Water: Coastal Zone Act Reauthorization Amendments
B. Instream and Riparian Habitat Restoration Management Measure
- Evaluate the potential effects of proposed channelization and channel modification on instream and riparian habitat in coastal areas;
- Plan and design channelization and channel modification to reduce undesirable impacts; and
- Develop an operation and maintenance program with specific timetables for existing modified channels that includes identification of opportunities to restore instream and riparian habitat in those channels.
This management measure pertains to surface waters where channelization and channel modification have altered or have the potential to alter instream and riparian habitat such that historically present fish or wildlife are adversely affected. This management measure is intended to apply to any proposed channelization or channel modification project to determine changes in instream and riparian habitat and to existing modified channels to evaluate possible improvements to instream and riparian habitat. Under the Coastal Zone Act Reauthorization Amendments of 1990, States are subject to a number of requirements as they develop coastal NPS programs in conformity with management measures and will have some flexibility in doing so. The application of this management measure by States is described more fully in Coastal Nonpoint Pollution Control Program: Program Development and Approval Guidance, published jointly by the U.S. Environmental Protection Agency (EPA) and the National Oceanic and Atmospheric Administration (NOAA) of the U.S. Department of Commerce.
The purpose of this management measure is to correct or prevent detrimental changes to instream and riparian habitat from the impacts of channelization and channel modification projects. Implementation of this management measure is intended to occur concurrently with the implementation of Management Measure A (Physical and Chemical Characteristics of Surface Waters) of this section.
Contact between floodwaters and overbank soil and vegetation can be increased by a combination of setback levees and use of compound-channel designs. Levees set back away from the streambank (setback levees) can be constructed to allow for overbank flooding, which provides surface water contact to important streamside areas (including wetlands and riparian areas). Additionally, setback levees still function to protect adjacent property from flood damage. Compound-channel designs consist of an incised, narrow channel to carry surface water during low (base)-flow periods, a staged overbank area into which the flow can expand during design flow events, and an extended overbank area, sometimes with meanders, for high-flow events. Planting of the extended overbank with suitable vegetation completes the design.
Preservation of ecosystem benefits can be achieved by site-specific design to obtain predefined optimum or existing ranges of physical environmental conditions. Mathematical models can be used to assist in site-specific design. Instream and riparian habitat alterations caused by secondary effects can be evaluated by the use of models and other decision aids in the design process of a channelization and channel modification activity. After using models to evaluate secondary effects, restoration programs can be established.
Selection of this management measure was based on the following factors:
- Published case studies that show that channelization projects cause instream and riparian habitat degradation. For example, wetland drainage due to hydraulic modifications was found to be significant by several researchers (Barclay, 1980; Erickson et al., 1979; Schoof, 1980; Wilcock and Essery, 1991).
- Published case studies that note instream habitat changes caused by channelization and channel modifications (Reiser et al., 1985; Sandheinrich and Atchison, 1986).
As explained more fully at the beginning of this chapter and in Chapter 1, the following practices are described for illustrative purposes only. State programs need not require implementation of practices. However, as a practical matter, EPA anticipates that the management measure set forth above generally will be implemented by applying one or more management practices appropriate to the source, location, and climate. The practices set forth below have been found by EPA to be representative of the types of practices that can be applied successfully to achieve the management measure described above.
- a. Use models/methodologies to evaluate the effects of proposed channelization and channel modification projects on instream and riparian habitat and to determine the effects after such projects are implemented.
Expert Judgment and Check Lists
Approaches using expert judgment and check lists developed based on experience acquired in previous projects and case studies may be very helpful in integrating environmental goals into project development. This concept of incorporating environmental goals into project design was used by the U.S. Army Corps of Engineers (Shields and Schaefer, 1990) in the development of a computer-based system for the environmental design of waterways (ENDOW). The system is composed of three modules: streambank protection module, flood control channel module, and streamside levee module. The three modules require the definition of the pertinent environmental goals to be considered in the identification of design features.
Depending on the environmental goals selected for each module, ENDOW will display a list of comments or cautions about anticipated impacts and other precautions to be taken into account in the design.
To assess the biological impacts of channelization, it is necessary to evaluate both physical and biological attributes of the stream system. Assessment studies should be performed before and after channel modification, with samples being collected upstream from, within, and downstream from the modified reach to allow characterization of baseline conditions. It is also desirable to identify and sample a reference site within the same ecoregion as part of the rapid bioassessment procedures discussed below.
Habitat Evaluation Procedures
Habitat Evaluation Procedures (HEPs) can be used to document the quality and quantity of available habitat, including aquatic habitat, for selected wildlife species. HEPs provide information for two general types of instream and riparian habitat comparisons:
- The relative value of different areas at the same point in time and
- The relative value of the same area at future points in time.
By combining the two types of comparisons, the impact of proposed or anticipated land and water use changes on instream and riparian habitat can be quantified (USDOI-FWS, 1980).
Rapid Bioassessment Protocols - Habitat Assessment
Rapid Bioassessment Protocols (RBPs) were developed as inexpensive screening tools for determining whether a stream is supporting a designated aquatic life use (Plafkin et al., 1989). One component of these protocols is an instream habitat assessment procedure that measures physical characteristics of the stream reach (Barbour and Stribling, 1991). An assessment of instream habitat quality based on 12 instream habitat parameters is performed in comparison to conditions at a "reference" site, which represents the "best attainable" instream habitat in nearby streams similar to the one being studied. The RBP habitat assessment procedure has been used in a number of locations across the United States. The procedure typically can be performed by a field crew of one person in approximately 20 minutes per sampling site.
Rapid Bioassessment Protocol III - Benthic Macroinvertebrates
Rapid Bioassessment Protocols (Plafkin et al., 1989) were designed to be scientifically valid and cost-effective and to offer rapid return of results and assessments. Protocol III (RBP III) focuses on quantitative sampling of benthic macroinvertebrates in riffle/run habitat or on other submerged, fixed structures (e.g., boulders, logs, bridge abutments, etc.) where such riffles may not be available. The data collected are used to calculate various metrics pertaining to benthic community structure, community balance, and functional feeding groups. The metrics are assigned scores and compared to biological conditions as described by either an ecoregional reference database or site-specific reference sites chosen to represent the "best attainable" biological community in similarly sized streams. In conjunction with the instream habitat quality assessment, an overall assessment of the biological and instream habitat quality at the site is derived. RBP III can be used to determine spatial and temporal differences in the modified stream reach. Application of RBP III requires a crew of two persons; field collections and lab processing require 4 to 7 hours per station and data analysis about 3 to 5 hours, totaling 7 to 12 hours per station. The RBP III has been extensively applied across the United States.
Rosgen Stream Classification System - Fish Habitat
Rosgen (1985) has developed a stream classification system that categorizes various stream types by morphological characteristics. Based on characteristics such as gradient, sinuosity, width/depth ratio, bed particle size, channel entrenchment/valley confinement, and landform features and watershed soil types, stream segments can be placed within major categories. Subcategories can be delineated using additional factors including organic debris, riparian vegetation, stream size, flow regimen, depositional features, and meander patterns. The method is designed to be applied using aerial photographs and topographic maps, with field validation necessary for gradients, particle size, and width/depth ratios. Rosgen and Fittante (1986) have prepared guidelines for fish habitat improvement structure suitability based on Rosgen's (1985) classification system. The methods have been used in the western States and have had some application in the eastern States.
Simon and Hupp Channel Response Model - Stream Habitat
A conceptual model of channel evolution in response to channelization has been developed by Simon and Hupp (1986, 1987), Hupp and Simon (1986, 1991), and Simon (1989a, 1989b). The model identifies six geomorphic stages of channel response and was developed and extensively applied to predict empirically stream channel changes following large-scale channelization projects in western Tennessee. Data required for model application include bed elevation and gradient, channel top-width, and channel length before, during, and after modification. Gauging station data can be used to evaluate changes through time of the stage-discharge relationship and bed-level trends. Riparian vegetation is dated to provide ages of various geomorphic surfaces and thereby to deduce the temporal stability of a reach.
Stream temperature has been widely studied, and heat transfer is one of the better-understood processes in natural watershed systems. Most available approaches use energy balance formulations based on the physical processes of heat transfer to describe and predict changes in stream temperature. The six primary processes that transfer energy in the stream environment are (1) short-wave solar radiation, (2) long-wave solar radiation, (3) convection with the air, (4) evaporation, (5) conduction to the soil, and (6) advection from incoming water sources (e.g., ground-water seepage).
Several computer models that predict instream water temperature are currently available. These models vary in the complexity of detail with which site characteristics, including meteorology, hydrology, stream geometry, and riparian vegetation, are described. An instream surface water temperature model was developed by the U.S. Fish and Wildlife Service (Theurer et al., 1984) to predict mean daily temperature and diurnal fluctuations in surface water temperatures throughout a stream system. The model can be applied to any size watershed or river system. This predictive model uses either historical or synthetic hydrological, meteorological, and stream geometry characteristics to describe the ambient conditions. The purpose of the model is to predict the longitudinal temperature and its temporal variations. The instream surface water temperature model has been used satisfactorily to evaluate the impacts of riparian vegetation, reservoir releases, and stream withdrawal and returns on surface water temperature. In the Upper Colorado River Basin, the model was used to study the impact of temperature on endangered species (Theurer et al., 1982). It also has been used in smaller ungauged watersheds to study the impacts of riparian vegetation on salmonid habitat.
Index of Biological Integrity - Fish Habitat
Karr et al. (1986) describe an Index of Biological Integrity (IBI), which includes 12 matrices in three major categories of fish assemblage attributes: species composition, trophic composition, and fish abundance and condition. Data are collected at each site and compared to those collected at regional reference sites with relatively unimpacted biological conditions. A numerical rating is assigned to each metric based on its degree of agreement with expectations of biological condition provided by the reference sites. The sum of the metric ratings yields an overall score for the site. Application of the IBI requires a crew of two persons; field collections require 2 to 15 hours per station and data analysis about 1 to 2 hours, totaling 3 to 17 hours per station. The IBI, which was originally developed for Midwestern streams, can be readily adapted for use in other regions. It has been used in over two dozen States across the country to assess a wide range of impacts in streams and rivers.
Simon and Hupp Vegetative Recovery Model - Streamside Habitat
A component of Simon and Hupp's (1986, 1987) channel response model is the identification of specific groups of woody plants associated with each of the six geomorphic channel response stages. Their findings for western Tennessee streams suggest that the site preference or avoidance patterns of selected tree species allow their use as indicators of specific bank conditions. This method might require calibration for specific regions of the United States to account for differences in riparian zone plant communities, but it would allow simple vegetative reconnaissance of an area to be used for a preliminary estimate of stream recovery stage (Simon and Hupp, 1987).
- b. Identify and evaluate appropriate BMPs for use in the design of proposed channelization or channel modification projects or in the operation and maintenance program of existing projects. Identify and evaluate positive and negative impacts of selected BMPs and include costs.
Operation and maintenance programs should include provisions to use one or more of the approaches described under Practice "b" of Management Measure A of this section. To prevent future impacts to instream or riparian habitat or to solve current problems caused by channelization or channel modification projects, include one or more of the following in an operation and maintenance program:
- Streambed protection;
- Levee protection;
- Channel stabilization and flow restrictors;
- Check dams;
- Vegetative cover;
- Instream sediment load control;
- Noneroding roadways; and
- Setback levees and flood walls.
Operation and maintenance programs should weigh the benefits of including practices such as these for mitigating any current or future impairments to instream or riparian habitat.