Browsing by Subject "stream restoration"
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Item Open Access Comparison of streambed texture and hydraulic conductivity between degraded, natural reference, enhanced, and restored streams in the New Hope Creek watershed in Durham, North Carolina(2017-04-28) Crowell, Breanna; Fowler, Jerrett; Lenart, Jennifer; Smith, AustonCritical links exist between stream channel attributes and water quality function within stream restorations. During the process of stream restoration, much attention goes into recreating the profile of natural reference stream channels, but far less attention is given to factors that affect characteristics of the hyporheic zone in restored streambeds. The Priority 1 restoration process typically requires filling in the existing unstable stream channel and creating a new channel in the adjacent floodplain. The restoration of urban streams is often confined spatially and economically, so one alternative method includes stream enhancements that occur entirely with the stream channel. For this analysis, six streams – two natural, one degraded, one enhanced, and two restored -- near Durham, North Carolina were selected for textural and hydraulic conductivity analysis to identify the potential for hyporheic functions within these different systems. While direct measurement of hyporheic exchange is a complex process that is often not feasible stream restoration evaluation, there are several relatively simple indicators of potential hyporheic exchange including soil texture and field permeameter measurements. The study seeks to answer two questions: (1) Is there a difference in streambed sediment texture between degraded, natural reference, enhanced, and Priority 1 restored streams and within the vertical profile of a streambed? (2) How does streambed hydraulic conductivity relate to sediment texture in a stream system? This analysis relates three main findings in relation to streambed sediment texture and permeability. First, twenty-five percent of the measured variation in hydraulic conductivity of a streambed is explained by clay. Second, Priority 1 restorations do initially lose permeability and potentially hyporheic functionality, and this may take around ten years to be recovered in a new channel. Third, despite a higher cost per linear foot in Priority 1 restorations, the additional benefits provided by this method could outweigh this initial expense. Streambed sediment texture is not the only factor in explaining hyporheic functionality, but is a key component to whether the hyporheic zone can exist. Managers should consider the texture of a new channel when restorations are completed as it may relate to how functionality will be regained in the system.Item Open Access Evaluation of Pool Habitat Suitability of In-Stream Structures in Restored Streams of Western North Carolina(2007-08-31T19:47:10Z) Hammontree, AmyAbstract Evaluation of Pool Habitat Suitability of In-Stream Structures in Restored Streams of Western North Carolina by Amy Hammontree August 2007 One of the most critical aspects of stream restoration is the creation of suitable aquatic habitat. Much of this work is accomplished through the installation of both hard and soft in-stream structures. The structural stability of these practices has been well studied and monitored for decades. However, the evaluation of habitat potential of these structures has remained almost entirely qualitative and categorical. The objective of this study aimed to fill this void by quantitatively evaluating the habitat potential of a variety of common in-stream restoration structures and bend treatments in Western North Carolina through the measurement of common habitat features such as pool depth and length, distance to cover, and depth of cover (or undercut), with the ultimate goal of providing design recommendations for stream restoration projects listing habitat enhancement as a top priority. In analyzing the results of the study, high habitat quality was defined by large pool depths (for increased niche space and low flow velocities), small distances to cover, (for faster escape from predation), and large cover depth or undercut values, (for shelter, predation, and rearing). Collectively, soft structures provided the deepest pool depths, with shorter distances to cover and larger cover depth values than corresponding hard in-stream structures. Likewise, bend treatment groups containing soft in-stream structures also excelled in these areas. Bends containing hard structures produced much higher pool lengths, in many cases longer than the curvature of the bend itself. Design goals based on habitat enhancement of small streams should focus heavily on the installation of rootwad revetments and cover logs for creation of deeper pools with increased flow variation and increased cover depth. In addition, both these structures will also serve to promote the acquirement and continued recruitment of large and small woody debris into the streams. Where hardened structures are deemed necessary for structural or hydrologic purposes, they should be accompanied by soft in-stream structures to create combination bends to supplement habitat within these areas.Item Open Access The Effect of Stream Restoration on Turtle Species Assemblages in the Piedmont Region of North Carolina, USA(2010-04-30T18:48:42Z) Nowalk, MauraIn response to the negative impact of urban and agricultural development on freshwater systems, stream restoration efforts often attempt to return degraded streams to a natural ecosystem structure and function. However, few attempts have been made to monitor the effectiveness of restored streams in supporting certain important groups of organisms found in native aquatic ecosystems, such as freshwater turtles. The purpose of this study was to compare six natural and six restored streams in the North Carolina Piedmont by quantifying habitat characteristics that might drive differences in turtle assemblages and by directly capturing turtles at each site. Stream habitat was characterized by water quality analyses, structural measurements of each stream, and floodplain vegetation surveys. Three baited hoop nets were set at each location for a total of 36 trap-nights at each stream, which were used to collect turtle population data from mid-May to late July 2009. In total 77 turtles were captured comprising eight species. At the natural sites, 24 turtles were captured representing five species (C. picta, C. serpentina, P. floridana, S. odoratus, and T. scripta scripta); 53 turtles were captured at the restored sites representing seven species (C. guttata, C. picta, C. serpentina, K. subrubrum, S. odoratus, T. scripta elegans and T. scripta scripta). Modified t-tests, based on randomized permutation tests, suggest that natural and restored sites differ in turtle abundance (p=0.13), but are not different in species richness (p>0.99) or gender ratios (p=0.80). A species community index suggests that natural and restored turtle assemblages overlap by 50%. Non-metric multidimensional scaling analyses of habitat characteristics indicate that natural and restored streams differ in channel structure, vegetation, and some water quality variables. Using Mantel’s test to compare turtle species composition with the most important variables separating natural and restored streams, canopy, slope, total phosphorus, chlorophyll A, and Juncus effuses abundance were found to be most strongly correlated with patterns in turtle assemblage composition. This is one of the first studies to address the possible impact of stream restoration on turtle assemblages, and the findings suggest that restored streams may be better habitat for turtles in the North Carolina Piedmont.Item Open Access The Effects of Vegetative Disturbance on Winter Riparian Bird Populations: A Multinomial Analysis(2009-04-24T17:35:03Z) Vaughan, KristinTwo rural stream sites intended for enhancement were evaluated pre-construction to collect baseline data on riparian bird populations and vegetative characteristics. The fixed-radius point count method was used to survey the winter avian community, and vegetative attributes (DBH, percent tree canopy cover, volume of downed woody debris) were collected within each of the radius plots. Using a multinomial regression, the probability of detecting each bird species was calculated for each survey plot and subsequently related to the characteristics of the vegetation to create a model that describes the winter bird-habitat relationship. The model predicted that major vegetative disturbances would be highly detrimental to the diversity of the winter bird community, and demonstrated that mature bottomland hardwood forests are ideal for the numerous habitat preferences of different wintering birds. These data provide the basis for multiple suggestions for stream restoration practices on sites where the riparian buffer is already composed of mature bottomland hardwood forests, the most important of which is conserving and improving the established vegetation by considering stream mitigation practices that are less disruptive than restoration.