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• 1. [Article] Fluvial Wood Presence and Dynamics over a Thirty Year Interval in Forested Watersheds

  It has long been known that the presence of wood in rivers plays a vital biological and functional role and that a reciprocal relationship exists between woody material and the geomorphology of rivers. ...

  Citation × Citation Citation Abstract Copy Title: Fluvial Wood Presence and Dynamics over a Thirty Year Interval in Forested Watersheds Author: Atha, Jane Year: 2013 It has long been known that the presence of wood in rivers plays a vital biological and functional role and that a reciprocal relationship exists between woody material and the geomorphology of rivers. Fluvial wood studies, however, are rarely ongoing through time in order to ascertain long-term wood patterns within complete drainage networks. This dissertation addresses the temporal lag in fluvial wood patterns throughout four watersheds in the Oregon Coast Range by recreating a field dataset first collected in 1979 and then again in 1998. Statistical and spatial analysis of stream morphometric data at designated transects throughout the watersheds in addition to analysis of log step and log jam inventories provide insight into significant changes that have occurred over a thirty year interval at a multi-basin scale. These watersheds are located in areas that have been impacted by years of timber harvesting in the mid-twentieth century, however, clearcutting has been on the decline since the early 1980s. This research investigates the impacts that the legacy of clearcutting and subsequent afforestation has had on the abundance and volume of fluvial wood in the stream networks of these four watersheds. I digitized historical aerial imagery to determine the amounts of clearcutting in the basins over time. I integrated this variable with channel morphometric variables to assess predictors of wood abundance and volume through multiple regression analysis. Results show that the stream that has been the most affected by clearcutting has lower volumes of wood than measured in 1979 or 1998. Residence times of wood are short in these watersheds and wood abundance and volume was highly impacted by the debris flows that occurred during the Storm of 1996, prior to the 1998 data collection. There are statistically significant changes that have occurred in the stream morphology among the four watersheds. This dissertation also tests a method of detecting fluvial wood through airborne lidar analysis. This method provides an alternative to field surveys in areas of even the most extreme tree canopy cover. Title: Fluvial Wood Presence and Dynamics over a Thirty Year Interval in Forested Watersheds Author: Atha, Jane Year: 2013 It has long been known that the presence of wood in rivers plays a vital biological and functional role and that a reciprocal relationship exists between woody material and the geomorphology of rivers. Fluvial wood studies, however, are rarely ongoing through time in order to ascertain long-term wood patterns within complete drainage networks. This dissertation addresses the temporal lag in fluvial wood patterns throughout four watersheds in the Oregon Coast Range by recreating a field dataset first collected in 1979 and then again in 1998. Statistical and spatial analysis of stream morphometric data at designated transects throughout the watersheds in addition to analysis of log step and log jam inventories provide insight into significant changes that have occurred over a thirty year interval at a multi-basin scale. These watersheds are located in areas that have been impacted by years of timber harvesting in the mid-twentieth century, however, clearcutting has been on the decline since the early 1980s. This research investigates the impacts that the legacy of clearcutting and subsequent afforestation has had on the abundance and volume of fluvial wood in the stream networks of these four watersheds. I digitized historical aerial imagery to determine the amounts of clearcutting in the basins over time. I integrated this variable with channel morphometric variables to assess predictors of wood abundance and volume through multiple regression analysis. Results show that the stream that has been the most affected by clearcutting has lower volumes of wood than measured in 1979 or 1998. Residence times of wood are short in these watersheds and wood abundance and volume was highly impacted by the debris flows that occurred during the Storm of 1996, prior to the 1998 data collection. There are statistically significant changes that have occurred in the stream morphology among the four watersheds. This dissertation also tests a method of detecting fluvial wood through airborne lidar analysis. This method provides an alternative to field surveys in areas of even the most extreme tree canopy cover. Close

• 2. [Article] Eastside, Westside: Forestry students go into the woods for hands-on learning at field school

  Citation × Citation Citation Abstract Copy Title: Eastside, Westside: Forestry students go into the woods for hands-on learning at field school Author: Bernart, Bryan Title: Eastside, Westside: Forestry students go into the woods for hands-on learning at field school Author: Bernart, Bryan Close

• 3. [Article] Uncertainty in forest road hydrologic modeling and catchment scale assessment of forest road sediment yield

  The goal of this study was to advance methods for assessment of forest road hydrologic response and sediment yield at a catchment scale. This research looked at the effect of soil depth estimation on the ...

  Citation × Citation Citation Abstract Copy Title: Uncertainty in forest road hydrologic modeling and catchment scale assessment of forest road sediment yield Author: Surfleet, Christopher G. The goal of this study was to advance methods for assessment of forest road hydrologic response and sediment yield at a catchment scale. This research looked at the effect of soil depth estimation on the Distributive Hydrology Soil Vegetation Model (DHSVM), assessed the uncertainty and accuracy of hydrologic modeling of forest roads by DHSVM, and evaluated the use of road runoff and sediment sampling for catchment scale road sediment estimates. The influence of soil depth estimation on DHSVM varied by spatial scale and hydrologic process modeled. Soil depth measurement improved DHSVM simulated streamflow and road ditchflow for the rising limb of the hydrograph with no improvements during baseflow. For site specific or small scale modeling a deterministic soil depth model fit to field measurements was best. For larger scale simulations of streamflow mean soil depth provided as good or better estimates. Considerable uncertainty in estimates of road hydrologic response was observed from DHSVM. DHSVM over predicted individual road discharges. As the spatial scale and temporal scale was increased the uncertainty in DHSVM results decreased. This suggests that model structures chosen for DHSVM would be better determined with internal catchment data, at smaller scales. The GLUE assessment showed that change detection analysis with DHSVM will be limited to sites or scales of the catchment that behavioral model structures can be identified. From this research it was determined that only the catchment scale simulations and a few individual road locations could be used for change detection. The storm runoff volumes and peak flows from road ditchflow had linear relationships with storm sediment load. These relationships had to be developed by classes of road locations and types in an intensively managed forest due to variability in road design, hydrologic response, and road use. Sediment from roads estimated from field measurements used with SEDMODL2 or WARSEM provided substantially lower estimates than without field measured adjustments. The use of road runoff for sediment estimation provided even lower catchment scale sediment results. DHSVM simulated road runoff for sediment estimation provided catchment scale results similar to the sediment yield estimated from observed road runoff. Title: Uncertainty in forest road hydrologic modeling and catchment scale assessment of forest road sediment yield Author: Surfleet, Christopher G. The goal of this study was to advance methods for assessment of forest road hydrologic response and sediment yield at a catchment scale. This research looked at the effect of soil depth estimation on the Distributive Hydrology Soil Vegetation Model (DHSVM), assessed the uncertainty and accuracy of hydrologic modeling of forest roads by DHSVM, and evaluated the use of road runoff and sediment sampling for catchment scale road sediment estimates. The influence of soil depth estimation on DHSVM varied by spatial scale and hydrologic process modeled. Soil depth measurement improved DHSVM simulated streamflow and road ditchflow for the rising limb of the hydrograph with no improvements during baseflow. For site specific or small scale modeling a deterministic soil depth model fit to field measurements was best. For larger scale simulations of streamflow mean soil depth provided as good or better estimates. Considerable uncertainty in estimates of road hydrologic response was observed from DHSVM. DHSVM over predicted individual road discharges. As the spatial scale and temporal scale was increased the uncertainty in DHSVM results decreased. This suggests that model structures chosen for DHSVM would be better determined with internal catchment data, at smaller scales. The GLUE assessment showed that change detection analysis with DHSVM will be limited to sites or scales of the catchment that behavioral model structures can be identified. From this research it was determined that only the catchment scale simulations and a few individual road locations could be used for change detection. The storm runoff volumes and peak flows from road ditchflow had linear relationships with storm sediment load. These relationships had to be developed by classes of road locations and types in an intensively managed forest due to variability in road design, hydrologic response, and road use. Sediment from roads estimated from field measurements used with SEDMODL2 or WARSEM provided substantially lower estimates than without field measured adjustments. The use of road runoff for sediment estimation provided even lower catchment scale sediment results. DHSVM simulated road runoff for sediment estimation provided catchment scale results similar to the sediment yield estimated from observed road runoff. Close

• 4. [Article] Hydrology and geomorphic evolution of basaltic landscapes, High Cascades, Oregon

  The basaltic landscapes of the Oregon High Cascades form a natural laboratory for examining how geologic setting and history influence groundwater flowpaths, streamflow sensitivity to climate, and landscape ...

  Citation × Citation Citation Abstract Copy Title: Hydrology and geomorphic evolution of basaltic landscapes, High Cascades, Oregon Author: Jefferson, Anne (Anne Jarvis) The basaltic landscapes of the Oregon High Cascades form a natural laboratory for examining how geologic setting and history influence groundwater flowpaths, streamflow sensitivity to climate, and landscape evolution. In the High Cascades, highly permeable young basaltic lavas form extensive aquifers. These aquifers are the dominant sources of summer streamflow for the Willamette River and its tributary, the McKenzie River, whose watershed forms the study area. Groundwater is discharged at large volume, cold springs, and discharge, temperature, and isotopic measurements at seven springs were used to constrain groundwater patterns. Lava flow geometries have a significant influence on groundwater recharge areas and flowpaths, sometimes superseding topographic controls. Transit times to springs are ~3-14 years, and flowpaths are generally shallow and have limited contact with deeper geothermal systems, except at fault zones. Time-series analyses of historical discharge, precipitation, snow, and temperature records reveal that the distribution of permeable rocks and resultant groundwater systems strongly influence streamflow response to climatic forcing. The annual hydrograph is shaped by groundwater storage and release, but inter-annual streamflow variability is largely the result of climatic forcing. Over the past 60 years, warmer winters and earlier snowmelt have lengthened the summer recession period and decreased autumn minimum discharges in a groundwater-dominated watershed. A chronosequence of dated rock units, combined with field observations and measurements of slopes, contributing areas, and drainage densities, shows that the geologic history of a watershed controls the stage of drainage development. Groundwater flowpaths remain the dominant drainage mechanism for up to one million years, but as chemical weathering, glaciation, and other processes reduce the land surface permeability, channel networks grow up-slope of the springs. Within three million years, water is carried via a fully developed runoff-dominated stream network, groundwater discharge is insubstantial, and the landscape is shaped by fluvial and mass-wasting processes. The geology of a landscape is important for understanding hydrological processes at time scales ranging from a single season to several million years. Title: Hydrology and geomorphic evolution of basaltic landscapes, High Cascades, Oregon Author: Jefferson, Anne (Anne Jarvis) The basaltic landscapes of the Oregon High Cascades form a natural laboratory for examining how geologic setting and history influence groundwater flowpaths, streamflow sensitivity to climate, and landscape evolution. In the High Cascades, highly permeable young basaltic lavas form extensive aquifers. These aquifers are the dominant sources of summer streamflow for the Willamette River and its tributary, the McKenzie River, whose watershed forms the study area. Groundwater is discharged at large volume, cold springs, and discharge, temperature, and isotopic measurements at seven springs were used to constrain groundwater patterns. Lava flow geometries have a significant influence on groundwater recharge areas and flowpaths, sometimes superseding topographic controls. Transit times to springs are ~3-14 years, and flowpaths are generally shallow and have limited contact with deeper geothermal systems, except at fault zones. Time-series analyses of historical discharge, precipitation, snow, and temperature records reveal that the distribution of permeable rocks and resultant groundwater systems strongly influence streamflow response to climatic forcing. The annual hydrograph is shaped by groundwater storage and release, but inter-annual streamflow variability is largely the result of climatic forcing. Over the past 60 years, warmer winters and earlier snowmelt have lengthened the summer recession period and decreased autumn minimum discharges in a groundwater-dominated watershed. A chronosequence of dated rock units, combined with field observations and measurements of slopes, contributing areas, and drainage densities, shows that the geologic history of a watershed controls the stage of drainage development. Groundwater flowpaths remain the dominant drainage mechanism for up to one million years, but as chemical weathering, glaciation, and other processes reduce the land surface permeability, channel networks grow up-slope of the springs. Within three million years, water is carried via a fully developed runoff-dominated stream network, groundwater discharge is insubstantial, and the landscape is shaped by fluvial and mass-wasting processes. The geology of a landscape is important for understanding hydrological processes at time scales ranging from a single season to several million years. Close

• 5. [Article] Measurement and modeling the physical controls of snowmelt in the Pacific Northwest

  The physical controls of snowmelt in the Pacific Northwest (PNW) are poorly understood. While there have been numerous field and modeling investigations at the plot and watershed scale, few studies have ...

  Citation × Citation Citation Abstract Copy Title: Measurement and modeling the physical controls of snowmelt in the Pacific Northwest Author: Mazurkiewicz, Adam B. The physical controls of snowmelt in the Pacific Northwest (PNW) are poorly understood. While there have been numerous field and modeling investigations at the plot and watershed scale, few studies have identified how the snow energy balance (EB) components vary in importance both spatially and temporally. The identification of how dominant EB components vary in space and time will allow us to understand how the snow regime will be affected by environmental change. We apply two physically based snow energy balance models (SNOBAL and ISNOBAL) to two different climate regimes of PNW Cascade Mountains to investigate the spatial and temporal variability of EB components which cause snowmelt. We found that radiation dominated the EB in both the rain-on-snow, Western Cascades environment and in a semi-arid watershed in the Eastern Cascades. Turbulent energy exchanges varied with topographic position, vegetation, and most importantly wind speed. In both modeling scenarios warmer winters led to shallower snowpack accumulation. Shorter snow seasons resulted in lower radiation inputs and higher sensible heat exchanges in the annual EB. Numerical simulation of snowmelt processes has helped to provide an understanding of the anticipated effects of environmental change on the snow regime in the PNW. Title: Measurement and modeling the physical controls of snowmelt in the Pacific Northwest Author: Mazurkiewicz, Adam B. The physical controls of snowmelt in the Pacific Northwest (PNW) are poorly understood. While there have been numerous field and modeling investigations at the plot and watershed scale, few studies have identified how the snow energy balance (EB) components vary in importance both spatially and temporally. The identification of how dominant EB components vary in space and time will allow us to understand how the snow regime will be affected by environmental change. We apply two physically based snow energy balance models (SNOBAL and ISNOBAL) to two different climate regimes of PNW Cascade Mountains to investigate the spatial and temporal variability of EB components which cause snowmelt. We found that radiation dominated the EB in both the rain-on-snow, Western Cascades environment and in a semi-arid watershed in the Eastern Cascades. Turbulent energy exchanges varied with topographic position, vegetation, and most importantly wind speed. In both modeling scenarios warmer winters led to shallower snowpack accumulation. Shorter snow seasons resulted in lower radiation inputs and higher sensible heat exchanges in the annual EB. Numerical simulation of snowmelt processes has helped to provide an understanding of the anticipated effects of environmental change on the snow regime in the PNW. Close

• 6. [Article] After the Flow: Landscape Response to the Emplacement of Holocene Lava Flows, Central Oregon Cascades, USA

  Effusive volcanic eruptions repave landscapes rapidly with lava flows, resetting the underlying landscape and ecosystem. The unique physical properties of lava pose interesting challenges for recovery, ...

  Citation × Citation Citation Abstract Copy Title: After the Flow: Landscape Response to the Emplacement of Holocene Lava Flows, Central Oregon Cascades, USA Author: Deligne, Natalia Year: 2012 Effusive volcanic eruptions repave landscapes rapidly with lava flows, resetting the underlying landscape and ecosystem. The unique physical properties of lava pose interesting challenges for recovery, as lava flows can be highly permeable while lava itself is dense, sterile, and generally inhospitable towards life. This dissertation examines two aspects of landscape recovery following lava flow emplacement: (1) hydrologic adaptation of surface and groundwater to recent volcanism and (2) plant colonization of young lava flows. I examine two sites in the central Oregon Cascades: the c. 3 ka Sand Mountain volcanic field (SMVF), located in the headwaters of the McKenzie River, a critical water resource for the state of Oregon, and the c. 1.5 ka Collier Cone lava flow, originating on the north flanks of North Sister volcano. My investigation of the SMVF and upper McKenzie River watershed reveals a complex volcanic history with profound impacts on the configuration and short-term discharge of the McKenzie River: lava flows from the SMVF and other Holocene vents have buried, dammed, and altered the path of the McKenzie River. Moreover, given the large groundwater contribution from the SMVF to the McKenzie River, I estimate that SMVF activity caused McKenzie River discharge in present-day Eugene, Oregon to decrease by up to 20% for days to months at a time; future regional mafic volcanic activity could have a similar impact. The SMVF and the Collier Cone lava flow are notable for the juxtaposition of barren exposed lava and mature forests on the same or similarly aged lava flows. I use a combination of LiDAR analysis, field observations, and soil characterization to examine soil and vegetation at these two sites and find that the presence of an external soil source greatly facilitates plant establishment, growth, and survival. Here, external soil sources are syn- or post-eruptive tephra (SMVF) or flood-borne deposits (Collier Cone lava flow). External soil appears to provide a substrate for plants to grow in along with key nutrients and sufficient moisture; overall, external soil sources are key for the initial recovery following an effusive volcanic disturbance. This dissertation includes co-authored material submitted for publication. Title: After the Flow: Landscape Response to the Emplacement of Holocene Lava Flows, Central Oregon Cascades, USA Author: Deligne, Natalia Year: 2012 Effusive volcanic eruptions repave landscapes rapidly with lava flows, resetting the underlying landscape and ecosystem. The unique physical properties of lava pose interesting challenges for recovery, as lava flows can be highly permeable while lava itself is dense, sterile, and generally inhospitable towards life. This dissertation examines two aspects of landscape recovery following lava flow emplacement: (1) hydrologic adaptation of surface and groundwater to recent volcanism and (2) plant colonization of young lava flows. I examine two sites in the central Oregon Cascades: the c. 3 ka Sand Mountain volcanic field (SMVF), located in the headwaters of the McKenzie River, a critical water resource for the state of Oregon, and the c. 1.5 ka Collier Cone lava flow, originating on the north flanks of North Sister volcano. My investigation of the SMVF and upper McKenzie River watershed reveals a complex volcanic history with profound impacts on the configuration and short-term discharge of the McKenzie River: lava flows from the SMVF and other Holocene vents have buried, dammed, and altered the path of the McKenzie River. Moreover, given the large groundwater contribution from the SMVF to the McKenzie River, I estimate that SMVF activity caused McKenzie River discharge in present-day Eugene, Oregon to decrease by up to 20% for days to months at a time; future regional mafic volcanic activity could have a similar impact. The SMVF and the Collier Cone lava flow are notable for the juxtaposition of barren exposed lava and mature forests on the same or similarly aged lava flows. I use a combination of LiDAR analysis, field observations, and soil characterization to examine soil and vegetation at these two sites and find that the presence of an external soil source greatly facilitates plant establishment, growth, and survival. Here, external soil sources are syn- or post-eruptive tephra (SMVF) or flood-borne deposits (Collier Cone lava flow). External soil appears to provide a substrate for plants to grow in along with key nutrients and sufficient moisture; overall, external soil sources are key for the initial recovery following an effusive volcanic disturbance. This dissertation includes co-authored material submitted for publication. Close