Geochemical fingerprinting to target sediment sources in the Oreti catchment

Sediment fingerprinting is a technique for understanding where sediment entering our streams and rivers comes from. The technique utilizes properties of soils and sediments, like their geochemistry, to characterize different erosion sources and determine their relative contributions to the sediment transported through rivers.

Introducing the Haunui erosion and sediment research catchment

Understanding the connectivity between sediment sources and the stream network is critical for the STEC programme. Most longer-term data sets record turbidity and flow data at the downstream end of large catchments, a long way from some erosion sources. This makes it difficult to link discrete sources to their impact on water quality.

Swiss students down under (in so many ways)

Manaaki Whenua hosted 4 Swiss over the spring of 2019 as part of the “Smarter targeting of erosion control” STEC programme. They were here to work on poplars. Two Bachelors students (Ivo Gasparini, Julien Plaschy), one PhD (Feiko van Zadelhoff), and a technical lead (Gianluca Flepp) from the Bern University of Applied Sciences (HAFL) worked at Ballantrae – an old AgResearch farm just over the hill from Palmerston North. One of their supervising Professor’s (Luuk Dorren) also made a short visit to New Zealand. Ian McIvor (Plant & Food Research and the Willow & Poplar Research Trust) provided additional supervision.

Shallow landslide susceptibility analysis supports better targeting of erosion control

High-magnitude rainfall events that trigger hundreds to thousands of shallow landslides in New Zealand’s hill country are associated with significant costs in terms of damage to land and infrastructure, agricultural losses, and impacts on freshwater environments. Landslide susceptibility analysis provides a measure of the relative likelihood of a landslide occurring based on landscape conditions. This information can then be used to better inform targeting of erosion control measures.

Improving understanding of the effectiveness of space-planted trees in reducing shallow landslide erosion

Evidence for the current assumptions on the effectiveness of treatment of erodible hill country in New Zealand is poor. Published reductions in shallow landsliding using space-planted trees range from 70 to 95%. But measured or assessed reductions are often far less than this because plantings are inadequately spaced and/or poorly maintained. There is an obvious gap between what is known in terms of the effectiveness of individual implemented works and the overall effectiveness of these measures at farm and catchment scale. This largely depends on whether trees are planted in the right place, i.e. targeting susceptible slopes.

Landslides, Erosion, and Insurance Claims

Erosion in New Zealand has many social and economic impacts, such as reduced soil fertility and productivity, decreased carbon sequestration, sediment impacts in water bodies, and damage to properties and infrastructure. To better design erosion-related policy and assess trade-offs it is important to be able to accurately assess the impacts of erosion, and the benefits and costs of erosion control. However, the New Zealand literature contains very few studies with spatially explicit estimates of erosion-related damages.

TEST – Temporal Erosion and Sediment Transport model

Since European settlement in New Zealand, large-scale catchment disturbance has led to increased erosion rates and the delivery of fine sediment to rivers, lakes and estuaries. Excessive sediment loads adversely affect downstream aquatic ecosystems. Riverbeds and benthic habitat are smothered, fish become susceptible to disease, and the periphyton and macrophytes on riverbeds are seriously affected by reduced light penetration.

Recent publications & outputs related to STEC