Project 1.7

Reducing sediment sources to the Reef: testing the effectiveness of managing alluvial gully erosion

Led by: Dr Andrew Brooks, GU

Project Summary

Alluvial gully erosion contributes 20-40% of fine sediment from the three largest sediment contributing catchments to the GBR, yet there has been limited effort to manage this major sediment source. Cost effective reduction of sediment from these alluvial gullies requires data on effective management strategies. We will take advantage of a ‘natural experiment’ that occurred when Cyclone Ita passed over existing trial management sites in the Normanby catchment. The project will evaluate the effectiveness of different management strategies to reduce erosion from alluvial gullies. To complement this, we will collect baseline data at additional sites in the Normanby and Burdekin catchments.

Problem Statements

Problem

Following significant investment through the Federal Government’s first Reef Rescue program, alluvial gully erosion was shown to be a dominant source of fine sediment pollution (20-40%) to the GBR, particularly from the large, dry, grazing-dominated catchments in the tropics (eg. Cape York, the Burdekin). However research into the optimal methods for reducing this major source of sediment pollution significantly lags behind research in the management of other, less dominant sources.

How Research Addresses Problem

There is a pressing need to determine effective management practices to reduce sediment yields from alluvial gullies if targets for sediment reduction to the reef are to be met. This project will build on previous investment in gully management trials in the Normanby catchment, particularly as these sites were impacted by Cyclone Ita in early 2014. It will determine which interventions were effective in reducing erosion, particularly during an extreme event and collect baseline data in additional sites (Normanby, Burdekin) ready for further trials of active and passive management approaches. This will provide evidence for the development of cost effective sediment management intervention in key GBR catchments.