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Sediment

The Fitzroy Region (including coastal catchments) contributes an estimated 1.5 million tonnes of extra sediment to the Reef as a result of human impacts, 23% of the total sediment that reaches the Reef. 83% of the sediment in the Fitzroy comes from grazing lands which occupy an equal proportion of land use making them a priority industry for the WQIP:2015.

The suspended sediment of most risk to the Reef is the fine fraction.  This is the component that contains most of the nitrogen and phosphorus content (and other contaminants), travels widely in flood plumes rather than all depositing near the river mouth and is very effective at reducing light when in suspension. These characteristics of fine sediments can impact on Reef health in a number of ways. Corals and seagrass can be impacted through smothering, decreased light for photosynthesis, reduced recruitment and increased competition with macro-algae and turf algae. Fauna such as reef fish can also be impacted through reduced juvenile recruitment, changes in the benthic structure and hence food availability, and direct interference with gill membranes.

Furthermore, the impacts of suspended sediment contributes to the cumulative impacts of other stressors (e.g. fresh-water flood plumes, elevated nutrients, impacts from cyclones, increasing sea surface temperatures) to increase the overall impact on organisms of the Reef.

Select the interactive map below to discover where in our catchment the sediment is coming from. You can search by total exported anthropogenic load or load per hectare being delivered from grazing and farming lands in the region. 

The model does not calculate streambank erosion loads for grazing/farming lands. These numbers have been calculated by estimating the stream density in each catchment that is on grazing lands compared to the density of streams on non-grazing/farming lands and allocating the proportion of total streambank load to the landuse 

Please note, these estimates are developed from models and should be considered estimates only. They do, however, provide a good relative comparison between catchments.

[wqip-data component=’pollutant-loads’ category=’Sediment – Fine’ parameter=’Combined’]