Wrapping up hydrological restoration works at Stipiturus CP

Posted at 30 Jan 2025 at 11:01h in News, Fleurieu Peninsula Swamps by
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When it comes to hydrological restoration works at Stipiturus Conservation Park (Glenshera Swamp) south of Adelaide, which commenced in 2017, it is pretty much “job done”. While there are still some artificial drains affecting site hydrology towards the downstream end of the swamp on private land, the remediation of them would impact land that is currently used for agriculture, so no work is currently planned for this part of the wetland.

Casting our memory back to 2017, the first works NGT undertook at Stipi were a series of trial sandbag structures within the inflow drain that brings seasonal surface flows into the swamp. These structures lifted water out of the drain and re-engaged the natural, meandering creekline through which the drain had been cut (see figure below). Several years later, with the concept effectively proven, in early 2023 we brought in a small excavator to cover the sandbag structures with soil to make them permanent. Shortly thereafter, high flows in early winter 2023 caused some damage to the recently buried structures. Although we had anticipated the structures would be completely overtopped in a high flow event, early winter rains in 2023 proved to be too much, too soon. So in March/April 2024 we brought the excavator back to undertake repairs, this time laying coir matting over the buried structures as an added measure of protection.

As in 2023, we set up trail cameras to take time lapse images of the structures through winter 2024, allowing us to monitor their performance. A selection of the images is shown below.

Location of the first 7 (of 8) restoration structures, superimposed on the Digital Elevation Model for the Park, showing their intended function to either (a) reinstate the creekline meanders (#1 to #5), or (b) block the artificial bypass drain (#6 to #8).

Structure 1 recently repaired in May 2024, looking downstream.
Structure 1 in August 2024 diverting moderate winter flows out of the drain (left to right) and into the natural creek meanders.
Structure 1 in early December 2024 with it’s crest covered in dense vegetation.
Structure 2 recently repaired in May 2024, looking upstream.
Structure 2 in August 2024 diverting moderate winter flows. Water in the foreground is the pool created by Structure 3 downstream.
Structure 3 in December 2024.
Structure 5 recently repaired in May 2024, looking upstream.
Structure 5 in August 2024 diverting moderate winter flows (right to left) out of the bypass drain and into Glenshera Swamp. The water in the foreground is a pool created by works further downstream,
Structure 5 in December 2024 covered in grasses and sedges.

Trail camera monitoring has shown us that flows through winter and spring 2024 were insufficient to completely overtop the recently repaired structures. This is good news as it means the structures will have had more time to settle and consolidate before they are subject to potentially damaging overtopping flows, which won’t occur until winter 2025 at the earliest.

The vegetation that has established on the structures in spring and early summer 2024 is also very encouraging. While much of this vegetation is non-native, reflecting the adjoining landuse, it will, along with the coir matting through which it is growing, provide excellent erosion protection during inevitable future high flow events. In time, with some management input, weedy grasses could be replaced with native sedges and shrubs.

The benefits of these hydrological restoration works at Stipi are now locked in permanently:

  • re-engagement of the natural inflow creek meanders
  • creation of a series of pools that hold water for far longer than previously, providing increased habitat availability and diversity for aquatic biota
  • prevention of erosion and deposition of sediment downstream
  • improved water quality downstream through slower flow and increased residence time within the creek and pools
  • increased recharge of groundwater
  • increased volume and duration of seasonal surface inflows to Glenshera Swamp, the largest and most intact example of the critically endagered Fleurieu Peninsula Swamp ecological community.

This work has been funded by the Friends of Stipiturus and Hesperilla Conservation Parks through the National Parks and Wildlife Service Friends of Parks ‘Partnership Grants’ Program.

Ben Taylor