News the serious degradation of the Shag River has stabilised will be welcomed by its community, Otago regional councillor Doug Brown says.
The council recently reassessed the shape of the channels of the Waianakarua and Shag Rivers to see how they had changed since the last survey in 2008-09.
The aim of the studies was to help the decision-making process surrounding gravel extraction, floodwater delivery and asset management.
Analysis of cross-sections taken of the Shag River showed between 2009 and 2013 there was an increase in the mean bed level at 16 of the 22 surveyed positions and a decrease at six, a report to the regional council said.
It indicated in the short term the Shag River was showing signs of changing from a state of overall degradation as it was in 2009 to one of aggradation, or stability.
However, the Shag River had not returned to a state of excess gravel accumulation and was still experiencing areas of ongoing bank erosion and channel incision.
The latest assessment showed the channel degradation was more prominent between Craig Rd and Munro Rd, while there was aggradation or minimal change from Munro Rd downstream to Palmerston, and also from Craig Rd upstream to McLew Rd.
Cr Brown said it was now important for the council and communities to look at how the Shag River should be managed in the future.
The analysis of the Waianakarua River showed noticeable amounts of bank erosion between 2008 and 2013, the largest change being seen in the south branch.
''Sediment movement has led to the channel becoming wider in some locations but narrower and deeper in others.''
Both the north and south branches had been affected by gravel extraction between the two study periods.
The report would be presented to the Waitaki District Council and to the Waianakarua and Shag Valley communities.
