IDENTIFYING MORAINE SURFACES WITH SIMILAR HISTORIES USING LICHEN SIZE DISTRIBUTIONS AND THE U2 STATISTIC, SOUTHEAST ICELAND

Moraine ridges are commonly used to identify past glacier ice margins and so infer glacier mass balance changes in response to climatic variability. However, differences in the form of past ice margins and post-depositional modification of moraine surfaces can complicate these geomorphic records. As a result, simple relationships, such as distance from current ice margin, or linear alignments, may not necessarily indicate moraines deposited contemporaneously. These disturbances can also modify the size distribution of lichen populations, providing a distinctive signature for surfaces with similar histories and a means of identifying contemporaneous moraine surfaces. In this paper, statistical analysis of lichen size distributions is used to identify moraine surfaces with similar histories from complex suites of Little Ice Age moraine fragments in the proglacial areas of Skálafellsjökull (including Sultartungnajökull) and Heinabergsjökull, southeast Iceland. The analysis is based on a novel use of the goodness-of-fit statistic, Watson's U² which provides a measure of 'closeness' between two sample distributions. Moraine fragments with similar histories are identified using cluster analysis of the U² closeness values. The spatial pattern of the clustered moraines suggests three distinct phases of moraine deposition at Skálafellsjökull and Heinabergsjökull, four phases at Sultartungnajökull and a digitate planform margin at Heinabergsjökull. These spatial patterns are corroborated with tephrochronology. The success of the U² statistical analysis in identifying surfaces with similar histories using lichen size distributions suggests that the technique may be useful in augmenting lichenometric surface dating as well as differentiating between other surfaces that support lichen populations, such as rock avalanche deposits.     

Integrating GIS and spatial data analysis: problems and possibilities

Abstract

This article is an agreed summary of a workshop held in Sheffield between 18-20 March 1991. The focus here is on three of the themes of the workshop: the mutual benefits of closer links between geographical information systems (GIS) and the methods of spatial data analysis (SDA); the specific areas of SDA that should be linked with GIS; how the linkage should be made in practice. Directions for future research are also reviewed. The emphasis throughout is on statistical SDA and principally from the perspective of human rather than physical geography.     

Assessing participatory GIS for community-based natural resource management: claiming community forests in Cameroon

This paper critically reviews and analyses participatory GIS (PGIS) and participatory mapping applications within participatory spatial planning for community-based natural resource management in developing countries. There is an often implicit assumption that PGIS use is effective, in that it meets content needs, satisfies underlying local stakeholder interests and therefore is a tool for better governance. The analytical framework looks at participatory spatial planning performance with respect to key dimensions of governance, especially the intensity of community participation and empowerment, equity within communities and between 'governed' and 'governing', respect for indigenous knowledge, rights, ownership, legitimacy, and effectiveness. Specific development focus is given by a case study using participatory mapping and PGIS in community forest legitimization, planning and management in Tinto, Cameroon. 'Good governance' criteria are applied ex-post to the implementation procedures, the geo-information outputs, and the longer-term outcomes of the PGIS processes. Impacts of incorporating PGIS were examined in terms of the types and degrees of participation in the process; access to, and the uses made of, the geographic information; whether the information outputs met stakeholders' requirements; and the overall changes in equity and empowerment in the community. It was found that PGIS/participatory mapping processes contributed – positively, though not comprehensively – to good governance, by improving dialogue, redistributing resource access and control rights – though not always equitably – legitimizing and using local knowledge, exposing local stakeholders to geospatial analysis, and creating some actor empowerment through training. PGIS promoted empowerment by supporting community members' participation in decision-making and actions, and by enabling land use planning decisions beyond community forestry itself.     

Sedimentary model for intertidal mudflat channels, with examples from the Solway Firth, Scotland

Intertidal mudflat channels (gullies) in the Solway Firth, Scotland possess width/depth ratios similar to meandering rivers. Most channels deeper than 1 m show cut-bank slides, but narrow, deep channels also have rotational slides on the point-bar slopes. The channels display two types of point-bar. The first, associated with gently curved meanders, is sigmoidal in profile. The second, associated with tight meander bends, possesses a pronounced lower platform. The onset of flow separation in meander bends, a phenomenon which enhances cut-bank erosion and point-bar deposition, is a direct function of meander-bend tightness and Froude number. The effects of flow separation are greatest on tight meander bends at times of high velocity during late spring ebb and also during rainfall run-off at low tide. These events appear to be responsible for the growth of the point-bar platforms. A model, predicting the type of point-bar development to be expected in different channel meanders, is used to reconstruct the sedimentary history of active and fossil point-bars.     

THE NON‐PENNSYLVANIA TOWN: DIFFUSION OF URBAN PLAN FORMS IN THE AMERICAN WEST*

ABSTRACT. Wilbur Zelinsky's classic 1977 account of the Pennsylvania town as a cultural place type–the urban component of the nationally influential Pennsylvanian culture region–acknowledged that it was not exported intact across the successive western frontiers of the United States. But, aside from Edward Price's specialized study of courthouse squares, we know little that is systematic about how town‐planning ideas diffused across the continent. This investigation offers evidence from the Willamette Valley in Oregon of the eventual variety and geographical distribution of town‐platting conventions that developed in this Pacific Coast “destination’ setting and the possible provenance in the Ohio Valley of certain early Oregonian town‐plan features. The evidence raises questions about the resilience of town‐planning conventions in light of the distance carried, cultural time lags, and changing ideas about best practice and local suitability.     

A generic model for planar geographical objects

Abstract

The lack of a coherent theory underpinning geographical databases is a serious obstacle to research efforts in this field. This article attempts to construct part of such a theory, namely the formalization of the underlying object mode for geographical data whose spatial references are embedded in the plane. Questions of approximation and error analysis, while exposed and briefly discussed here, do not form a major part of the discussion. This work extends earlier work by giving a detailed construction of the classes and operations for spatial objects embedded in the plane. It goes on to provide an explicit link between this object model and its representation in computationally meaningful terms using classes of simplicial complexes and operations acting upon these classes.     

THE RESPONSE OF PARTIALLY DEBRIS‐COVERED VALLEY GLACIERS TO CLIMATE CHANGE: THE EXAMPLE OF THE PASTERZE GLACIER (AUSTRIA) IN THE PERIOD 1964 TO 2006

Long‐term observations of partly debris‐covered glaciers have allowed us to assess the impact of supra‐glacial debris on volumetric changes. In this paper, the behaviour of the partially debris‐covered, 3.6 km² tongue of Pasterze Glacier (47°05′N, 12°44′E) was studied in the context of ongoing climate changes. The right part of the glacier tongue is covered by a continuous supra‐glacial debris mantle with variable thicknesses (a few centimetres to about 1 m). For the period 1964–2000 three digital elevation models (1964, 1981, 2000) and related debris‐cover distributions were analysed. These datasets were compared with long‐term series of glaciological field data (displacement, elevation change, glacier terminus behaviour) from the 1960s to 2006. Differences between the debriscovered and the clean ice parts were emphasised. Results show that volumetric losses increased by 2.3 times between the periods 1964–1981 and 1981–2000 with significant regional variations at the glacier tongue. Such variations are controlled by the glacier emergence velocity pattern, existence and thickness of supra‐glacial debris, direct solar radiation, counter‐radiation from the valley sides and their changes over time. The downward‐increasing debris thickness is counteracting to a compensational stage against the common decrease of ablation with elevation. A continuous debris cover not less than 15 cm in thickness reduces ablation rates by 30–35%. No relationship exists between glacier retreat rates and summer air temperatures. Substantial and varying differences of the two different terminus parts occurred. Our findings clearly underline the importance of supra‐glacial debris on mass balance and glacier tongue morphology.