Growth of Present-Day Concepts, up to 1977
the channels in a fluvial distributary system, as in
giant modern fans. Analogies with the Kosi fan have
commonly been drawn (e.g., Collinson 1986). Unfortunately, Campbell's reconstruction has now been
shown to be seriously flawed (Sect. 10.3.2).
Other work included a study of the geometry of
sand units on a delta plain by Ferm and Cavaroc
(1968). Horne and Ferm (1976) described the architecture of some Carboniferous coal-bearing rocks in
the central Appalachians, based on large highway
and railroad exposures. Cant (1978) erected a hypothetical model for the two-dimensional geometry
of a braided system of South Saskatchewan type.
Nami and Leeder (1978) described the geometry of a
well-exposed meandering river deposit. Friend
(1978) commented on gross architectural features of
several ancient fluvial systems.
Vegetation is an architectural control of considerable importance, affecting channel morphology
and shifting behavior through increasing bank ·stability (D.G. Smith 1976) and, by its presence or absence in headwater catchment areas, playing a large
part in determining the nature of the river hydrograph and the sediment supply. The geomorphic
effects of vegetation were recognized in the nineteenth century (e.g., Surell 1841, 1870), but Schumm
(1968a) was the first to clearly point out its
paleoclimatic implications. He suggested that rivers
of pre- and post-Devonian age were probably fundamentally different because of the first appearance in
the Devonian of an extensive cover of land vegetation. Long (1978) discussed the implications of this
difference for studies of the Proterozoic fluvial
record, and Cotter (1978) examined the Paleozoic
record of the Appalachians.
On all scales ranging from the local to the continental, a knowledge of the geometry and dispersal
patterns of alluvial deposits can lead to a better
understanding of contemporary tectonics, as several
papers published in the 1970s were beginning to
demonstrate (e.g., Steel and Aasheim 1978; McLean
and Jerzykiewicz 1978; Friend 1978; Potter 1978;
Miall 1978d).
2.3.8 Paleohydraulics
The study of fl uvial facies in vertical proflles or in
two or three dimensions is an essentially qualitative
approach to the reconstruction of past river systems,
even where statistical techniques are used to provide
quantitative information regarding facies assem35
blages (Sect. 10.4). Paleohydraulics is the study of the
quantitative relationships between the hydraulic parameters of a river (depth, width, slope, discharge,
sediment type, etc.) and its preserved deposits.
The study of paleohydraulics is fraught with
difficulties, and some fluviologists feel that our
knowledge of the depositional and preservational
processes of rivers is still so inadequate that numerical estimates of past hydraulic parameters verge
on the fictional. However, some progress has undoubtedly been made, and continued attempts at
paleohydraulic reconstruction can only serve to en�
courage fluvial sedimentologists to structure their
future research into modern rivers so as to ask the
right questions, in the hope that some of the difficulties can gradually be overcome . .
There are essentially two approaches to paleohydraulics, the engineering approach, which uses
theoretical relationships and empirical data regarding sediment transport mechanics and bedform generation to reconstruct the depositional conditions
for individual beds or sedimentary structures, and
the geomorphological approach, which relates empirical data about the morphology of modern
rivers to some of the gross features of their deposits.
Each method has its limitations - the engineering
approach concerns itself primarily with instantaneous depositional conditions of specific bedding
units, the overall, long-term significance of which
may be hard to judge because of our lack of knowledge of facies preservability in fluvial environments.
And, as Allen (1973, 1974a) has shown, bedforms are
slow to react to changes in flow conditions and are
therefore inaccurate hydraulic indicators. The geomorphological approach is potentially more useful,
in that it deals with long-term, statistical averages,
but suffers, at present, from a gross lack of data from
all but a limited range of modern climatic, discharge,
and sediment-load conditions. Even at the time of
writing this book sedimentological concepts regarding rivers are derived from verf few, possibly atypical, modern examples, most of which are located in
populated or otherwise accessible, relatively temperate climates. The range of different conditions represented by ancient fluvial deposits of all ages has
barely been touched, and research which integrates
sedimentology with hydraulics is sparse. We are
hampered, also, by the influence on modern rivers of
the rapid climatic and sea-level changes during and
following the Quaternary glaciation, and an uncertainty as to how this distorts our perceptions of
rivers at times of greater geological stability. Recent
the channels in a fluvial distributary system, as in
giant modern fans. Analogies with the Kosi fan have
commonly been drawn (e.g., Collinson 1986). Unfortunately, Campbell's reconstruction has now been
shown to be seriously flawed (Sect. 10.3.2).
Other work included a study of the geometry of
sand units on a delta plain by Ferm and Cavaroc
(1968). Horne and Ferm (1976) described the architecture of some Carboniferous coal-bearing rocks in
the central Appalachians, based on large highway
and railroad exposures. Cant (1978) erected a hypothetical model for the two-dimensional geometry
of a braided system of South Saskatchewan type.
Nami and Leeder (1978) described the geometry of a
well-exposed meandering river deposit. Friend
(1978) commented on gross architectural features of
several ancient fluvial systems.
Vegetation is an architectural control of considerable importance, affecting channel morphology
and shifting behavior through increasing bank ·stability (D.G. Smith 1976) and, by its presence or absence in headwater catchment areas, playing a large
part in determining the nature of the river hydrograph and the sediment supply. The geomorphic
effects of vegetation were recognized in the nineteenth century (e.g., Surell 1841, 1870), but Schumm
(1968a) was the first to clearly point out its
paleoclimatic implications. He suggested that rivers
of pre- and post-Devonian age were probably fundamentally different because of the first appearance in
the Devonian of an extensive cover of land vegetation. Long (1978) discussed the implications of this
difference for studies of the Proterozoic fluvial
record, and Cotter (1978) examined the Paleozoic
record of the Appalachians.
On all scales ranging from the local to the continental, a knowledge of the geometry and dispersal
patterns of alluvial deposits can lead to a better
understanding of contemporary tectonics, as several
papers published in the 1970s were beginning to
demonstrate (e.g., Steel and Aasheim 1978; McLean
and Jerzykiewicz 1978; Friend 1978; Potter 1978;
Miall 1978d).
2.3.8 Paleohydraulics
The study of fl uvial facies in vertical proflles or in
two or three dimensions is an essentially qualitative
approach to the reconstruction of past river systems,
even where statistical techniques are used to provide
quantitative information regarding facies assem35
blages (Sect. 10.4). Paleohydraulics is the study of the
quantitative relationships between the hydraulic parameters of a river (depth, width, slope, discharge,
sediment type, etc.) and its preserved deposits.
The study of paleohydraulics is fraught with
difficulties, and some fluviologists feel that our
knowledge of the depositional and preservational
processes of rivers is still so inadequate that numerical estimates of past hydraulic parameters verge
on the fictional. However, some progress has undoubtedly been made, and continued attempts at
paleohydraulic reconstruction can only serve to en�
courage fluvial sedimentologists to structure their
future research into modern rivers so as to ask the
right questions, in the hope that some of the difficulties can gradually be overcome . .
There are essentially two approaches to paleohydraulics, the engineering approach, which uses
theoretical relationships and empirical data regarding sediment transport mechanics and bedform generation to reconstruct the depositional conditions
for individual beds or sedimentary structures, and
the geomorphological approach, which relates empirical data about the morphology of modern
rivers to some of the gross features of their deposits.
Each method has its limitations - the engineering
approach concerns itself primarily with instantaneous depositional conditions of specific bedding
units, the overall, long-term significance of which
may be hard to judge because of our lack of knowledge of facies preservability in fluvial environments.
And, as Allen (1973, 1974a) has shown, bedforms are
slow to react to changes in flow conditions and are
therefore inaccurate hydraulic indicators. The geomorphological approach is potentially more useful,
in that it deals with long-term, statistical averages,
but suffers, at present, from a gross lack of data from
all but a limited range of modern climatic, discharge,
and sediment-load conditions. Even at the time of
writing this book sedimentological concepts regarding rivers are derived from verf few, possibly atypical, modern examples, most of which are located in
populated or otherwise accessible, relatively temperate climates. The range of different conditions represented by ancient fluvial deposits of all ages has
barely been touched, and research which integrates
sedimentology with hydraulics is sparse. We are
hampered, also, by the influence on modern rivers of
the rapid climatic and sea-level changes during and
following the Quaternary glaciation, and an uncertainty as to how this distorts our perceptions of
rivers at times of greater geological stability. Recent