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• 1. [Article] Effects of Beaver Dams on Surface Water Flow During Storm Events in an Urban Landscape

  Urban land-use generally alters the hydrologic cycle, leading to changes in the natural flow regime of local streams. Runoff from impervious surfaces and routing of stormwater to streams causes urban streams ...

  Citation × Citation Citation Abstract Copy Title: Effects of Beaver Dams on Surface Water Flow During Storm Events in an Urban Landscape Author: Poor, Erin Year: 2017 Urban land-use generally alters the hydrologic cycle, leading to changes in the natural flow regime of local streams. Runoff from impervious surfaces and routing of stormwater to streams causes urban streams to respond quickly and more intensely to storm events-more so than then would be observed in a less urbanized landscape. The rapid pulse of water that is routed to streams during precipitation events can degrade the physical structure of the channel and alter water quality and habitat availability. To manage these common urban stream issues, agencies have been seeking alternative ways of restoring and enhancing resilience in urban stream networks within the constraints of existing infrastructure. One potential strategy may be to support beaver recolonization of urban streams. This is because beaver dam building activity has been found to attenuate streamflow in areas that have experienced minimal human impact. Currently, however, no studies have been published that examine how beaver dams affect stream flow in altered urban systems. This study seeks to determine if the presence of beaver dams and ponds in urban stream reaches in the Tualatin River basin, Oregon, modifies the stream’s response to storm events. Continuous surface water levels are being collected upstream and downstream of two beaver affected reaches in order to determine how the presence of dams and ponds affect the flow regime, and whether this more closely resembles a less degraded state. Title: Effects of Beaver Dams on Surface Water Flow During Storm Events in an Urban Landscape Author: Poor, Erin Year: 2017 Urban land-use generally alters the hydrologic cycle, leading to changes in the natural flow regime of local streams. Runoff from impervious surfaces and routing of stormwater to streams causes urban streams to respond quickly and more intensely to storm events-more so than then would be observed in a less urbanized landscape. The rapid pulse of water that is routed to streams during precipitation events can degrade the physical structure of the channel and alter water quality and habitat availability. To manage these common urban stream issues, agencies have been seeking alternative ways of restoring and enhancing resilience in urban stream networks within the constraints of existing infrastructure. One potential strategy may be to support beaver recolonization of urban streams. This is because beaver dam building activity has been found to attenuate streamflow in areas that have experienced minimal human impact. Currently, however, no studies have been published that examine how beaver dams affect stream flow in altered urban systems. This study seeks to determine if the presence of beaver dams and ponds in urban stream reaches in the Tualatin River basin, Oregon, modifies the stream’s response to storm events. Continuous surface water levels are being collected upstream and downstream of two beaver affected reaches in order to determine how the presence of dams and ponds affect the flow regime, and whether this more closely resembles a less degraded state. Close

• 2. [Article] A Statistical Investigation of Lower Columbia River Water Temperature, 1915-2003

  The Columbia River is home to anadromous salmon populations that migrate upriver every year to spawn. These fish require cool water temperatures (Tw) to survive. In recent years, high summer Tw in the ...

  Citation × Citation Citation Abstract Copy Title: A Statistical Investigation of Lower Columbia River Water Temperature, 1915-2003 Author: Overman, Corina Christina Mae Year: 2017 The Columbia River is home to anadromous salmon populations that migrate upriver every year to spawn. These fish require cool water temperatures (Tw) to survive. In recent years, high summer Tw in the Columbia River has caused increased mortality of salmon. Different possible explanations for increased Tw include climate change, deforestation, and decreased summertime streamflow (Q) due to dams. In this study, robust linear regression models of Tw based on air temperature (Ta) and Q were developed to examine the change in Tw over time. The data was separated into an historical period (1938-1956) and a modern period (1977-2003). Seasonal regression models were used for May through October (summer) and November through April (winter) for each period. Comparison of these models showed that Tw has become less sensitive to recent atmospheric heating and cooling. By contrast, analysis suggested that Tw has become more sensitive to variations in Q. Of the 1.5ºC increase in maximum summertime Tw, approximately 1.3ºC was due to dams and reservoir management based on changes in regression coefficients and average Q. A smaller, 0.2ºC change was estimated to be caused by increasing Ta since the mid-20th century. While average maximum Tw has increased, both the statistical model and data suggest that the variability in Tw from its climatological average has decreased, probably due to reservoir management. Title: A Statistical Investigation of Lower Columbia River Water Temperature, 1915-2003 Author: Overman, Corina Christina Mae Year: 2017 The Columbia River is home to anadromous salmon populations that migrate upriver every year to spawn. These fish require cool water temperatures (Tw) to survive. In recent years, high summer Tw in the Columbia River has caused increased mortality of salmon. Different possible explanations for increased Tw include climate change, deforestation, and decreased summertime streamflow (Q) due to dams. In this study, robust linear regression models of Tw based on air temperature (Ta) and Q were developed to examine the change in Tw over time. The data was separated into an historical period (1938-1956) and a modern period (1977-2003). Seasonal regression models were used for May through October (summer) and November through April (winter) for each period. Comparison of these models showed that Tw has become less sensitive to recent atmospheric heating and cooling. By contrast, analysis suggested that Tw has become more sensitive to variations in Q. Of the 1.5ºC increase in maximum summertime Tw, approximately 1.3ºC was due to dams and reservoir management based on changes in regression coefficients and average Q. A smaller, 0.2ºC change was estimated to be caused by increasing Ta since the mid-20th century. While average maximum Tw has increased, both the statistical model and data suggest that the variability in Tw from its climatological average has decreased, probably due to reservoir management. Close

• 3. [Article] Historical and Existing Vascular and Bryophyte Flora, Former Blue Heron Paper Mill, Willamette Falls, Oregon City, Oregon

  Willamette Falls has long been a focus of botanical interest, but industrial development at the site has limited public access for over a century. The closure of the Blue Heron paper mill on the south ...

  Citation × Citation Citation Abstract Copy Title: Historical and Existing Vascular and Bryophyte Flora, Former Blue Heron Paper Mill, Willamette Falls, Oregon City, Oregon Author: Christy, John A., Gaddis, Philip Year: 2015 Willamette Falls has long been a focus of botanical interest, but industrial development at the site has limited public access for over a century. The closure of the Blue Heron paper mill on the south bank of the river, and proposed redevelopment of the site, has given planners an opportunity to revisit this part of the falls and identify its current flora. As part of the preconstruction planning process for public access to the falls, Metro contracted John Christy to document the historical and existing vascular flora on the site, and Philip Gaddis joined us to document the bryophyte flora. For millennia, the falls has been a magnet for fishing, settlement, and more recent industrial development. Photographs by Carleton Watkins show that the south bank of the river at Willamette Falls had been modified for industrial uses as early as 1867. Infrastructure included dams and spillways to create a boat basin, and millraces to power a sawmill, gristmill, and woolen mill. Later, paper mills and electrical generating stations were built on both sides of the falls. These activities concentrated at the falls have impacted all native habitat except vertical cliff faces on basalt outcrops along the river. Significant portions of the shoreline at the Blue Heron site have been modified by fill. Remaining habitat in natural or semi-natural condition includes areas hydrated by tidal action of the Willamette River, areas of seasonal or perennial seepage below spillways and the old grinders, and basalt outcrops with varying exposures. The basalt outcrops are a relic of the Bretz or Missoula Floods (Allen et al. 1986), and exposures along this part of the Willamette River provide outlier habitat for both mesic and xeric species more common in the Columbia River Gorge (Detling 1958). Willamette Falls has a similar history to that of Niagara Falls in terms of industrial development, presence of a rock substrate supporting disjunct populations of rare plants, and botanical exploration that occurred primarily between 1885 and 1915 (Eckel 2013). Title: Historical and Existing Vascular and Bryophyte Flora, Former Blue Heron Paper Mill, Willamette Falls, Oregon City, Oregon Author: Christy, John A., Gaddis, Philip Year: 2015 Willamette Falls has long been a focus of botanical interest, but industrial development at the site has limited public access for over a century. The closure of the Blue Heron paper mill on the south bank of the river, and proposed redevelopment of the site, has given planners an opportunity to revisit this part of the falls and identify its current flora. As part of the preconstruction planning process for public access to the falls, Metro contracted John Christy to document the historical and existing vascular flora on the site, and Philip Gaddis joined us to document the bryophyte flora. For millennia, the falls has been a magnet for fishing, settlement, and more recent industrial development. Photographs by Carleton Watkins show that the south bank of the river at Willamette Falls had been modified for industrial uses as early as 1867. Infrastructure included dams and spillways to create a boat basin, and millraces to power a sawmill, gristmill, and woolen mill. Later, paper mills and electrical generating stations were built on both sides of the falls. These activities concentrated at the falls have impacted all native habitat except vertical cliff faces on basalt outcrops along the river. Significant portions of the shoreline at the Blue Heron site have been modified by fill. Remaining habitat in natural or semi-natural condition includes areas hydrated by tidal action of the Willamette River, areas of seasonal or perennial seepage below spillways and the old grinders, and basalt outcrops with varying exposures. The basalt outcrops are a relic of the Bretz or Missoula Floods (Allen et al. 1986), and exposures along this part of the Willamette River provide outlier habitat for both mesic and xeric species more common in the Columbia River Gorge (Detling 1958). Willamette Falls has a similar history to that of Niagara Falls in terms of industrial development, presence of a rock substrate supporting disjunct populations of rare plants, and botanical exploration that occurred primarily between 1885 and 1915 (Eckel 2013). Close