Environmental Engineering Reference
In-Depth Information
•
Environmental attractors and stressors (low volumes, low velocity, water temperature,
seasonal timing)
•
Relevant behavioral characteristics of the target species that could affect ish passage
(water temperature preferences and avoidances)
The NRCS (2007b) tabulates information on swimming speeds, etc., that can aid in design, as
illustrated in Table 8.5.
Fishways can be formal concrete structures or roughened channels, as illustrated in Figure 8.18.
Improperly designed culverts are also common impediments to ish movement, and culvert redesign
and replacement to provide ishways are a common practice.
8.4.10.1 Concrete Fishways and Ladders
Concrete ish ladders and ishways are structures that are designed to allow ish the opportunity to
migrate upstream, over, around, or through a barrier to ish movement. Common examples include
pool-weir or vertical-slot ishways. Figure 8.20 illustrates a general coniguration and examples
are illustrated in Figure 8.21. Pool-weir ishways, the most common type of ishway in the Paciic
Northwest (WDFW 2000a), have distinct pools (steps) separated by weirs. The weirs may be with or
without oriices (Figure 8.20). Vertical-slot ladders are also commonly used and have a large narrow
slot to control the water low and the depths in the pools between slots. The pools should provide
adequate capacity and depth to dissipate hydraulic energy, maintain a stable low, and provide room
for ish to accelerate and jump (NRCS 2007b) according to their maximum swimming speeds and
jumping capacity (see Table 8.5).
8.4.10.2 Roughened Channel Fishways
Roughened channels are chutes or lumes with roughness, which are designed to reduce velocity,
allowing ish passage. Examples of designed roughened channels include the Denil-style ishways.
Denil ishways are rectangular channels itted with symmetrical, closely spaced bafles that redirect
the lowing water and allow ish to swim around or over a barrier (NRCS 2007b; Figures 8.22 and
8.23). Denil ishways have been used in Alaska and the Paciic Northwest to pass migrating adult
salmonids over small barriers (Slatick and Basham 1985). Used on large and medium-sized rivers,
particularly those with highly variable lows, they are typically constructed as three-sided, sloping,
TABLE 8.5
Example of Maximum Swimming Speeds and Maximum Jumping
Heights for Selected Adult Salmonids
Sustained
Speed
Cruising Speed
Burst Speed
Jump Height
Salmonid
Species
ft. s
-1
m s
-1
ft. s
-1
m s
-1
ft. s
-1
m s
-1
ft.
m
Steelhead
4.6
1.4
13.7
4.18
26.5
8.08
11.2
3.4
Chinook
3.4
1.04
10.8
3.29
22.4
6.83
7.8
2.4
Coho
3.4
1.04
10.6
3.23
21.5
6.55
7.2
2.2
Cutthroat
2
0.61
6.4
1.95
13.5
4.11
2.8
0.9
Chum
1.6
0.49
5.2
1.58
10.6
3.23
1.7
0.5
Sockeye
3.2
0.98
10.2
3.11
20.6
6.28
6.9
2.1
Source:
NRCS, Fish passage and screening design, Technical supplement 14N (210-VI-
NEH),
Part 654 National Engineering Handbook
, Natural Resources Conservation
Service, 2007b.
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