Classification of Auckland soil types

Detailed spatial soil property information is vital for sustainable land use management. Application of soil property data spans fields as diverse as civil/structural engineering, agriculture, climate system studies, environmental monitoring and land use policy and decision-making. Soil properties control the way soils behave during seasonal fluctuations and evolution of the hydrological cycle, which must be addressed in myriad land-use decisions. In the context of climate change, it will be particularly important to understand the way soils respond to increasingly variable and extreme weather events.

The geology of Auckland comprises four main units: Waipapa/Murihiku Terrane basement greywacke rocks, Waitemata Group sedimentary, Northland Allochthon sedimentary and Auckland Volcanic Field rocks, which weather to secondary products known to have variable chemistry and physical properties (eg: expansivity, shear strength). However, the causes and spatial distributions are poorly understood (eg: Meffan, 2016) and correlations between properties and protolith are not well established. As a consequence, land-use decisions can be costly (eg: conservative building design) and/or not fit-for-purpose. For example, foundation engineering standards that adopt a conservative approach under the assumption that all soils are highly expansive (eg: Brown et al., 2008).

For this project, we propose to employ research assistants (RAs) to undertake testing on a representative suite of soil samples, including physical, mineralogical/petrographic, chemical and in-situ tests.

The aim of this project is to begin compilation of a database of chemical and physical soil properties which can subsequently be used for statistical analysis (eg: supervised and unsupervised machine learning methods) and spatial analysis in 2/3D to augment current soil classification schemes.

This project presents an opportunity for collaboration between the schools of Future Environment (Geotechnical) and Science (Environmental). Moreover, many of the soil samples will be provided by environmental and engineering consultancy Tonkin & Taylor, making them key contributors and direct stakeholders of the outcomes.