1. Forest activities and Water Quality What can we confidently say after 30 years of research?

2. DOES LOGGING IMPACT UPON WATER QUALITY? $64,000 question that largely remains unanswered$64,000 question that largely remains unanswered The question itself is not CONSTRUCTIVE - it offers no solution and no practical help to the industryThe question itself is not CONSTRUCTIVE - it offers no solution and no practical help to the industry

3. TRADITIONAL APPROACH Paired catchment monitored before and after the period of major disturbance.Paired catchment monitored before and after the period of major disturbance. Estimates of suspended solids or turbidity are used to infer increased sediment delivery to streamsEstimates of suspended solids or turbidity are used to infer increased sediment delivery to streams

4. IMPORTANT LIMITATIONS Black-Box ie you can NOT relate the increase in suspended load at the catchment outlet to activities on the slopesBlack-Box ie you can NOT relate the increase in suspended load at the catchment outlet to activities on the slopes Tells us nothing about where the sediment comes from and hence how to manage itTells us nothing about where the sediment comes from and hence how to manage it

5. NEW APPROACH- OPEN UP THE BLACK BOX For water pollution to occur, you need 3 key ingredients; a source of sediment,a source of sediment, delivered directly to the streamdelivered directly to the stream complete failure of any sediment control strategies or BMP’scomplete failure of any sediment control strategies or BMP’s

6. CAN WE BE CONFIDENT? BROAD GENERALISATIONSBROAD GENERALISATIONS WELL ESTABLISHEDWELL ESTABLISHED LIMITED EVIDENCELIMITED EVIDENCE SPECULATIVESPECULATIVE

7. SEDIMENT AND NUTRIENT SOURCES Well Established  Unsealed forest roads are the major sources of sediment in managed forests.  Road usage is a critical factor in explaining sediment production rates on roads.

8. (Reid and Dunne 1984) 10 100100010000 100 1000 10000 100000 Culvert discharge (mL/s) Abandoned Feeder Access Secondary Access Dump Access 5 yr snig track Sediment concentration (mg/L) Heavy use Temporary use

9. 0.001 0.01 0.1 1 10 100 05001000150020002500 Time (secs) Sediment Flux (g/m/s) Road Snig Track Hillslope SEDIMENT SOURCES

10. SEDIMENT AND NUTRIENT SOURCES  Sediment production rates on roads and tracks decline within the time frame of 2- to 5 years  Sediment yeilds from managed forests are lower than those from other landuses primarily agriculture

11. 0.00 0.01 0.02 0.03 0.5123456 0.04 Age (years) Yield (kg/m 2 ) Hillslope 0.00 0.40 0.80 1.20 0.5123456 Age (years ) Yield (kg/ m 2 ) Snig Track Metasediment Red Granite Light Granite RECOVERY OVER TIME

12. SEDIMENT AND NUTRIENT SOURCES  Nutrient concentrations in streams draining forested catchments are considerably lower than those reported for other landuses, primarily agriculture. The dominant cause of increased nutrients in streams if observed, is due to the effects of prescribed burning and wildfire.The dominant cause of increased nutrients in streams if observed, is due to the effects of prescribed burning and wildfire.

13. Limited Evidence  The GHA is not a significant source of sediment due to limited sediment availability, high retention of vegetation cover and spatially variable infiltration rates. SEDIMENT AND NUTRIENT SOURCES

14. Metasediment soil 2.31 t/ha 0.26 0.69 0.35 t/ha GHASnig xbank Red granite soil 11.08 t/ha 0.25 1.62 0.05 t/ha GHASnig

15. SEDIMENT DELIVERY PATHWAYS The degree to which the source is connected or linked to the receiving watersThe degree to which the source is connected or linked to the receiving waters

16. Direct linkage No channel linkage Infiltration Full channel linkage Partial channel linkage Bridge

17. DELIVERY PATHWAYS Well Established  Channelised pathways forming at road drainage outlets form the most efficient conduit for sediment and nutrient delivery to streams.  Sediment delivery ratios are closely associated with the size composition of the in-situ and eroded soil.

18. Full Channel Partial Channel MITRE DRAIN CULVERT Mitres Push Outs Culverts Percentage 0 10 20 30 40 50 60 70 80 90 100

19. Follow the Red Line N 2km Major area of Impact

20. The impact can be widespread The impact of channelised pathways extends beyond a single point or particular road drain and can be catchment-wideThe impact of channelised pathways extends beyond a single point or particular road drain and can be catchment-wide They also become permanent features of the landscapeThey also become permanent features of the landscape

21. DELIVERY PATHWAYS Well Established  Channelised pathways forming at road drainage outlets form the most efficient conduit for sediment and nutrient delivery to streams.  Sediment delivery ratios are closely associated with the size composition of the in-situ and eroded soil.

22. Full Channel Partial Channel MITRE DRAIN CULVERT Mitres Push Outs Culverts Percentage 0 10 20 30 40 50 60 70 80 90 100

23. Follow the Red Line N 2km Major area of Impact

24. The impact can be widespread The impact of channelised pathways extends beyond a single point or particular road drain and can be catchment-wideThe impact of channelised pathways extends beyond a single point or particular road drain and can be catchment-wide They also become permanent features of the landscapeThey also become permanent features of the landscape

25. Maximum contributing length 95m for road gradient of 5 degrees and DHG 7.5 Maximum contributing length 95m for road gradient of 5 degrees and DHG 7.5 Drain discharge hillslope gradient 90 80 70 65 60 55 50 45 40 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 - 155 150 125 100 90 80 70 65 60 55 50 45 40 110 100 90 80 70 65 60 55 50 45 40 95 90 80 70 65 60 55 50 45 40 85 80 70 65 60 55 50 45 40 80 70 65 60 55 50 45 40 75 70 65 60 55 50 45 40 102.55.07.515202545 75 70 65 60 55 50 45 40 95 Road travelway gradient

26. 200 Inter-bank length (m) 56820304050608020010100 5 6 8 20 30 40 50 60 80 10 100 2 year event for T = 30mins 10 year event for T = 30mins 100 year event for T = 30mins

27. EFFECTS OF BEST MANAGEMENT PRACTICES Well established  BMP’s play a significant role in the reduction of adverse effects in forested catchments.  Forest buffer strips are an effective measure in reducing the volume of surface water and sediment/nutrients delivered to a stream.

28. EFFECTS OF BEST MANAGEMENT PRACTICES Limited Evidence  The best location and design of buffer strips in forested catchments of varying topography and landuse.  The specific role and effectiveness of BMP’s on the hillslope compared with those in the near-stream area.

29. CONCLUDING REMARKS The Most Dramatic Impacts On Water Quality Will Come About In Response To The Most Dramatic Landuse Impact-The Most Dramatic Impacts On Water Quality Will Come About In Response To The Most Dramatic Landuse Impact- Broad Scale Slash And Burn- Large Scale Conversion To PastureBroad Scale Slash And Burn- Large Scale Conversion To Pasture