首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 109 毫秒
1.
Abstract: Regional curves, which relate bankfull channel dimensions and discharge to watershed drainage area, are developed to aid in identifying the bankfull stage in ungaged watersheds, and estimating the bankfull discharge and dimensions for river studies and natural channel design applications. This study assessed 26 stable stream reaches in two hydro‐physiographic regions of the Florida Coastal Plain: the Northwest Florida Coastal Plain (NWFCP) and the North Florida Coastal Plain (NFCP). Data from stream reaches in Georgia and Alabama were also used to develop the Florida regional curves, since they are located in the same hydro‐physiographic region. Reaches were selected based on the presence of U.S. Geological Survey gage stations and indicators of limited watershed development (e.g., <10% impervious surface). Analyses were conducted to determine bankfull channel dimensions, bankfull discharge, average channel slope, and Rosgen stream classification. Based on these data, significant relationships were found between bankfull cross‐sectional area, width, mean depth, and discharge as a function of drainage area for both regions. Data from this study suggested that bankfull discharges and channel dimensions were larger from NWFCP streams than from Coastal Plain streams in North Carolina and Maryland. Bankfull discharges were similar between NFCP and Georgia coastal plain streams; therefore, the data were combined into one regional curve. In addition, the data were stratified by Rosgen stream type. This stratification strengthened the relationships of bankfull width and mean depth as a function of drainage area.  相似文献   

2.
Brockman, Ruth R., Carmen T. Agouridis, Stephen R. Workman, Lindell E. Ormsbee, and Alex W. Fogle, 2012. Bankfull Regional Curves for the Inner and Outer Bluegrass Regions of Kentucky. Journal of the American Water Resources Association (JAWRA) 48(2): 391‐406. DOI: 10.1111/j.1752‐1688.2011.00621.x Abstract: Bankfull regional curves that relate channel dimensions and discharge to watershed drainage area are useful tools for assisting in the correct identification of bankfull elevation and in stream restoration and reconstruction. This study assessed 28 stable streams located in two physiographic regions of Kentucky: the Inner Bluegrass and the Outer Bluegrass. Bankfull channel dimensions, discharge, and return period as well as average channel slope, median bed material size, sinuosity, Rosgen stream classification, and percent impervious area were determined. Significant relationships were found between drainage area and the bankfull characteristics of cross‐sectional area, width, mean depth, and discharge for both the Inner Bluegrass and Outer Bluegrass regions (α = 0.05). It was also found that the percent impervious area in a watershed had minimal effect on bankfull dimensions, which is attributed to the well‐vegetated nature of the streambanks, cohesive streambank materials, and bedrock control. No significant differences between any of the Inner Bluegrass and Outer Bluegrass regional curves were found (α = 0.05). Comparisons were made between the Inner Bluegrass and Outer Bluegrass curves and others developed in karst‐influenced areas in the Eastern United States. Although few significant differences were found between the regional curves for bankfull discharge and width, a number of the curves differed with regards to bankfull cross‐sectional area and mean depth.  相似文献   

3.
ABSTRACT: Rosgen analysis, developed for assessing channel stability in streams from the western United States, is applied to the Oswego River watershed in the New Jersey Pine Barrens. The Rosgen method requires calibration to local conditions due to the impact of peat substrates on channel morphology. In particular, the presence of peat induces low width to depth ratios and greater channel confinement, reversing typical downstream morphologic trends observed in other rivers. Therefore peat is added to those substrates already evaluated by Rosgen. A consistent sequence of Rosgen stream types develops along the Oswego River and its tributaries created by spatially overlapping processes of water table emergence, peat development, and channel formation. This sequence delineates a “natural” transition of stream channel morphology downslope through the watershed. First, as the water table reaches the surface of dry sloughs, Sphagnum growth is stimulated and peat substrates result. These substrates have lower permeability than the underlying gravelly sands. Next, surface runoff, through braided pathways over the peat, eventually erodes mainly anastomosing channels into the peat. Finally, single‐thread channels develop in underlying gravelly sands further downslope. This downslope sequence, expressed as Rosgen stream types, begins generally with DA7 streams arising from dry sloughs. These pass to E7, C7 or DA5 stream types that in turn pass to B5c, C5 and C4 stream types. Departures from the “natural” stream type sequence occur along the course of the Oswego and its tributaries due to human activities such as the construction of dams, bridges and drainage ditches, stream bank erosion at streamside camping and picnic areas and the clear‐cutting of adjacent stands of Atlantic white cedar.  相似文献   

4.
Abstract: Stream and riparian managers must effectively allocate limited financial and personnel resources to monitor and manage riparian ecosystems. They need to use management strategies and monitoring methods that are compatible with their objectives and the response potential of each stream reach. Our objective is to help others set realistic management objectives by comparing results from different methods used to document riparian recovery across a diversity of stream types. The Bureau of Land Management Elko Field Office, Nevada, used stream survey, riparian proper functioning condition (PFC) assessment, repeat photographic analysis, and stream and ecological classification to study 10 streams within the Marys River watershed of northeast Nevada during all or parts of 20 years. Most riparian areas improved significantly from 1979 to 1992‐1993 and then additionally by 1997‐2000. Improvements were observed in riparian and habitat condition indices, bank cover, and stability, pool quality, bank angle, and depth of undercut bank. Interpretation of repeat photography generally confirmed results from stream survey and should be part of long‐term riparian monitoring. More attributes of Rosgen stream types C and E improved than of types B and F. A and Gc streams did not show significant improvement. Alluvial draws and alluvial valleys improved in more ways than V‐erosional canyons and especially V‐depositional canyons. Stream survey data could not be substituted for riparian PFC assessment. Riparian PFC assessments help interpret other data.  相似文献   

5.
6.
Mulvihill, Christiane I. and Barry P. Baldigo, 2012. Optimizing Bankfull Discharge and Hydraulic Geometry Relations for Streams in New York State. Journal of the American Water Resources Association (JAWRA) 48(3): 449-463. DOI: 10.1111/j.1752-1688.2011.00623.x Abstract: This study analyzes how various data stratification schemes can be used to optimize the accuracy and utility of regional hydraulic geometry (HG) models of bankfull discharge, width, depth, and cross-sectional area for streams in New York. Topographic surveys and discharge records from 281 cross sections at 82 gaging stations with drainage areas of 0.52-396 square miles were used to create log-log regressions of region-based relations between bankfull HG metrics and drainage area. The success with which regional models distinguished unique bankfull discharge and HG patterns was assessed by comparing each regional model to those for all other regions and a pooled statewide model. Gages were also stratified (grouped) by mean annual runoff (MAR), Rosgen stream type, and water-surface slope to test if these models were better predictors of HG to drainage area relations. Bankfull discharge models for Regions 4 and 7 were outside the 95% confidence interval bands of the statewide model, and bankfull width, depth, and cross-sectional area models for Region 3 differed significantly (p < 0.05) from those of other regions. This study found that statewide relations between drainage area and HG were strongest when data were stratified by hydrologic region, but that co-variable models could yield more accurate HG estimates in some local regional curve applications.  相似文献   

7.
Procopio, Nicholas A., 2010. Hydrologic and Morphologic Variability of Streams With Different Cranberry Agriculture Histories, Southern New Jersey, United States. Journal of the American Water Resources Association (JAWRA) 46(3):527-540. DOI: 10.1111/j.1752-1688.2010.00432.x Abstract: The creation of reservoirs and the modification of stream channels are common practices used to facilitate the efficient production of cranberries. The potential impacts to hydrologic and geomorphic aspects of streamflow and channel structure have not been adequately assessed. In this study, the streamflow regime of 12 streams and the channel morphologies of 11 streams were compared for study sites in the Pinelands region of New Jersey with upstream active-cranberry bogs, upstream abandoned-cranberry bogs, and basins with no apparent agricultural history. Flow regime metrics included measures of low-flow, median-flow, and bankfull discharge, two measures of streamflow variability (spread and a modified Richards-Baker Flashiness index), and the frequency of overbank flooding. Stream-channel morphology metrics included average bank slope, average bankfull width, average bankfull depth, average bankfull width-to-depth ratio, and average bankfull area. No significant differences between stream types were apparent for any of the metrics. Basin-area normalized streamflow values of all 12 study sites were highly correlated to each other. Significant relationships existed between some of the flow-regime and channel-morphology metrics. Due to the lack of significant differences between stream types, it appears that neither historic nor current cranberry agricultural practices considerably influence flow regimes or the channel morphology of streams in the New Jersey Pinelands.  相似文献   

8.
Abstract: Stream monitoring programs commonly measure physical attributes to assess the effect of land management on stream habitat. Variability associated with the measurement of these attributes has been linked to a number of factors, but few studies have evaluated variability due to differences in protocols. We compared six protocols, five used by the U.S. Department of Agriculture Forest Service and one by the U.S. Environmental Protection Agency, on six streams in Oregon and Idaho to determine whether differences in protocol affect values for 10 physical stream attributes. Results from Oregon and Idaho were combined for groups participating in both states, with significant differences in attribute means for 9 out of the 10 stream attributes. Significant differences occurred in 5 of 10 in Idaho, and 10 of 10 in Oregon. Coefficients of variation, signal‐to‐noise ratio, and root mean square error were used to evaluate measurement precision. There were differences among protocols for all attributes when states were analyzed separately and as a combined dataset. Measurement differences were influenced by choice of instruments, measurement method, measurement location, attribute definitions, and training approach. Comparison of data gathered by observers using different protocols will be difficult unless a core set of protocols for commonly measured stream attributes can be standardized among monitoring programs.  相似文献   

9.
Abstract: Over the past 10 years the Rosgen classification system and its associated methods of “natural channel design” have become synonymous to some with the term “stream restoration” and the science of fluvial geomorphology. Since the mid 1990s, this classification approach has become widely adopted by governmental agencies, particularly those funding restoration projects. The purposes of this article are to present a critical review, highlight inconsistencies and identify technical problems of Rosgen’s “natural channel design” approach to stream restoration. This paper’s primary thesis is that alluvial streams are open systems that adjust to altered inputs of energy and materials, and that a form‐based system largely ignores this critical component. Problems with the use of the classification are encountered with identifying bankfull dimensions, particularly in incising channels and with the mixing of bed and bank sediment into a single population. Its use for engineering design and restoration may be flawed by ignoring some processes governed by force and resistance, and the imbalance between sediment supply and transporting power in unstable systems. An example of how C5 channels composed of different bank sediments adjust differently and to different equilibrium morphologies in response to an identical disturbance is shown. This contradicts the fundamental underpinning of “natural channel design” and the “reference‐reach approach.” The Rosgen classification is probably best applied as a communication tool to describe channel form but, in combination with “natural channel design” techniques, are not diagnostic of how to mitigate channel instability or predict equilibrium morphologies. For this, physically based, mechanistic approaches that rely on quantifying the driving and resisting forces that control active processes and ultimate channel morphology are better suited as the physics of erosion, transport, and deposition are the same regardless of the hydro‐physiographic province or stream type because of the uniformity of physical laws.  相似文献   

10.
/ Little attention has been paid to wetland stream morphology in the geomorphological and environmental literature, and in the recently expanding wetland reconstruction field, stream design has been based primarily on stream morphologies typical of nonwetland alluvial environments. Field investigation of a wetland reach of Roaring Brook, Stafford, Connecticut, USA, revealed several significant differences between the morphology of this stream and the typical morphology of nonwetland alluvial streams. Six morphological features of the study reach were examined: bankfull flow, meanders, pools and riffles, thalweg location, straight reaches, and cross-sectional shape. It was found that bankfull flow definitions originating from streams in nonwetland environments did not apply. Unusual features observed in the wetland reach include tight bends and a large axial wavelength to width ratio. A lengthy straight reach exists that exceeds what is typically found in nonwetland alluvial streams. The lack of convex bank point bars in the bends, a greater channel width at riffle locations, an unusual thalweg location, and small form ratios (a deep and narrow channel) were also differences identified. Further study is needed on wetland streams of various regions to determine if differences in morphology between alluvial and wetland environments can be applied in order to improve future designs of wetland channels.KEY WORDS: Stream morphology; Wetland restoration; Wetland creation; Bankfull; Pools and riffles; Meanders; Thalweg  相似文献   

11.
ABSTRACT: Bankfull depth and discharge are basic input parameters to stream planform, stream restoration, and highway crossing designs, as well as to the development of hydraulic geometry relationships and the classification of streams. Unfortunately, there are a wide variety of definitions for bankfull that provide a range of values, and the actual selection of bankfull is subjective. In this paper, the relative uncertainty in determining the bankfull depth and discharge is quantified, first by examining the variability in the estimates of bankfull and second by using fuzzy numbers to describe bankfull depth. Fuzzy numbers are used to incorporate uncertainty due to vagueness in the definition of bankfull and subjectivity in the selection of bankfull. Examples are provided that demonstrate the use of a fuzzy bankfull depth in sediment trans. port and in stream classification. Using fuzzy numbers to describe bankfull depth rather than a deterministic value allows the engineer to base designs and decisions on a range of possible values and associated degrees of belief that the bankfull depths take on each value in that range.  相似文献   

12.
ABSTRACT: The last few decades have seen an increased reliance on the use of stream attributes to monitor stream conditions. The use of stream attributes has been criticized because of variation in how observers evaluate them, inconsistent protocol application, lack of consistent training, and the difficulty in using them to detect change caused by management activity. In this paper, we evaluate the effect of environmental heterogeneity and observer variation on the use of physical stream attributes as monitoring tools. For most stream habitat attributes evaluated, difference among streams accounted for greater than 80 percent of the total survey variation. To minimize the effect that variation among streams has on evaluating stream conditions, it may be necessary to design survey protocols and analysis that include stratification, permanent sites, and/or analysis of covariance. Although total variation was primarily due to differences among streams, observers also differed in their evaluation of stream attributes. This study suggests that if trained observers conducting a study that is designed to account for environmental heterogeneity can objectively evaluate defined stream attributes, results should prove valuable in monitoring differences in reach scale stream conditions. The failure to address any of these factors will likely lead to the failure of stream attributes as effective monitoring tools.  相似文献   

13.
Water quality and stream habitat in agricultural watersheds are under greater scrutiny as hydrologic pathways are altered to increase crop production. Agricultural drainage ditches function to remove water quickly from farmed landscapes. Conventional ditch designs lack the form and function of natural stream systems and tend to be unstable and provide inadequate habitat. In October of 2009, 1.89 km of a conventional drainage ditch in Mower County, Minnesota, was converted to an alternative system with a two‐stage channel to investigate the improvements in water quality, stability, and habitat. Longitudinal surveys show a 12‐fold increase in the pool‐riffle formation. Cross‐sectional surveys show an average increase in bankfull width of approximately 10% and may be associated to an increased frequency in large storm events. The average increase in bankfull depth was estimated as 18% but is largely influenced by pool formation. Rosgen Stability Analyses show the channel to be highly stable and the banks at a low risk of erosion. The average bankfull recurrence interval was estimated to be approximately 0.30 years. Overall, the two‐stage ditch design demonstrates an increase in fluvial stability, creating a more consistent sediment budget, and increasing the frequency of important instream habitat features, making this best management practice a viable option for addressing issues of erosion, sediment imbalance, and poor habitat in agricultural drainage systems.  相似文献   

14.
ABSTRACT: Data collected from 121 stream reaches during 1991 to 1993 were evaluated to determine the applicability of the Rosgen Stream Classification System (RSCS) to the low relief terrain within the Chequamegon‐Nicolet National Forest (CNNF) in Wisconsin, USA. All reaches were classified to RSCS Level I and II except that 10.7 percent had sinuosities below the continuum limits and one reach had a predominantly organic substrate. Five of eight possible RSCS Level I types were observed including B, C, D, A, E, and F; 86 percent were C and E types. Seventeen of 94 possible RSCS Level II types were observed. Most reaches were slightly entrenched, had low to moderate width/depth ratios, relatively low sinuosity, low slope, and sand or gravel as the dominant channel material. Discriminant analyses were used to verify the applicability of RSCS for streams within the CNNF; discriminant functions correctly classified 92.5 and 94.7 percent of the Level I and II RSCS types, respectively. When limits for E and F types were modified slightly at Level II by adding an additional category for slopes less than 0.1 percent (a modification we recommend for low relief terrain), discriminant functions correctly classified 99.1 percent of the types. Adding another slope break at 0.3 percent produced similar results. Based on our analyses, RSCS works well within the CNNF and is probably applicable to other areas with low‐relief terrain.  相似文献   

15.
ABSTRACT: Data were collected in 1992 from 17 mountain streams located within fine- to coarse-grained schist formations on the Idaho Panhandle National Forests. These were used to examine predictive relationships potentially useful in monitoring stream channel stability and fishery habitat. Channel morphology, sediment, and lithological data were obtained at 123 riffle sites. An analysis of materials deposited on gravel bars showed that at most sites, critical grain size, calculated using Duboy's tractive force equation, often does not provide accurate estimates of particle sizes moved at bankfull discharge. The tractive force equation gave reasonable estimates (± 10 mm) at 16 percent of the sites, but significantly over- or underestimated the sizes at the remaining sites. Regression and discriminant analysis showed that the relationship between critical grain size and the geometric mean diameter of material deposited on gravel bars was influenced most by the substrate size, slope, and width-to-depth ratio. Similarly, lithology was correlated with the size of particles moved. Particle sizes moved at bankfull discharge were not well correlated with residual pool depth or pool length.  相似文献   

16.
Rapid field-based protocols for classifying flow permanence of headwater streams are needed to inform timely regulatory decisions. Such an existing method was developed for and has been used in North Carolina since 1998. The method uses ordinal scoring of 26 geomorphology, hydrology, and biology attributes of streams. The attribute scores are summed and compared to threshold scores to assign a flow permanence class. Our study objective was to evaluate the method’s ability to classify the flow permanence of forested stream reaches from Piedmont and Southeastern Plains ecoregions in South Carolina. Ephemeral reaches scored significantly lower than intermittent and perennial reaches, but scores from intermittent and perennial reaches did not differ. Scores collected in the dry and wet seasons were strongly correlated, indicating that the method was seasonally stable. Scores had positive nonlinear relationships with the maximum recorded wet duration and the proportion of the record that reaches were wet, but were not related to drying frequency. Scores of the presence of baseflow in the dry season were more important in flow permanence classification than those from the wet season. Other important attributes and parameters in discriminating flow classes were macrobenthos, rooted upland plants, bankfull width, drainage area, and ecoregion. Although the North Carolina method did not consistently differentiate intermittent from perennial reaches, the indicator-based approach is a strong foundation from which to build a protocol for South Carolina. Adding measures like bankfull width and drainage area, weighting by ecoregion, or shifting thresholds may be warranted modifications for South Carolina.  相似文献   

17.
Abstract: Mapping stream channels and their geomorphic attributes is an important step in many watershed research and management projects. Often insufficient field data exist to map hydromorphologic attributes across entire drainage basins, necessitating the application of hydrologic modeling tools to digital elevation models (DEMs) via a geographic information system (GIS). In this article, we demonstrate methods for deriving synthetic stream networks via GIS across large and diverse basins using drainage‐enforced DEMs, along with techniques for estimating channel widths and gradient on the reach scale. The two‐step drainage enforcement method we used produced synthetic stream networks that displayed a high degree of positional accuracy relative to the input streams. The accuracies of our estimated channel parameters were assessed with field data, and predictions of bankfull width, wetted width and gradient were strongly correlated with measured values (r2 = 0.92, r2 = 0.95, r2 = 0.88, respectively). Classification accuracies of binned channel attributes were also high. Our methodology allows for the relatively rapid mapping of stream channels and associated morphological attributes across large geographic areas. Although initially developed to provide salmon recovery planners with important salmon habitat information, we suggest these methodologies are relevant to a variety of research and management questions.  相似文献   

18.
ABSTRACT: Detailed studies of long-term management impacts on rangeland streams are few because of the cost of obtaining detailed data replicated in time. This study uses government agency aquatic habitat, stream morphologic, and ocular stability data to assess land management impacts over four years on three stream reaches of an important rangeland watershed in northwestern Nevada. Aquatic habitat improved as riparian vegetation reestablished itself with decreased and better controlled livestock grazing. However, sediment from livestock disturbances and road crossings and very low stream flows limited the rate of change. Stream type limited the change of pool variables and width/depth ratio, which are linked to gradient and entrenchment. Coarse woody debris removal due to previous management limited pool recovery. Various critical-element ocular stability estimates represented changes with time and differences among reaches very well. Ocular stability variables tracked the quantitative habitat and morphologic variables well enough to recommend that ocular surveys be used to monitor changes with time between more intensive aquatic surveys.  相似文献   

19.
Many bank erosion models have limitations that restrict their use in wildland settings. Scientists and land managers at the Sequoia National Forest would like to understand the mechanisms and rates of streambank erosion to evaluate management issues and post‐wildfire effects. This study uses bank erosion hazard index (BEHI) and near‐bank stress (NBS) methods developed in Rosgen (2006 Watershed Assessment of River Stability and Sediment Supply [WARSSS]) for predicting streambank erosion in a geographic area that is dominated by colluvium and in which streambank erosion modeling has not been previously evaluated. BEHI evaluates bank susceptibility to erosion based on bank angle, bank and bankfull height, rooting depth and density, surface protection, and stratification of material within the banks. NBS assesses energy distribution against the bank measured as a ratio of bankfull near‐bank maximum depth to mean bankfull depth. We compared BEHI classes and NBS to actual bank erosion measured from 2008 to 2012. This index predicted streambank erosion with clear separation among BEHI ratings with R2 values of 0.76 for extreme, 0.37 for high/very high, 0.49 for moderate, and 0.70 for low BEHI. The relationships between measured erosion and BEHI extend the application of BEHI/NBS to a new region where they can inform management priorities, afforestation, stream/riparian restoration projects, and potentially burned area rehabilitation.  相似文献   

20.
Abstract: Managers, regulators, and researchers of aquatic ecosystems are increasingly pressed to consider large areas. However, accurate stream maps with geo‐referenced attributes are uncommon over relevant spatial extents. Field inventories provide high‐quality data, particularly for habitat characteristics at fine spatial resolutions (e.g., large wood), but are costly and so cover relatively small areas. Recent availability of regional digital data and Geographic Information Systems software has advanced capabilities to delineate stream networks and estimate coarse‐resolution hydrogeomorphic attributes (e.g., gradient). A spatially comprehensive coverage results, but types of modeled outputs may be limited and their accuracy is typically unknown. Capitalizing on strengths in both field and regional digital data, we modeled a synthetic stream network and a variety of hydrogeomorphic attributes for the Oregon Coastal Province. The synthetic network, encompassing 96,000 km of stream, was derived from digital elevation data. We used high‐resolution but spatially restricted data from field inventories and streamflow gauges to evaluate, calibrate, and interpret hydrogeomorphic attributes modeled from digital elevation and precipitation data. The attributes we chose to model (drainage area, mean annual precipitation, mean annual flow, probability of perennial flow, channel gradient, active‐channel width and depth, valley‐floor width, valley‐width index, and valley constraint) have demonstrated value for stream research and management. For most of these attributes, field‐measured, and modeled values were highly correlated, yielding confidence in the modeled outputs. The modeled stream network and attributes have been used for a variety of purposes, including mapping riparian areas, identifying headwater streams likely to transport debris flows, and characterizing the potential of streams to provide high‐quality habitat for salmonids. Our framework and models can be adapted and applied to areas where the necessary field and digital data exist or can be obtained.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号