In 2019, the Council completed comprehensive City-wide floodplain mapping, identifying areas at risk of flooding. The mapping incorporated a range of future scenarios, including infill development and the continuing effects of climate change.

Following the floodplain mapping, the Council developed and endorsed a Stormwater Drainage Program, which is being implemented in stages over a 15-year period. This program includes the renewal and upgrade of the City’s stormwater infrastructure—such as pipes, culverts, inlets, and junction boxes—to ensure it meets the Council’s service level standards for effective stormwater management.

The Trinity Valley drainage catchment encompasses areas within the suburbs of St Morris, Trinity Gardens, Maylands, and Stepney.

The primary objective of the Trinity Valley Stormwater Drainage Upgrade Project is to enhance flood protection for properties and dwellings against a 1 in 100-year rainfall event. This will be achieved by:

> increasing the capacity of the stormwater infrastructure;
> utilising Council reserves as detention areas; and
> reducing the volume of stormwater conveyed downstream during storm events.

The project is being delivered in four stages. Stages 2 and 3 were completed in May 2024, which involved the installation of large culverts, pipes, and pits within the roadway, followed by full-depth pavement reconstruction at:

> Albermarle Avenue and Ashbrook Avenue, Trinity Gardens (Stage 2); and
> Amherst Avenue and Jones Avenue, Trinity Gardens (Stage 3).

Stages 1 and 4 will be undertaken in 2025.

Similar to Stages 2 and 3, Stage 1 will involve the installation of large culverts within the roadway at Clifton Street, Maylands. Further details will be provided after the design is completed.

Stage 4 will be undertaken in the suburbs of Firle and St Morris.

The work includes:

> the installation of new stormwater infrastructure (i.e. underground pipes and pits);
> building a detention basin and upgrading the St Morris Reserve; and
> some road resurfacing.

For more information, visit the Trinity Valley Stage 4 major projects webpage.

Stage 1 is expected to commence mid-2025 and be completed late 2025 (weather permitting). The dates will be confirmed, and residents and businesses will be notified after contractor procurement has been completed.

The construction work to install stormwater pipes and pits requires large trenches to be excavated in the roadway. Some roads will require a reduction to one-way traffic and small sections of road may be completely closed while works are undertaken. Where necessary, short-term detours will be in place during road closures.

Pedestrian access to properties will always be maintained. However, at some time during construction, access to your driveway may be temporarily restricted. If your driveway access is affected, we will contact you ahead of these works occurring.

Property owners will not be required to modify their existing stormwater systems or connections to the street.

If you have a question about the project, please email: trinityvalley@npsp.sa.gov.au or contact our Citizen Services team on 8366 4555.

To receive updates on our major projects, please subscribe: www.npsp.sa.gov.au/project/subscribe.