Detainment Bunds
What is a Detainment Bund PS120© ?
A Detainment Bund PS120© is a special type of sediment trap to temporarily detain stormwater runoff from pasture lands. It intercepts stormwater run-off by briefly ponding it on pasture to reduce significant amounts of sediment, phosphorus, and pathogens. Runoff ponding is achieved by constructing low earth bunds across valley floors where water flows during high-intensity rain storm events. Water ponding is controlled by a flow structure and a spill way in case of a very high runoff event. Pasture growth in the ponding area is not compromised due to temporary storage and then release of the ponded water.
For best mitigation performance the pond can be held for up to 3 days before release back into the flow pathway. View the images and diagrams below which explain how a Detainment Bund PS120© works.
Photo credit: A.Schnell and Diagram credit: J.P.Paterson.
Conceptualisation of a Detainment Bund
Before rainfall event
A bund is built into the landscape using Lidar and GIS data to determine the best location.
3 days after ponding
Significant amounts of sediment, phosphorus and pathogens are removed from the water during the detainment period.
During rainfall event
Rain water is trapped in the bund for 3 days to allow sediment, phosphorus and e-coli to filter out of the water.
grazing stock return
Stock can be put back on the paddock once the bund’s water has been released.
Interested in learning more about Detainment Bunds?
If you would like to find out more about the conceptualisation, design and effectiveness of a Detainment Bund PS120© for mitigation of phosphorus, sediment and e-coli losses, watch the following two videos. John Paterson, an expert on detainment bunds, from the Phosphorus Mitigation Project Inc. provides the answer the question “I want to build a detainment bund”.
Fernando Avendano talks about how to map the Detainment Bund PS120© across a catchment area using GIS and Lidar technology.
scoping and mapping of potential sites
play the computer generated animation to see how the Detainment Bund PS120© can be built into a catchment area
Visit a Detainment BundPS120©
Take a virtual tour of the the Detainment Bund PS120© built on a farm in the Mangaone catchment – the first ever detainment bund built in the lower North Island. Take the tour to learn more about how they work. Google Earth software is recommended for best viewing results.
Watch our virtual tour of a Detainment Bund on Google Earth
Explore our Detainment Bund built on a farm in
the Mangaone River Catchment to mitigate the
loss of sediment into waterways. Google Earth software is required for viewing
Visit the Mangaone River Catchment Group page
Visit the Mangaone River Catchment Group page to hear from the farmers themselves who are trialling the first ever Detainment Bund PS120© built in the Lower North Island. They provide thoughts and insights as they have experienced the build of the technology in order to mitigate the effects of nutrient and sediment runoff in their catchment.
DOWNLOAD THE DETAINMENT BUND PS120© GUIDE
A comprehensive guide is available below supplied by J.P.Paterson from PMP Inc. which will help you as a farmer make informed decisions about appropriate installation.