Wetland Restoration on Private Land Case Study 4: Cashmore District

This is the fourth of our early works case studies, where we review a trial sandbag structure installed at Cashmore.

This project involved the installation of a temporary sandbag weir in an artificial drain on a private property near Portland, in far south-western Victoria. The temporary weir was constructed using sandbags made from geo-textile material placed to form a weir wall and overflow sill within the existing drainage channel. The trial sandbag structure is designed to function as a drainage regulation weir, where water flowing out of the drainage channel is retained to promote pooling of the backwater into the natural wetland depression located directly upstream. In this instance, the landholder was interested in restoring the natural wetland area – noting that this area had become much drier since the construction of the drain – as the wetland area itself was considered to be of marginal value for agricultural purposes.

The temporary sandbag weir was installed in early June, prior to the above average July rains in that district, being completed by the landholder, members from a local landcare group and Nature Glenelg Trust.  The weir structure has been designed to recreate a 4 hectare wetland area by restricting drainage outflows by up to 60 cm within the existing drainage channel.  NGT’s Lachlan Farrington put together a short summary of the action, which can be viewed below:

Temporary trial weir structures provide both Nature Glenelg Trust and the landholders we work with, with an inexpensive and low risk approach to trialing wetland restoration measures. Once the functionality of the structure and its wetland restoration impact have been assessed by both parties – under real conditions – a permanent structure can be designed and installed according to a set of agreed criteria. In this way, trial structures can provide a valuable (no-obligation) first step, along the path to providing lasting, self-sustaining and effective wetland restoration solutions in the region.

Trial structures are not necessary at every site, but are a good option for people who are tentative about making the leap to a permanent structure, without having the opportunity to see what the potential inundation effect will be first under a range of settings and conditions. If you are interested in having a wetland restoration trial undertaken on your property, please contact us here.

This Case Study is the fourth in a series to illustrate wetland restoration in practice, delivered through Nature Glenelg Trust’s Wetland Restoration Program on Private Land and funded by the Australian Government.

Image I. The temporary sandbag weir, operating nicely after a substantial rainfall event. Over flow sill levels can be altered to suit landholder expectations.

Image II. The background view from the weir location shows the backwater inundation affect. The retention of fresh water here will help with restoring the wetland area present in the background.