A new analysis showing there has been little change in the structure of the lower Rees River should reassure concerned Glenorchy residents, the Otago Regional Council says.
''Channel Morphology of the Rees River, Otago'' was presented to the Otago Regional Council's engineering and hazards committee on Wednesday.
The report incorporated the cross-sections of the river from November 2011, LiDAR (aerial surveying) data from October 2011 and doctoral research funded by the council.
Environmental engineering and hazards director Gavin Palmer said results of the analysis showed very little net change in bed level and channel location in the river between 2006 and 2011.
It also showed minimal net change since survey data was first collected in the reach in the 1990s.
''Substantial changes in morphology over relatively short time-scales can occur in this area.''
However, that was generally balanced by a lowering of the channel elsewhere.
Growth of the delta out into the lake was occurring near Glenorchy and the PhD study showed showed the delta shoreline had grown about 120m between 1966 and 2007.
Between December 2006 and November 2011, a general trend of net deposition of material in the river bed occurred near the Rees River bridge. A more defined channel formed at the two sections immediately upstream of the bridge, he said.
''This is consistent with long-term trends in this reach.''
The report would be taken to the community to get its feedback and its knowledge of the area incorporated.
Cr Duncan Butcher said there was a perception in the community that shingle was building up in the river.
There had been calls since the 1994 flood for barriers to be built or the river diverted, he said.
''It's quite amazing that since 2006, there hasn't been a lot of change. This should give them some reassurance it isn't as bad as they thought.''
The committee recommended the report be given to the Queenstown Lakes District Council, Department of Conservation and the Rees Valley community.
