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Design For Fish Passage at Roadway - Stream Crossings: Synthesis Report
How to use this chapter
Although much research has been done to understand the requirements of fish passage, gaps in knowledge, nuances in fish behavior, and lack of adequate hydraulic and hydrological data result in criteria that are likely quite conservative (Furniss 2006). A monitoring program will help ensure that structure impact on fish passage is more clearly understood, allowing future criteria for assessment and design to be more effective, and aiding in reducing future expenditures for fish passage (General Accounting Office 2001).
10.1 Purpose and Scope
The four types of monitoring listed in Table 10.1 can be carried out on a fish passage project (adapted from Collins 2003).
For the purposes of fish passage monitoring, implementation and effectiveness monitoring are the most pertinent consideration (Collins 2003). Barnard's study of stream simulation culverts in western Washington is an example of effectiveness monitoring, and has allowed a better understanding of variables (i.e. width ratio and slope ratio) leading to successful stream simulation (2003).
For fish passage installations, implementation and effectiveness monitoring protocols might be used to answer the following questions (Collins 2003):
Monitoring may take place completely within a State DOT or may be the product of a multi-agency regional agreement. The latter approach would ensure consistent communications between all agencies responsible for fish passage.
Monitoring should begin with clear project goals that will allow the development of measurable parameters to allow "success" to be quantified (Committee on Restoration of Aquatic Ecosystems 1992). Ideally, monitoring might include direct observation of fish movement and utilization, but should at least focus on project compliance with design specifications such as substrate retention and the ability to maintain fish passable conditions (Furniss 2006).
Beginning with project goals in mind, parameters and field methods should be aimed at comparing current physical conditions to design performance criteria. Building upon this type of analysis, Harris (2005) developed the following criteria (Table 10.2) for fish passage installation effectiveness monitoring in California.
10.2.1 Inventory and Assessment
Inventory and assessment, as outlined in Chapter 4 is a form of effectiveness monitoring that will allow designers to gain design experience through an understanding of the impact that structures have on a stream reach and fish populations. Many design techniques, such as those described in Browning's survey of culverts in Oregon (1990), were derived from field observations of existing structures, and can continue to be modified as monitoring provides insight into the sustainability and impact of specific culvert design elements.
10.2.2 Surveying and Field Inspection
Monitoring, surveying and field inspection should focus on many of the same elements described in Chapter 4. This can include consideration of channel slope and elevation, culvert slope, crossing inlet and outlet conditions, existing bed material, and debris accumulation. Photos, benchmarks, monumented cross sections, and floodplain and terrace elevations can be useful in determining the culvert impact on the surrounding stream, and to determine if channel incision has occurred (Castro 2003). A major question to ask while in the field is - Is this culvert functioning as intended? (Furniss 2006).