To address the current data and understanding knowledge gap in landslide dam inventories related to geomorphological parameters, a new global-scale landslide dam dataset named River Augmented Global Landslide Dams (RAGLAD) was created. RAGLAD is a collection of landslide dam records from multiple data sources published in various languages and many of these records we have been able to precisely geolocate. In total, 779 landslide dam records were compiled from 34 countries/regions. The spatial distribution, time trend, triggers, and geomorphological characteristic of the landslides and catchments where landslide dams formed are summarized. The relationships between geomorphological characteristics for landslides that form river dams are discussed and compared with those of landslides more generally. Additionally, a potential threshold for landslide dam formation is proposed, based on the relationship of landslide volume to river width. Our findings from our analysis of the value of the use of additional fluvial datasets to augment the database parameters indicate that they can be applied as a reliable supplemental data source, when the landslide dam records were accurately and precisely geolocated, although location precision in smaller river catchment areas can result in some uncertainty at this scale. This newly collected and supplemented dataset will allow the analysis and development of new relationships between landslides located near rivers and their actual propensity to block those particular rivers based on their geomorphology.
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In this article we attend to an emergent practice of visualising GIS data in physical geography using the graphics engine of a videogame, Crysis. We suggest these modes of image-making aid the possibility of imagining and disseminating complex geographical data differently by re-contextualising seemingly abstract mathematical information within a human horizon of embodied meaning. Furthermore we argue these ways of imagining are closely linked to the technology and phenomenology of screens which make the presentation of these images possible. We close by reflecting on the possibility that these technologies are shifting the grounds of vision and the geographical imagination of users. 相似文献
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The rate of regrowth of Limaria hians nest material, following a simulated dredging impact, was examined on an extensive L. hians bed off the west coast of Scotland. Within an area of complete coverage of the sea bed by a turf of L. hians nest material, the turf was cleared by diver from 10 × 0.25 m2 plots and the sediment subsequently raked to simulate the passage of a scallop dredge. The areal extent and pattern of nest regrowth were recorded after 6 and 12 months. Control plots showed no significant change in 100% nest cover over the year. In the treated plots regrowth generally occurred from extension of peripheral nest material. Over the initial 6 autumn and winter months treatment plots displayed a mean regrowth of 9.2% of the cleared area, increasing to 15% in the second 6-month spring and summer period. However, no significant difference in growth was found between these periods. After 12 months half the treatment plots exhibited <25% nest cover and none of them contained nest of a thickness comparable to the surrounding bed. Conversion of regrowth rates within the treated plots to the rate of nest advance along a linear front, gave a value of 3.2 cm per year, highlighting the susceptibility of this species-rich biotope to scallop dredging. 相似文献
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Utility of Landsat 7 satellite data for continued monitoring of forest cover change in protected areas in Southeast Asia 总被引：1，自引：0，他引：1
Simon N. Trigg Lisa M. Curran Alice K. McDonald 《Singapore journal of tropical geography》2006,27(1):49-66
Satellite instruments, particularly the Landsat TM (Thematic Mapper) and ETM+ (Enhanced Thematic Mapper Plus) series of sensors, are important tools in the interdisciplinary study of tropical forests that are increasingly integrated into studies that monitor changes in vegetation cover within tropical forests and tropical protected areas, and also applied with other types of data to investigate the drivers of land cover change. However, further advances in the use of Landsat to study and monitor tropical forests and protected areas are threatened by the scan line corrector failure on the ETM+ sensor, as well as uncertainty about the continuity of the Landsat mission. Given these problems, this paper illustrates how ETM+ data were used in an interdisciplinary study that effectively monitored forest cover change in Gunung Palung National Park in West Kalimantan, Indonesian Borneo. Following 31 May 2003, when the ETM+ sensor's scan line corrector failed, we analysed how this failure impedes our ability to perform a similar study from this date onwards. This analysis uses six simulated post-scan line corrector failure (SLC-off) images and reveals that data gaps caused by SLC-off introduce maximum errors of 1.47 per cent and 4.04 per cent in estimates of forest cover and rates of forest loss, respectively. The analysis also demonstrates how SLC-off has transformed ETM+ data from a complete inventory dataset to a statistical sample with variable sample fraction, and notes how this data loss will confound the use of Landsat data to model land cover change in a spatially explicit manner. We discuss potential limited uses of SLC-off data and suggest alternative sensors that may provide essential remotely sensed data for monitoring tropical forests in Southeast Asia. 相似文献
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Remote sensing of fire severity: assessing the performance of the normalized burn ratio 总被引：4，自引：0，他引：4
Several studies have used satellite data to map different levels of fire severity present within burned areas. Increasingly, fire severity has been estimated using a spectral index called the normalized burn ratio (NBR). This letter assesses the performance of the NBR against ideal requirements of a spectral index designed to measure fire severity. According to index theory, the NBR would be optimal for quantifying fire severity if the trajectory in spectral feature space caused by different levels of severity occurred perpendicular to the NBR isolines. We assess how well NBR meets this condition using reflectance data sensed before and shortly after fires in the South African savanna, Australian savanna, Russian Federation boreal forest, and South American tropical forest. Although previous studies report high correlation between fire severity measured in the field- and satellite-derived NBR, our results do not provide evidence that the performance of the NBR is optimal in describing fire severity shortly after fire occurrence. Spectral displacements due to burning occur in numerous directions relative to the NBR index isolines, suggesting that the NBR may not be primarily and consistently sensitive to fire severity. Findings suggest that the development of the next generation of methods to estimate fire severity remotely should incorporate knowledge of how fires of different severity displace the position of prefire vegetation in multispectral space. 相似文献
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