EARTH SURFACE PROCESSES AND LANDFORMS, VOL 22, 799–816 (1997) CCC 0197-9337/97/090799–18 $17.50  1997 by John Wiley & Sons, Ltd. EROSION PROCESSES AND LANDFORM EVOLUTION ON AGRICULTURAL LAND – NEW PERSPECTIVES FROM CAESIUM-137 MEASUREMENTS AND TOPOGRAPHIC-BASED EROSION MODELLING TIMOTHY A. QUINE 1 , GERARD GOVERS 2 , DESMOND E. WALLING 1 , XINBAO ZHANG 3 , PHILIPPE J. J. DESMET 4 , YUSHENG ZHANG 1 AND KAREL VANDAELE 4 1 Department of Geography, University of Exeter, Amory Building, Rennes Drive, Exeter, Devon, EX4 4RJ, UK 2 National Fund for Scientific Research, Laboratory for Experimental Geomorphology, Catholic University of Leuven, 16 Redingenstraat, Leuven, Belgium 3 Institute of Mountain Disasters and Environment, Chinese Academy of Sciences, Chengdu, Sichuan Province, China; also at the Department of Geography, University of Exeter 4 Laboratory for Experimental Geomorphology, Catholic University of Leuven, 16 Redingenstraat, Leuven, Belgium Received 29 February 1996; Revised 20 August 1996; Accepted 25 September 1996 ABSTRACT Despite growing interest in soil erosion on agricultural land, relatively little attention has been paid to the influence of erosion processes on the pattern of contemporary landform evolution. This in part reflects the problems associated with up- scaling the results of short-term process studies to temporal and spatial scales relevant to the study of landform evolution. This paper presents a new approach to examining the influence of erosion processes on landform evolution on agricultural land which employs: caesium-137 ( 137 Cs) measurements to provide medium-term (c. 40 years) estimates of rates of landform change; experimental data and a topographic-based model to simulate soil redistribution by tillage; a mass- balance model of 137 Cs redistribution to separate the water erosion and tillage components of the 137 Cs ‘signatures’; and field observations of water erosion for validation. This approach is used to examine the relative importance of water erosion and tillage processes for contemporary landform evolution at contrasting sites near Leuven, in Belgium, and near Yanan, in Shaanxi Province, China. This application of the approach provides good agreement between the derived water erosion rates and field observations, and hitherto unobtainable insights into medium-term patterns and rates of contemporary landform evolution. At Huldenberg in Belgium, despite rill incision of slope concavities and ephemeral gully incision of the valley floor, contemporary landform evolution is dominated by infilling of slope and valley concavities (rates >0·5 mm a -1 ) and gradual lowering of slope angles as a result of tillage. In contrast, at Ansai (near Yanan) the slope is characterized by increase in slope angle over most of the length, recession of the steepest section at a rate >5 mm a -1 and by increasing planform curvature. At this site, contemporary landform evolution is dominated by water erosion. The constraints on the approach are examined, with particular attention being given to limitations on extrapolation of the results and to the sensitivity of the models to parameter variation.  1997 by John Wiley & Sons, Ltd. Earth surf. process. landforms, 22, 799–816 (1997) No. of figures: 7 No. of tables: 5 No. of refs: 33 KEY WORDS: landform evolution; caesium-137; soil erosion; erosion modelling; water erosion; tillage erosion; China; Loess Plateau; Belgium LANDFORM AND PROCESS ON AGRICULTURAL LAND Field, laboratory and modelling studies undertaken over the last two decades have brought about significant progress in the understanding of erosion processes on agricultural land (Kirkby and Morgan, 1980; Boardman et al., 1989; Wicherek, 1993). A number of studies have addressed the relationship between process and landform by examining landform or topographic controls on water erosion processes (Evans and Cook, 1986; Martz and De Jong, 1987; Loughran et al., 1989; Govers, 1991; Martz, 1992; Auzet et al., 1993). Relatively little attention has, however, been given to the converse aspect of the relationship, namely the influence of erosion processes on the pattern of contemporary landform evolution on agricultural land. This reflects the difficulty of up-scaling * Correspondence to: T. A. Quine Contract grant sponsor: ODA Contract grant sponsor: Royal Society Contract grant sponsor: British Council Contract grant sponsor: University of Exeter Research Fund.