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• 1. [Article] Coastal hazards and community exposure in a changing climate : the development of probabilistic coastal change hazard zones

  Documented trends in rising sea levels, storminess, and extreme wave heights have the potential to increase the frequency and magnitude of coastal change hazards, increasing risks to coastal infrastructure ...

  Citation × Citation Citation Abstract Copy Title: Coastal hazards and community exposure in a changing climate : the development of probabilistic coastal change hazard zones Author: Baron, Heather M. Documented trends in rising sea levels, storminess, and extreme wave heights have the potential to increase the frequency and magnitude of coastal change hazards, increasing risks to coastal infrastructure and environmental resources. Coastal planners and decision makers need information about the impacts of future hazards in order to apply mitigation and adaptation strategies. However, making quantitative predictions of beach and dune erosion is complicated by uncertainties surrounding the drivers and impacts of climate change as well as our understanding of climate controls on coastal change hazards. Furthermore, these changes are occurring in a dynamic environment where beach geomorphology evolves over a variety of spatial and temporal scales. Here a new, probabilistic approach for quantifying future coastal change hazards that incorporates the uncertainty associated with both climate change and morphological variability is presented. First, a suite of synthetic time series of total water levels (TWLs) through 2100 are produced by applying various climate change scenarios, composed of projections of sea-level rise, wave climate, and the frequency of major El Niños, to historical datasets of waves and measured tidal elevations. These time series allow extreme design events to be computed for any time period in the future (e.g., 100-year TWL event in 2030). Using simple coastal change models that require TWLs and various beach morphometrics as input, future coastal change is quantified over a wide range of possible climate futures for sandy, dune-backed coastlines. The new methodology has been applied to the Tillamook County coast in northwestern Oregon to develop coastal change hazard zones of arbitrary confidence levels for both the 100% and 1% annual chance TWL events at present (2009) and for years 2030, 2050, and 2100. The nature of the probabilistic approach, however, allows for coastal decision makers to determine the desired level of confidence (or exceedance probability), extremity of the event, and planning horizon to consider. The hazard zones are then integrated with various socioeconomic datasets (e.g., structures, roads) to evaluate the exposure of coastal communities to the predicted coastal change hazards at various levels of confidence. When paired with community vulnerability assessments, the hazard map products developed will provide coastal planners with the tools and information to allow for science-based decisions that will increase the adaptive capacity of coastal communities as they prepare for the uncertainties of future climate change. Title: Coastal hazards and community exposure in a changing climate : the development of probabilistic coastal change hazard zones Author: Baron, Heather M. Documented trends in rising sea levels, storminess, and extreme wave heights have the potential to increase the frequency and magnitude of coastal change hazards, increasing risks to coastal infrastructure and environmental resources. Coastal planners and decision makers need information about the impacts of future hazards in order to apply mitigation and adaptation strategies. However, making quantitative predictions of beach and dune erosion is complicated by uncertainties surrounding the drivers and impacts of climate change as well as our understanding of climate controls on coastal change hazards. Furthermore, these changes are occurring in a dynamic environment where beach geomorphology evolves over a variety of spatial and temporal scales. Here a new, probabilistic approach for quantifying future coastal change hazards that incorporates the uncertainty associated with both climate change and morphological variability is presented. First, a suite of synthetic time series of total water levels (TWLs) through 2100 are produced by applying various climate change scenarios, composed of projections of sea-level rise, wave climate, and the frequency of major El Niños, to historical datasets of waves and measured tidal elevations. These time series allow extreme design events to be computed for any time period in the future (e.g., 100-year TWL event in 2030). Using simple coastal change models that require TWLs and various beach morphometrics as input, future coastal change is quantified over a wide range of possible climate futures for sandy, dune-backed coastlines. The new methodology has been applied to the Tillamook County coast in northwestern Oregon to develop coastal change hazard zones of arbitrary confidence levels for both the 100% and 1% annual chance TWL events at present (2009) and for years 2030, 2050, and 2100. The nature of the probabilistic approach, however, allows for coastal decision makers to determine the desired level of confidence (or exceedance probability), extremity of the event, and planning horizon to consider. The hazard zones are then integrated with various socioeconomic datasets (e.g., structures, roads) to evaluate the exposure of coastal communities to the predicted coastal change hazards at various levels of confidence. When paired with community vulnerability assessments, the hazard map products developed will provide coastal planners with the tools and information to allow for science-based decisions that will increase the adaptive capacity of coastal communities as they prepare for the uncertainties of future climate change. Close

• 2. [Article] Climate change impacts on mountain snowpack presented in a knowledge to action framework

  Throughout many of the world’s mountain ranges snowpack accumulates during the winter and into the spring, providing a natural reservoir for water. As this reservoir melts, it fills streams and recharges ...

  Citation × Citation Citation Abstract Copy Title: Climate change impacts on mountain snowpack presented in a knowledge to action framework Author: Sproles, Eric Allan Throughout many of the world’s mountain ranges snowpack accumulates during the winter and into the spring, providing a natural reservoir for water. As this reservoir melts, it fills streams and recharges groundwater for over 1 billion people globally. Despite its importance to water resources, our understanding of the storage capacity of mountain snowpack is incomplete. This partial knowledge limits our abilities to assess the impact that projected climate conditions will have on mountain snowpack and water resources. While understanding the effect of projected climate on mountain snowpack is a global question, it can be best understood at the basin scale. It is at this level that decision makers and water resource managers base their decisions and require a clarified understanding of basin's mountain snowpack. The McKenzie River Basin located in the central-western Cascades of Oregon exhibits characteristics typical of many mountain river systems globally and in the Pacific Northwestern United States. Here snowmelt provides critical water supply for hydropower, agriculture, ecosystems, recreation, and municipalities. While there is a surplus of water in winter, the summer months see flows reach a minimum and the same groups have to compete for a limited supply. Throughout the Pacific Northwestern United States, current analyses and those of projected future climate change impacts show rising temperatures, diminished snowpacks, and declining summertime streamflow. The impacts of climate change on water resources presents new challenges and requires fresh approaches to understanding problems that are only beginning to be recognized. Climate change also presents challenges to decision makers who need new kinds of climate and water information, and will need the scientific research community to help provide improved means of knowledge transfer. This dissertation quantified the basin-wide distribution of snowpack across multiple decades in present and in projected climate conditions, describing a 56% decrease in mountain snowpack with regional projected temperature increases. These results were used to develop a probabilistic understanding of snowpack in projected climates. This section described a significant shift in statistical relations of snowpack. One that would be statistically likely to accumulate every 3 out of 4 years would accumulate in 1 out of 20 years. Finally this research identifies methods to improved knowledge transfer from the research community to water resource professionals. Implementation of these recommendations would enable a more effective means of dissemination to stakeholders and policy makers. While this research focused only on the McKenzie River Basin, it has regional applications. Processes affecting snowpack in the McKenzie River Basin are similar to those in many other maritime, forested Pacific Northwest watersheds. The framework of this research could also be applied to regions outside of the Pacific Northwestern United States to gain a similar level of understanding of climate impacts on mountain snowpack. Title: Climate change impacts on mountain snowpack presented in a knowledge to action framework Author: Sproles, Eric Allan Throughout many of the world’s mountain ranges snowpack accumulates during the winter and into the spring, providing a natural reservoir for water. As this reservoir melts, it fills streams and recharges groundwater for over 1 billion people globally. Despite its importance to water resources, our understanding of the storage capacity of mountain snowpack is incomplete. This partial knowledge limits our abilities to assess the impact that projected climate conditions will have on mountain snowpack and water resources. While understanding the effect of projected climate on mountain snowpack is a global question, it can be best understood at the basin scale. It is at this level that decision makers and water resource managers base their decisions and require a clarified understanding of basin's mountain snowpack. The McKenzie River Basin located in the central-western Cascades of Oregon exhibits characteristics typical of many mountain river systems globally and in the Pacific Northwestern United States. Here snowmelt provides critical water supply for hydropower, agriculture, ecosystems, recreation, and municipalities. While there is a surplus of water in winter, the summer months see flows reach a minimum and the same groups have to compete for a limited supply. Throughout the Pacific Northwestern United States, current analyses and those of projected future climate change impacts show rising temperatures, diminished snowpacks, and declining summertime streamflow. The impacts of climate change on water resources presents new challenges and requires fresh approaches to understanding problems that are only beginning to be recognized. Climate change also presents challenges to decision makers who need new kinds of climate and water information, and will need the scientific research community to help provide improved means of knowledge transfer. This dissertation quantified the basin-wide distribution of snowpack across multiple decades in present and in projected climate conditions, describing a 56% decrease in mountain snowpack with regional projected temperature increases. These results were used to develop a probabilistic understanding of snowpack in projected climates. This section described a significant shift in statistical relations of snowpack. One that would be statistically likely to accumulate every 3 out of 4 years would accumulate in 1 out of 20 years. Finally this research identifies methods to improved knowledge transfer from the research community to water resource professionals. Implementation of these recommendations would enable a more effective means of dissemination to stakeholders and policy makers. While this research focused only on the McKenzie River Basin, it has regional applications. Processes affecting snowpack in the McKenzie River Basin are similar to those in many other maritime, forested Pacific Northwest watersheds. The framework of this research could also be applied to regions outside of the Pacific Northwestern United States to gain a similar level of understanding of climate impacts on mountain snowpack. Close

• 3. [Article] Debris flows in glaciated catchments : a case study on Mount Rainier, Washington

  Debris flows, which occur in mountain settings worldwide, have been particularly damaging in the glaciated basins flanking the stratovolcanoes in the Cascade Range of the northwestern United States. This ...

  Citation × Citation Citation Abstract Copy Title: Debris flows in glaciated catchments : a case study on Mount Rainier, Washington Author: Legg, Nicholas T. Debris flows, which occur in mountain settings worldwide, have been particularly damaging in the glaciated basins flanking the stratovolcanoes in the Cascade Range of the northwestern United States. This thesis contains two manuscripts that respectively investigate the (1) initiation processes of debris flows in these glaciated catchments, and (2) debris flow occurrence and its effect on valley bottoms over the last thousand years. In a 2006 storm, seven debris flows initiated from proglacial gullies of separate basins on the flanks of Mount Rainier. Gully heads at glacier termini and distributed collapse of gully walls imply that clear water was transformed to debris flow through progressive addition of sediment along gully lengths. In the first study, we analyze gully changes, reconstruct runoff conditions, and assess spatial distributions of debris flows to infer the processes and conditions necessary for debris flow initiation in glaciated catchments. Gully measurements suggest that sediment bulking requires steep gradients, abundant unstable material, and sufficient gully length. Reconstruction of runoff generated during the storm suggests that glaciers are important for generating the runoff necessary for debris flow initiation, particularly because infiltration capacities on glacial till covered surfaces well exceed measured rainfall rates. Runoff generation from glaciers and abundant loose debris at their termini explain why all debris flows in the storm initiated from proglacial areas. Proglacial areas that produced debris flows have steeper drainage networks with significantly higher elevations and lower drainage areas, suggesting that debris flows are associated with high elevation glaciers with relatively steep proglacial areas. This correlation reflects positive slope-elevation trends for the Mount Rainier volcano. An indirect effect of glacier change is thus the change in the distribution of ice-free slopes, which influence a basin’s debris flow potential. These findings have implications for projections of debris flow activity in basins experiencing glacier change. The second study uses a variety of dating techniques to reconstruct a chronology of debris flows in the Kautz Creek valley on the southwest flank of Mount Rainier (Washington). Dendrochronologic dating of growth disturbances combined with lichenometric techniques constrained five debris flow ages from 1712 to 1915 AD. We also estimated ages of three debris flows ranging in age from ca. 970 to 1661. Run-out distances served as a proxy for debris flow magnitude, and indicate that at least 11, 2, and 1 debris flow(s) have traveled at least 1, 3, and 5 km from the valley head, respectively since ca. 1650. Valley form reflects the frequency-magnitude relationship indicated by the chronology. In the upper, relatively steep valley, discrete debris flow snouts and secondary channels are abundant, suggesting a process of debris flow conveyance, channel plugging, and channel avulsion. The lower valley is characterized by relatively smooth surfaces, an absence of bouldery debris flow snouts, few secondary channels, and relatively old surface ages inferred from the presence of tephra layers. We infer that the lower valley is deposited on by relatively infrequent, large magnitude, low-yield strength debris flows like an event in 1947, which deposited wide, tabular lobes of debris outside of the main channel. Debris flows during the Little Ice Age (LIA) predominantly traveled no further than the upper valley. Stratigraphic evidence suggests that the main Kautz Creek channel was filled during the LIA, enhancing debris flow deposition on the valley surface and perhaps reducing run-out lengths. Diminished areas and gradients in front of glaciers during the LIA also likely contributed to decreased run-out lengths. These findings suggest that changes in debris flow source and depositional zones resulting from temperature and glacier cycles influence the magnitude and run-out distances of debris flows, and the dynamics of deposition in valley bottoms. Title: Debris flows in glaciated catchments : a case study on Mount Rainier, Washington Author: Legg, Nicholas T. Debris flows, which occur in mountain settings worldwide, have been particularly damaging in the glaciated basins flanking the stratovolcanoes in the Cascade Range of the northwestern United States. This thesis contains two manuscripts that respectively investigate the (1) initiation processes of debris flows in these glaciated catchments, and (2) debris flow occurrence and its effect on valley bottoms over the last thousand years. In a 2006 storm, seven debris flows initiated from proglacial gullies of separate basins on the flanks of Mount Rainier. Gully heads at glacier termini and distributed collapse of gully walls imply that clear water was transformed to debris flow through progressive addition of sediment along gully lengths. In the first study, we analyze gully changes, reconstruct runoff conditions, and assess spatial distributions of debris flows to infer the processes and conditions necessary for debris flow initiation in glaciated catchments. Gully measurements suggest that sediment bulking requires steep gradients, abundant unstable material, and sufficient gully length. Reconstruction of runoff generated during the storm suggests that glaciers are important for generating the runoff necessary for debris flow initiation, particularly because infiltration capacities on glacial till covered surfaces well exceed measured rainfall rates. Runoff generation from glaciers and abundant loose debris at their termini explain why all debris flows in the storm initiated from proglacial areas. Proglacial areas that produced debris flows have steeper drainage networks with significantly higher elevations and lower drainage areas, suggesting that debris flows are associated with high elevation glaciers with relatively steep proglacial areas. This correlation reflects positive slope-elevation trends for the Mount Rainier volcano. An indirect effect of glacier change is thus the change in the distribution of ice-free slopes, which influence a basin’s debris flow potential. These findings have implications for projections of debris flow activity in basins experiencing glacier change. The second study uses a variety of dating techniques to reconstruct a chronology of debris flows in the Kautz Creek valley on the southwest flank of Mount Rainier (Washington). Dendrochronologic dating of growth disturbances combined with lichenometric techniques constrained five debris flow ages from 1712 to 1915 AD. We also estimated ages of three debris flows ranging in age from ca. 970 to 1661. Run-out distances served as a proxy for debris flow magnitude, and indicate that at least 11, 2, and 1 debris flow(s) have traveled at least 1, 3, and 5 km from the valley head, respectively since ca. 1650. Valley form reflects the frequency-magnitude relationship indicated by the chronology. In the upper, relatively steep valley, discrete debris flow snouts and secondary channels are abundant, suggesting a process of debris flow conveyance, channel plugging, and channel avulsion. The lower valley is characterized by relatively smooth surfaces, an absence of bouldery debris flow snouts, few secondary channels, and relatively old surface ages inferred from the presence of tephra layers. We infer that the lower valley is deposited on by relatively infrequent, large magnitude, low-yield strength debris flows like an event in 1947, which deposited wide, tabular lobes of debris outside of the main channel. Debris flows during the Little Ice Age (LIA) predominantly traveled no further than the upper valley. Stratigraphic evidence suggests that the main Kautz Creek channel was filled during the LIA, enhancing debris flow deposition on the valley surface and perhaps reducing run-out lengths. Diminished areas and gradients in front of glaciers during the LIA also likely contributed to decreased run-out lengths. These findings suggest that changes in debris flow source and depositional zones resulting from temperature and glacier cycles influence the magnitude and run-out distances of debris flows, and the dynamics of deposition in valley bottoms. Close