ENSO Controls Interannual Fire Activity in Southeast Australia

El Niño–Southern Oscillation (ENSO) is the main mode controlling the variability in the ocean-atmosphere system in the South Pacific. While the ENSO influence on rainfall regimes in the South Pacific is well documented, its role in driving spatiotemporal trends in fire activity in this region has not been rigorously investigated. This is particularly the case for the highly flammable and densely populated southeast Australian sector, where ENSO is a major control over climatic variability. Here we conduct the first region-wide analysis of how ENSO controls fire activity in southeast Australia. We identify a significant relationship between ENSO and both fire frequency and area burnt. Critically, wavelet analyses reveal that despite substantial temporal variability in the ENSO system, ENSO exerts a persistent and significant influence on southeast Australian fire activity. Our analysis has direct application for developing robust predictive capacity for the increasingly important efforts at fire management

Assessment of post-wildfire erosion risk and effects on water quality in south-western Australia

Investigations of wildfire impact on water resources have escalated globally over the last decade owing to an awareness of climate-related vulnerabilities. Within Australia, research into post-wildfire erosion has focused on water supply catchments in the south-eastern region. Here, we examine post-wildfire erosion risk and its potential for water quality impacts in a catchment in south-western Australia. The catchment of the Harvey River, which drains from forested escarpments onto an agricultural coastal plain and into valuable coastal wetlands, was burnt by wildfire in 2016. The aims of this study were to determine erosion risk across contrasting landforms and variable fire severity, using the Revised Universal Soil Loss Equation (RUSLE), and to determine whether post-fire water quality impacts could be detected at permanent river monitoring stations located on the coastal plain. RUSLE outputs showed erosion hot-spots at intersections of steep terrain and high fire severity and that these areas were confined to forested headwaters and coastal dunes. Monthly water quality data showed conspicuous seasonal patterns, but that sampling frequency was temporally too coarse to pick up predicted event-related effects, particularly given that the pre-existing monitoring sites were distal to the predicted zone of contamination. © IAWF 2020 Open Access

Mass Movements of Warrumbungle National Park, New South Wales, Australia

The Warrumbungle Range is the mountainous eroded remnant of an Early Miocene shield volcanic complex located in the central west of New South Wales. A high-severity wildfire in Warrumbungle National Park in January 2013 was followed by intense rain, causing a number of debris flows. Several flows impacted on infrastructure such as roads and culverts and posed a severe risk to public safety, prompting a broader assessment of mass movement hazard within the park. High resolution LiDAR DEM revealed 542 locations with evidence of mass movement processes that pre-date the fire. The most common types of mass movement visible in the DEM are rotational slumps (353, 65%). The distribution of these indicated stratigraphic control, with 50% of slumps within 440 m of the volcanics-sandstone geologic contact, and typically occurring within unconsolidated volcanic colluvium and/or in situ deeply weathered volcanics. Debris flows are the next most common mass movement type after rotational slumps. Debris flow scour channels generally occurred on colluvial slopes in more elevated sites, within the volcanic rocks. DEM-extracted morphometric data was used to identify areas of debris flow hazard in WNP. Several large mass movements are morphometrically different, with some evidence for formation under different hydro-climatic conditions. A simple conceptual model of how mass movements contribute to the evolution of the Warrumbungle Range is proposed involving groundwater, deep weathering, slope retreat by mass failure, colluvial deposition and periodic incision by debris flows

A model for assessing water quality risk in catchments prone to wildfire

Post-fire debris flows can have erosion rates up to three orders of magnitude higher than background rates. They are major sources of fine suspended sediment, which is critical to the safety of water supply from forested catchments. Fire can cover parts or all of these large catchments and burn severity is often heterogeneous. The probability of spatial and temporal overlap of fire disturbance and rainfall events, and the susceptibility of hillslopes to severe erosion determine the risk to water quality. Here we present a model to calculate recurrence intervals of high magnitude sediment delivery from runoff-generated debris flows to a reservoir in a large catchment (>100 km2) accounting for heterogeneous burn conditions. Debris flow initiation was modelled with indicators of surface runoff and soil surface erodibility. Debris flow volume was calculated with an empirical model, and fine sediment delivery was calculated using simple, expert-based assumptions. In a Monte-Carlo simulation, wildfire was modelled with a fire spread model using historic data on weather and ignition probabilities for a forested catchment in central Victoria, Australia. Multiple high intensity storms covering the study catchment were simulated using Intensity–Frequency–Duration relationships, and the runoff indicator calculated with a runoff model for hillslopes. A sensitivity analysis showed that fine sediment is most sensitive to variables related to the texture of the source material, debris flow volume estimation, and the proportion of fine sediment transported to the reservoir. As a measure of indirect validation, denudation rates of 4.6–28.5 mm ka−1 were estimated and compared well to other studies in the region. From the results it was extrapolated that in the absence of fire management intervention the critical sediment concentrations in the studied reservoir could be exceeded in intervals of 18–124 years

Modelling the spatial extent of post-fire sedimentation threat to estimate the impacts of fire on waterways and aquatic species

Aim: Fires can severely impact aquatic fauna, especially when attributes of soil, topography, fire severity and post-fire rainfall interact to cause substantial sedimentation. Such events can cause immediate mortality and longer-term changes in food resources and habitat structure. Approaches for estimating fire impacts on terrestrial species (e.g. intersecting fire extent with species distributions) are inappropriate for aquatic species as sedimentation can carry well downstream of the fire extent, and occur long after fire. Here, we develop an approach for estimating the spatial extent of fire impacts for aquatic systems, across multiple catchments. Location: Southern Australian bioregions affected by the fires in 2019–2020 that burned >10 million ha of temperate and subtropical forests. Methods: We integrated an existing soil erosion model with fire severity mapping and rainfall data to estimate the spatial extent of post-fire sedimentation threat in waterways and in basins and the potential exposure of aquatic species to this threat. We validated the model against field observations of sedimentation events after the 2019–20 fires. Results: While fires overlapped with ~27,643 km of waterways, post-fire sedimentation events potentially occurred across ~40,449 km. In total, 55% (n = 85) of 154 basins in the study region may have experienced substantial post-fire sedimentation. Ten species—including six Critically Endangered—were threatened by post-fire sedimentation events across 100% of their range. The model increased the estimates for potential impact, compared to considering fire extent alone, for >80% of aquatic species. Some species had distributions that did not overlap with the fire extent, but that were entirely exposed to post-fire sedimentation threat. Conclusions: Compared with estimating the overlap of fire extent with species' ranges, our model improves estimates of fire-related threats to aquatic fauna by capturing the complexities of fire impacts on hydrological systems. The model provides a method for quickly estimating post-fire sedimentation threat after future fires in any fire-prone region, thus potentially improving conservation assessments and informing emergency management interventions

Scientists' warning on extreme wildfire risks to water supply

2020 is the year of wildfire records. California experienced its three largest fires early in its fire season. The Pantanal, the largest wetland on the planet, burned over 20% of its surface. More than 18 million hectares of forest and bushland burned during the 2019–2020 fire season in Australia, killing 33 people, destroying nearly 2500 homes, and endangering many endemic species. The direct cost of damages is being counted in dozens of billion dollars, but the indirect costs on water‐related ecosystem services and benefits could be equally expensive, with impacts lasting for decades. In Australia, the extreme precipitation (“200 mm day −1 in several location”) that interrupted the catastrophic wildfire season triggered a series of watershed effects from headwaters to areas downstream. The increased runoff and erosion from burned areas disrupted water supplies in several locations. These post‐fire watershed hazards via source water contamination, flash floods, and mudslides can represent substantial, systemic long‐term risks to drinking water production, aquatic life, and socio‐economic activity. Scenarios similar to the recent event in Australia are now predicted to unfold in the Western USA. This is a new reality that societies will have to live with as uncharted fire activity, water crises, and widespread human footprint collide all‐around of the world. Therefore, we advocate for a more proactive approach to wildfire‐watershed risk governance in an effort to advance and protect water security. We also argue that there is no easy solution to reducing this risk and that investments in both green (i.e., natural) and grey (i.e., built) infrastructure will be necessary. Further, we propose strategies to combine modern data analytics with existing tools for use by water and land managers worldwide to leverage several decades worth of data and knowledge on post‐fire hydrology

Post-fire debris flows in southeast Australia: initiation, magnitude and landscape controls

© 2013 Dr. Petter NymanSurface runoff and sediment availability can increase after wildfire, potentially resulting in extreme erosion, flash floods and debris flows. These hydro-geomorphic events supply large amounts of sediment to streams and can represent a hazard to water supply systems, infrastructure and communities. This thesis combines observations, measurements and models to quantify and represent the post-fire processes that result in hazardous catchment responses. The processes that constitute risk to water quality and infrastructure were identified through field surveys of burnt catchments in the eastern upland of Victoria (southeast Australia) where impacts had occurred. The survey established that the majority of high-impact events after wildfire were linked to runoff-generated debris flows, a process previously undocumented in the region. The debris flows were initiated through progressive sediment bulking, and occurred in response to short duration and high intensity rainfall events, within one year after wildfire. Debris flows were confined to dry sclerophyll forests that had been subject to crown fire. Wet forest types displayed comparatively subdued responses, a pattern attributed to the relatively high infiltration capacity in these systems. Infiltration and sediment availability were isolated as the key hillslope components that were sensitive to burning and which strongly influenced catchment processes and debris flow susceptibility. The aims of subsequent work were therefore to develop models of infiltration and sediment availability as controls on hillslope response and use these to quantify changes in key parameters during recovery from wildfire. Infiltration was modelled as function of surface storage (H), matrix flow (Kmat) and macropore flow (Kmac). Macropore flow was found to be the main parameter driving the temporal trends in infiltration capacity during recovery from wildfire. Water repellency was ubiquitous in headwater recovering from wildfire, although the strength diminished during prolonged wet weather conditions, a dependency which could be modelled as a function of monthly weather patterns. Sediment availability was highly variable with soil depth, a feature which contrasts with assumptions underlying commonly used erosion models, typically developed in agricultural systems. The majority of erosion following wildfire was found to occur in a shallow layer of highly erodible material which could be represented through dnc, a parameter describing the depth of non-cohesive soil. This depth of available soil decreased exponentially during recovery. The models of sediment availability and infiltration were effective at capturing both spatial variability and recovery processes and form a basis on which to model debris flow initiation and magnitude in variable landscapes during recovery from wildfire

Using Generalized Fibonacci Sequences for Solving the One-Dimensional LQR Problem and its Discrete-Time Riccati Equation

In this article we develop a method of solving general one-dimensional Linear Quadratic Regulator (LQR) problems in optimal control theory, using a generalized form of Fibonacci numbers. We find the solution R(k) of the corresponding discrete-time Riccati equation in terms of ratios of generalized Fibonacci numbers. An explicit Binet type formula for R(k) is also found, removing the need for recursively finding the solution at a given timestep. Moreover, we show that it is also possible to express the feedback gain, the penalty functional and the controller state in terms of these ratios. A generalized golden ratio appears in the corresponding infinite horizon problem. Finally, we show the use of the method in a few examples

DNA vaccine expressing the non-structural proteins of Piscine orthoreovirus delay the kinetics of PRV infection and induces moderate protection against heart -and skeletal muscle inflammation in Atlantic salmon (Salmo salar)

Piscine orthoreovirus (PRV) causes heart- and skeletal muscle inflammation (HSMI) in farmed Atlantic salmon (Salmo salar). Erythrocytes are the main target cells for PRV. HSMI causes significant economic losses to the salmon aquaculture industry, and there is currently no vaccine available. PRV replicates and assembles within cytoplasmic structures called viral factories, mainly organized by the non-structural viral protein mNS. In two experimental vaccination trials in Atlantic salmon, using DNA vaccines expressing different combinations of PRV proteins, we found that expression of the non-structural proteins mNS combined with the cell attachment protein r1 was associated with an increasing trend in lymphocyte marker gene expression in spleen, and induced moderate protective effect against HSMI.publishedVersio