Geology Reference
In-Depth Information
estuaries, back-barrier systems and open coast tidal
fl ats and marshes. His classifi cation is more detailed,
recognizing ten types of channels within three catego-
ries: (1) single channels: straight, sinuous, and mean-
dering (sinuosity ratio > 1.5; see
Sect. 11.5.3
); (2)
channel systems: parallel channels, dendritic and elon-
gate dendritic, distributary, braided, and interconnect-
ing; and (3) few or no channels.
Further narrowing the environment considered, Pye
and French (
1993
) identify seven categories of net-
work within marsh systems. These overlap or expand
on those of Eisma (
1998
): linear single, dendritic and
linear dendritic, meandering dendritic; reticulate, com-
plex, and superimposed (Fig.
11.2
). Several types of
channels or channel network may occur concurrently
within a tidal system. The Wash (UK) is a classic
example of variability within a single estuary: in an area
approximately 25 km
2
, one may fi nd extensive salt
marshes, tidal fl ats and channel-shoal morphologies.
11.3
Classifi cation of Channels and
Channel Network Morophologies
Several authors have classifi ed tidal channel network
morphologies according to their planform. Hibma et al.
(
2004a
) broadly view an entire estuarine system, look-
ing at the large channel forms and making a general
classifi cation into two morphologies: fractal (i.e. den-
dritic systems) and braided (meandering, interconnected
channels separated by shoals; Fig.
11.1
). A similar clas-
sifi cation is made by van Veen (
1950
) who describes
them as 'apple tree' and 'poplar tree' morphologies,
respectively. These two morphologies loosely relate to
the shallow, intertidal and peri-tidal environments of
tidal fl ats and marshes, and the deeper subtidal environ-
ments, respectively, as described above.
Eisma (
1998
) examines intertidal channels on a
variety of scales in a range of coastal settings, including
Fig. 11.2
A classifi cation
for salt marsh creek networks
(After Pye and French
1993
)
