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Streams & Rivers Restoration
The concept of stream restoration refers to returning degraded ecosystems to a stable, healthy condition. Those who take on this task must consider the factors that impact the rivers and streams and recognize that completing restoration projects involves a number of sequential steps.
Getting from concept to completion of a restoration project can be daunting. Understanding the sequential steps of planning, designing, funding, constructing, and monitoring restoration projects is critical to venturing into the process and achieving restoration success.
River restoration requires expertise in a number of disciplines and specialized skills. The leader, or project manager, is responsible for organizing and bringing together various project partners, agency technical staff, non-governmental, and other parties interested in or concerned with a potential project. Such partnerships can create effective avenues for addressing multi-faceted river restoration projects with a multitude of issues.
Restoration Planning and Implementation
Assessment, Planning and Permitting
The first step in restoration planning is typically a conceptual feasibility study or conceptual restoration plan. For these studies and plans, one or more sites are considered for restoration/rehabilitation with a number of technical assessments often needed to determine potential feasibility of projects and their design and implementation constraints. These studies also help in assessing the spatial scale and complexity of a potential project.
Consideration must be given to the project property limits (e.g., boundary survey and existing conditions map) and ownership (e.g., deed and title search). Are aerial photographs and topographic maps of the existing and/or past conditions available for the site? Are other sources available such as Environmental Assessments for the presence of contaminants or soils maps and geo-technical borings? As early as possible, potential constraints must be identified and input from regulatory and resource advisory agencies, project stakeholders and other interested parties on any significant issues associated with an anticipated project must be gathered. Public and stakeholder input, review and comment are critical to any informational meetings or any regulatory process hearing for restoration projects.
Various federal, state and local laws and regulations will apply to most river restoration projects. Evaluation of any regulatory constraints is essential early on, even though permit applications are not prepared and submitted until the later design phase. Permit processing sometimes requires significant time and cost. Environmental and land use constraints associated with projects may include:
- Federal, state, and/or locally-regulated wetlands;
- Federal Emergency Management Agency (FEMA) designated100-year floodplain and floodway where earth fill and structures are limited;
- Threatened or endangered species subject to the federal Endangered Species Act and/or state regulations;
- Historical and/or archaeological resources or features (e.g., dams subject to the National Historic Preservation Act (NHPA) or state regulations promulgated by the State Historic Preservation Office (SHPO) (or Tribal HPO on Native American lands);
- Contaminated sediments and hazardous waste (federal and/or state-regulated materials, e.g., asbestos tiles, sheeting, tires, lead paint, soils or sediments contaminated by lead, petroleum hydrocarbons) (See Adams et al.1992; Shelton and Capel 1994);
- Protected large "specimen" trees;
- Steep slopes regulated by municipal and/or county governments for disturbances;
- Other site features (e.g., buildings, utilities, walls, and bridges) that will potentially affect restoration work activities; and
- Off-site constraints upstream of a project area that may affect success of the project, such as water withdrawals (e.g., uncertainty of water availability), bridges (e.g., footing scour potential), and utility lines (e.g., buried pipes that could be exposed with headcutting).
Design and Cost Estimating
Once all essential assessment work is completed, project partners then transition into the design phase. Preliminary and final project designs are developed based on conceptual plans prepared during the feasibility study. Design work often involves a team with members from a number of technical disciplines, including licensed civil, structural, and hydraulic engineers (professional engineers - PEs), registered landscape architects (RLAs), and experienced ecologists and river geomorphologists.
Once a project is permitted by all regulatory agencies and final plans are completed, a plan, specifications, and details package is developed to solicit the contracting industry to bid on the construction. As part of the bid package, the project engineer or manager must develop a cost estimate for each project phase and specific activity. Costs are projected by professional engineers and cost estimators applying in-depth work experience and using standardized unit material and labor costs along with regional/municipal multipliers and other information available to the industry, particularly costs available through and updated annually by RS Means.
Costs are often one of the primary factors determining whether a restoration project moves forward to implementation. A collaborative approach by combining efforts of multiple partners is often required to secure adequate funds for costly restoration projects.
Restoration project construction is usually completed by private contractors, although for some sites, the U.S. military has undertaken and completed projects. Community-based groups and other volunteers may be the principal workforce for smaller-scale projects. Regardless of the workforce size and composition, a project or site manager with in-depth work experience and communication skills is essential to complete a project in a timely and cost efficient manner.
River restoration and fishway construction may include an array of equipment, laborers, and materials—whether pre-cast at an off-site location or poured in-place using forms. Excavators, backhoes, front-end loaders, cranes, or dump trucks may be needed to carry out on-site work and transport heavy loads to and from the site. Items such as temporary coffer dams, dewatering pumps, and siphon pipes are standard materials. Equipment and materials can be temporarily stored at on or off-site staging areas nearby during the project period.
The project work zone should be delineated by the project manager and contractor before any on-site work begins. Construction activities in and near streams should always be conducted in such a manner to avoid or minimize impacts to these stream and wetlands, and be in conformance with regulatory-approved project plans. Care must be taken to avoid disturbances to historic features that have been designated for protection, or if they are dismantled—such as an old dam—their internal structure should be documented by a qualified historian as it is removed.
The use of construction equipment mats and other best management practices applied in the forestry industry also help minimize damages to riparian vegetation and floodplain soils. The contractor should always employ best management practices for erosion and sediment control, noise (e.g., time of work periods) and dust control (e.g., site access road watering during extended dry periods), and other construction techniques that minimize disturbances of the site and to neighboring communities.
River and Stream Restoration Techniques
River and stream restoration involves the modification of a disturbed condition to re-establish physical channel and bank features of riparian plant communities bordering a particular river or stream reach. Numerous in-water and bank restoration techniques may be used, although NOAA Fisheries focuses on highest priority river restoration projects that are cost-effective, allow for unimpeded fish passage, and restore riverine ecological services.
Although a number of in-water and bank restoration techniques may be employed, the primary practices are described here:
Restoration of a river or stream channel requires that the project not only take into account the hydrology, hydraulics, and geomorphic conditions, but that the restoration activity result in no substantial physical barriers that prevent or impede fish from passing. Understanding and assessing channel dynamics is an essential component for channel reconstruction (See for example, Shields, Jr. et al. 2003). A number of structures can be constructed to address channel erosion and migration depending on the river characteristics. Examples include rock vanes, w-weirs, current deflectors, mid-channel deflectors, channel constrictors, cross-channel logs and revetments (See for example, Hunt 1993; Rosgen 1996). However, before any channel modifications to address erosion or deposition are proposed, upland watershed problems and processes (e.g., sub-division development, logging)must first be assessed. Correcting upstream problems is the first priority before any channel modifications are implemented.
Channel Structural Complexity
The addition of large woody debris (LWD) such as logs, stumps, boulders, and brush can provide cover habitat for fish to hide, substrate for macroinvertebrates to attach to or live on, and structure to vary flows and enhance diversity. Reports are available specifically addressing LWD (e.g., Fischenrich and Morrow, Jr. 2002; ODFW 1995).
This activity involves using plants, tree stumps and logs; synthetic geo-fabrics/textiles such as coir fiber logs and mats; stone and other materials to minimize erosion potential on regraded banks. A wide variety of geo-fabrics and textiles can be used by providing a temporary organic material cover material until a natural vegetation cover is established. Stream bank fencing, cattle guards, and in-stream techniques are also available (Hunt 1993).
Riparian and Wetland Planting and Seeding
Once a disturbed channel or its banks are regraded and stabilized and/or invasive plants are removed, the riparian zone and floodplain may be restored by planting native vegetation in association with installation of natural stone, logs or bioengineering materials. Plant materials may include native woody live cuttings purchased from a plant supplier or collected from a nearby donor site (if regulations allow). Live cuttings or stem sections typically 2 to 3 feet long are driven approximately three-quarters of their length into the soil in the early or late growing season and the cuttings sprout to grow new plants. Similarly, fascines (bundled woody plant cuttings)are installed in shallow trenches dug parallel to the stream channel and then covered with soil to encourage new plant growth. Brush mattresses, vegetated gabions, live crib walls, and vegetated geo-grids are other practices commonly employed. Woody plants—primarily balled and burlaped tree saplings and container pot seedlings or shrubs—are commonly installed along re-established riverbanks and in floodplains. Seeding with native wetland grasses or other herbaceous plants is also a common practice for stabilizing disturbed floodplain and bank soils, and is often done in association with the placement of geo-fabrics or hay mulching. Seeding of small sites is often done by hand or with rotary spreader; hydroseeding using water tank trucks and spray gun to release seed and tackifier is used on larger sites.
Of the restoration alternatives available to correct fish barriers caused by dams, NOAA generally prefers dam removal, as this restoration activity has the highest potential for improving fish passage and re-establishing other important riverine functions. Between 1996 and 2006, NOAA's Restoration Center provided funding and technical assistance to approximately 65 dam removal projects in the Northeast (Maine south through Virginia) alone, and we are actively collaborating on feasibility studies assessing the potential for other dam removals on the East Coast, West Coast, and Great Lakes. Through the Open Rivers Initiative (ORI), NOAA continues to specifically address dam removals that both restore fish passage and other riverine ecological services, and help contribute to the socio-economic vitality of our communities.
Removing a dam can have a significant effect on a river’s ecology. Dam removals have substantially increased in number across the United States since the early 1990s. Some East Coast states have established strong programs targeting dam removals as a preferred alternative for achieving restoration goals and for addressing dams in poor condition, of limited use, or limited value. The feasibility of dam removal depends on a number of factors including owner cooperation, dam length and height, dam hazard rating, potential for and extent of impounded contaminated sediments, historic designation of dam or its setting, presence of rare or endangered species, and recreational values of the impoundment. If these issues can be addressed, other project construction constraints also need to be assessed, such as the presence of onsite public utilities, vehicle equipment access, and options for temporary sediment stockpiling and disposal.
For some sites, partial dam removal or breach may be the preferred alternative if maintaining the impoundment is required (e.g., fire water supply), or removal of large quantities of sediment, particularly contaminated sediments, is infeasible. Partial removal by lowering the height of the dam structure may allow target fish species to pass over the structure, as well as re-establish other ecological river functions.
Several valuable publications addressing dam removal include:
- Dam Removal - A New Option for a New Century
- Dam Removal - Science and Decision-Making
- American River's Dam Removal Toolkit.
Where dams and other obstructions cannot be removed, fishways may be a viable alternative. Fishways, or "fish ladders," provide a series of pools or flow dissipaters in a sloped structure so fish can pass through, over, or around a blockage. Fish ladders are typically constructed of concrete, metal, wood, or other artificial materials.
All fishways are meant to function in a very similar manner. Adequate attraction flows are required to allow fish to find the entranceway to the fishway and stimulate the fish to move through the fishway to the exit and pass into the river or headpond above the dam. The entranceway must be properly sited below a dam that is also passing flows and possibly creating a hydraulic turbulence that may otherwise deter fish from using the fishway. Installation of fishways with proper bottom elevations or inverts of the entranceway and exit is essential to effective passage.
Proper fishway design requires adequate information on the target species' swimming capabilities, river flows during the period when the target species is expected to be on its river spawning migration, and detailed information on the elevations of headpond and tailwater.
River flow information is typically collected in the field over multiple dates at the project site for the expected operational period (normal upstream and downstream migration periods) by licensed surveyors and engineers, or calculated by hydraulic engineers who use flow gauging station data from other nearby, comparable rivers. The types of fishways most commonly used along the East Coast for upstream fish passage are:
- Alaskan steep passes - A series of baffles to dissipate flow velocities on streams and small rivers allowing fish to swim at burst speed through the pass. These fishways are typically constructed of pre-fabricated sheet aluminum with individual sections typically 10 feet long, 2 to 3 feet wide and 2 to 3.5 feet high. The grade of the slope varies according to the targeted fish species. For example, steep passes are often used on the East Coast with installation slopes (rise to run) of 1:4 to1:6 for river herring and with slopes of 1:8 for American shad.
- Bypass channels - Carry a minimum and controllable flow that allows fish to pass efficiently, but do not carry the dominant river flow. This alternative is only feasible if adequate lands bordering the river are available, particularly for high dams that require switchbacks in the bypass (see, for example, http://www.dnr.cornell.edu/research).
- Denil fishways - Used on large and medium-sized rivers, particularly those with highly variable flows, they are typically constructed as three-sided sloping poured concrete flumes with a series of wooden baffles shaped like window frames installed perpendicular to the water flow. These fishways may be more than 100 feet long, 10 feet wide, and 8 to 10 feet high.
- Eelways - Typically include the installation of three-sided wooden or metal troughs that extend from the tailwater into the headpond impoundment. The trough is lined with rough surface materials which eels can readily climb. The trough is covered with a protective mesh-netting to protect eels from birds and other predators. Water trickles down the eelway to keep the eel's gills and skin moist as they move up the trough.
- Fish elevators or lifts - Costly fishway alternatives, typically associated with large hydroelectric dams. Fish are attracted into a box trap which is mechanically lifted up along the dam, after which the fish are released into the impoundment. Fish elevators are located at the Conowingo Dam on the Susquehanna River in Pennsylvania and the Holyoke Dam on the Connecticut River in Massachusetts.
- Nature-like fishways - Constructed of natural, river-worn stone and other materials to provide passage. Nature-like fishways have been used primarily in Europe and, to a lesser extent, in Minnesota. American Rivers, a non-governmental organization (www.americanrivers.org) has a repository of information on nature-like fishways and other fish passage projects.
- Pool-and-weir fishways - Built on streams with very limited normal flows. Typically constructed out of concrete, the weirs include notches large enough for fish to pass through in a variety of flows. Fish rest in pools between two consecutive notched weirs.
- Roughened ramps - Also called rock rapids, they involve the placement of earth and stone below a dam, perched culvert, or partially removed dam. Fish pass by swimming up the earth and stone ramp. The ramp has a central low flow channel and is designed to accommodate varying flow velocities. These structures may be constructed across the entire or partial width of a river channel. Large keystones are placed to form weirs or chevrons that reduce velocities and provide resting sites on the ramp.
- Vertical slot fishways - A type of pool-and-weir fishway used on large rivers and for larger fish species—particularly Pacific salmon and steelhead in the Northwest. The design typically involves a series of weirs with one or two large vertical openings for fish to pass through, with resting areas between the weirs.
There is a variety of literature on the planning, design, maintenance, and costs of fishways. The technical content of these publications varies from those written more for the layperson (e.g., CRWC, Inc. 2000) to those for the experienced practicing engineer (e.g., Bell 1991; Clay 1995). Detailed information on nature-like fishways is also available (e.g., Gebbler et al.1998; Parasiewicz et al. 1998).
Culvert Removal or Replacement
For streams and rivers crossed by roads, road decommissioning combined with culvert removal is often the best way to restore riverine function and structure. Unfortunately, road decommissioning rarely occurs except in forests, parklands, and other remote areas where roads no longer serve a viable purpose.
If road decommissioning is not feasible, culvert modification or removal may still be practical and highly beneficial. Culverts should be installed at proper elevations and gradients to ensure fish passage for targeted species. Care must also be taken to prevent flow velocity barriers and physical blockages within culverts. There are multiple resources for culvert modification or removal design and practices:
- Washington Department of Fish and Wildlife's Fish Passage Technical Assistance(2003)
- Project SHARE's BMP Guidelines for Roads In Atlantic Salmon Watersheds(2004)
- NOAA's Guidelines for Salmonid Passage at Stream Crossings(2001)
- Oregon Department of Fish and Wildlife's Fish Passage Program
- Massachusetts Riverways Program
- Clay's Design of Fishways and Other Fish Facilities (1995)