Coastal discharges

Coastal discharges include urban stormwater drains and outfalls for sewage and industry. The number and locations of these point-source discharges are an important indicator for State of the Environment reporting (e.g. Indicator 7.5: Estuaries and the Sea) 1.

Coastal issues arising from coastal discharges

Stormwater and wastewater inputs into coastal waterways can locally increase freshwater flows to coastal waterways. Coastal discharges may also carry with them the following waterborne wastes 1:

  • toxicants derived from a plethora of domestic and industrial point sources;
  • nutrients from fertilisers, detergents, eroded soils, decomposing lawn clippings, pet faeces, manures, sewage overflows, sewage treatment plants and other nutrient point sources;
  • organic matter from eroded soils, decomposing lawn clippings, pet faeces, manure, sewage overflows and sewage treatment plants;
  • pathogenic organisms from pet faeces, manures and sewage overflows;
  • suspended solids from atmospheric fallout, organic matter (including sewage), and soils eroded from construction sites, roads, market gardens, mining sites and other sources; and
  • litter (plastic containers, junk mail, glass and cans).

Contaminants in stormwater and wastewater can give rise to fish kills, shellfish closures and eutrophication, and to related problems such as harmful algal blooms and anoxic & hypoxic events. These factors can contribute to a reduction in critical habitat areas, and to an overall reduction in biodiversity.

Existing information and data

More information on coastal discharges as an indicator (e.g. reporting scales, outputs, analysis and interpretation and data sources) can be found in the Estuaries and the Sea volume of Environmental Indicators for National State of the Environment Reporting 1. The indicators nutrient point source hazard, industrial point sources and stormwater discharges fit under the broad umbrella of coastal discharges.

  1. Ward, T., Butler, E. and Hill, B. 1998. Environmental Indicators for National State of the Environment Reporting, Estuaries and the Sea, Commonwealth of Australia, pp.81.