Environmental Engineering Reference
In-Depth Information
Figure 11.21(a) shows a satellite image of a typical plume network on the Loess Plateau in western China;
and Fig .11.21(b) shows a satellite image of a typical dentritic networks in northeastern China. Figure 11.22
shows the stream webs of the three types of drainage network. The plume network has a large number of
first order streams flowing into a second order stream, forming a plume-like structure. The vein network
has a main stream and its parallel tributaries, which looks like nervations. The dentritic network shows
continuous bifurcation, which looks like tree branches.
Horton's ratios were calculated from the statistics for the three typical networks. Figure 11.23 shows
Horton's ratios for the three types of network as functions of the stream order of the network. The
bifurcation ratio of a plume type network is about 12 for stream orders less than 4, which is much greater
than the value for a dentritic network (4) and a vein network (5). For stream orders higher than 4 the
bifurcation ratio reduces and converges for all the three types of networks and approaches 4 for the
stream order of 8. Other ratios have a similar trend. The ratios of dentritic networks are almost invariant
for different stream orders, but the ratios for plume networks vary over a great range. In other words a
dentritic network has the highest similarity between large watersheds and small watersheds; and a plume
network is very different for small watersheds and from large watersheds.
(a) (b)
Fig. 11.21 (a) Satellite image of a typical plume network on the Loess Plateau in western China; (b) Satellite image
of a typical dentritic network in northeastern China
Fig. 11.22 Three types of drainage networks (a) Plume network (in the north part of the loess plateau); (b) vein
network (the Yanhe River); and (c) Dentritic network (the Nuoming River)
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