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A combination of flood plan options is the "most promising way" of reducing the flood risk on the Taieri Plain, Otago Regional Council staff told Mosgiel Taieri Community Board members last night.
Council engineering and hazards director Gavin Palmer outlined four options to mitigate the flood hazard in the Silverstream area, downstream of Gordon Rd.
The first was to widen the Silver Stream corridor between Gordon Rd and Gladfield Rd; option 2 was to install a spillway on the left bank of the Silver Stream between Riccarton Rd and Gladfield Rd; option 3 was to provide a "bunded" storage area beside the existing Gordon Rd spillway on the Silver Stream; option 4 was to move an existing right-bank spillway at Gordon Rd so it spilled directly into a ponding area upstream of Gladfield Rd.
Cr Syd Brown asked if silt and debris would be removed from channel beds to lower water levels, the previous practice of catchment boards.
Mr Palmer said work to remove debris could damage stone channel beds, causing erosion.
"It all helps, but during a big flood event, as we saw in April 2006, this would not make a huge amount of difference."
However, the regional council had received consent to remove gravel from the mouth of the Silver Stream.
Cr Brown and board member John Kelly, commenting on options 2 and 4 respectively, raised concerns over changes to spillways and ponding areas given that residents had bought land in some areas on the understanding some degree of flood protection was in place.
The next milestone was to have the preferred option endorsed by the regional council for the inclusion in the next financial plan, Mr Palmer said after the meeting.