Previous studies of channel morphological change have often relied upon sparse spatial and temporal data-sets, resulting in a degree of uncertainty in their conclusions. Furthermore, previous methodologies have been unable to quantify small-scale changes in channels composed of sand and fine gravel due to inadequate data density. This study reports the use of a high-resolution 3D laser scanner (LMS-Z210) in the assessment of erosion and deposition volumes in the proglacial zone of Glacier du Ferpècle and Mont Miné, Switzerland. Highresolution (> > > > >500 points/m 2 ) data obtained across a 5881 m 2 area of braid plain during the early part of the melt-water season permitted digital elevation models (DEMs) of bar surfaces and channels to be produced. The approach negates the need for complex surface interpolation algorithms required in surveys with lower point density, e.g. those obtained from global positioning systems or total stations. Furthermore, the technique has the advantage of being able to cover a large area over a comparatively short time period. Laser scanner returns revealed high vertical precision, ± ± ± ± ±0·02 m, for dry bar surfaces; however, submerged areas (< < < < <0·2 m depth) returned lower precision, with a range of − − − − −0·15 to + + + + +0·06 m. To account for this, different levels of detection (LoD) were applied to the dry and wet parts of the study reach during DEM subtraction. Subtraction of successive DEMs revealed two short depositional episodes over the ten-day study, with erosion dominating in between. Three episodes of avulsion were identified, two of which appeared to be triggered by constriction avulsion, whilst the other was initiated by bar-edge erosion. Transient lobes and sediment sheets could also be identified at the downstream end of the reach, as could lobe progradation. Relatively minor, but common, changes in channel morphology could also be detected, such as bar edge accretion, bank erosion and chute development. In an analysis of the effects of survey frequency upon volumes calculated following DEM subtraction, daily surveys were found to increase erosion volumes by 67 per cent and deposition volumes by 14 per cent when compared with an 8-day survey interval.

Advances in spatial analytical software allow digital elevation models (DEMs) to be produced which accurately represent landform surface variability and offer an important opportunity to measure and monitor morphological change and sediment transfer across a variety of spatial scales. Many of the techniques presently employed (aerial LIDAR, EDM theodolites, GPS, photogrammetry) suffer coverage or resolution limitations resulting in a trade-off between spatial coverage and morphologic detail captured. This issue is particularly important when rates of spatial and temporal change are considered for fluvial systems. This paper describes the field and processing techniques required for oblique laser scanning to acquire 0·01 m resolution digital elevation data of an upland reach of the River Wharfe in the UK. The study site is variable with rapidly changing morphology, diverse vegetation and the presence of water, and these are evaluated with respect to laser data accuracy. Scan location, frequency and distance are discussed with reference to survey accuracy and efficiency, and a field protocol is proposed. Scan data cloud merging was achieved with a high degree of precision (sub-centimetre) and positional data are shown to be very accurate for exposed surfaces. Vegetation and water decrease the accuracy, as the laser pulse is often prevented from reaching the ground surface or is not returned.

Abstract-A terrestrial laser scanner (TLS) was used to measure canopy directional gap fraction distribution in forest stands in the Swiss National Park, eastern Switzerland. A scanner model was derived to determine the expected number of laser shots in all directions, and these data were compared with the measured number of laser hits to determine directional gap fraction at eight sampling points. Directional gap fraction distributions were determined from digital hemispherical photographs recorded at the same sampling locations in the forest, and these data were compared with distributions computed from the laser scanner data. The results showed that the measured directional gap fraction distributions were similar for both hemispherical photography and TLS data with a high degree of precision in the area of overlap of orthogonal laser scans. Analysis of hemispherical photography to determine canopy gap fraction normally requires some manual data processing; laser scanners offer semiautomatic measurement of directional gap fraction distribution plus additional threedimensional information about tree height, gap size, and foliage distributions.Index Terms-Directional gap fraction, forest structure, hemispherical photography, terrestrial laser scanner (TLS).

1. The severe and early destruction and fragmentation of woodland habitats due to human activities is thought to have been a leading factor in the extirpation from Britain of several large, forest-dependent mammal species, such as the Eurasian lynx Lynx lynx. However, during the 20th century, Scotland in particular has experienced rapid, large-scale reafforestation. In order to assess if this reafforestation has been sufficient to permit the potential restoration of extirpated forest mammal species with large spatial requirements, a Geographical Information System (GIS) analysis of potential habitat of one species, the Eurasian lynx, was performed for the Scottish mainland. 2.A rule-based analysis, incorporating data and expert opinion from Switzerland, an environmentally similar area where lynx now occur, was used to identify patches of suitable lynx habitat in Scotland. A connectivity analysis was used to investigate whether and how these patches are connected to form larger interconnected networks of potential lynx habitat that would allow lynx to sufficiently interact with one another to form a single interbreeding population. 3. Scotland has over 20 000 km 2 of suitable lynx habitat split into two main networks of interconnected patches: the Highlands (c. 15 000 km 2 ) and the Southern Uplands (c. 5000 km 2 ). A further 800 km 2 of potential habitat, contiguous with the Southern Uplands lynx habitat network, lies across the border in England. Although connectivity between the Highlands and Southern Uplands networks is currently weak, the implementation of measures to mitigate the barrier effects of busy roads in central Scotland could facilitate the movement of lynx between the two areas. 4. Based on the availability of prey resources, Scotland could support around 400 adult and subadult lynx in the Highlands and around 50 in the Southern Uplands. A Scottish population of this size would be the fourth largest lynx population in Europe considering current population estimates.

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The presence of Eurasian lynx as a former native species in Britain during the Holocene is known from bones recovered from several sites. AMS radiocarbon dating of lynx bone recovered from two sites in the Craven area of northern England gave 1842 AE 35 14 C yr BP and 1550 AE 24 14 C yr BP, together representing the youngest dates for lynx from England, and in the case of the latter, the youngest for Britain as a whole. These dates support the view that the game animal whose occurrence in the nearby Lake District is described in the early 7th century Cumbric text Pais Dinogad, and whose translation to date has been problematic, is a lynx. The occurrence of lynx in early medieval Britain shows that earlier periods of climate change, previously blamed for the species' extinction in Britain, were not responsible. Instead, anthropogenic factors such as severe deforestation, declining deer populations, and persecution, are likely to have caused the extirpation of lynx in Britain. Consequently, the lynx qualifies as a candidate for reintroduction. Large-scale reafforestation, the growth of deer populations, and more positive attitudes towards carnivores in modern society, could permit the restoration of lynx to Britain, particularly in Scotland.

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