Australian River Assessment System: Review of Physical River Assessment Methods — A Biological Perspective

M. Parsons, M. Thomas, R. Norris
Cooperative Research Centre for Freshwater Ecology
Monitoring River Health Initiative Technical Report Number 21
Environment Australia, 2002
ISSN 1447 1280
ISBN 0 642 54887 0

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Chapter 2 Review of River Assessment Methods (continued)

2.6 State of the Rivers Survey

2.6.1 How did the State of the Rivers Survey come about?
2.6.2 How does the State of the Rivers Survey work?
2.6.3 How does the State of the Rivers Survey assess stream condition?
2.6.4 How does the State of the Rivers Survey link physical and chemical features with the biota?

2.6.1 How did the State of the Rivers Survey come about?

The State of the Rivers Survey was developed in Queensland, in response to a need for detailed information on the physical and environmental condition of streams and rivers (Anderson, 1993a). This information would then be available to the Queensland Department of Primary Industries (DPI) for use in the Integrated Catchment Management process (Anderson, 1993a). The State of the Rivers Survey is not designed to establish the trend or rate of change of stream condition, but rather, it provides a 'snapshot' of the physical and environmental condition of streams. These data can then be used to:

provide an objective and comprehensive benchmark against which future trends and rates of change of conditions can be assessed by conducting follow-up surveys;
provide the fundamental information required to classify rivers and streams; and,
provides an overview to help identify resource management and utilisation practices contributing to the deterioration in physical and ecological condition of rivers (Anderson, 1993a).

The State of the Rivers Survey was developed in two stages. The first stage involved development (Anderson, 1993a; Anderson, 1993b) and testing (Anderson, 1993c) of the method. The State of the Rivers Survey has subsequently been applied to assess stream condition in 26 catchments in New South Wales and Queensland (Anderson, 1999).

2.6.2 How does the State of the Rivers Survey work?

The State of the Rivers Survey methodology aims to assess the condition of homogenous stream sections within catchments (Anderson, 1993a). The use of homogeneous stream sections facilitates comparison of similar stream types among catchments or sub-catchments, and provides an ability to distinguish inherent natural variability from the effects of human impacts. Division of the catchment into homogeneous stream sections is a hierarchical process that involves the following steps:

a map exercise to subdivide streams into homogeneous stream sections on the basis of available data such as geology, soils, sub-catchment structure, stream order, natural and artificial barriers, altitude, catchment slope, stream gradient and vegetation type and cover;
visual reconnaissance of the catchment to test the initial homogeneity and to further subdivide the rivers and streams at appropriate boundaries;
further sub-sectioning is made in the course of conducting the instream surveys;
analysis of the instream site data and testing of homogeneity between sites in the same section may lead to further sub-divisions;
compilation of relevant catchment data, with further possible revision of sections; and,
final classification of stream sections using different combinations of the attributes for different purposes (Anderson, 1993a; Anderson, 1993b).

Within each stream segment, a representative sampling reach is chosen on the basis of the following criteria:

the reach should be representative of the types of habitat, morphology and physical and ecological condition of the stream segment;
to represent habitat diversity, the reach should preferably contain at least two complete pools and riffle/run habitats;
the whole length of the reach should be visible at one location; and,
the reach should contain at least one pool, which should be the largest and deepest in the area (Anderson, 1993a).

The number of reaches sampled within each catchment varies according to the size of the catchment and the required resolution of the survey (Anderson, 1993a).

**Table 2.6.1 Data components and types of variables measured in the State of the Rivers Survey. Compiled from the detailed survey data sheets provided in Anderson (1993b).**
Sub-section elements¹ Section boundaries Sub-catchment centroid Elevation information Hydrology² Water flow Time since last runoff General local conditions Instream water quality measurements³ Site description Grid reference Latitude Longitude Catchment area Altitude Map details Site access details Photograph details Reach environs - temporal and spatial Water level at sampling time Channel pattern Local land use Local disturbance Local vegetation types Floodplain features Local land tenure Overall disturbance rating Channel habitat Channel habitat types Reach length Sketch of reach Cross-sections⁴ Depth⁵ Water velocity⁵ Bed sediments⁵ Bank dimensions Bank sediments	Bank condition Bank stability⁶ Bank slope⁶ Bank shape⁶ Overall bank condition⁶ Factors affecting stability Artificial bank protection measures Levee banks Bed and bar condition Bar type and distribution Bar size Gravel angularity and shape Gravel surface characteristics Bed compaction Factors affecting stability Controls stabilising the bed Passage for fish and other organisms Overall bed stability rating Vegetation Width of riparian zone⁶ Vegetation cover of plant types⁶ Percent exotic species in riparian zone⁶ Local species checklist⁶ Aquatic vegetation - submerged and floating Emergent aquatic vegetation Aquatic habitat Instream debris cover Canopy cover⁶ Vegetation overhang⁶ Root overhang⁶ Bank overhang⁶ Man-made overhang⁶ Overall site rating for all aquatic life Scenic, recreational and conservation values Recreational opportunity type Recreation types suitable for the area Scenic value assessment Initial conservation value assessment

¹ This component is usually completed post-survey, to characterise the final homogeneous stream sections

² This component is desk based and is designed to establish an interface with hydrological and water quality data through HYDSYS

³ Measurement of depth, water temperature, dissolved oxygen, pH, conductivity, salinity, turbidity, secchi depth and water velocity is optional

⁴ One cross section is measured in each habitat type present within a reach

⁵ Measured at up to 15 locations within the cross sectional transect

⁶ Measured for left and right banks

In addition to the map-based data that are used to delineate the initial stream sections, the State of the Rivers Survey consists of 11 data components (Table 2.6.1) that are collected at each representative sampling reach. Each data component is composed of different types of variables that represent the physical and environmental aspects of the stream channel (Table 2.6.1). Variables are generally measured using visual estimation, but some variables require physical measurement or an interpretive rating of condition.

2.6.3 How does the State of the Rivers Survey assess stream condition?

The basis for assessment of stream condition in the State of the Rivers Survey is 'the extent to which the values or perceived function of an attribute has declined from a pristine or undisturbed condition' (Anderson, 1999). A series of condition ratings are produced for each data component. Formulas are used to derive condition ratings, using subsets of variables collected within each component (Anderson 1993b). These condition ratings are based on the extent of degradation from a theoretical maximum of 100%, where 100% percent represents the full value, pristine condition or complete function for the component and 0% represents a complete loss of these (Anderson, 1999). Comparisons with representative sites in good condition are also used to scale the ratings (Anderson, 1999).

Using the condition ratings for each data component, an assessment of condition is derived for each homogeneous stream section (Figure 2.6.1). A final assessment of stream condition within a catchment is achieved by calculating the number of homogeneous stream sections that correspond to each condition rating, for each data component (Figure 2.6.1). The length of stream within each catchment that corresponds to a certain condition can also be calculated (Figure 2.6.1). In addition, an overall condition rating can also be calculated for the whole catchment by resetting the condition ratings for all the data components combined (Anderson, 1993c). Thus, stream condition can be reported on several levels of resolution that can encompass combinations of individual data components or all data components together, as well as individual stream sections or the entire catchment.

2.6.4 How does the State of the Rivers Survey link physical and chemical features with the biota?

The State of the Rivers Survey was designed to 'estimate the ecological condition [of rivers] in terms of the condition of the instream habitat, rather than by conducting flora or faunal surveys' (Anderson, 1993a, p6). As such, the State of the Rivers Survey primarily makes a detailed assessment of components that describe the physical condition of streams, such as channel habitat, bed condition, bank condition, cross-sectional dimension and riparian vegetation (Table 2.6.1). Anderson (1993a) recognised that habitat attributes of general importance to the biota were encompassed by these components. Many of the variables measured in the State of the Rivers Survey correspond with those measured in AusRivAS (see Section 2.2), RHS (see Section 2.8) and Habitat Predictive Modelling (see Section 2.7). Therefore, many of the empirical links between biota and habitat that are encompassed within other methods, are potentially represented by the variables collected in the State of the Rivers Survey.

Figure 2.6.1 Steps in assessing stream condition in the State of the Rivers Survey. The example is derived from an assessment of the Maroochy River Catchment, Queensland (Anderson, 1993c), and shows the bed and bank condition data component only. Variables are collected in each stream segment to represent bed and bar conditions. A condition rating is derived using selected variables and preset formulae. The number of sections that correspond to each condition rating are calculated, to give an overall picture of bed and bar condition in the Maroochy Catchment. Diagram compiled from Anderson (1993c).

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