Bankfull Width Research Articles

Mechanisms and source distances for the input of large woody debris to forested streams in British Columbia, Canada

The geomorphic process domain concept predicts consistent associations between stream channel geomorphology and large woody debris (LWD) input mechanisms. We used synoptic surveys at 51 stream reaches adjacent to undisturbed mature or old-growth forests in central and southern British Columbia to test associations between stream geomorphology and the input processes, source distances, physical characteristics, and geomorphic functions of LWD within the bankfull channel. Standing dead tree fall was the dominant input mechanism, but bank erosion was important in low- and medium-gradient channels >3 m bankfull width. Wind-induced inputs (stem breakage and windthrow) were relatively more important in small or steep channels. LWD piece size and source distance varied among delivery processes. LWD originated at ground distances up to 65 m from the streams, but 90% of the LWD at a site originated within 18 m of the channel at 90% of the sites. Statistical models incorporating tree size and stream characteristics (bankfull width, channel type) explained 40%–64% of the variation among sites in the distances from which LWD entered streams. In general, LWD source distances increased with increasing tree height and decreased with increasing stream width; however, the strengths of these relationships were modified by channel type.

Bankfull Hydraulic Geometry Relationships for the Inner and Outer Bluegrass Regions of Kentucky

Bankfull hydraulic geometry relationships relate bankfull stream dimensions, such as cross-sectional area, width, mean depth, mean velocity, width to depth ratio, and slope to bankfull discharge. These relationships can assist in determining a design discharge for stream restoration and management projects. This study assessed 27 stable streams located in the Inner Bluegrass and Outer Bluegrass regions of Kentucky. Reaches were selected based on the presence of a U.S. Geological Survey gage, as well as other conditions such as presence of readily identifiable bankfull indicators, stability indices, and site accessibility. Bankfull channel dimensions and discharges were determined, and hydraulic geometry relationships were developed for both the Inner Bluegrass and Outer Bluegrass regions. These scaling relationships for karst-influenced streams were similar to others reported in the literature for non-karst areas. Significant differences between the regions were found only for bankfull width and width-to-depth ratio. Streams in the Inner Bluegrass tended to be more narrow and deep at bankfull discharges less than 10 m3s−1 and wider and shallower at bankfull discharges greater than 20 m3s−1 as compared to stream in the Outer Bluegrass. It is suspected that physiographic conditions related to local geology and/or riparian vegetation at three sites in the Outer Bluegrass accounted for these differences. Results of this study indicate that in instances of geologic variation within a physiographic region, hydraulic geometry relationships may require evaluation at the watershed scale.

Identifying the spatial pattern of wood distribution in northeastern North American streams

The spatial distribution of instream wood influences important ecological processes but has proven challenging to describe quantitatively. We present a modified version of a previously described metric used to quantify the spatial extent and pattern of instream wood distribution, then apply this approach in evaluating the distribution of wood habitat in forested northeastern North American streams. This revised metric, a ‘binned neighbor-K analysis’, provides greater resolution in evaluating the presence of aggregated, periodic, or segregated wood distributions in stream ecosystems. We employed this metric in evaluating the distribution of wood within 17 streams in two regions of northeastern North America. Our results indicate that the binned neighbor-K approach more accurately represents the spatial extent at which wood accumulates in streams by identifying recurring intervals in streams within which instream wood is not present and by more accurately quantifying the spatial extent of wood aggregations and periodically repeating occurrences of accumulated wood. We also used this metric to quantify the overall extent of wood ‘organization’ in streams, which revealed similarities and differences in instream wood distribution patterns in the two regions evaluated. Wood distribution patterns in both study regions were generally consistent with our expectations of increased organization at an intermediate stream size (up to 10 m bankfull width), then in larger streams (> 10 m) wood was less organized. These observed patterns result from landscape and ecosystem influences upon wood accumulation and movement in streams.

Meander dynamics in a changing river corridor

In the first decades of the twentieth century, the Ebro River was the Iberian channel with the most active fluvial dynamics and the most remarkable spatial–temporal evolution. Its meandering typology, the dimensions of its floodplain (with an average width >3.0km), and the singularities of its flow regime produced a especially interesting set of river functions from the perspective of the fluvial geomorphology of the largest Mediterranean channels.The largest dynamics of the Ebro River are concentrated along the meandering profile of the central sector. During the twentieth century, this sector experienced a large alteration of its geomorphological structure. We present here an analysis of this evolution through the cartographic study of a long segment of the river (~250km) in 1927, 1956, and 2003. The study is focused on a wide set of geomorphic parameters and indicators that represent the forms of the meander belt, its lateral dynamics, and the overall mobility of the river corridor. The results of the analysis show a large transformation of the meander dynamics, as well as a massive loss of the river lateral activity, most of which occurred in the second half of the twentieth century.This intense geomorphological transformation becomes visible in (i) the large reduction of the bankfull width and the active channel area; (ii) the decrease in the rate of lateral channel migration; (iii) the loss of channel activity; and (iv) the large reduction of coincidence of the active channel areas. However, the most traditional form parameters (i.e., wavelength, amplitude, radius of curvature, and meander length) do not show significant differences throughout the time interval analysed. The study reinforces the necessity of integrating a wide range of dynamic indicators, which may complement the classical form parameters and represent the real functioning of the river corridor, in the geomorphological analyses of meander dynamics.This work also shows the most important procedures for the recuperation of the ecomorphological processes of the meander belt. It highlights the most urgent measurement for ecological recovery and illustrates the management scenarios that have led to the present-day situation of the river system. This work further highlights the management scenarios that could be most important for the continued good status of the meander dynamics in this changing river corridor.

Developing channel and floodplain dimensions with limited data: a case study in the Amazon Basin

ABSTRACTThis research builds on the concept of hydraulic geometry and presents a methodology for estimating bankfull discharge and the hydraulic geometry coefficients and exponents for a station using limited data; only stage‐discharge and Landsat imagery. The approach is implemented using 82 streamflow gauging locations in the Amazon Basin. Using the estimated values for the hydraulic geometry relations, bankfull discharge, discharge data above bankfull and upstream drainage area at each site, relationships for estimating channel and floodplain characteristics as a function of drainage area are developed. Specifically, this research provides relationships for estimating bankfull discharge, bankfull depth, bankfull width, and floodplain width as a function of upstream drainage area in the Amazon Basin intended for providing reasonable cross‐section estimates for large scale hydraulic routing models. The derived relationships are also combined with a high resolution drainage network to develop relationships for estimating cumulative upstream channel lengths and surface areas as a function of the specified minimum channel width ranging from 2 m to 1 km (i.e. threshold drainage areas ranging from 1 to 431,000 km2). At the finest resolution (i.e. all channels greater than 2 m or a threshold area of 1 km2), the Amazon Basin contains approximately 4.4 million kilometers of channels with a combined surface area of 59,700 km2. The intended use of these relationships is for partitioning total floodable area (channels versus lakes and floodplain lakes) obtained from remote sensing for biogeochemical applications (e.g. quantifying CO2 evasion in the Amazon Basin). Copyright © 2011 John Wiley & Sons, Ltd.

Are Ozark Streams Underfit? Using Gis to Re-Examine Dury's Theory of Underfit Streams

The theory of underfit streams as described by George H. Dury has often been used to explain the distinct compound valleys found throughout the Ozark Plateaus physiographic province. Dury developed mathematical relationships between the valley meander wavelength and the stream meander wavelength to define the underfit condition. He found that Osage underfit streams fail to meander within the stream valley and have wavelength ratios of approximately 3.5, and that the valley meander wavelengths are 30 times the bankfull width of the stream. This study uses modern analytical techniques and data sets to test these mathematical relationships both for watersheds used in Dury's original study and for other watersheds in the region. Using GIS-based analysis of digital raster graphics, digital elevation models, and U.S. Geological Survey hydrology data, we could not replicate Dury's results. Most wavelength ratios measured for all streams were less than 3.0, and valley wavelengths ranged from 0.08 to 141 times the bankfull bed width of the river. The theory of underfit streams fails to explain the great variability of data derived in this analysis. In fact, this study suggests that structural controls have a greater influence on modern valley architecture than hydrologic controls.

Regime Equations for Natural Meandering Cobble- and Gravel-Bed Rivers

Data obtained from 48 stable reaches of upland rivers in the UK were stratified by stream type to develop regime equations specifically for natural meandering cobble- and gravel-bed rivers: C3 and C4 stream types, according to the Rosgen classification. Multiple regression models were applied to derive equations for reach-averaged values of bankfull width, mean depth, slope, meander arc length and sinuosity in bankfull discharge and associated bed-material load, the caliber of the bed material, bank vegetation density, and valley slope. The equations show that their cross-sectional dimensions are primarily determined by the bankfull discharge, bank vegetation, and bed-material size, whereas their profile and plan form are very strongly influenced by the valley gradient. Although bankfull bed-material load only appears to have a minor influence on channel morphology, its effect is implicit in the value of bankfull discharge because this corresponds to the flow that transports most of the bed-material load....

Does Channel Incision Affect In-stream Habitat? Examining the Effects of Multiple Geomorphic Variables on Fish Habitat

Incised river channels are dynamic components of fluvial systems, represent geomorphic degradation, and are encountered worldwide. Ecological effects of incision can be far-reaching, affecting habitat availability and channel processes. Although incision can reflect habitat degradation, some studies suggest that important in-stream habitats do not differ with the degree of incision. Therefore, we tested whether in-stream habitat variables that are important to imperiled fishes differ in river reaches with varying degrees of incision. Because incision (measured using entrenchment ratio) had no discernable effect on in-stream habitat characteristics (i.e., proportion fines, gravel, cobble, and macrophyte occurrence and length), we expanded our analysis to assess the effects of 29 additional geomorphic variables on in-stream habitat. These analyses indicated that bank height, bed mobility, D84, cross-sectional area, bankfull width, and wetted perimeter accounted for 42% of macrophyte occurrence and 64% of macrophyte length variance. Postflood surveys indicated that macrophyte occurrence on cobble declined as bank height and bed mobility increased, and sediment size decreased, suggesting that sediment size and bed mobility have a stronger influence on in-stream habitat than incision. Although channel incision often indicates environmental degradation, important aspects of habitat are not described by this measurement. Strategies that depend on incision to identify restoration sites may have limited habitat benefits in Southeastern Piedmont streams and rivers. Instead, landscape or shoal-scale restoration approaches that increase coarse sediment proportions may increase macrophyte occurrence, length, and persistence. Sediment budgets that identify coarse and fine sediment sources and transport may be useful to prioritize restoration approaches.

A new framework for modeling the migration of meandering rivers

AbstractMany models of river meander migration rely upon a simple formalism, whereby the eroding bank is cut back at a rate that is dictated by the flow, and the depositing bank then migrates passively in response, so as to maintain a constant bankfull channel width. Here a new model is presented, in which separate relations are developed for the migration of the eroding bank and the depositing bank. It is assumed that the eroding bank consists of a layer of fine‐grained sediment that is cohesive and/or densely riddled with roots, underlain by a purely noncohesive layer of sand and/or gravel. Following erosion of the noncohesive layer, the cohesive layer fails in the form of slump blocks, which armor the noncohesive layer and thereby moderate the erosion rate. If the slump block material breaks down or is fluvially entrained, the protection it provides for the noncohesive layer diminishes and bank erosion is renewed. Renewed bank erosion, however, rejuvenates slump block armoring. At the depositing bank, it is assumed that all the sediment delivered to the edge of vegetation due to the transverse component of sediment transport is captured by encroaching vegetation, which is not removed by successive floods. Separate equations describing the migration of the eroding and depositing banks are tied to a standard morphodynamic formulation for the evolution of the flow and bed in the central region of the channel. In this model, the river evolves toward maintenance of roughly constant bankfull width as it migrates only to the extent that the eroding bank and depositing bank ‘talk’ to each other via the medium of the morphodynamics of the channel center region. The model allows for both (a) migration for which erosion widens the channel, forcing deposition at the opposite bank, and (b) migration for which deposition narrows the channel forcing erosion at the opposite bank. Copyright © 2010 John Wiley & Sons, Ltd.

Physical Basis for Quasi-Universal Relationships Describing Bankfull Hydraulic Geometry of Sand-Bed Rivers

Empirical data indicate that hydraulic geometry relationships for single-thread sand-bed rivers (i.e., rivers with median bed-material size between 0.062 and 0.50 mm) can be delineated such that bankfull width, bankfull depth, and channel slope are related in consistent ways to bankfull discharge. Such relationships ought to be the external expression of physical relationships intrinsic to sand-bed river dynamics. In this study, a back-calculation is performed to identify parameters (exponents and coefficients) for three relationships taken to be intrinsic to sand-bed rivers: (1) a generalized Manning-Strickler resistance relationship; (2) a relationship for channel-forming Shields number; and (3) a relationship for sand yield at bankfull flow. To back-calculate parameters for the physical relationships, first the hydraulic geometry relationships are expressed in suitable dimensionless form. Second, the physical relationships are expressed with coefficients and exponents that are analytically related to p...

Quasi‐equilibrium conditions of urban gravel‐bed stream channels in southern Ontario, Canada

ABSTRACTUrban gravel‐bed stream channels in southern Ontario, Canada identified to be in a state of quasi‐equilibrium have been studied over the past 15 years and compared against rural gravel bed stream channels of the same hydrophysiographic region. Bankfull width and depth versus bankfull discharge were not found to increase as a function of increasing urbanization as has been found in many other studies. The observed annual frequency of bankfull discharge was typically less than a 1‐year return period with many sites ranging between 2 and 18 bankfull events per year with higher intensity and shorter duration urban flood responses, which further identified significant limitations in using annual peak discharge methods for predicting morphological forming flows in urban watersheds.The cumulative volume of bankfull and larger flood events from the urban stream channels were very similar to the same annual event volumes in the rural comparison study reaches. Bed material supply was found to decrease with increasing urbanization and the reduction in bed material supply appears to be off‐set by the smaller bankfull channel width, depth and access to floodplains during large flood events. Field evidence may also suggest a even greater reduction in channel width trajectory, relative to the rural setting, with expansive floodplains to maintain quasi‐equilibrium conditions as bed material supply continues to decrease with increased anthropogenic activity. Copyright © 2010 John Wiley & Sons, Ltd.

Channel changes in burned streams of northern Nevada

In the Great Basin, frequency of large-fire is increasing. To better understand fire and riparian system interactions, we studied pre- to post-fire changes in ten riparian attributes of a randomly sampled reach of forty three streams burned within a three-year period. Post-fire data were collected four to six relatively dry years after late-summer wildfires in sagebrush dominated watersheds of the North Central Great Basin. All streams had been surveyed in the one to fifteen years prior to the fire. Five channel attributes improved; bankfull width decreased 21%, riparian width increased 79%, median dominant riparian vegetation increased by two categories (grass/sod to high brush), bank stability increased by one category, and median bank angle decreased. Four attributes did not change; bank cover, organic debris, bank undercuts, and embeddedness. An increase of sand by 19% in the dominant bottom material was considered unfavorable. Riparian vegetation and systems seem to be resilient and whether improvement was due to fire or changed management and time for recovery was not ascertained. Overall, degradation to stream channel attributes was minimal to non-existent suggesting riparian stability and/or resiliency.

Ecoregions and stream morphology in eastern Oklahoma

Broad-scale variables (i.e., geology, topography, climate, land use, vegetation, and soils) influence channel morphology. How and to what extent the longitudinal pattern of channel morphology is influenced by broad-scale variables is important to fluvial geomorphologists and stream ecologists. In the last couple of decades, there has been an increase in the amount of interdisciplinary research between fluvial geomorphologists and stream ecologists. In a historical context, fluvial geomorphologists are more apt to use physiographic regions to distinguish broad-scale variables, while stream ecologists are more apt to use the concept of an ecosystem to address the broad-scale variables that influence stream habitat. For this reason, we designed a study using ecoregions, which uses physical and biological variables to understand how landscapes influence channel processes. Ecoregions are delineated by similarities in geology, climate, soils, land use, and potential natural vegetation. In the fluvial system, stream form and function are dictated by processes observed throughout the fluvial hierarchy. Recognizing that stream form and function should differ by ecoregion, a study was designed to evaluate how the characteristics of stream channels differed longitudinally among three ecoregions in eastern Oklahoma, USA: Boston Mountains, Ozark Highlands, and Ouachita Mountains. Channel morphology of 149 stream reaches was surveyed in 1st- through 4th-order streams, and effects of drainage area and ecoregion on channel morphology was evaluated using multiple regressions. Differences existed (α ≤ 0.05) among ecoregions for particle size, bankfull width, and width/depth ratio. No differences existed among ecoregions for gradient or sinuosity. Particle size was smallest in the Ozark Highlands and largest in the Ouachita Mountains. Bankfull width was larger in the Ozark Highlands than in the Boston Mountains and Ouachita Mountains in larger streams. Width/depth ratios of the Boston Mountains and Ozark Highlands were not statistically different. Significant differences existed, however, between the Boston Mountains and Ozark Highlands when compared individually to the Ouachita Mountains. We found that ecoregions afforded a good spatial structure that can help in understanding longitudinal trends in stream reach morphology surveyed at the reach scale. The hierarchy of the fluvial system begins within a broad, relatively homogenous setting that imparts control on processes that affect stream function. Ecoregions provide an adequate regional division to begin a large-scale geomorphic study of processes in stream channels.

Large wood abundance, distribution and mobilization in a third order Coastal mountain range river system, southern Chile

Large wood (LW) abundance, longitudinal distribution and mobilization were studied in the Vuelta de la Zorra channel draining a third order catchment located in the Coastal mountain range of southern Chile. Seventy-five percent of the 586.8 ha study catchment area is covered by evergreen native rainforests, 24% by Eucalyptus nitens plantations and the remaining 1% are different sites were native tree and shrub species are regenerating in areas that were prepared for forest replacement in the late 1980s but finally left unplanted. In a segment, 1557 m in length, surveyed between November 2008 and February 2009, a total of 484 pieces representing 181 m 3 of LW were measured. Using bankfull width and length this volume corresponds to 109 m 3 ha −1 or 11.6 m 3 100 m −1. LW was distributed along the channel in correlation with bankfull width. The channel segment was re-surveyed in December 2009 and we found that after one winter season 12% of the LW were transported downstream the river channel and 9 new wood elements were recruited. The LW traveled distance and traveled distance/piece diameter ratio decreased with increasing piece length/mean bankfull ratio. These results contribute to understand the complexity of LW abundance, mobilization and recruitment processes, and their effects on channel morphology, sediment routing and ecology in Chilean catchments.

Hydrologic and Morphologic Variability of Streams With Different Cranberry Agriculture Histories, Southern New Jersey, United States1

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.xAbstract: 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.

Photogrammetric monitoring of small streams under a riparian forest canopy

AbstractThe recent advent of digital photogrammetry has enabled the modeling and monitoring of river beds at relatively high spatial resolution (0·01 to 1 m) through the extraction of digital elevation models (DEMs). The traditional approach to image capture has been to mount a metric camera to an aircraft, although non‐metric cameras have been mounted to a variety of novel aerial platforms to acquire river‐based imagery (e.g. helicopters, radio‐controlled motorized vehicles, tethered blimps and balloons). However, most of these techniques are designed to acquire imagery at flying heights above the riparian tree canopy. In relatively narrow channels (e.g. <20 m bankfull width), streamside trees can obscure the channel and limit continuous photogrammetric data acquisition of both the channel bed and banks, while still providing useful information regarding the riparian canopy and even spot elevations of the channel. This paper presents a technique for the capture and analysis of close‐range photogrammetric data acquired from a vertically mounted non‐metric camera suspended 10 m above the channel bed by a unipod. The camera is positioned under the riparian forest canopy so that the channel bed can be imaged without obstruction. The system is portable and permits relatively rapid image acquisition over rough terrain and in dense forest. The platform was used to generate DEMs with a nominal ground resolution of 0·03 m. DEMs generated from this platform required post‐possessing to either adjust or eliminate erroneous cells introduced by the extraction process, overhanging branches, and by the effects of refraction at the air–water interface for submerged portions of the channel bed. The vertical precision in the post‐processed surface generally ranged from ± 0·01 to 0·1 m depending on the quality of triangulation and the characteristics of the surface being imaged. Copyright © 2010 John Wiley & Sons, Ltd.

Red alder leaf decomposition and nutrient release in alder and conifer riparian patches in western Washington, USA

Current management practices encourage conversion of red alder ( Alnus rubra) riparian forests to conifers in the Pacific Northwest U.S. Patches of young naturally regenerated conifers are commonly present in alder dominated riparian areas and an understanding of the soil processes in these patches will be helpful in guiding future riparian management. Study objectives were to: (1) determine decomposition rates of red alder leaves in riparian alder and conifer patches, (2) relate decomposition rates to environmental factors and litter chemistry, and (3) determine nutrient release from decomposing alder leaves in these patches. Study sites were riparian areas adjacent to Brown and Le Bar creeks in the Skokomish River basin, Olympic National Forest, Washington. Red alder leaves were placed in litterbags in red alder and conifer riparian patches along each stream in November 2000 and collected after 1 and 3 years. There was rapid mass loss of alder leaves in the first year in both patch types, but decomposition was significantly faster ( p < 0.05) in alder patches (43.2% mass remaining, k = 0.855 year −1) than in conifer patches (48.4% mass remaining, k = 0.734 year −1). There was little mass loss after the first year and no significant difference in decomposition rates. After 3 years mass remaining was 44.2% ( k = 0.283 year −1) and 47.8% ( k = 0.48 year −1) in alder and conifer patches, respectively. Decomposition rate differences were attributed more to the effects of the different litters in each patch and the influence on soil microbial and faunal communities than differences in soil temperature and moisture. The forest floor was deeper in conifer patches (3.7 cm) than alder (1.8 cm) patches. This was ascribed to slower decomposition rates in conifer patches, greater litterfall in conifer patches, and/or removal of alder surface litter by flooding. Alder patches were lower in elevation (0.8 m above bankfull width) than conifer patches (2.2 m). Forest floor and soil C and N concentrations and pHs were not significantly different in alder and conifer patches. Nutrient release from decomposing alder leaves was not significantly different in conifer and alder patches, although there was a trend for C, N, P, K, and Ca to be lost faster from leaves in alder patches than conifer patches in the first year. Red alder litter input to riparian conifer patches will initially decompose rapidly and provide nutrients, particularly N and P to conifers, as well as enhancing soil C since long-term decomposition rates are slow.

Characteristics of the Lower Yellow River channel shrinkage and its discriminant parameters

This paper analyzes the changing trends of the Lower Yellow River (LYR) transverse profile parameters and their aberrance points by the time series analysis method. Research results show that there has been a trend of changes in the LYR channel transverse profile parameters since the 1950s. The main river channel has a tendency of shrinkage year by year and the trend will be continued in the future. The main features of the LYR channel shrinkage are remarkable reductions of bankfull discharges and bankfull areas, corresponding decreases of bankfull widths, average bankfull water depths and maximal bankfull water depths, as well as increases of bankfull water levels and width-depth ratios accompanied. The discriminant parameters for threshold of the LYR main channel shrinkage were put forward. It indicates that the LYR main channel began to shrink in the 1970s and has entered into a serious phase of channel shrinkage since the 1990s. The incompatible index of discharged water-sediment processes of the Sanmenxia Reservoir was introduced, which revealed that there was a trend of increasing in the incompatibility between water flow and sediment load. Response relations between the LYR main channel shrinkage parameters and discharged water-sediment processes of the Sanmenxia Reservoir were founded, which indicate that the LYR main channel shrinkage can be mitigated and improved through the regulation of discharged water-sediment processes of the reservoir, especially through the regulation of water-sediment incompatible index. The LYR channel for water and sediment transportation can be restored and maintained.

Regression estimates of design flows for ungaged sites using bankfull geometry and flashiness

Bankfull geometry data at 22 United States Geological Survey stream flow gaging sites in the Red River Basin of Minnesota and North Dakota were used for developing regression estimates of flows of different return periods. Regression equations were developed first by using only basin characteristics and then by using only bankfull geometry data as independent variables. Flashiness was included later as an independent variable in both cases. In all, 101 regressions were evaluated. Storage, channel slope, and bankfull width did not appear in the selected regressions. Stream flashiness was found to be an important explanatory variable in both bankfull geometry and basin characteristics regressions. The bankfull geometry data produced slightly better regression equations than the basin characteristics data. The bankfull geometry regressions will be useful to predict design flows and to compare with flow estimates developed by traditional methods for ungaged sites in the Red River Basin.

The Effects of Road Crossings on Prairie Stream Habitat and Function

ABSTRACT Improperly designed stream crossing structures may alter the form and function of stream ecosystems and habitat and prohibit the movement of aquatic organisms. Stream sections adjoining five concrete box culverts, five low-water crossings (concrete slabs vented by one or multiple culverts), and two large, single corrugated culvert vehicle crossings in eastern Kansas streams were compared to reference reaches using a geomorphologic survey and stream classification. Stream reaches were also compared upstream and downstream of crossings, and crossing measurements were used to determine which crossing design best mimicked the natural dimensions of the adjoining stream. Four of five low-water crossings, three of five box culverts, and one of two large, single corrugated pipe culverts changed classification from upstream to downstream of the crossings. Mean riffle spacing upstream at low-water crossings (8.6 bankfull widths) was double that of downstream reaches (mean 4.4 bankfull widths) but was similar upstream and downstream of box and corrugated pipe culverts. There also appeared to be greater deposition of fine sediments directly upstream of these designs. Box and corrugated culverts were more similar to natural streams than low-water crossings at transporting water, sediments, and debris during bankfull flows.