Two large winter rainstorms caused significant damage in the Waihopai, Wairau and Omaka river systems in June and July this year.
Council’s Infrastructure and Community Facilities Committee heard the repair bill was estimated to cost $4.6 million.
Rivers Operations Manager Gregor Punzel said Marlborough’s river flood protection systems of stopbanks and other infrastructure performed well during both events, but there was significant localised erosion and damage at several locations.
“The two significant rain events occurred over a relatively short period of time,” he said. “The June event primarily affected the Wairau River catchment while the July rain caused flooding across southern Marlborough in the Omaka and Taylor rivers.
“The most significant damage occurred along the lower Waihopai, Wairau and Omaka River systems in particularly the stopbank at the Waihopai-Wairau confluence. There was significant erosion of the buffer area as well as the stop bank itself – increasing the vulnerability of the main stopbank.”
While some repairs have been carried out, further repair works were needed as soon as practicable to reduce the risk of further erosion and damage to critical stopbank infrastructure.
Mr Punzel said the rain caused the largest flood levels in both the Omaka and Ōpaoa rivers and the second largest in the Taylor River since monitoring began.
“The stopbank system through Blenheim comfortably managed the July flood flows however, some localised damage occurred including bed scour and degradation,” he said.
