Environmental Engineering Reference
In-Depth Information
Total sediment load
By origin
By transport
By sampling method
Suspended load
Wash load
Suspended load
Unsampled load 1
Bed-material load
Bed load
Bed load
1 That part of the sediment load that is not collected by the depth-integrating
suspended-sediment and pressure-difference bed-load samplers used, depending
on the type and size of the sampler(s). Unsampled-zone sediment can occur in one
or more of the following categories: (a) sediment that passes under the nozzle of
the suspended-sediment sampler when the sampler is touching the streambed
and no bed-load sampler is used; (b) sediment small enough to pass through the
bed-load sample's mesh bag; (c) sediment in transport above the bed-load sampler
that is too large to be sampled reliably by the suspended-sediment sampler; and
(d) material too large to enter the bed-load-sampler nozzle.
Fig. 2.1 Components of total-sediment
load considered by origin, by transport,
and by sampling method.
From Diplas et al. (2008).
October 9, 1989
October 11, 1989
October 12, 1989
6.0
3.0
0
-3.0
-6.0
7.5
Helley-Smith
BL-86-3
6.0
4.5
3.0
1.5
0
10
11
12
13
14
15
16
11
12
Time (h)
13
14
15
16
17
18
Fig. 2.2 Variability in sand bed-load transport rates measured 2 meters apart by a Helley-Smith bed-load sampler and a BL-86-3
bed-load sampler (the latter identical to the US BL-84 bed-load sampler), at the U.S. Geological Survey (USGS) streamgage on the
Colorado River above National Canyon near Supai, Arizona, USA, October 1989.
From Gray et al . (1991).
The spatiotemporal distribution of bed material
transport is a complicated, non-linear function of
sediment supply, bed state, and fl uid forcing (Gomez
1991). Figure 2.2 shows variations in bed-load trans-
port rates measured by two types of pressure-differ-
ence sampler deployed at fi xed locations 2 meters
apart during steady fl ows near the middle of the sand-
bedded Colorado River above National Canyon near
Supai, Arizona, USA (Gray et al. 1991). Such variabil-
ity is more or less typical for at-a-point bed-load
measurements. However, after collection of 390
discrete bed-load transport samples using two types
 
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