Heavy rain and flooding have forced the closure of several key highways across Canterbury and the West Coast, with road crews mobilising to repair damage and monitor rising rivers.

New Zealand Transport Agency crews are responding to significant erosion along State Highway 7 near Engineers Camp.

The damage is within the section of highway already closed between Springs Junction and the Hanmer Springs turnoff because of flooding.

The Boyle River remains high at the site of the erosion, and more rain is expected this week. Officials said further erosion is possible and roading teams will fill the damaged areas as soon as conditions allow.

Earlier this morning, State Highway 7, including the Lewis Pass, was closed because of flooding between the Hanmer Springs turnoff and Springs Junction. Drivers are being asked to delay travel or take alternative routes.

Inland Route 70 between Waiau and Stag and Spey is also closed because of fallen trees.

On the West Coast, slips and flooding have affected several highways. Sections of State Highway 73 near Jacksons and Otira were closed earlier in the morning due to slips, while further slips have been reported on State Highway 6 near Harihari.

Motorists are also being urged to take care in the Upper Buller Gorge, where fallen trees have been reported north of Lyell, and on State Highway 65 between Murchison and Springs Junction, where surface flooding remains an issue.

Officials are warning more intense weather is forecast later in the week, which may cause further disruption across the South Island.