Logging Out: Forestry, Transport and the Health of Hokianga Communities

This paper reports on log transportation as a health-related issue in the Hokianga district of Northland at a time when forestry activity in the area is expanding and radical reforms to New Zealand's roading network have been proposed. Drawing on technical information and key informant interviews, the potential impacts of logging trucks on Hokianga roads are considered, the costs associated with forestry traffic are estimated, and the routes most likely to be affected are identified. Possible responses to the log transport problem are discussed, and it is concluded that rural communities such as Hokianga are vulnerable to both logging truck activity and changes in government policy.     

Quantifying septic nitrogen loadings to receiving waters: Waquoit Bay,Massachusetts

Abstract

Waquoit Bay, a shallow bay on Cape Cod, Massachusetts, is exhibiting symptoms of eutrophication, largely attributed to septic nitrogen inputs. This study assessed septic nitrogen inputs by linking a three-dimensional ground-water model, a geographic information system (GIS), and a customized spatio-temporal nitrogen loading program. Owing to the slow speed of ground-water movement, the bulk of septic nitrogen entering the bay lags behind development by nearly a decade. Even if residential development is held at 1989 levels, nitrogen input from septic systems wilt increase by 36% over the current levels. At full residential build-out (i.e., development), septic nitrogen loading will eventually increase to more than twice the current levels.     

HUMAN IMPACTS ON THE ENVIRONMENT: UNPREDICTABILITY AND THE PRIMACY OF PLACE

Landscapes, environments, and ecosystems (i.e., places) are historically and spatially contingent and therefore unique. Generalizations and laws are based on “all other things being equal.” Owing to historical and spatial contingency, all other things are never completely equal and often do not approach that ideal closely enough to allow for reliable prediction. The problem is illustrated by examining effects of grazing and fire suppression on transitions between grass and woody vegetation communities. In three different environments in the southern United States (central Texas, southwestern Virginia, and eastern North Carolina), three different relationships exist between grazing and fire regime, and vegetation. Other examples are common in the geographic and environmental literature. This suggests that the search for a single applicable generalization or predictive model of a given human-induced environmental change that can be applied without accounting for the particular characteristics of places may be futile. Several general ways to address this issue are suggested. First is the recognition that place matters. Conditions specific to a location or region will influence what, how, or even if generalizations apply. Second is the adoption of a “demographic” approach. This is based on the idea that for places, like people, it is possible to make aggregate or probabilistic generalizations or predictions, but these cannot be applied to deterministic prediction of individuals. Third is a synoptic approach based on forecasting not via simple cause-effect relationships, but based on a typology of situations that recognizes and incorporates the unique characteristics of site and situation. Several converging threads of inquiry in geography and geosciences explicitly or implicitly address the issue of historical and spatial contingency. [Key words: landscape, environment, place, prediction.]     

Stochastic model-based methods for handling uncertainty in areal interpolation

Handling of uncertainty in the estimation of values from source areas to target areas poses a challenge in areal interpolation research. Stochastic model-based methods offer a basis for incorporating such uncertainty, but to date they have not been widely adopted by the GIS community. In this article, we propose one use of such methods based in the problem of interpolating count data from a source set of zones (parishes) to a more widely used target zone geography (postcode sectors). The model developed also uses ancillary statistical count data for a third set of areas nested within both source and target zones. The interpolation procedure was implemented within a Bayesian statistical framework using Markov chain Monte Carlo methods, enabling us to take account of all sources of uncertainty included in the model. Distributions of estimated values at the target zone level are presented using both summary statistics and as individual realisations selected to illustrate the degree of uncertainty in the interpolation results. We aim to describe the use of such stochastic approaches in an accessible way and to highlight the need for quantifying estimation uncertainty arising in areal interpolation, especially given the implications arising when interpolated values are used in subsequent analyses of relationships.     

Susceptibility assessment of earthquake-triggered landslides in El Salvador using logistic regression

This work has evaluated the probability of earthquake-triggered landslide occurrence in the whole of El Salvador, with a Geographic Information System (GIS) and a logistic regression model. Slope gradient, elevation, aspect, mean annual precipitation, lithology, land use, and terrain roughness are the predictor variables used to determine the dependent variable of occurrence or non-occurrence of landslides within an individual grid cell. The results illustrate the importance of terrain roughness and soil type as key factors within the model — using only these two variables the analysis returned a significance level of 89.4%. The results obtained from the model within the GIS were then used to produce a map of relative landslide susceptibility.     

The geological evolution of southern McMurdo Sound — new evidence from a high-resolution aeromagnetic survey

Magnetic anomaly data are presented from a new helicopter-borne high-resolution aeromagnetic survey in southern McMurdo Sound. Anomaly data have been acquired at a common 305 m elevation above the McMurdo and southern McMurdo ice shelves and draped over the volcanic islands that pin them. The resulting anomaly patterns provide a significant advance in the understanding of the rift related geology beneath the floating ice shelves. More extensive Erebus Volcanic Province (McMurdo Volcanic Group) rocks are indicated along with a significant blanket of glaci-volcaniclastic sediment on the seafloor between the volcanic islands in southern McMurdo Sound. These glaci-volcaniclastic sediments are inferred to originate from former grounding of the southern McMurdo Ice Shelf as a marine ice sheet. A strong N–S fabric is also observed in the anomaly data suggesting that the rift structure observed in the Victoria Land basin persists to the south beneath the McMurdo and southern McMurdo ice shelves. W–N–W transfer faults identified within the Transantarctic Mountain rift flank to the west are not obvious in the aeromagnetic data set, implying that the 'Discovery Accommodation Zone' may be restricted to the region between a southward extension of the range bounding fault that marks the limit of the Victoria Land Basin and the right lateral offset in the Transantarctic Mountain front in southern Victoria Land.     

Geomorphic constraints on the active tectonics of southern Taiwan

Taiwan is a region of rapid active tectonics, yet the study of the tectonic processes that shape the interior of the island is difficult due to the high rates of erosion and dense vegetation. We use digital topography to look for indications of active deformation preserved in the local geomorphology. In particular, anomalies in the regional pattern of drainage are used to infer zones of enhanced tectonic activity. The apparent anticlockwise rotation of major river systems in plan view indicates the presence of a diffuse zone of left-lateral shear running down the southeastern side of Taiwan. Asymmetries in the catchments of individual drainage basins show the influence of varying rates of uplift across southern Taiwan, with the most rapid uplift close to Taitung at the indentation point of the Luzon arc with the Chinese continental margin. Our interpretations, though based predominantly on remote-sensing observations, are consistent with the available field evidence. This study demonstrates the usefulness of drainage basins as tectonic markers in the quantification of regional strain and uplift, which may have wider applicability in other deforming parts of the world.     

Estimation of Elastic Stress-Related Properties of Bottom Sediments via the Inversion of Very- and Ultra-High-Resolution Seismic Data

Izvestiya, Atmospheric and Oceanic Physics - This paper provides an overview of several seismic inversion approaches and their application to very- and ultra-high-resolution marine seismic...