Marjetta L Puotinen

Monitoring live fuel moisture content of heathland, shrubland and sclerophyll forest in south-eastern Australia using MODIS data

Live fuel moisture content is an important variable for assessing fire risk. Satellite observations provide the potential for monitoring fuel moisture across large areas. The objective of this study was to use data from the Moderate Resolution Imaging Spectroradiometer to monitor live fuel moisture content of three fire-prone vegetation types (shrubland, heathland and sclerophyll forest) in south-eastern Australia. The performances of four spectral indices (Normalised Difference Vegetation Index, Visible Atmospherically Resistant Index, Normalised Difference Infrared Index centred on 1650 nm and Normalised Difference Water Index) were compared. Models based on Visible Atmospherically Resistant Index and Normalised Difference Infrared Index centred on 1650 nm provided the best results (R2 values of 0.537 and 0.586). An empirical model based on these two indices was developed and its performance compared with a meteorological index traditionally used in this context, the Keetch–Byram Drought Index. The empirical model (R2 = 0.692) outperformed the meteorological index (R2 = 0.151), showing an enhanced capability to predict live fuel moisture content of the fire-prone vegetation types considered.

Impacts and Recovery from Severe Tropical Cyclone Yasi on the Great Barrier Reef

Full recovery of coral reefs from tropical cyclone (TC) damage can take decades, making cyclones a major driver of habitat condition where they occur regularly. Since 1985, 44 TCs generated gale force winds (≥17 metres/second) within the Great Barrier Reef Marine Park (GBRMP). Of the hurricane strength TCs (≥H1—Saffir Simpson scale; ≥ category 3 Australian scale), TC Yasi (February, 2011) was the largest. In the weeks after TC Yasi crossed the GBRMP, participating researchers, managers and rangers assessed the extent and severity of reef damage via 841 Reef Health and Impact Surveys at 70 reefs. Records were scaled into five damage levels representing increasingly widespread colony-level damage (1, 2, 3) and reef structural damage (4, 5). Average damage severity was significantly affected by direction (north vs south of the cyclone track), reef shelf position (mid-shelf vs outer-shelf) and habitat type. More outer-shelf reefs suffered structural damage than mid-shelf reefs within 150 km of the track. Structural damage spanned a greater latitudinal range for mid-shelf reefs than outer-shelf reefs (400 vs 300 km). Structural damage was patchily distributed at all distances, but more so as distance from the track increased. Damage extended much further from the track than during other recent intense cyclones that had smaller circulation sizes. Just over 15% (3,834 km2) of the total reef area of the GBRMP is estimated to have sustained some level of coral damage, with ~4% (949 km2) sustaining a degree of structural damage. TC Yasi likely caused the greatest loss of coral cover on the GBR in a 24-hour period since 1985. Severely impacted reefs have started to recover; coral cover increased an average of 4% between 2011 and 2013 at re-surveyed reefs. The in situ assessment of impacts described here is the largest in scale ever conducted on the Great Barrier Reef following a reef health disturbance.

Assessing the recent (1834-2002) morphological evolution of a rapidly prograding delta within a GIS framework: Macquarie Rivulet delta, Lake Illawarra, New South Wales

The recent morphological evolution of Macquarie Rivulet delta, Lake Illawarra, New South Wales, has been assessed from historical parish maps from 1834, 1892, 1916 and 1927 along with aerial photographs from 1938 to 2002. These images were digitised, georeferenced and analysed in a GIS framework. The 1834 sketch map could not be georeferenced and it was excluded from the calculation of delta progradation areas. Between 1892 and 1927 morphological changes were minimal, probably because the areas were not resurveyed between these map editions. A significant change in morphology between 1927 and 1938 reflects a change in source material from maps to aerial photographs. The research highlights that great care must be taken when utilising historical data. Major morphological changes observed between 1938 and 2002 included the development of a large crevasse splay in the 1960s to 1970s and the abandonment and infilling of the deltas previously active distributary channels. The research shows that the morphological changes observed on the delta can be related to both natural processes and anthropogenic modifications to the catchment and thus could be used in the development of catchment management plans.