EARTH SURFACE PROCESSES AND LANDFORMS, VOL. 9, 305-306 (1984)

THE DAVID LINTON AWARD

RECIPIENTS

Ralph A. Bagnold

Ralph Bagnold took a month’s leave from the British Army in Egypt in 1929 to travel into the western desert of Egypt by motor vehicle with a group of fellow officers. The use of mechanical transport for exploration was criticized later by some attending the Royal Geographical Society meetings at which Bagnold spoke. He countered his critics by pointing out that the motor car made it possible to bring more scientists to the field more quickly and thus accelerated the accumulation of knowledge about deserts. Bagnold‘s desert journeys, reported in articles in the Geographical Journal, and a book Libyan Sands (1935), aroused his interest in the problems of sand transport by wind. Careful particle size analyses helped him to develop a theory of sand movement which was later tested with a wind tunnel in the engineering section of the City and Guilds College in London. This work gained him the Founder’s Medal of the Royal Geographical Society in 1935 and culminated in the book The Physics of Blown Sand and Desert Dunes (1941).

Bagnold noted that the wind needed to initiate lift or shear movement of particles had a greater velocity than that required to sustain movement. He distinguished the former as the fluid threshold velocity and the second as

the impact threshold velocity for grains of a particular size. His recognition of the need for assessment of critical thresholds is apparent in his calculations of the theoret- ical possibility of sand drift in his comments on J. A. Steers’ paper on the Culbin Sands and Burghead Bay (Geographical Journal, 1937). Bagnold also made the pertinent observation that light winds erode, or elongate a sand patch or dune, while strong winds build it up. The interaction between the sand bed of the desert surface and the particles in suspension in the air above it was seen to be part of a turbulent continuum in which the supply of particles and the detachment forces were delicately balanced.

When his book on blown sand was published, Bagnold was back in the desert as commander of the Long Range Desert Group which operated in the eastern Sahara behind Italian and German lines during World War 11. Here the navigational skills, including the Bagnold sun compass, developed during the earlier journeys, became of immense practical significance. Yet, characteristically, when he reported to the Royal Geographical Society in 1945 on the early days of the Long Range Desert Group, Bagnold again showed his unabated scientific curiosity and urged his listeners to enter a new phase of scientific desert exploration.

Bagnold’s interests in the phenomena of sediment transport then shifted to movement by water. A new series of flume experiments was reported in a series of papers to the Royal Society and the Institution of Civil Engineers in the 1950s. These were augmented by contri- butions to the Professional Papers of the United States Geological Survey when Bagnold spent a period with the Survey a few years later. From this work came a new, simpler approach to the study of sediment movement in rivers. Bagnold saw the fluid stream of a river as a transporting machine expending power to do work. Using concepts of bed shear stress and bedload transport rate, Bagnold revealed the discontinuities in the transport process associated with the formation of secondary bedforms (dunes) which dissipate flow energy in form roughness. These ideas have been refined in a series of papers in the last 20 years.

Throughout his career, Bagnold has emphasised the need to think along fresh lines about old problems. He has combined field observation with laboratory experiment, deduction from first principles with field testing. As he

0 1984 by John Wiley & Sons, Ltd.

306 THE DAVID LINTON AWARD

said when accepting the Founder’s Medal of the Royal Geographical Society in 1935:

Today, Ralph Bagnold, worthy recipient of the first David Linton Memorial Award, still challenges earth - .

scientists to take a fresh look at old problems, to clear their minds of old ways of thinking, and to think logically and clearly. He has shown just how fruitful and product- ive such a process can be.

As knowledge becomes more specialized there will always be new things to be found by those who know what to look for, even in ground that has already been gone over. The only trouble is to persuade the specialist to leave his books and lectures and come out into the field. IAN DOUGLAS

Stanley A. Schumm

Professor Schumm was presented with the David Linton award of the BGRG at the meeting in Birmingham in September 1982-a meeting during which Stan gave an excellent lecture in his usual relaxed, delightfully en- tertaining and thought-provoking style. Without doubt research by Professor Schumm has been one of the most substantial influences exerted upon members of the BGRG since 1960.

In 1955 Professor Schumm obtained his Ph.D. from Columbia University as one of the influential products of the Strahler school, and the work on drainage systems at Perth Amboy has become classic for a number of contributions that it made. Twelve years experience as a geologist with the US. Geological Survey preceded his appointment at Colorado State University in 1967. In a distinguished publication record of over 100 items it is not easy to separate the most notable contributions but it is evident that several research strands have been particu- larly influential. Work on sediment yield in relation to mean annual precipitation was subsequently developed to important ideas on palaeohydrology, to erosion rates in relation to orogeny and related to the geologic record. A further theme has been the investigation of alluvial stream channel morphology in relation to sediment type and it is notable that a classification of alluvial channels proposed as tentative in 1963 has already survived unchallenged for twenty years and has been applied to fluvial palaeochan-

nels. River channel change has been studied in a number of distinguished research investigations extending from channel widening and flood plain construction along the Cimarron to the more recent work on the Mississippi. Such studies of channel change were important not only because they pioneered methods of investigation and demonstrated the significance of results, but also pro- vided the basis for extremely significant conceptual advances in the understanding of river metamorphosis. Slope processes have also been the subject of important research advances made by Professor Schumm and the graph of gullied and ungullied valley floors in the Piceance basin is a classic which was important for the elegant simplicity of the contribution made. A further research theme has been the experimental studies of drainage basins which emerged from the rainfall erosion facility developed by Professor Schumm and collabor- ators at Colorado State and have led to an enhanced understanding of the mechanisms of drainage basin processes.

Contributions from these several themes add up to an outstanding impact on geomorphology but there has been a further level of contribution which has arisen from the generalizations drawn from each theme, from the interac- tions between the themes, and from their application to the whole of geomorphology. Thus we have appreciated the vision of time, space and causality in geomorphology, the insight of thresholds, of complex response, and erosion, and the promotion of applications of geomor- phological research. Many of Professor Schumm’s ideas are encapsulated in his book The Fluvial System pub- lished in 1977 and in that and his other books, including the Physical Geography of W M . Davis, and in his research papers Professor Schumm has developed a writing style that is truly stimulating and provides vision on geomorphology that has exerted a very great positive influence. He has already received a number of awards including the Kirk Bryan award of the Geological Society of America for his book the Fluvial System and the David Linton award is appropriate for someone who has already achieved great standing not only in fluvial geomorphology but in geomorphology as a whole and all geomorphologists will continue to welcome the writings from the pen of a truly innovative and outstanding leader in the field.

K. J. GREGORY Southampton