Erosion and Nutrient Loss on Sloping Land under Intense Cultivation in Southern Vietnam

To help improve the well‐being of the local people, a joint Vietnamese‐UK team set out to establish a way of estimating soil and nutrient losses under different land management scenarios, using field data extrapolated through remote sensing and GIS, to obtain catchment‐wide estimates of the impact of land cover change. Immigration from remote provinces to the Dong Phu District of Binh Phuóc Province, about 120 km north of Ho Chi Minh City, has led to disruption of soil surface stability on easily eroded clayey sandstones, creating rapid nutrient depletion that affects crop yields and siltation in the channel of the Rach Rat river downstream. The poor farmers of the areas see crop yields drop dramatically after two or three years of cultivation due to the fertility decline. Soil loss varies dramatically between wet season and dry season and with ground cover. Erosion bridge measurements showed a mean loss of 85.2 t ha^?1 y^?1 under cassava saplings with cashew nuts, 43.3 t ha^?1 y^?1 on uncultivated land and 41.7 t ha^?1 y^?1 under mature cassava. The rates of erosion were higher than those reported in many other parts of Vietnam, reflecting the high erodibility of the friable sandy soils on the steep side‐slopes of the Rach Rat catchment. However, although the actual measurements provide better soil loss data than estimates based on the parameters of soil loss equations, a large number of measurement sites is needed to provide adequate coverage of the crop and slope combinations in this dissected terrain for good prediction using GIS and remote sensing.     

UVB RADIATION DISTRIBUTION IN CANADA DURING 1992 AND 1993

One of the steps leading to an assessment of the biological significance of ozone destruction is to determine the biologically effective ultraviolet radiation (UVB) distribution. The objective of this study is to describe and analyze broadband UVB radiation at 24 locations across Canada, during the period from July 1992 through December 1993. This is the first study of broadband UVB measurements involving such a large number of UVB measuring instruments. Quantitative characteristics and statistical analysis of the surface UVB radiation in Canada with respect to ozone amount, as well as cloudiness, are presented. The results indicate higher UVB irradiance in the second half of 1992, compared with the same period in 1993. Among all the locations, Toronto received the greatest dose of UVB radiation in 1993. Excluding Yellowknife, due to its northernmost location (larger zenith angles), Ste-Agathe, Quebec received the smallest dose. Unusually high UVB fluxes were found to occur in March 1993 over eastern Canada. A study of the correlation of UVB radiation with total ozone and cloud opacity was carried out for most of the locations. The results suggest that other meteorological parameters have a significant impact on the ultraviolet levels.     

THE JUDICIOUS SELECTION AND PRESERVATION OF TUFF AND TRAVERTINE BUILDING STONE IN ANCIENT ROME*

The Republican and early Imperial monuments of Rome are, for the most part, built of tuffs quarried from at least seven pyroclastic deposits erupted from nearby Monti Sabatini and Alban Hills volcanoes. Remarks by Vitruvius (2.7.1–5), field observations of the monuments, and petrographic and rock testing studies of samples from Roman quarries demonstrate that Roman builders developed a good knowledge of the diverse material properties of the tuffs over centuries of use and exposure. Measurements of compressive strength, specific gravity, water absorption and adsorption of water vapour confirm that the petrographic characteristics of each tuff lithology strongly influence its strength and durability. Early construction utilized weakly durable, soft or vitric tuffs such as Tufo del Palatino or Tufo Giallo della Via Tiberina that are susceptible to decay, as at Temple C (290 bc ) of the Largo Argentina Sacred Area. Late Republican structures, such as the Temple of Portunus (80–90 bc ), employed somewhat durable, vitric–lithic Tufo Lionato reinforced with travertine, a durable limestone quarried near Tivoli. Roman builders selected the material properties of the tuffs to advantage for specific structural elements within large public monuments of the first century bc and the first century ad , as at the tabernae of the Forum of Caesar (46 bc ), where an upper storey of lightweight Tufo Lionato is supported by robust, lithic–crystal Lapis Gabinus pillars and flat arches reinforced with travertine. The tuffs are not very durable building stones; Romans preserved them with protective stucco, and travertine and marble cladding. Their high water intake, coupled with direct exposure to rain, daily fluctuations in relative humidity and urban weathering at present makes them especially vulnerable to decay.     

FURTHER STUDIES IN THE COMPOSITIONAL VARIABILITY OF COLOURLESS ROMANO‐BRITISH VESSEL GLASS*

Previous studies of colourless Romano‐British vessel glasses have suggested that, regardless of vessel type, they show considerable compositional homogeneity. Intriguing differences in variability (as opposed to mean composition) have, however, also emerged. This paper reports on a compositional study of 243 vessels, that is larger and more carefully controlled than in previous studies of this kind. Unexpected compositional differences have been found both between and within the four vessel types studied. We discuss the implications of these results in the context of different models that have been proposed for glass‐making and glass‐working in the Roman world.     

GLACIATION OF BONAVISTA PENINSULA, NORTHEAST NEWFOUNDLAND

Over Bonavista Peninsula, in northeast Newfoundland, ice-flow directional indicators reveal two styles of glaciation. The inner part was glaciated by ice of the Newfoundland Ice Cap, flowing northeast but drawn down strongly into deep channels in Bonavista and Trinity bays and basally deflected northward by a line of hills bisecting the peninsula. The outer peninsula was almost completely glaciated by the contiguous, dynamically independent Bonavista Ice Divide, with coastward flow. Near the northeast extremity a low plateau, mantled with blockfield and bearing no obvious traces of glaciation, is flanked by a subdued end moraine. The moraine is argued to represent the local entire Wisconsinan glaciation limit. Evidence from soil development on the moraine and elevations of emerged post-glacial shore features, as well as from comparison with glacial history in nearby areas, is used to argue a late Wisconsinan (pre-12,000–13,000 BP) age for the later part of glaciation. Evidence of widespread till deposition far offshore can be harmonized with evidence of incomplete Wisconsinan glaciation onshore by postulating persistent discharge of inland ice through the deep, compound fiord basins that flank Bonavista and other east Newfoundland peninsulas Les indicateurs du passage des glaciers dans la péninsule de Bonavista située au nord-est de Terre-Neuve signalent l'oeuvre de deux styles de glaciation. La Calotte Glaciaire de Terre-Neuve recouvrait tout I'intérieur de la Péninsule; se déplaçantvers le nord-est, elle était forcee de suivre par les baies profondes de Bonavista et de Trinité, et détournée à sa base en direction du nord par les collines qui franchissent la péninsule du nordau sud. Pour sa part, I'extérieur de la péninsule gisait entièrement sous le Diviseur Glaciaire Bonavista, qui tout en étant contigu obéissait à une dynamique indépendante et s'écoulait en direction des côtes. A I'extrémité nord-est de la pénin sule, sous un manteau de blocs rocheux, se trouve un bas plateau qui ne porte aucune trace de glaciation et qui est bordé d'une fine moraine terminale. Selon l'argument proposé, cette moraine représente en cet endroit la limite extrême des glaciers du Wisconsin. Des indices provenant de la formation des sols sur cette moraine et des hauteurs atteintes par la mer postglaciaire, de même qu'une comparaison avec l'histoire des glaciations dans les zones environnantes, permettent d'avancer que la fin de la dernière glaciation remonte à celle du Wisconsin (avant 12 000 à 13 000 ans AP). Des liens existent entre les dépots très répandus de till, loin au large des côtes, et les indices d'une glaciation incomplète durant le Wisconsin sur ces côtes, dans la mesure où l'on postule qu'il y eut une décharge soutenue de glace en provenance de l'intérieur, le long des fiords profonds et complexes qui bordent la peninsule de Bonavista de même que d'autres péninsules de Terre-Neuve.     

Caravan Parks and the AprWMay 1988 New South Wales Floods

Caravan parks are an important component of the tourist industry. They serve as the dormitory and the focal point for the immediate environs at places of interest. This paper investigates the characteristics and the occupancy of parks which were inundaled by water during the April/May floods of 1988 in New South Wales. It looks at the number of people at risk, and the appropriateness of caravan parks occupying land liable to flood. This form of accommodation offers people a great flexibility in their holidaying patterns but when long-term or permanent caravans are concentrated in parks on floodprone land they pose a number of problems. In addition to human elements such as personal property damage and social disruption, substantial disaster relief payments from public funds are required. It appears quite inappropriate 10 allow floodprone caravan parks to have sites occupied on a long-term basis.