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.

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. / text

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.

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. / Forestry, Faculty of / Graduate

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.

No description available.

No description available.

Large woody debris (LWD) was added to North Fork Stony Creek and North Prong Barbours Creek in southwest Virginia to inlprove fish habitat. The purposes of this study were to monitor stream channel response to the addition of LWD at a stream reach scale and at a local scale around individual logs, to evaluate changes in fish population parameters, and to observe microhabitat availability and use before and after L WD additions. In low-gradient Stony Creek, LWD was effective in modifying fish habitat through the formation of pools, the structuring of poo1/riffle sequences, and the enhancement of channel complexity. New pools formed from the break up of continuous rime habitat, increasing the overall number of habitat units and decreasing mean surface areas. Total pool area increased for both treatment sections, while changing little in the reference section where no logs were added. Localized scour and fill was observed for crosssectional transects around individual logs, creating a more heterogenous environment than in areas without logs. In contrast, physical habitat changed little in moderate-gradient Barbours Creek after L WD was added. An increase in the relative weight of brook trout in Barbours Creek suggested that although minimal channel changes were observed, logs may have increased channel complexity and cover, providing resting areas of lower velocities next to food pathways, which may have lead to decreased energy expenditure. Observations of microhabitat use revealed that unlike adult brook trout, juvenile brook trout used a limited range of depths and velocities. Adult brook trout shifted microhabitat use in response to changes in microhabitat available. Low numbers of fish in Stony Creek may have been related to low pH, but numbers of adult brook trout found in each section increased in 1994. With improved water quality, I believe that fish abundance in Stony Creek would increase through time because of the improved habitat. Although few significant changes were observed for available microhabitat in Stony Creek, changes in physical habitat suggest that over time shifts in microhabitat would be apparent. / Master of Science

Master of Arts / Department of Geography / Melinda Daniels / 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.