Dunedin's floodwaters receded within a few days, but some of the damaged infrastructure will take many months to repair.
Slips, dropouts, damage to road surfaces and blown out stormwater pipes and manholes would all need repairing, Dunedin roading maintenance engineer Peter Standring said yesterday.
Every site where damage had occurred was important, but the council would prioritise finite resources to the sites affecting the most people, he said.
That meant the slip damage to Highcliff Rd, which was an important route for many, would be prioritised ahead of the slip damage to Hatchery Rd, Portobello, which affected fewer people.
Mr Standring said it was too soon to know how long each repair would take, but it would be ''a couple of months'' before the most serious sites were repaired.
Damage to road surfaces, such as in Glen Rd, could be repaired within a few weeks.
Damage to roads as a result of blown pipes beneath the surface would be harder to assess, as the pipes would need to be inspected.
While several trees came down as a result of the rain, most had been cleared by yesterday, he said.
Most of the surface debris had already been cleared away.
Slips and dropouts
Slips and dropouts - slips underneath a road surface - were to be expected from such heavy rain as last week's, Mr Standring said.
''A lot of the hillsides around Dunedin, when they get wet, they tend to move.''
That was because Dunedin's hills were a combination of two things - solid volcanic rock and the loose soil that sat on top of that rock.
Rain caused to the soil to become sodden and heavy, and if prolonged it could soak in far enough until it met the hard rock.
That created a layer of lubrication between rock and soil, and the combination of weight and lubrication triggered slips.
Surface damage to roads
The surface of Dunedin's roads was strong enough to not be affected by flooding. But the base beneath the roads could vary.
With enough rainfall, the finer materials in the base could be washed away by flows beneath the road, Mr Standring said.
In South Dunedin, the land was so low its water table was affected by the tide.
Last week's flooding caused the water table to lift, and the rising and falling water sucked away the finer sediments in the roads' base.
Without fine sediment, a section of the road base was weakened and the surface was effectively hanging above a void. Any weight could break it.
Burst pipes
Dunedin's hills were relatively high and steep.
With significant rainfall, huge amounts of water fed from the heights into the city's stormwater pipes, converging at sea-level areas such as South Dunedin.
The hills acted like huge, elevated header tanks, creating massive pressure running through the stormwater pipes.
Last week, the pressure was simply too much for some pipes, causing them to burst.
Where they burst under a road, such as Sandringham St in St Clair, the road surface was damaged.
Spouts
A common scene during last week's downpour was water spouting from some of the city's mud-tanks, or sumps.
While the system appeared to have failed, the issue was simply water volume, Mr Standring said.
The mud-tanks were designed to filter large debris out of the stormwater system.
Water ran along the road, through the tanks' grilles on the road's surface, and into a sump.
From there it ran through pipes to the road's main stormwater drains, usually underneath roading.
But the volume of water running through those centre pipes was greater than they could manage.
Water was pushed back through the joining pipes, into the sumps, and on to the streets.
