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The STREAMS Channel Protection and Restoration Conference Posters(Click each poster title below for an abstract and contact information, or scroll down this page to read all.)
Poster Abstracts Analysis of Ecological Services provided by Blossom Way Creek, Rogers, Arkansas The city of Rogers, Arkansas is part of the rapidly growing Fayetteville-Springdale-Rogers metropolitan area of Northwest Arkansas. In June of 2003, the Milken Institute identified the area as having the top economic performance of cities in the United States. The natural resources of the area have been stressed as the cities struggle to develop infrastructure needed for the rapid growth. The water resources are particularly stressed because of increased pollutant loading from wastewater treatment plants, urban and agricultural nonpoint source pollution and loss of riparian zone vegetation. In 2002, the US EPA and the Arkansas Soil and Water Conservation Commission awarded a grant to the City of Rogers to demonstrate the environmental and economic benefits of using greenways in development of their drainage system. The demonstration stream is the Blossom Way Creek, a second order stream in the city draining roughly 16 km2. The upper half of the watershed has been fully developed as residential, industrial and commercial property. The lower half is currently being developed as single family residential property. The initial phase of the demonstration was to analyze the ecological services being provided by the stream in its present condition. Analysis included a habitat assessment, evaluation of the biodiversity, a tree survey, determination of land use and land use change in the watershed and analysis of the hydrologic/geomorphologic conditions in the stream. The project is unique in its combination of ecological sciences and engineering in the initial planning stages. Future phases of the project will include design and implementation of the greenway system; follow up analysis of ecological services and technology transfer elements. A local stakeholders committee consisting of the landowners, local educators, and interested citizens has been created to direct the project and extend the greenway concept to the rest of the area. return to listAn Evaluation of USGS Empirical Discharge Methods for Watersheds in Ohio The objectives of this study were to determine how runoff/discharge changes associated with land use alterations can be predicted by the USGS empirical discharge methods and to evaluate the performance of these methods on mixed land use watersheds in Ohio with variously sized drainage areas. These methods were developed for use on small watersheds that have drainage areas that are less than a few square miles. Using flow data from gaged watersheds in Ohio, we tested the USGS urban and rural equations for their usefulness as predictors of discharge for 2, 5, 10, 25, 50, and 100-year recurrence intervals. Inadequate data were available to test the methods for the small watershed sizes that were used to develop the equations. Therefore, the focus of our study was to determine if they could be used for larger areas and could provide useful estimates for land uses ranging from totally rural to totally urban. Results from this analysis indicated that in many cases the USGS urban equation provided reasonable peak-flood discharge estimates on both urban and rural watersheds ranging from a few square miles up to 35mi2. For this same size range, the USGS rural equation provided reasonable estimates less often than the urban equation. As watershed size increased (up to 100mi2) the USGS urban equation often provided reasonable estimates but the accuracy diminished as the size increased. Preliminary conclusions from this study indicate that a more accurate prediction of discharge on larger watersheds in Ohio may require the addition to the urban and rural equations of more variables that better characterize land use changes across the watershed. The USGS urban equation is of limited value when predicting runoff/discharge values on Ohio’s larger watersheds because: (1) these watersheds are mostly rural and the equation does not account for a totally rural condition; and (2) drainage, land slope, soil type, surface storage, impoundments and wetlands, and vegetation cover are important factors on these watersheds and are not considered in the method. The USGS rural equations are being enhanced by the USGS but details on their performance has not yet been reported and they have not yet been evaluated in our study. A limitation of the rural equations that were tested is that they do not account for land use change. return to listAttempts to Restore Degraded Stream Ecosystems: Lessons from the State of Indiana, USA Aquatic resource managers have attempted to restore stream ecosystems for decades, but limited information is available on approaches used to restore streams in the midwestern U.S. For the state of Indiana (USA), we conducted a survey of reach-scale restorations to determine restoration approaches, objectives, and degree of pre- and post-restoration assessment. Our survey suggests that streams are being restored for numerous reasons, including aesthetics, water quality improvement, and permitting requirements, but evaluations of these restorations are rare. Restored reaches had higher Qualitative Habitat Evaluation Index scores and lower width-depth ratios than did upstream degraded reaches, which suggests that current restoration approaches are effective at improving habitat quality. To better understand stream restoration practices in Indiana, we intensively evaluated one restoration (Juday Creek) for five years. Changes in habitat and water quality, periphyton, macroinvertebrates, and fishes were evaluated in the restored reaches and compared to unrestored reaches. Results suggest that an initial increase in habitat quality in restored reaches drove positive changes in higher trophic levels (i.e., macroinvertebrates and fishes), but over time differences between reach types diminished because sedimentation from upstream sources reduced habitat complexity in restored reaches. return to listBankfull Geometry Determinations in the Hocking River Basin of Ohio Natural stream channels are constructed and maintained by forces of the water and sediments of the watershed balanced against the resistance of bed and bank materials. Though the process of channel formation is complex, there are consistent quantifiable patterns for natural streams. These patterns form the basis of bankfull stage and discharge defined as the channel maintenance stage and discharge for a stream. Channel maintenance is most effective at the bankfull stage, while the associated discharge carrying sediment loads, forming and removing bars, and forming and changing bends results in average morphological characteristics of stream channels. Bankfull stage and its corresponding discharge are a useful measure in determining natural stream morphological characteristics for channel classification. This measure provides a valuable tool for assessing stable channel characteristics of natural streams. Bankfull channel dimensions for classifying and characterizing natural streams have been used in both regulatory programs and environmental impact analysis. To develop possible measures of relationship between the bankfull stage and the physical, geological, and meteorological conditions in the major regions of Ohio will greatly enhance the understanding of bankfull stage characteristics for classifying streams quantitatively. This will provide information to assess impacts of projects for modifying channels and a useful tool to design channels for minimizing these impacts. Natural stream channels are constructed and maintained by complex processes of their watersheds including waters and sediments. Though the formation process of a natural channel is complex, there are quantifiable and consistent patterns for the process, especially at the bankfull stage. The stability of a stream channel is generally defined as the ability to carry the water and sediment of its watershed while maintaining dimension, pattern, and profile without degrading or aggrading channel dimensions over time. However, any changes of geomorphic parameters will trigger adjustments in a channel to reach a new equilibrium. A geomorphic approach quantifies the physical characteristics of stream channels and identifies patterns common to a watershed or region. In this study, twelve sites whose drainage areas ranging from 7 to 120 square miles were selected for the bankfull geometry determinations including width, depth, cross-section area, bed slope, and drainage area. These form the basis to develop possible measures of relationship between the bankfull stage and the physical, meteorological, and geological conditions to enhance the understanding of bankfull stage characteristics for classifying streams quantitatively in the southeast region of Ohio. return to listBokes Creek Water Quality Enhancement Project Powderlick Run Channel Restoration The Bokes Creek Water Quality Enhancement Project promotes Natural Channel Design (NCD) methods to improve pollutant assimilation and water quality on Powderlick Run, a headwater stream in the Eastern Corn Belt Plains eco-region of Ohio. Powderlick Run is within the Bokes Creek Watershed, a major drinking water supply for the City of Columbus. This project demonstrates scientifically sound methods of restoring the hydrology and biology of modified stream channels while maintaining drainage benefits. Powder Lick Run is in non-attainment of it’s warm water habitat (WWH) designated use and this project concentrates on mitigating the water quality impairments which include nutrient enrichment, low dissolved oxygen associated with concentrated manure applications and extensive hydromodification. An Adaptive Management process was utilized in data collection and synthesis, design, implementation and the development of monitoring performance standards. The channel morphology and hydraulics of Powderlick Run was studied to determine baseline conditions. A comparison of baseline and reference reach data was made to define restoration goals and the morphological characteristics of the restored channel. A design-build approach took the project from data collection and design through construction of the channel and re-vegetation. This project is part of the Bokes Creek TMDL implementation plan and funded by a Section 319 Water Quality Implementation Grant from Ohio EPA. return to listConceptual Booth Run Stream Restoration Plan Booth Run is a 7.56-mile tributary to Pymatuning Creek in the Shenango River watershed. The Shenango Reservoir, located in the same watershed, is a source of drinking water and recreation for the public. Booth Run flows through natural areas and agricultural fields draining a 10.53-acre watershed along its 7.56-mile length. Land use changes and development have caused a slow but steady degradation of Booth Run and the reservoir. Mercer County Conservation District identified these issues and in the interest of improving water quality in the Shenango River watershed, secured a grant from the Growing Greener Program to fund this project. The goals of the Booth Run Stream Restoration Plan are to reduce sediment loading, and restore water quality to Booth Run and the Shenango Reservoir though corrective stream restoration measures. This study was conducted in two phases; 1.) Collection of biological and physical baseline data, and 2.) Baseline data analysis and restoration plan development. The objectives of this study were to identify and document present ecological conditions of Booth Run and its riparian area, characterize representative stream reaches utilizing Rosgen methodologies, identify areas of degradation, and provide techniques for restoration. Davey Resource Group utilized field data collection and analysis to determine the water quality of Booth Run. The recommendations from Phase One were to complete a vertical and horizontal survey of a reference segment of the stream and to calculate the final acreage for conservation easements in all reaches of the stream. Phase Two recommendations are to purchase conservation easements throughout many of the indicated enhancement areas, restore and construct a stable channel in Reach #2, and develop a final plan for restoration and stabilization of Reach #4. return to listDesign, Construction, and Post-Construction Monitoring for Relocation of 5,288 ft of Stream Channel in New Hartford, New York Stantec designed and constructed a total of 5,288 ft of new stream channel in 2000 to relocate a stream that supported a cool/warmwater fish community and a small population of juvenile brown trout. Extensive pre-design biological, morphological, and hydrologic studies were conducted in order to devise a natural channel relocation plan acceptable to the regulatory agencies. Natural channel design and bioengineering techniques were used to relocate the stream and integrate it with existing and new wetland areas. Extensive use of stream bank and bed protection methods such as concealed grade control structures, coconut fiber coir logs, native stone bed materials, erosion control matting, and native plant materials were used in the design. The new channel incorporated several design reaches including a cascade/pool reach to stabilize a steep grade section; a meandering Rosgen “C” channel through a sensitive woodlot/wetland; a meandering Rosgen “E” channel with several floodplain wetlands in the upper reach; and a series of floodplain wetlands to dissipate flood flows, collect groundwater, and provide water quality attenuation. The project was started in mid summer when site conditions were favorable for movement of construction equipment. However, the project was completed in late fall with minimal time for the floodplain grasses to become established. Following the first year of construction spring floodwaters overtopped the banks as designed and the bank erosion control materials functioned as intended. However, without the grass and root systems in place large volumes of topsoil was stripped from the floodway. Another design flaw was not mixing fines with the streambed stone throughout the pool/cascade section of the stream. In the area where they were not mixed water flows through the rocks in low-flow conditions. Post-construction monitoring in 2001 and 2002 shows that overall the new stream-channel is stable providing habitat for a diverse biotic community. return to listEvaluating the Link between Biology and Geomorphology in Forested Headwater Streams in Ohio About two-thirds of the streams in Ohio have drainage areas less than 1 square mile and have been classified by Ohio EPA as "primary headwater streams." Headwater streams supply the rest of the downstream drainage network with water, nutrients, energy, and biological inputs. These streams have historically been treated as structures to move water, and have been the victims of land use change on the watershed, and hydromodification in the form of straightening, widening and channelization. The Ohio EPA has developed a new method to evaluate the integrity of these primary headwater streams but the link between aquatic and terrestrial biology and stream geomorphology is unclear. The goal of the study was to better understand the factors that influence stream health in headwater streams and to determine if fluvial factors play a significant role. A study was conducted on 24 forested watershed in Ohio that have drainage areas of 0.1 to 5 square miles. The watersheds were located in three regions with distinctly different geology, soils, and groundwater contributions. Adverse anthropogenic impacts associated with surface mining, agricultural, and occupation of the land were generally small but varied considerably between the watersheds. At each site, data that was obtained included: drainage area; longitudinal profile along a reach that is at least 30 times the channel width; cross-sectional profile on representative pools and riffles; measurements of fluvial features that defined the main channel, floodplain, and pools and riffles; pebble count and measurement on bank and bar materials; field biological assessments (benthic macroinvertebrate index) in a representative pool and riffle; water quality (pH, DO, Conductivity, Temperature); Headwater Habitat Evaluation Index (HHEI) and Headwater Macroinvertebrate Field Evaluation Index (HMFEI). Preliminary results indicate that groundwater baseflow, depth to bedrock, substrate coarseness, riffle-pool features, and anthropogenic impacts were important factors. return to listGeomorphic Study of the Kalamazoo River, Michigan The restoration of natural flow regimes to rivers can have significant environ-mental and aesthetic benefits. In many cases, restoring the natural flow regime requires the removal of man-made structures that no longer serve their original purpose. A series of low-head dams exists on the Kalamazoo River between Plainwell and Allegan, Michigan. Most are in varying states of disrepair and are under consideration for removal. The removal of these structures is complicated due to a significant amount of polychlorinated biphenyl contamination present in the floodplain and in-stream sediments. The U.S. Environmental Protection Agency and Michigan Department of Environmental Quality have asked the U.S. Geological Survey to qualitatively describe the geomorphic condition, identify reaches that are prone to lateral migration, measure stream bank stability, and model stream bank and channel stability through a selected reach of the Kalamazoo River. The USGS analyzed stream banks digitized based on a time-series of aerial photographs and Government Land Office survey notes, performed geotechnical stream bank tests (in cooperation with the U.S. Department of Agriculture-Agricultural Research Service), and used a stream bank stability model to determine the conditions under which bank failures would occur. The USDA-ARS also assisted with developing a model of channel stability and the design of a stable channel configuration. Preliminary results indicate that historically the river has resisted significant widening, having maintained a fairly narrow channel. Although susceptible to undercutting, the stream banks are currently stable. Concerns of contamination contributed from the stream banks should focus more on sediment contributions from overland flow processes rather than stream bank failure. Furthermore, removal of any dam would result in the erosion of the in-stream sediments and are likely to impact dams located below the removal reach. return to listHydrological and Biogeochemical Investigations of Riparian Buffers in the Piedmont and Blue Ridge Regions of North Carolina NPS pollution has been identified as a major contributor to water quality degradation within most of the seventeen major river basins in North Carolina. The use of riparian, vegetated buffers has been identified as a Best Management Practice in controlling nitrogen, suspended sediment and to some degree phosphorus inputs into surface waters. The majority of the hydrological and biogeochemical investigations of riparian buffer functions have been carried out in the eastern regions of North Carolina. This research is assessing the effectiveness of vegetated riparian buffers in controlling the export of contaminants from agricultural operations to surface waters in the Piedmont and Blue Ridge regions of the state. The Piedmont site for this study is the Kiser Branch of Long Creek in the Catawba River Basin in Gaston County, NC. This site has been studied for eight years as a USEPA 319 Monitoring and BMP (best management practices) site. In 1996 a 50-ft. riparian buffer was planted along 2000 ft of the branch and was found to be effectively lowering amounts of sediment, bacteria and phosphorous entering local stream waters. However, nitrate (NO3-) concentrations in the stream and groundwater have remained elevated. The Blue Ridge site for this study is a beef cattle pasture adjacent to Nicholson Creek in Brevard, Transylvania County, North Carolina. The cattle were excluded and a 30-ft. riparian buffer was planted along an 800-ft reach of the creek in 1997. A detailed examination of the spatial and temporal transport of water and pollutants through both riparian zones was initiated in August, 2002. Piezometer nests with groundwater wells were installed at various locations and depths along two transects at each site. Sampling of the piezometers and wells has occurred every 14-28 days since installation. Water level, surface runoff, volumetric soil moisture, and recharge rate data have also been collected. Weather conditions at each site are recorded continuously via automatic weather stations. Water samples from each site are being analyzed for NH4+, NO3-, Cl-, TP, TKN, and fecal coliform. Here we present the hydrological conditions of the two sites including mineralogy, stratigraphy, hydraulic conductivity, as well as initial water quality patterns. return to listIdentifying and Correcting Man’s Impacts -- The West Fork Case The West Fork of the East Branch of the Black River, outside of Lodi, Ohio, has experienced increased sediments within the river during moderate to high flows which was of concern to the Medina County Park District and land owners along an 8000 lf stretch of river just south of Highway 224. Local landowners commented about increased velocities, frequency of flooding, and rates of bank erosion. Field investigations, maps and aerial photos indicated a moderately sinuous “C” type channel with gravel riffles and bars and silty sands in pools. The 40 square mile drains mostly farm fields and undeveloped wooded areas with a small commercial/industrial area on the west side of Lodi. A 1 to 2 year flow rate of 430 cfs resulted in a bankfull depth of about 4 feet, width of 50 to 60 feet and a velocity of 2-3 f/s which was consistent with field observations of gravel bars and vegetation. The existing eroding bank heights were not consistant with this data though. They varied from 5 to 6 feet at the upstream end and 10 to 12 feet at the downstream end. Initial conclusions were that much of the floodplain vegetaion had been cleared and farming operations had deposited significant sediment onto the floodplain raising elevations as much as 4 to 5 feet. The valley side slopes also narrowed which may contribute to the rising floodplain to stream bed difference. But some observations such as 100+ year old trees along the stream bank and soil cross sections not showing significant depositions indicated something else. Then we found the 1937 aerial photographs, used for creation of the Medina County Soil Survey, for the area now crossed by Highway 224 and our whole perspective regarding man’s impact on this river changed along with our recommendations for mitigation. return to listMiddle Cuyahoga River (MCR) Restoration Project - Kent, Ohio The Kent Dam located in the MCR is listed on the National Register of Historic Places. An OEPA TMDL study (1999) identified water quality problems within the Kent Dam pool. Currently, this reach of the MCR is considered by OEPA to be in non-attainment of its WWH classification. Low DO concentrations (1.75mg/l) have been measured. Aquatic habitat has been negatively altered in the dam pool, and the dam acts as a barrier to fish migration. To comply with OEPA TMDL requirements, the City must mitigate these degraded conditions. Goals: Modify the river to achieve the following criteria while preserving the dam:
Design Highlights: Instream Structures Fish Passage Response of Aquatic Invertebrates to a Stream Restoration in Northern Indiana Although stream habitat restoration is performed commonly as part of stream improvement and mitigation projects, the long term effectiveness of these efforts is poorly documented. Macroinvertebrate species richness and population densities, sediment deposition, and habitat quality were compared in restored and unrestored reaches of Juday Creek, a 3rd order cold water tributary of the St. Joseph River, in St. Joesph County, Indiana, from 1997 through 2002. The restoration included the relocation of two 320 m reaches of the stream into newly constructed channels, and the construction and maintenance of a sediment trap to protect the restored reaches. Between 1980 and 1992, stream invertebrate populations seriously deteriorated as a result of high rates of sedimentation due to changing land use and riparian management practices. The sediment trap has been effective at reducing levels of deposited sediments in downstream reaches, with maintenance activities having little impact on downstream conditions. Macroinvertebrate populations showed significantly higher densities and diversities in restored versus control stream reaches that have been sustained for 5 years following the restoration. return to listADAPTIVE MANAGEMENT STRATEGY The field of stream ecosystem restoration is a very complex and newly emerging (applied) science. We are currently using large sums of public moneys to restore public resources under very broad regulatory and scientific guidance. We commonly hear (and believe) that we must utilize a “Multi-disciplinary”, “holistic”, “systems” approach to managing and restoring our stream ecosystems (our environment). What does that mean? How can the regulated community work with the regulators to better accomplish this? We must develop an “Adaptive Management Process” within an ecosystem context that is born out of consensus to provide that much needed foundation from which restoration and management decisions will be based. This “process” involves managers, scientists and stakeholders who contribute to primary objectives and information needs for their project or resource. This “process” develops a set of techniques that integrate environmental issues with economic and social understanding. This “process” recognizes and targets an audience of practitioners who perform environmental assessment and the ability to communicate those results to senior administrators and policy makers. An Adaptive Management approach to project design and implementation provides advantages such as:
Adaptive Management attempts to deal with our limitations or inability to assess impacts to the environment as a means to produce and deliver better environmental outcomes such as strategies, goals and restoration projects. The goal of an Adaptive Management strategy is to develop a set of techniques to: (1) deal with uncertain information; (2) mobilize available data on partially known processes; and (3) assist with the "formation of objectives that are less sensitive to the unexpected. Adaptive Management emphasizes a systems approach and communication as the way to achieve a better, shared understanding of the problem. This implies a need to develop simplified models to better understand the behavior of the system. It also demands an emphasis on communication between practitioners in various disciplines and between researchers, practitioners and managers. This concept is not new and has been in practice across North America over the past 20 years. The Canadian’s adopted a national strategy of “Adaptive Management” for stream ecosystems in the late 1990’s. The US Forest Service has used an “adaptive management strategy” for forest management in the northwest for many years. The US Fish and Wildlife uses “adaptive management” in waterfowl management. According to Bernard T. Bowmann, US forest Service, “broad top down regulations are not likely to be effective until we foster creative local solutions, adapted to local conditions that emerge from structured learning and adapting experiences. Adaptive Management is probably the only alternative to ever-tightening regulations”. In this field of stream ecosystem restoration, we assume that we will acquire the “best available scientific knowledge” from “experts” at federal, state and local agencies, universities or private sector professionals to base our decisions upon. But that knowledge has proven to be disparate, at best, and disputed, at worst. Often what is “best scientific knowledge” for one person is “inadequate knowledge” or even “biased knowledge” for another. In addition, knowledge derived from experience (applied science) is often proprietary to those practicing professionals working in the field. Natural Channel theory has a large element of uncertainty. An Adaptive Management approach recognizes the lack of adequate:
Consider the barrage of scientific information that professional practitioners must face, sediment transport and competence, river continuum theory, biological criteria, channel evolution models, flow continuum models and the list goes on. Consider the complex list of problems such as urbanizing streams and watersheds, hydromodification, degraded habitat, water quality. These are all recognized problems, but how serious and synergistic are these and how can we best develop restoration and management schemes to address them? It seems clear that the “best available scientific knowledge” is somewhat elusive and is not necessary “applied” knowledge derived from project experience and management adaptation. Over time, various models have been developed and tested and there are many philosophies of modeling (e.g. river continuum, classification). Most of these are useful, perhaps essential to support decision-making in stream ecosystem management. However, none is complete enough to serve as the sole decision support tool for our restoration efforts. The various models do a reasonable job of ranking the expected benefits of management alternatives, and decision-makers would be well served by drawing on all the available analytical tools from the various disciplines. The concept of “adaptive management” has grown from this frustration with disparate scientific knowledge, the lack of integration between disciplines and the inability to communicate effectively with decision makers. Many believe that ecosystem restoration requires scientific skepticism. That fish and wildlife recovery should be seen as a series of experiments. Through monitoring and evaluation of these experiments, we should begin to learn what works and what doesn’t, effectively communicate our findings and then focus our investments on those experiments, and elements of experiments, that show promise. Attempts to implement adaptive management approaches have revealed many challenges. Second, it is difficult, if not impossible, to manage these problems experimentally, yet that is what adaptive management would have us do. The scientific method would have us limit or withhold variables and then monitor the results. Yet, we cannot control natural forces like weather conditions under natural and changing conditions. Success may need to be measured by trends, or at very exaggerated and different temperate scales. Third, adaptive management often leads us to spend money on efforts that might fail. Adaptive management by definition assumes that you have questions that need answers, and the adaptive management process allows you to construct experiments in the face of that uncertainty. But obviously there is an element of risk. To help us proceed in the face of uncertainty, which is a polite word for ignorance, we must learn some important lessons about adaptive management from the past 20 years, most importantly that adaptive management provides a different approach to managing public resources because it:
In short, “adaptive management” brings together the state of practice, science, and governance. Adaptive management allows us to learn by doing through communication between the disciplines. That is the essence of adaptive management. Bankfull Characteristics of Ohio Streams and Their Relation to Peak Streamflows In addition to its obvious importance for flood awareness, the stage at which a stream first overflows its natural banks is important, because flows at or near bankfull stage tend to move the most sediment over the long term and thus are highly influential in forming the main channel. When relocating a stream or reconstructing a stream crossing, good estimates of natural-channel dimensions are needed so that a stable stream channel can be designed. The U.S. Geological Survey (USGS), in cooperation with the Ohio Department of Transportation and the U.S. Department of Transportation, Federal Highway Administration, is conducting a study whose objectives are to (1) collect geomorphic data for a variety of Ohio stream sites to obtain a representative sampling of physical, geological, and meteorological settings, (2) regionalize selected geomorphic characteristics, including mean bankfull depth, bankfull area, and bankfull width, and (3) relate selected geomorphic characteristics to flood-frequency information. Because natural streams channels in Ohio are scarce (particularly at streamflow-gaging stations), 230 potential study sites were map- and field-checked in order to identify the 50 sites needed for the study. Horizontal- and vertical-control surveys were conducted and bed and bank materials were sampled at each the 50 study sites. The site data were plotted and analyzed to compute geomorphic characteristics, estimate bankfull discharges, and quantify bed- and bank-material particle-size distributions. Development of regional curves and multiple-regression equations for estimating bankfull width, depth, cross-sectional area, discharge, and flood-discharge-frequency curves are in progress. Dimensions of natural streams traditionally have been estimated by means of regional curves as a function of drainage area only, such as those developed by Dunne and Leopold in the 1970s. The data used to construct these curves are unpublished, thus the prediction errors associated with the curves is unknown. There is considerable variance in the relations between drainage area and bankfull dimensions. Preliminary multiple-regression analyses relating bankfull dimensions to selected explanatory variables indicate that much of the variance can be explained by factors such as channel slope, bed material composition, and climate. Therefore, estimates based on multiple-regression equations may be significantly more accurate than those based on drainage-area-only regional curves, particularly for basins having very high or very low gradients. Also, preliminary analyses indicate that estimates of flood-discharge-frequency curves for small drainage areas (which generally have the greatest prediction errors) may be significantly improved by the use of bankfull-characteristic-based equations instead of the more traditional basin-characteristic-based equations. |
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