Application of the River Styles framework as a basis for river management in New South Wales, Australia

Transcription

1 Applied Geography 22 (2002) Application of the River Styles framework as a basis for river management in New South Wales, Australia G. Brierley a,, K. Fryirs a, D. Outhet b, C. Massey c a Department of Physical Geography, Macquarie University, North Ryde, NSW 2109, Australia b New South Wales Department of Land and Water Conservation, PO Box 3720, Parramatta, NSW 2124, Australia c New South Wales Department of Land and Water Conservation, PO Box 118, Bega, NSW 2550, Australia Received 1 February 2001; received in revised form 15 June 2001; accepted 3 July 2001 Abstract If strategies in natural resource management are to work with nature, reliable biophysical baseline data on ecosystem structure and function are required. The River Styles framework provides a geomorphic template upon which spatial and temporal linkages of biophysical processes are assessed within a catchment context. River Styles record river character and behaviour. As the capacity for a river reach to adjust varies for each style, so too do management issues and associated rehabilitation programmes. The framework also provides a basis for assessing geomorphic river condition and recovery potential, framed in terms of the evolutionary pathways of differing River Styles in the period since the European settlement of Australia. Within a catchment context, the River Styles framework provides a unified baseline upon which an array of additional information can be applied, thereby providing a consistent framework for management decision-making. The framework was developed as a research tool by geomorphologists working in collaboration with the New South Wales Department of Land and Water Conservation, which has used it for a range of river management applications. Target conditions for rehabilitation programmes are framed within a catchment vision that integrates understanding of the character, behaviour, condition and recovery potential of each reach. A prioritization procedure determines the most cost-effective and efficient strategies that should be implemented to work towards the catchment vision. In addition, the River Styles framework is being used to identify rare or unusual geomorphic features that should be pre- Corresponding author. Tel.: ; fax: address: gbrierli@laurel.ocs.mq.edu.au (G. Brierley) /02/$ - see front matter 2002 Published by Elsevier Science Ltd. PII: S (01)

2 92 G. Brierley et al. / Applied Geography 22 (2002) served, assess riparian vegetation patterns and habitat availability along river courses, and derive water licensing, environmental flow and water quality policies that are relevant to river needs in each valley. Based on these principles, representative biomonitoring, benchmarking and auditing procedures are being developed to evaluate river health Published by Elsevier Science Ltd. Keywords: Australia; Fluvial geomorphology; River management; River rehabilitation; River styles Introduction The theory and practice of environmental management in Australia have been subjected to major changes in the past decade or so, with increasing emphasis on stakeholder and community initiatives in natural resources management (Conacher & Conacher, 2000). Many researchers now work directly with managers to bring about changes in environmental practice. Geographers are ideally placed to work at the interface between scientific understanding of biophysical processes and direct management applications, through the provision of tools and techniques for catchment planning and on-the-ground applications in conservation and rehabilitation programmes (Brookes & Shields, 1996; Downs & Thorne, 1996; Rutherfurd, Jerie, Walker, & Marsh, 2000). In this study, collaboration between researchers at Macquarie University and the New South Wales Department of Land and Water Conservation (NSW DLWC) is documented, showing how this collaboration has changed the focus of river management practices in New South Wales, particularly in the Bega catchment, on the south coast. Over the last decade or so principles from fluvial geomorphology have been embraced as a core component of river management practices in Australia and overseas (e.g. Newson, 1992; Sear, 1994; Downs, 1995a; Kondolf, 1995a; Sear, Newson & Brookes, 1995; Newson, Clark, Sear, & Brookes, 1998; Brierley, 1999; Rutherfurd, Jerie, Walker, & Marsh, 1999). Geomorphology provides an ideal starting point for evaluating the interaction of biophysical processes within a catchment, as geomorphological processes determine the structure, or physical template, of a river system. Understanding of geomorphic processes, and determination of appropriate river structure and function at differing positions in catchments, are critical components in sustainable rehabilitation of aquatic ecosystems (Southwood, 1977; Poff & Ward, 1990; Newson, 1992; Brookes, 1995; Imhof, Fitzgibbon, & Annable, 1996; Maddock, 1999). The geomorphic structure and function of many rivers are tied innately to vegetation cover and composition, and the loading of large woody debris (e.g. Hickin, 1984; Brooks, 1999a; Millar, 2000). These interactions induce direct controls on the distribution of flow energy, dictating local-scale patterns of erosion and deposition at differing flow stages. When tied to sediment availability and flow variability, geomorphic structure dictates the diversity of hydraulic units and associated habitats along river courses, and many other facets of aquatic ecosystem functioning (e.g. nutrient flow, transfer of organic materials, etc.; see Taylor, Thomson, Fryirs, & Brierley, 2000). Based on these considerations, river morphology and

3 G. Brierley et al. / Applied Geography 22 (2002) vegetation associations must be appropriately reconstructed before sympathetic rehabilitation of riverine ecology will occur. Two examples of differing patterns of interactions of biophysical processes related to the geomorphic structure of rivers are presented in Fig. 1. Most Australian rivers are now part of highly modified landscapes in which human activities are dominant. Efforts at river rehabilitation cannot realistically aim to reconstruct landscapes of the period prior to European settlement. The catchment conditions under which many rivers now operate (in terms of water and sediment transfer and vegetation coverage) have been fundamentally altered, in many cases irreversibly. As many river systems are now adjusting to a new set of boundary conditions (Cairns, 1989), management programmes must strive to adopt river rehabilitation strategies that work with the contemporary catchment conditions. As rivers demonstrate remarkably different characters, behaviours and evolutionary traits (both between and within catchments), individual catchments need to be managed in a flexible manner, recognizing what forms and processes occur where, why and how often, and how these processes have changed over time. To achieve this, a physical template is required upon which to assimilate and order information, identify gaps and, most importantly, highlight linkages of biophysical processes and their management implications. Without this template, management programmes are applied in an ad hoc manner. It is not unduly cynical to ask how management strategies can work within a sustainable framework if the principles adopted do not work with nature, building on a catchment-framed understanding of river character and behaviour. Unfortunately, at the beginning of the 21st century there remains a serious lack of baseline information on the character, behaviour and distribution of different river types across the Australian continent. The River Styles framework provides a geomorphic tool for catchment-wide assessment of river character, behaviour, evolution and condition (Brierley & Fryirs, 2000; Fryirs & Brierley, 2001). The framework was developed by Gary Brierley, Kirstie Fryirs and colleagues in the Department of Physical Geography at Macquarie University, working in direct collaboration with river managers and applied geomorphologists in the NSW DLWC, with support from Land and Water Australia (LWA). To date, the framework has been applied to 14 New South Wales coastal catchments. NSW DLWC staff are now applying it across many other catchments in the state to meet the requests of stakeholder committees and boards. A statewide GIS database will be established so that the information can be readily accessed by anyone interested in river management activities. A River Style is a river reach with a near-uniform assemblage of geomorphic units (Brierley & Fryirs, 2000). Stage 1 of the River Styles framework entails the identification, interpretation and mapping of River Styles throughout a catchment (Brierley & Fryirs, 2000) to provide a baseline survey of river character and behaviour. The second stage assesses the geomorphic condition of each reach of each style in the catchment, framed in terms of an analysis of river evolution. By placing each reach in its catchment context, its geomorphic recovery potential is determined in stage 3 (see Fryirs & Brierley, 2000). From this, predictions of likely future river condition are determined. With this information in hand, realistic target conditions

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5 G. Brierley et al. / Applied Geography 22 (2002) Fig. 1. Geomorphology as a physical template. Note: Principles from fluvial geomorphology can be applied to derive a template with which to explain the interaction of various biophysical processes along river courses, including vegetation type, hydraulic diversity and habitat availability. In Example A, the geomorphic structure of an intact valley fill comprises a relatively flat and featureless swamp, with a discontinuous channel and localized ponding. The moisture gradient across the swamp results in different vegetation associations, with Melaleuca sp. at the margins and Juncus sp. in the centre (Inset B). All flood events inundate the swamp surface and filter through the organic-rich sediments, thereby maintaining base flows to downstream reaches. One of the most frequently occurring river types in coastal catchments of New South Wales comprises pockets of floodplain within partly confined valleys (Example B). An array of geomorphic units is evident, including primary, backwater and chute channels, a dissected bar platform, and floodplain pockets (Inset A). As noted in Inset B, differing geomorphic surfaces have distinct substrates, inundation frequencies and associated magnitude frequency relationships. This results in the prominence of primary colonising species on bar surfaces, open forest associations on the floodplain, and swamp associations in valley marginal back channels. for river rehabilitation programmes are identified for each reach in stage 4, framed within a catchment-based vision. Working with local/regional catchment managers, a physically based procedure to prioritize management strategies for river rehabilitation and conservation is then applied. The identification and characterization of a River Style is not simply a visual assessment of a river, but a summary understanding of how that river operates or behaves within its valley setting. The geomorphic unit framework (Brierley, 1996) provides the fundamental interpretative tool that sets the River Styles framework apart from other classification schemes. These building blocks of rivers record the form-process associations occurring along a reach. The River Styles framework endeavours to move beyond visual and mechanical approaches to river classification to provide a more process-based procedure for analysing river character and behaviour (cf. Mosley, 1987; Church, 1992; Rosgen, 1994, 1996; Montgomery & Buffington, 1997; Raven, Fox, Everand, Holmes, & Dawson, 1997; Newson et al., 1998; Rowntree & Wadeson, 1999). Prescriptive and regionally specific river classification procedures provide little sense of river process, river change, river condition or trajectory (Kondolf, 1995a; Kondolf & Downs, 1996; Miller & Ritter, 1996). Unlike these schemes, the River Styles framework is: Open-ended and generic. New variants can be added as the framework is applied in new environmental settings. It is not a rigid scheme that pigeonholes rivers into categories. Process-based. Understanding of the character and behaviour of both channel and floodplain zones provides the process-based knowledge to manage rivers in a way that works with nature. Catchment-based. Linkages of biophysical processes in catchments, such as water and sediment fluxes and vegetation dispersal, can be analysed. Structured hierarchically. Processes occurring at finer scales can be explained by those occurring at higher levels in the hierarchy (see Brierley & Fryirs, 2000, and references therein). Set within the context of river evolution. Understanding a river s capacity to adjust

6 96 G. Brierley et al. / Applied Geography 22 (2002) Fig. 2. Procedures used to identify River Styles. Note: The degree of valley confinement along a reach is the first step in the identification of River Styles. Three classes are differentiated: confined, partly confined and alluvial valley settings. Different procedures are used to identify River Styles for each of these classes. In confined valley settings, the abundance of floodplain pockets forms the first level of analysis, followed by bed material texture and the make-up of geomorphic units on the valley floor (cf. Grant, Swanson, & Wolman, 1990; Montgomery & Buffington, 1997). In partly confined valley settings, the extent and role of bedrock control on the distribution of floodplain pockets is the key determinant in the differentiation of bedrock- and planform-controlled River Styles. Bed material texture and geomorphic units determine finer levels of analysis. Differentiation of alluvial River Styles is based initially on the presence and continuity of the channel. For absent or discontinuous channels the valley floor texture and array of geomorphic units are key considerations. For alluvial rivers with continuous channels, conventional planform-based notions are followed in the identification of River Styles (cf. Rust, 1978), with additional layers reflecting bed material texture (cf. Schumm, 1977) and the assemblage of geomorphic units along the reach (cf. Brierley, 1996). within its valley setting provides the basis for assessing how far from its natural condition the river sits, and why that type of river has changed. Only then can the contemporary condition of a river be realistically assessed. Directly linked to assessment of the trajectory of future river condition (recovery potential). Analysis of river change provides a basis to predict how a river will adjust in the future. This provides a geomorphic basis for determining future target conditions for river rehabilitation and creating a catchment-framed vision. In the River Styles framework, differentiation of river character and behaviour is initially based on the valley setting of a river, using procedures outlined in Fig. 2. Using this procedure, 21 River Styles have been identified in coastal valleys of New South Wales. The critical geomorphic units that comprise each style are indicated

7 G. Brierley et al. / Applied Geography 22 (2002) Fig. 3. Procedures used to name River Styles in coastal catchments of New South Wales. Note: Following procedures outlined in Fig. 2, 21 River Styles have been identified in coastal valleys of New South Wales (noted in italics). Three are in confined valley settings, three in partly confined valley settings, four in alluvial (discontinuous channel) valley settings, and eleven in alluvial (continuous channel) valley settings. Differentiation of River Styles is based, in part, on the scale of analysis of reaches. In this instance, identification has been made for reaches of several kilometres length.

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9 G. Brierley et al. / Applied Geography 22 (2002) Fig. 4. Schematic planform views of River Styles in coastal catchments of New South Wales. Note: Each River Style has a characteristic planform and geomorphic unit assemblage. River Styles in confined valley settings have no floodplain or occasional floodplain pockets. The shape of the valley (sinuous, irregular or straight) dictates the position of discontinuous floodplain pockets and the alignment of the channel within the partly confined valley setting. Discontinuous alluvial channels have a number of forms, ranging from ponds through discontinuous channels to featureless swamps. Alluvial valley settings with continuous channels are characterized by continuous floodplains along both channel margins. These rivers display an array of forms largely dependent on channel slope and the texture of the channel banks and bed. Geomorphic unit assemblages range markedly from style to style. As the River Styles framework is open-ended, new variants or river can be identified, such as the multi-channel sand belt. on Fig. 3, and schematic planform representations are presented in Fig. 4. Given the open-ended nature of the procedure, the range of River Styles is not prescriptive and can be added to as new variants arise. For example, although no braided rivers are evident in coastal valleys of New South Wales, sand or gravel braided rivers could easily be added to the procedural trees shown in Figs 2 and 3. The explanatory and predictive bases of the River Styles framework provide a rigorous physical basis for management decision-making. The key management applications and implications outlined in this manuscript are as follows. 1. The River Styles framework is used to determine management programmes that work with nature. 2. Rare or unique River Styles are identified, such that appropriate conservation measures can be developed and applied. 3. Linkages of biophysical processes within a catchment are integrated into river management plans. 4. Geomorphic condition and river recovery potential are assessed. 5. A catchment-based physical vision is derived. 6. Realistic target conditions are identified for each reach in the catchment. 7. A catchment-based prioritization framework for river management programmes is developed. 8. Representative reaches are selected for various biomonitoring programmes used to audit the impacts of environmental flows, water licensing and water quality. This paper demonstrates the application of the River Styles framework in several on-going management programmes carried out by NSW DLWC. Particular emphasis is placed on Bega catchment, on the south coast of New South Wales, where detailed geomorphic research has been undertaken (Brooks & Brierley, 1997, 2000; Brierley & Fryirs, 1998, 1999; Fryirs & Brierley, 1998, 1999, 2001; Brierley, Cohen, Fryirs, & Brooks, 1999a).

10 100 G. Brierley et al. / Applied Geography 22 (2002) Applications of the River Styles framework Using River Styles to develop management programmes that work with nature All too often rivers have been managed to some norm, with undue emphasis placed on their stability. In the River Styles framework, management programmes are derived to work with the contemporary character and behaviour of rivers, recognizing the diversity of patterns and rates of adjustment. Interpretation of form-process associations for the assemblage of geomorphic units that make up a River Style Table 1 The capacity for adjustment of various examples of River Styles and typical associated management response River Style Capacity for adjustment Management response Confined valley setting Gorge Minimal Bed material organization can locally adjust Preserve and protect Partly confined valley setting Bedrock- controlled Local channel expansion Woody debris placement discontinuous Floodplain stripping Fencing and revegetation floodplain Ensure compatible land use Alluvial valley setting - discontinuous channel Floodout Shifting loads of sediment Ensure compatible land use on the accumulation as feeder active shallow-angle fan channel(s) shift Proactive nickpoint control Chain-of-ponds Pond expansion and deepening Fencing and revegetation Ensure compatible land use Proactive nickpoint control Alluvial valley setting - continuous channel Meandering fine Bed incision Bed control grained Channel expansion Fencing and revegetation Channel abandonment Ensure compatible land use Meandering gravel Channel migration Bed control bed Bed incision Bank protection Channel expansion Woody debris placement Floodplain stripping Fencing and revegetation Ensure compatible land use

11 G. Brierley et al. / Applied Geography 22 (2002) provides insight into the capacity for river adjustment in a reach. Different management problems tend to arise in differing types of river. As a consequence, different river rehabilitation techniques must be applied, as effective management responses aim to fix underlying causes rather than the symptoms of change. Examples of differing patterns of river adjustment, and typical management responses as applied by NSW DLWC, are summarized in Table 1. Certain types and rates of geomorphic change fall within the natural range of behaviour for any River Style. The degree of inherent stability varies naturally from style to style, from reach to reach, and from subcatchment to subcatchment. Accordingly, some stream systems are more sensitive to physical and biological disturbance than others. Hence, identification of River Styles guides what types of problems are to be expected where, and what natural patterns and rates of adjustment are expected for different types of streams. The key is to determine the capacity for adjustment for each style by interpreting the potential ways in which a river can adjust within its valley setting (cf. Downs, 1995b). For example, the natural proportion of eroding banks varies markedly from one River Style to another. In a chain-of-ponds style, bank erosion is unexpected, but in an alluvial meandering style, natural patterns of bend migration may result in active erosion along up to 50% of banks. In some settings, channel avulsion is a natural component of the river s long-term behavioural regime. For example, wandering gravel-bed rivers naturally switch channels at differing flow stages. Therefore, trying to maintain stability (no change) is not a sustainable basis for rehabilitating such streams. It is now recognized that reducing rates of change that have been accelerated by disturbance in the period since European settlement is the only practical solution to river rehabilitation in many instances. Most reaches that are sensitive to adjustment are found in alluvial valley settings, where the river has the capacity to adjust its form. The removal of riparian vegetation and large woody debris along many alluvial reaches of rivers in coastal New South Wales in the period since European settlement has brought about profound changes to river morphology (Abernethy & Rutherfurd, 1998; Brooks, 1999b). Positive feedback mechanisms induced by increased channel capacity have increased sediment transport capacity and stream power conditions to such a degree that changes to river character and behaviour are to all intents and purposes irreversible. However, over 70% of river courses mapped in New South Wales coastal catchments comprise confined or partly confined valley settings (Brierley et al., 1999b). In the latter settings, processes such as catastrophic stripping are promoted as high stream powers are generated and flow energy is concentrated across the valley floor (cf. Nanson, 1986). While the capacity for these streams to strip their floodplains under a fully vegetated cover is conjectural, contemporary river management programmes must recognize the potential for profound adjustments to river morphology in these reaches. It is only in the light of understanding of the natural range of character and behaviour of differing river reaches, framed in terms of a river s capacity for adjustment, that management strategies can be devised that work with nature.

12 102 G. Brierley et al. / Applied Geography 22 (2002) Conservation of unique or rare River Styles Identification of unique or rare reaches of a River Style provides a basis upon which to conserve these rivers to maintain the geodiversity of fluvial landscapes (cf. Boon, 1992; Naiman, Lonzarich, Beechie & Ralph, 1992; Newson, 1992; Downs & Gregory, 1994; Penn, 1999; Rutherfurd et al., 1999, 2000). This has implications for conservation programmes at local, catchment, regional or even state/national levels (Koehn, Brierley, Cant, & Lucas, 2001). River Styles assessments undertaken in coastal New South Wales have identified river variants not previously described in the geomorphology literature. For example, in the Richmond catchment, discontinuous sand-bed and multi-channel sand-belt River Styles were identified in the sandstone landscape in the south of the catchment (Goldrick, Brierley, & Fryirs, 1999). As another example, the wandering gravel-bed and low sinuosity boulder-bed River Styles are only found (so far) in isolated sections of the Bellinger, Hastings, Macleay and Tweed catchments on the north coast. Similarly, the distribution of intact valleyfill and chain-of-ponds styles has highlighted the limited range over which these once prevalent river types extend. These two styles maintain base flow and filtering processes throughout catchments, providing unique habitats for aquatic fauna (see Fig. 1a). Identification of these rare or unique reaches has only been achieved through catchment-wide baseline surveys of river character and behaviour. Sadly, such baseline data are still missing across much of the Australian continent. Implications of catchment-framed biophysical linkages in river management plans In proactive river rehabilitation programmes, upstream-downstream and tributarytrunk stream linkages of biophysical processes are a fundamental component in the design of reach-based plans (cf. Downs & Brookes, 1994; Brookes, 1995; Kondolf & Downs, 1996; Brookes & Sear, 1996; Sear, 1996; Fryirs & Brierley, 2001). Issues such as sediment movement, water transfer and seed dispersion are critical factors in determining what can realistically be achieved in each reach. In the River Styles framework, assessment of upstream-downstream linkages places each reach within its catchment context, enabling off-site impacts to be interpreted. For example, if a nickpoint is excavating a valley fill, the potential exists for extensive sediment removal. Impacts will vary, depending on the downstream River Style. While sediments may be flushed through confined or partly confined valley settings, with impacts restricted to local bed aggradation and transitory infilling of pools, there may be much more profound impacts if the sediment slug reaches an alluvial River Style, where the capacity for river adjustment may be significant (e.g. lateral channel expansion, sedimentation on floodplains, increased homogeneity of the channel bed, etc.). Alternatively, if upstream sediment availability is limited, the potential for geomorphic river recovery in over-enlarged channels downstream is limited (cf. Kemp, Harper & Crossa, 1999; Fryirs & Brierley, 2001). In the River Styles framework these issues are addressed by analysing the downstream pattern of River Styles. The example presented in Fig. 5 shows how downstream patterns of flow and sediment transfer vary along river courses in two adjacent subcatchments in Bega catchment.

13 G. Brierley et al. / Applied Geography 22 (2002) Fig. 5. River Styles in Wolumla catchment, South Coast, New South Wales. Note: Six River Styles have been identified in Wolumla catchment, which drains an area of around 130 km 2 of granitic terrain in the southern part of Bega catchment on the New South Wales south coast (Brierley & Fryirs, 2000). Along Wolumla Creek four River Styles occur. In the headwaters, which drain from the escarpment zone, the Gorge River Style (A) is characterized by bedrock steps and waterfalls, separated by rapids and bedrockinduced pools. Gradients are steep and no floodplain occurs along the valley margin. Immediately downstream of the escarpment, the valley widens and an alluvial channelized fill River Style (B) develops. This is characterized by continuous valley flats along both sides of an incised trench. The floor of the trench comprises a series of inset features, sand bars, sand sheets and swampy low-flow channels. Prior to European settlement, this reach contained an intact valley fill River Style (River Style E along Frogs Hollow Creek). Further downstream, a partly confined valley with bedrock controlled discontinuous River Style (C) occurs. The channel abuts the valley margin along 10 90% of the sinuous valley. Discontinuous pockets of floodplain occur between bedrock spurs or on the insides of bends. The channel is characterized by point bars, point benches, inset features and sand sheets. At the lower end of Wolumla Creek the valley narrows considerably, and a confined valley with occasional floodplain pockets River Style (D) occurs. This is characterized by occasional shallow, narrow pockets of floodplain. The channel abuts the valley margin along 90% of its length. Significant bedrock outcrops induce an irregular series of pools, islands, runs and sand bars. Frogs Hollow Creek, to the east, is a discontinuous watercourse. The intact valley fill River Style (E) at the base of the escarpment is one of the last remnants of a pre-european swamp in Bega catchment (see Fig. 1A). This swamp is threatened by a nickpoint that forms the upper boundary of the confined valley with occasional floodplain pockets River Style (F) immediately downstream. In the middle section of Frogs Hollow catchment, the last remaining floodout River Style (G) in Bega catchment occurs. This reach is characterized by an intact swamp surface over which sands are splayed at the mouth of a discontinuous channel. As noted along lower Wolumla Creek, lower Frogs Hollow Creek comprises a confined valley with occasional floodplain pockets River Style (H). The differing patterns of River Styles along Wolumla and Frogs Hollow Creeks result in differing connectivity of biophysical processes along these river courses. Water, sand and nutrients are readily flushed along Wolumla Creek, with peaked flood flows. In contrast, retention of base flows, fine grained sediment and nutrients is much more significant along the discontinuous channels of Frogs Hollow Creek. These conditions result in the maintenance of remnant habitat niches along swamp zones.

14 104 G. Brierley et al. / Applied Geography 22 (2002) Assessment of geomorphic condition and river recovery potential Effective river management plans must work with the character and behaviour of each reach, the linkage of biophysical processes that determine the present and likely future behaviour of the reach, and associated assessments of river condition and recovery potential. Although significant research has focused on ecological condition and recovery potential components (e.g. Gore, 1985; Gore, Kelly, & Young, 1990; Milner, 1994; Bradshaw, 1996; Hobbs, 1997), few procedures are available for evaluating these components in geomorphic terms (cf. Sear, 1994; Brookes, 1995; Brookes & Sear, 1996). Those tools that are available need to be expressed in terms of practical guidelines for assessing river condition and recovery potential. This oversight has been addressed in the River Styles framework (Fryirs & Brierley, 2000). Any assessment of river condition must be framed relative to some benchmark or reference point (Cairns, 1989; Kondolf & Downs, 1996). However, simple analysis of changes to river forms and processes does not provide a direct measure of geomorphic river condition. In the River Styles framework, geomorphic condition is assessed relative to the natural range of variability that is considered to be appropriate for the River Style and the reach setting, given the present-day controls. Studies of river evolution are used to assess the nature, extent and rate of changes imposed since European settlement (cf. Kondolf & Larson, 1995). This provides an indication of how far from a good or natural geomorphic structure and function differing reaches of river are. Reaches that have fully adjusted to contemporary controls, are self-maintaining, and are operating within their natural range of variability are put in the good category. Reaches that are still recovering and/or have accelerated rates of change are put in the moderate or poor categories, depending on the degree of degradation. Assessment of river condition, in itself, provides an insufficient physical platform from which to rehabilitate rivers. Effective management strategies that work with nature must appreciate the trajectory of change. Extensive geomorphic research on river evolution, magnitude-frequency relations, and notions such as complex response, have highlighted how recovery processes, and their geomorphic consequences, are not necessarily the reverse of geomorphic responses to degradational influences (e.g. Schumm, 1973; Simon, 1989; Hupp, 1992; Renwick, 1992; Fryirs & Brierley, 2000). The critical question here is: if the river were to be left alone, would its condition deteriorate or improve? Principles applied in the River Styles framework follow the lead from ecology, promoting enhanced geomorphic recovery of rivers as a basis for effective management programmes (see Kondolf, 1995a; Fryirs & Brierley, 2000). Limiting factors to geomorphic recovery are identified, such as sediment supply and transport capacity, the nature and variability of discharge (i.e. water transfer), vegetation distribution and character (including seed dispersion), the position of a reach within the catchment, the connectivity of processes throughout the catchment, and off-site impacts of degradation or disturbance in upstream or downstream reaches. Based on principles documented in Fryirs and Brierley (2000), an example of the application of the principles used to assess river condition and recovery potential in

15 G. Brierley et al. / Applied Geography 22 (2002) Fig. 6. Application of the recovery potential framework for the partly confined valley with bedrockcontrolled discontinuous floodplain River Style. Note: In this figure a series of condition and potential recovery endpoints are identified for the partly confined valley with bedrock-controlled floodplain River Style in Bega catchment. Moving down the left-hand side of the figure, good, moderate and poor conditions of the style reflect changes that have occurred since European settlement. The extent of disturbance, and processes occurring in adjacent reaches (especially upstream), determine the likely pathway of adjustment of the reach (on the right-hand side of the figure). The reach can recover towards a restored condition whereby geomorphic structure and function is akin to an intact condition. Alternatively, if systematic or irreversible change has occurred to catchment boundary conditions, the reach will adjust towards a created condition. The recovery trajectory is used to designate appropriate target condition for management of the reach. Such a figure can be further broken down to provide short-to medium-term target conditions for river rehabilitation. The particular patterns of geomorphic adjustment and recovery, and associated identification of goals for river rehabilitation, are River Style specific.

16 106 G. Brierley et al. / Applied Geography 22 (2002) the River Styles framework is shown in Fig. 6. There are two components to this figure. The vertical line on the left represents the continuum from an intact to a degraded condition. The contemporary character and behaviour of the reach can lie at any position along this degradation pathway, depending on the river s sensitivity to disturbance, the character and degree of disturbance, and the time since disturbance. At any stage along this pathway, rivers are adjusting their character and behaviour to disturbance. If a natural system is resilient to disturbance, it oscillates in form around a mean condition and remains close to an intact condition (position A or B on Fig. 6). If disturbance is severe, such that a threshold condition is breached, the river cannot self-adjust, and falls along the degradation pathway (positions C, D or E). The right-hand side of Fig. 6 shows directions of river recovery following the cumulative impacts of disturbance. Two pathways are shown. In the first instance, the river system endeavours to return to a condition akin to its original or intact state (i.e. a restored river condition; position F). Alternatively, if catchment boundary conditions have been altered to such a degree that geomorphic changes to river structure are irreversible, the recovery pathway moves the river towards a new condition, termed river creation (position G). The transition to recovery, termed a turning point on Fig. 6, can occur at any stage along the sliding scale of the degradation pathway, as it is determined by a range of local, reach and off-site constraints. However, in general, the further down the degradation scale a reach sits, the less likely it is to regain a fully restored condition. Ultimately, the endpoint of recovery, whether restored or created, is attained when a reach achieves a structure and function that is self-maintaining under the conditions operating within the catchment. Since effective river rehabilitation strategies work with both the contemporary condition and trajectory of river changes, it is necessary to determine where each reach lies on the pathways indicated on Fig. 6. Given that each catchment includes a variety of River Styles at various stages of degradation and recovery, limiting factors to geomorphic recovery vary not only between catchments, but also between reaches. Placing the condition of a reach in the context of its within-catchment position, and producing an associated map of river recovery potential, provide a biophysical platform with which to derive a realistic catchment-framed vision for river management programmes. Creating a catchment-framed biophysical vision Most river rehabilitation projects in Australia, and elsewhere, have generally been applied in a piecemeal manner over relatively short reaches, without a sound understanding of the broader spatial and temporal context (e.g. Downs & Brookes, 1994; Brookes & Shields, 1996; Newson et al., 1998; Harper et al., 1999). Such reactive strategies are not the most efficient and cost-effective way to achieve rehabilitation success in ecological terms. Projects that fail to consider current trends in sediment delivery and the dominant fluvial processes in the reach are likely to require costly maintenance, or fail to achieve their intended goal (Sear et al., 1995; Sear, 1996).

17 G. Brierley et al. / Applied Geography 22 (2002) All too often, however, this intended long-term goal is overlooked or poorly specified. Defining a catchment-framed vision is a critical early step in effective river rehabilitation (Kondolf, 1995b). A vision statement envisages an improved state for a system that can be achieved at some stage in the future. The mission, goals and objectives of environmental projects fit into this over-arching vision. This provides a basis for assessing whether management efforts are successful. Bringing groups together to develop a shared vision generates the commitment and focus needed for a successful project (Rogers & Bestbier, 1997; Rutherfurd et al., 2000; Koehn et al., 2001). Application of the River Styles framework has been used to identify an achievable structure and function for river courses across a catchment, maximizing the potential to produce a self-adjusting (i.e. natural) river morphology that minimizes the need for invasive management techniques. Reach-scale goals can then be framed within a catchment-wide vision. This vision of what is realistically achievable within a specified time-frame is derived from an understanding of the linkages between biophysical processes within the catchment, recognizing on-going and likely future pressures that will be experienced, and prospective environmental changes (cf. Newson, 1994). From these insights, thresholds of probable concern and associated management responses can be identified (e.g. Mackenzie, van Coller, & Rogers, 1999). Adoption of these principles within NSW DLWC has resulted in coherent and proactive rehabilitation programmes that are spatially and temporally integrated (Table 2). The character and behaviour of individual River Styles, and their downstream pattern, provide an appropriate biophysical framework with which to develop river rehabilitation schemes that fit into the catchment-based vision. Due regard is given to potential off-site impacts, ensuring that balanced perspectives on sediment transfer are determined. For example, it may be pointless to expend significant effort and resource on fixing a downstream reach if a large sediment slug sits immediately upstream, as the future geomorphological behaviour of the downstream reach will reflect river responses to the transfer and/or accumulation of those materials. Application of these principles is exemplified by the designation of a vision for Wolumla catchment in Table 3. Extensive adjustments to river morphology have occurred here since European settlement (Brierley & Fryirs, 1998, 1999; Fryirs & Brierley, 1998, 1999). The catchment vision for management seeks to minimize rates of sediment loss from valley floors, improve riparian vegetation cover, and retain base-flow conditions for longer durations. In turn, this will lead to improved ecological associations along river courses. In general terms, strategies aim to minimize erosion and sedimentation problems by locking up sediment as appropriate. Wherever practicable, zones of instability (such as nickpoints) are prevented from extending further through the catchment. Riparian vegetation plans are tied to the geomorphic structure of the river, with parallel weed management programmes. Trapping of fine-grained materials enhances the retention of base flows, maximizing the potential for aquatic ecosystem functioning and improving water quality in receiving basins (cf. Zierholz, Prosser, Fogarty, & Rustomji, 2001). To achieve these biophysical goals, different reach-based strategies are required for the various River

18 108 G. Brierley et al. / Applied Geography 22 (2002) Table 2 Use of River Styles within the regions of NSW DLWC (as of November 2000) Region Catchment- Identifying Funding Rehabilitation Rehabilitation Assessing River Monitoring Flow Water based vision rare or prioritization plans works capacity for health programmes policy allocation and unique rivers adjustment and planning for licensing conservation North coast P P P P P P P P P X Hunter P P P P P X P P F F Sydney South P P X P P P P P P X Coast Barwon P P F P P P P P P F Central west P P P P P X X X X X Murrumbidgee P P P F F F P P P F Murray P P NA NA NA P F F F F Far west P P NA NA NA F P P F F P = presently using, F = intend use in near future, NA = not applicable (e.g. no rehabilitation plans being done), X = not using River Styles for this purpose

19 G. Brierley et al. / Applied Geography 22 (2002) Table 3 A biophysical vision for Wolumla catchment Overall vision: Community and government working together, with nature, to improve the health of riverine ecosystems. What are we trying to achieve? The Wolumla Catchment Rivercare Plan has set priorities for onground works based on several criteria including: sediment and water storage and delivery issues, exotic weed eradication and planting of native vegetation, enhancing ecological recovery potential, cost effectiveness and demonstration value. What are we managing for? The aim is to return the river system to a sustainable (self-maintaining) geomorphic and ecological condition, minimising the need for ongoing (reactive) maintenance. What do we want the river to be like? Healthier, catchment-wide river system with natural sediment regime, improved water quality, native vegetation and ecological associations. Issue Long-term vision Short-term action Sediment regime Lock up sediment in cut-andfill Upper catchment River Styles at the base of Protect remnant swamps and the escarpment. floodouts from nickpoint retreat. Maintain balance between Cattle exclusion and fencing off. sediment input and output Revegetate riparian and withinalong mid-catchment reaches. channel geomorphic surfaces to Maintain remnant swamps stabilise sediment stores. and floodouts along Frogs Bed control structures to retain Hollow Creek and lower- sediment in within-channel order drainage lines that act swamps. as sediment sinks. Middle-lower catchment Riparian revegetation programmes to reduce rates of channel expansion, and removal of floodplain sediment. Bank control structures to aid sediment accumulation along the reach. Woody debris placement to stabilize in-channel sediments and induce pool development. Cattle access points to reduce bank and bed degradation. Vegetation associations Remove willows and re- establish native vegetation associations along the river course. Reinstate a continuous riparian corridor. Willow control along river courses, with a commitment to sustained maintenance programmes. Replant native vegetation that suits the riparian environment for each River Style, using species that are indigenous to the region. Continued

20 110 G. Brierley et al. / Applied Geography 22 (2002) Table 3 (Continued) Issue Long-term vision Short-term action Water regime Maintain base-flow conditions Conserve and protect swamps and water storage in remnant and floodouts from nickpoint swamps and floodouts for retreat. drought proofing and Undertake riparian and withinecological refugia. channel revegetation Reduce time of travel and programmes. stream powers by flattening Increase channel roughness the hydrograph i.e. reduce through woody debris placement flood peaks. and revegetation of instream geomorphic surfaces. Ecological associations Enhance native terrestrial and aquatic ecological associations. Reinstigate channel-floodplain connections (e.g. between channel habitat and floodplain wetlands). Improve water quality and organic matter retention. Maintain and improve the viability of remnant ecological niches in swamps and floodouts. Reduce channel capacities to reinstigate channel-floodplain connectivity. This requires sediment storage and revegetation of geomorphic units at appropriate places along each River Style. Protect remnant swamps and floodouts. Supply and retain organic matter in the system through native revegetation programmes. Styles along the primary streams, framing target conditions within the broader catchment vision. Identification of reach-based target condition In the past, community groups and their technical advisers found the hardest part of the rehabilitation planning process to be determining the target condition for each reach of stream. As noted by Kondolf (1998), it is critical that rehabilitation programmes move beyond visual descriptions of river character (cf. Rosgen, 1994, 1996) and associated prescriptive, off-the-shelf management responses. Rather, reach-based processes and the implications of water and sediment delivery and vegetation issues must be understood in designating appropriate reach-based plans. Insights into recovery potential indicate how achievable the attainment of a good condition for the reach is, including what actions need to be implemented to achieve this goal. The rehabilitation group then needs to match resources with actions to determine a practical target for the reach (Rutherfurd et al., 2000). In the River Styles framework, understanding of form-process associations in minimally impacted or fully adjusted reaches is used to guide the determination of

21 G. Brierley et al. / Applied Geography 22 (2002) Table 4 Rivercare planning in Wolumla Catchment Background The Wolumla Landcare Group is currently implementing a Rivercare Plan to achieve the goals set out within the catchment-framed vision (see Table 3). NSW DLWC and the Far South Coast Landcare Association are providing technical advice and planning assistance. The first priority of the Rivercare Plan is to protect sediment sinks from incision and sediment removal (i.e. protecting intact valley fill and floodout River Styles). All potential sediment sources are targeted and stabilisation options are outlined. Broader ecological issues such as willow (Salix sp.) control and native vegetation replanting form part of the rehabilitation plan. Community participation One of the challenges of improving river/catchment health is educating people about geomorphic processes. This has been achieved through the use of the River Styles framework. In addition, communities need to be aware of methods of sustainable options for riparian and riverine management, and the necessity to undertake remedial works. To assist with this endeavour, a project has been partnered between the Wolumla Landcare Group, Commonwealth Government (NHT), NSW DLWC, Bega Valley Shire Council, Far South Coast Landcare Association and Land and Water Australia. The project involves rehabilitating three reaches in Wolumla Catchment (Fig. 7), applying a range of rehabilitation techniques. These reaches are: 1. Ticehurst - stabilize sediment stores along a 500-m reach of Wolumla Creek, in a partly confined valley with bedrock-controlled discontinuous floodplain River Style. 2. Sarjents Swamp - apply rehabilitation measures to minimize impacts from a nickpoint that is retreating into an intact tributary fill, in an area suffering from grazing pressure. 3. Frogs Hollow Swamp - protect an intact, high conservation priority remnant swamp from a retreating nickpoint. The sites are all in high-profile areas, close to major roads, and demonstrate several rehabilitation techniques that fit with the natural character and behaviour of the River Style. All sites have revegetation components as part of their respective recovery plans. Project title/river Style Description of remedial works Total (material costs) Ticehurst 150-m mesh fence and bays $ Partly-confined valley with 150-m rock revetment wall (completed) bedrock-controlled rock flume on small nickpoint discontinuous floodplain fencing and revegetation Sarjents Swamp bed-level cattle crossing $2 900 (completed) Intact valley fill log weir fencing and revegetation of swamp Frogs Hollow Swamp concrete flume (currently being designed) $ (planning Intact valley fill fencing and revegetation stage) Continued