Widespread heavy rain along the entire North Coast last week turned a season deficit around with some damage, no surprise considering the volume that tumbled to earth.
Oyster growers on the Mid North Coast watched a good season come to a premature end, with fresh water sending their oysters into hibernation. Others lost rafts of infrastructure losing potentially ‘tens of thousands of dollars’, said Peter Troupe, Camden Haven.
On the Mid Richmond 435mm in 18 hours and 630mm in five days fell on the Bungawalbyn catchment raising the normally placid tea tree creek by five metres in three hours topping at 10m, stranding a thin population of residents in an inland sea. Richmond Valley Council estimates road damage at $3m.
Water spilled into adjacent cropping land, drowning ‘hundreds of acres’ of soybean with water that will remain for a week, said Woodburn SES controller Jim McCormack. Young sugar cane will be affected if cloudy skies ever clear.
Sunday March 22:
A weekend featuring remarkably persistent and narrow troughs dumped more than 248mm of rain on the Mid Richmond between Grafton and Lismore in less than 24 hours filling backswamps and cutting off some low-lying roads – including the Pacific Highway at New Italy on Saturday.
Coffs Harbour and the Dorrigo Plateau west to Point Lookout experienced a similar downpour, fed by a standing wave of frigid air at the top of the atmospheric column, dumped 273mm on the town of Dorrigo itself on Saturday alone with 481mm for the week, only just ahead of New Italy, south of Woodburn, where 470mm fell in the week to Sunday morning with more before sundown. The Pacific Highway was blocked in both directions at New Italy for most of Saturday.
Other centres experienced good falls but nothing so extreme. Tenterfield got 71 on Saturday, Tabulam below it got 24mm. Armidale received 28mm and Inverell, which is experiencing a dream season, was grateful for the 41mm.
Further north on the Tablelands Bolivia took 115mm on the Saturday, with Glen Ines recording 172mm for the week, which helps explain why the Severn and the Mole felt a flood. Glen Elgin, which drains into the top of the Clarence, recorded 138mm in the 24 hours to Sunday morning.
The rain gave all the parched valleys from the Hunter north a good drink, with minor flooding on the Manning and Macleay, while Hastings experienced a moderate event with Mt Seaview recording 232mm to Sunday morning, taking it to 505mm for the week. Upper Pappinbarra, which felt the heat of bushfire five weeks ago, recorded 136mm to Sunday morning.
Turners Flat on the Macleay experienced 159mm by Sunday morning. Kempsey, meanwhile recorded nearly 300mm for the week.
Taylors Arm on the Nambucca recorded 166mm on Saturday, with 331mm for the week dumped on Nambucca Heads – a similar figure to that received at Port Macquarie to the south and Coffs Harbour to the north.
The Orara River which drains the north side of Dorrigo Plateau also recorded a moderate flood as did the Severn west of the divide. The Mole and Dumeresq felt a minor event with Mingoola west of Tenterfield receiving 90mm all up from the days long event.
The Clarence and Richmond only realised minor flooding as most of the rain fell on the coastal flood plain, most by far confined to the forested Bungawalbyn catchment that enters the Richmond at Coraki.
The lack of major flooding was the result of rain falling mostly on lower catchments, and also because of its patchy nature as observed on radar.
It could be said that the New Italy deluge was the result of a major upper atmosphere standing wave combined with the right humidity and temperatures downstairs. A similar event devastated both sides of the dividing range when it occurred over Toowoomba in 2011.