Geoscience Reference
In-Depth Information
Mesopotamia, China, India, Egypt, and the Roman Empire, for example. Graf (
1984
)
attributes the first basic scientific statements about loose-boundary hydraulics to
the Italian hydraulician Guglielmini (1655-1710), with the French hydraulician
duBuat (1734-1809) providing detailed observations of bedform mechanics, includ-
ing “furrow” shapes, sizes, propagation speeds, and associated sediment motions.
In deference to the hydraulician's interest in observable bedform dynamics,
geologists use bedforms preserved in stratigraphic records to infer details of
historical currents and sedimentary environments. In this regard, de la Beche
(
1851
) and Sorby (
1859
) discuss ripple marks formed by currents, including their
orientation, shape, sizes, motion, and transport of sediment. Sorby (
1859
) notes that
such structures “are so common that they cannot have escaped the attention of
anyone who has carefully examined stratified rocks.” Jukes (
1862
) also discusses
ripple marks formed by currents, including their sizes and motions. He concludes
that current ripples indicate “that the strength, velocity and mode of action of moving
water in the old geological periods was precisely of the same kind and intensity as
those with which we are familiar at the present day.”
Efforts regarding observations of bedform dynamics in nature and through
controlled experiments accelerated in the late 1800s. Raudkivi (
1967
) cites an
expression for bedform celerity given by Partiot (
1871
) based on observations in
the River Loire. Numerous field observations of ripple marks, including their
sizes and their dynamics, are provided by Hunt (
1882
), with a principal focus on
ripples occurring in oscillatory flows. Darwin (
1883
) also discusses the respective
fine-sand ripples formed in uniform currents and oscillating flows. Of particular
relevance to the present chapter, he describes early experimental observations
of current-ripple sizes, shapes, orientation, growth, and dynamics, noting that
Forel (
1883
) refers to bedwaves formed by continuous currents as dunes in sum-
marising observations and his experimental studies. Deacon (
1894
) reports further
observations of experiments regarding the orientation, shape, propagation speed,
transport rate, and associated sediment dynamics for current ripples, and how these
vary with increasing flow strength. At the turn of the century, Bertololy (
1900
)
carried out studies of the formation of waves on a flattened creek bed, recording
their simultaneous appearance over the whole bed, orientation, downstream migra-
tion, lengthening, and lateral uniting to form normal current ripples (Bucher
1919
).
In a notable work, Cornish (
1901
), a student of Kumatology, describes observa-
tions of current-generated sand waves that are much larger than ripple marks, i.e.
dunes in today's terminology. He comments that Reynolds (
1891
) noted the
presence of these large tidal sand waves below low water in model estuaries,
where the existence of such waves in nature had been overlooked, principally as
they are out of sight, until the model results encouraged searches for them. Having
sought out field sites evidencing these tidal-current sand waves under conditions
favourable to examination, Cornish (
1901
) notes the shape, orientation, and varia-
tion with flow of these larger waves and provides measurements of lengths, heights,
and migration rates. He also provides observations of sand wave growth, including
inferences of bedform elimination (or coalescence as described in more recent
works, e.g. F
oter
1983
; Raudkivi and Witte
1990
; Coleman and Melville
1994
).
Cornish (
1901
) goes further to offer a theory on the origin, growth, and decay of sand
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