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Design For Fish Passage at Roadway - Stream Crossings: Synthesis Report
How to use this chapter
1.1 Purpose and Scope
This document is a design reference for the classification, assessment, design or retrofit of a roadway-stream crossing to facilitate fish passage. It is the result of a comprehensive literature review completed to categorize design procedures, case histories, and culvert assessment techniques. No new recommendations for a universal design procedure are made; rather, a compilation of design options used in different geographic regions is included to allow the user to select the most appropriate design method for their unique situation. A collection of design examples and case histories is intended to add clarity to the design methodology selection.
In order to provide stream reach connectivity for all wildlife, removal of road barriers or the installation of a bridge spanning the floodplain are ideal; however, this report presumes that a narrower, fish-friendly, installation is both permitted and desirable for economical or logistical reasons. It is recognized that fish are not the only animals requiring habitat connectivity for long-term population viability, and future versions of this circular are intended to cover aquatic organism passage (AOP) in more detail. This report is intended solely as a reference for the design, retrofit, or replacement of a road stream crossing to meet fish passage requirements.
The scope of this report is also limited to culvert installations. If the total culvert span including all barrels and fill between barrels exceeds 6.1 m (20 ft), it is called a bridge according to the Federal Highway Administration code:
Bridge. A structure, including supports, erected over a depression or an obstruction, such as water, a highway, or a railway, having a track or passageway for carrying traffic or other moving loads, and having an opening measured along the center of the roadway of more than 6.1 m (20 ft) between undercopings of abutments or spring lines of arches, or extreme ends of the openings for multiple boxes; it may include multiple pipes where the clear distance between openings is less than half of the smaller contiguous opening.
A logical progression is followed to guide the reader through the assessment and design process. Culvert analysis, design and retrofit techniques are then described, followed by case histories and design examples.
The increased biological, hydrological, and geomorphic sensitivity of a fish-passable structure requires that designers have access to a broad knowledge base. Proper assessment and design of a culvert installation or retrofit requires some expertise in hydraulic engineering, structural/geotechnical engineering, and hydrology; although, the level of experience needed varies depending on the preferred culvert installation/assessment method. Regional requirements for fish biology, hydrology, and geomorphology require that the design for fish passage be considered on a site-by-site basis, all but eliminating the possibility of a cookie-cutter design approach. Consultation with local engineers, stream ecologists and fish biologists will help ensure that the culvert selection, design, and alignment provide adequate stream reach connectivity, and that the most appropriate installation or retrofit strategy is selected based on ecological need, priority, cost, and site logistics.
1.2 Highway Perspective
Waterway crossings, including bridges and culverts, represent a key and expensive element in our overall transportation system. The design of crossing structures has traditionally used hydraulic conveyance and flood capacity as the main design parameters. Hydraulic Design Series - 5 Hydraulic Design of Highway Culverts(HDS-5) specifies a culvert design procedure to maintain acceptable headwater depth during design floods; this ensures efficient conveyance of water, but normally does not include provisions for fish passage through the culvert (Norman et al. 2005).
Design for hydraulic efficiency overlooks the impact of a roadway-stream crossing on the stream-channel aquatic ecosystem. Resulting structures often narrow the channel through the bridge opening or culvert barrel. Constricted reaches influence the characteristics of flow through and around the hydraulic structure, increasing velocities and scour potential (Johnson and Brown 2000). Augmented flow regimes may induce scour of the streambed through and downstream from the structure, and cause upstream progressing channel incision (Castro 2003). Table 1.1, from the Forest Service Stream Simulation Manual, lists a number of possible stream responses to altered hydraulic conditions caused by a traditionally sized crossing (Bates et al. 2006). In general, the effects of an undersized culvert can be described as a local destabilization of the stream channel (Johnson and Brown 2000).
Velocities resulting from traditionally sized culverts may exceed fish swimming ability, and scour at culvert outlets may prove too excessive for fish to leap into the structure (Venner Consulting and Parsons Brinkerhoff 2004). As a result, culverts act as barriers to juvenile and adult fish movement (Flanders and Cariello 2000; Wilder et al. 2004; Browning 1990). For example, Figures 1.1 and 1.2 depict outlet scour and channel degradation resulting in perching - the development of a falls or cascade at the culvert outfall due to erosion of the stream channel downstream of the drainage structure (Bates et al. 2003) - while Figure 1.3 illustrates the impact of debris deposition. Often, high quality upstream fish habitat is disconnected from downstream river and stream corridors by structures that are impassable for native fish (Trombulak and Frissell 2000).
1.3 Ecological Perspective
River and stream corridors provide vital habitat for a wide range of animal species, many of which depend on the ability to move freely throughout their ecosystem in order to complete their life cycles (Jackson 2003). The importance of human transportation has led to roads that extend through much of the country, inevitably crossing over streams and rivers (Schrag 2003). Structures designed to pass water under a road frequently do not consider animal movement, causing fragmentation of many riverine systems (Trombulak and Frissell 2000). Recognition of the need to restore habitat connectivity has added ecological consideration to the design and retrofit of road stream crossings (e.g. Jackson 2003; Bates et al. 2006). The following sections address issues associated with passage of all animals at roadway-stream crossings. The remainder of the report will focus on fish passage.
1.3.1 Importance of Animal Movement
As a dynamic environment, the habitat within riverine ecosystems is in a constant state of flux, producing the need for animal movement (Amoros and Bornette 2005). The ability to move freely throughout a stream ecosystem allows wildlife to seek food and shelter, mating partners, escape predation, or move in response to seasonal or extreme natural disturbances (Jackson 2003). While some animals can live their entire life under a single rock, others require substantial room to travel. For example, the Florida Black Panther has been shown to occupy home ranges up to 1182 km2 (734 mi2) (Cramer 1999), and salmon can travel hundreds of miles up rivers and streams to make their return from the ocean to headwater streams to spawn (Groot and Margolis 1991).
Freedom of movement allows wildlife to seek out habitat suitable to their life stage. Salamanders, for example, utilize headwater streams as adults, but seek out environments with more stable hydrology when breeding. The resulting larvae are weak swimming, and could not survive in the more dynamic riverine system occupied by adults (Jackson 2003). Adult salmon migrate to the ocean to grow, but return to the headwater streams of their birth to spawn (Groot and Margolis 1991). It has been observed that smaller resident salmonids move upstream and downstream, relying on more than a small stream reach for survival (Young 1995; Young 1996; Kahler and Quinn 1998).
Population dynamics are linked to movement, allowing many subpopulations to interact to increase genetic exchange and enhance biodiversity. Just as roads convey traffic from one point to another, streams and rivers provide an avenue for animals to seek out the resources they need to survive and enhance their genetic biodiversity. Disturbances in river continuity force animals to utilize smaller areas - blocking off spaces that were once an integral part of their range.
1.3.2 Road Stream Interaction
Roads cover almost 2% of the landmass in the United States, leading to a seemingly unavoidable interaction of roadways and the environment (Schrag 2003). For example, a survey of Bureau of Land Management (BLM) and U.S. Forest Service land found 10,000 culvert crossings on fish bearing streams in Washington and Oregon alone (General Accounting Office 2001). And estimates of road and railroad crossing affecting Massachusetts streams are as high as 28,500 (Venner Consulting and Parsons Brinkerhoff 2004). Such crossings impact aquatic organisms and fish, potentially causing barriers to passage, fragmentation, and a loss of ecological connectivity (Trombulak and Frissell 2000). Many of the roadway-stream culverts that are currently in place were designed and installed with hydraulic conveyance as the main criteria (Norman et al. 2005). Natural stream processes were not considered in favor of relatively inexpensive culverts that could pass a design flow without roadway overtopping. This design methodology ignored issues such as sediment transport, fish and wildlife passage, and generally had a significant impact on the stream's natural hydrology (Jackson 2003). For example, over half of the 10,000 culverts surveyed on Forest Service and BLM land in Washington and Oregon are considered to be barriers to juvenile salmon passage (General Accounting Office 2001).
Although much recent focus has been on the passage of fish, many other organisms are affected by improperly designed culverts, from small aquatic organisms such as salamanders to large terrestrial animals such as deer (United States Forest Service 2006a; Schrag 2003). In general, a culvert that is impassable for fish will also pose as a barrier to weaker swimming semi-aquatic organisms (Bates et al. 2006).
As increasing human population leads to an expansion of our infrastructure, the role of roads in habitat decline and fragmentation is the subject of increased scrutiny (e.g. Spellerberg 1998; Trombulak and Frissell 2000). The long-term ecological effects of roads include loss and change of habitat, changes in biological makeup of communities, and fragmentation - leading to population isolation (Spellerberg 1998).
1.3.3 Effects of Population Isolation
The effects of isolation are most dangerous in smaller populations, although a variety of parameters are involved in analysis of population vulnerability (Mace and Lande 1991). With a smaller isolated group there will be an increase in genetic homogeneity, as well as higher susceptibility to natural or chance events (Mace and Lande 1991). This can mean local extinctions due to drought or fire, and the results of inbreeding, including genetic weakness, which makes the population susceptible to disease, decreased reproduction, high mortality, and possibly to extinction (McKelvey et al. 2002).
For both aquatic and terrestrial organisms, negative impacts of roadway interaction are manifest through a loss of population connectivity. The species most vulnerable to isolation are those with large home ranges and low population numbers, including bears, wolves, mountain lions, Florida panthers, lynx, snakes and desert tortoises (Hass 2000). The removal of these predators can have a significant impact throughout the food web, and many attempts to increase connectivity have been undertaken in the United States, Canada and Europe, including underpasses and overpasses (Schrag 2003). Many of these wildlife-crossing case histories can be accessed through the U.S. Forest Services Wildlife Crossing Toolkit website at http://www.wildlifecrossings.info/beta2.htm.
Aquatic organism passage (AOP) was the focus of a short course developed by the U.S. Forest Service (2006b). To provide connectivity, roadway-stream crossings must provide a desirable passageway for aquatic organisms at a variety of flows. Culverts that mimic stream reach characteristics can provide favorable connectivity at a culvert crossing (Bates et al. 2006). Bridges, however, offer the most protection against habitat fragmentation (Robison et al. 1999). Organisms such as moles, salamanders, newts, and mussels depend on the ability to move between habitats at different life stages. For such organisms, the ability to reach vital rearing habitat is essential to survival, and fragmentation could spell the end of a localized population. With the recognition of the importance of ecological connectivity, limiting the disruption that roadway-stream crossings pose has received recent focus (e.g. United States Forest Service 2006a; Jackson 2003), and is even the subject of a lawsuit brought against the State of Washington by twenty of its Native American tribes (Wildlife Management Interactive 2001).
Without ecosystem connectivity, areas could remain void of species diversity, as new populations cannot move in to mitigate a local extirpation (e.g. Morita and Yamamoto 2002). The loss or disconnection of any portion of an ecosystem is undesirable but is not necessarily detrimental to a population (Farhig and Merriam 1985). Even in an undisrupted ecosystem individual animals are constantly in danger of death even as the larger population remains in tact. Persistence is the result of a constantly refreshing gene pool, which maintains genetic health. Connectivity ensures that wildlife is given the chance to move freely in order to complete life cycle functions and maintain long-term population viability.
The emphasis of this report is on fish passage. Future versions will address AOP as more information becomes available.
1.4 Legislation and Regulation
Several statutes, regulations and Executive Orders may need to be coordinated during selection, design, installation, operation and maintenance of culverts, especially those in waters that support fish. Almost all of the relevant statutes delegate jurisdiction by statute or expertise to one or more regulatory or coordinating agencies.
These statutes and Executive Orders represent societal values and, in most cases, identify obligations of federal agencies that are as important to the public as is a safe and reliable road network. It is a fundamental engineering challenge to collaborate with other disciplines and agencies to identify one or more culvert solutions that optimize as many of those societal values as possible. The information in this section is provided to encourage active and informed interdisciplinary and multiple agency discussions which will enhance the permitting process, improving cost, time, safety and ecosystem efficiencies.
Environmental regulatory agencies have greatly streamlined and simplified the permit application processes for installing, replacing or extending a culvert at a roadway-stream crossing, but there are still many occasions where the process does not go smoothly, or may be complex and seem frustrating. Regardless, a key to long-term success is ongoing good faith efforts to help all agencies and stakeholders attain their goals. Striving to meet transportation and environmental goals when roads cross streams requires routine use of common sense, and participation of interdisciplinary and multiple agency teams to support hydraulic, design, safety and structural engineering.
This section provides a brief description of some of the most frequently encountered federal environmental statutes and agencies. Negotiated agreements between State Departments of Transportation (DOTs) and regulatory agencies are preferred to mandated solutions.
1.4.1 Statutes and an Executive Order
220.127.116.11 Clean Water Act (CWA) 1948
The Federal Water Pollution Control Act, also known as the Clean Water Act, is intended to restore and maintain the physical, chemical and biological integrity of waters of the United States. This law addresses the discharge of pollutants into water bodies. Pollutants can include concentration levels of dissolved oxygen, temperature, sediment and even color. This law is the source of each States' (and some Tribal) water quality standards, which always include an anti-degradation clause: discharge of pollutants can not degrade the waterway's designated uses. If aquatic life is a designated use, culvert installation, operation and maintenance should not cause physical, chemical or biological degradation or otherwise alter fish species composition and demographics, and habitat. The discharge should not impede fish movements, the movements of prey and forage, or symbiotic and commensal species.
In addition, all states support a list of non-attainment waters as required by CWA 303(d). The 303(d) list is generally linked to total Daily Maximum Load (TMDL) limitations.
Three sections of the CWA are relevant to culvert installation across the country: sections 401 (water quality certification), 402 (National Pollution Discharge Elimination System permits), and 404 (dredge and fill, also called "wetland" permits). In rare circumstances, Section 403 (ocean discharge permits) may be required. Permits or certification notices issued under sections 401 and 402 may be indistinguishable in practice. They address the project's compliance with State water quality standards; most States, and many tribes, have assumed responsibility for these programs from the Environmental Protection Agency (EPA). Permits issued under Section 404 generally address the placement of fill material, including pipes and the pipe-soil matrix, into designated water bodies. The U.S. Army Corps of Engineers is the primary, on-the-ground jurisdictional agency, but the EPA has joint oversight of the program, and Section 404 permits, while most commonly associated with wetlands in the public mind, cover fill in streams, lakes and more.
The regulatory agencies at state and federal levels have established simplified permit processes for routine activities that do not degrade the environment. These may be nationwide, regional or state wide in scope.
18.104.22.168 Endangered Species Act (ESA) of 1973
The ESA obligates all federal agencies to seek to conserve, or recover, federally listed species, and to use all their authorities and programs, including grants, loans, permit issuance and technical assistance, to do the same. The law's purpose is to provide a means to conserve the ecosystems which federally listed species depend on, to conserve or recover those listed species, and to meet the Nation's obligations under treaties and conventions. The law and implementing regulations and guidance dictate the process for listing species as threatened or endangered. Recognize that federally listed threatened and endangered species are jurisdictionally distinct from State listed species. International and other treaties and conventions may be relevant where certain transboundary fish restoration or invasive species control issues are in effect.
For current purposes, federally listed species fall into two categories. Endangered identifies those species which are in imminent risk of extirpation. Threatened identifies the next highest risk category, species or populations facing imminently imminent risk of extirpation. Species that fall under either of two additional categories, proposed and candidate, are not technically considered federally listed. Nevertheless, species that fall within these latter categories generally warrant special administrative procedures or protective measures. The ESA's protections are limited to plants and animals
Two agencies, the Fish and Wildlife Service and the National Marine Fisheries Service (or National Oceanographic and Atmospheric Administration - Fisheries), collectively called the Services, have jurisdiction by law and expertise. The rationale used to allocate each species and life history stage to a Service is not always clear.
The law also requires the jurisdictional agencies to designate critical habitat for listed species. The rulemaking material must include a description of the constituent elements, including structures, processes and ecosystem attributes, that must be protected or restored for the habitat to support recovery. This can include geomorphic and hydrologic processes. Federal projects that adversely constrain or alter those constituent elements are said to adversely modify the designated critical habitat. This implies that the project will prevent recovery of the listed species, which no single agency head can allow.
Federal projects that may affect a listed animal must undergo a cooperative consultation under Section 7 of the ESA with the Fish and Wildlife Service or National Marine Fisheries Service to avoid violating Section 9 prohibitions. This consultation is intended to mitigate the adverse effects of the action on listed species to the extent practicable. Often, agencies that routinely conduct activities that may affect listed species develop a set of best management plans which preclude the need for formal consultation.
For non-federal entities carrying out an action that may take a listed species, the ESA includes alternate means of working cooperatively with the Services to minimize take and still implement the project without violating Section 9's prohibitions. Take is broadly defined to include harassing, killing, wounding or otherwise interfering with individuals, or disturbing habitat used for feeding, breeding, sheltering and, in the case of fish, spawning and rearing.
Decades of experience suggests that collaboration and ongoing discussions between agencies and disciplines offer the highest level of certainty that consultation for projects that may affect listed fish species will be completed in a timely and effective manner. Because the consultation process is both substantive and procedural, agencies like the Federal Highway Administration recommend using a collaborative, interdisciplinary problem-solving approach to consultation.
22.214.171.124 Fish and Wildlife Coordination Act (FWCA) 1934
The FWCA recognizes the importance of wildlife resources to the nation. It requires federal agencies undertaking water resource projects to give equal consideration and coordination to fish and wildlife resource conservation. Undertakings are generally accepted to include funding, permitting and more. The law originally targeted game and furbearing animals, and commercially and recreationally valuable fish and shellfish (reflecting the traditional concern for "fur, fins and feathers"). By dint of emerging scientific knowledge and well established practice, consideration is now given to ecosystem patterns, processes and the species therein.
The law is one of the vehicles that Fish and Wildlife Service, National Marine Fisheries Service, Department of Agriculture bureaus and State fish and game agencies use to provide cooperative assistance and reports on environmental effects of proposals to Federal action agencies. It authorizes the Fish and Wildlife Service to conduct investigations, including comment letters, to protect environmental resources, and allows Federal agencies to fund preparation of those reports.
126.96.36.199 National Environmental Policy Act (NEPA) 1969
The NEPA encourages productive and enjoyable harmony between man and the environment as national policy. It is one of only a few statutes that include the word "ecosystem," and the authors assert that it was introduced and passed to balance the effects of the Full Employment Act of 1948, which obligates Federal agencies to promote economic growth in all of their activities.
More important from the perspective of fish passage and culverts, the NEPA also established the requirement that Federal decisions be informed about the environmental consequences of those actions. These consequences encompass what is described as the human and natural environments. Coverage can be comprehensive when required; the implementing regulations, however, encourage a common sense approach.
The NEPA analytic documentation is differentiated by four categories, those that are: (1) statutorily excluded, which could include certain disaster response activities, (2) categorically excluded, which include activities that the evidence suggests individually and cumulatively have no significant, lasting effect on the environment, (3) Environmental Assessment and Finding of No Significant Impact, which is usually a cursory or preliminary evaluation of potential effects, with the obvious conclusion, and (4) Environmental Impact Statement and Record of Decision, which are activities that require more substantive analysis because they are likely or known to have significant environmental consequences, or high degrees of uncertainty and controversy.
The NEPA applies to Federal agencies that directly or indirectly implement projects, establish rules or enforce laws. The NEPA analysis is, for example, conducted by the U.S. Army Corps of Engineers when that agency issues a Clean Water Act section 404 permit authorizing installation of a culvert. In many States, the regulatory and decision-making agencies have developed streamlined processes that allow them to join together and conduct a single NEPA analysis for the various agencies that must make decisions. Such streamlined processes provide for "one-stop shopping" to culvert placement proponents, regulatory agencies, environmental agencies and other stakeholders.
The NEPA, in practice, is the most important source for interdisciplinary approaches, public involvement and similar initiatives.
188.8.131.52 Rivers and Harbors Appropriations Act of 1899
The Rivers and Harbors Act is concerned with navigation in the nations' waters, and the regulation of interstate commerce related to that navigation. The law has two "permit" sections of interest when considering roadway-stream crossings.
The U.S. Coast Guard, a bureau of the Department of Homeland Security, has jurisdiction over Section 9. This section requires a permit or authorization for construction of bridges, dams, dikes or causeways over or in navigable waterways. An exception in the process exists for navigable waterways that are entirely within one State's boundaries.
The U.S. Army Corps of Engineers has jurisdiction for permits issued under Section 10. Section 10 covers the building of any wharfs, piers, jetties and other structures, and excavation or fill within navigable waters. In practice, Section 10 permits are considered part and parcel of the Clean Water Act section 404 permit process; the popular reference is to a "Section 10/404 permit."
184.108.40.206 Sustainable Fisheries Act 1996
The Magnuson-Stevens Fishery Conservation and Management Act, also known as the Sustainable Fisheries Act, primarily directs States to work together through various commissions and councils to manage marine and Great Lakes commercial fisheries. Of interest for the present purposes is the requirement that those multiple state fishery management councils develop fishery management plans, using an ecosystem and ecological approach. The plans must identify Essential Fish Habitat (EFH) for all life stages of the target species and associated species and processes. Coastal waters that are designated EFH under this statute may pose unique challenges when designing, installing, operating and maintaining culverts. The EFH is designated by councils or commissions comprised of state marine fish agencies or their equivalent; EFH within a State are protected by the relevant state agency and the National Marine Fisheries Service, also known as National Oceanographic and Atmospheric Administration - Fisheries. Those agencies review activities authorized or funded by Federal agencies, and coordinate to ensure that the functional integrity of the EFH is not degraded.
220.127.116.11 Wild and Scenic Rivers Act 1968
The Wild and Scenic Rivers Act establishes a National Wild and Scenic Rivers System. This law is of interest here only in that special considerations apply when considering culvert installation or any road feature in or adjacent to a designated Wild and Scenic River.
18.104.22.168 Executive Order on Recreation Fisheries 1995
The Executive Order on Recreational Fisheries (EO), number 12962, directs federal agencies to support recreational fishing. Collaborative efforts are encouraged. Such efforts can include aquatic resource habitat conservation and restoration, implementation of programs in a manner that supports recreational fisheries, and more. The EO can be used to support federal agency involvement in partnerships that address fish passage through culverts.
1.4.2 State and Local Regulations
In addition to federal regulations, there may also be a number of regional, local or state regulations that apply to the design and installation of roadway-stream crossing structures. For example, the NOAA National Marine Fisheries Service (NMFS) has fish passage policies in place for several of their regions. Such regulations may dictate construction timing, allowable sediment levels, fish passage requirements, or preferred culvert design techniques. It is important to consult with local authorities before beginning any project.
1.5 Multidisciplinary Nature of Providing for Fish Passage at Roadway-Stream Crossings
Historical culvert designs were most often performed exclusively by roadway-design or hydraulic engineers. Little, if any, consultation was required with other staff or agencies.
Providing for fish passage involves the additional disciplines of fisheries biology, geomorphology and possibly aquatic ecology. It will also require complying with legislative actions that are administered by multiple local, State and Federal agencies.
Design engineers must expand the design team to include experts from the additional disciplines and to communicate openly and consistently with regulatory agencies. The additional experts may be part of the State DOT staff or may be found in State or Federal natural resources agencies.
It is recommended that each State DOT roadway and hydraulics section assemble teams appropriate for the design of roadway-stream crossings for fish passage. This will provide (a) consistency in the application of design methods, and (b) will likely facilitate the establishment of general and regional permits with regulatory agencies.
1.6 Related fhwa publications and report preview
Table 1.2 summarizes related FHWA publications helpful when performing culvert design. For example, HDS-5 discusses the hydraulics of culverts in great detail, and HDS-6 provides detailed background and formulae for considering geomorphic aspects of river mechanics.
A brief summary of the report chapters is listed in Table 1.3. The report need not be read sequentially; the reader can go directly to chapters of interest. Cross references are used to direct the reader to other essential sections.