"We're very very fortunate because if we'd had the intensities for the length of time it was forecasted, we would be having a totally different conversation right now," Ms Lash said.
Instead, rivers were beginning to fall and Lash said the slips that had been found were minor and were being cleaned up.
No one was evacuated overnight despite communities opening their halls ready to welcome anybody in need, Ms Lash said.
"Everything worked like a well-oiled machine, I couldn't be more pleased with how everything worked."
State Highway 6 between Haast and Hokitika has been reopened.
Ms Lash said with SH6 closed from Ross to Makarora, police were out ensuring the road was clear before a second belt of rain made its way up the coast.
The Waiho River at Franz Josef was expected to peak about 2am today, with the Hokitika River expected to follow about 10am.
Earlier, a local State of Emergency was declared for Westland. Travellers had until 6pm yesterday to leave SH6 and were advised to head north towards Hokitika and Greymouth. Anyone camping in the region was told to find accommodation at the nearest township in a campground or motel.
The heaviest rain in the deluge was expected to arrive between about 10pm yesterday and 6am today.
The Waiho River reached its first alarm level at 8m after it earlier appeared to be receding. It was not expected to peak until 2am.
The Hokitika River was experiencing intense rainfall in the ranges, expected to peak at 10am today.
"High tide in Hokitika is around 7am tomorrow, so our teams will be keeping an eye on river levels through the night," West Coast Emergency Management (WCEM) group controller Te Aroha Cook said yesterday, adding that preparations were under way for potential evacuations and emergency services had boosted staffing in the region.
"We’ve got around 1500 people in Franz Josef at the moment, and there’s a lot of traffic on the road. We strongly advise people to take extra care on the roads and keep up-to-date with road conditions and weather conditions."
Earlier, sandbags were being handed out on the streets of Hokitika and Civil Defence staff from across the South Island were pulled in as locals prepared for the massive deluge from an atmospheric river of moisture.
Stuff reported Civil Defence had set up a base of operations inside the council building in Hokitika and staff had been pulled in from around the South Island.
The Westland District Council had prepared at least 500 sandbags for locals to use, "but we ask that people only take what they need to protect their properties".
An emergency operating centre will be set up today to help co-ordinate responses to the storm between the WCEM and the district council.
The National Institute of Water and Atmospheric Research (Niwa) said a "month’s worth of rain in a day" was likely to fall.
The atmospheric river came from a "moisture plume extend[ing] back to northern Australia, where the monsoon is active," Niwa said.
