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• 1. [Article] Toward a Spatial-Temporal Measure of Land-Use Mix

  Urban planning and public-health research has long been interested in the connection between land-use mix and travel. Interest from urban planners stems from the potential of transportation efficiency ...

  Citation × Citation Citation Abstract Copy Title: Toward a Spatial-Temporal Measure of Land-Use Mix Author: Gehrke, Steven R., Clifton, Kelly Year: 2015 Urban planning and public-health research has long been interested in the connection between land-use mix and travel. Interest from urban planners stems from the potential of transportation efficiency gains achieved by an increased land-use mix and subsequent shortening of trip lengths; whereas, public-health research advocates an increased land-use mix as an effective policy for facilitating greater physical activity. Yet, despite the transportation, land-use, and health benefits related to improving land-use mix and the extent of topical attention given by researchers, no consensus has been reached regarding the magnitude of its effect on travel. This absence of agreement may largely be attributed to the theoretical and methodological failings persistent in present attempts to accurately reflect land-use interaction and operationalize its quantification within a defined spatial extent. To better evaluate the impact of land-use mix on travel behavior and assess more temporal policies, a robust mix measure accounting for these two elements of land-use interaction and geographic scale as well as a temporal element of land-use mixing—missing from present specifications—must be introduced. This paper establishes the research agenda for a spatial-temporal land-use mix measure by (1) identifying the conceptual and methodological faults inherent to current land-use interaction and geographic-scale representations and (2) describing strategies and practical benefits of representing the temporal availability of land-use mixing in guiding innovative transportation/land-use policies. Title: Toward a Spatial-Temporal Measure of Land-Use Mix Author: Gehrke, Steven R., Clifton, Kelly Year: 2015 Urban planning and public-health research has long been interested in the connection between land-use mix and travel. Interest from urban planners stems from the potential of transportation efficiency gains achieved by an increased land-use mix and subsequent shortening of trip lengths; whereas, public-health research advocates an increased land-use mix as an effective policy for facilitating greater physical activity. Yet, despite the transportation, land-use, and health benefits related to improving land-use mix and the extent of topical attention given by researchers, no consensus has been reached regarding the magnitude of its effect on travel. This absence of agreement may largely be attributed to the theoretical and methodological failings persistent in present attempts to accurately reflect land-use interaction and operationalize its quantification within a defined spatial extent. To better evaluate the impact of land-use mix on travel behavior and assess more temporal policies, a robust mix measure accounting for these two elements of land-use interaction and geographic scale as well as a temporal element of land-use mixing—missing from present specifications—must be introduced. This paper establishes the research agenda for a spatial-temporal land-use mix measure by (1) identifying the conceptual and methodological faults inherent to current land-use interaction and geographic-scale representations and (2) describing strategies and practical benefits of representing the temporal availability of land-use mixing in guiding innovative transportation/land-use policies. Close

• 2. [Article] Laboratory Performance of Highway Bridge Girder Anchorages Under Simulated Hurricane-Induced Wave Loading

  Many bridges along the Gulf Coast of the United States were damaged by recent hurricanes, and many more are susceptible to similar damage. This research examines the structural performance of common connection ...

  Citation × Citation Citation Abstract Copy Title: Laboratory Performance of Highway Bridge Girder Anchorages Under Simulated Hurricane-Induced Wave Loading Author: Lehrman, Jora, Higgins, Christopher, Cox, Daniel Year: 2012 Many bridges along the Gulf Coast of the United States were damaged by recent hurricanes, and many more are susceptible to similar damage. This research examines the structural performance of common connection details used to anchor prestressed concrete girders to the substructure. Full-scale specimens were fabricated and tested under static and dynamic cyclic load histories. Dynamic load histories were developed from previously conducted hydraulic tests of a 1/5 scale model of a highway bridge under hurricane wave loads. The load effects considered included the pseudo-statically applied vertical uplift force, horizontal force, combined horizontal and vertical forces, and dynamically applied combined horizontal and vertical forces. This research describes the structural performance of the details under these loading conditions, provides improved understanding of connection performance, and enables better design details for new bridge construction and for rehabilitation of existing bridges to resist hurricane loads to produce surface transportation infrastructure that is more resilient to natural hazards. Title: Laboratory Performance of Highway Bridge Girder Anchorages Under Simulated Hurricane-Induced Wave Loading Author: Lehrman, Jora, Higgins, Christopher, Cox, Daniel Year: 2012 Many bridges along the Gulf Coast of the United States were damaged by recent hurricanes, and many more are susceptible to similar damage. This research examines the structural performance of common connection details used to anchor prestressed concrete girders to the substructure. Full-scale specimens were fabricated and tested under static and dynamic cyclic load histories. Dynamic load histories were developed from previously conducted hydraulic tests of a 1/5 scale model of a highway bridge under hurricane wave loads. The load effects considered included the pseudo-statically applied vertical uplift force, horizontal force, combined horizontal and vertical forces, and dynamically applied combined horizontal and vertical forces. This research describes the structural performance of the details under these loading conditions, provides improved understanding of connection performance, and enables better design details for new bridge construction and for rehabilitation of existing bridges to resist hurricane loads to produce surface transportation infrastructure that is more resilient to natural hazards. Close

• 3. [Article] Do Characteristics of Walkable Environments Support Bicycling? Toward a Definition of Bicycle-Supported Development

  Does walkability equate with bikeability? Through a comprehensive review of studies of the built environment and bicycling, including mode choice, route choice, safety, and urban design literature, this ...

  Citation × Citation Citation Abstract Copy Title: Do Characteristics of Walkable Environments Support Bicycling? Toward a Definition of Bicycle-Supported Development Author: Muhs, Christopher D., Clifton, Kelly Year: 2016 Does walkability equate with bikeability? Through a comprehensive review of studies of the built environment and bicycling, including mode choice, route choice, safety, and urban design literature, this paper addresses this question. Previous work has raised the issue that the two modes are functionally different, despite them often being combined into a nonmotorized category, and has highlighted research challenges. Existing studies of bikeability have largely focused on infrastructure. This paper contributes to the literature on bicycling and the built environment by providing a thorough review of past research with a focus on the relationships between land use, urban form, and bicycling. Highly walkable and highly bikeable environments are quite different, and there is little consistency in the built-environment attributes associated with cycling across studies. We postulate that this inconsistency is due in part to a disconnect between theory and methods of measuring the environment for cycling along with data limitations, including sample sizes and our understanding being based mainly on cross-sectional data. Many research opportunities are present for land-use planning policies now that planning for cycling is a top priority for cities and regions across the world. Title: Do Characteristics of Walkable Environments Support Bicycling? Toward a Definition of Bicycle-Supported Development Author: Muhs, Christopher D., Clifton, Kelly Year: 2016 Does walkability equate with bikeability? Through a comprehensive review of studies of the built environment and bicycling, including mode choice, route choice, safety, and urban design literature, this paper addresses this question. Previous work has raised the issue that the two modes are functionally different, despite them often being combined into a nonmotorized category, and has highlighted research challenges. Existing studies of bikeability have largely focused on infrastructure. This paper contributes to the literature on bicycling and the built environment by providing a thorough review of past research with a focus on the relationships between land use, urban form, and bicycling. Highly walkable and highly bikeable environments are quite different, and there is little consistency in the built-environment attributes associated with cycling across studies. We postulate that this inconsistency is due in part to a disconnect between theory and methods of measuring the environment for cycling along with data limitations, including sample sizes and our understanding being based mainly on cross-sectional data. Many research opportunities are present for land-use planning policies now that planning for cycling is a top priority for cities and regions across the world. Close

• 4. [Article] Development of a Pedestrian Demand Estimation Tool

  Most research on walking behavior has focused on mode choice or walk-trip frequency. In contrast, this study is one of the first to analyze the destination choice behaviors of pedestrians. Using about ...

  Citation × Citation Citation Abstract Copy Title: Development of a Pedestrian Demand Estimation Tool Author: Clifton, Kelly, Singleton, Patrick Allen, Muhs, Christopher D., Schneider, Robert J. Year: 2015 Most research on walking behavior has focused on mode choice or walk-trip frequency. In contrast, this study is one of the first to analyze the destination choice behaviors of pedestrians. Using about 4,500 walk trips from a 2011 household travel survey in the Portland, OR, region, we estimated multinomial logit pedestrian destination choice models for six trip purposes. Independent variables included terms for impedance (walk-trip distance); size (employment by type, households); supportive pedestrian environments (parks, a pedestrian index of the environment variable called PIE); barriers to walking (terrain, industrial-type employment); and traveler characteristics. Unique to this study was the use of small-scale destination zone alternatives. Distance was a significant deterrent to pedestrian destination choice, and people in carless or childless households were less sensitive to distance for some purposes. Employment (especially retail) was a strong attractor: doubling the number of jobs nearly doubled the odds of choosing a destination for home-based shopping walk trips. More attractive pedestrian environments were also positively associated with pedestrian destination choice after controlling for other factors. These results shed light on determinants of pedestrian destination choice behavior, and sensitivities in the models highlight potential policy-levers to increase walking activity. In addition, the destination choice models can be used in regional travel demand models or as pedestrian planning tools to evaluate land use and transportation policy and investment scenarios. Title: Development of a Pedestrian Demand Estimation Tool Author: Clifton, Kelly, Singleton, Patrick Allen, Muhs, Christopher D., Schneider, Robert J. Year: 2015 Most research on walking behavior has focused on mode choice or walk-trip frequency. In contrast, this study is one of the first to analyze the destination choice behaviors of pedestrians. Using about 4,500 walk trips from a 2011 household travel survey in the Portland, OR, region, we estimated multinomial logit pedestrian destination choice models for six trip purposes. Independent variables included terms for impedance (walk-trip distance); size (employment by type, households); supportive pedestrian environments (parks, a pedestrian index of the environment variable called PIE); barriers to walking (terrain, industrial-type employment); and traveler characteristics. Unique to this study was the use of small-scale destination zone alternatives. Distance was a significant deterrent to pedestrian destination choice, and people in carless or childless households were less sensitive to distance for some purposes. Employment (especially retail) was a strong attractor: doubling the number of jobs nearly doubled the odds of choosing a destination for home-based shopping walk trips. More attractive pedestrian environments were also positively associated with pedestrian destination choice after controlling for other factors. These results shed light on determinants of pedestrian destination choice behavior, and sensitivities in the models highlight potential policy-levers to increase walking activity. In addition, the destination choice models can be used in regional travel demand models or as pedestrian planning tools to evaluate land use and transportation policy and investment scenarios. Close

• 5. [Article] Adjusting ITE’s Trip Generation Handbook for Urban Context

  This study examines the ways in which urban context affects vehicle trip generation rates across three land uses. An intercept travel survey was administered at 78 establishments (high-turnover restaurants, ...

  Citation × Citation Citation Abstract Copy Title: Adjusting ITE’s Trip Generation Handbook for Urban Context Author: Clifton, Kelly J., Currans, Kristina Marie, Muhs, Christopher D. Year: 2015 This study examines the ways in which urban context affects vehicle trip generation rates across three land uses. An intercept travel survey was administered at 78 establishments (high-turnover restaurants, convenience markets, and drinking places) in the Portland, Oregon, region during 2011. This approach was developed to adjust the Institute of Transportation Engineers (ITE) Trip Generation Handbook vehicle trip rates based on built environment characteristics where the establishments were located. A number of policy-relevant built environment measures were used to estimate a set of nine models predicting an adjustment to ITE trip rates. Each model was estimated as a single measure: activity density, number of transit corridors, number of high-frequency bus lines, employment density, lot coverage, length of bicycle facilities, presence of rail transit, retail and service employment index, and intersection density. All of these models perform similarly (Adj. R2 0.76-0.77) in estimating trip rate adjustments. Data from 34 additional sites were collected to verify the adjustments. For convenience markets and drinking places, the adjustment models were an improvement to the ITE’s handbook method, while adjustments for restaurants tended to perform similarly to those from ITE’s estimation. The approach here is useful in guiding plans and policies for a short-term improvement to the ITE’s Trip Generation Handbook. The measures are useful for communities seeking to develop local adjustments to vehicle trip rate estimates, and all could be calculated from spatial data available in most locations. The paper concludes with a discussion on what long-term improvements to the ITE’s Trip Generation Handbook might entail, with further implications in planning and practice. Title: Adjusting ITE’s Trip Generation Handbook for Urban Context Author: Clifton, Kelly J., Currans, Kristina Marie, Muhs, Christopher D. Year: 2015 This study examines the ways in which urban context affects vehicle trip generation rates across three land uses. An intercept travel survey was administered at 78 establishments (high-turnover restaurants, convenience markets, and drinking places) in the Portland, Oregon, region during 2011. This approach was developed to adjust the Institute of Transportation Engineers (ITE) Trip Generation Handbook vehicle trip rates based on built environment characteristics where the establishments were located. A number of policy-relevant built environment measures were used to estimate a set of nine models predicting an adjustment to ITE trip rates. Each model was estimated as a single measure: activity density, number of transit corridors, number of high-frequency bus lines, employment density, lot coverage, length of bicycle facilities, presence of rail transit, retail and service employment index, and intersection density. All of these models perform similarly (Adj. R2 0.76-0.77) in estimating trip rate adjustments. Data from 34 additional sites were collected to verify the adjustments. For convenience markets and drinking places, the adjustment models were an improvement to the ITE’s handbook method, while adjustments for restaurants tended to perform similarly to those from ITE’s estimation. The approach here is useful in guiding plans and policies for a short-term improvement to the ITE’s Trip Generation Handbook. The measures are useful for communities seeking to develop local adjustments to vehicle trip rate estimates, and all could be calculated from spatial data available in most locations. The paper concludes with a discussion on what long-term improvements to the ITE’s Trip Generation Handbook might entail, with further implications in planning and practice. Close

• 6. [Article] Safety Effectiveness of Pedestrian Crossing Enhancements

  Over the last decade, the Oregon DOT and other agencies have systematically implemented many pedestrian crossing enhancements (PCEs) across the state. This study explored the safety performance of these ...

  Citation × Citation Citation Abstract Copy Title: Safety Effectiveness of Pedestrian Crossing Enhancements Author: Monsere, Christopher M., Figliozzi, Miguel, Kothuri, Sirisha, Razmpa, Ali, Hazel, Daniel R. Year: 2016 Over the last decade, the Oregon DOT and other agencies have systematically implemented many pedestrian crossing enhancements (PCEs) across the state. This study explored the safety performance of these enhanced crossing in Oregon. Detailed data were collected on 191 crossings. Supplemental data items included crossing location information, route characteristics, surrounding land use and crossing enhancement descriptions. Pedestrian volume at the crossing locations was a highly desirable but unavailable data element. To characterize pedestrian activity, a method was developed to estimate ranges for pedestrian crosswalk activity levels based on the land use classification at the census block level and the presence of pedestrian traffic generators such as bus stops, schools, shopping centers and hospitals within a 0.25-mile radius. Each crosswalk was categorized into one of six levels of activity – very low, low, medium-low, medium, medium-high and high. Crash data for the 2007-2014 period were assembled for the safety analysis. After filtering, 62 pedestrian crashes and 746 rear-end crashes were retained for further analysis. The crash data were merged and analyzed. Crash patterns and risk ratios were explored. The most important trend observed was a shift (reduction) in the pedestrian crash severity after the installation of the crosswalk treatments. This shift was from fatal and injury A crash type to lower severity crashes of injury B and injury C. For pedestrian crashes, increases in the risk ratio were observed for increases in the number of lanes, the posted speed, and estimated pedestrian activity level. Similar trends were observed for rear-end crashes. Due to data limitations, subsequent safety analysis focused on installations of RRFB crossing enhancements. A CMF for RRFB installations was estimated. The CMFS for pedestrian crashes are 0.64 +/- 0.26 using a simple before-after analysis; for rear-end crashes: 0.93 +/- 0.22 using an empirical Bayes analysis approach. Title: Safety Effectiveness of Pedestrian Crossing Enhancements Author: Monsere, Christopher M., Figliozzi, Miguel, Kothuri, Sirisha, Razmpa, Ali, Hazel, Daniel R. Year: 2016 Over the last decade, the Oregon DOT and other agencies have systematically implemented many pedestrian crossing enhancements (PCEs) across the state. This study explored the safety performance of these enhanced crossing in Oregon. Detailed data were collected on 191 crossings. Supplemental data items included crossing location information, route characteristics, surrounding land use and crossing enhancement descriptions. Pedestrian volume at the crossing locations was a highly desirable but unavailable data element. To characterize pedestrian activity, a method was developed to estimate ranges for pedestrian crosswalk activity levels based on the land use classification at the census block level and the presence of pedestrian traffic generators such as bus stops, schools, shopping centers and hospitals within a 0.25-mile radius. Each crosswalk was categorized into one of six levels of activity – very low, low, medium-low, medium, medium-high and high. Crash data for the 2007-2014 period were assembled for the safety analysis. After filtering, 62 pedestrian crashes and 746 rear-end crashes were retained for further analysis. The crash data were merged and analyzed. Crash patterns and risk ratios were explored. The most important trend observed was a shift (reduction) in the pedestrian crash severity after the installation of the crosswalk treatments. This shift was from fatal and injury A crash type to lower severity crashes of injury B and injury C. For pedestrian crashes, increases in the risk ratio were observed for increases in the number of lanes, the posted speed, and estimated pedestrian activity level. Similar trends were observed for rear-end crashes. Due to data limitations, subsequent safety analysis focused on installations of RRFB crossing enhancements. A CMF for RRFB installations was estimated. The CMFS for pedestrian crashes are 0.64 +/- 0.26 using a simple before-after analysis; for rear-end crashes: 0.93 +/- 0.22 using an empirical Bayes analysis approach. Close

• 7. [Article] Safety Effectiveness of Pedestrian Crossing Treatments

  Over the last decade, the transportation agencies in Oregon have systematically enhanced many pedestrian crossings at mid-block locations with Rectangular Rapid Flashing Beacons (RRFBs), Flashing Yellow ...

  Citation × Citation Citation Abstract Copy Title: Safety Effectiveness of Pedestrian Crossing Treatments Author: Monsere, Christopher Year: 2017 Over the last decade, the transportation agencies in Oregon have systematically enhanced many pedestrian crossings at mid-block locations with Rectangular Rapid Flashing Beacons (RRFBs), Flashing Yellow Beacons (Flash), and high visibility crosswalk markings (Hi-Vis). Enhancements often included the installation of refuge medians. This study explored the safety performance of these enhanced crossings, categorized by enhancement type. Data were collected on 191 crossings that included installation year, geometric features, surrounding land use, traffic volumes, and the number of crashes. Because pedestrian volume at the locations was unavailable, a pedestrian activity level variable was developed. Target crashes for analysis were identified as pedestrian and rear-end. The analysis of the before-after crash patterns showed a reduction in the pedestrian crash severity after the installation of the crosswalk enhancements. Risk ratios, calculated by the unadjusted crash frequency relative to the years of operation in each analysis category, were calculated. For pedestrian crashes, risk ratios increased with the number of lanes, posted speed, and estimated pedestrian activity level. Similar trends were observed for rear-end crashes. Due to sample size limitations, safety effectiveness was only estimated for the 19 RRFBs locations. Lack of pedestrian volumes limited the development of a safety performance function (SPF) for the pedestrian crash types. However, a rear-end crash SPF was estimated. Standard methods to estimate a crash modification factor (CMF) were attempted. The recommended CMF for pedestrian crashes is 0.64 +/- 0.26 using a simple before-after analysis and 0.93 +/- 0.22 for rear-end crashes using an empirical Bayes analysis. The final report that the presentation is derived from is available: https://doi.org/10.15760/trec.168 Title: Safety Effectiveness of Pedestrian Crossing Treatments Author: Monsere, Christopher Year: 2017 Over the last decade, the transportation agencies in Oregon have systematically enhanced many pedestrian crossings at mid-block locations with Rectangular Rapid Flashing Beacons (RRFBs), Flashing Yellow Beacons (Flash), and high visibility crosswalk markings (Hi-Vis). Enhancements often included the installation of refuge medians. This study explored the safety performance of these enhanced crossings, categorized by enhancement type. Data were collected on 191 crossings that included installation year, geometric features, surrounding land use, traffic volumes, and the number of crashes. Because pedestrian volume at the locations was unavailable, a pedestrian activity level variable was developed. Target crashes for analysis were identified as pedestrian and rear-end. The analysis of the before-after crash patterns showed a reduction in the pedestrian crash severity after the installation of the crosswalk enhancements. Risk ratios, calculated by the unadjusted crash frequency relative to the years of operation in each analysis category, were calculated. For pedestrian crashes, risk ratios increased with the number of lanes, posted speed, and estimated pedestrian activity level. Similar trends were observed for rear-end crashes. Due to sample size limitations, safety effectiveness was only estimated for the 19 RRFBs locations. Lack of pedestrian volumes limited the development of a safety performance function (SPF) for the pedestrian crash types. However, a rear-end crash SPF was estimated. Standard methods to estimate a crash modification factor (CMF) were attempted. The recommended CMF for pedestrian crashes is 0.64 +/- 0.26 using a simple before-after analysis and 0.93 +/- 0.22 for rear-end crashes using an empirical Bayes analysis. The final report that the presentation is derived from is available: https://doi.org/10.15760/trec.168 Close

• 8. [Article] Hydrodynamics and Morphology in the Ems/Dollard Estuary: Review of Models, Measurements, Scientific Literature, and the Effects of Changing Conditions

  The Ems estuary has constantly changed over the past centuries both from man-made and natural influences. On the time scale of thousands of years, sea level rise has created the estuary and dynamically ...

  Citation × Citation Citation Abstract Copy Title: Hydrodynamics and Morphology in the Ems/Dollard Estuary: Review of Models, Measurements, Scientific Literature, and the Effects of Changing Conditions Author: Talke, Stefan A., de Swart, Huib E. Year: 2006 The Ems estuary has constantly changed over the past centuries both from man-made and natural influences. On the time scale of thousands of years, sea level rise has created the estuary and dynamically changed its boundaries. More recently, storm surges created the Dollard sub-basin in the 14th -15th centuries. Beginning in the 16th century, diking and reclamation of land has greatly altered the surface area of the Ems estuary, particularly in the Dollard. These natural and anthropogenic changes to the surface area of the Ems altered the flow patterns of water, the tidal characteristics, and the patterns of sediment deposition and erosion. Since 1945, reclamation of land has halted and the borders of the Ems estuary have changed little. Sea level rise has continued, and over the past 40 years the rate of increase in mean high water (MHW) along the German coast has accelerated to 40 cm/ century. Climate has varied on a decadal time scale due to long-term variations in the North Atlantic Oscillation (NAO), which controls precipitation, temperature, and the direction and magnitude of winds. Between 1960 and 1990 the most intense variation in the NAO index on record was observed. As a result the magnitude and frequency of storm surges increased, and mean wave heights increased at 1-2 cm/year. Currently the NAO index—and therefore storminess—is trending downwards. Over the longer term, global warming models predict an average temperature rise of 2 degrees Celsius over the next century. A doubling of CO2 is expected to increase sea level by 30 cm, while the significant wind speed and wave heights in the North Sea are predicted to increase by 50 cm/s and 50 cm, respectively. Beginning in the late 1950’s, dredging activity and construction measures in harbours and shipping channels greatly altered the physical processes in the Ems. Deepening and streamlining the Ems River and shipping channel between the 1960s and 1990s decreased the hydraulic roughness and increased the tidal range in the river above Emden by as much as 1.5 m. At the turbidity maximum between Emden and Papenburg, concentrations of sediment are currently between 1-2 orders of magnitude larger than in the 1950’s, and fluid mud layers of several meters thickness occur. Other man-made changes, such as gas pipelines and the expansion of harbours, have often caused significant, but more localized, changes to the estuary. Between the mid 19th century and the 1970’s, dumping of organic waste—agricultural, industrial, and human—severely stressed the ecology of the Dollard sub-basin in particular. Since then the input of organic waste has been greatly reduced and anoxic conditions eliminated. However, the increase in turbidity at the turbidity maximum has caused depleted oxygen concentrations and periodic anoxia between Pogum and Papenburg during the summer months (personal communication, H. Juergens; Talke et al, 2005). The Ems is a relatively well studied estuary. Significant research projects have included the BOEDE project in the 1970’s --1980’s and the BOA and INTRAMUD projects in the 1990’s. These projects and other efforts have amassed a deep literature in the knowledge of tidal flats, fluid mud and flocculation, and mixing and dispersion processes. Projects currently underway are focusing on tidal dynamics and the affects of dredging in the high turbidity zone between Emden and Herbrum. Optimal management of the estuary is the goal of the HARBASINS project. Many analytical and numerical models have been applied to the Ems estuary to estimate tidal range, storm surges, wave fields, sediment transport, and mixing and dispersion processes. Analytical models to estimate mixing of scalars and sediment fluxes (Sediment Trend Analysis) have been extensively used. Numerical models such as WAQUA, unTRIM, MIKE3, Telemac 2D, SWAN, Delft 3D –Sed, and others have been applied to the Ems. While reasonable results are found for short term processes (order of days), long-term morphological change cannot yet be predicted. For the Ems catchement basin, the numerical models REGFLUD and FLUMAGIS are used to estimate nutrient inputs from diffuse sources and to visualize and evaluate the effects of land-use change. Title: Hydrodynamics and Morphology in the Ems/Dollard Estuary: Review of Models, Measurements, Scientific Literature, and the Effects of Changing Conditions Author: Talke, Stefan A., de Swart, Huib E. Year: 2006 The Ems estuary has constantly changed over the past centuries both from man-made and natural influences. On the time scale of thousands of years, sea level rise has created the estuary and dynamically changed its boundaries. More recently, storm surges created the Dollard sub-basin in the 14th -15th centuries. Beginning in the 16th century, diking and reclamation of land has greatly altered the surface area of the Ems estuary, particularly in the Dollard. These natural and anthropogenic changes to the surface area of the Ems altered the flow patterns of water, the tidal characteristics, and the patterns of sediment deposition and erosion. Since 1945, reclamation of land has halted and the borders of the Ems estuary have changed little. Sea level rise has continued, and over the past 40 years the rate of increase in mean high water (MHW) along the German coast has accelerated to 40 cm/ century. Climate has varied on a decadal time scale due to long-term variations in the North Atlantic Oscillation (NAO), which controls precipitation, temperature, and the direction and magnitude of winds. Between 1960 and 1990 the most intense variation in the NAO index on record was observed. As a result the magnitude and frequency of storm surges increased, and mean wave heights increased at 1-2 cm/year. Currently the NAO index—and therefore storminess—is trending downwards. Over the longer term, global warming models predict an average temperature rise of 2 degrees Celsius over the next century. A doubling of CO2 is expected to increase sea level by 30 cm, while the significant wind speed and wave heights in the North Sea are predicted to increase by 50 cm/s and 50 cm, respectively. Beginning in the late 1950’s, dredging activity and construction measures in harbours and shipping channels greatly altered the physical processes in the Ems. Deepening and streamlining the Ems River and shipping channel between the 1960s and 1990s decreased the hydraulic roughness and increased the tidal range in the river above Emden by as much as 1.5 m. At the turbidity maximum between Emden and Papenburg, concentrations of sediment are currently between 1-2 orders of magnitude larger than in the 1950’s, and fluid mud layers of several meters thickness occur. Other man-made changes, such as gas pipelines and the expansion of harbours, have often caused significant, but more localized, changes to the estuary. Between the mid 19th century and the 1970’s, dumping of organic waste—agricultural, industrial, and human—severely stressed the ecology of the Dollard sub-basin in particular. Since then the input of organic waste has been greatly reduced and anoxic conditions eliminated. However, the increase in turbidity at the turbidity maximum has caused depleted oxygen concentrations and periodic anoxia between Pogum and Papenburg during the summer months (personal communication, H. Juergens; Talke et al, 2005). The Ems is a relatively well studied estuary. Significant research projects have included the BOEDE project in the 1970’s --1980’s and the BOA and INTRAMUD projects in the 1990’s. These projects and other efforts have amassed a deep literature in the knowledge of tidal flats, fluid mud and flocculation, and mixing and dispersion processes. Projects currently underway are focusing on tidal dynamics and the affects of dredging in the high turbidity zone between Emden and Herbrum. Optimal management of the estuary is the goal of the HARBASINS project. Many analytical and numerical models have been applied to the Ems estuary to estimate tidal range, storm surges, wave fields, sediment transport, and mixing and dispersion processes. Analytical models to estimate mixing of scalars and sediment fluxes (Sediment Trend Analysis) have been extensively used. Numerical models such as WAQUA, unTRIM, MIKE3, Telemac 2D, SWAN, Delft 3D –Sed, and others have been applied to the Ems. While reasonable results are found for short term processes (order of days), long-term morphological change cannot yet be predicted. For the Ems catchement basin, the numerical models REGFLUD and FLUMAGIS are used to estimate nutrient inputs from diffuse sources and to visualize and evaluate the effects of land-use change. Close

• 9. [Article] The Effect of Tidal Asymmetry and Temporal Settling Lag on Sediment Trapping in Tidal Estuaries

  Over decades and centuries, the mean depth of estuaries changes due to sea-level rise, land subsidence, infilling, and dredging projects. These processes produce changes in relative roughness (friction) ...

  Citation × Citation Citation Abstract Copy Title: The Effect of Tidal Asymmetry and Temporal Settling Lag on Sediment Trapping in Tidal Estuaries Author: Chernetsky, Alexander S., Schuttelaars, Henk M., Talke, Stefan A. Year: 2010 Over decades and centuries, the mean depth of estuaries changes due to sea-level rise, land subsidence, infilling, and dredging projects. These processes produce changes in relative roughness (friction) and mixing, resulting in fundamental changes in the characteristics of the horizontal (velocity) and vertical tides (sea surface elevation) and the dynamics of sediment trapping. To investigate such changes, a 2DV model is developed. The model equations consist of the width-averaged shallow water equations and a sediment balance equation. Together with the condition of morphodynamic equilibrium, these equations are solved analytically by making a regular expansion of the various physical variables in a small parameter. Using these analytic solutions, we are able to gain insight into the fundamental physical processes resulting in sediment trapping in an estuary by studying various forcings separately. As a case study, we consider the Ems estuary. Between 1980 and 2005, successive deepening of the Ems estuary has significantly altered the tidal and sediment dynamics. The tidal range and the surface sediment concentration has increased and the position of the turbidity zone has shifted into the freshwater zone. The model is used to determine the causes of these historical changes. It is found that the increase of the tidal amplitude toward the end of the embayment is the combined effect of the deepening of the estuary and a 37% and 50% reduction in the vertical eddy viscosity and stress parameter, respectively. The physical mechanism resulting in the trapping of sediment, the number of trapping regions, and their sensitivity to grain size are explained by careful analysis of the various contributions of the residual sediment transport. It is found that sediment is trapped in the estuary by a delicate balance between the M 2 transport and the residual transport for fine sediment (\emphws=0.2 mm s −1) and the residual, M 2 and M 4 transports for coarser sediment (\emphws=2 mm s − 1). The upstream movement of the estuarine turbidity maximum into the freshwater zone in 2005 is mainly the result of changes in tidal asymmetry. Moreover, the difference between the sediment distribution for different grain sizes in the same year can be attributed to changes in the temporal settling lag. Title: The Effect of Tidal Asymmetry and Temporal Settling Lag on Sediment Trapping in Tidal Estuaries Author: Chernetsky, Alexander S., Schuttelaars, Henk M., Talke, Stefan A. Year: 2010 Over decades and centuries, the mean depth of estuaries changes due to sea-level rise, land subsidence, infilling, and dredging projects. These processes produce changes in relative roughness (friction) and mixing, resulting in fundamental changes in the characteristics of the horizontal (velocity) and vertical tides (sea surface elevation) and the dynamics of sediment trapping. To investigate such changes, a 2DV model is developed. The model equations consist of the width-averaged shallow water equations and a sediment balance equation. Together with the condition of morphodynamic equilibrium, these equations are solved analytically by making a regular expansion of the various physical variables in a small parameter. Using these analytic solutions, we are able to gain insight into the fundamental physical processes resulting in sediment trapping in an estuary by studying various forcings separately. As a case study, we consider the Ems estuary. Between 1980 and 2005, successive deepening of the Ems estuary has significantly altered the tidal and sediment dynamics. The tidal range and the surface sediment concentration has increased and the position of the turbidity zone has shifted into the freshwater zone. The model is used to determine the causes of these historical changes. It is found that the increase of the tidal amplitude toward the end of the embayment is the combined effect of the deepening of the estuary and a 37% and 50% reduction in the vertical eddy viscosity and stress parameter, respectively. The physical mechanism resulting in the trapping of sediment, the number of trapping regions, and their sensitivity to grain size are explained by careful analysis of the various contributions of the residual sediment transport. It is found that sediment is trapped in the estuary by a delicate balance between the M 2 transport and the residual transport for fine sediment (\emphws=0.2 mm s −1) and the residual, M 2 and M 4 transports for coarser sediment (\emphws=2 mm s − 1). The upstream movement of the estuarine turbidity maximum into the freshwater zone in 2005 is mainly the result of changes in tidal asymmetry. Moreover, the difference between the sediment distribution for different grain sizes in the same year can be attributed to changes in the temporal settling lag. Close

• 10. [Article] Wider Dissemination of Household Travel Survey Data Using Geographical Perturbation Methods

  Public agencies spend vast amounts of money collecting information about passenger travel in household travel surveys. These data are valuable for the rich and detailed information they provide, which ...

  Citation × Citation Citation Abstract Copy Title: Wider Dissemination of Household Travel Survey Data Using Geographical Perturbation Methods Author: Clifton, Kelly J., Gehrke, Steven R. Year: 2014 Public agencies spend vast amounts of money collecting information about passenger travel in household travel surveys. These data are valuable for the rich and detailed information they provide, which contribute to regional and statewide travel demand models. These data have utility beyond travel demand modeling in their application to transportation policy and travel behavior research. As the demand on these data increase, so have the quantity of information collected. Detailed geospatial referencing of the home, work and other travel destinations are common practice and permit the integration with other spatially archived data sources, such as land use characteristics, transportation system information, and other built environment, social and economic data. Other public agencies, private consultancies, non-profits and educational institutions may benefit from access to the original data with applications to areas such public health, equity, transportation safety and urban planning. Oregon Modeling Collaborative (OMC) has entered into an agreement with Oregon Modeling Steering Committee (OMSC) to host and make available Oregon Household Activity Survey (OHAS) datasets. But wide distribution of these important and expensive data is limited by the requirement to protect the confidentiality of survey participants, who are guaranteed anonymity in exchange for participation. Data are often aggregated to a geographic level such as Census tracts or transportation analysis zones (TAZs) before disseminating to the public, which limits the utility of this information. This project aims to develop a methodology to permit dissemination of these spatially-explicit data to a wider range of public constituents while at the same time, protecting the identities of study participants. Making use of these data, this project will use geographical perturbation methods to add noise to the original data to protect confidentiality while at the same time allowing the detailed geo-spatial referencing to be included in the disseminated data. The process includes: The coordinates (locations) will be geographically perturbed (masked) so that they do not reveal the identity of the traveler while at the same time retaining spatial relevance and resolution. Here the limits of the perturbation (minimum and maximum displacement) need to be determined that a) ensure confidentiality and b) minimize the errors introduced to the data. The original and perturbed (masked) data will be compared using various statistical approaches to develop a set of confidence measures for different types of transportation applications. For example, geographically perturbed (masked) may be more robust for automobile travel measures, such as vehicle miles traveled (VMT) or transit accessibility than for detailed pedestrian or bicycle trip attributes. This exercise will allow spatially-explicit OHAS data to be released to the public with some information about the confidence to which it can be applied. These data will be archived at Portland State University and made available to the public. The information and algorithms can be shared with other agencies collecting and archiving travel data, such as the National Household Travel Survey, metropolitan planning organizations and state departments of transportation, to permit wider dissemination of their data. Title: Wider Dissemination of Household Travel Survey Data Using Geographical Perturbation Methods Author: Clifton, Kelly J., Gehrke, Steven R. Year: 2014 Public agencies spend vast amounts of money collecting information about passenger travel in household travel surveys. These data are valuable for the rich and detailed information they provide, which contribute to regional and statewide travel demand models. These data have utility beyond travel demand modeling in their application to transportation policy and travel behavior research. As the demand on these data increase, so have the quantity of information collected. Detailed geospatial referencing of the home, work and other travel destinations are common practice and permit the integration with other spatially archived data sources, such as land use characteristics, transportation system information, and other built environment, social and economic data. Other public agencies, private consultancies, non-profits and educational institutions may benefit from access to the original data with applications to areas such public health, equity, transportation safety and urban planning. Oregon Modeling Collaborative (OMC) has entered into an agreement with Oregon Modeling Steering Committee (OMSC) to host and make available Oregon Household Activity Survey (OHAS) datasets. But wide distribution of these important and expensive data is limited by the requirement to protect the confidentiality of survey participants, who are guaranteed anonymity in exchange for participation. Data are often aggregated to a geographic level such as Census tracts or transportation analysis zones (TAZs) before disseminating to the public, which limits the utility of this information. This project aims to develop a methodology to permit dissemination of these spatially-explicit data to a wider range of public constituents while at the same time, protecting the identities of study participants. Making use of these data, this project will use geographical perturbation methods to add noise to the original data to protect confidentiality while at the same time allowing the detailed geo-spatial referencing to be included in the disseminated data. The process includes: The coordinates (locations) will be geographically perturbed (masked) so that they do not reveal the identity of the traveler while at the same time retaining spatial relevance and resolution. Here the limits of the perturbation (minimum and maximum displacement) need to be determined that a) ensure confidentiality and b) minimize the errors introduced to the data. The original and perturbed (masked) data will be compared using various statistical approaches to develop a set of confidence measures for different types of transportation applications. For example, geographically perturbed (masked) may be more robust for automobile travel measures, such as vehicle miles traveled (VMT) or transit accessibility than for detailed pedestrian or bicycle trip attributes. This exercise will allow spatially-explicit OHAS data to be released to the public with some information about the confidence to which it can be applied. These data will be archived at Portland State University and made available to the public. The information and algorithms can be shared with other agencies collecting and archiving travel data, such as the National Household Travel Survey, metropolitan planning organizations and state departments of transportation, to permit wider dissemination of their data. Close