Discussion :
• The diversion bank was successful , although maintenance was required on the level sill and stockpiled spoil was removed from the bank outlet as it concentrated the diverted flow . There was no obvious erosion issue resulting from discharge of the diverted water at the level sill outlet or further downslope .
• There were some concerns about the long-term stability of the mid and lower sections of the diversion bank due to the high volumes of flow . Sections had become bare and there was considerable scouring in some sections and deposition in others as the diverted flow established true levels . However , by May 2022 the channel was fully grassed and there were no obvious ongoing erosion issues .
• The construction cost ( and time ) for the diversion bank seems difficult to justify . At that scale , it is only a viable option for that type of erosion feature if the landholder makes a significant inkind contribution with on-property machinery .
• The control head cut did not actively erode . However , this head cut was levelled by the property manager in 2021 . This was a high risk option which could have been disastrous if a heavy storm had occurred but after two wet seasons the site is now well covered and stable - so it was a success .
• Heads cuts where water was removed became increasingly stable and channels grassed over , with the channel profile flattened and gully edges rounded .
• The planned grazing as implemented ( with very long pasture recovery periods i . e . up to 6 months between grazing events ) did not have any known detrimental effects on the improvements in the gullies .
November 2017 April 2021 May 2022 Figure 39 : Grassing up of gully heads and channels ( head cut 5 )
• Ripping and reseeding was largely unsuccessful . Ripping may have reduced run-off in the first wet season but rip lines quickly sealed over . Limited germination of broadcast seed occurred in the rip lines and was generally seca stylo and butterfly pea . Grasses only established in the bare earthworks areas - in the diversion bank channel and on the banks . The banks lost all of the cover , however , after the first dry season but have more cover by May 2022 , especially in areas with more productive soils .
78