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Index of Stream Condition (ISC)

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Victorian Department of Environment and Primary Industries

Latest documentation


Designed for use in

Victoria, Australia



Assessment purpose

Prioritisation, Processes and components, Values/Services

Assessment criteria

Physical and chemical, Flora, Fauna

Method type

Field, desktop


Short term – Three to four sites can be surveyed in a day; macroinvertebrate sampling is required in autumn and spring. The methodology is designed for ongoing monitoring over many years.


Region, Site/habitat

Wetland system


Description and method logic

Method purpose

Designed as a spatial benchmarking process the ISC is used to assess stream condition and detect long-term changes in overall stream condition over whole catchments.


The Index of Stream Condition (ISC) brings together data from a variety of sources to give a detailed overall picture of river condition. Five sub-indices make up the ISC score - Hydrology, Water Quality, Streamside Zone, Physical Form and Aquatic Life.  Each sub-index comprises individually measured variables.

The ISC is evaluated for individual river reaches, which are generally between 10 and 30km long, with similar hydrological, vegetation and landscape characteristics. Although, the 2013 documentation for the vegeation sub index was produced using LiDAR across the entire ISC network. Outputs from the ISC project feed directly into Catchment Management Authority (CMA) regional Waterway Health Strategies.

Method logic

Sampling metrics for the ISC requires a combination of field and desktop approaches:
  • Aquatic life indicators are collected via field sampling using AusRivAS, SIGNAL, EPT and assessing the number of macroinvertebrate families present
  • The Hydrology metric is assessed using a combination of in-stream gauging and hydrological modelling
  • Variables for Streamside Zone and Physical Form are measured using LiDAR and aerial photography, allowing for a wider site assessment
  • Water Quality is measured using field sampling of physicochemical parameters

Each sub-index is rated against a reference condition and scored between 0 and 10 with the overall index scored out of 50. The overall score is not an aggregate of the five sub-indices. The ISC is weighted to recognise that a low score in one sub-index may have a limiting effect on stream health even if other sub-indices score highly. The total ISC score is categorised into one of five groups of condition - excellent, good, moderate, poor and very poor.

A benchmarking exercise of Victorian streams was carried out in 1999. The method was reviewed and variables changed or added where it could be shown the change was an improvement on the old method, it had been rigorously tested and it conformed to the original variable criteria. The revised methodology was used in 2004. Analysis of the results showed no major change had occurred since 1999. The third benchmark report in 2010 outlined further improvements from the 2004 methodology, most importantly, the addition of LiDAR and aerial photography for assessing Streamside Zone and Physical Form metrics. Additionally, the introduction of these techniques allowed for wider applications in flood risk mapping, flood warning, dam hydrology modelling and general management and planning.

Criteria groupings of the method

Five key components of river health: hydrology, water quality, vegetation, physical form and aquatic life.

Data required

Long term stream flow data (15 years)

Field sampling:
  • Water quality
  • Aquatic biota and habitat

LiDAR and aerial photography for:
  • Bank condition
  • Artificial barriers
  • Instream woody habitat
  • Streamside vegetation condition, extent and distribution.

Resources required

Expertise required

Ecologist, GIS, modellers, database management, water quality assessment

Materials required

Access to stream flow data, five years of monthly water quality sampling data, Ecological Vegetation Class Benchmark (EVC), 'reference' water quality, field surveys.

Method outputs


  • An integrated measure of stream condition using 5 sub-indices.


  • To benchmark stream condition
  • To inform reporting to local, regional, state or Commonwealth agencies
  • To add objective setting by natural resource managers
  • To provide feedback to natural resource managers
  • To assess trade-offs between utilitarian demands on streams and environmental condition
  • High level review of performance against expected outcomes.

Criteria by category

    Physical and chemical

    • Hydrology
      • Seasonality
      • Streamflow
      • Variability
    • Physical form
      • Artificial barriers
      • Bank condition
      • In-stream woody habitat
    • Water quality
      • Salinity
      • Total Phosphorous
      • Turbidity
      • PH


    • Streamside zone
      • Cover trees and shrubs
      • Fragmentation
      • Large trees
      • Overhang
      • Structure
      • Weeds
      • Width


    • Aquatic life
      • AusRivAs macroinvertebrate score
      • Number of macroinvertebrate families in a sample
      • Presence of EPT macroinvertebrates
      • SIGNAL score


Recommended user

Natural resource managers, regional NRM bodies, Waterwatch and community groups may find the ISC outputs useful.


  • Uses information that is easily understood and collectible at the regional scale
  • Methodologies are actively reviewed and improved
  • Utilises a combination of desktop and field assessment.


  • Requires a high level of skill, time and resources
  • Specialised knowledge, equipment and tools
  • to be used for monitoring requires detailed statistical designed and analysis capabilities

Case studies

(not documented)



  1. Department of Environment and Primary Industries (2013), Index of Stream Condition: The Third Benchmark of Victorian River Condition. [online], Department of Environment and Primary Industries, Melbourne. Available at:
  2. Ladson, A & White, L (1999), Index of Stream Condition: reference manual. [online], Department of Natural Resources and Environment, Melbourne. Available at:
  3. Water and Natural Resources Division (2014), ISC 2010 Remote Sensing Metrics version 1.0., Department of Environment and Primary Industries, Melbourne.

Last updated: 7 February 2019

This page should be cited as:

Department of Environment and Science, Queensland (2019) Index of Stream Condition (ISC), WetlandInfo website, accessed 1 February 2023. Available at:

Queensland Government
WetlandInfo   —   Department of Environment and Science