- Email: [email protected]
The significance of fluvial archives in geomorphology
Geomorphology 33 Ž2000. 127–130
Editorial
The significance of fluvial archives in geomorphology
1. Some aspects of historical approaches and modern trends in fluvial research Rivers have always been considered as one of the most important geomorphic agents. Since the 1950s, fluvial research has concentrated on understanding contemporary fluvial processes, spearheaded by American researchers such as L. Leopold and S. Schumm. These studies, exemplified also by Binghamton Symposia ŽMorisawa, 1974; Rhodes and Williams, 1979., have advanced substantially our understanding of river behaviour and channel patterns. At the same time, European geomorphology was more under the influence of climatic geomorphology Že.g., Cailleux and Tricart, 1958; Budel, 1977., which considered the relationship between the larger-scale morphology initiated by rivers and changing climate conditions. Recently, these two approaches have been combined, substantially advancing the interpretation of fluvial morphology. These advances have been illustrated in a number of special volumes and international programmes ŽGregory, 1983; Starkel et al., 1991; Vandenberghe et al., 1994; Frenzel et al., 1995; Gregory et al., 1995.. As an unfortunate consequence of the convergence of process studies and climatic geomorphology, another important external control on fluvial systems, tectonic movements, has been widely neglected in fluvial geomorphology. The study of tectonic influences on rivers has been largely left to sedimentologists Že.g., Alexander and Leeder, 1990; Leeder, 1993; Leeder and Jackson, 1993. who concern themselves with tectonic impacts limited largely to ‘mega-forms’ Že.g., Summerfield, 1981; Bridges,
1990.. Recently, however, there has been renewed interest in the role of tectonics in fluvial system development. This change in outlook is a consequence of more detailed geodetic measurements; better insights into the magnitude and timing of tectonic devents; and most importantly, a growing cooperation between geomorphologists and tectonicians in many regions. This latter cooperation is exemplified by the NEESDI-program ŽNetherlands Environmental Earth System Dynamics Initiative., a national science foundation funded program where geomorphologists, geophysicists and tectonicians have been cooperating since 1977, in an attempt to better understand natural environmental processes. In the last decade, thanks to the growing awareness of environmental values, in general, and the recognition that river valleys occupy an essential part of the landscape, the appeal of natural rivers has been rediscovered and appreciated again. As a consequence, environmental managers are increasingly governed by the characteristics of the natural river system in the architectural design of the present-day valley landscape. Fluvial geomorphology has proven to be capable of bringing considerable insight into the complex relationships governing natural river systems. In the short term, use is made of the intrinsic characteristics and the evolution of rivers to explain gradual processes, but much is also contributed by the study of extreme events, like floods, which characterize more abrupt natural river behaviour Žillustrated for instance by the recent establishment of an IGU Study Group ‘Environmental Change and Extreme Hydrological Events’.. In such applications, however, it is also necessary to realize that the channel and valley properties Žlike valley
0169-555Xr00r$ - see front matter q 2000 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 9 - 5 5 5 X Ž 9 9 . 0 0 1 1 9 - 1
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Editorial
slope, river pattern, and river position within the valley. respond to the long-term effects of climate change and tectonic movements. Increasingly, computer modelling is being applied by fluvial geomorphologists. Theoretical modelling of slopes is relatively old ŽBakker and Le Heux, 1952., and sees continuing development by the research work of, for example, F. Anhert Že.g., Anhert, 1976. and M. Kirkby Že.g., Kirkby, 1978, 1993.. After the pioneering work by A.D. Howard Že.g., Howard, 1994; Howard et al., 1994. different kinds of fluvial models have been developed. Some of them tried to simulate the system as a whole with a few simple relations, and are often forced by external factors. Others tried to apply physical laws of sediment entrainment and transport, but are often restricted to small-scale channel processes Že.g., in Carling and Dawson, 1996.. River modelling is certainly a tedious job, because of the complexity of the system. However, it offers tremendous possibilities for sensitivity analysis in the understanding and application of past, present and future fluvial processes. Furthermore, any progress in modelling will need to be accompanied by detailed and reliable field data together with associated climatic and tectonic movement datasets. It seems that we face here only the beginning of a fascinating and challenging evolution in fluvial geomorphology.
2. The role of the Fluvial Archives Group (FLAG) in fluvial research The increasing interest in fluvial systems over the last decade has involved a wide range and growing number of disciplines including geomorphology, sedimentology, archaeology, ecology, engineering and planning. This multidisciplinary approach has led to a burgeoning of research concerned with the relationship between river behaviour and environmental change. Fluvial archives Že.g., sediments, morphology, historical maps, palaeoecology, etc.. preserve a tremendous source of information concerning the functioning and evolution of river systems. The study of each individual archive requires specialist expertise, but understanding the fluvial system benefits most from a combination of archives. The utility of each specific archive depends upon its spatial and
temporal scale, the age of the fluvial system and the basin characteristics as a whole. Furthermore, in order to appraise the evolution of the system, it is essential that all archives be dated accurately and reliably. It is the main aim of FLAG to foster the use of such archives in the investigation of fluvial systems. FLAG establishes a forum for the exchange of information and ideas and will facilitate accessibility to these wide and varied archives, by making data readily available through publication. Furthermore, foci for future researches are proposed resulting from problems identified in current researches. The latter may lead to the formulation strategies that can be used to facilitate joint ‘focused’ research initiatives. Two major research themes have been defined. The first theme is ‘Long terrestrial records’ which is concerned with fluvial archives that span the whole Quaternary. Within this theme, two specific foci are identified, namely: ‘global correlation of Late Cenozoic fluvial sequences’ and ‘fluvial activity and crustal instability’. The second theme is ‘Fluvial environments and processes’ within which two further foci are identified, namely: ‘fluvial response to rapid environmental change during the last interglacial–glacial cycle’ and ‘Holocene fluvial system response to frequent and rapid periods of environmental change — identification and modelling of forcing factors’. Although distinction is made between the various themes and foci, it is essential that each of these are integrated and applied in all relevant regions. These research themes are intended to link with IGU, INQUA and IGBP-PAGES programmes. FLAG was formed in 1996 as a research group of the British Quaternary Research Association for a fixed term of 3 years. FLAG has now moved on, and has established itself as an internationally oriented group with the same objectives. FLAG currently has over 160 members from 22 different countries Žhttp:rrqra.org.ukrFLAG..
3. Research results This issue of ‘Geomorphology’ presents a small selection of river studies, which illustrate the philos-
Editorial
ophy of FLAG research. They result mainly from a conference held in Arcen, The Netherlands in September 1997. These contributions show the relevance of different fluvial archives in the investigation of the above-mentioned research topics. The impact of climatic changes on river pattern as recorded in sediment sequences from the last glacial in eastern Germany is exemplified in a paper by Mol et al. Mol et al. suggest that the most important changes in fluvial activity take place at climatic transitions, but under the control of local conditions such as vegetation, supplied sediment and eventual permafrost. Tectonic influences at different scales and in different modes appear in several papers. A complicated pattern of block faulting and uplift in the Polish Sudeten Mountains during different periods of the Quaternary has provoked a complex drainage response expressed in diverse depositionr erosion rates and irregular valley slopes ŽKrzyszkowski et al... Maddy et al. adopt a simple and constant regional uplift to explain the Quaternary incision of the British rivers. This interpretation is discussed against other external driving mechanisms such as eustatic sea level fall and erosional isostasy. A welldocumented paper of northern French rivers by Antoine et al. is a good example of the combined influence of tectonic movements, climate and sealevel change. However, local characteristics like drainage basin size are shown to influence the response of individual rivers. Benito et al. describe the intrinsic response of Spanish rivers in the specific case of subsidence in the underlying karst bedrock resulting in the development of local terraces. Finally, a way of simulating valley evolution is reported by Veldkamp and van Dijke. This paper demonstrates in general how modelling may evaluate the production of fluvial archives, and in particular the nonlinear reaction of the river system to external controls. References Alexander, J., Leeder, M.R., 1990. Geomorphology and surface tilling in an active extensions basin, SW Montana, USA. Journal of the Geological Society of London 147, 461–467.
129
Anhert, F., 1976. Brief description of a comprehensive three-dimensional process-response model of landform development. Zeitschrift fur ¨ Geomorphologie, Supplement Band 25, 29–49. Bakker, J.P., Le Heux, J.W.N., 1952. A remarkable new geomorphological law. Proceedings of the Koninklijke Nederlandese Akademie van Wetenschappen, Series B 55, 399–410, 554– 571. Bridges, E.M., 1990. World Geomorphology. Cambridge Univ. Press, Cambridge. Budel, J., 1977. Klima-Geomorphologie. Gebr. Borntrager, Stuttgart. Cailleux, A., Tricart, J., 1958. Introduction a la geomorphologie climatique. Cours de Geomorphologie, Paris V. Carling, P.A., Dawson, M.R. ŽEds.., 1996. Advances in Fluvial Dynamics and Stratigraphy. Wiley, Chichester. Frenzel, B., Vandenberghe, J., Kasse, C., Bohncke, S. ŽEds.., 1995. Palaeoklimaforschung 14, 226 pp. European river activity as a function of climate changes during the Late Glacial and Early Holocene. ESF Project ‘European Palaeoclimate and Man’. Gregory, K. ŽEd.., 1983. Background to Palaeohydrology. Wiley, Chichester. Gregory, K., Starkel, L., Baker, V. ŽEds.., 1995. Global Palaeohydrology. Wiley, Chichester. Howard, A.D., 1994. A detachment-limited model of drainage basin evolution. Water Resources Research 30, 2261–2285. Howard, A.D., Dietrich, W.E., Seidl, M.A., 1994. Modelling fluvial erosion on regional to continental scales. Journal of Geophysical Research 99, 13971–13986. Kirkby, M.J. ŽEd.., 1978. Hillslope Hydrology. Wiley, Chichester. Kirkby, M.J., 1993. Network hydrology and geomorphology. In: Beven, K., Kirkby, M.J. ŽEds.., Channel Network Hydrology. Wiley, Chichester, pp. 1–11. Leeder, M.R., 1993. Tectonic controls upon drainage basin development, river channel migration and alluvial architecture: implications for hydrocarbon reservoir development and characterization. In: North, C.P., Prosser, D.J. ŽEds.., Characterization of Fluvial and Aeolian Reservoirs. Geological Society of London, Special Publication 73 pp. 7–22. Leeder, M.R., Jackson, J.A., 1993. The interaction between normal faulting and drainage in active extensional basins, with examples from the western United States and central Greece. Basin Research 5, 79–102. Morisawa, M. ŽEd.., 1974. Fluvial Geomorphology. SUNY, Binghamton Symposium, Geomorphology. Rhodes, D.D., Williams, G.P. ŽEds.., 1979. Adjustments of the Fluvial System. Alien & Unwin, Boston, Binghamton Symposium. Starkel, L., Gregory, K., Thornes, J. ŽEds.., 1991. Temperate Palaeohydrology. Wiley, Chichester. Summerfield, M., 1981. Macroscale geomorphology. Area 13, 3–8. Vandenberghe, J., Gibbard, P., Van den Berg, M. ŽEds.., 1994. Pleistocene river systems in Europe. Terra Nova 6 Ž5..
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Editorial
Jef Vandenberghe a, ) Centre for Geo-ecological Research, Faculty of Earth Sciences, Vrije UniÕersiteit, De Boelelaan 1085, 1081 HV Amsterdam, Netherlands E-mail address: [email protected] a
)
Corresponding author. Fax: q31-20-646-2457.
Darrel Maddy b Department of Geography, UniÕersity of Newcastle, Newcastle-upon-Tyne, NE1 7RU, UK. E-mail address: [email protected] b
Editorial
The significance of fluvial archives in geomorphology
1. Some aspects of historical approaches and modern trends in fluvial research Rivers have always been considered as one of the most important geomorphic agents. Since the 1950s, fluvial research has concentrated on understanding contemporary fluvial processes, spearheaded by American researchers such as L. Leopold and S. Schumm. These studies, exemplified also by Binghamton Symposia ŽMorisawa, 1974; Rhodes and Williams, 1979., have advanced substantially our understanding of river behaviour and channel patterns. At the same time, European geomorphology was more under the influence of climatic geomorphology Že.g., Cailleux and Tricart, 1958; Budel, 1977., which considered the relationship between the larger-scale morphology initiated by rivers and changing climate conditions. Recently, these two approaches have been combined, substantially advancing the interpretation of fluvial morphology. These advances have been illustrated in a number of special volumes and international programmes ŽGregory, 1983; Starkel et al., 1991; Vandenberghe et al., 1994; Frenzel et al., 1995; Gregory et al., 1995.. As an unfortunate consequence of the convergence of process studies and climatic geomorphology, another important external control on fluvial systems, tectonic movements, has been widely neglected in fluvial geomorphology. The study of tectonic influences on rivers has been largely left to sedimentologists Že.g., Alexander and Leeder, 1990; Leeder, 1993; Leeder and Jackson, 1993. who concern themselves with tectonic impacts limited largely to ‘mega-forms’ Že.g., Summerfield, 1981; Bridges,
1990.. Recently, however, there has been renewed interest in the role of tectonics in fluvial system development. This change in outlook is a consequence of more detailed geodetic measurements; better insights into the magnitude and timing of tectonic devents; and most importantly, a growing cooperation between geomorphologists and tectonicians in many regions. This latter cooperation is exemplified by the NEESDI-program ŽNetherlands Environmental Earth System Dynamics Initiative., a national science foundation funded program where geomorphologists, geophysicists and tectonicians have been cooperating since 1977, in an attempt to better understand natural environmental processes. In the last decade, thanks to the growing awareness of environmental values, in general, and the recognition that river valleys occupy an essential part of the landscape, the appeal of natural rivers has been rediscovered and appreciated again. As a consequence, environmental managers are increasingly governed by the characteristics of the natural river system in the architectural design of the present-day valley landscape. Fluvial geomorphology has proven to be capable of bringing considerable insight into the complex relationships governing natural river systems. In the short term, use is made of the intrinsic characteristics and the evolution of rivers to explain gradual processes, but much is also contributed by the study of extreme events, like floods, which characterize more abrupt natural river behaviour Žillustrated for instance by the recent establishment of an IGU Study Group ‘Environmental Change and Extreme Hydrological Events’.. In such applications, however, it is also necessary to realize that the channel and valley properties Žlike valley
0169-555Xr00r$ - see front matter q 2000 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 9 - 5 5 5 X Ž 9 9 . 0 0 1 1 9 - 1
128
Editorial
slope, river pattern, and river position within the valley. respond to the long-term effects of climate change and tectonic movements. Increasingly, computer modelling is being applied by fluvial geomorphologists. Theoretical modelling of slopes is relatively old ŽBakker and Le Heux, 1952., and sees continuing development by the research work of, for example, F. Anhert Že.g., Anhert, 1976. and M. Kirkby Že.g., Kirkby, 1978, 1993.. After the pioneering work by A.D. Howard Že.g., Howard, 1994; Howard et al., 1994. different kinds of fluvial models have been developed. Some of them tried to simulate the system as a whole with a few simple relations, and are often forced by external factors. Others tried to apply physical laws of sediment entrainment and transport, but are often restricted to small-scale channel processes Že.g., in Carling and Dawson, 1996.. River modelling is certainly a tedious job, because of the complexity of the system. However, it offers tremendous possibilities for sensitivity analysis in the understanding and application of past, present and future fluvial processes. Furthermore, any progress in modelling will need to be accompanied by detailed and reliable field data together with associated climatic and tectonic movement datasets. It seems that we face here only the beginning of a fascinating and challenging evolution in fluvial geomorphology.
2. The role of the Fluvial Archives Group (FLAG) in fluvial research The increasing interest in fluvial systems over the last decade has involved a wide range and growing number of disciplines including geomorphology, sedimentology, archaeology, ecology, engineering and planning. This multidisciplinary approach has led to a burgeoning of research concerned with the relationship between river behaviour and environmental change. Fluvial archives Že.g., sediments, morphology, historical maps, palaeoecology, etc.. preserve a tremendous source of information concerning the functioning and evolution of river systems. The study of each individual archive requires specialist expertise, but understanding the fluvial system benefits most from a combination of archives. The utility of each specific archive depends upon its spatial and
temporal scale, the age of the fluvial system and the basin characteristics as a whole. Furthermore, in order to appraise the evolution of the system, it is essential that all archives be dated accurately and reliably. It is the main aim of FLAG to foster the use of such archives in the investigation of fluvial systems. FLAG establishes a forum for the exchange of information and ideas and will facilitate accessibility to these wide and varied archives, by making data readily available through publication. Furthermore, foci for future researches are proposed resulting from problems identified in current researches. The latter may lead to the formulation strategies that can be used to facilitate joint ‘focused’ research initiatives. Two major research themes have been defined. The first theme is ‘Long terrestrial records’ which is concerned with fluvial archives that span the whole Quaternary. Within this theme, two specific foci are identified, namely: ‘global correlation of Late Cenozoic fluvial sequences’ and ‘fluvial activity and crustal instability’. The second theme is ‘Fluvial environments and processes’ within which two further foci are identified, namely: ‘fluvial response to rapid environmental change during the last interglacial–glacial cycle’ and ‘Holocene fluvial system response to frequent and rapid periods of environmental change — identification and modelling of forcing factors’. Although distinction is made between the various themes and foci, it is essential that each of these are integrated and applied in all relevant regions. These research themes are intended to link with IGU, INQUA and IGBP-PAGES programmes. FLAG was formed in 1996 as a research group of the British Quaternary Research Association for a fixed term of 3 years. FLAG has now moved on, and has established itself as an internationally oriented group with the same objectives. FLAG currently has over 160 members from 22 different countries Žhttp:rrqra.org.ukrFLAG..
3. Research results This issue of ‘Geomorphology’ presents a small selection of river studies, which illustrate the philos-
Editorial
ophy of FLAG research. They result mainly from a conference held in Arcen, The Netherlands in September 1997. These contributions show the relevance of different fluvial archives in the investigation of the above-mentioned research topics. The impact of climatic changes on river pattern as recorded in sediment sequences from the last glacial in eastern Germany is exemplified in a paper by Mol et al. Mol et al. suggest that the most important changes in fluvial activity take place at climatic transitions, but under the control of local conditions such as vegetation, supplied sediment and eventual permafrost. Tectonic influences at different scales and in different modes appear in several papers. A complicated pattern of block faulting and uplift in the Polish Sudeten Mountains during different periods of the Quaternary has provoked a complex drainage response expressed in diverse depositionr erosion rates and irregular valley slopes ŽKrzyszkowski et al... Maddy et al. adopt a simple and constant regional uplift to explain the Quaternary incision of the British rivers. This interpretation is discussed against other external driving mechanisms such as eustatic sea level fall and erosional isostasy. A welldocumented paper of northern French rivers by Antoine et al. is a good example of the combined influence of tectonic movements, climate and sealevel change. However, local characteristics like drainage basin size are shown to influence the response of individual rivers. Benito et al. describe the intrinsic response of Spanish rivers in the specific case of subsidence in the underlying karst bedrock resulting in the development of local terraces. Finally, a way of simulating valley evolution is reported by Veldkamp and van Dijke. This paper demonstrates in general how modelling may evaluate the production of fluvial archives, and in particular the nonlinear reaction of the river system to external controls. References Alexander, J., Leeder, M.R., 1990. Geomorphology and surface tilling in an active extensions basin, SW Montana, USA. Journal of the Geological Society of London 147, 461–467.
129
Anhert, F., 1976. Brief description of a comprehensive three-dimensional process-response model of landform development. Zeitschrift fur ¨ Geomorphologie, Supplement Band 25, 29–49. Bakker, J.P., Le Heux, J.W.N., 1952. A remarkable new geomorphological law. Proceedings of the Koninklijke Nederlandese Akademie van Wetenschappen, Series B 55, 399–410, 554– 571. Bridges, E.M., 1990. World Geomorphology. Cambridge Univ. Press, Cambridge. Budel, J., 1977. Klima-Geomorphologie. Gebr. Borntrager, Stuttgart. Cailleux, A., Tricart, J., 1958. Introduction a la geomorphologie climatique. Cours de Geomorphologie, Paris V. Carling, P.A., Dawson, M.R. ŽEds.., 1996. Advances in Fluvial Dynamics and Stratigraphy. Wiley, Chichester. Frenzel, B., Vandenberghe, J., Kasse, C., Bohncke, S. ŽEds.., 1995. Palaeoklimaforschung 14, 226 pp. European river activity as a function of climate changes during the Late Glacial and Early Holocene. ESF Project ‘European Palaeoclimate and Man’. Gregory, K. ŽEd.., 1983. Background to Palaeohydrology. Wiley, Chichester. Gregory, K., Starkel, L., Baker, V. ŽEds.., 1995. Global Palaeohydrology. Wiley, Chichester. Howard, A.D., 1994. A detachment-limited model of drainage basin evolution. Water Resources Research 30, 2261–2285. Howard, A.D., Dietrich, W.E., Seidl, M.A., 1994. Modelling fluvial erosion on regional to continental scales. Journal of Geophysical Research 99, 13971–13986. Kirkby, M.J. ŽEd.., 1978. Hillslope Hydrology. Wiley, Chichester. Kirkby, M.J., 1993. Network hydrology and geomorphology. In: Beven, K., Kirkby, M.J. ŽEds.., Channel Network Hydrology. Wiley, Chichester, pp. 1–11. Leeder, M.R., 1993. Tectonic controls upon drainage basin development, river channel migration and alluvial architecture: implications for hydrocarbon reservoir development and characterization. In: North, C.P., Prosser, D.J. ŽEds.., Characterization of Fluvial and Aeolian Reservoirs. Geological Society of London, Special Publication 73 pp. 7–22. Leeder, M.R., Jackson, J.A., 1993. The interaction between normal faulting and drainage in active extensional basins, with examples from the western United States and central Greece. Basin Research 5, 79–102. Morisawa, M. ŽEd.., 1974. Fluvial Geomorphology. SUNY, Binghamton Symposium, Geomorphology. Rhodes, D.D., Williams, G.P. ŽEds.., 1979. Adjustments of the Fluvial System. Alien & Unwin, Boston, Binghamton Symposium. Starkel, L., Gregory, K., Thornes, J. ŽEds.., 1991. Temperate Palaeohydrology. Wiley, Chichester. Summerfield, M., 1981. Macroscale geomorphology. Area 13, 3–8. Vandenberghe, J., Gibbard, P., Van den Berg, M. ŽEds.., 1994. Pleistocene river systems in Europe. Terra Nova 6 Ž5..
130
Editorial
Jef Vandenberghe a, ) Centre for Geo-ecological Research, Faculty of Earth Sciences, Vrije UniÕersiteit, De Boelelaan 1085, 1081 HV Amsterdam, Netherlands E-mail address: [email protected] a
)
Corresponding author. Fax: q31-20-646-2457.
Darrel Maddy b Department of Geography, UniÕersity of Newcastle, Newcastle-upon-Tyne, NE1 7RU, UK. E-mail address: [email protected] b