Managing waterways - no small task

During National Water Week (21-27 October 2024) it is important to recognise the role that our waterways play in Tasmania.

Waterways are the arteries of our landscapes, pumping nourishing and life-giving water through the environment to every animal, plant and fungi. From the mighty blue gums to the most fragile butterfly, every organism needs water to survive.

What’s more, they need that water to be clean, fresh and reliable, the way that it has been for hundreds of thousands of years. We too must be conscious of the water flowing around us, for we are as intrinsically linked to these systems as any other being.

Recently however, the ever-presence and reliability of some of these precious waterways has been challenged. Threats such as excess fertilisers can run unchecked into meandering streams and introduced weeds can choke the rivers and block the channels. This leads to a myriad of problems, and not just for the environment.

Crack willow (Salix fragilis) is a common sight along larger rivers such as the Derwent but where it has a really damaging impact is in the smaller tributaries – rivers such as the Lachlan and Tyenna. These smaller streams become choked with willows, which then act in accordance with their name (given for their brittle nature), breaking and snapping until eventually the river is full of log jams.

These log jams act to create pools and alter the natural behaviour of the river (which alters the ecology for many freshwater species) but when we really notice their impacts is when it comes to flood times. As rains fall upstream and the rivers rise, these log jams act as damming agents, blocking the river from flowing naturally downstream.

This can then go one of two ways, which we saw in the recent floods in central Tasmania. All that water and force has to go somewhere, so the river either breaks its banks or suddenly dislodges the log jam creating a dangerously fast flowing flash flood with a wall of water and debris racing downstream. And both situations are significantly damaging, with widespread flooding over low lying land often occurring.

One of the best ways to counter this and improve flood resilience in these smaller rivers is removing the willows. We have been working closely with the land management group Derwent Catchment Project to to achieve this.

Over the last few years, we have created and implemented river restoration plans that have seen a significant improvement in river health. This National Water Week, we have cause to celebrate the impacts we have made.

The recent major flooding event in the Derwent Catchment saw a huge amount of rain fall very quickly and widespread flooding across most rivers. This was a great chance to test out how effective these restoration works have been and to our great happiness we can report that in the areas where funded work occurred, these responded very well.

Previous years have seen major flash flooding and breaking of the banks in the Lachlan River given less rain, however this time none of that occurred. The river flowed as it should, straight through the Derwent, sparing the community much heartache and financial loss. There is of course more work to be done.

At Enviro-dynamics, we are very proud to be able to be a part of something making such a tangible impact on health of our waterways, and helping the community to be more resilient to flooding in the process!

See more of this great work at the Derwent Catchment Project