Progress in Physical Geography current issue

Progress in Physical Geography: retrospect and prospect 2009--10

Clifford, N. J. — Fri, 20 Nov 2009 04:03:15 PST

Synchronization of transport and supply in beach-dune interaction

Houser, C. — Fri, 20 Nov 2009 04:03:15 PST

This review considers the role of nearshore processes and morphological change as a flexible and dynamic constraint on the supply and transport of sediment between beach and dune. It is argued that the lack of information in this regard remains a central barrier to the development of a theory of beach-dune interaction that can be translated across scales and between field sites. Existing beach-dune models do not consider how and when sediment gets transferred to the backshore where it becomes available for transport by wind. Rather, existing models largely ascribe regional variations in dune morphology to fixed constraints on beach slope and sediment budget, without explicit recognition of processes involved. Recent (process-scale) transport studies have shown that the transfer of sediment is both spatially variable and temporally intermittent as a result of transport limitations across the beachface. While these studies have identified varied controls on sediment transport and exchange, there remains a limited capacity to predict the evolution of beach-dune systems, largely because the beachface tends to be viewed as a static transport surface without regard to supply or to the changing limits to transport. Following storm erosion, dune recovery first requires that the beach recovers through the onshore migration and welding of nearshore bars, followed by accretion in the backshore to create a supply of sediment for transport by the wind. The dependence of dune recovery on the synchronization of transport events with the recovery of sediment supply in the backshore creates a strong asymmetry in dune recovery that makes barrier island susceptible to widespread erosion and breaching if a change in the frequency or grouping of storm events is capable of resetting the bar system (offshore) before the next extreme storm.

Problems in remote sensing of landscapes and habitats

Wang, K., Franklin, S. E., Guo, X., He, Y., McDermid, G. J. — Fri, 20 Nov 2009 04:03:15 PST

Wildlife habitat mapping strongly supports applications in natural resource management, environmental conservation, impacts of anthropogenic activity, perturbed ecosystem restoration, species-at-risk recovery and species inventory. Remote sensing has long been identified as a feasible and effective technology for large-area habitat mapping. However, existing and future uncertainties in remote sensing will definitely have a significant effect on the relevant scientific research. This article attempts to identify the current challenges and opportunities in remote sensing for large-area wildlife habitat mapping, and accordingly provide possible solutions and directions for further research.

Advances in interferometric synthetic aperture radar (InSAR) in earth system science

Rott, H. — Fri, 20 Nov 2009 04:03:16 PST

During recent years, synthetic aperture radar (SAR) interferometry (InSAR) has become an important tool for precise measurements of the earth’s surface topography and deformation. This paper presents an overview on recent developments in InSAR applications, with emphasis on the use of satellite-borne sensors for applications in geoscience, topographic mapping, natural hazard monitoring and environmental research. InSAR measurement principles are briefly introduced. Recent results on the use of repeat-pass interferometry for mapping seismic and volcanic deformation, monitoring landslides and subsidence, and mapping glacier motion are described. Other InSAR applications introduced in the paper are: topographic mapping, retrieval of biogeophysical parameters on land surfaces, and measurements of water currents. Examples of interferometric products are shown for satellite-borne SAR systems operating at X-band, C-band and L-band radar frequencies. An outlook is provided on upcoming SAR systems which will spur further advances in InSAR techniques and applications.

The effects of land-use combinations on soil erosion: a case study in the Loess Plateau of China

Fu, B.-J., Wang, Y.-F., Lu, Y.-H., He, C.-S., Chen, L.-D., Song, C.-J. — Fri, 20 Nov 2009 04:03:16 PST

Land use is one of the key factors affecting soil erosion in the Loess Plateau of China. This paper examines soil erosion under different land uses and land-use combinations using ¹³⁷ Cs tracing in the Yangjuangou Catchment, a tributary of the Yan River in the Loess Plateau of Northern Shaanxi Province. The results show that the order of ¹³⁷Cs activity in different land uses decreases sequentially from mature forest to grass to young forest to orchard to terrace crop, indicating that the mature forests had the lowest erosion rates while the terraced cropland produced the highest erosion amount. The majority of ¹³⁷Cs is distributed in the top 0—10 cm of the soil layer. The ¹³⁷Cs activity in mature forest and grass soil is significantly higher than in other land uses. Three land-use combinations on the hillslope were selected to study the relationship between land-use combination and soil erosion. The mixtures of ‘grass (6 years old) + mature forest (25 years old) + grass (25 years old)’ and ‘grass (6 years old) + young forest (6 years old) + mature forest (25 years old) + grass (25 years old)’ are better for soil erosion control, lowering soil erosion amount by 42% compared with a land-use combination of ‘grass (6 years old) and shrub (6 years old)’. The results provide an important basis for optimizing land-use combinations to control soil erosion on slopes and may also result in important ecological benefits.

The endokarstic erosion of marble in cold climates: Corbel revisited

Faulkner, T. L. — Fri, 20 Nov 2009 04:03:16 PST

After the work of Jean Corbel in the 1950s, who compared karstification in the Scandinavian Caledonide marbles with that in sedimentary limestones in temperate and tropical regions, the understanding of underground limestone dissolution has developed considerably. Corbel concluded that ‘karstification proceeds much faster in a cold than in a warm climate’, based on the knowledge that the solubilities of both CO₂ and CaCO₃ increase with lower temperature, without realizing that because cave streams in Scandinavia rarely reach saturation this fact is not directly relevant. We now know that the dissolutional enlargement of inception channels in limestones proceeds commonly via a slow initial ‘pre-breakthrough’ laminar flow stage before conduits can enlarge chemically at maximum rates under turbulent flow conditions. Recent research has shown that the pre-breakthrough stage is speeded up at low temperatures, as occurs in cold climates now, and as occurred during the deglaciation of the Weichselian ice sheet in Scandinavia, especially under steep hydraulic gradients and, in many cases, despite the lower partial pressure of CO₂. Additionally, this whole stage might be bypassed if fractures created by deglacial seismicity were wide enough and short enough. After breakthrough, although limestone dissolution is slower in cold rather than warm climates, conduit enlargement still proceeds at a significant rate, provided the water remains unsaturated, and especially if high flow rates promote mechanical erosion. The exploration of large numbers of (short) caves in central Scandinavia shows that Corbel’s conclusion is partly true for the more recent geological past, because of the special conditions that apply during the Quaternary glacial cycles.

Topographic normalization of satellite imagery for image classification in northeast India

Reddy, M. B., Blah, B. — Fri, 20 Nov 2009 04:03:17 PST

IRS-LISS-III satellite imagery covering Nongkhyllem Wildlife Sanctuary area located within the Ri-Bhoi District of Meghalaya State, northeast India, was used for analysis of the landcover pattern and vegetation types occurring there. A maximum likelihood classifier was used to generate a supervised classification into land-cover types and the vegetation types within the forested area. The preparation of training data sets used thematic maps of the area, and knowledge accruing from extensive personal field visits. Sample field plots were located at 30 different places in the Sanctuary for classification accuracy assessment. The Normalized Difference Vegetation Index (NDVI) was also computed from LISS-III satellite imagery. A digital elevation model (DEM) of the Sanctuary was generated using a GIS. The DEM was used to test the hypothesis that its joint use with the satellite data would increase classification accuracy. This proved to be the case. Bivariate correlation analysis was performed between spectral and DEM variables to cross-check the results. In the example used, that of the rugged terrain in mountainous parts of northeast India, such integration of satellite land-cover data and DEM information appears to be a necessity in improved land-cover mapping for resource planning and utilization.

Hydrology: catchment vegetation and runoff

Peel, M. C. — Fri, 20 Nov 2009 04:03:17 PST

The interactions between catchment vegetation and runoff continue to be a staple area of hydrological research. Drawing mainly upon material published since 2002, this report briefly reviews progress in this area with specific reference to: (1) paired and single catchment studies; (2) top-down models; and (3) the likely impact of climate change. Results from a wider range of paired and single catchments studies are revealing the complex relationship between catchment vegetation and runoff and prompting a reassessment of the methodologies used to generalize this relationship. Vegetation appears to have a significant influence on runoff at small scales, which reduces to a second-order influence, relative to aridity, at larger scales. Top-down models of catchment behaviour generally reflect this second-order influence at the large scale. As vegetation responds to CO₂ enrichment under climate change, the magnitude and direction of associated changes in runoff remains uncertain. A key element in quantifying the hydrological impact of climate change is the relationship between catchment vegetation and runoff, which continues to be a productive area of research within hydrology.

Research resource review: Burek, C.V. and Prosser, C.D., editors 2008: The history of geoconservation. Bath: The Geological Society Publishing House. 320 pp. {pound}60 cloth. ISBN: 978 1 86239 254 0

Page, K. — Fri, 20 Nov 2009 04:03:17 PST

Research resource review: Pelletier, J.D. 2008: Quantitative modeling of Earth surface processes. Cambridge: Cambridge University Press. 304 pp. {pound}40 cloth. ISBN: 978 0 521 85597 6

Wainwright, J. — Fri, 20 Nov 2009 04:03:17 PST