Darwin Harbour
Integrated Report Card

Catchment Disturbance Index

The catchment disturbance index (CDI) assesses the likely impact of different land uses on water quality entering Darwin Harbour. Satellite imagery is used to classify different land-uses and each land use has an “impact to water quality” weighting associated with it. Data are analysed by the Northern Territory Government and results presented as an average CDI across eight regions that make up the Darwin Harbour catchment.

Photo of lands around Darwin taken by Ken Hodge, used under CC BY 2.0.

Scoring method

The catchment disturbance index reports results on a scale from 0.3 (most disturbed) - 1.0 (least disturbed). In order to standardise the reporting scale across all indicators, the catchment disturbance index scale was converted to a 0-100 report card scale using the relationship shown in this graph.


The catchment disturbance index for the entire Darwin Harbour catchment was assessed as in very good condition (A). Typically, the most populated regions (i.e. those around Darwin) displayed higher catchment disturbance. Very poor catchment condition was identified in the Rapid Creek region (E), with poor catchment condition identified for the Darwin City region (D−), and good condition for the City of Palmerston and Elizabeth River regions (B− and B+, respectively). The remainder of the catchment was assessed as being in very good condition.