Resilience and vulnerability to Climate Change: Challenges of temporal and geographical scales for geotechnical engineering

The interaction between water and soil particles lies at the heart of the work of geotechnical and geo-environmental engineers. The water content of the subsurface is an important state variable influencing soil behaviour in relation to strength and stability, hydrologic and chemical insulation, sediment budgets and transport and support for biological life. The capacity of many soils to maintain high shear strength and withstand loads applied to them without significant deformation, crushing or erosion, their ability to insulate contaminated sites and filter heavy metals and organic chemicals out of polluted water and their effectiveness in supporting healthy biological life for food production and other ecosystem services, are all examples of vital, and sometimes conflicting services, that soils provide and which are critically dependent on water content.

Three major sources of ecological and social change are reasonably certain in the 21st century:

1. increased urbanisation with more demands placed on subsurface systems and structures, by the energy, transport, mining and environmental sectors
2. increased frequencies, magnitude and duration of droughts and floods as a result of anthropogenic climate change, with likely changes to patterns of precipitation and water retention and
3. significant rise in sea levels as a result of thermal expansion and melting of glaciers, leading to higher risks of erosion of coastal land and weakening of coastal foundations with possible damage to private properties and critical water, wastewater, telecommunications and transport infrastructure.

The paper’s goal is threefold. First, different pathways for the impacts of climate change on subsurface systems are described through the lens of soil-water and land-ocean interactions. Second, a case study from Callala beach in Shoalhaven is presented to illustrate the complexity of making adaptation choices at the interface between land and water, especially as a result of uncertainty and unusual temporal and geographical scales of the problems. Third, the readiness of geotechnical education and practice to deal with these problems is discussed in the context of the difference between risk and vulnerability and the emerging distinction between incremental and transformational adaptation. The paper calls on the geotechnical community to engage more fully in the debate on adaptation to climate futures, going beyond the technical assessment of the integrity of infrastructure systems, and identifying long-term strategies for the conflicting demands we place on the subsurface. This will require innovations and possibly some extension of the spatial and temporal scopes of our experimental, analytical and theoretical methodologies.