Index of Stream Condition (ISC)
Description and method logic
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.
Sampling metrics for the ISC requires a combination of field and desktop approaches:
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.
Long term stream flow data (15 years)
LiDAR and aerial photography for:
Ecologist, GIS, modellers, database management, water quality assessment
Access to stream flow data, five years of monthly water quality sampling data, Ecological Vegetation Class Benchmark (EVC), 'reference' water quality, field surveys.
Criteria by category
Physical and chemical
Natural resource managers, regional NRM bodies, Waterwatch and community groups may find the ISC outputs useful.
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 2 February 2022. Available at: https://wetlandinfo.des.qld.gov.au/wetlands/resources/tools/assessment-search-tool/index-of-stream-condition-isc/