Regional Patterns of Erosion and Sediment and Nutrient Transport in the Goulburn and Broken River Catchments, Victoria R.C. DeRose, I.P.Prosser, L.J. Wilkinson, A.O. Hughes and W.J. Young CSIRO Land and Water, Canberra Technical Report 11/03, March 2003 CSIRO LAND and WATER Regional Patterns of Erosion and Sediment and Nutrient Transport in the Goulburn and Broken River Catchments, Victoria R.C. DeRose, I.P. Prosser, L.J. Wilkinson, A.O. Hughes and W.J. Young CSIRO Land and Water, Canberra Technical Report 11/03, March 2003 Copyright ©2003 CSIRO Land and Water To the extent permitted by law, all rights are reserved and no part of this publication covered by copyright may be reproduced or copied in any form or by any means except with the written permission of CSIRO Land and Water. Important Disclaimer To the extent permitted by law, CSIRO Land and Water (including its employees and consultants) excludes all liability to any person for any consequences, including but not limited to all losses, damages, costs, expenses and any other compensation, arising directly or indirectly from using this publication (in part or in whole) and any information or material contained in it. ISSN 1446-6163 Table of Contents Acknowledgments..................................................................................................................................................... 3 Abstract......................................................................................................................................................................... 4 Main Research Report................................................................................................................................................... 5 Background............................................................................................................................................................... 5 Project Objectives ..................................................................................................................................................... 8 Methods .................................................................................................................................................................... 8 Sediment Delivery through the River Network................................................................................................... 10 Contribution of Suspended Sediment to the Murray River ................................................................................. 12 Nutrient Delivery through the River Network .................................................................................................... 13 Model Inputs ........................................................................................................................................................... 13 River Hydrology and Channel Form................................................................................................................... 13 Hillslope Erosion ................................................................................................................................................ 15 Gully Erosion...................................................................................................................................................... 16 River Bank Erosion............................................................................................................................................. 16 Nutrient Sources – Total P and N ....................................................................................................................... 21 Disaggregation of Mean Annual Loads to Daily Loads...................................................................................... 24 Results and Discussion............................................................................................................................................ 25 Hillslope Erosion Hazard .................................................................................................................................... 25 Gully Erosion Hazard.......................................................................................................................................... 25 Riverbank Erosion............................................................................................................................................... 26 Sediment Sources to the Stream Network........................................................................................................... 26 Nutrient Sources.................................................................................................................................................. 28 Sediment Delivery through the River Network................................................................................................... 28 River Suspended Loads....................................................................................................................................... 29 Bedload Deposition............................................................................................................................................. 29 Nutrient Budget................................................................................................................................................... 30 Contribution to Suspended Sediment Export to the Murray River ..................................................................... 41 Comparison of Suspended Sediment Loads........................................................................................................ 41 Comparison of Nutrient Loads............................................................................................................................ 44 Disaggregation of Annual to Daily Loads........................................................................................................... 47 Testing of Land Use Scenarios ........................................................................................................................... 47 Comparison with NLWRA Results..................................................................................................................... 49 Conclusions............................................................................................................................................................. 49 References............................................................................................................................................................... 50 1 List of Figures (abbreviated titles) Figure 1: Map of the Goulburn and Broken River catchments. .................................................................................. 7 Figure 2: Mean annual rainfall across the Goulburn and Broken River catchments................................................... 9 Figure 3: A river network showing links, nodes, Shreve magnitude of each link (Shreve, 1966) and internal catchment area of a magnitude one and a magnitude four link.................................................................. 10 Figure 4: Conceptual diagram of the bedload sediment budget for a river link. STC is the sediment transport capacity of the river link, determined by Equation 1. ................................................................................ 11 Figure 5: Conceptual diagram for the suspended sediment budget of a river link.. .................................................. 12 Figure 6: Conceptual diagram for the nutrient budget of a river link........................................................................ 13 Figure 7: Distribution of average bank heights and channel widths in relation to upslope contributing area for 48 surveyed sites. ............................................................................................................................................ 15 Figure 8: Predicted hillslope erosion hazard in the Goulburn and Broken River catchments................................... 17 Figure 9: Average density of gully erosion for 10 x 10 km grid cells for the Goulburn and Broken River Catchments................................................................................................................................................. 18 Figure 10: Mapped amount of intact riparian vegetation. ......................................................................................... 19 Figure 11: Predicted bank erosion............................................................................................................................. 20 Figure 12: Pattern of dissolved N input to streams. .................................................................................................. 22 Figure 13: Pattern of dissolved P input to streams.................................................................................................... 23 Figure 14: Measured floodplain width...................................................................................................................... 31 Figure 15: Predicted depth of floodplain deposition. ................................................................................................ 32 Figure 16: Predicted suspended sediment load compared with loads measured at gauging stations within the Goulburn and Broken catchments. ............................................................................................................. 33 Figure 17: Predicted suspended sediment