Streambank erosion is an issue in the Wet Tropics due to the combination of heavy rainfall and significant clearing of riparian zones for urban and agricultural development, particularly in the lower catchments.

All estuaries in the Wet Tropics Waterway Health Report Card score poorly for ‘riparian extent’, which gives an indication of how much vegetation there is along rivers and creeks.

Riparian vegetation is important for waterway health for a number of reasons including:

1. Water Quality Regulation
Vegetation in riparian zones helps filter pollutants and sediment from surface water and groundwater running off the land into waterways. By stabilising soil, the root systems of the vegetation help reduce erosion and prevent silt build up, which improves water quality downstream.

2. Flood Mitigation
The role of these root systems in stablising soil is particularly important during heavy rainfall and flood events since it mitigates the risk of soil erosion and landslides. It also helps minimise the intensity of floods by slowing down the flow of water, which allows more time for excess water to be gradually absorbed into the ground.

3. Temperature Regulation
The shade produced by tree canopies over water helps regulate water temperature, which is crucial for fish and other aquatic species that are sensitive to temperature changes.

4. Wildlife Habitat
The wildlife corridors provided by riparian zones along waterways provide shelter, nesting, feeding, and breeding grounds for a many species of birds, insects, amphibians, and mammals. They also enable wildlife to move easily across the landscape ensuring genetic diversity and ecosystem resilience.

5. Rat reduction

It is a common misperception that trees along streambanks harbour rats, which are a pest for farmers, particularly sugarcane. However, research studies have proven that farms with more riparian vegetation have less rat problems because the trees shade out weeds and grasses, which are the preferred habitat of rats.

Read this booklet for more information: https://www.wettropicsplan.org.au/var/nrm/storage/original/application/1c651f42d2de1b96862052aee4bc0652.pdf

6. Carbon Sequestration
Trees and plants act as a carbon sink by absorbing carbon dioxide from the air and storing it in plant biomass and soil.

What’s been done?

In some erosion hotspots affected by flood damage, engineering solutions including rockwalls and pilefields have been constructed as a short-term measure to shore up heavily degraded riverbanks. These help stabilise the riverbank but the only long-term solution to preventing streambank erosion is to have dense riparian verges.

In other areas, local community conservation and landcare groups have been actively restoring riparian zones throughout the Wet Tropics by planting native species and removing invasive plants.