AgTech, Drainage, Nutrients, Projects, Soil, Water

Drainage and Erosion Planning

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The Arawhata Catchment Integrated Storm Water Management project is drawing to a close, the majority of work is done but farm follow-ups continue. The aim of the project was to reduce crop loss from ponding and minimise erosion of soil to Lake Horowhenua. 

We completed OptiSurface drainage analyses for 26 Levin properties covering 450ha of intensive vegetable cropping. OptiSurface calculates flood patterns and erosion risk and creates cut & fill maps for GPS levelling. An example is shown in our earlier post “Mapping for Drainage”.

Drainage and Erosion Management Plans were developed for each block. The plans identify drainage problem areas and erosion risks and recommend management strategies to respond.

Individual farms have done significant work to prevent erosion and reduce crop damage. Farmer actions to reduce sediment runoff and ponding include realigning bed direction, levelling, grassed headlands and drains and swales and sediment traps.

Stages in headland redevelopment

Original design used narrow headlands subject to pugging in wet weather with high risk of slumping soil into vegetation-free drains
Headland lowered to ensure adequate drainage from furrows. Vegetation being encouraged to protect drain from sediment inflows
Land-shaping created a much wider headland for a greater vegetation buffer between cultivated land and drains
Completed headland with its well-established vegetated buffer filtering sediment from drainage water

Now farms are required to have consent in this catchment, the Drainage and Erosion Management Plans are a useful component of the overall Farm Nutrient Management Plans required.

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