Introduction to Stream Restoration - Hydro-Environmental Analysis: Freshwater Environments - page 239

Two common types of ish screens are positive barriers that prevent ish from passing and behav-
ioral barriers that encourage ish to swim away. The Washington Department of Fish and Wildlife
(WDFW 2000a) describes and provides design considerations for the following screen types:

• Rotary drum screens

• Vertical ixed-plate screens

• Vertical traveling screens (panel and belt types)

• Nonvertical ixed-plate screens

• Pump screens

• End-of-pipe screens

• Iniltration galleries

• Portable screens

Examples of end-of-pipe screens are illustrated in Figure 8.25 and construction guidance is pro-
vided by the Ontario Department of Fisheries and Oceans (ODFO 1995). In addition, visual, audi-
tory, electrical, and hydrodynamic stimuli have resulted in a large number of experimental barriers,
such as bubble screens, electrical screens, and hydrodynamic (louver) screens. The hydrodynamic
or louver screen consists of an array of vertical slats aligned across a canal intake at a speciied
angle to the low direction (ASCE 1995) and guides ish toward a bypass, applicable to sites with
relatively high approach velocities, a uniform low, and relatively shallow depths. The eficiency

FIGURE 8.25 Examples of end-of-pipe screens. (From ODFO, Freshwater Intake End-of-Pipe Fish Screen
Guideline , Ontario Department of Fisheries and Oceans, Ottawa, Ontario, 1995.)