River styles in NSW

Rivers come in a large range of types, processes and sensitivities to change. River types need to be defined by their character and behaviour. River character depends on the setting of the river to its valley, its shape and variety of geomorphic features. Classifying river behaviour requires an understanding of the inherent fragility of the river and its existing geomorphic condition. Describing the condition of a river requires a method to characterise how they function.

The River Styles Framework was developed by Macquarie University, and has been implemented across NSW by the NSW Department of Industry - Water, to form both a description of rivers with similar channel forms and processes, and to incorporate the condition of the river reach and its likely recovery potential, based on the fragility of the river and its geomorphic condition.

River Styles provides a consistent way to define river character and behaviour, and has been used extensively in Australia and internationally to categorise river types and describe river behaviour - see www.riverstyles.com.

The NSW River Styles database captures all the River Styles information collected across NSW. It describes the variety of riverine types and identifies their geomorphic condition, and likely future trajectory towards recovery or towards degradation. The intended use of the River Styles database is to identify river character, based on similar core features and potential to adjust within three geo-attributes; channel character, planform features and bed material attributes. This is explained below.

The framework uses four stages of analysis to provide a platform to develop detailed riverine classification scheme and reach-scale prioritisation for management options to be weighed on a catchment scale. The four stages of the River Styles framework are:

  1. Catchment-wide analysis of river morphology to develop categorisation of river character and behaviour,
  2. Catchment framed assessment of riverine evolution and geomorphic condition
  3. Extension of riverine evolution to assess most likely pathways for future river change and geomorphic recovery,
  4. Development of catchment-based vision, targeting future river condition and prioritisation of management actions

The development of vision statements, priority categories and management actions is not addressed in the NSW River Styles database or mapping tool, but is a step used by users of the database to frame their management options.  The framework then aims to provide a means to categorise rivers by their core features and compare the evolutionary adjustment of river reaches against similar reaches in different geomorphic state. Four key considerations underlie the development of the framework and prioritising management (Brierley and Fryirs 2005). These are:

  • Identifying linkages between river forms and their processes, and their capacity and constraints to adjustment,
  • Procedures to clearly identify controls on river behaviour, and linkages between river reaches, applying from the catchment scale down to geomorphic and hydraulic units,
  • Appraisal of geomorphic condition and recovery potential trajectories are formed, based on identified evolutionary histories and reach scale processes,
  • Development of likely future pathways for riverine adjustment, and prioritisation of management options to encourage geomorphic recovery processes to act.

Each River Style possesses its own suite of valley confinement controls, bed and bank configurations, typical large woody debris loadings (if any) and susceptibility to bed and bank alteration. This is reflected in the identification of geomorphic condition and likely channel alterations in future, termed geomorphic recovery potential. These issues are addressed below.

The diagnostic procedure to classify River Styles commences at the catchment scale, though each river reach is placed within a River Style category. Figure 1 provides the six levels of descriptors used to identify specific River Styles and then place them in the continuous pattern of river shape and complexity progressing downstream.

Classifying river styles

Hierarchy of geo-attributes used to formulate river styles, set out in the NSW River Styles database.

Once the River Styles of a set of reaches are determined and included in the database, additional information relating to the target reach is assessed and included. The key information that is appended to the River Styles classification is:

  1. River styles – detail the physical setting in which the stream occurs. It includes four main groups comprising the swampy meadow group, confined valley setting, partially confined valley setting, and unconfined valley setting,
  2. Fragility – refers to the susceptibility or sensitivity of certain geomorphic categories to physical adjustments and changes when subjected to degradation or certain threatening activities,
  3. Geomorphic condition – a measure of departure from a natural or expected state and can be defined as the ability of a river or reach to perform functions expected for a specific river type,
  4. Recovery potential – provides the potential of the river reach to return to good condition, through the consideration of existing physical disturbance threats.

Prioritisation of management actions, including bed and bank stabilisation engineering options, revegetation and other measures are derived from the recovery potential and fragility of the river, as well as upstream and downstream values and risks to the reach. This is conducted in a qualitative way, to allow more detailed quantitative assessments to be undertaken.

Geomorphic condition and the trajectory of recovery or degradation is explained in the recovery trajectory shown in Figure 2 below.

Trajectory of recovery or degradation is explained

Trajectory of river degradation/remediation (after Brierley and Fryirs 2005).

Geomorphic recovery potential guides have been formed for specific riverine types. Assessing geomorphic condition and geomorphic recovery potential forms Stages 2 and 3 of the River Styles framework (Brierley and Fryirs 2005). The steps to assessing relevant geomorphic condition and recovery potential is presented in detail in a geomorphic analysis case study in the Bega catchment (Fryirs et al 2002, Fryirs 2015) and in the New South Wales wide study on developing the method to derive recovery potential (Fryirs and Brierley 2016).

References

(accessed via www.riverstyles.com )

Brierley, G.J. and Fryirs, K.A. 2005. Geomorphology and River Management: Applications of the River Styles Framework. Blackwell Publications, Oxford, UK. 398pp.

Fryirs, K. and Brierley, G. 2005. Practical application of the River Styles® framework as a tool for catchment-wide river management: A case study from Bega catchment, New South Wales, Australia. 230pp. ISBN 1 74138 153 3

Fryirs, K. 2016. The use and usefulness of geomorphology in river management. In Vietz, G.J., Flatley, A.J. and Rutherfurd, I.D. 2016. Proceedings of the 8th Australian Stream Management Conference, 31 July – 3 August 2016, Leura, New South Wales. River Basin Management Society, Melbourne, Australia. pp 507-514. ISBN 978 0 7340 5298 8.

Fryirs, K. and Brierley G.J. 2016. Assessing the geomorphic recovery potential of rivers: Forecasting future trajectories of adjustment for use in river management. WIREsWater. 3, 727-748.doi: 10.1002/wat2.1158

Fryirs, K.A. 2017. River sensitivity: A lost foundation concept in fluvial geomorphology. Earth Surface Processes and Landforms, State of Science Series. 42, 55-70. DOI: 10.1002/esp.3940

Fryirs, K.A., Wheaton, J.M. and Brierley, G.J. 2016. An approach for measuring confinement and assessing the influence of valley setting on river forms and processes. Earth Surface Processes and Landforms. 41, 701-710.

Fryirs, K.2015. Developing and using geomorphic condition assessments for river rehabilitation planning, implementation and monitoring. WIREs Water. 2(6), 649-667. DOI: 10.1002/wat2.1100

Gurnell, A. M., Rinaldi, M., Buijse, A. D., Brierley, G., & PiƩgay, H. (2016). Hydromorphological frameworks: emerging trajectories. Aquatic Sciences, 78 (1), 135-138.

Kasprak, A., Hough-Snee, N., Beechie, T., Bouwes, N., Brierley, G., Camp, R., Fryirs, K., Imaki, H., Jensen, M., O’Brien, G., Rosgen, D.L. and Wheaton, J.M. 2016. The Blurred Line between form and process: A comparison of stream channel classification frameworks. PLoSONE. 11(3): e0150293