Waste dump erosional landform stability – a critical issue for mountain mining

Mining is the largest producer of solid wastes which, when released to land or into waterways, can cause harmful environmental impacts. This is mostly due to fluvial erosion, which is highly increased in mountain areas, due to abrupt slopes. We have analysed this situation at a mountain watershed (192 ha), where steep mined sites and their waste dumps are the main source of sediment in a Natural Park. This problem was tackled by building gabion check dams downstream from the mined sites. We used the DEM of Differences (DoD) method to quantify erosion and sediment yield from three waste dumps (5 ha). Their topography and substrate properties were analysed to understand the erosion problem. The sediment trapped by the check dams was quantified by Electrical Resistivity Tomography. The rainfall characteristics triggering an episode that filled the check dams with sediment in the winter of 2009-2010, were studied to confirm whether it was a case of extreme precipitation conditions. The waste dumps sediment yield (353 ± 95 Mg ha-1 yr-1) suggests severe landform instability. Analysis of topographic and substrate properties confirmed long, steep slopes combined with highly erodible materials. The check dams proved to be inefficient in controlling sediment loads, as they had only functioned for four years of 31 of existence, having trapped 13000 ± 660 m3 of sediment, whereas we estimated that the waste dumps have yielded approximately three times more sediment for the same period. Rainfall analyses showed that neither intense nor extreme conditions (return period of 25-35 years) triggered the mobilization of 37 ± 2 Mg ha-1 in a month. This study highlights the fact that mining operations in similar mountainous settings, with equivalent waste dump construction and reclamation practices, are currently unfeasible. We conclude that landform stability cannot be achieved at this site without landform changes

Accuracy assessment of LiDAR elevation data using survey marks

Airborne LiDAR has become the preferred technology for digital elevation data acquisition in a wide range of applications. The vertical accuracy with respect to a specified vertical datum is the principal criterion in specifying the quality of LiDAR elevation data. The quantitative assessment of LiDAR elevation data is usually conducted by comparing high-accuracy checkpoints with elevations estimated from the LiDAR ground data. However, the collection of a sufficient number of checkpoints by field surveying is a time-consuming task. This study used survey marks to assess the vertical accuracy of LiDAR data for different land covers in a rural area and explored the performance of different methods for deriving elevations from LiDAR data corresponding to the locations of heckpoints. Normality tests using both frequency histograms and quantile-quantile plots were performed for vertical differences between the LiDAR data and the checkpoints, so the appropriate measures (the formula 1.96×RMSE or the 95th percentile) can be used for the vertical accuracy ssessment of the LiDAR data for different land covers. The results demonstrated the suitability of using survey marks as checkpoints for the assessment of the vertical accuracy of LiDAR data

GIS Videos: An Annotated Bibliography (92-9)

Describes over 120 educational videos on GIS and related subjects, from government agencies, software and hardware vendors, and independent video companies. This video bibliography is a joint effort of the National Center for Geographic Information and Analysis (NCGIA) and the American Society for Photogrammetry and Remote Sensing (ASPRS)

GIS Videos: An Annotated Bibliography (92-9)

Describes over 120 educational videos on GIS and related subjects, from government agencies, software and hardware vendors, and independent video companies. This video bibliography is a joint effort of the National Center for Geographic Information and Analysis (NCGIA) and the American Society for Photogrammetry and Remote Sensing (ASPRS)

A comparative analysis of routes generated by Web Mapping APIs

Web Mapping APIs (WMAs), such as Google Maps API, are widely used by researchers across different fields to develop geospatial Web applications. Among maps and map functionalities provided through WMAs, route and direction are prominent and commonly available. Given that each WMA uses a different map database and a different set of assumptions, the routes they generate, for the same pairs of origin and destination addresses, are different. Considering the current void in literature on WMAs and the routes they generate, in this paper, select common WMAs are compared and analyzed based on their routing techniques. The results of these comparisons will benefit researchers by helping them better understand the behavior of WMAs in producing routes, which in turn can be used for selecting suitable WMAs for research projects or developing applications (such as navigation and location-based services). The process in which routes are evaluated can also be used as a guideline to help researchers explore behavior of WMAs in generating routes