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1
Bahuguna, Devesh. "Postharvest windthrow and recruitment of large woody debris in riparian buffers." Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/3326.
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Large woody debris (LWD) is an important component of forest ecosystems and provides structural complexity to small streams. Riparian buffers are intended to provide long term supplies of LWD, but post harvest windthrow often occurs. To document the impacts of windthrow in riparian buffers and identify the components needed for small stream LWD recruitment modeling, I sampled 39 small streams at the Malcolm Knapp Research Forest (MKRF) and on Vancouver Island. I took two basic approaches. In the small stream experiment at MKRF a series of small clearcuts were harvested in 1998 in a 70 year old second growth stand. I measured LWD in 10m and 30m buffer treatments, and in the unharvested control. I added samples in mature and old-growth stands for comparison. In the second approach, I retrospectively sampled buffers that were exposed by harvesting from 0-20yrs ago on southwestern and northeastern Vancouver Island. In both studies, all logs greater than 7.5 cm diameter at mid-creek, in decay class 1 to 4 that spanned at least part of stream channel width were measured. There was no significant difference in the number of spanning and in-creek logs in 10m and 30m buffer given the short term monitoring of woody debris in the buffers. The majority of windthrown trees were still suspended above the stream channel years after a windthrow event. The height above stream was negatively correlated with log decay class and the buffer age class. The number of logs was higher in immature stands than mature stands. As the stems per hectare in riparian stands increases, so does the frequency of spanning LWD. The frequency of logs in decay classes 3 and 4 was higher in older buffers, and deciduous LWD decayed more quickly than conifers. Interestingly, the log length was found to be shorter in advance stage of decay. Key elements in a conceptual model of LWD recruitment via windthrow are the geometry of initial log position, log size, species and decay rate.
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Wilson, Jessica. "The Efficacy and Design of Coastal Protection Using Large Woody Debris." Thesis, Université d'Ottawa / University of Ottawa, 2020. http://hdl.handle.net/10393/41573.
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Those who frequent the coastline may be accustomed to seeing driftwood washed onshore, some of it having seemingly found a home there for many years, others having been freshly deposited during the last set of storms; However, if a passerby were to take a closer look at the driftwood on the coastline, they may notice that some of these logs – also known as Large Woody Debris (LWD) – are anchored in place, a practice which is generally used for the purpose of stabilizing the shoreline or reducing wave-induced flooding. Records of existing anchored LWD project sites date back to 1997 and anecdotal evidence suggests that the technique has been used since the mid-1900’s in coastal British Columbia (BC), Canada, and Washington State, USA. Now, with an increased demand for natural and nature-based solutions, the technique is again gaining popularity. Despite this, the design of anchored LWD has largely been based on anecdotal observations and experience, as well as a continuity of design practices from the river engineering field. To date, there is no known peer-reviewed literature on the design or efficacy of LWD protection systems in a coastal environment.
In 2019, the “Efficacy and Design of Coastal Protection using Large Woody Debris” research project was initiated to determine if LWD are effective at stabilizing the shoreline under wave action, if they are effective at reducing wave run-up, and if they are durable enough to meet engineering requirements for shore protection. In addition, the project aimed to determine the optimum configuration of LWD for design purposes. To meet these objectives, this study included the following work: (1) field studies of existing LWD installations, (2) experimental modeling of beach morphology with and without LWD structures, (3) experimental modeling of wave run-up with and without LWD structures, and (4) development of preliminary design guidance.
The first phase of the project included field investigations at 15 existing anchored LWD sites in coastal BC and Washington State. Site characteristics, design techniques, and durability indicators were examined and correlated to a new design life parameter: ‘Effective Life’. Six primary installation techniques were observed: Single, Multiple, Benched, Stacked, Matrix, and Groyne. Observed durability and/or performance issues included: missing LWD, erosion, arson, wood decay, and anchor corrosion/damage. The Effective Life of anchored LWD was found to be strongly correlated to the tidal range and the upper beach slope for all installation types, and the LWD placement elevation relative to the beach crest elevation for single, shore-parallel structures. The many noted durability issues and ineffectiveness as mitigating erosion indicates that existing design methods for anchored LWD have not generally been effective at providing coastal protection and meeting engineering design life requirements.
A comprehensive set of over 60 experimental tests were completed as part of the overall research program. Thirty-two (32) tests were analyzed as part of this study relating to the morphological response of a gravel beach with and without various LWD configurations. The tests were conducted within a wave flume at the National Research Council’s Ocean, Coastal and River Engineering Research Centre (NRC-OCRE), at a large scale (5:1) based on site characteristics and LWD design characteristics made during the previous field investigations. Tests were also conducted to assess experiment repeatability, sensitivity to test duration, sensitivity to wave height, wave period, and relative water level, influence of regular waves, and influence of log roughness. The position of the most seaward LWD (whether considering distance or elevation) was found to be strongly linked to morphological response. A theoretical relationship was developed between LWD elevation and sediment volume change. Configurations which included LWD placement below the still water level, such as the Benched configuration, were found to be most effective at stabilizing the beach profile.
As part of the experimental modeling program, 24 tests were also conducted for the purpose of estimating the effect of LWD design configuration on wave run-up. In total, six different beach and LWD configurations were tested under a base set of four regular wave conditions. The study findings indicated that anchored LWD may increase wave run-up relative to a gravel beach with no structures. In particular, configurations with more logs tended to result in higher wave run-up. However, additional research is needed on the effect of LWD on wave run-up to confirm and expand these findings.
There are a number of potential engineering, ecological, social, and economic benefits associated with anchored LWD installations if designed, installed, and monitored appropriately for the site conditions and user needs. To realize these potential benefits, significant additional research is needed on the topic. One of the most significant barriers to usage is a lack of information on how to effectively anchor LWD structures. However, this research project provides a baseline for future comprehensive studies on the effect and design of coastal protection using LWD. The project provides preliminary design considerations for the usage of LWD as coastal protection and contributes to the growing body of literature on nature-based solutions.
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Wallerstein, Nicholas Paul. "Impact of Large Woody Debris on fluvial processes and channel geomorphology in unstable sand-bed rivers." Thesis, University of Nottingham, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.311841.
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Scherer, Robert Andrew. "The effects of wildfire disturbance and streamside clearcut harvesting on instream wood and small stream geomorphology in south-central British Columbia." Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/3391.
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Few field studies have assessed the temporal and spatial dynamics of wood in small streams (bankfull widths < 5 m) flowing through forest ecosystems dominated by stand replacing wildfires. Comparisons of instream wood loads associated with clearcut harvesting, wildfire, and undisturbed, old forests are also scarce. The two main objectives of this research were: (1) to document the temporal and spatial variability of wood and its geomorphic role in relation to stand development stage; and (2) to compare wood loads and its geomorphic role in relation to streamside clearcut harvesting, wildfires and older, undisturbed forest stands. This research focused on 38 small streams with gradients less than 14% situated in the plateau regions of south-central British Columbia, Canada.
A distinct temporal trend in wood loading was observed, with elevated volumes present 30-50 years subsequent to the wildfire disturbances following a “reverse J-shaped” trend in relation to time since the last major wildfire disturbance. The number of wood pieces was highly variable and few of the wood characteristics exhibited a significant trend in relation to time since the last major wildfire disturbance. Except at the smallest spatial scale (<3 m segments longitudinally along the stream) the spatial distribution of wood followed a random pattern with no trend, indicating that wood loads are related to local wood recruitment processes associated with episodic or chronic tree mortality and low wood transport.
Instream wood volumes were three times higher in streams recently (30 – 50 years ago) disturbed by wildfire as compared to the older riparian forest stands, confirming that wildfire disturbance is an important mechanism to recruit wood into streams. No significant differences in wood loads were identified between the streamside clearcut streams and the wildfire-disturbed or older, undisturbed streams. The lack of reductions in wood loads are likely related to the low transport capacity of our study streams, retention of non-merchantable trees and recruitment of slash from harvesting. A lack of morphologic variability was observed in relation to the disturbances indicating that the streams included in this study are relatively robust and unresponsive to wildfire or streamside clearcut harvesting disturbances.
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Samuelsson, Valdemar. "Fjärranalys av kantzoner och död ved i Natura 2000- vattendrag : Hur har det förändrats över tid?" Thesis, Umeå universitet, Institutionen för ekologi, miljö och geovetenskap, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-161041.
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The forestry is the main use of forests in Sweden which results in a number of positive aspects but also a number of negative effects on our nature. Aquatic ecosystems are specifically exposed to land use by the forest industry. The problem areas that arise are mainly discharge of nutrients, mercury, change in hydromorphology and local environment, sludge transport, absence of dead wood in streams and altered solar radiation. In order to reduce negative impact and protect natural populations of species but also to protect important ecosystems, there are a number of national prospective objectives and laws. From the year 2014, a number of prospective aims have been introduced to get a common view of the problem factors, but also to get a common representation of how the forestry measures should be carried out. This work evaluated the width of the riparian buffer zone left along the 138 streams at final clearcutting in the Vindelälven catchment, comparing three periods: period 1 (year 2001-2007), period 2 (year 2008-2013) and period 3 (year 2014-2018). The work also included a count of the number of dead wood objects that occur in 16 of the 138 streams in the study area. The method of the study is based on remote sensing using ArcGIS software, along with a field inventory to verify the remote sensing with reality. The results found from the study were that a significant increase in average minimum-width was shown between periods 1 and 3 (ANOVA, n = 138, df = 2, F = 5.083 and p = 0.007). The results from the average width were not significantly different but suggest a positive correlation between lower age of final clearcutting and the average width of the riparian zone. The density of dead wood in the streams of the study site did not give any significant differences or correlations depending on time period. What could be explained from the result was that the presence of beaver (Castor fiber) positively affected the amount of dead wood. To conclude, positive effects of the introduction of new objectives for riparian buffer zone management were indicated. This is a sign that the forestry industry is moving towards implementing more sustainable methods. In addition, a method based on remote sensing for measuring riparian buffer zone widths was found to provide reliable estimates in the Vindelälven catchment, Västerbotten County.<br>Grip on Life IP
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Minckley, W. L., and John N. Rinne. "Large Woody Debris in Hot-Desert Streams: An Historical Perspective." University of Arizona (Tucson, AZ), 1985. http://hdl.handle.net/10150/554222.
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Large-particulate organic debris is denied to present-day desert streams because of interception by impoundments and as a result of decimation of formerly extensive riparian vegetation. Historical records indicate a substantial, but sporadic, input of coarse debris, which was reduced to finer particles through molar action in canyon-bound reaches of desert rivers. Historical changes, functions of large debris in the systems, and probable future conditions are reviewed.
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Linstead, Conor. "The influences of large woody debris on British headwater streams." Thesis, University of Birmingham, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.368996.
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This thesis examines the influence of large woody debris (LWD) on the physical habitat of British headwater streams. The distribution and density of LWD accumulations throughout catchments is considered using data from the River Habitat Survey (RHS) and more detailed catchment scale surveys. The effect of accumulations of LWD on stream hydraulics and physical habitat at a reach scale is examined using transect based measurements of depth and velocity over a range of discharges before and after LWD removal for two reaches, measurement of reach average hydraulic parameters for 25 reaches with differing levels of LWD and the application of the Aggregated Dead Zone (ADZ) and Physical Habitat Simulation (PHABSIM) models. The RHS and catchment scale surveys showed that LWD accumulations exhibit systematic patterns in abundance within catchments, smaller streams having a higher density of LWD and a greater number of LWD accumulations. The most hydraulically active type of LWD accumulations were found to reduce flow velocity by an average of 55%, increase channel roughness by 149% and increase depth by 165%. This impact was, however, found to vary with discharge. Application of the Aggregated Dead Zone (ADZ) model showed that LWD increases the volume of ADZ, which may indicate greater ecological refuge potential. Using the Physical Habitat Simulation (PHABSIM) model, it was found that LWD improved habitat quality and overall habitat diversity.
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Thompson, M. "The effect of large woody debris restoration on stream ecosystems." Thesis, University College London (University of London), 2014. http://discovery.ucl.ac.uk/1455018/.
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The natural physical and biological states of rivers have been altered increasingly by habitat modification and pollution. Successful river restoration is therefore critical for mitigating impacts on river ecosystems. However, restorations are typically constrained to small patches within individual rivers and often lack standardised or adequate monitoring and assessment. This has led to poor diagnosis of both the “problem” and the effectiveness of the “solution” as comparable data are rare. In a literature review and meta-analysis I identified three areas limiting the development of river restoration as a science: 1) prior monitoring to determine the chief ecological constraint was not common practice; 2) the primary driver for restoration was ecological (e.g. an increase in biodiversity) but monitoring was often inadequate to detect ecological response to restoration or not undertaken; 3) target species (e.g. brown trout) or assemblages (e.g. invertebrates) are often the focus of monitoring, but it is not yet clear how habitat restoration affects more complex organisational levels (e.g. food webs, community mass-abundance scaling, ecosystems) and how this regulates populations of target taxa. These three areas were the focus of the subsequent data chapters. Conserving naturally fallen large woody debris (LWD) in rivers and felling trees to mimic LWD is one current vogue in river restoration-management thought to increase habitat diversity and positively correlate with increasing invertebrate biodiversity. Invertebrates were sampled between reaches with and without LWD and across a nutrient gradient, which included 19 base-rich streams, to test whether the chief determinant of invertebrate density and composition was either habitat quality or water quality. Five chalk streams were sampled before and after at control, reference (i.e. natural LWD) and treatment (i.e. felled) sites to test for a general restoration effect. A combination of spatially nested scales (i.e. stream-reach-habitat), invertebrate structural measures (e.g. α-diversity, abundance and biomass) and food web metrics (e.g. trivariate analysis) have been tested so that the ecological impact of restoration could be quantified. Large-scale pressures, namely fine sediment and orthophosphate (and their potential covariates) were impacting invertebrate community structure. Quantitative estimates of abundance and biomass increased within LWD habitat and reference reaches respectively. Evenness, α- and β-diversity were not significantly higher in restored LWD. Community mass-abundance scaling was not affected by either experimental or natural LWD. This implies that LWD is having an effect, but this is restricted to the invertebrate community. Many of the patterns decribed here would not have been detected using standard protocol methods (e.g. invertebrate kick net sampling). This highlights the need for the development of standardised biomonitoring practices that are able to diagnose root causes of degradation and demonstrate ecological recovery following restoration. If the aim of restoration is to predictably increase fishes biomass or biodiversity, for example, I anticipate larger-scale restorations, which address multiple stressors, and longer-term monitoring will be needed.
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Dahlström, Niklas. "Function and dynamics of woody debris in boreal forest streams." Doctoral thesis, Umeå University, Ecology and Environmental Science, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-425.
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<p>The work in this thesis deals with (1) the effects of woody debris on stream channel morphology and retention of organic material, and (2) the dynamics of woody debris and its relation to riparian forest history and composition. The studied stream reaches are situated in mature, productive forests in the boreal zone of Sweden.</p><p>Wood variables were important predictors of the frequency of debris dams, pool area, the proportion of pools formed by wood, and variation in the bankfull channel width. Pools formed by woody debris were mainly created by damming and had larger surface areas and residual depths than pools formed by other agents. Stream reaches intersecting old-growth forest (with minor influence of forest management) had coarser and longer woody debris pieces, greater amounts of wood, more debris dams, and wood-formed pools compared to streams surrounded by forests influenced by selective logging.</p><p>The influence of past forest management on the quality and quantity of woody debris in streams were analyzed by using dendrochrnological methods. Selective loggings and absence of forest fires after 1831 resulted in lower input rates and a gradual replacement of pine by sruce over time. Residence times in stream channels of woody debris (>10 cm in basal diameter) were long and the oldest dated pieces of pine and spruce were over 300 and 100 years, respectively.</p><p>Dynamics of woody debris were explored by comparing wood volumes and characteristics between stream channels and their riparianforests and between old growth and managed sites. Wood volumes recorded in the stream channels exceeded, but were related to, the volumes found in the riparian forests. Limited input of woody debris by bank cutting and absence of slope processes suggest that recruitment processes of woody debri to stream channels are similar as in riparian forests and slow decay in channels results in greater volumes.</p><p>The retentiveness of organic material in stream channels was examined by using release and capture experiments in multiple reaces during varying discharges using different sizes of leaf mimics. Sixty eight percent of the variation in retention was explained by a multiple regression model including discharge and leaf mimic siz. Between 44 and 80% of the variation in retention among reaches was explained by channel constraint, gravel coverage, and woody debris variables as the most important. Estimates from a partial least squares (PLS) model suggest an increase in mean transport distances by 22 to 53% in managed forest streams compared to old growth conditions and in a low wood scenario, mean transport distances increased by 38 to 99% with larger increases for higher discharges and larger particle sizes.</p><p>To regain more pristine conditions of stream channels, management and restoration are needed to increase the amount of woody debris that recreates lost channel structures and increaes the retention of organic material.</p>
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Latterell, Joshua J. "The natural history and dynamics of large wood in the Queets River, Washington /." Thesis, Connect to this title online; UW restricted, 2005. http://hdl.handle.net/1773/5273.
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Fox, Martin J. "Spatial organization, position, and source characteristics of large woody debris in natural systems /." Thesis, Connect to this title online; UW restricted, 2003. http://hdl.handle.net/1773/5463.
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Bambrick, Beth Marie. "Large Woody Debris Mobility Areas in a Coastal Old-Growth Forest Stream, Oregon." PDXScholar, 2013. https://pdxscholar.library.pdx.edu/open_access_etds/658.
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This study uses a spatial model to visualize LWD mobility areas in an approximate 1km reach of Cummins Creek, a fourth-order stream flowing through an old-growth Sitka spruce-western hemlock forest in the Oregon Coast Range. The model solves a LWD incipient motion equation for nine wood size combinations (0.1m, 0.4m, 1.7m diameters by 1.0m, 6.87m, 47.2m lengths) during the 2-year, 10-year, and 100-year discharge events. Model input variables were derived from a combination of field survey, remotely sensed, and modeled data collected or derived between June 2010 and July 2011. LWD mobility map results indicate the 2-year discharge mobilizes all modeled diameters, but mobile piece lengths are shorter than the bankfull channel boundary. Mobility areas for each wood size combination increases with discharge; 10-year and 100-year discharge events mobilize wood longer than average bankfull width within a confined section of the main stem channel, and mobilize LWD shorter than bankfull width within the main stem channel, side channels, and floodplain. No discharge event mobilizes the largest LWD size combination (1.7m / 47.2). Recruitment process was recorded for all LWD during June 2010, revealing that all mobile wood in the study reach was shorter than bankfull width. Based on these conflicting results, I hypothesize the distribution of wood in Cummins Creek can be described in terms of discharge frequency and magnitude, instead of as a binary mobile/stable classification. Mobility maps could be a useful tool for land managers using LWD as part of a stream restoration or conservation plan, but will require additional calibration.
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Roberts, Brianna. "Geomorphic function of large woody debris within a headwater tallgrass prairie stream network." Thesis, Kansas State University, 2014. http://hdl.handle.net/2097/18207.
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Master of Arts<br>Department of Geography<br>Melinda Daniels<br>Large woody debris, (LWD), defined as pieces measuring ≥ 1 meter in length and ≥ 10
centimeters in diameter (Swanson and Lienkaemper, 1978; Marston, 1982) is an influential
stream component. Once stable LWD obstructs streamflow and regulates key processes, causing
increases in storage capacity, scouring, and variations to the bed, the extent contingent upon
LWD’s average length of residence time within a system. Several North American studies have
acknowledged the effects of interactions between wood, sediment, and flow regimes (Bilby,
1981; Keller, E.A., and Swanson, F.J., 1979; Montgomery et al., 1995; Wohl, E., 2008), linking
the triad to geomorphic changes, the redistribution of bed materials, and ecological benefits. A
consensual baseline reference for LWD’s function over time does not exist however, partly due
to previous research being primarily conducted in the Northeast and Pacific Northwest regions
where historic actions of humans, particularly riparian logging and stream clearing, have greatly
impacted the condition of the watersheds. Researchers having long-overlooked the Great Plains
and other regions not commonly associated with woody vegetation has increased the ambiguity
regarding the transferability of LWD findings between regions. By shifting the focus to a non-forested
region, the goal of this thesis is to measure the dynamics and influence of a prairie
stream’s wood load on sediment storage and bed morphology. The Kings Creek network study
area is located on the Konza Prairie Biological Station in northeastern Kansas, and drains one of
few remaining unaltered North American watersheds. Results document the ongoing forest
expansion into the surrounding pristine grassland, and provide a temporal context of the regions
changing climate representative of atypical stream conditions caused by drought. In total, 406
individual pieces of wood were measured. The wood load was lower than most forest streams
referenced (13.05 m[superscript]³/100 m), though higher than expected resulting from the absence of
streamflow. LWD stored 108 m[superscript]³ of sediment within the channel, and the cumulative volume of
LWD-formed pools was 169 m[superscript]³. Additionally, statistical analysis showed longitudinal bed
variations to be strongly associated to LWD abundance, further indicating that LWD influences
prairie stream processes similarly to those in a forest stream.
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Hess, Jacquelyn Marie. "Distribution and residence times of large woody debris along South River, Shenandoah Valley, Virginia." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 184 p, 2007. http://proquest.umi.com/pqdweb?did=1400957071&sid=6&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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Vergaro, Alexandra [Verfasser], and A. [Akademischer Betreuer] Dittrich. "Large woody debris in river channels - hazard and dynamics / Alexandra Vergaro ; Betreuer: A. Dittrich." Braunschweig : Technische Universität Braunschweig, 2015. http://d-nb.info/1175819948/34.
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Hilderbrand, Robert Howard. "Relations between large woody debris, physical habitat, and benthic macroinvertebrates in Appalachian mountain streams." Thesis, This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-06082009-170744/.
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Klungle, Matthew M. "An evaluation of large woody debris restorations on the Manistee and Au Sable rivers, Michigan." Diss., Connect to online resource - MSU authorized users, 2006.
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Johnson, Elizabeth. "Hydraulic and Geomorphic Effects of Large Woody Debris Additions in the Narraguagus River Watershed, Coastal Maine." Thesis, Boston College, 2009. http://hdl.handle.net/2345/996.
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Thesis advisor: Noah P. Snyder<br>Thesis advisor: Gail C. Kineke<br>Maine coastal rivers host the last remaining runs of endangered anadromous Atlantic salmon in the United States, whose populations have decline from ~500,000 returning adults in the 1880s to only ~1000 in 2000. Restoration projects have focused on these coastal river systems to bring natural populations back to the area, and recent efforts involve adding large woody debris (LWD) to small tributaries to improve salmon rearing habitat. Large woody debris actively changes the hydraulics and geomorphology of small streams by acting as a barrier to flow and creating decreased velocity zones, scour pools, and sediment storage and sorting. I study the effects of LWD additions in early August 2008 on hydraulics and substrate in Baker Brook, a west-flowing tributary of the Narraguagus River. Hydraulically, I focus on the treatment reach nearest the confluence with the Narraguagus River (Baker1), and I also study changes in substrate in Baker1 and the upstream treatment location (Baker3). Both study locations are divided into two reaches, treatment (Baker1-T and Baker3-T) and control (Baker1-C and Baker3-C). In Baker1, the treatment and control reaches are further divided into four 50 m sub-reaches based on channel gradient (~1% in Baker1-C-Flat and Baker1-T-Flat; >2% in Baker1-C-Steep and Baker1-T-Steep). In Baker3, we use two 50 m sub-reaches of similar gradient (ranges from ~1% to 2%) to determine substrate changes. Significant post-LWD addition changes are determined by comparison with the control sub-reaches. Changes in the treatment sub-reaches must be larger than those in the control sub-reaches to be deemed significant. I seek to answer three research questions: (1) how much does mean velocity through the study sub-reaches change as a result of additions; (2) how much does hydraulic roughness change; and (3) does sediment storage and spatial sorting result from the LWD additions? I measured reach-average velocities (Ureach) in Baker1 using the salt dilution method in May, July and August 2008 and May 2009. I use rating curves to compare the post-treatment to the pre-treatment Ureach-stage relationship. A temporary decrease in Ureach occurred in October 2008 in Baker1-T-Flat, whereas the other sub-reaches experienced no change in Ureach. A localized change in cross-sectionally averaged velocity (U) measured with a flow meter, is also evident at Baker1-T-Flat, but this is because an added tree lies directly in the downstream cross-section where measurements are recorded. I assessed channel roughness changes by comparing roughness rating curves created using the Manning roughness parameter, n (back-calculated from velocity measurements) for each sub-reach. Because of the short-term decrease in Ureach, roughness increased in Baker1-T-Flat in October 2008 as well. No change in roughness is evident in the other sub-reaches because post-treatment values of n plot on the same decreasing trend with respect to stage as pre-treatment values. I quantified pre- and post-treatment sub-reach substrate median grain size (D50) with intensive clast counts in July 2008 and May 2009. In Baker1, analysis of pre-treatment substrate size show that the flat sub-reaches have a finer substrate size (34-38 mm) than the steep sub-reaches (88-134 mm). Baker3 pre-treatment grain size is similar to that of the flat Baker1 sub-reaches, with a median grain size of 38 mm in Baker3-T and 28 mm in Baker3-C. Two of the three treatment sub-reaches exhibited significant fining (D50 decreased by 37-54%) between the surveys, and the third changed less than measurement uncertainty. One of the three control sub-reaches coarsened significantly (D50 increased by 29%), one fined significantly (-42%), and one coarsened less than measurement uncertainty. In summary, I find that LWD additions in Baker Brook had little effect on reach-scale hydraulics during the flows we observed, but did influence bed-grain size during the 10-month study interval, underscoring the importance of floods on channel change<br>Thesis (MS) — Boston College, 2009<br>Submitted to: Boston College. Graduate School of Arts and Sciences<br>Discipline: Geology and Geophysics
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Treadwell, Simon Andrew 1968. "Patterns in community metabolism and biomass of biofilms colonising large woody debris along an Australian lowland river." Monash University, Dept. of Biological Sciences, 2002. http://arrow.monash.edu.au/hdl/1959.1/5605.
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Perry, Brian. "A Physical and Numerical Model Investigation of a River Flow Diversion and Assessment of Large Woody Debris Types." Thesis, Université d'Ottawa / University of Ottawa, 2018. http://hdl.handle.net/10393/38581.
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The extreme flooding event that occurred in 2013 in Alberta, Canada was at time the most costly natural hazard event in the nation’s history with damages exceeding $5 billion. Due to this event, an increased effort for flood mitigation strategies began and resulted in the proposal of the Springbank Off-Stream Storage Reservoir to divert and detain Elbow River flow upstream of the City of Calgary. In order to validate the design of the flow diversion structures, a large (1:16) scale physical model was constructed. The model tested among other things, the impact of large woody debris (LWD) on the flow diversion structures. The LWD modelling included a comparison of LWD manufactured from smooth cylindrical dowels versus natural tree limbs of the same dimensions. The results from the physical model led to a series of design changes for the diversion structures that likely would not have been identified without physical modelling. The LWD material comparison demonstrated significantly different behaviours between LWD types. Specifically, LWD manufactured from natural tree limbs was significantly more likely to accumulate in debris dams on the diversion structures. The impact of root wad was also investigated and proved to play a major role in the damming characteristics and blocking probability of debris. Following the physical model investigations, a numerical simulation was completed in order to examine further the hydrodynamic results obtained from the Springbank project. Using TELEMAC MASCARET’s open source free surface flow program TELEMAC 2D, a two dimensional simulation was completed using data from the physical model. Flowrates and velocities from both models were compared and discrepancies between the two are identified. Reasoning for these differences as well as future works for the numerical model are presented.
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Turcotte, Benoit. "Large smooth cylindrical elements located in a rectangular channel : upstream hydraulic conditions and drag force evaluation." Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/2477.
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Classical approaches to evaluate the stability of large woody debris (LWD) introduced in streams for habitat restoration or flood management purposes are usually based on inappropriate assumptions and hydraulic equations. Results suggest that the physics of small cylindrical elements located in large channels cannot be transferred to the case of a large roughness elements placed in small channels. The introduction of LWD in a small channel can generate a significant modification of the upstream hydraulic conditions. This modification has direct implications on the stability of the LWD.
Experiments were performed in a controlled environment: a small stream section was represented by a low roughness rectangular flume and LWD were modeled with smooth PVC cylinders. Direct force measurements were performed with a load cell and results were used to identify an equation that evaluates the drag force acting on a large cylindrical element place in a rectangular channel. This equation does not depend on a drag coefficient. Water depths were also measured during the experiments and results were used to develop an approach that evaluates the upstream hydraulic impacts of a large cylinder introduced in a rectangular channel. The effect of the variation of the unit discharge (discharge per unit of width), cylinder size, cylinder elevation from the channel bed, and downstream hydraulic conditions, could be related to the upstream hydraulic conditions with relative success. Dimensionless parameters were developed to increase the versatility of the approach.
The application of this approach to field cases is expected to require adjustments, mainly because of the roughness of natural environments differs from the smoothness of the controlled environment described in this work.
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Camp, Reid. "Short Term Effectiveness of High Density Large Woody Debris in Asotin Creek as a Cheap and Cheerful Restoration Restoration Action." DigitalCommons@USU, 2015. https://digitalcommons.usu.edu/etd/4417.
Full textAbstract:
In response to human impacts, river restoration and rehabilitation actions have become a priority in the United States. In the Pacific Northwest, most restoration actions are focused on repairing degraded freshwater habitat to increase or improve Pacific salmonid production. However, traditional river restoration actions remained largely unchanged for over 100 years despite a lack of definitive evidence that the actions were effective. More recently, there has been a surge in process-based restoration actions, which aim to reestablish the physical and biological processes that maintain fluvial and floodplain environments by targeting the root causes of degradation in a watershed. Cheap and cheerful restoration projects focus on restoration actions that are low impact and cost effective, can be implemented over large scales, and target degraded processes. However, because cheap and cheerful restoration is a relatively new method, the success of these types of projects has not been assessed.
To address this issue, I studied the short-term physical effectiveness of a type of cheap and cheerful restoration that uses high density large woody debris (HDLWD) to restore instream habitat complexity in two wadeable tributaries to Asotin Creek in southeast Washington State. My specific research objectives included (1) assessing hydraulic and geomorphic responses in the stream channel imposed by restoration structures, (2) quantifying the changes to geomorphic channel unit assemblages post restoration, (3) quantifying changes in sediment storage post restoration, and (4) developing a geomorphic condition assessment of Asotin Creek using the River Styles Framework. Additionally, I developed a mobile database application (app) to facilitate data collection using a novel rapid restoration effectiveness assessment survey.
Through analysis and a thorough review of the land use history in Asotin Creek, I determined that much of the watershed is in poor geomorphic condition based on the River Styles Framework for river classification. Many stream reaches have been degraded from their historic condition and often lack habitat complexity associated with suitable rearing habitat for juvenile salmonids. My results indicate that the structures are impose several immediate hydraulic responses following installation. These hydraulic responses increase hydraulic roughness, which results in predictable geomorphic responses following high flow events. Following restoration, the number and area of pools and bars significantly increased within treatment sites, while the number and area of planar units decreased. Likewise, it appears that the addition of the structures has led to a 25% increase in depositional volume at treatment sites compared to control sites.
Results from the rapid assessment approach supported the more vetted approaches used to assess the efficacy of the treatment. However, the viability of the app and rapid protocol indicate that inter-observer variability may be high, and estimates of geomorphic unit area are not entirely consistent with the vetted approaches. Analysis of the rapid assessment approach revealed pertinent improvements to the app and rapid protocol that will be made in the future.
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Alexander, Michelle M., and John N. Rinne. "Preliminary Observations on the Transportation of Large Woody Organic Debris in Burned and Unburned Headwater Streams, Tonto National Forest, Arizona." Arizona-Nevada Academy of Science, 1995. http://hdl.handle.net/10150/296458.
Full textAbstract:
From the Proceedings of the 1995 Meetings of the Arizona Section - American Water Resources Association and the Hydrology Section - Arizona-Nevada Academy of Science - April 22, 1995, Northern Arizona University, Flagstaff, Arizona
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Allen, Kelly Harpster. "Short-term response of physical habitat and fish to the addition of large woody debris in two Appalachian Mountain streams." Thesis, This resource online, 1998. http://scholar.lib.vt.edu/theses/available/etd-08252008-162213/.
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Russell, Gabrielle Nicole. "The Impact of Woody Debris on Bank Stability and Macroinvertebrates in IntermittentHeadwater Streams within the Western Allegheny Plateau." Ohio University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1524857157950265.
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Theobald, Dylan Robert. "Evaluation of Red Alder Mortality in the Little Creek Watershed Following the 2009 Lockheed Fire." DigitalCommons@CalPoly, 2014. https://digitalcommons.calpoly.edu/theses/1170.
Full textAbstract:
Five hundred eighty red alder along a 2.16 km portion of the Little Creek riparian zone were assessed for mortality following the 2009 Lockheed Fire near Davenport, California. The study area was divided into burn severity zones and every red alder within the riparian zone was observed and assessed for mortality. Height, diameter at breast height (DBH), and age were collected on selected trees. An estimation of red alder large woody debris (LWD) input to Little Creek since a 2010 LWD survey (Smith, 2010) was calculated using average red alder tree dimensions applied to Smalian’s formula (MLNRO, 2011). The mean proportion of dead red alder in the non-burn zone and burn-zone was .11 and .45 respectively. Volume of red alder LWD in Little Creek is estimated to have increased approximately 245% since the fire. Given other factors may have played a role in red alder mortality in Little Creek, the analysis reported here supports fire also contributed to accelerated mortality of red alder established following the catastrophic debris torrent in 1955 in Little Creek. This study provides useful information regarding fire and red alder and establishes baseline conditions of the Little Creek riparian zone following the 2009 Lockheed Fire.
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Soltesz, Paul J. "Large Wood Dynamics in Central Appalachian Hemlock Headwater Ravines." The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1408703567.
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Chapman, Linnaea R. A. "The long-term availability of large woody debris in logged stream channels and second-growth riparian forests on the west coast of Vancouver Island." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/MQ39179.pdf.
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Sass, Emma. "Lasting Legacies of Hurricane, Harvesting, and Salvage Logging Disturbance on Succession and Structural Development in an Old-Growth Tsuga canadensis-Pinus strobus Forest." ScholarWorks @ UVM, 2017. http://scholarworks.uvm.edu/graddis/817.
Full textAbstract:
Disturbance events affect forest composition and structure across a range of spatial and temporal scales, and forest development may differ after natural, anthropogenic, or compound disturbances. Following large, natural disturbances, salvage logging is a common yet controversial management practice around the globe. While the short-term impacts of salvage logging have been studied in many systems, the long-term effects remain unclear. Further, while natural disturbances create many persistent and unique microsite conditions, little is known about the long-term influence of microsites on forest development. We capitalized on over eighty years of data on stand development following the 1938 hurricane in New England to provide the longest known evaluation of salvage logging impacts, as well as to highlight developmental trajectories for eastern hemlock (Tsuga canadensis)-white pine (Pinus strobus) forests under a variety of disturbance histories. Eight decades following disturbance, there were no differences in current overstory composition between areas that were logged, hurricane disturbed, or hurricane disturbed and salvage logged, but white pine declined across most sites. In contrast, structural characteristics remain distinct between the three management histories. In the unsalvaged area, the diversity of microsites and the coverage of uprootings and pits influenced overstory tree composition, diversity, and structural characteristics. These findings underscore the long-term influence of salvage logging on forest development and the importance of natural disturbance-mediated microsite conditions on tree species growth and survival. Future salvage logging efforts should consider these impacts and provide a greater range of unsalvaged areas across the landscape to maintain these important structural legacies over the long term.
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Chen, Guan-hong, and 陳冠宏. "The Spatial Distribution Characteristics of Large Woody Debris (LWD) in the Mountain Stream of Central Taiwan." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/42025773713139315412.
Full textAbstract:
碩士<br>逢甲大學<br>水利工程與資源保育研究所<br>96<br>The forest resources in high mountain area are variety and wide, which also passed through by some streams. LWD in the steam is caused by the wood forest of natural death, landslide, wild fire, and other cautions. According to the Count of Veterans Affairs Commission, the erosion and the deposition of the Channel morphology is affected by the deposition of the 10% wood forest, which will become LWD in the stream every year. The function of the channel and habitat enhancement is proved by the examinations and the studies in the foreign countries. But, there are fewer references about it in Taiwan. This topic is aimed to study the spatital distribution characteristic of LWD in the channel of mountain area.
By the study，we get the effects of channel width and sinuosity are very obvious, but effect of slope is no longer obvious, and LWD deposion is strongly influenced by landslide area. According data, the LWD deposion are classified into five types. And we use Artificial Neural Network to construct a forecast model. The simple forecast model can forecast LWD deposion, and it have 80% higher accuracy.
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D’Aoust, Stephane G. "Large woody debris fish habitat structure performance and ballasting requirements." Thesis, 1998. http://hdl.handle.net/2429/8029.
Full textAbstract:
Many stream restoration efforts include placement of constructed large woody debris
(LWD) habitat structures. These structures are installed in stable channels to rehabilitate
summer habitat and critical overwintering refuges in streams, thus attenuating stresses on
the aquatic ecosystem until logged riparian areas naturally supply mature windfalls (Slaney
& Martin, 1997). This study addresses one of the main problems faced by restoration
practitioners: The lack of physically based design guidelines for LWD habitat structures.
This study presents the theoretical basis behind design methodologies for three types of
LWD structures: (1) Single-LWD, (2) Single-LWD with intact root wad, and (3) Multiple-
LWD structures. A field verification program was undertaken to test the applicability the
theoretical basis and to refine the design guidelines. Over 80 LWD structures were
assessed after construction and again after the fall 1997 to spring 1998 floods.
Results indicate that the design approach for single-LWD and single-LWD with root wad
structures, based on a factor of safety against sliding failure, successfully predicted the
stability of the structures during the past fall to spring floods. The stability of the multiple-
LWD structures proved to be more complex to predict since a greater number of design
and construction-related factors influence stability. Nonetheless, a design approach based
on a safety factor against buoyant failure is recommended.
Recommendations with respect to the design and construction of LWD structures are also
presented as part of this study.
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Wu, Hua-Shung, and 吳化祥. "An Experimental Study on the Characterization of Large Woody Debris Structures." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/36348329603829434201.
Full textAbstract:
碩士<br>逢甲大學<br>土木及水利工程所<br>93<br>Large Woody Debris Structure (LWDS) plays an important role in forest ecosystem. However, when LWDS falls into river, it will block flow and make the river width contracted such that the increasing flow velocity often causes bank erosion.
This experimental study first identifying the “transmission rate” of LWDS as indicator to define the flow rate passing through the structure under diverse conditions of flow and channel slope within straight channel. With various combinations of experimental factors, including no structure and concrete spur dike, this study tried to discover the characteristic of LWDS on bank protection length, maximum depth and position of scouring pool, channel bed stability, and diversity of bed forms. The major findings from model experiments were concluded as follows:
1.LWDS can protect efficiently channel banks
when transmission rate approaches to 90%.
2.With 1.5 degree channel slope and transmission
rate above 75%, both stabilities of channel
bed and banks reached the most stable
condition of all experimental combinations in
straight channel. However, the stability
falls when transmission rate increases to 90%.
3.LWDS can perform better ability on create
diverse river habitat environment under high
flow. The diversity of bed forms improved
most under the LWDS with transmission rate
between 80% to 90%.
Overall, to achieve the goals on improving bed form diversity and maintaining stable channel bed and banks, the experimental results of this study concluded that LWDS with transmission rate around 75% to 90% under 1.5 degree channel slope outperformed the other experimental combinations, including those with concrete spur dike.
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Grilliot, Michael J. "The role of large woody debris on sandy beach-dune morphodynamics." Thesis, 2019. http://hdl.handle.net/1828/10804.
Full textAbstract:
Coastal foredune evolution involves complex processes and controls. Although a great deal is known about the effects of vegetation cover, moisture, and fetch distance on sediment supply, and of topographic forcing on airflow dynamics, the role of large woody debris (LWD) as a modulator of sediment supply and a control on foredune growth is understudied. Large assemblages of LWD are common on beaches near forested watersheds and collectively have a degree of porosity that increases aerodynamic roughness and provides substantial sand trapping volume. To date, no research has attempted to understand the geomorphic role that LWD matrices, as a whole, have as roughness elements affecting airflow and sediment transport across a beach-dune system, or, what the long-term implications of these impacts are on beach and foredune erosion recovery and evolution. This four-year research initiative investigated the role of a LWD matrix on beach-dune morphodynamics on West Beach, Calvert Island on the central coast of British Columbia, Canada.
This study integrated data from research that spanned three temporal scales, 1) event-scale (10 min) flow and sediment transport patterns, 2) daily frequency and relative magnitude of landscape changing events, 3) seasonal to interannual-scale volumetric and LWD changes. An event-scale experiment to characterise airflow dynamics and related sand transport patterns showed that LWD distinctly alters wind flow patterns and turbulence levels from that of incoming flow over a flat beach. Overall, mean wind speed and fluctuating flow properties declined as wind transitioned across the LWD. Streamwise mean energy was converted to turbulent energy, however, the reductions in mean flow properties were too great for the increased streamwise turbulence to have an effect on transport. In response to these flow alterations and more limited sand transport pathways to the foredune, sediment flux was reduced by 99% in the LWD compared to the open beach, thereby reducing sand supply to the foredune. Sand grains rebounding off of the LWD were carried higher into the flow field resulting in greater mass flux recorded at 20-50 cm in the LWD as opposed to the flat beach. This effect was only recorded 6 m into the LWD. As such, LWD has the potential to modulate rates of foredune recovery, growth, and evolution.
Time-lapse photography collected at 15 min intervals during the study revealed that storm events lead to wave-induced erosion of the backshore and reworking of the LWD matrix. The exposed LWD matrix subsequently traps aeolian sediment that leads to rapid burial of the LWD and building of a raised platform for emergent vegetation. However, infilling of the accommodation space within the LWD matrix is so rapid, that sediment starvation of the foredune is short-lived. While the LWD at this site does trap sediment in the backshore, helping to protect the dune from scarping, LWD at this study site maintains an overall lower impact on transport to the foredune. Critical to this relationship is the frequency and magnitude of nearshore events that erode the beach periodically and re-organize the LWD matrix, which directly impacts the ability of LWD to store sediment and modulate transport to the foredune. A conceptual model exploring these relationships is presented.<br>Graduate
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Robison, E. George. "Large woody debris and channel morphology of undisturbed streams in southeast Alaska /." 1987. http://hdl.handle.net/1957/9757.
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Wang, Ci-Rong, and 王啟榮. "The Mechanism of Large Woody Debris Initial Entrainment in a Flume Experiment." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/98707309248305712100.
Full textAbstract:
碩士<br>國立中興大學<br>水土保持學系所<br>98<br>There has thus far been relatively little research into large woody debris (LWD) motion. The research was designed as a fixed bed flume experiment to explore the state of LWD critical entrainment, and discussed the initial flow condition was influenced by different length, diameter, orientation and bed roughness. Additionally, the theoretical model was developed to predict wood entrainment and compare predictor with experiment results.
The experiment results show that different orientations of wood will lead to different types of wood movement. For wood parallel to flow, the mechanism of motion features started by semi-floating and semi-sliding, because flow was gradually raised with the buoyant force increased and the friction force decreased until the wood moved to downstream. For wood oblique or perpendicular to flow, the mechanism of motion features started by rolling. Both the models and the experiments indicate that stable wood is significantly associated with wood angle relative to flow direction, the density of wood, wood diameter, channel slope and bed roughness. The wood stability is less sensitive to the choice of the apparent drag coefficient and wood length. Although previously reported as the most important factor in wood stability, wood length did not significantly affect the threshold of movement in the experiments or the model predictions, for wood shorter than channel width.
This research consists of sliding and rolling equilibrium equations to establish a prediction model of wood entrainment:
where dw is the flow depth for wood incipient motion, Llog is the wood length, Dlog is wood diameter, ρlog and ρw are the densities of wood and water, respectively, S is the channel slope (S=tanα), CD is the drag coefficient of the wood in water, ds is the bed grain size, θ is the angle of the wood relative to flow, and is the friction angle between wood and channel bed.
This prediction model is helpfully used for multiple angles of the wood relative to flow, and the flow depth for wood incipient motion could be predicted under the wood and channel characteristics are given. To compare model predictors with experiments, the bias account for about 10% of the wood diameter. Moreover, for wood oblique or perpendicular to flow, the bias only account for about 5% of the wood diameter. According to the results, the prediction model is relative successfully at predicting depths for wood incipient motion.
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Long, Barry A. "Recruitment and abundance of large woody debris in an Oregon coastal stream system /." 1987. http://hdl.handle.net/1957/9555.
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Archer, Michael W. "Retention, movement, and the biotic response to large woody debris in the channelized Missouri River." 2009. http://digitalcommons.unl.edu/natresdiss/6.
Full textAbstract:
Thesis (M.S.)--University of Nebraska-Lincoln, 2009.<br>Title from title screen (site viewed June 8, 2010). PDF text: x, 116 p. : ill. (some col.). Publication: Dissertations & Theses in Natural Resources. Includes bibliographical references.
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Chou, Chia-Hsien, and 周佳賢. "An Experimental Study of Single Large Woody Debris Structure on the Change of Channel Morphology." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/81189270173320739112.
Full textAbstract:
碩士<br>逢甲大學<br>水利工程所<br>93<br>Even the flow deflector structures are useful on controlling channel banks erosion, the safety and its stability of the non-concrete deflector constructed by natural materials are still the major concerns for engineers and residents in Taiwan. Focused on the single flow deflector made of woody debris, this study tries to find the better structure configuration for considering the needs in structure safety, erosion control, and habitat enhancement through model experiments on concrete groyne, deflector log, and large woody debris. The flume experiments are undertaken with different experiment conditions of flow discharge, sediment composition, and channel slope. The experimental results indicated that the large woody debris is good at bulwark ability, channel steady and variety of habitat enhancement. The deflector log has good ability of variety of habitat enhancement in low flow discharge. As flow discharge increases, the concrete groyne and large woody debris perform better in variety of habitat enhancement and diversity. In structure safety, the concrete groyne and large woody debris are the better structures in bulwark ability while the flow energy increases. For these three structures, the large woody debris is the best structure in safety and habitat enhancement, while deflector log is concluded as the worst one.
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Braudrick, Christian A. "Entrainment, transport, and deposition of large woody debris in streams : results from a series of flume experiments." Thesis, 1997. http://hdl.handle.net/1957/33808.
Full textAbstract:
Although there has been extensive research on the geomorphic and ecologic role of
large woody debris (LWD) in streams, the dynamics of LWD in streams are poorly
known due to various measurement difficulties during floods. In this thesis I present the
results of two flume experiments on the dynamics of wood in streams. The first
experiment examined the effects of piece interaction on wood transport, while the second
evaluated a theoretical model predicting the threshold of movement, and factors
controlling the deposition of individual logs. Flume experiments allow us to model the
wood movement under a variety of piece geometries, piece concentrations, and hydraulic
conditions.
The first experiment showed that logs moved in three distinct transport regimes;
congested, semi-congested, and uncongested transport. During congested transport the
logs move as a single mass and occupy > 33 % of the channel area. Uncongested transport
occurs when the logs are moving as individuals and occupy < 10 % of the channel area.
Semi-congested transport is intermediate between these two transport regimes and occurs when wood moves in clumps of 2-3 logs. Transport regime was dependent upon the ration of the volumetric input rate of pieces to the flow, and to a lesser degree, the ratios of the piece length to channel width and piece diameter to channel depth. The transport regime was reflected in the deposit. Congested transport deposits have a higher portion of their pieces oriented parallel to flow than uncongested and semi-congested transport. We expect that congested transport will occur in low-order channels where input rates are high and channel geometry is small relative to piece size. Uncongested transport will dominate large channels where input rates are lower relative to flow and channel geometry is large relative to piece size.
Our theoretical model and these experiments indicate that the entrainment of individual logs was dependent upon the angle of the piece, and the presence/absence of rootwads. Although previously noted as a first-order control on piece movement, piece length had little effect on the entrainment threshold, but did affect the distance transported. The distance transported decreased with increases in the ratios of the piece length to average channel width (L[subscript log]/w[subscript av]), the piece length to the radius of curvature (L[subscript log]/R[subscript c]), and the piece diameter relative to average depth (D[subscript log]/D[subscript av]). These three ratios comprise the debris roughness. Increased debris roughness caused a general decrease in distance transported. Pieces with high debris roughness can travel further than predicted if they have high momentum, and over 50 % of their channel area deeper than the depth at which the piece floats. These results indicate that flume experiments and theoretical models, tools that have been extensively used to study sediment dynamics, are a useful in examining wood dynamics.<br>Graduation date: 1998
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Anderson, Jeffrey. "Morphodynamics of beach-dune systems laden with large woody debris: Haida Gwaii (Queen Charlotte Islands), British Columbia." Thesis, 2009. http://hdl.handle.net/1828/2252.
Full textAbstract:
This thesis explores the geomorphic implications of large woody debris (LWD) residing in the backshore of beach-dune systems along the northeastern coasts of Haida Gwaii (Queen Charlotte Islands), British Columbia, Canada. Detailed topographic surveys were employed to quantify seasonal mass balance of the beach-dune systems along two distinctly different coastlines. Erosion and accretion potential models were applied to characterize sediment transport conditions.
Holman’s (1986) R2% wave runup model was superimposed on total water levels, to model wave runup exceedence of the beach-dune junction elevation (6.5 m aCD). Modelled ‘erosion potential’ hours were demonstrated to correspond with observed erosion including removal of the LWD zone, resulting in decreased mass balance. Similarly, Fryberger and Dean’s (1979) Drift Potential model was used to model accretion potential hours. Modelled accretion potential hours were also able to effectively describe conditions when actual accretion occurred. The presence of LWD in the backshore offered two functions to the above processes: it acted effectively as an ‘accretion anchor’, promoting increased mass balance and rebuilding of the incipient foredune; and, it offered a mass of sediment fronting the foredune to protect the beach-dune system from storm wave attack and subsequent erosion.
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Miesbauer, Jean Marie. "An assessment of large woody debris, fish populations, and organic matter retention in upper midwestern forested streams." 2004. http://etd.nd.edu.lib-proxy.nd.edu/ETD-db/theses/available/etd-07072004-132201/.
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Powell, Sonya Rebecca. "A wood inventory and dendroecological analysis of large woody debris in small streams in the foothills model forest, Hinton, Alberta." Thesis, 2006. http://hdl.handle.net/2429/18103.
Full textAbstract:
This research explores large woody debris (LWD) dynamics in five 100-year old lodgepole pine-dominated and five > 100 year old spruce-dominated riparian forests of the Foothills Model Forest in west-central Alberta. The objectives of my research were (l) quantify the abundance and type of in-stream LWD in mature pine and spruce forests, (2) determine ages of in-stream LWD using tree-ring methods, (3) compare ages of LWD to the age structure of canopy trees to determine how disturbance and stand dynamics contribute to recruitment, and (4) quantify rates of decay and residence times by testing for differences in LWD abundance and volume among sites and among decay and position classes. To identify spatial aspects of LWD generation, I conducted a census of LWD within a 50m reach at each study site. Individual logs ranged from 0.01 to 0.88m³ ; total log volumes were 6.62 to 41.35 m³ per ha. For both pine and spruce, log volume decreased significantly between position classes and decay class for both species, largely due to change in the length of logs between classes. To identify temporal aspects of LWD generation, a dendroecological analysis was conducted. Two major disturbance types generated large woody debris in mature riparian forests. Lodgepole pine-dominated stands established ca. 1890 to 1900 after fires. During canopy closure, ca. 40 years after stand initiation, a pulse of tree mortality generated LWD. At the spruce-dominated sites, canopy trees established between 1730 and 1910. These stands were in later stages of stand development and within-stand disturbances generated LWD during the 1900s. I successfully estimated the year of death of 180 logs; 56% of estimates were high quality estimates from samples that included bark andlor sapwood. The age of LWD increased significantly with decay and position classes. The oldest LWD of lodgepole pine, white spruce and black spruce were 82, 137 and 80 years, respectively. Given the longevity of LWD, I conclude that management decisions that alter the abundance and rate of recruitment of LWD into streams have long-term implications for the structure and dynamics of riparian environments as well as in-stream habitat and biodiversity.<br>Arts, Faculty of<br>Geography, Department of<br>Graduate
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Sawyer, Audrey Hucks. "Complexity in river-groundwater exchange due to permeability heterogeneity, in-stream flow obstacles, and river stage fluctuations." Thesis, 2011. http://hdl.handle.net/2152/ETD-UT-2011-05-2805.
Full textAbstract:
River-groundwater exchange (hyporheic exchange) influences temperature, water
chemistry, and ecology within rivers and alluvial aquifers. Rates and patterns of
hyporheic exchange depend on riverbed permeability, pressure gradients created by
current-obstacle interactions, and river stage fluctuations. I demonstrate the response of
hyporheic exchange to three examples of these driving forces: fine-scale permeability
structure in cross-bedded sediment, current interactions with large woody debris (LWD),
and anthropogenic river stage fluctuations downstream of dams.
Using numerical simulations, I show that cross-bedded permeability structure
increases hyporheic path lengths and modifies solute residence times in bedforms. The
tails of residence time distributions conform to a power law in both cross-bedded and
internally homogeneous riverbed sediment. Current-bedform interactions are responsible
for the decade-scale tails, rather than permeability heterogeneity.
Like bedforms, wood debris interacts with currents and drives hyporheic exchange. Laboratory flume experiments and numerical simulations demonstrate that the
amplitude of the pressure wave (and thus hyporheic exchange) due to a channel-spanning log increases with channel Froude number and blockage ratio (log diameter : flow depth).
Upstream from LWD, downwelling water transports the river’s diel thermal signal deep into the sediment. Downstream, upwelling water forms a wedge of buffered
temperatures. Hyporheic exchange associated with LWD does not significantly impact diel surface water temperatures. I tested these fluid and heat flow relationships in a second-order stream in Valles Caldera National Preserve (NM). Log additions created alternating zones of upwelling and downwelling in a reach that was previously losing throughout. By clearing LWD from channels, humans have reduced hydrologic connectivity at the meter-scale and contributed to degradation of benthic and hyporheic habitats.
Dams also significantly alter hydrologic connectivity in modern rivers. Continuous water table measurements show that 15 km downstream of the Longhorn dam
(Austin, Texas), river stage fluctuations of almost 1 m induce a large, unsteady hyporheic
exchange zone within the bank. Dam-induced hyporheic exchange may impact thermal and geochemical budgets for regulated rivers. Together, these three case studies broaden our understanding of complex drivers of hyporheic exchange in small, natural streams as well as large, regulated rivers.<br>text
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Clark, Steven (Steven Michael). "Breeding site selection by coho salmon (Oncorhynchus kisutch) in relation to large wood additions and factors that drive reproductive success." Thesis, 2013. http://hdl.handle.net/1957/38182.
Full textAbstract:
The fitness of female Pacific salmon (Oncorhynchus spp.) with respect to breeding behavior can be partitioned into at least four components: survival to reproduction, competition for breeding sites, success of egg incubation, and suitability of the local environment near breeding sites for early rearing of juveniles. Accordingly, breeding sites should exhibit predictable habitat features linked to these components. In this study, I evaluated the relative influences of habitat features linked to fitness components on selection of breeding sites by coho salmon (Oncorhynchus kisutch). I also evaluated associations between breeding site selection and additions of large wood, as the latter were introduced into the study system as a means of restoring habitat conditions to benefit coho salmon. I used a model selection approach to organize specific habitat features into groupings reflecting fitness components and influences of large wood. The relative likelihood of each of these models was then evaluated based on how coho salmon were observed to select breeding sites. Specific variables examined within these models included depth at the redd, width to depth ratio, stream network location, proximity to other redds, maximum depth, proximity to a pool tail, and the count of naturally occurring and artificially placed large wood. Results of this work suggest that female coho salmon most likely select breeding sites based on habitat features linked to all four hypothesized fitness components. Linkages between large wood and breeding site selection were less clear, likely due to mismatches between the scale at which availability was quantified relative to the geomorphic influences of wood, insufficient time for wood to have geomorphic influences on habitat, or the directionality in which geomorphic effects are currently manifested (i.e., upstream, downstream, or bi-directional influences). Future work focused on geomorphic processes in this system could reveal stronger linkages between instream wood and the habitat features that coho salmon select for breeding.<br>Graduation date: 2013