Most of the province received more than twice its average monthly rainfall, some districts three or four times, in two major storms in the second and third weeks of the month. Farmland inundation was extensive in all catchments, possibly exceeding that of July 2007.
Floodwater hung around longer in the Wairua, Kaihu, and Lake Omapere catchments than in 2007, farmers said. The western coast of the province went from three droughts in the past four years to flooding, damaged fencelines, fallen trees, and drowned pastures.
Some paddocks re-sown after the drought last summer and autumn will have to be done again at considerable extra cost. Dairy farmers needed to remove cows from low-lying paddocks and go back to supplementary feeding to avoid soil compaction.
Long-lasting floodwater affected dairy farmers in and around the Hikurangi Swamp, to the north-west of Whangarei, on Mangakahia and Wairoa river flats between Whangarei and Dargaville, and on the Kaihu River flats north of Dargaville. Although the water was cold, the length of time and the silt loading was deoxygenating and pastures which died and rotted will have to be cultivated and sown.
Farms nearer Kaikohe and Kaitaia, and in Bay of Islands, were also waterlogged for days, sometimes weeks. South of Whangarei the rainfall totals were lower and damage less severe.
Power outages were widespread and prolonged in the Far North where Top Energy struggled for days to rebuild its network.
The province also coped with major road closures and damages – on SH1 south of Kawakawa and at Moerewa, on Mangakahia Road south of Kaikohe, and SH1 in the Brynderwyn Hills. All vehicles were directed around the Brynderwyn closure for a week and heavy transport spent more than a week avoiding the Kawakawa break by using SH12 through Waipoua Forest and the Hokianga Harbour, adding two hours to what was a one-hour trip.
Missed milkings and disruption to Fonterra milk pick-ups were minimised by the time of the year although many autumn-calving or split-calving herds had to be carefully managed through storm and power outages.
Enhanced Task Force Green work teams began work on July 28 after training. Three teams of four with a supervisor were trained in equipment safety and went out to clear fencelines, remove flood debris from paddocks, and to rake fruit and cut up fallen trees in commercial orchards.
Two of the Government-funded teams were based in Whangarei and the other in Kaikohe, Rural Support Northland co-ordinator Julie Jonker said. They expected to be working for up to three months.
She said many requests had been for livestock feed and the first of 20 or more truck-and-trailer loads had been distributed to needy farms. Five loads came from eastern Bay of Plenty, where farmers and transport operators were keen to repay donations and kindness from the north after that region’s 2004 floods. Fifteen or more loads of donated feed or offers at cost-recovery only were expected from Taranaki.
Dairy farmers Greg and Rachel Alexander, at Parakao on the Mangakahia River just south of Twin Bridges, said the flood damage was extensive – to raceways, fences, water lines, and pastures. The road was cut and vehicles trapped as a huge volume of water and logs came out of the Twin Bridges gorge, fed by the extensive hill country run-off. Fencelines choked with debris had to be cleared so that new posts could be driven and the wires re-tensioned.
Silt-covered pastures would need at least a month to dry out before any tractor work, Greg said.
How to handle silt
Heavily silted pastures must dry out until the silt cracks before any remediation.
DairyNZ’s Northland regional manager Tafi Manjala said heavily silted paddocks were those without green and/or very low covers. When the silt dried enough to crack, the paddocks could be moved or mulched, nitrogen and sulphur applied at 150kg/ha of sulphate of ammonia, and possibly then over-sowed.
If green pasture was showing above a silt layer beneath, Manjala recommended light grazing early in the day before moving the herd to better pastures or supplementary feeding.
Flood silt could contain chemical contaminants or pathogens like neospora or bovine viral diarrhoea. If pasture was starting to rot, bacteria and fungi might be multiplying, as they do in rotting hay and silage.
Cows should not be fed mouldy feed and they couldn’t be fed palm kernel alone as the daily limit was about 7kg/cow.
They did require fibre from pasture or feed. Undisturbed silage would still be good if no water has got in.
Cattle under stress would be susceptible to theileria and mineral levels should be kept up, particularly magnesium.
