Post-storm erosion decisions on a Hawke's Bay hill-country farm
A 420 ha sheep and beef hill-country farm in southern Hawke's Bay runs 2,800 Romney ewes and 600 rising two-tooth ewes, plus 90 Angus bulls. A February storm dropped 180 mm in 30 hours. Thirty hectares of steep, north-facing slope now has shallow slips and debris flows; a further 60 ha has rilled surfaces. The regional council offers a 50% cost-share for poplar/willow pole planting at $1,200/ha and retirement fencing at $900/ha, capped at $30,000. The farm's overdraft is $180,000 and the bank requires a positive cash surplus this season. Stocking rate is currently 8.5 SU/ha. The slips have exposed subsoil and the owner wants to maintain ewe numbers for a contracted lamb supply.
1. Evaluate the erosion risk and recommend where to retire versus plant, given the council cost-share cap.
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The 30 ha of steep, north-facing slope with shallow slips and exposed subsoil is the highest-risk area: it has already failed and will continue to deliver sediment. Retirement from grazing is the priority there. Fencing 30 ha at $900/ha costs $27,000; the council pays 50%, or $13,500. The 60 ha of rilled surface is lower-risk and can be treated with pole planting at $1,200/ha, but the full 60 ha would cost $72,000, with a 50% council share of $36,000-above the $30,000 cap. A feasible package is to retire the 30 ha and plant about 14 ha of the most severe rills: $27,000 + 14 × $1,200 = $43,800, with the council contribution $21,900, within the cap. The remaining 46 ha should be managed by reduced grazing and natural revegetation.
2. Calculate the impact of retiring 30 ha on stocking rate and recommend how to adjust stock numbers.
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Current total stocking = 420 ha × 8.5 SU/ha = 3,570 SU. Retiring 30 ha leaves 390 ha. To keep 3,570 SU on 390 ha, the stocking rate would rise to 9.15 SU/ha-an 8% increase on the remaining hill, which would raise erosion risk. A safer adjustment is to reduce stock by 30 × 8.5 = 255 SU, so the remaining 390 ha stays at 8.5 SU/ha. That is roughly 255 ewes, or about 9% of the ewe flock. Culling the oldest or least productive ewes is preferable to buying feed, because the bank wants a positive cash surplus. If the lamb contract requires numbers, negotiate a temporary reduction or source 255 SU of grazing off-farm rather than overstocking the erodible hill.
3. Justify a recovery plan to the bank and council, including sequencing and monitoring.
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The plan should be phased to protect cashflow. In the first month, fence the 30 ha highest-risk slope and destock 255 SU; this avoids further slips before winter. In the second phase, plant poles on the worst 14 ha of rills and stabilise the slip toes with debris traps. The council cost-share should be claimed for the retirement fencing first, because it protects the most vulnerable land and is cheaper per hectare. Monitoring should include photographic points, slip counts after each storm, and pasture cover on the remaining 390 ha. To the bank, the key point is that destocking reduces income but avoids a larger erosion liability and protects the lamb contract's long-term supply. Present a three-year budget showing reduced fertiliser and grazing costs offsetting the lower stock numbers.