial land of the lowland plains was sparse to open Eucalyptus coolabah (Coolibah) woodland, or grasslands dominated by Astrebla lappacea (Mitchell grass) or Plains grass. Most this area has now

Namoi River Styles 14 been cleared for cropping and grazing (Donaldson, 1997; Thoms, 1998; Caitecheon et al., 1999). Today the floodplains are dominated by cotton and wheat crops. Travelling stock and roadside reserves support remnants of the original vegetation communities. Early settlers noted that the Namoi River was lined with trees and shrubs and the channels contained numerous fallen trees (Olley & Scott, 2002). Today only major streams have a narrow riparian zone supporting Eucalyptus camaldulensis (River Red Gum), Acacia stenophylla (River Coolah), Atalaya hemiglauca (Whitewood), Casaurina cristata (Belah), White Box and Grey Box.

Land Use in the Namoi catchment Land use in the Namoi Catchment is dominated by agriculture, with approximately 50% of the catchment used for livestock grazing and a further 23% for cropping. Of the remaining area 25% is timbered and the rest is urban area, a water body, mining site or infrastructure (ie roads) (Thoms, 1998). The main towns are Tamworth, Gunnedah, Narrabri, Manilla, Quirindi and Walgett.

Livestock grazing in the Namoi catchment arrived with European settlement, by the 1880’s grazing pressure was intense, this was accompanied by deforestation as timber was in high demand for fencing (Caitcheon et al., 1999). Intense grazing pressure was exacerbated by the arrival of rabbits in the early 1900’s, which inhibited regeneration of timbered areas (Caitcheon et al., 1999). Today most grazing is on native pasture, with only limited areas under improved pasture and fodder crops. The main impacts of livestock on streamlines are through trampling river banks and inhibiting the regeneration of native trees.

Initially cropping in the Namoi catchment was limited to sandy loam and some red earth soils (Olley & Scott, 2002). In the early 20th Century several improvements, in both equipment and crop varieties, lead to the expansion of cropping, including wheat and cotton, into the areas of heavy black cracking clays (Caitcheon et al., 1999). Today grain, fibre and fodder crops dominate the flat fertile alluvial country around the towns of Gunnedah and Narrabri. There is also a substantial irrigated lucerne industry around Tamworth and Manilla. In some areas cropping extends to the top of the bank.

Forestry is also an valuable industry within the catchment. Logging operations are centred around softwood plantations in the Nundle area and hardwood timbers of the Pilliga. Mining is the other important primary industry. Although mining only occupies a small area of the catchment (<0.1%), the impacts in terms of sedimentation and erosion are high. The main mining areas are coal near Gunnedah and limestone at Attunga (Donaldson, 1997). Sand and gravel extraction from river channels was previously uncontrolled. Today extraction requires a permit and is limited to areas that will not affect the stability of the channel bed and banks (eg inactive gravel bars and bars above the normal low flow water level) (Lyons, 1996). A gradual phasing out of extraction is planned.

4.4 Climate

Daily temperature and annual evaporation both increase across the catchment in a westerly direction. In January average daily temperatures can range from 19°C in the east to 34°C in the west, in July they range from 4 to 17°C, respectively. Variations in altitude also influence temperature, at elevations above 900m daily temperatures are 4 to 5°C lower than in the west (Thoms, 1998).

As shown in Figure 4.4, average annual rainfall decreases from east to west across the Namoi catchment. Rainfall decreases from 1200mm p.a at the top of the Great Dividing Range, to 600mm to 700 mm p.a. around Tamworth down to 450mm p.a. at Walgett in the west. Temporal variations in rainfall also occur. Rainfall occurs in all months of the year but on average 40% more rain falls in summer months than in winter months (Olley & Scott, 2002). Summer rainfall is typically of high intensity and short duration, floods are therefore common in the summer months (Thoms, 1998). Longer term variations in rainfall have also been observed, such that periods of decadal magnitude exhibit higher or lower than average rainfall.

Namoi River Styles 15 WALGETT

WEE WAA
NARRABRI
BARRABA

BOGGABRI
MANILLA

BARADINE
GUNNEDAH

MULLALEY TAMWORTH

WERRIS CREEK

QUIRINDI
Legend - Average Annual Rainfall, Namoi Catchment, 5mm Isohyets Isohyet Classes (mm) < 500 500 - 650 650 - 800 800 - 1000 > 1000 012.5 25 50 75 100  Kilometers

Figure 4.4: Average annual rainfall for the Namoi catchment.

4.5 Hydrology

A catchment’s hydrology, or discharge regime, is a fundamental control on river processes and behaviour. Key discharge factors include: • the total volume of water conveyed • discharge variability over a range of time-scales, and • the frequency, magnitude and duration of flow events.

These factors are important controls on the physical, chemical and biological attributes of a river system (Thoms, 1998). Consequently, developments, which alter the natural hydrological regime of a catchment, have significant impacts on river forms and function. In the Namoi catchment these developments include changes in land use, the construction of dams and weirs and water extraction. A river systems response to these changes will depend on how the flow regime has been affected.

The important role of vegetation in intercepting and slowing delivery of rainfall and run-off to streamlines was discussed in briefly in Section 4.3. Since European settlement significant changes in vegetation cover have occurred across the Namoi catchment. A major modification has been the removal of extensive areas trees, shrubs, grasses and perennial ground cover and it’s replacement with pasture and annual crops. This has reduced the interception and infiltration of rainfall and resulted in increased run-off and more peaky, higher energy flows. In a study of the Liverpool Plains Wallbrink et al. (1999) found that contemporary flood hydrographs show floods are bigger, peak earlier and are of shorter duration than pre European settlement. These flows have more erosive power which may lead to channel enlargement, through increased rates of bank and bed erosion, and the disconnection of channels from their floodplains.

In the Namoi catchment flows are regulated by three major water storages in the middle to upper parts of the catchment. These are: • Keepit Dam on the Namoi River upstream of the Peel River confluence, built in 1960 with a maximum storage capacity of 427,000 ML.

Namoi River Styles 16 • Spilt Rock Dam on the Manilla River, built in 1988 with a maximum storage capacity of 397,000 ML. • Chaffey Dam on the Peel River upstream of Woolomin, built in 1979 with a maximum storage capacity of 62,000 ML.

In addition to these large dams there are some smaller dams (including Dungowan and Quipolly). All of the dams impound water and trap sediment. The location of the dams capitalises on the distribution of run off in the catchment. In the Namoi catchment surface run-off corresponds closely with the rainfall isohyets shown in Figure 4.4. Most run-off is generated in the headwater regions, with 90% sourced from 40% of the total catchment area (Thoms, 1998).

The implications of water impoundment on downstream reaches is decreased flood frequency, magnitude and duration. As water is generally released in quantities and at times to meet community requirements. These changes in discharge regime have direct impacts on geomorphic forms and processes as water is the main agent for channel adjustment. Channel changes predominantly occur when the channel is in flood. The response to a decreased frequency of channel forming flow events is one of reduced bed scour, resulting in channel contraction, the smothering of gravels by silt and the infilling of pools with sediment.

The other major impact of dams is the trapping of sediment. It is calculated that Keepit and Split Rock dams trap up to 97% of incoming sediment and Chaffey dam traps about 59% (Thoms, 1998). These statistics are an overall figure for suspended and bed load sediment, due to dam design the proportion of bed load sediments trapped is likely to be close to 100%. An implication of reduced sediment supply on downstream reaches includes channel degradation due to starvation, as bed load is transported downstream but not replaced by upstream sources.

Downstream of Keepit dam a series of weirs regulate flow at Mollee, Gunidgera and Weeta (Donaldson, 1997; Thoms, 1998). These weirs are used to improve the precision of water supply, raise water levels to divert flows (into Pian and Gunidgera Creeks) and to store water for downstream irrigators. There are also four privately owned weirs in the Gunidgera-Pian Creek system (Thoms, 1998).

The final major impact on catchment hydrology is water extraction. Surface water and groundwater are extracted for irrigation and stock/domestic use. A probable impact of water extraction on catchment hydrology is one of reduced flows between floods, when the proportion of water extracted is large in relation to discharge. In the Namoi catchment the impacts of water extraction are demonstrated by a reverse trend in discharge. Generally, annual flows will increase with increasing catchment area but downstream of Gunnedah annual flows decrease due to water use, increased evaporation and transmission losses (Thoms, 1998).

Namoi River Styles 17 Namoi River Styles 18 Section Five: Definition and Interpretation of River Styles in the Namoi Catchment

The River Styles analysis of the Namoi catchment has assessed around 10 thousand kilometres of named stream length. From this, 23 River Styles have been identified in the Namoi catchment. These can be divided into four broad categories based largely on valley morphology as follows:

Confined valley River Styles • Headwater • Gorge • Floodplain pockets • Confined valley sand

Partly-confined valley River Styles • Bedrock controlled, gravel • Bedrock controlled, sand • Bedrock controlled, fine grained • Planform controlled , low sinuosity cobble • Planform controlled, low to moderate sinuosity gravel • Planform controlled, low sinuosity sand • Planform controlled, meandering fine grained

Laterally-unconfined valley River Styles • Low sinuosity, gravel • Low sinuosity, sand • Low sinuosity, fine grained • Wandering, gravel • Wandering, sand • Meandering, gravel • Meandering, fine grained • Anabranching, meandering fine grained • Channelised fill

Discontinuous River Styles • Floodout • Lowland chain of ponds • Valley fill

The primary attributes that define each River Style identified in the Namoi catchment are summarised in Table 5.1. River Styles trees have been produced for each sub-catchment and are shown in Diagrams 5.1 to 5.5. These trees show the pathway to identify each River Style, starting with valley setting and moving through to bed materials. Each River Style has been given a diagnostic name that synthesises river character.

The following section provides a detailed outline and interpretation of the character and behaviour for each River Style. A summary proforma has been produced that describes the cahracter, behaviour and controls of each River Style across the catchment. A representative reach has also been analysed in more detail.

Namoi River Styles 19 River Style Planform Channel geometry Bed materials Bank/floodplain materials Number of Lateral stability Sinuosity channels Confined valley setting Headwater 1 Stable Low Symmetrical to Bedrock floor Bedrock irregular with boulders through to sands Gorge 1 Stable Variable, Symmetrical to Bedrock floor Bedrock/ Terrace valley irregular with boulders controlled through to sands Floodplain Pockets 1 Stable Low Symmetrical to Bedrock with Bedrock or alluvial asymmetrical where gravel or sand banks fines with floodplains occur bedload gravel Confined valley, sand 1 Stable, potential for Low Symmetrical Sand with some Bedrock localised expansion fines Partly-confined valley setting Bedrock controlled, 1 Stable, potential for Generally low, Symmetrical to Bedrock with Bedrock or alluvial gravel localised channel expansion dictated by asymmetrical on bends gravel bedload banks fines gravel valley base Bedrock controlled, 1 Stable, potential for Generally low, Compound or irregular Bedrock with Bedrock or alluvial sand localised channel expansion dictated by sand bedload banks fines/sands valley Bedrock controlled, 1 Stable, potential for Generally low, Symmetrical Bedrock with Bedrock or alluvial fine grained localised movement dictated by cobbles/gravels banks fines valley Planform controlled, 1 Relatively laterally stable, Low Symmetrical Cobbles and Bedrock or alluvial low sinuosity cobble adjusts through channel gravels banks composite expansion cobble/gravel over laid by fines Planform controlled, 1 Relatively laterally stable, Low to Symmetrical to Gravel Bedrock or alluvial low-moderate sinuosity adjusts through channel moderate asymmetrical on bends banks are composite gravel expansion gravels overlaid by fines Planform controlled, 1 Laterally stable, adjusts Low Symmetrical Sands Bedrock/terrace or low sinuosity sand through channel expansion alluvial banks sands and fines Planform controlled, 1 Relatively laterally stable, Moderate to Trench-like Cohesive fines Bedrock or alluvial meandering fine adjusts through avulsion high symmetrical banks cohesive fines grained Laterally-unconfined valley setting Low sinuosity, gravel 1 Laterallyactive,adjusts Low to Compound to Gravel armoured Cohesive fines through channel expansion moderate asymmetrical and/or avulsion Low sinuosity, sand 1 Relatively laterally active, Low Symmetrical to Sands with Fine sands and adjusts through channel compound, low width scattered gravels organic matter expansion and/or avulsion /depth ratio Low sinuosity, fine 1 Relatively laterally stable Low- Symmetrical to Cohesive fines, Cohesive fines grained moderate compound may have scattered gravels Wandering, gravel up to 5 Multiple channel thalweg Macrochannel Macrochannel is Gravels, cobbles Sand and silt with shifts within a relatively is low. compound. Primary and boulders gravel lenses stable macrochannel. and secondary channels are symmetrical Wandering, sand 3 or more Multiple channel thalweg Macrochannel Macrochannel is Sands with some Fines shifts within a relatively is low. compound and gravels stable macrochannel irregular. Primary and secondary channels are symmetrical Meandering, gravel 1 Typically adjusts through Moderate to Compound, Gravels with Composite gravels lateral migration processes high symmetrical to some sands overlaid by fines asymmetrical on bends Meandering, fine 1 Laterally stable, slow rates Moderate to Symmetrical to Fines Cohesive fines grained of lateral migration high aymmetrical on bends Channelised fill 1 Laterally stable Low Symmetrical or Fines or sands Fines and sands compound Anabranching, 3 or more Laterally stable channels Moderate to Symmetrical to Fines and sands Cohesive fines meandering fine that adjust through avulsion high asymmetrical on bends grained Discontinuous Valley fill no channel Prone to incision Low Symmetrical Organic rich fines Bedrock Lowland Chain of usually 1 but Laterally stable, prone to Low Symmetrical Organic rich sand Organic rich sand ponds up to 3 incision and fines and fines Floodout n/a Prone to incision n/a n/a Muds and silts n/a Table 5.1: Summary of attributes for each River Style.

Namoi River Styles 20 ao ie tls20 Styles River Namoi Diagram 5.1: Peel sub-catchment valley settings and River Styles

Confined valley setting Partly-confined valley setting Laterally-unconfined valley setting Discontinuous channel

single continuous channel no floodplain occasional sinuous or spurred relatively straight or no channel diverging shallow and valley irregular valley channels which narrow alluvial fan dissipate onto floodplain channel along valley low sinuosity high sinuosity confined by fans/swamps, pockets margin 50-90%, channel along valley valley walls, no defined waterfalls, steep stepped margin 10-50%, channel cascades, sections (falls, featureless plunge pools, boulder bars) swampy fill pools, riffles, surface riffles and alternating bedrock steps, pool/riffle long pools, low high sinuosity laterally stable laterally active runs, bars with lower bank attached sequences, gravel riffles, sinuosity mud/sand and benches sloped sections bars, benches compound cascades, long pools mud/sand (pools, riffles and ledges, bars and bars, benches separated by and rapids) islands, scour benches and islands, no defined forced short riffles long pools, Floodout pool/riffle pools, riffles, bars Valley fill features on dissected by levees, flood or glides, floodplain chute channels and sequence, riffles, benches and trench-like pool/riffle dissected by bedrock, bedrock, pockets channels, backswamps cascades, point bars, ledges, channel with sequences, chute channels, bars, benches gravel lags, boulder, gravel boulder, gravel compound on undercut bars and bars, benches and ledges, levees, flood floodplain floodplains concave sand sheets, benches, laterally active with terraces and ledges, active and banks, active generally inset channels and laterally stable Gorge generally relict featureless features, relict features Headwater bedrock with and relict featureless floodplain floodplain active and on floodplain gravel or sand sand features on bedrock and floodplains features floodplain relict gravel floodplain gravel features pool/riffle long shallow Floodplain Bedrock sand/mud sequences, point pools separated pockets controlled, cobble gravel fine sand, silt Bedrock fine sand, and bank attached by muddy riffles, sand and clay controlled, silt and clay bars, benches with point bars and gravel chute channels, benches with Low sinuosity, active and relict chute channels, Channelised gravel features on flood channels fill Planform Planform Planform Low floodplain controlled, controlled, controlled, sinuosity, low low – meandering fine grained sinuosity moderate fine grained gravel fine silt and clay cobble sinuosity gravel Meandering, Meandering, gravel fine grained ao ie tls21 Styles River Namoi  90 Diagram 5.2: Macdonald/Manilla sub-catchment valley settings and River Styles

Confined valley setting Partly-confined valley setting Laterally-unconfined valley setting Discontinuous

single continuous channel no floodplain occasional sinuous or spurred relatively straight or no channel diverging narrow and valley irregular valley channels which shallow alluvial fan dissipate onto floodplain low sinuosity high confined by fans/swamps, no pockets channel along valley channel along valley sinuosity valley walls, defined channel waterfalls, steep stepped margin 50-90% margin 10-50% cascades, sections (falls, featureless plunge boulder bars) swampy fill laterally laterally surface pools, alternating pools, riffles, stable active mud/sand riffles and with lower bedrock steps, low high runs, bars sloped sections sinuosity sinuosity bank attached pool/riffle long pools, long forced Floodout and (pools, riffles bars, benches sequences, gravel riffles, pools separated mud/sand benches and rapids) and ledges, compound cascades, bars, by bedrock islands, scour forced pools, long pools point bars benches and sills, benches trench-like pool/riffle long pools, Valley fill features on riffles, point separated by and point islands, levees, with chute channel with sequences, riffles, bars floodplain bars, benches short riffles or bedrock, benches, flood channels channels, bars and bars, dissected by laterally boulder, pockets and ledges, glides, benches bedrock, chute and levees and sand sheets, benches, chute stable gravel active and and ledges, boulder, channels, backswamps flood channels relict undercut generally inset channels, gravel compound on floodplain floodplain concave banks, featureless features, gravel lags, floodplain features active and floodplain active and levees, flood laterally Bedrock with with terraces relict features relict channels and active long shallow pools Headwater gravel or sand sand on floodplain features on relict separated by muddy bedrock, floodplain features on riffles, point bars Gorge cobbles, gravel gravel floodplain and benches with gravel and fines pool/riffle sequences, chute channels and Floodplain Bedrock fine sand, silt sand/mud point and bank flood channels pockets controlled , and clay fine sand, silt attached bars, benches sand Bedrock Planform and clay with chute channels, Bedrock controlled, controlled, low- gravel active and relict controlled , features on floodplain fine sand, silt and fine grained moderate Planform gravel clay sinuosity gravel controlled, Channelised meandering fill Low sinuosity, Low fine grained fine grained sinuosity, gravel gravel Meandering, fine grained Meandering, gravel ao ie tls22 Styles River Namoi

low sinuosity Diagram 5.3: Mooki sub-catchment valley settings and River Styles

Confined valley setting Partly-confined valley setting Laterally-unconfined valley setting Discontinuous

no floodplain occasional sinuous or spurred relatively straight or single continuous channel multiple channels narrow and valley irregular valley no channel diverging shallow channels which floodplain dissipate onto pockets channel along valley channel along valley low sinuosity high sinuosity alluvial fan fans/swamps, waterfalls, steep stepped margin 50-90% margin 10-50% confined by no defined cascades, sections valley walls, channel plunge (falls, laterally stable laterally featureless pools, boulder bars) pools, riffles, pool/riffle low sinuosity active swampy fill riffles and alternating bedrock steps, sequences, surface mud/sand runs, bars with lower bank attached compound laterally laterally and sloped bars, benches point bars and active stable benches sections and ledges, point benches, no defined forced pools, mud/ Floodout (pools, riffles islands, scour chute channels, pool/riffle riffles, point sand trench-like pool/riffle long pools, and rapids) features on compound sequence, bars, benches channel sequences, riffles, bars pool/riffle long shallow floodplain floodplain with cascades, bars, and ledges. with bars bars, dissected by sequences, pools pockets terraces benches and active and point and separated by Valley fill bedrock, islands, relict and sand benches, chute sheets, inset channels, bank muddy boulder, generally floodplain bedrock, generally features, gravel lags, attached riffles, point gravel gravel featureless features boulder, featureless active and levees, flood bars, benches bars and floodplain gravel bedrock with floodplain relict channels and with chute benches with gravel or sand features on relict channels, chute Headwater active and channels low sinuosity gravel floodplain features on floodplain relict macrochannel zone Bedrock cobble with a primary Floodplain controlled, features on channel and up to 4 pockets gravel floodplains fine sand, silt fine sand, silt secondary channels Gorge and clay gravel and clay Planform Planform controlled, sand and controlled, low- moderate mud planar bed with scour holes, primary and low sinuosity sinuosity Low sinuosity, Low sinuosity gravel Meandering, secondary channels cobble gravel fine grained gravel fine grained separated by bars, islands and floodplain segments Channelised fill Meandering, gravel Wandering, gravel swamps valley fill diverging mud/sand perched on Floodout discrete fans/ channels onto channels segments Discontinuous incision separated by bars, mud/sand holes, primary and secondary channels featureless no channel surface, no swampy fill planar bed with scour Wandering gravel and up to 4 secondary islands and floodplain Valley fill low sinuosity macrochannel zone with a primary channel multiple channels    long point channels separated and clay fine grained with chute Meandering, shallow pools laterally stable channels, flood fine sand, silt bars and benches by muddy riffles, sand Low sinuosity , sand chute channels, levees small bars, benches with planar mobile sand sheet, high sinuosity d River Styles gravel laterally active gravel features and bank pool/riffle floodplain Meandering, benches with attached bars, chute channels, active and relict sequences, point gravel laterally active features Low sinuosity, gravel flood chute Laterally-unconfined valley setting Low benches, channels channels, and clay long pools, riffles, bars lateral bars, sinuosity, sand sheets, gravel lags, levees, flood fine grained single continuous channel fine sand, silt dissected by chute channels, channels and relict floodplain low sinuosity fill inset laterally stable features, sand/mud floodplain featureless trench-like sand sheets, channel with Channelised ledges, concave undercut or glides, and relict fine sand, Planform floodplain long pools features on controlled, short riffles high sinuosity silt and clay benches and separated by meandering fine grained banks, active irregular valley margin 10-50% relict gravel gravel relatively straight or channel along valley features sinuosity Planform active and floodplain and ledges, controlled, riffles, point forced pools, low sinuosity bars, benches low-moderate Partly-confined valley setting gravel gravel 50-90% Bedrock pool/riffle sinuous or floodplain compound compound sequences, controlled , valley margin channel along point bars and spurred valley point benches, chute channels, Diagram 5.4: Middle Namoi sub-catchment valley settings an LWD margin, features sand sand bed, Confined associated featureless with valley small scour valley, sand vegetation or generally flat and shallow floodplain pockets occasional narrow with sand bars, scour pools, riffles, islands, pockets bedrock benches bedrock attached gravel or floodplain features on steps, bank and ledges, Floodplain pockets bars) steep (falls, gravel sloped Gorge boulder stepped sections sections boulder, bedrock, alternating with lower (pools and Confined valley setting and pools, gravel no floodplain plunge benches boulder, bedrock, cascades, runs, bars riffles and waterfalls, Headwater

Namoi River Styles 23 sand mud/ which channel swamps, channels dissipate diverging Floodout onto fans/ no defined surface Valley fill featureless no channel alluvial fan valley wall, swampy fill confined by mud/sand and organic matter sandy splays ponds chain of and sand channels, Lowland mud/sand bottom of at top and pools, flood pools/ponds swamp, bars separated by backswamps Discontinuous high grained bar/bench floodplain complexes long pools, sinuosity anabranches channels and separated by gravel riffles, several flood fines and sand laterally stable Anabranching, channels meandering fine laterally stable fine sand, silt and clay benches with chute, flood multiple channels Meandering , fine grained muddy riffles, point bars and sand sand long shallow pools separated by stable channels is laterally bars, ridges and islands, and terraces with several separated by Wandering, cris-crossing low sinuosity macrochannel macrochannel flood channels River Styles® sand sand levees planar channels, with chute sheet, small mobile sand gravel Low sinuosity, bars, benches high sinuosity laterally active features on floodplain Meandering, gravel gravel relict chute gravel pool/riffle sequences, point and chute channels, active and relict features bank attached bars, benches with channels, floodplain Laterally-unconfined valley setting long pools, riffles, bars gravel lags, dissected by laterally active levees, flood channels and Low sinuosity, bars, inset relict single continuous channel features, benches, fine sand, pool/riffle sequences active and floodplain fine grained features on silt and clay Low sinuosity, low sinuosity fill laterally stable bars and generally sand/mud floodplain featureless trench-like Channelised sand sheets, channel with or sand along low valley margin channel 10-50% valley straight terraces Planform irregular sinuosity channels, relatively scour pools, sinuosity sand backswamps, islands, flood controlled, low riffles, bars and riffles relict Bedrock gravel gravel features floodplains sinuosity Planform active and floodplain and ledges, controlled, islands, levees, riffles, point forced pools, backswamps on bars, benches sand with gravel riffles, cascades, controlled, sand low-moderate bars, benches and long pools, gravel flood channels and 50-90% Partly-confined valley setting sinuous or spurred valley channel along valley margin gravel gravel Bedrock pool/riffle floodplain compound compound sequences, controlled, Diagram 5.5: Lower Namoi sub-catchment valley settings and point bars and point benches, chute channels, sand valley margin, vegetation or LWD sand bed, small scour Confined valley, sand features associated with generally flat featureless narrow pockets floodplain occasional shallow and (falls, gravel sloped Gorge or sand pockets sections sections boulder, bedrock, alternating with lower and rapids) boulder bars) steep stepped (pools, riffles bars, benches and bedrock with gravel steps, bank attached ledges, islands, scour features on floodplain pools, riffles, bedrock Floodplain pockets Confined valley setting no floodplain and pools, gravel plunge benches boulder, bedrock, cascades, runs, bars riffles and waterfalls, Headwater

Namoi River Styles 24 River Style – Headwater

Sub-catchments All, uncommon in Lower Namoi

Character Single, steep, symmetrical to irregular channel occupying narrow v- shaped valleys. Low sinuosity imposed by bedrock valley. Channel is laterally and vertically stable. Bed composed of bedrock with boulder, cobble, gravel and/or sand deposits depending on local geology. Banks composed of bedrock and boulders. Floodplains are absent such that sediment storage is limited to small bars and benches.

Geomorphic Within channel: units • Cascades/waterfalls • Plunge pools • Small benches • Riffles and runs • Small mid-channel and bank attached bars

Controls First and second order streams in upper catchment positions. Common in Rugged metasediments, Rugged volcanics, Uplands and Pilliga landscape units, with a presence in the Liverpool plains. They occur in narrow (less than 20m at valley floor), v-shaped valleys with steep to very steep valley sides. Upstream catchment areas are small, generally less than 20km2, and gradients typically greater then 0.01m/m.

Behaviour High energy, laterally and vertically stable systems. Sand and silt materials are transported during low flows. As flow stage increases larger sediments are mobilised. Bars and benches are reworked during moderate to high flows. The steep gradients but relatively small catchment areas ensure that larger calibre sediments, such as boulders, are only moved in rare high magnitude events. Acts as a long-term source of sediments for downstream reaches. Geomorphic diversity is high, with boulders and LWD creating a range of flow and habitat conditions.

Variability Can occur on colluvium. These systems are characterised by narrow, within River steep, featureless valley floor and are susceptible to bed erosion through Style gullying processes (see Figure 5.2).

Representative Duncans Creek, Nundle 1:25000, GR 331300E 6518600 N reach

Namoi River Styles 26 Figure 5.1: Duncans Creek at Headwater representative reach during low flow. Note small bench on right and left side of the channel (upstream into page).

Figure 5.2: An example of a gentler gradient, colluvium Headwater - this variation is susceptible to erosion through gullying processes.

Namoi River Styles 27 Representative Reach - Headwater

Date of Analysis: 22/6/2004 Analysts: Guy Lampert and Amalia Short River: Duncans Creek Sub-catchment Peel Location: Nundle1:25000GR331300E6518600N Aerial Photo: Nundle 2002 R12/0249 Riparian vegetation Densely vegetated valley margins includes Eucalyptus spp., associations: Pinus radiata (Radiata Pine), Leptospermum spp. (Tea Tree) with an understorey of tree fern and Lomandra spp..

Landscape unit: Rugged metasediments Within catchment position: Upper Upstreamcatchment area: 5km2 Valley morphology: Narrow, V-shaped valley, up to 10m wide at valley floor Processzone: Sourceofmaterialsofvarioussizes. Channel slope: 0.08m/m Stream power estimate: Up to 700 W/m2. IndicativeCondition Good

20

18

16 Bedrock Valley

14

12 Low flow Bench channel

10

8 Arbitary Elevation (m)

6

4

2

0 100 90 80 70 60 50 40 30 20 10 0 Horizontal Distance (m) Figure 5.3 : Cross-section of Duncans Creek at Headwater representative reach (downstream into page).

Namoi River Styles 28 Key

Catchment boundary

Main channel

Tributary Bedrock valley

N

Figure 5.4: Planform map of Headwater River Style along Duncans Creek (Approximate scale 1:30000).

Figure 5.5: Aerial photo of a Headwater system, showing the network of first and second order streams (Approximate scale 1:25000)

Namoi River Styles 29 River Style – Gorge

Sub-catchments All, uncommon in Lower Namoi

Character Single, symmetrical channel in bedrock confined, irregular V or U shaped valley. Channel geometry and sinuosity is valley controlled. Bed composed of bedrock, boulder, cobble and gravel. System may also transport sand, depending on local geology. Banks are composed of bedrock and boulders and floodplains are absent.

Geomorphic Within channel: units • Alternating sequences of steep stepped sections and lower-sloped sections • Bedrock steps, waterfalls and cascades • Bedrock floored pools up to several 100 metres long • Boulder rapids up to 40 metres long • Bank attached bars in protected backwaters composed of sand and small gravels

Controls Located in upper, and occasionally middle, catchment positions of Rugged metasediments, Uplands and Rugged volcanics landscape units. Usually in slot shaped valleys less than 150m wide at valley floor. Upstream catchment areas are up to 2000km2 and gradients are generally greater than 0.01m/m.

Behaviour Extremely laterally and vertically stable due to bedrock confinement. At low flow, faster flowing rapids separate long, slow flowing pools. Sediments smaller than gravels are temporarily stored in protected backwaters. Higher flows transport small boulders, cobbles, gravels and sands. Larger boulders are only moved over short distances in very high magnitude events. The combination of bed diversity and instream boulder features creates a range of flow conditions. The presence of LWD within pools increases flow diversity during low flow. The relatively steep gradients and high degree of valley confinement generate high-energy flows which throughput sediment over short to moderate timeframes. Over the longer term acts as a source of sediment through the gradual expansion and down cutting of the valley floor. Sediment slugs may locally drown pools, if sediment supply is increased due to the erosion of upstream reaches. Excess sediment will be flushed during the next high flow event.

Variability May be terrace rather than bedrock confined eg. sections of Jacob and within River Joseph Creek and Wiles Gully in Mooki sub-catchment. Style Representative Namoi River, Welsh :25000, GR 300500E 6617500N reach

Namoi River Styles 30 Figure 5.6: Bedrock/boulder cascade on Namoi River at Gorge representative reach (right to left bank).

Figure 5.7: Wiles Gully, an example of a Gorge in moderate condition (downstream into page).

Namoi River Styles 31 Representative Reach - Gorge

Date of Analysis: 25/3/2004 Analysts: Guy Lampert and Amalia Short River: Namoi River Sub-catchment: Macdonald/Manilla Location: Welsh 1:25 000, GR 300500E 6617500N Aerial Photo: Manilla 2001 R2/0172 Riparian vegetation Instream trees including Leptospermum spp. (Tea Tree) and associations: Casuarina cunninghamii (River Oak). Adjacent valley slopes supports structurally intact native vegetation which includes Eucalyptus spp., Callitris spp. (Cypress Pine) and Tea Tree with an understorey of Lomandra spp. and native grasses.

Landscape unit: Rugged metasediments Within catchment Middle position: Upstream catchment 1925 km2 area: Valley morphology: Symmetrical to irregular, slot shaped valley up to 150 metres wide. Process zone: Throughput in balance over long term. Will accumulate sand sediments during low magnitude events, these are flushed by next high flow.

Channel slope: 0.011 m/m Stream power estimate: Up to 1500 W/m2. Indicative Condition Good

50

40

30

Arbitary Elevation (m) 20

Valley floor 10

0 0 50 100 150 200 250 300 350 400 450 Horizontal Distance (m) Figure 5.8: Cross-section of Namoi River at Gorge representative reach (downstream into page).

Namoi River Styles 32

Key

Valley margin

Cascade N

Ridge

Tributary

Bedrock valley

Figure 5.9: Planform map of Gorge River Style on the Namoi River (Approximate scale 1:30000)

Cascade

Flow direction

Figure 5.10: Aerial photo of Gorge representative reach along the Namoi River (Approximate scale 1:20000).

Namoi River Styles 33 River Style – Floodplain pockets

Sub-catchments All, uncommon in Lower Namoi

Character Single, bedrock or terrace confined, channel with low sinuosity. Small floodplains occur at isolated wider sections of the valley, either behind bedrock spurs or at tributary confluences. Channel geometry is symmetrical to asymmetrical where floodplain pockets occur. Channel bed is dominantly composed of bedrock with forced pools and runs separated by short, steep riffles of bedrock steps. Bed loads are usually dominated by gravel or sand dependent on local geology. Banks are bedrock or terrace, except where floodplains occur. The narrow floodplains are composite with basal gravels overlain by finer grained sediments (sand/silt). Flood channels traverse floodplain surfaces, usually along opposite valley margin to the channel.

Geomorphic units Within channel • Pools, usually bedrock floored, separated by coarse gravel and cobble riffles and bedrock steps • Glides and runs • Mid-channel and bank attached bars dissected by chute channels • Small vegetated islands • Benches and ledges with chute channels Floodplains • Occasional small floodplain pockets at points of local valley widening • Flood channels • Stripped or scour features

Controls Usually associated with the Rugged metasediments, Rugged volcanics and Uplands landscape units, with presence in Liverpool plains, Middle to lower Peel and Pilliga. Located in relatively narrow, less then 250m wide, v- shaped valleys in middle to upper catchment positions. Upstream catchment areas are up to 2000km2 and gradients lie between 0.002 and 0.02 m/m.

Behaviour Generally stable river morphology with little potential for lateral adjustment due to bedrock or terrace control. The channel bed may aggrade or degrade, depending on sediment availability and the potential for sediment throughput. During low flows a pool-run-step sequence is maintained, providing high geomorphic and hydraulic diversity. Higher flows transport bed load, rework bars and activate chute channels that dissect bars and benches. Over bank flows build the floodplain through vertical accretion. Coarse materials are deposited under high-energy flow conditions and fines are deposited from suspension in the waning stage of the flood. Floodplains and benches are prone to reworking via stripping processes during high magnitude flow events. The combination of relatively steep gradients, confinement and relatively large catchment areas leads to high-energy systems which throughput sediment over the long term. Hydraulic diversity is generally high, with flow diversity generated by the combination of bed forms, instream boulders, bedrock outcrops, vegetation and LWD.

Variability within Bedload may be gravel or sands, depending on catchment geology. River Style Valley margins may be bedrock or terrace. Representative Swamp Oak Creek, Weabonga 1:25000, GR 338900E 6546600N reach

Namoi River Styles 34 Valley Margin

Floodplain

Riffle Bench Bar

Pool

Figure 5.11: Swamp Oak Creek at Floodplain pockets representative reach showing a diversity on in-channel geomorphic units including pool, riffle, bars and benches (upstream into page).

Floodplain pocket

Figure 5.12: Jamiesons Creek, section of a Floodplain pockets reach showing channel, floodplain pocket and valley (upstream into page).

Namoi River Styles 35 Representative Reach – Floodplain pockets

Date of Analysis: 22/6/2004 Analysts: Guy Lampert and Amalia Short River: Swamp Oak Creek Sub-catchment: Peel Location: Weabonga 1:25000 GR 338900E 6546600N Aerial Photo: Nundle 2002 R6/0198 Riparian vegetation Casuarina cunninghamii (River Oak) in channel, on banks and associations: floodplain pockets, with an understorey of pasture grasses on banks, benches and floodplain pockets.

Landscape unit: Rugged metasediments Within catchment Middle to upper position: Upstream catchment 80 km2 area: Valley morphology: Irregular valley up to 100m wide Process zone: Throughput, with temporal storage of sediments in floodplain pockets. Source of gravels over the long term, through breakdown of bedrock. Channel slope: 0.007 m/m Stream power estimate: Up to 1500 W/m2 at bankfull. Indicative Condition Good

20

18

16

14

Floodplain 12 Bench Low flow channel 10 Bar Chute channel 8 Arbitarty Elevation (m)

6

4

2

0 0 5 10 15 20 25 30 35 40 45 50 Horizontal Distance (m) Figure 5.13: Cross-section of Swamp Oak Creek at Floodplain pockets representative reach.

Namoi River Styles 36 Key

Channel margin

Tributary Valley margin Bedrock valley

Floodplain

N

Figure 5.14: Planform map of Floodplain pockets River Style (Approximate scale 1:14000).

Floodplain pocket

Flow Floodplain pocket direction Figure 5.15: Aerial photo of Swamp Oak Creek the Floodplain Pockets representative reach (Approximate scale 1:14000).

Namoi River Styles 37 River Style – Confined valley, sand

Sub-catchments Lower Namoi and Middle Namoi Character Single, low sinuosity, laterally stable sand bed system. Channel is symmetrical with variable width/depth ratio. Channel alignment and geometry is valley controlled. Occasional small floodplain pockets are observed along some reaches, in areas of locally wider valleys. The flat, featureless bed, which resembles a valley fill, is dominated by sand with some fines and organic materials. The bed is usually highly mobile but in undisturbed situations the surface is stabilised by a dense growth of grasses. Valley margins form the banks, except on the rare occasions where floodplain pockets occur.

Geomorphic Within channel: units • Lumpy, featureless sand dominated bed • Poorly defined low flow channel may be present • Small scour features in bed associated with valley margins, large trees or LWD Floodplain: • Generally absent, occasional small floodplain pockets may be present in areas of local valley widening • Scour features on floodplain

Controls Occurs in middle to upper catchment positions of the Pilliga landscape unit, with a small presence in the Liverpool plains. Generally in low sinuosity, regular valleys between 5m and 50m wide at valley floor. Upstream catchment areas are up to 200 km2 and on gradients of 0.01 m/m and steeper.

Behaviour These intermittent systems do not typically retain surface water between flow events. With similarities to valley fills and gorges the whole valley floor acts as the channel during flow events. In nearly all cases, even the largest flow events are contained within the channel. Moderate to high flows transport both sand and suspended sediments that are deposited as a blanket on the bed via vertical accretion processes as flows wane. Benches and small floodplains pockets are formed through lateral accretion processes as a result of flow separation on bends. The stability of the bed is directly related to vegetation. If vegetation is disturbed, fines and organic materials are preferentially transported downstream, leaving a coarse mobile sand bed. Once disturbed the massive release of sediment will cause sediment slugs and the aggradation of downstream reaches. After disturbance the highly mobile bed and the lack of fines and organic matter may inhibit future revegetation. Relatively steep gradients and confinement can generate moderate to high stream powers. Hydraulic diversity is low due to homogeneous bed, however instream vegetation and LWD (if present) do create some scour features within the bed. Sediment transfer is generally in balance, unless bed vegetation has been disturbed and sand bed mobilised.

Variability Channel bed may be well vegetated and stable, dominated by sands with within River fines and organic matter (eg Borah Creek in Figure 5.16) or an extremely Style mobile sand sheet (eg Rocky Creek in Figure 5.17)

Representative Borah Creek, Mullaley 1:50000, GR 744400E 6554700N reach

Namoi River Styles 38 Figure 5.16: Borah Creek at Confined valley, sand representative site, the bed is stabilised by adense layer of grasses (downstream into page).

Figure 5.17: Rocky Creek, Confined valley, sand in poor condition. Sand bed is highly mobile and is transporting excess sand due to upstream disturbance (downstream into page).

Namoi River Styles 39 Representative Reach – Confined valley, sand

Date of Analysis: 30/6/2004 Analysts: Guy Lampert and Amalia Short River: Borah Creek Sub-catchment: Lower Namoi Location: Mullaley 1:50000, GR 744400E 6554700N Aerial Photo: Tambar Springs 2003 R3/0221 Riparian vegetation Mature and juvenile Eucalyptus camaldulensis (River Red associations: Gum), scattered Callitris spp. (Cypress Pine) and Acacia spp. (Wattle) with understorey of native and pasture grasses occur in channel and on valley margins.

Landscape unit: Pilliga Within catchment Upper position: Upstream catchment 35 km2 area: Valley morphology: Regular low sinuosity valley, 30m wide at valley floor Process zone: Transfer Channel slope: 0.011 m/m Stream power estimate: Up to 250 W/m2. Indicative Condition Good

6

5 Valley margin Valley margin

4

3 Arbitary elevation (m) Valley floor 2

1

0 0 20 40 60 80 100 120 140 160 Horizontal distance (m) Figure 5.18 : Cross-section of Borah Creek at Confined valley, sand representative reach (downstream into page).

Namoi River Styles 40 Key N Valley margin

Tributary

Bedrock valley

Figure 5.19: Planform map of the Confined valley, sand River Style (Approximate scale 1:20000).

Figure 5.20:Aerial photo of Borah Creek Confined valley, sand representative reach (Approximate scale 1:30000)

Namoi River Styles 41 River Style – Bedrock controlled, gravel

Sub- All, uncommon in Lower Namoi catchments Character Single, symmetrical to asymmetrical compound channel within a partly confined valley. Changes in valley width and alignment largely dictate channel sinuosity and the longitudinal extent of floodplains. Discontinuous floodplains are formed on inside bends as channel switches from valley margin to valley margin. Bedrock floored channel with gravel bed load. Banks are either bedrock or gravel overlain with fines.

Geomorphic Within channel: units • Pools, generally forced, separated by steep riffles • Bars (point, bank attached, mid-channel) dissected by chute channels • Benches (point and lateral) • Occasional vegetated islands • Bedrock sills/steps Floodplains: • Discontinuous floodplains traversed by flood channels • Levees on inside bends • Terraces • Backswamps in protected, distal areas of the floodplain

Controls Common in middle to upper catchment positions of the Rugged metasediments, Liverpool plains and Middle to lower Peel landscape units, with a presence in Rugged volcanics, Pilliga and Uplands. Flow through irregular sinuous or spurred valleys, up to 2km wide at valley floor. Gradients are between 0.002 and 0.01 m/m and catchment areas are up to 5900km2.

Behaviour During low flows, slow flowing pools are separated by faster flowing riffles. Higher flows rework bars, scour pools and transport gravel bed load. If disturbed, alluvial banks are susceptible to erosion during moderate to high flows. Overbank flows generally occur every 2-5 years unless the channel has enlarged. Floodplains are generally formed behind bedrock spurs through the vertical accretion of fine-grained suspended sediments during the waning stage of floods. Gravel splays may be deposited on the floodplain by a sudden surge in flood height. Floodplains are prone to stripping in higher energy situations, especially if vegetation has been removed. Although high stream powers can be generated the channel is relatively stable with little capacity for lateral adjustment. Concave banks are often pinned against the valley margin, limiting downstream migration of bends, and floodplains usually form where they are protected by bedrock spurs. Channel may change course through avulsion in locally wider sections of valley. Hydraulic diversity is generally high with different flow environments created by a variety of bed forms, moderate LWD loading, instream vegetation and bedrock outcrops. Sediment transfer is in balance over the long term.

Variability Variations in valley width over short distances may create more confined within River gorge-like reaches or less confined more laterally active reaches. Valley Style margins are usually bedrock but may be terrace (eg Yarramabully Creek Figure 5.22).

Representative Dungowan Creek, Niangala 1:25000, GR 341100E 6528500N reach

Namoi River Styles 42 Figure 5.21: Dungowan Creek at Bedrock controlled, gravel representative site, note gravel bar and alluvial bank on left and valley margin on right (upstream into page).

Floodplain

Approximately 5 metres Terrace

Figure 5.22: Yarramabully Creek, an example of terrace confined Bedrock controlled, gravel in poor condition. Note flat featureless gravel bed (downstream into page).

Namoi River Styles 43 Representative Reach – Bedrock controlled, gravel

Date of Analysis: 24/6/2004 Analysts: Guy Lampert and Amalia Short River: Dungowan Creek Sub-catchment: Peel Location: Niangala 1:25000, GR 341100E 6528500N Aerial Photo: Nundle 2002 R10/0150 Riparian vegetation Toe of bank protected by sedges and pin rush. Bars and banks associations: support Casuarina cunninghamii (River Oak). Continuous riparian corridor includes River Oak, Eucalyptus spp., Acacia spp. and Leptospermum spp. (Tea Tree) with an understorey of Lomandra spp. and pasture grasses. Floodplains are pasture grasses with only scattered trees.

Landscape unit: Rugged metasediments Within catchment Upper position: Upstream catchment 175 km2 area: Valley morphology: Irregular spurred or sinuous valley, 50-100 metres wide. Process zone: Throughput in balance over the long term Channel slope: 0.0095 m/m Stream power estimate: Up to 700 W/m2 at bankfull Indicative Condition Good

6

Terrace

5 Floodplain

4 Low flow channel Bench

3

Bar Arbitary elevation (m) 2

1

0 100 90 80 70 60 50 40 30 20 10 0 Horizontal distance (m) Figure 5.23: Cross-section of Dungowan Creek at Bedrock controlled, gravel representative reach (downstream into page).

Namoi River Styles 44 Key N Channel margin Bar

Floodchannel Bedrock valley

Tributary Floodplain Valley margin

Figure 5.24: Planform map for Bedrock controlled, gravel River Style along Dungowan Creek (Approximate scale 1:14000).

Flow direction

Figure 5.25: Aerial photo of a section of Dungowan Creek Bedrock controlled, gravel representative reach (Approximate scale 1:9000).

Namoi River Styles 45 River Style – Bedrock controlled, sand

Sub- Macdonald/Manilla and Lower Namoi, with a presence in Peel catchments Character Single, low-moderate sinuosity, laterally stable channel within a partly confined valley. Changes in valley width and alignment largely dictate channel sinuosity and the longitudinal extent of floodplains. Discontinuous floodplains are formed as the channel crosses from valley margin to valley margin. Channel is generally compound with low-moderate width/depth ratio. Bed is composed of sands with occasional gravel deposits in higher energy locations. Banks are composed of bedrock or vertically accreted fines.

Geomorphic Within channel: units • Long pools, often bedrock forced, separated by gravel riffles and bedrock steps • Sand and gravel bars (bank attached and point) • Vegetated islands • Benches with chute channels Floodplains: • Discontinuous floodplains traversed by flood channels • Levees on inside bends • Sand splays • Backswamps in protected, distal areas of the floodplains

Controls Predominantly occur in middle to upper catchment positions of the Pilliga and Uplands landscape units, with a small presence in Rugged metasediments. Located in sinuous, spurred valleys, up to 1km wide at valley floor. Gradients typically range from 0.002 to 0.02 m/m and catchment areas are up to1350km2.

Behaviour During low flows, fast flowing riffles/bedrock steps separate long slow flowing pools. Moderate flow events mobilise the sand bed, rework bars and scour pools. Flood events activate chute channels and form benches and levees. During floods the sand bed load is transported in suspension and sand splays are deposited on the floodplains by surges in flood height. Although moderate to high stream powers can be generated, the channel is relatively stable with little capacity for lateral adjustment. Concave banks are often pinned against the valley margin, limiting downstream migration of bends, and the floodplains usually form where they are protected by bedrock spurs. Channel may change course through avulsion in locally wider sections of valley. Channel is also prone to enlargement through the erosion of benches and floodplains, especially when riparian vegetation is disturbed. Hydraulic diversity is high, with a range of flow conditions created by a diversity of bed materials, bed forms, bedrock outcrops and LWD. Sediments are generally throughput over the long term with temporal storage in floodplain deposits. Sediments may accumulate if upstream reaches are disturbed, resulting in a less diverse bed character.

Variability Variations in valley width over short distances may create more confined within River gorge-like reaches or less confined more laterally active reaches. Style Representative Macdonald River, Walcha Road 1:25000, GR 336500E 6578900 N reach

Namoi River Styles 46