Geology Reference
In-Depth Information
Fig. 7.2
(
a
) Major river deltas classifi ed by the relative infl u-
ence of river, wave, and tidal processes (After Galloway
1975
) .
(
b
) Mean wave height versus mean tidal range for major large
river deltas. The areas are grouped into fi ve morphological
classes after the classifi cation of Davis and Hayes (
1984
)
(Modifi ed after Hori et al.
2002a
)
( Coleman et al.
1970
) and the Yalu and Ord rivers of
Korea and Australia, respectively (Coleman and Wright
1978
). None of these systems are discussed at length
in this chapter as they are best reclassifi ed as tide-
infl uenced deltas (Klang-Langat) or as tidal estuaries
(Yalu and Ord; see Chap. 5). In the 1980s the Amazon
and Changjiang (i.e. Yangtze) were the fi rst large tide-
infl uenced deltas to be studied in detail through large,
comprehensive, and multidisciplinary investigations.
The Amazon project, called AMASEDS, collected
observational data simultaneously at the seabed and
water column over different phases of the river hydro-
graph and tidal conditions, demonstrating the tremen-
dous benefi ts of such an integrated approach (Nittrouer
and DeMaster
1986
). Combined with sediment coring and
seismic-refl ection surveys, AMASEDS defi ned the mod-
ern approach for studying complex, river-fed continental
margin systems. A similar comprehensive study was done
for the Changjiang in Asia (Milliman and Jin
1985
) .
However research of tide-dominated deltas remained lim-
ited as most studies were of river- or wave-dominated
examples (e.g. Mississippi, Nile, Ebro, Rhine).
Middleton (
1991
) pointed out that a majority of
very large rivers in terms of sediment load discharge
along meso- to macrotidal coasts, forming tide-dominated
or tide-infl uenced deltas (Fig.
7.1
). In response,
research was initiated in several tidally affected
deltas, with the Fly river being among the fi rst major
tide-dominated deltas to be studied in detail (Harris
et al.
1996
; Wolanski et al.
1995
). Since that time the
rate of investigation has accelerated and today most
major tide-dominated delta systems have received some
formal investigation. Most studies have employed
stratigraphic or seismic-refl ection approaches, but
observational and hydrodynamic data remain rare for
many systems. Among several coordinated research
programs, recent efforts have focused on the Changjiang,
Mekong, and other nearby Asian deltas (e.g. Hori et al.
2001
; Ta et al.
2005
), and the Gulf of Papua 'contin-
uum' that includes the tide-dominated Fly and Kikori
deltas (e.g., Ogston et al.
2008
; Walsh et al.
2004
) . The
Ganges-Brahmaputra has been reasonably well studied
by individual working groups (Goodbred and Kuehl
2000
; Kuehl et al.
2005
; Michels et al.
1998
) , and to a
lesser extent the Indus (Giosan et al.
2006
) and Colorado
(Carriquiry and Sanchez
1999
; Thompson
1968
)
deltas. The Ayeyarwady (i.e., Irrawaddy) and Tigris-
Euphrates deltas, however, remain notable exceptions
with very little published research.
Other more general studies have advanced our
understanding of continental margin systems with
great implications for tide-dominated deltas, including
developments in shelf hydrodynamics and sediment
transport (Wright and Friedrichs
2006
) ,
and
the
