The short answer to that question is – we do!
Before European settlement the gulf ecosystem was protected from stormwater inflows by the extensive low-lying, reedy swamps behind the coastal dunes.
Those areas have now been largely drained and built upon, and stormwater is funneled directly into gulf waters via the Torrens and other rivers and concrete storm drains.
When suburbs and industry began developing in Adelaide there were few, if any, environmental protections. Tanneries and other factories discharged waste directly into streams, drains, or onto land. Contaminated soil is still being remediated throughout the Adelaide Plains.
The Port River, as a focus of industry and shipping for the State, was very significantly affected by industrial pollution and, further, by regular dredging and by shipping threats such as oil spills and ballast water.
Some years ago, wastewater treatment discharges from Bolivar, Glenelg and Christies Beach were shown to be the main source of the nutrients that were causing death of seagrasses of the Adelaide metro coast. In the past few decades improved sewage treatment processing has greatly reduced the nutrient discharges, but there are still other serious polluters, such as Penrice Soda.
Have you seen the Torrens outlet at West Beach after heavy rain? Stormwaters flowing out of the Torrens are typically loaded with sediments washed from its catchment – off building sites, roads and carparks. This fine sediment sits off the coast, settling after a few days of calm weather and stirred up again by wind and waves. The sediment is now a more or less permanent feature between West Beach and Tennyson.
Despite significant improvements in waste processing and disposals and better environmental awareness and controls there will continue to be threats to the gulf from dredging, chemical and oil spills, nutrients and sediments.
We need to keep working on making things better.