Report: Carry on SamplingAuthor(s): Bruce WebbSource: Area, Vol. 14, No. 1 (1982), pp. 51-52Published by: The Royal Geographical Society (with the Institute of British Geographers)Stable URL: http://www.jstor.org/stable/20001775 .

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Carry on sampling

Report of the International Symposium on Erosion and Sediment Transport Measurement, Florence, 22-26 June 1981.

The elegant Sala Verde of the Palazzo dei Congressi, Florence provided a fitting setting for this International Symposium which was attended by more than 150 specialists from nearly 40 countries. The Symposium was organised jointly by the National Research Council of Italy and the Commission on Continental Erosion of the International Association of Hydrological Sciences, to provide a forum for the exchange of ideas, for the review of recent progress and for the definition of existing problems and research needs in the measurement of erosion and sediment transport.

One index of the success of the meeting in fulfilling these aims is provided by the large number and variety of papers submitted to the Symposium. These were pre-published, totalled over 60 contributions and ranged in subject matter from modifications of the Helley-Smith bed load sampler (R. L. Beschta) to the design of plot-sized rainfall simulators (W. H. Neibling et al.). The wide scope of papers was apparent in the environments monitored, which varied from tropical areas in East Java (T. E. Brabben) to seasonally frozen creeks in Eastern Canada (W. T. Dickinson) and from single mountain hillslopes (A. Takei et al.) to major lowland rivers (H. S. S. Singhal et al.); in the processes measured, which included bank erosion (C. R. Thorne), splash erosion (R. P. C. Morgan), debris flows (S. Okuda et al.), and suspended sediment transport in the surf zone (T. Basinski); and in the conditions encountered which fluctuated from low sediment concentrations of estuaries (M. L. Crickmore and C. J. Teal) to hyperconcentrations of debris flows (M. Hirano and M. Iwamoto). Equipment employed in individual studies varied from simple and low cost samplers (I. Becchi et al.) to very sophisticated installations such as the US Geological Survey Bed Load Transport Research Facility, Wyoming (W. W. Emmett). Contributions concerned with field (e.g. P. Billi et al.), laboratory (e.g. F. Raemy and M. Jaeggi) and theoretical (e.g. W. E. H. Culling) approaches were included in the programme which was also diversified by a film illustrating computer simulation techniques (G. Fleming and S. Fattorelli) and by a 'work print' depicting the collection and results of erosion measurements (I. A. Campbell).

Although individual contributions were diverse, the overall direction of the Symposium was not disparate, and sessions were structured into two main sections which were given further specific orientation by general lectures and invited papers. C. F. Nordin opened the section on 'Measurement of sediment transport' with a general review which considered suspended sediment and bedload discharge of rivers and highlighted four problem areas, including the effectiveness of sampling apparatus and techniques, the variable character of transport relation ships, the episodic nature of transport processes, and the indifferent quality of sediment data on a global basis. These and other themes were developed in following sessions which dealt with the

measurement of bedload transport, for example by basket samples (P. Engel and Y. Lam Lau), by tracer experiments (S. Cavazza) and by specially designed equipment (D. Zhou et al.), and which discussed techniques for continuous monitoring of suspended sediment concentrations, including conventional turbidity meters (D. C. Grobler and V. B. Weaver) and more recently developed and impressive applications of nuclear gauges (G. S. Tazioli; L. Raikoczi and B. Berke). Further sessions considered suspended sediment sampling apparatus, including recent developments in pump samplers (M. L. Crickmore and C. J. Teal), and suspended sediment sampling techniques designed to provide data for the modelling of mixing and transport phenomena (B. D611 et al.), for assessing environmental impacts (E. L. Pemberton) and for evaluation of land management strategies (K. T. Ryan). The reliability of sediment data was also discussed and the need to assess the accuracy and precision of past, present and future sediment load estimates (D. E. Walling and B. W. Webb; W. T. Dickinson) clearly emerged as

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52 Carry on sampling

did the necessity of long-term measurements for calculating average sediment yields (A. Rooseboom and G. W. Annandale).

Experimental approaches, including the investigation of shelter effects in the movement of streambed cobbles (L. B. Leopold and W. W. Emmett), were also covered in the first section of the meeting which was concluded by a discussion of ,he design of data collection programmes at a variety of scales from the continental level (J. W. Holeman), to the major system of the Yellow River (Y. Long and G. Xiong) and to smaller drainage basins (N. G. Bhowmik).

The second section of the Symposium was concerned with the 'Measurement of erosion ' and was introduced by G. Chisci who lucidly reviewed the interaction of field research and mathematical modelling in the study of upland erosion, and evaluated the advantages and disadvantages of modelling via conceptual, parametric and deterministic approaches. Subsequent sessions focused firstly on the measurement of rainfall erosivity and splash erosion, and consideration was given to the various, but not always consistent, direct and indirect

methods of evaluating the erosive power of rainfall (N. W. Hudson) and to the great variety of factors which influence erosion by running water in the tropics (R. Lal). Problems of controlling experimental conditions were prominent in a session dealing with rainfall simulators and laboratory studies of erosion, where an alarming amount of variation in absolute and relative results from rainulators of different design was reported (R. B. Bryan), and the difficulties of scaling laboratory plots were discussed (J. De Ploey). The continuing popularity of erosion plot studies was clear from several contributions on their use (e.g. E. Caroni and D. Tropeano), although the importance of employing field plots of a suitably large size was made clear from work in the loess region of China (J. Mou). The usefulness of this technique in erosion studies was well demonstrated by the results from the Sde Boqer experimental site in the northern Negev Desert (A. Yair and H. Lavee) which have clearly indicated the influence of biological activity on the spatial variation of sediment sources on arid hillslopes. Field measurements at different scales may be particularly instructive as demonstrated by catchment yield, erosion plot and erosion pin studies of sediment flux on hillslopes in Sierra Leone (A. C. Millington). The section on erosion measurement was appropriately concluded by a review of the techniques used in more than 60 research centres located throughout the world (I. Becchi and P. Tacconi).

A number of trends and themes common to erosion and sediment transport measurement emerged from the two main parts of this Symposium, which included the increasing sophistication of monitoring and recording techniques (e.g. J. Colombani et al.; S. Okuda et al.) and a growing desire for standardisation of measuring procedures and instrumentation. The need for good quality long-term transport and erosion data, and the influence of scale of measurement on subsequent results were also recognised by several papers. In general discussion, delegates advocated that more attention should be given to biological and chemical processes, since it is rare that sediment erosion and transport are purely mechanical phenomena. Some participants also felt that more effort should be devoted by ' sediment specialists ' to processes of deposition and to the applied aspects of sediment mobilisation and conveyance. In spite of these particular omissions in the scope of the Florence Symposium, the meeting clearly reflected the vigorous international state of sediment studies and of considerable interest was the substantial number of contributions submitted by geographers from Britain and abroad. The paper sessions were supplemented by an enjoyable field trip to the Virginio and Pesciola experimental catchments in the Elsa Valley and the Vicarello experimental station in the Era Valley. In addition, a post-Symposium tour gave delegates a chance to visit the radioisotope stations for measuring sediment transport operated in Calabria by G. S. Tazioli, and the opportunity of seeing the landscape and cultural heritage of Southern Italy.

There can have been few international meetings so well organised and smoothly running as the Florence Symposium, and our Italian hosts at the University of Florence were particularly generous in their hospitality and also provided a most interesting social programme for delegates and accompanying persons, which culminated in a memorable seven-course banquet at the

Medici Villa of Artimino.

Bruce Webb University of Exeter

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