Agricultural vulnerability to tephra fall impacts.
Degree GrantorUniversity of Canterbury
Degree NameDoctor of Philosophy
Understanding agricultural impact from tephra hazards and their causal mechanisms is vital when developing mitigation and recovery strategies. It is well documented that tephra can impact agricultural systems. However, forecasting likely impacts has been challenging and focused on creating generalised models where impacts typically increase with tephra thickness or loading. Lack of quantitative data and insufficient sample sizes of impact assessment studies restrict potential analysis. However, previous studies have identified that impacts will be governed by the complex interaction of tephra characteristics (thickness/loading, grain size, leachates), exposed farm characteristics (farm size/type, pre-existing conditions), climate, time of year and existing risk management.
Post-eruption impact assessments (Post-EIA) have been used to retrospectively investigate tephra impacts to agriculture, including exploring how tephra and vulnerability characteristics of exposed farms interact. In this study, Post-EIA are used to investigate impacts to agricultural land from three silicic eruptions (2011 Cordón Caulle, 2008 Chaitén, and 1991 Hudson) in Patagonia. Analysis of 49 impacted farms suggests that the characteristics of tephra fall are important, but that the vulnerability characteristics of the farms have a stronger influence on impact. Findings show appropriate recovery strategies employed by farmers are crucial for reducing losses.
This analysis is used to: 1) develop an improved understanding of the factors that influence agricultural impacts from tephra fall; 2) design standardised impact assessment guidelines and databases; and 3) develop improved tephra fall risk assessment methodologies fragility functions that include different agricultural vulnerabilities due to farm type, intensity, seasonality, and leachable fluoride. These initiatives aim to build predicative capacity and ultimately aid disaster risk reduction strategies.