Development of Trigger Levels to Assess Catchment Disturbance on Stream Suspended Sediment Loads in the Magela Creek Catchment,Northern Territory,Australia

Trigger levels for fine suspended sediment (FSS) load in streams are required to identify rainfall-runoff events that have significantly elevated FSS loads, compared with expected background loads, as a result of catchment disturbance. Stream FSS load data collected in the mine-impacted Magela Creek catchment in the wet-dry tropics were used to derive water quality management trigger levels for two approaches – a Before-After-Control-Impact Paired difference design (BACIP) and a regression relationship between observed FSS load and corresponding event discharge characteristics. The results indicate that both the BACIP and regression relationship approaches behave similarly, with similar FSS load events elevated above trigger levels. Notwithstanding this, it is recommended that in order to reliably assess the location and magnitude of a catchment disturbance on FSS load, a combination of BACIP and regression relationship approaches must be adopted. In this study, an event with a FSS load above trigger levels associated with both BACIP and the regression relationship fitted for the downstream site is considered to be significantly elevated as a result of a disturbance within the mine-impacted region. While this technique cannot conclusively determine whether the cause of the disturbance is mine-related or natural (such as fire or bank erosion), it is an efficient statistical method of identifying events that warrant further investigation and management action, if required.     

The historical dimension of French geography

In France, the study of history behind regional geography has suffered a long decline since the late nineteenth century, but a new historical dimension is beginning to emerge. In the nineteenth century, historians showed how much regional character owed to remains from antiquity while historical geographers traced the history of exploration and discovery from ancient to modern times. Vidal de la Blache integrated historical reconstruction with social analysis in the study of regions. Vidal's followers not only characterized the distinctiveness of regional features but also demonstrated that differences in regional ways of life were more pronounced before industrialization and urbanization than later. In the first quarter of the twentieth century, historical investigations by geographers were neither sufficiently comprehensive nor sufficiently rigorous to explain spatial patterns. Historians of the Annales school obtained deeper understandings of social and economic changes and took a broader view of long-term psychological, cultural and geographical changes. Their interpretations of agrarian structures illuminated problems fundamental to the development of European civilization. In the 1970s, reacting against mechanistic analyses of spatial organization, young scholars again turned to historical geography to examine problems of social evolution. At the moment, this revival of historical interest among geographers has not attracted much attention from historians.     

X-ray fluorescence analysis and intra-island exchange in the Society Island archipelago (Central Eastern Polynesia)

We apply X-ray fluorescence (XRF) geochemical analysis to a collection of 'Opunohu Valley lithic artifacts from Mo'orea island to investigate the local scale of raw material procurement, adze production, use, and exchange within the Society Island archipelago. We use these data to document the distribution of non-local versus local volcanic artifacts in 'Opunohu Valley house sites, ritual sites, and specialized sites, as a means for establishing intra-site production and consumption patterns, and access to exotic, possibly superior, stone resources, and how these two themes correlate with site function or household wealth and status. Overall, 30% of the artifacts analyzed via WDXRF derive from non-local sources, notably two other islands in the archipelago outside of the political boundaries of Moorean chiefdoms. Our case study thus provides the first direct material evidence of intra-archipelago trade and exchange in the Society Islands. Intra-archipelago trade in adzes was certainly in place by as early as A.D. 1350, if not earlier, and continued up until the time of European contact. In addition, our analyses have identified a local adze production locale in the Afareaitu district of Mo'orea island. The patterns of local versus non-local adze production and exchange strongly suggest that dual interaction spheres were involved. The correlation between adzes and adze-related debris produced from off-island sources and sites with specialized use, which were often reserved for the social, ritual, and political elites in Ma'ohi society suggests that some of the exotic adzes derived from gift exchange between Mo'orea and ruling elites in Tahiti and the Leeward Islands. These adzes from afar would have solidified socio-political and ideological alliances between elites in the Windward and Leeward sectors of the archipelago.