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• 1. [Article] Hydrology and Flooding

  Abstract -- The Lower Nehalem Watershed Council has looked at several issues in more detail than was possible in the PSU assessment. This document on hydrology and flooding is one of those issues that ...

  Citation × Citation Citation Abstract Copy Title: Hydrology and Flooding Abstract -- The Lower Nehalem Watershed Council has looked at several issues in more detail than was possible in the PSU assessment. This document on hydrology and flooding is one of those issues that the watershed council has looked at more closely. Document sections include background information including the 1996 flood, flood history, flood damage control, hydraulic models, flood alternatives for the Nehalem Basin, and Criteria for Evaluating Alternate Flood Control Projects. Title: Hydrology and Flooding Abstract -- The Lower Nehalem Watershed Council has looked at several issues in more detail than was possible in the PSU assessment. This document on hydrology and flooding is one of those issues that the watershed council has looked at more closely. Document sections include background information including the 1996 flood, flood history, flood damage control, hydraulic models, flood alternatives for the Nehalem Basin, and Criteria for Evaluating Alternate Flood Control Projects. Close

• 2. [Article] The problems and issues of implementing the National Flood Insurance Act in Oregon

  Floods and ensuing damage have always been a problem for man. Initial reaction to the frequent destruction was to avoid siting permanent domiciles on flood-prone lands. As a result of increasing population ...

  Citation × Citation Citation Abstract Copy Title: The problems and issues of implementing the National Flood Insurance Act in Oregon Author: Emmer, Rod E. Floods and ensuing damage have always been a problem for man. Initial reaction to the frequent destruction was to avoid siting permanent domiciles on flood-prone lands. As a result of increasing population and pressure for development, flood control structures were built. Instead of reducing flood losses, however, flood control projects encouraged development of more hazardous zones by giving a false sense of security to flood plain occupants. In the 1960's Congress began to evaluate alternatives to flood control and abatement projects in an attempt to retard and eventually eliminate further flood losses. In 1968 it sought to resolve the problems of aid to flood victims and reduce the increasing losses by enacting the National Flood Insurance Act (NFIA). If implemented the Act will furnish assistance to flood victims through insurance policies and reduce further losses by establishing a mandatory set of minimum standards for land use on flood plains. This study analyzes the problems and issues of implementing the NFIA in Oregon between enactment of the law in 1968 and June 1972. The study reveals that extensive revisions of local ordinances will be necessary if participating governments are to meet the minimum standards of the Federal Insurance Administration. The four standards most commonly omitted in the regulations promulgated by local governments are those pertaining to: fill in the floodway, raising utilities above the 100-year flood level, providing adequate drainage, and considering neighboring flood plain programs. A sample of flood plain occupants suggests that the availability of flood insurance and the potential flood hazard of an area are, not widely known. In sum, the implementation of the NFIA proceeded slowly between enactment in 1968 and the summer of 1972. Even where it was accepted by local governments, the ordinance would not restrict flood plain use to the degree Congress intended. Title: The problems and issues of implementing the National Flood Insurance Act in Oregon Author: Emmer, Rod E. Floods and ensuing damage have always been a problem for man. Initial reaction to the frequent destruction was to avoid siting permanent domiciles on flood-prone lands. As a result of increasing population and pressure for development, flood control structures were built. Instead of reducing flood losses, however, flood control projects encouraged development of more hazardous zones by giving a false sense of security to flood plain occupants. In the 1960's Congress began to evaluate alternatives to flood control and abatement projects in an attempt to retard and eventually eliminate further flood losses. In 1968 it sought to resolve the problems of aid to flood victims and reduce the increasing losses by enacting the National Flood Insurance Act (NFIA). If implemented the Act will furnish assistance to flood victims through insurance policies and reduce further losses by establishing a mandatory set of minimum standards for land use on flood plains. This study analyzes the problems and issues of implementing the NFIA in Oregon between enactment of the law in 1968 and June 1972. The study reveals that extensive revisions of local ordinances will be necessary if participating governments are to meet the minimum standards of the Federal Insurance Administration. The four standards most commonly omitted in the regulations promulgated by local governments are those pertaining to: fill in the floodway, raising utilities above the 100-year flood level, providing adequate drainage, and considering neighboring flood plain programs. A sample of flood plain occupants suggests that the availability of flood insurance and the potential flood hazard of an area are, not widely known. In sum, the implementation of the NFIA proceeded slowly between enactment in 1968 and the summer of 1972. Even where it was accepted by local governments, the ordinance would not restrict flood plain use to the degree Congress intended. Close

• 3. [Article] Authorizing preliminary examination of Yaquina River and its tributaries in Oregon with view to control of floods

  Report to accompany House resolution 5776. "The floods of 1933 caused severe damage in all portions of the Yaquina River Valley and damaging floods occur at intervals from 2 to 4 years. It is believed ...

  Citation × Citation Citation Abstract Copy Title: Authorizing preliminary examination of Yaquina River and its tributaries in Oregon with view to control of floods Author: United States. Congress. House. Committee on Flood Control Report to accompany House resolution 5776. "The floods of 1933 caused severe damage in all portions of the Yaquina River Valley and damaging floods occur at intervals from 2 to 4 years. It is believed these floods warrant investigation with a view to determining flood-protective measures." Title: Authorizing preliminary examination of Yaquina River and its tributaries in Oregon with view to control of floods Author: United States. Congress. House. Committee on Flood Control Report to accompany House resolution 5776. "The floods of 1933 caused severe damage in all portions of the Yaquina River Valley and damaging floods occur at intervals from 2 to 4 years. It is believed these floods warrant investigation with a view to determining flood-protective measures." Close

• 4. [Article] Tradeoffs and Preferences between Flood Mitigation Measures

  Floods remain the world’s most destructive natural hazard, despite centuries of efforts to minimize losses. Understanding public preferences for flood mitigation measures, and the impacts of these measures, ...

  Citation × Citation Citation Abstract Copy Title: Tradeoffs and Preferences between Flood Mitigation Measures Author: Byron, Elizabeth G Floods remain the world’s most destructive natural hazard, despite centuries of efforts to minimize losses. Understanding public preferences for flood mitigation measures, and the impacts of these measures, is key to minimizing flood-induced losses. This study quantified tradeoffs between flood mitigation measures and determined factors that influence public preferences for those flood mitigation measures in college student and professionals familiar with environmental issues. To quantify tradeoffs, we modeled economic, social, and environmental costs, as well as risk of failure, for dams, early warning systems, and floodplain reconnection. To assess public preferences, we distributed an online survey based upon our modeled values. Results suggested that people with previous flood experience support different mitigation practices than people with no prior experience. Additionally, people who support different flood mitigation practices prioritize different factors. These findings can improve flood mitigation planning and help prioritize the expenditure of limited public funding on different mitigation options. Title: Tradeoffs and Preferences between Flood Mitigation Measures Author: Byron, Elizabeth G Floods remain the world’s most destructive natural hazard, despite centuries of efforts to minimize losses. Understanding public preferences for flood mitigation measures, and the impacts of these measures, is key to minimizing flood-induced losses. This study quantified tradeoffs between flood mitigation measures and determined factors that influence public preferences for those flood mitigation measures in college student and professionals familiar with environmental issues. To quantify tradeoffs, we modeled economic, social, and environmental costs, as well as risk of failure, for dams, early warning systems, and floodplain reconnection. To assess public preferences, we distributed an online survey based upon our modeled values. Results suggested that people with previous flood experience support different mitigation practices than people with no prior experience. Additionally, people who support different flood mitigation practices prioritize different factors. These findings can improve flood mitigation planning and help prioritize the expenditure of limited public funding on different mitigation options. Close

• 5. [Article] Toward More Robust Extreme Flood Prediction by Bayesian Hierarchical and Multimodeling

  Flood information, especially extreme flood, is necessary for any large hydraulic structure design and flood risk management. Flood mitigation also requires a comprehensive assessment of flood risk and ...

  Citation × Citation Citation Abstract Copy Title: Toward More Robust Extreme Flood Prediction by Bayesian Hierarchical and Multimodeling Author: Yan, Hongxiang, Moradkhani, Hamid Year: 2016 Flood information, especially extreme flood, is necessary for any large hydraulic structure design and flood risk management. Flood mitigation also requires a comprehensive assessment of flood risk and an explicit quantification of the flood uncertainty. In the present study, we use a multimodel ensemble approach based on Bayesian model averaging (BMA) method to account for model structure and distribution uncertainties. The usefulness of this approach is assessed by a case study over the Willamette River Basin (WRB) in Pacific Northwest, USA. Besides the standard log-Pearson Type III distribution, we also identified that the generalized extreme value and three-parameter lognormal distributions were both potential distributions in WRB. Three different statistical models, including the Bulletin-17B quantile model, index-flood model, and spatial Bayesian hierarchical model, were considered in the study. The BMA method is then used to assign weights to different models, where better performing model receives higher weights. It was found that the major uncertainty in extreme flood prediction is contributed by model structure, while the choice of distribution plays a lesser important role in quantification of flood uncertainty. The BMA approach provides a more robust extreme flood prediction than any single model. Title: Toward More Robust Extreme Flood Prediction by Bayesian Hierarchical and Multimodeling Author: Yan, Hongxiang, Moradkhani, Hamid Year: 2016 Flood information, especially extreme flood, is necessary for any large hydraulic structure design and flood risk management. Flood mitigation also requires a comprehensive assessment of flood risk and an explicit quantification of the flood uncertainty. In the present study, we use a multimodel ensemble approach based on Bayesian model averaging (BMA) method to account for model structure and distribution uncertainties. The usefulness of this approach is assessed by a case study over the Willamette River Basin (WRB) in Pacific Northwest, USA. Besides the standard log-Pearson Type III distribution, we also identified that the generalized extreme value and three-parameter lognormal distributions were both potential distributions in WRB. Three different statistical models, including the Bulletin-17B quantile model, index-flood model, and spatial Bayesian hierarchical model, were considered in the study. The BMA method is then used to assign weights to different models, where better performing model receives higher weights. It was found that the major uncertainty in extreme flood prediction is contributed by model structure, while the choice of distribution plays a lesser important role in quantification of flood uncertainty. The BMA approach provides a more robust extreme flood prediction than any single model. Close

• 6. [Article] Techniques for identifying flood plains in Oregon

  Seven methods for delineating flood plains were evaluated. The methods are classified : (1) Geomorphic Technique; (2) Soils Technique; (3) Botanical Technique; (4) Hydrologic Technique; (5) Hydrologic- Hydraulic ...

  Citation × Citation Citation Abstract Copy Title: Techniques for identifying flood plains in Oregon Author: Reckendorf, Frank Fred Seven methods for delineating flood plains were evaluated. The methods are classified : (1) Geomorphic Technique; (2) Soils Technique; (3) Botanical Technique; (4) Hydrologic Technique; (5) Hydrologic- Hydraulic Technique; (6) Historical Technique; and (7) "Combination Method". All of the methods, except the Botanical Technique and the Hydrologic-Hydraulic Technique, were compared on sample flood plain reaches throughout Oregon. Chronological sequences of natural flood plains were identified and mapped based on: (1) scarps separating two or more flood plain or terrace geomorphic surfaces and (2) the abundance and degree of photographic expression of flood plain features such as meander scrolls, point bars, oxbows, oxbow lakes, sloughs, old channels, natural levees, and sand splays. Soils were useful in delineating flood plain areas since soils cannot be older than the alluvium in which they form or older than the associated geomorphic surface. Since soils exhibit increasing development of genetic horizons with increasing age, delineation of younger bottomland soils from older soils on higher flood plains or terraces, usually results in the delineation of flood prone areas. Since floods scar bark, or prune branches or the tops of trees, botanical studies can provide information about the flood date, flood stage, and area flooded. The number of annual tree rings that have grown since scarring of the bark, or the age of sprouts that have grown since flood damage occurred, are equal to the number of growing seasons since the trees were damaged. The thickness of sediment above the base of a tree serves as a measure of the rate of sediment accumulation above the surface on which the tree was located. Historically flood plains have been recognized and delineated by (1) aerial or ground photographs taken during floods; (2) high flood marks such as float debris; and (3) locating flooded areas from field interviews. Previous hydrologic studies have related the stage of rivers at gage locations to the adjacent flood plain areas, and in this manner flood plains have been recognized and delineated. In addition, hydraulic studies have been used to determine flood stages at valley cross sections, for specific flood frequencies. Flood plain width therefore may be determined from the valley cross sections. Use of both the gaging stations and the valley cross sections results in a hydrologic-hydraulic procedure for flood plain identification. The particular flood plain mapping technique that is most applicable in any given study depends on the data available, the purpose and scale of mapping, and the field conditions. Each technique has deficiencies; therefore, the "Combination Method" is introduced to utilize the most useful information from each technique. Collective use of two or more techniques is called the "Combination Method". The relative accuracy of the Geomorphic Technique, Soils Technique, Historical Technique, Hydrologic Technique, and "Combination Method" was determined for some representative stream reaches in Oregon. Areas flooded in a 100 year average recurrence interval event were compared for all methods available in 10 study areas, which ranged from semiarid to humid environments. For the areas compared the "Combination Method" was used as the base method. The Geomorphic Technique was the method most consistently comparable with the "Combination Method". The Soils Technique was generally accurate for delimiting flood plains, with some studies showing excellent correlation. The three study areas with comparisons using the Historic Technique were generally good and most discrepancies occurred where approximate historical flood lines were drawn for inaccessible areas. The Hydrologic Technique showed by fax the poorest correlation with the "Combination Method" as well as with all other methods. The differences between the "Combination Method" and the Hydrologic Technique are explained for specific maps, but in general the major problem was the lack of field correlation of crest staff gage flood elevations, with the general flood plain area away from the river. No independent evaluations were made of the Hydraulic Technique, although the Hydrologic-Hydraulic Technique was included as part of the "Combination Method" in one study. Title: Techniques for identifying flood plains in Oregon Author: Reckendorf, Frank Fred Seven methods for delineating flood plains were evaluated. The methods are classified : (1) Geomorphic Technique; (2) Soils Technique; (3) Botanical Technique; (4) Hydrologic Technique; (5) Hydrologic- Hydraulic Technique; (6) Historical Technique; and (7) "Combination Method". All of the methods, except the Botanical Technique and the Hydrologic-Hydraulic Technique, were compared on sample flood plain reaches throughout Oregon. Chronological sequences of natural flood plains were identified and mapped based on: (1) scarps separating two or more flood plain or terrace geomorphic surfaces and (2) the abundance and degree of photographic expression of flood plain features such as meander scrolls, point bars, oxbows, oxbow lakes, sloughs, old channels, natural levees, and sand splays. Soils were useful in delineating flood plain areas since soils cannot be older than the alluvium in which they form or older than the associated geomorphic surface. Since soils exhibit increasing development of genetic horizons with increasing age, delineation of younger bottomland soils from older soils on higher flood plains or terraces, usually results in the delineation of flood prone areas. Since floods scar bark, or prune branches or the tops of trees, botanical studies can provide information about the flood date, flood stage, and area flooded. The number of annual tree rings that have grown since scarring of the bark, or the age of sprouts that have grown since flood damage occurred, are equal to the number of growing seasons since the trees were damaged. The thickness of sediment above the base of a tree serves as a measure of the rate of sediment accumulation above the surface on which the tree was located. Historically flood plains have been recognized and delineated by (1) aerial or ground photographs taken during floods; (2) high flood marks such as float debris; and (3) locating flooded areas from field interviews. Previous hydrologic studies have related the stage of rivers at gage locations to the adjacent flood plain areas, and in this manner flood plains have been recognized and delineated. In addition, hydraulic studies have been used to determine flood stages at valley cross sections, for specific flood frequencies. Flood plain width therefore may be determined from the valley cross sections. Use of both the gaging stations and the valley cross sections results in a hydrologic-hydraulic procedure for flood plain identification. The particular flood plain mapping technique that is most applicable in any given study depends on the data available, the purpose and scale of mapping, and the field conditions. Each technique has deficiencies; therefore, the "Combination Method" is introduced to utilize the most useful information from each technique. Collective use of two or more techniques is called the "Combination Method". The relative accuracy of the Geomorphic Technique, Soils Technique, Historical Technique, Hydrologic Technique, and "Combination Method" was determined for some representative stream reaches in Oregon. Areas flooded in a 100 year average recurrence interval event were compared for all methods available in 10 study areas, which ranged from semiarid to humid environments. For the areas compared the "Combination Method" was used as the base method. The Geomorphic Technique was the method most consistently comparable with the "Combination Method". The Soils Technique was generally accurate for delimiting flood plains, with some studies showing excellent correlation. The three study areas with comparisons using the Historic Technique were generally good and most discrepancies occurred where approximate historical flood lines were drawn for inaccessible areas. The Hydrologic Technique showed by fax the poorest correlation with the "Combination Method" as well as with all other methods. The differences between the "Combination Method" and the Hydrologic Technique are explained for specific maps, but in general the major problem was the lack of field correlation of crest staff gage flood elevations, with the general flood plain area away from the river. No independent evaluations were made of the Hydraulic Technique, although the Hydrologic-Hydraulic Technique was included as part of the "Combination Method" in one study. Close

• 7. [Article] Highlights in the changing resource perception and land use of the Willamette River flood plain, Albany-Corvallis area

  Taking advantage of a favorable physical system but also risking the hazards of flooding, man has long occupied flood plain land. He has attempted to adjust rivers to his needs in order to reduce flood ...

  Citation × Citation Citation Abstract Copy Title: Highlights in the changing resource perception and land use of the Willamette River flood plain, Albany-Corvallis area Author: Lewis, Anthony J. Taking advantage of a favorable physical system but also risking the hazards of flooding, man has long occupied flood plain land. He has attempted to adjust rivers to his needs in order to reduce flood loss, but the rising cost of flood protection accompanied by an increase in flood damage potential warrants that a course of human adjustment be undertaken on occupied flood plains. The flood plain of the Willamette River between Albany and Corvallis, Oregon provides an opportunity to study the resource use of a flood plain in a relatively youthful stage of economic development, having the physical as sets and limitations of most flood plains. By studying the physical system and changing resource utilization of this flood plain, an evaluation has been made of the present and possible future use of its resource base. Land use has evolved from a primitive stage of hunting, fishing, and gathering to intensive agricultural endeavors with some residential and commercial development. Resource utilization during the same period has changed from a dependence on the flora and fauna for food and clothing to a dependence on the soil and climate, flood protection, markets, labor, and so forth. The change has been towards a more intensive, higher valued use of the land with more sophisticated land management practices. A relatively satisfactory arrangement of land use presently exists on the Albany-Corvallis flood plain; however, present land use practices in the study area reflect a rational use of flood subjected land primarily because the pressures of industrial and commercial development have not yet been heavily felt. Residential expansion, however, has taken place at an alarming rate. Many of the human adjustments suggested by Gilbert White in his flood plain studies at the University of Chicago are applicable to a future course of orderly occupance for the Albany-Corvallis flood plain. One of the more applicable local forms of adjustment is the directing of flood plain use which involves land elevation, land use regulation, structural modifications, flood insurance, relief, and better warning systems. The construction of engineering works for flood abatement represents the traditional form of river adjustment in the Willamette Basin. The building of storage dams upstream of the study area has lowered the height of the flood crest but has also given many flood plain dwellers a feeling of false security. Channel improvements and bank revetments are the main form of river adjustment in the study area, and they help to reduce the danger of crop drowning and to control bank erosion. Title: Highlights in the changing resource perception and land use of the Willamette River flood plain, Albany-Corvallis area Author: Lewis, Anthony J. Taking advantage of a favorable physical system but also risking the hazards of flooding, man has long occupied flood plain land. He has attempted to adjust rivers to his needs in order to reduce flood loss, but the rising cost of flood protection accompanied by an increase in flood damage potential warrants that a course of human adjustment be undertaken on occupied flood plains. The flood plain of the Willamette River between Albany and Corvallis, Oregon provides an opportunity to study the resource use of a flood plain in a relatively youthful stage of economic development, having the physical as sets and limitations of most flood plains. By studying the physical system and changing resource utilization of this flood plain, an evaluation has been made of the present and possible future use of its resource base. Land use has evolved from a primitive stage of hunting, fishing, and gathering to intensive agricultural endeavors with some residential and commercial development. Resource utilization during the same period has changed from a dependence on the flora and fauna for food and clothing to a dependence on the soil and climate, flood protection, markets, labor, and so forth. The change has been towards a more intensive, higher valued use of the land with more sophisticated land management practices. A relatively satisfactory arrangement of land use presently exists on the Albany-Corvallis flood plain; however, present land use practices in the study area reflect a rational use of flood subjected land primarily because the pressures of industrial and commercial development have not yet been heavily felt. Residential expansion, however, has taken place at an alarming rate. Many of the human adjustments suggested by Gilbert White in his flood plain studies at the University of Chicago are applicable to a future course of orderly occupance for the Albany-Corvallis flood plain. One of the more applicable local forms of adjustment is the directing of flood plain use which involves land elevation, land use regulation, structural modifications, flood insurance, relief, and better warning systems. The construction of engineering works for flood abatement represents the traditional form of river adjustment in the Willamette Basin. The building of storage dams upstream of the study area has lowered the height of the flood crest but has also given many flood plain dwellers a feeling of false security. Channel improvements and bank revetments are the main form of river adjustment in the study area, and they help to reduce the danger of crop drowning and to control bank erosion. Close

• 8. [Article] Watershed and climate influences on flood frequency distributions in the Willamette River basin

  Problem areas identified are: The needs a) to develop curve fitting procedures to estimate flood flow distributions; b) to incorporate precipitation data into frequency analysis procedures; and c) to better ...

  Citation × Citation Citation Abstract Copy Title: Watershed and climate influences on flood frequency distributions in the Willamette River basin Author: Tolle, Timothy Victor Problem areas identified are: The needs a) to develop curve fitting procedures to estimate flood flow distributions; b) to incorporate precipitation data into frequency analysis procedures; and c) to better define flood potentials for ungauged streams. Closely related to the above, it is noted that variables commonly used to estimate flood magnitudes usually do not serve as optimum predictors. Hydrophysical variables are shown to increase the ability to estimate flood magnitudes of all frequencies within the Willamette River basin of western Oregon. The major hypotheses tested show that the traditional "regionalization" procedure is not hydrologically sound. The objective herein is to regionalize flood distributions by basin parameters. These parameters include climatic variables that are hydrologically meaningful and easy to measure or estimate. Regression equations are developed to estimate the descriptive statistics of each stream's flood distribution. The mean of the logarithms of the annual peak flows describes numerically the position of a flood frequency curve. The standard deviation of the logarithms of the peak flows describes numerically the slope of the flood frequency curve assuming a log-normal or log Pearson type III distribution. Watershed relief is the strongest estimator of flood distributions for all but the low elevation streams (R² = 56%). Relief influences within-basin climatic variability. Large flood climatology differences yield desynchronized runoff from the various source areas. Only rarely do the different elevation areas synchronize and then they yield exceptionally large peak flows. Antecedent conditions are shown to be related to flood distributions. Those basins with large year-to-year differences in antecedent conditions have steeper flood frequency curves (R² = 76%). Precipitation zones, soil permeability, and forest cover all influence antecedent conditions. Drier basins with permeable soils and forest cover have steeper flood frequency curves. Lakes and ponds act as sinks on all peak flows, and streams which flow through them have less steep flood frequency curves. In combination with watershed relief and mean annual precipitation, these three variables explain 86% of the stream-to-stream differences in the slopes of flood frequency curves in the Willamette River basin. Drainage area, terrain roughness, forest cover, and precipitation explain over 95% of the stream-to-stream differences in average flood magnitudes. Steeper slopes yield larger flood peaks as does lesser forest cover. As elevation increases, average flood magnitudes decrease, but extreme peak flows are larger. Collectively these estimation equations reduce standard errors of 50-year floods from over 40% to less than 14%. They also reduce standard errors of ten-year and 25-year floods from 46% to 15%. Title: Watershed and climate influences on flood frequency distributions in the Willamette River basin Author: Tolle, Timothy Victor Problem areas identified are: The needs a) to develop curve fitting procedures to estimate flood flow distributions; b) to incorporate precipitation data into frequency analysis procedures; and c) to better define flood potentials for ungauged streams. Closely related to the above, it is noted that variables commonly used to estimate flood magnitudes usually do not serve as optimum predictors. Hydrophysical variables are shown to increase the ability to estimate flood magnitudes of all frequencies within the Willamette River basin of western Oregon. The major hypotheses tested show that the traditional "regionalization" procedure is not hydrologically sound. The objective herein is to regionalize flood distributions by basin parameters. These parameters include climatic variables that are hydrologically meaningful and easy to measure or estimate. Regression equations are developed to estimate the descriptive statistics of each stream's flood distribution. The mean of the logarithms of the annual peak flows describes numerically the position of a flood frequency curve. The standard deviation of the logarithms of the peak flows describes numerically the slope of the flood frequency curve assuming a log-normal or log Pearson type III distribution. Watershed relief is the strongest estimator of flood distributions for all but the low elevation streams (R² = 56%). Relief influences within-basin climatic variability. Large flood climatology differences yield desynchronized runoff from the various source areas. Only rarely do the different elevation areas synchronize and then they yield exceptionally large peak flows. Antecedent conditions are shown to be related to flood distributions. Those basins with large year-to-year differences in antecedent conditions have steeper flood frequency curves (R² = 76%). Precipitation zones, soil permeability, and forest cover all influence antecedent conditions. Drier basins with permeable soils and forest cover have steeper flood frequency curves. Lakes and ponds act as sinks on all peak flows, and streams which flow through them have less steep flood frequency curves. In combination with watershed relief and mean annual precipitation, these three variables explain 86% of the stream-to-stream differences in the slopes of flood frequency curves in the Willamette River basin. Drainage area, terrain roughness, forest cover, and precipitation explain over 95% of the stream-to-stream differences in average flood magnitudes. Steeper slopes yield larger flood peaks as does lesser forest cover. As elevation increases, average flood magnitudes decrease, but extreme peak flows are larger. Collectively these estimation equations reduce standard errors of 50-year floods from over 40% to less than 14%. They also reduce standard errors of ten-year and 25-year floods from 46% to 15%. Close

• 9. [Article] Groundwater Flooding and Guerrilla Trenches : a Participatory Approach for Flood Control

  Residents in South Falls City, a small town in the foothills of Oregon's Coast Range, battle intense flooding during the rainy season. Disagreements about surface water management pit neighbor against ...

  Citation × Citation Citation Abstract Copy Title: Groundwater Flooding and Guerrilla Trenches : a Participatory Approach for Flood Control Author: Kemper, Joseph B. Residents in South Falls City, a small town in the foothills of Oregon's Coast Range, battle intense flooding during the rainy season. Disagreements about surface water management pit neighbor against neighbor, but preliminary evidence suggests that groundwater flooding is an underlying cause. OSU researchers pair the emerging literature on groundwater flooding with a collaborative learning framework to manage conflict and characterize the region's hydrology. This joint fact-finding mission seeks to determine if (1) the groundwater contributes to the apparent stormwater flooding, and (2) if a Coupled Human and Naturals Systems (CHANS) approach to groundwater control can alleviate both flooding and conflict. A Falls City/OSU partnership provide funds for a monitoring well to measure depth of the alluvial aquifer, produce water table hydrographs, and determine aquifer properties. LIDAR based surface elevation data help resolve surface-groundwater interactions. Results show that groundwater plays an active role in the surface flooding. AquiferWin32 software provided by Dr. Steve Taylor from Western Oregon is used to evaluate potential mitigation strategies including ditch modifications, drain tiles, land cover changes, and dewatering wells. Engineering measures and stakeholder suggestions are synthesized to create mitigation recommendations for South Falls City. South Falls City joins a growing body of media reports and literature on groundwater flooding. A common theme emphasizes the importance of cooperative land and aquifer management in flooding regions, particularly in light of predicted precipitation increases with global climate change. Title: Groundwater Flooding and Guerrilla Trenches : a Participatory Approach for Flood Control Author: Kemper, Joseph B. Residents in South Falls City, a small town in the foothills of Oregon's Coast Range, battle intense flooding during the rainy season. Disagreements about surface water management pit neighbor against neighbor, but preliminary evidence suggests that groundwater flooding is an underlying cause. OSU researchers pair the emerging literature on groundwater flooding with a collaborative learning framework to manage conflict and characterize the region's hydrology. This joint fact-finding mission seeks to determine if (1) the groundwater contributes to the apparent stormwater flooding, and (2) if a Coupled Human and Naturals Systems (CHANS) approach to groundwater control can alleviate both flooding and conflict. A Falls City/OSU partnership provide funds for a monitoring well to measure depth of the alluvial aquifer, produce water table hydrographs, and determine aquifer properties. LIDAR based surface elevation data help resolve surface-groundwater interactions. Results show that groundwater plays an active role in the surface flooding. AquiferWin32 software provided by Dr. Steve Taylor from Western Oregon is used to evaluate potential mitigation strategies including ditch modifications, drain tiles, land cover changes, and dewatering wells. Engineering measures and stakeholder suggestions are synthesized to create mitigation recommendations for South Falls City. South Falls City joins a growing body of media reports and literature on groundwater flooding. A common theme emphasizes the importance of cooperative land and aquifer management in flooding regions, particularly in light of predicted precipitation increases with global climate change. Close

• 10. [Article] A Dynamic Framework for Intelligent Control of River Flooding - A Case Study

  This is an author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by the American Society of Civil Engineers and can be found at: http://ascelibrary...

  Citation × Citation Citation Abstract Copy Title: A Dynamic Framework for Intelligent Control of River Flooding - A Case Study Author: Leon, Arturo S., Valverde, Rachelle, Sridhar, Venkataramana, Kanashiro, Elizabeth A. This is an author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by the American Society of Civil Engineers and can be found at: http://ascelibrary.org/journal/jwrmd5. Title: A Dynamic Framework for Intelligent Control of River Flooding - A Case Study Author: Leon, Arturo S., Valverde, Rachelle, Sridhar, Venkataramana, Kanashiro, Elizabeth A. This is an author's peer-reviewed final manuscript, as accepted by the publisher. The published article is copyrighted by the American Society of Civil Engineers and can be found at: http://ascelibrary.org/journal/jwrmd5. Close