Drainage works in the Paretai area on the lower Clutha River are struggling to cope with more intensive land use and coastal erosion.
The Otago Regional Council has proposed three stages of work to manage the risks faced by the flat, low-lying area, a report to its engineering and hazards committee says.
A recent review of the standard of land drainage provided to the Paretai part of the lower Clutha flood protection and drainage scheme found more intensive farming practices meant the level of protection provided did not meet the expectations of ratepayers.
Engineering manager Ramon Strong said rates of coastal erosion in Molyneux Bay and potential climate change effects seemed set to further compound the limitations of the system, which was constructed in the 1960s and 1970s.
As a result, the review recommended modifications to the Paretai pumping station, the mechanical cleaning of a key feeder drain to the pump station and in, the longer term, developing a more substantial direct link between the drainage network and the Koau branch of the Clutha River.
Work on the drain was scheduled to begin this financial year, with modifications to the pumping station included in the long-term plan for 2011-12 and investigations of a new drainage outlet to start in 2010-11.
The drainage work was estimated to cost $300,000 and modifications to the pumping station $200,000.
Cr Stephen Woodhead said the area's gravity drainage was coming under pressure and the council needed to "keep an eye on it".
The problem had been compounded by additional areas of the low-lying land being drained and converted to farming.
Committee members recommended the report be presented to the Lower Clutha Scheme Liaison Group.
