Returning to Minyumai (NSW) for Landscape Rehydration Training

It’s been a while since we updated readers on progress at Minyumai Indigenous Protected Area on the NSW north coast. You may recall from past blogs that NGT has been working with the Bandjalang clan Traditional Owners at Minyumai since early 2022 to plan and implement hydrological restoration of an area of endangered swamp forest.

The project has not been without its challenges, including the major floods of February and March 2022, which left Minyumai inaccessible for several months and caused disruption and trauma for the local community. More recently we have been exploring the various technical challenges and potential implications of the comprehensive hydrological restoration works we have in mind. It was good to put these complexities to the side and get back out onto country at Minyumai recently in November!

The intention was to train up the Minyumai rangers, rangers from Jagun Alliance and also ourselves (Mark and Ben) in the construction of landscape rehydration structures, for which there is huge scope and need to install across the network of over 21 km of eroding drains at Minyumai. Training was provided by our collaborators the Mulloon Institute and generously supported by Jagun Alliance.

The week commenced with a day out walking on country to have a look at the issues and the need for hydrological restoration. In this we were joined by officers from the NSW Department of Climate Change, Energy, the Environment and Water and also the not-for-profit organisation OzFish. It had been quite wet in the lead up and around 30 mm of rain had fallen the night before, so there was plenty of flow in the drains and streams to illustrate what is going on – in terms of the challenges facing the site that have been caused by artificial drain construction more than 50 years ago.

On days two and three we were in the hands of Erin Healy, Tam Connor and Peter Hazell from the Mulloon Institute as they guided us through their Boot Camp training in landscape rehydration. In a nutshell, this covers the why, where and how of building small structures by hand using natural materials to restore the natural hydrology of watercourses, wetlands and floodplains. You might think this is NGT’s bread and butter, and it is, but we were keen for the Minyumai and Jagun Rangers to learn these skills, plus to pick up a few new skills ourselves – using different designs and materials more commonly employed by Mulloon.

Building structures from locally available materials is a cheap and simple solution to particular hydrological issues and is perfect at Minyumai where there is no shortage of logs and branches littering the landscape. The training allowed us to construct two types of “flow-through” structure: pin weirs and brushpacks. When water passes through these structures it is slowed and any sediment and/or debris it is carrying is deposited onto the stream bed upstream, thereby preventing or reversing erosion. There are a number of locations at Minyumai where these structures are required, particularly where flows within natural streams have been accelerated by erosion and/or drainage both up and downstream.

In addition to “flow-through” structures are “flow-over” and “flow-around” structures. During the training, we built a flow-over log-sill bed control structure using local materials. This structure was built in a flowing drain and raised the upstream water level by about 30 cm. We cut an opening in the spoil bank of the drain to allow a portion (about 20%) of the flow to be redirected onto the adjoining ground. The structure took about 4 hours to build and the gallery below tells the story of its construction.

Its was a tough couple of days battling the humidity, mud, thunderstorms, leeches, spiders and all manner of biting insects but the camaraderie and sense of achievement made it all worthwhile. The goal now is to get busy constructing these and other structures across the property to address the impacts of historic agricultural drainage and subsequent erosion.

On the last day of the week, Ben further explored Minyumai, venturing into parts of the property we hadn’t yet set foot on but had our suspicions, from aerial imagery, of the need for restoration works. You might notice that in all the photos above, the dominant understory plants are grasses. These are two introduced pasture species, Setaria (Setaria sphacelata) and Broad-leaved Paspalum (Paspalum mandiocanum), which dominate the areas of Minyumai that were cleared, drained and sown to pasture in c.1970.

With this in mind, it was exciting to discover an area of swamp forest with an intact understory that has never been cleared and converted to pasture (see below photo). This area featured ferns, diverse sedges, aquatic plants and Gahnia and was free of exotic grasses. It provides a valuable reference area to serve as the template for what restoration at Minyumai is aiming to achieve. However, even this area is threatened by erosion of nearby drains, emphasising the urgent need to address the legacy issue of historic agricultural drainage at Minyumai – something that we will continue to support the Minyumai IPA Rangers and Bandjalang clan Traditional Owners with over the years ahead.

This project is supported by the NSW Environmental Trust and the Bandjalang Clan, who are the Traditional Owners and custodians of Minyumai IPA.