The importance of managing riparian zones for saving the Great Barrier Reef
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Key Points 堏ver the past decade the scientific understanding of the dominant sources of contemporary sediment pollution to the Great Barrier Reef (GBR) has changed dramatically; from models a decade ago which assumed a dominance of hillslope sheet and rill erosion, to multiple lines of empirical evidence which now show that channel network erosion (particularly bank and gully erosion) from savannah grazing land is the dominant sediment source. 堂enches and inset floodplains can account for as much, or more, contemporary fine sediment storage (i.e. on century timescales) as occurs on floodplains. 堔o manage sediment supply to the GBR we need to manage how alluvial sediment stores within the riparian zones of all catchments are remobilized and/or stabilized (i.e. riparian management). 堇rass buffer strips at the paddock scale (which some argue are ineffective sediment and nutrient filters) should not be confused with riparian buffers, which are essential to managing sediment runoff to the GBR. 堉t is time to re-establish a program similar to the Land and Water Australia Riparian Program - with a specific focus on managing sediment supply to the GBR from riparian lands. Abstract Recent research into the sources of post-European settlement increases in sediment yield to the Great Barrier Reef World Heritage Area (GBRWHA) indicate that in most catchments the dominant erosion processes contributing elevated sediment are those associated with the sub-surface sources of bank, gully, and scald erosion (stripping of the soil A horizon). Gully erosion is likely to be the dominant sediment source in the major sediment yielding catchments to the GBR like the Burdekin, Fitzroy, Normanby and Herbert catchments, with a large proportion being the alluvial form, where the erosion is occurring into floodplain deposits. By definition the initiation, and potential control of these alluvial gullies, are inherently linked to riparian zone land management. Bank erosion is also a process that is integrally associated with riparian zone processes, and in catchments such as the Normanby is as significant a source as alluvial gully erosion. Evidence from the Normanby also indicates that the deposition of suspended sediment within the macro-channel is far more significant than previously assumed; a sink that to date has not been accounted for in most catchment sediment budgets. Management strategies aimed at managing water quality delivered to the GBRWHA have not focused to the extent that they need to be on sediment sources derived from the riparian zone, nor to the potential of this zone to mitigate sediment delivery through storage. In this paper we present evidence for the critical role of riparian zone management in reducing sediment inputs to the GBR and suggest a targeted program similar to the former Land and Water Australia Riparian Program, should be re-established for managing sediment runoff to the GBR.
Proceedings of the 7th Australian Stream Management Conference
Geomorphology and Regolith and Landscape Evolution