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Streams & Rivers Monitoring
The completion of construction is often thought of as the final step of a restoration project, but is only the beginning of the next phase: monitoring to assess success and determine if corrective actions are needed. Site monitoring, preferably for at least three to five years, is important to evaluate progress and document ecological changes that lag in response to restoration activities.
Monitoring Structural and Functional Characteristics
NOAA has identified the need for monitoring of structural and functional attributes of restoration sites in a two-volume set (Thayer et al. 2003, 2005) which covers primarily coastal habitats, but includes riverine forest communities.
Structural characteristics to monitor:
- Stream channel - using survey level to map channel bottom elevations in a regularly spaced series and along multiple sections across the project area stream reach in relation to a known or relative vertical reference datum
- Sediment - grab samples from sites within the restored stream reach to document grain-size over time
- Riparian vegetation - sampling from regularly spaced areas perpendicular to the stream centerline throughout the project area over an extended time period
- Percent canopy cover over stream - establish sampling stations or belt transects and monitor cover over time
- Presence and abundance of large woody debris along a specified stream reach length
Functional characteristics to monitor:
- Fish sampling - to identify species presence, abundance and assemblage composition using seines, hand nets, snorkeling, or electrofishing - the techniques should be able to quantify the fish use for a unit area or specified time period;
- Aquatic macroinvertebrate sampling - using Surber sampler or kick-net for a unit stream bottom area, usually in riffle habitat to identify species abundance, diversity, and community composition;
- Bird surveys - using station counts and amphibian and reptile surveys using fence arrays and pit fall traps to quantify riparian habitat use;
- Surveys of riparian trees and shrubs - to document the production of seeds, acorns, and other mast production as food for wildlife; and
- Measuring in-stream temperatures - to document water quality due to increased canopy cover and in-stream structure.
Both pre- and post-restoration monitoring of project sites should be completed to document changes and examine trends and performance that result from a specific restoration activity. Concurrent monitoring of one or more nearby reference sites can also be undertaken to differentiate changes in the restoration site attributable to the restoration activity versus normal environmental variability affecting the region. Monitoring periods will vary depending on the type and scale of the project and availability of monitors and monitoring budget; however, three to five years of data are typical for restoration projects with analysis to be completed by experienced ecologists and biologists.
Monitoring Riparian and In-stream Restoration
Monitoring of restored riparian and floodplain wetland habitats generally involves the collection of vegetation, hydrologic, and/or soils data to help in quantifying structure and qualifying ecological functions. Permanent field monitoring plots along one or more transects parallel to the floodplain slope and hydraulic gradient are commonly used in completing assessments of plant community re-colonization, percent cover, and dominant plant species. Photograph stations are also important for documenting vegetation conditions. The number of plots and distance between plots and along transects is dependent on the project site area and variability. Direct counts and inspections of plantings can also be completed to assess survivorship and condition of plantings over time, but if a large number of plants are installed or seeding occurs over a large area, monitoring plots may also used. The monitoring period for assessing vegetation is best done during the peak of the growing season. Vegetation monitoring methods may be similar to those applied for wetland delineations (See for example - Environmental Laboratory 1987).
Riparian hydrology can be documented by using staff gages or automated data loggers tied into a known elevation datum to record changes in surface water elevations seasonally and inter-annually. Groundwater wells are also often installed to measure changes in sub-surface elevation, as well as groundwater quality characteristics.
In-stream monitoring often involves field surveys by professional surveyors and geomorphologists to document changes in stream cross-sections and channel longitudinal profiles along the thalweg by comparing pre- to post-restoration conditions. Other in-stream habitat measurements may include qualifying structural development associated with large woody debris and other materials, delineating streambed features, and sediment size distribution and embeddedness.
Monitoring Fish Passage Restoration
Passage efficiency is an important concept for defining how well a fishway or other river restoration project is performing relative to fish passage, and is influenced by the target species' behavioral traits, and fishway type, design and construction. No fishway is 100 percent efficient, although dam removals or river restoration that re-establishes unimpeded movement and migration through the channel will achieve or approach complete passage providing there are no physical or flow velocity barriers resulting from the project. Passage efficiency can be quantified or qualified during the fishway's operational period applying visual monitoring, electronic fish counters, above river and/or underwater video, and telemetry (radio or acoustic monitors). Sensor PIT tags installed into live fish and then returned to the river are used in conjunction with antennae and continuous data loggers. Information obtained can be used to assess the functioning of fishway attraction flows, overall passage efficiency through a restored area, and the time for the fish to pass the structure or restored river reach. As an example of this type of performance monitoring, NOAA's Restoration Center has been working with the U.S. Geological Survey (USGS) conducting acoustic studies at nature-like structures installed in the Northeast, as well as testing nature-like fishway designs at the USGS Conte Anadromous Fish Research Library in Turners Falls, Massachusetts.
Telemetry is also used for conducting a variety of fish behavior and physiology studies to evaluate effectiveness of fishways at dams or assess the bio-energetic expense to fishes at a swimming impediment (e.g., hydroelectric facility). This work is conducted by trained and experienced fishery biologists. Data that can be collected using telemetric methods includes:
- location and movement of fish in rivers
- in-stream temperatures
- physiological data
- fish mortality
- historical data
- 3-dimensional mapping where fish can be detected with high accuracy.
Keeping good records of fish passage monitoring data is vital to restoration programs. An example of a monitoring program regularly collecting diadromous fish run data is the Connecticut Department of Environmental Protection's (CTDEP) Inland Fisheries Program which maintains a web site and list serve available to the public. Such data can be used to compare and contrast numbers of fish for various years as a means to assess the performance or progress of a passage project, as well as provide important information to the public on a restoration project.
Watershed Level Monitoring
Although such monitoring is not often necessary for small projects, watershed level monitoring can be useful to demonstrate the success of larger projects and restoration programs. The use of a chronological series of aerial photographs to document and compare geomorphic changes and plant community responses over time is one relatively low-cost technique, but requires skill in photographic interpretation and typically involves ground-truthing and field survey measurements to examine actual site conditions. Mapping—using GIS (geographic information system) software packages—is a common practice today and facilitates the assessment of large aerial coverage and data sets using multiple environmental and land use data layers.