A repository of hydrology and engineering publications, reports, and tools developed by Steven Yochum and his collaborators is provided. (See the About page for a list of collaborators.) Use of these materials needs to be credited to the authors, developers, and organizations.
Mark Twain National Forest Climate Change Impact Assessment and Vulnerability Framework for Recreation
Shannon, P.D., Brandt, L.A., Peters, M.P., Yochum, S.E., Gubernick, R., Ewing, R. (2025). Mark Twain National Forest Climate Change Impact Assessment and Vulnerability Framework for Recreation, U.S. Forest Service, General Technical Report NRS-236.
EXECUTIVE SUMMARY: This assessment evaluates how changes in climate, hydrology, and ecosystems influence the overall vulnerability of the Mark Twain National Forest’s recreation opportunities and related infrastructure under a range of modeled projected future climates. The assessment summarizes current conditions for the national forest and key stressors that could be exacerbated by climatic change and identifies past and projected trends in climate. These projections, combined with resource specialists’ local knowledge and expertise, can be used to identify the factors that contribute to the vulnerability of forest ecosystems, local recreation sites, and infrastructure to climate impacts. A vulnerability framework developed to help address these impacts was applied to the national forest’s Red Bluff recreation site in a collaborative workshop with recreation, hydrology, and other resource specialists. This framework can help managers identify climate-related risks and potential vulnerability for sites and recreation assets in support of recreation management and climate adaptation planning.
Virginia Creeper Trail Flooding from Hurricane Helene: Hydrology Analyses for Reconstruction
Yochum, S.E. (2025). Virginia Creeper Trail Flooding from Hurricane Helene: Hydrology Analyses for Reconstruction. U.S. Forest Service, National Stream and Aquatic Ecology Center, Project Report for the Jefferson National Forest, July 16, 2025.
SUMMARY: Powerful remnants of Hurricane Helene impacted the Southern Appalachians in September 2024, with up to 24 inches of rain inducing large-scale flooding. The popular rails-to-trails Virginia Creeper Trail was heavily impacted by flooding from Whitetop Laurel Creek, with 18 bridges (trestles) severely damaged or destroyed, and portions of the embankment eroded and nonfunctional. Hurricane Helene induced flooding in Whitetop Laurel Creek that was unexpectedly large. High water marks indicate that this event exceeded the size of floods that are expected and most infrastructure is designed to safely pass. In some places, the flooding was extreme. Using a preliminary version of the six-level (Fl-1 to Fl-6) Flood Severity Scale, this event was at the Fl-4 and Fl-5 magnitudes. Generally, this portion of the Southern Appalachians is highly susceptible to flooding from hurricanes, with the most substantial recorded event being induced from a hurricane that came ashore at Beaufort, South Carolina on August 11, 1940. Previously, a powerful flood event was induced across the southern Blue Ridge Mountains from hurricane remnants in July of 1916. Floods are inherently large in this area, at the 78th percentile compared to all of the United States. This is quantified and illustrated within the Flood Potential Portal (https://floodpotential.erams.com/). On average floods are twice as large in this portion of the Blue Ridge than in the neighboring portion of the Valley and Ridge physiographic province. However, portions of the Blue Ridge to the South experience floods 3 times larger, on average; this area was most dramatically impacted by Helene flooding. Trends in magnitudes of moderate- and bankfull-scale floods are increasing in this area, but no increasing trends in large floods are currently being observed. Recommendations for design flood discharges at the 100-year (1% chance of occurrence) scale are quantified for the Virginia Creeper Trail reconstruction based on analyses performed in the Flood Potential Portal Watershed Analysis module. Design flood discharges are the size of large floods we can expect, and should plan and design for.
Flood Potential Portal: A web tool for understanding flood variability and predicting peak discharges
Yochum, S. E., Wible, T., Korsa, M., Ghanbari, M., & Arabi, M. (2024). Flood Potential Portal: A web tool for understanding flood variability and predicting peak discharges. River Research and Applications, 1–13.
ABSTRACT: The Flood Potential Portal (https://floodpotential.erams.com/) has been developed for the contiguous United States, as a practitioner-focused tool that uses observational data (streamgages) to enhance understanding of how floods vary in space and time, and assist users in making more informed peak discharge predictions for infrastructure design and floodplain management. This capability is presented through several modules. The Mapping module provides tools to explore variability using multiple indices, and provides detailed information, figures, and algorithms describing and comparing flooding characteristics. The Cross-Section Analysis module allows users to cut regional-scale sections to interpret the role of topography in driving flood variability. The Watershed Analysis module provides multiple methods for quantifying expected peak discharge magnitudes and flood frequency relationships at user-selected locations, including the integration of observed trends in flood magnitudes due to climate change and other sources of nonstationarity into decision making. The Streamgage Analysis module performs streamgage flood-frequency analyses. These modules are based in part on the flood potential method, through the use of 207 zones of similar flood response defined using more than 8200 streamgages with watershed areas <10,000 km2. Regression models that define each zone had high explained variance (average R2 = 0.93). An example is provided to illustrate use of the Flood Potential Portal for the design of a hypothetical bridge replacement.
Flood Potential Portal: User Manual
Yochum, S.E., Wible, T., Ghanbari, M., and Millonig, S. (20**). Flood Potential Portal: User Manual. One Water Solutions Institute and the National Stream and Aquatic Ecology Center, Colorado State University and the U.S. Forest Service, Version *.*.
SUMMARY: Riverine floods are a leading environmental threat to life, infrastructure, and property. Climate change is likely changing these threats in some areas. To maximize infrastructure resilience and knowledge used for stream and riparian ecosystem management, it is essential to develop enhanced understanding of riverine flood hazards and make this knowledge readily available to hydrologic professionals, to be incorporated into decision making. The Flood Potential Portal (FPP) was developed to assist practitioners with developing such enhanced understanding, using both traditional and new techniques that leverage the power of more than a century of streamgaging efforts in the United States. The U.S. Forest Service’s National Stream and Aquatic Ecology Center (NSAEC) collaborated with researchers and staff at Colorado State University’s One Water Solutions Institute (OWSI) to develop a decision support system that presents the results of the flood potential method (Yochum et al., 2019) alongside the results of traditional riverine flood analysis methodologies. The intent is to help professionals understand how floods vary in space and time (from continental to catchment scales), to explore how floods differ across regions and predict flood magnitudes at points of interest using multiple methodologies. Additionally, the stationarity assumption for streamgage analyses is tested and adjustments applied where trends in flood magnitudes are detected, with additional trend testing for flood frequency and flashiness performed; the FPP provides tools to test and account for observed changes in large floods due to climate change and other non-stationarity mechanisms.
Working with wood in rivers in the Western United States
Ockelford et al. (2024). Working with wood in rivers in the Western United States. River Research and Applications 1-16.
Recognition of the important physical and ecological roles played by large wood in channels and on floodplains has grown substantially during recent decades. Although large wood continues to be routinely removed from many river corridors worldwide, the practice of wood reintroduction has spread across the United States, the United Kingdom and western Europe, Australia, and New Zealand. The state-of-science regarding working with wood in rivers was discussed during a workshop held in Colorado, USA, in September 2022 with 40 participants who are scientists and practitioners from across the USA, UK, Europe, and Japan. The objectives of this paper are to present the findings from the workshop; summarize two case studies of wood in river restoration in the western United States; and provide suggestions for advancing the practice of wood in river management. We summarize the workshop results based on participant judgements and recommendations with respect to: (i) limitations and key barriers to using wood, which reflect perceptions and practicalities; (ii) gaps in the use of large wood in river management; (iii) scenarios in which wood is generally used effectively; and (iv) scenarios in which wood is generally not used effectively. The case studies illustrate the importance of the local geomorphic context, the configuration complexity of the wood, and the potential for modification of river corridor morphology to enhance desired benefits. Moving forward, we stress the importance of collaboration across disciplines and across communities of research scientists, practitioners, regulators, and potential stakeholders; accounting for stakeholder perceptions of the use of large wood; and increasing non-scientist access to the latest state-of-science knowledge.
Flood Variability in the Western United States: Overview and Examples
Yochum, S.E., Levinson, D.H. (2023). Flood Variability in the Western United States: Overview and Examples. SEDHYD-2023 Conference Proceedings Article, May 8-12, St. Louis, Missouri, USA.
ABSTRACT: Greater understanding of riverine flood hazards, and how they vary in space and time, is needed to protect lives, property, and infrastructure. To this end, the variability of floods within the wide-ranging climatological conditions of the contiguous United States west of the Mississippi River were assessed using the flood potential method. This procedure fosters the comparison, visualization, and communication of flood hazards, for highlighting the status of flooding given observational data from the nation’s streamgaging network, and how floods are changing due to such non-stationarity mechanisms as climate change. Within the study area, 117 zones of similar flood response were delineated using 4621 streamgaged watersheds with areas <3860 mi2. Explained variances of the regressions were high, with an average R2 = 0.91. The central tendency and variability of flood magnitudes experienced within each zone is an intrinsic characteristic, with exceedingly large floods systematically defined and ranked as extreme. The highest flood potential occurs in the southern Midwest and Texas, and along the West Coast, with the lowest flood potential in the Great Basin, Rocky Mountains, and northern Midwest. Extreme floods are not becoming larger or more frequent. However, some zonal areas (29%) are currently experiencing increasing trends in the magnitude or frequency of large floods, though magnitudes vary considerably more in space than in time. Results are presented through the Flood Potential Portal, a decision support system to explore flood variability at a full range of scales and predict flood discharge magnitudes using multiple methodologies. Examples are provided, including for the Yellowstone region floods of 2022 and Oroville Dam flood of 2017, to provide applications that use the methodology for enhancing knowledge of flood hazards.
Guidance for Stream Restoration
Yochum, S.E., Reynolds, L.V. (2020). Guidance for Stream Restoration. U.S. Department of Agriculture, Forest Service; U.S. Department of Interior, Bureau of Land Management; Forest Service National Stream & Aquatic Ecology Center Technical Note TN-102.5. Fort Collins, Colorado.
ABSTRACT: Stream restoration practitioners and researchers have devoted a great deal of effort in recent decades to developing extensive guidance for stream restoration. The available resources are diverse, reflecting the wide ranging approaches used and expertise required to develop effective stream restoration projects. To help practitioners in sorting through the extensive amount of available information, this technical note has been developed to provide a guide to the available guidance. The document structure is primarily a series of short literature reviews followed by a hyperlinked reference list for readers to find more information on each topic. The primary topics incorporated into this guidance include general methods, an overview of stream processes and restoration, case studies, data compilation, preliminary assessments, and field data collection. Analysis methods and tools, and planning and design guidance for specific restoration features are also provided. This technical note is a bibliographic repository of information available to assist professionals with the process of planning, analyzing, and designing stream restoration projects. It is updated periodically.
Methods for Assessing Expected Flood Potential and Variability: Southern Rocky Mountains Region
Yochum, S. E., Scott, J. A., & Levinson, D. H. (2019). Methods for assessing expected flood potential and variability: Southern Rocky Mountains region. Water Resources Research, 55, 6392–6416.
ABSTRACT: Enhanced understanding of flood hazards, and how they vary across regions and continents, is needed to help protect lives and develop more resilient communities. Using the greater Southern Rocky Mountains region as a study area, a novel methodology was developed to predict, rank, and communicate expected flood magnitudes across similar responding areas (zones). Using 463 streamgages, up to 93% of the variance was explained by regression models developed for 11 derived zones. These regressions define the expected flood potential of each zone, a term introduced to assist practitioners, policy makers, and the public in understanding what flood magnitudes can be expected given the maximum recorded streamgage floods in nearby watersheds. Discharges above the 90% prediction limit, the maximum likely flood potential, are considered extreme; departure above this limit denotes the degree of extremity. The seasonality of the largest 5% floods varied substantially between zones, with the greatest frequency in July, August, and September in some zones (due to the North American monsoon) and May and June in other zones (due to snowmelt and rainfall). Using the lowest flood potential zone as an index area, flood potential and hazard indices were developed for comparing flood hazards across broad regions. The largest floods occur in the southern portion of the eastern slopes of the Southern Rocky Mountains and the adjacent Great Plains, with these events being 15 times larger than floods experienced in central Colorado and New Mexico mountain valleys, on average for a given watershed area.
Managing for large wood and beaver dams in stream corridors
Wohl, E.; Scott, D.N.; Yochum, S.E. (2019). Managing for large wood and beaver dams in stream corridors. Gen. Tech. Rep. 404. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. 137 p
ABSTRACT: Large wood and beaver dams are fundamental components of forested stream ecosystems but can also create hazards. We present guidelines for identifying stream segments that maximize environmental benefits while minimizing hazards. We focus on lesser gradient
stream segments, although wood can be ecologically beneficial anywhere in a river network. Stream segments can be targeted for field-based evaluation using checklists for scenarios of either retention or reintroduction for logjams or beaver dams. We also present the Wood Jam Dynamics Database and Assessment Model, which incorporates a machine-learning-based statistical analysis to predict wood jam dynamics and provides a standardized survey protocol for wood jams.
Wood Jam Dynamics Database and Assessment Model (WooDDAM): A framework to measure and understand wood jam characteristics and dynamics
Scott, D.N., Wohl, E., Yochum, S.E. (2019). Wood Jam Dynamics Database and Assessment Model (WooDDAM): A framework to measure and understand wood jam characteristics and dynamics. River Research and Applications 35, 1466-1477.
ABSTRACT: Wood jams in rivers and on floodplains play an essential role in shaping valley bottoms, and their dynamics regulate the ecology and morphology of river systems. Although wood jams are commonly used to regulate fluvial geomorphic processes and provide habitat, our inability to predict how wood jams change through time hampers wood restoration efforts. We present the Wood Jam Dynamics Database and Assessment Model (WooDDAM) to improve understanding and management of natural and anthropogenic wood jams in rivers. WooDDAM is composed of a field data collection protocol, an open database of wood jam characteristics and dynamics, machine learning statistical models for predicting wood jam dynamics during high flows, and an online user interface to facilitate collaborative data collection and use. Here, we provide the background and guidance necessary to utilize WooDDAM to make predictions of and contribute to the database describing wood jam dynamics. We present tests of interoperator variability to justify database variable selection. To refine model predictions and improve predictive power, we encourage users to follow simple resurvey procedures and submit observations of wood jam dynamics. WooDDAM provides a management and monitoring tool for the retention or reintroduction of wood jams in rivers and facilitates further research into the interactions between wood jam dynamics and fluvial or ecological processes.
Flood Potential in the Southern Rocky Mountains Region and Beyond
Yochum, S.E. (2019). Flood Potential in the Southern Rocky Mountains Region and Beyond. SEDHYD-2019 Conference Proceedings, June 24-28, Reno, Nevada, USA.
ABSTRACT: Understanding of the expected magnitudes and spatial variability of floods is essential for managing stream corridors. Utilizing the greater Southern Rocky Mountains region, a new method was developed to predict expected flood magnitudes and quantify spatial variability. In a variation of the envelope curve method, regressions of record peak discharges at long-term streamgages were used to predict the expected flood potential across zones of similar flood response and provide a framework for consistent comparison between zones through a flood potential index. Floods varied substantially, with the southern portion of Eastern Slopes and Great Plains zone experiencing floods, on average for a given watershed area, 15 times greater than an adjacent orographic-sheltered zone (mountain valleys of central Colorado and Northern New Mexico). The method facilitates the use of paleoflood data to extend predictions and provides a systematic approach for identifying extreme floods through comparison with large floods experienced by all streamgages within each zone. A variability index was developed to quantify within-zone flood variability and the flood potential index was combined with a flashiness index to yield a flood hazard index. Preliminary analyses performed in Texas, Missouri and Arkansas, northern Maine, northern California, and Puerto Rico indicate the method may have wide applicability. By leveraging data collected at streamgages in similar-responding nearby watersheds, these results can be used to predict expected large flood magnitudes at ungaged and insufficiently gaged locations, as well as for checking the results of statistical distributions at streamgaged locations, and for comparing flood risks across broad geographic extents.
Flow Resistance Coefficient Selection in Natural Channels: A Spreadsheet Tool
Yochum, S.E. (2018). Flow Resistance Coefficient Selection in Natural Channels: A Spreadsheet Tool. USDA Forest Service, National Stream and Aquatic Ecology Center, Technical Summary Report TS-103.2.
SUMMARY: A spreadsheet tool has been developed by the U.S. Forest Service National Stream and Aquatic Ecology Center to assist practitioners with selecting flow resistance coefficients (Manning’s n) for stream channels. Such coefficients are needed to quantify roughness for hydraulic modeling, stream assessments, stream restoration design, geomorphic analyses, and ecological studies.
Wet Canyon: Condition and Rehabilitation Potential
Yochum, S.E. (2018). Wet Canyon: Condition and Rehabilitation Potential. U.S. Forest Service, National Stream and Aquatic Ecology Center, Project Report for the Coronado National Forest, April 17, 2018.
SUMMARY: Wet Canyon at Arizona Rt. 366 was assessed for deficient conditions and rehabilitation needs after flood disturbances induced by the 2017 Frye Fire. The high and moderate soil burn severity experienced within this watershed has caused debris flows and debris floods that blocked a historic masonry-arch culvert, inducing backwater flooding that forced flow and debris over AZ-366. Emergency measures to remove the culvert and redistribute or remove the sediment and wood material alleviated a portion of the problem, but substantial issues remain including conditions unintentionally created by the emergency measures. At a minimum, over the short term (before July 2018) it is recommended that the old parking lot for the picnic area as well as the north “stump” of the masonry culvert be excavated to provide conveyance for floodplain flow captured by the parking area. This is necessary to insure safe passage of flows through the bridge rather than over the AZ-366 roadway. Additionally over the short term, if funding is available additional work that should be considered includes: earth movement to adjust the floodplain form, introduction of boulders (and large wood) to the machinery-impacted channel, work to reduce compaction of the machinery-disturbed areas, adding soil amendments to the floodplain, seeding of the floodplain, and monitoring for weed recruitment and subsequent mitigation when needed. Additional actions recommended for consideration over the medium term include (in a few years, after peak flows from the wildfire have reduced) adding additional soil amendments and an extensive quantity of native plantings.
Longitudinal variability of geomorphic response to floods
Sholtes, J.S., Yochum, S.E., Scott, J.A., Bledsoe, B.P. (2018). Longitudinal variability of geomorphic response to floods. Earth Surface Processes and Landforms.
ABSTRACT: Morphodynamic response of channels and floodplains to flooding reflects interactions of erosive and resistive forces with sediment transport capacity and supply at multiple scales. Monotonic relationships between reach-scale response to floods with independent variables such as flood stream power and channel confinement can be confounded by longitudinal variations in these variables at longer scales. In these cases, channel response depends on both local and upstream drivers. Using high resolution pre- and post-flood digital elevation models, we calculate reach-scale (0.5 to 1 km) and segment scale (10 km) longitudinal variations in channel widening and sediment balance. We relate these responses to longitudinal variations of unit stream power and channel confinement for selected streams impacted by the 2013 Colorado Front Range regional flood event. These streams transition from steep and relatively confined in the canyons of the foothills to less steep and unconfined on the high plains. The channel widening response is more closely linked with reach scale gradients in unit stream power: abrupt widening typically occurred within reaches where a large drop in unit stream power occurred relative to upstream. Sediment balance followed segment scale trends in unit stream power, exhibiting a net erosional trend within the foothills that switches to a net depositional trend within the transition to the plains. These findings indicate that unit stream power gradients mediate channel response at reach to segment scales. Predictive modeling of stream response to floods and fluvial hazards assessments that only consider absolute values of reach-scale stream power may under-estimate fluvial hazards in some settings by ignoring unit stream power gradients.
Tularosa River at NSFR-233: Site Visit and Recommendations
Yochum, S.E. (2018). Tularosa River at NSFR-233: Site Visit and Recommendations. U.S. Forest Service, National Stream and Aquatic Ecology Center, Project Report for the Gila National Forest, October 5, 2018.
The National Forest System Road (NFSR) 233 crossing of the Tularosa River was assessed. Primary resource concerns at this crossing include wetland loss, lack of aquatic organism passage, and the structural stability of the crossing, with key impacted species being the loach minnow and the Chiricahua leopard frog (critical habitat upstream and downstream of the crossing), and the narrow-headed gartersnake (proposed critical habitat). It is recommended that three actions for this crossing be considered, specifically: 1. the removal of the concrete apron added in 2009; 2. restoration of the downstream channel; and 3. the addition of a shallow and wide concrete conduit at the crossing. Scour downstream of the crossing and apron is preventing aquatic organism passage, with this scour likely made more severe by the apron – removal is warranted. Restoration of the downstream channel and floodplain would consist of filling the high unit stream power channel with borrow material from a suitable local source, to eliminate the knickpoint at the downstream limit of the crossing, provide aquatic organism passage, reconnect the channel with its floodplain (reducing unit stream power), and raise groundwater levels to reestablish riparian conditions and protect the downstream wetlands. Additionally, a shallow and wide concrete conduit at the crossing should be considered, to aid with aquatic organism passage while maintaining the upstream wetland. This may require reconstruction of the crossing, with a new alignment that is perpendicular to the valley profile preferred.
Stream power framework for predicting geomorphic change: The 2013 Colorado Front Range flood
Yochum, S.E., Sholtes, J.S., Scott, J.A., Bledsoe, B.P. (2017). Stream power framework for predicting geomorphic change: The 2013 Colorado Front Range flood. Geomorphology 292, 178-192.
ABSTRACT: The Colorado Front Range flood of September 2013 induced a diverse range of geomorphic changes along numerous stream corridors, providing an opportunity to assess responses to a large flood in a semiarid landscape. We defined six classes of geomorphic change related to peak unit stream power and valley confinement for 531 stream reaches over 226 km, spanning a gradient of channel scales and slope. Geomorphic change was generally driven by erosion of channel margins in confined reaches and by a combination of deposition and erosion in unconfined reaches. The magnitude of geomorphic change typically increased with unit stream power (ω), with greater responses observed in unconfined channels. Cumulative logit modeling indicated that total stream power or unit stream power, unit stream power gradient, and valley confinement are significant predictors of geomorphic response for this flood event. Based on this dataset, thresholds for geomorphic adjustment were defined. For channel slopes <3%, we noted a credible potential for substantial channel widening with ω > 230W/m2 (16 lb/ft-s; at least 10% of the investigated sites experienced substantial channel widening) and a credible potential for avulsions, braiding, and loss of adjacent road embankments associated with ω > 480 W/m2 (33 lb/ft-s; at least 10% of the investigated sites experienced such geomorphic change). Infrequent to numerous eroded banks were very likely with ω > 700 W/m2 (48 lb/ft-s), with substantial channel widening or major geomorphic change shifting from credible to likely. Importantly, in reaches where there were large reductions in ω as the valley form shifted from confined to relatively unconfined, large amounts of deposition-induced, reach-scale geomorphic change occurred in some locations at relatively lowω. Additionally, alluvial channels with slopes > 3% had greater resistance to geomorphic change, likely caused by armoring by larger bed material and increased flow resistance from enhanced bedforms. Finally, we describe how these results can potentially be used by practitioners for assessing the risk of geomorphic change when evaluating current or planned conditions.
Rio San Antonio: Stream Condition Restoration Potential
Yochum, S.E. (2017). Rio San Antonio: Stream Condition Restoration Potential. U.S. Forest Service, National Stream and Aquatic Ecology Center, Project Report for the Carson National Forest, December 13, 2017.
SUMMARY: Three segments of the Rio San Antonio and tributary streams were assessed for deficient conditions and the need for restoration. Current and historic conditions were evaluated and restoration alternatives were developed. Flow frequency relationships are provided at key points, for use in restoration planning and design. Recommendations for action and data needs are presented. Generally, Canada Tio Grande has intermittent deficiencies, with insufficient riparian cover in places and a few short reaches where restoration may be advisable to address incision. Management changes and vegetation plantings, as well as possibly isolated channel and floodplain restoration and beaver dam analogs, should be considered. The lower visited reach of Rio San Antonio is generally in fair to good condition, with active beaver activity and relatively dense riparian vegetation in many areas. Prior incision and, in 1962, braided conditions has generally stabilized at a lower grade with stands of riparian vegetation. Some reaches of overly-widened channel and bank instability were noted. Portions of this reach have extensive beaver activity, which can slowly recover the incision with dam building and beaver meadow development. Management changes as well as isolated channel and floodplain restoration (and beaver dam analogs) should be considered for this reach. The upper reach of the Rio San Antonio is generally in fair condition, with many portions of the reach incised. Braided reaches evident in 1962 have since stabilized but woody vegetation is highly impaired from browsing and grazing activities. The continuation of current management will likely result in continued impairment, with poor cover and elevated water temperatures. Management changes and riparian plantings, combined with structural headcut arrest, is at least needed. Beaver dam analogs can also be considered. Full restoration of the channel at the former grade, reestablishing pre-disturbance groundwater table elevations and providing the best conditions for riparian vegetation, can be done with reasonable effort at this stage and should also be considered. To meet objectives, fish barrier construction and non-native fish elimination will likely be needed before fully restoring this reach.
Pickel Meadow: Stream Condition and Restoration Potential
Yochum, S.E., McCann, J. (2017). Pickel Meadow: Stream Condition and Restoration Potential. U.S. Forest Service, National Stream and Aquatic Ecology Center, Project Report for the Humboldt-Toiyabe National Forests, June 23, 2017.
SUMMARY: Pickel Meadow and the West Walker River are impaired by three general circumstances: (1) an alluvial fan at the upstream limit of the meadow which is constrained by a parking lot, terrace features, and a primitive road, with a resulting disconnection of the uppermost, widest, and potentially most productive portion of the meadow; (2) incision within the upper portion of the potential restoration extent, which has likely lowered the groundwater table elevations in the meadow and reduced productivity; and (3) infrequent deep pools and cover for fish. The meadow disconnection by the parking lot, road, and terrace features has resulted in a loss of flow, sediment, and large wood and other organics from the West Walker River. The incision likely occurred some time ago since a wide and hydraulically-effective floodplain has had an opportunity to develop at a lower elevation but this incision has likely resulted in water table levels during low flow to be 6 or 7 feet below certain portions of the meadow surface along the West Walker River. Restoration with multi-thread channels, with vegetative plantingss recommended from the canyon mouth to where the West Walker River becomes semi-confined by high terraces. This alluvial fan restoration would best match the goals of the stakeholders. For the remainder (majority) of the 4.8 mile extent, it is recommended that fish habitat enhancement features be installed.
logPearson Frequency Analysis Spreadsheet for Analyses of Streamgage Records
Yochum, S.E. (2017). logPearson Frequency Analysis Spreadsheet for Analyses of Streamgage Records. U.S. Forest Service National Stream and Aquatic Ecology Center technical summary report, TS-101.2
SUMMARY: Projects along stream corridors require flow frequency estimates. Flow discharge estimates for the 1.25-year (80% chance of occurrence) through 100-year (1% chance of occurrence) discharges are used for projects ranging from stream restoration to culvert and bridge replacements. Where sufficient streamgage data are available, the likely best method for developing flow frequency relationships are from statistical analyses of streamgage data. The standard procedure for developing these estimates use the logPearson frequency analysis, as detailed in Bulletin 17B (Interagency Advisory Committee on Water Data 1982). The addition of the expected moments algorithm (EMA; Cohn et al. 2007; Paretti et al. 2014) and a few other modifications to the Bulletin 17B procedure have been recommended, though have not yet been incorporated into a Bulletin 17C and formally adopted. This spreadsheet tool was developed to implement the analysis procedures detailed in Bulletin 17B,
Armstrong Creek Restoration: Assessment
Yochum, S.E., Merritt, D. (2016). Armstrong Creek Restoration: Assessment. U.S. Forest Service, National Stream and Aquatic Ecology Center, Project Report for the Coronado National Forest, August 16, 2016.
SUMMARY: Stream restoration efforts have been implemented on Armstrong Creek in California Park, on the Routt National Forest. A site visit was performed to observe the conditions of the restoration projects constructed in Armstrong Creek. Specifically, projects that were constructed in 2013 (lower Armstrong Creek) and 2015 (upper Armstrong Creek) were observed. Generally, lower Armstrong Creek was in good condition, with several fish species observed (speckled dace, sculpin, and mountain sucker) and cutthroat trout abundance reportedly increasing in this restoration reach. The riparian vegetation was dense and well-established. The sedge plugs, sedge mats and willow plantings appear to have been very successful. However, an abundance of what appeared to be smooth brome and Canada thistle was observed. The upper subreach of upper Armstrong Creek was observed to be generally in good condition. However, the restoration performed on the lower subreach of upper Armstrong Creek is faring more poorly and we are concerned about the potential for recapture of the stream channel through the previously-incised but now ponded areas. With respect to this subreach, we recommend rebuilding of rock grade control structures, regrading and vegetating the pond areas, and repair of other noted geomorphic adjustments. Additionally, spot application of glyphosate is recommended for control of smooth brome and Canada thistle.
First Creek: Stream Restoration Assessment
Yochum, S.E., Merritt, D. (2016). First Creek: Stream Restoration Assessment. U.S. Forest Service, National Stream and Aquatic Ecology Center, Project Report for the Routt National Forest, September 15, 2016.
SUMMARY: The incision of First Creek, and the resulting perspective that restoration is needed, is due to a drop in the base level of Elkhead Creek and local meander cutoffs increasing slope, unit stream power and shear stress, and sediment transport capacity. This incision is likely due to historical and current grazing practices and browsing activities causing poor streambank vegetative condition. This is increasing the rate of bank erosion, with decreased root binding and lower hydraulic roughness. The lower roughness and flow resistance leads to higher velocities, higher momentum transfer to the channel banks, and larger forces acting on the weaker cut banks. This affect is exasperated by tight meander bends that reduce the area over which momentum transfer acts upon the bank within a channel bend. The resulting First Creek channel is Channel Evolution Model stages 3 and 4, with some reaches showing substantial floodplain width at the lower base level (stage 4) and other reaches showing overly-narrowed, channelized reaches (stage 3) that are actively eroding cutbanks. If left to evolutionary processes, the incised First Creek channel is expected to continue to develop widened floodplains during high flow events until a floodplain width is developed to sufficiently reduce unit stream power. However, additional disturbances may result in new rounds of incision and continued impaired conditions. Riparian management plus local streambank protection is recommended for implementation due to its lower risk for impairing existing ecological resources, specifically the oxbow-associated wetlands.
Living Streambanks: A Manual of Bioengineering Treatments for Colorado Streams
Giordanengo, J.H., Mandel, R.H., Spitz, W.J., Bossler, M.C., Blazewicz, M.J., Yochum, S.E., Jagt, K.R., LaBarre, W.J., Gurnee, G.E., Humphries, R., Uhing, K.T. (2016). Living Streambanks: A Manual of Bioengineering Treatments for Colorado Streams. Colorado Water Conservation Board.
SUMMARY: The 2013 Front Range Floods were highly detrimental to Colorado, impacting human life, infrastructure, and water quality. Furthermore, the flood caused historic levels of damage to stream channels, floodplains, and riparian areas. To assist the multiple communities and watersheds impacted by the 2013 disaster, the Colorado Department of Natural Resources, Colorado Water Conservation Board provided funding through Rocky Mountain Flycasters (a chapter of Colorado Trout Unlimited) for the creation of this bioengineering manual. Bioengineering practices provide resiliency for streambanks, enhance wildlife habitat, enhance organic matter inputs to streams, improve water quality, increase floodplain roughness, and heighten landscape aesthetics so important to countless residents, visitors, and businesses. Accordingly, the authors have created the following manuscript to: provide guidelines for a comprehensive bioengineering strategy; incorporate design elements that impart site stability and resilience; include project recommendations that minimize risk during periods of vulnerability; increase understanding of how to properly apply bioengineering and revegetation techniques; provide background resources on the combined forces of water and gravity as they pertain to bioengineered structures; and create a searchable Revegetation Matrix for the primary native restoration species useful for flood recovery and other riparian areas throughout Colorado. As the development of this manual is an iterative process, the authors thank you for taking the time to review our recommendations and welcome your feedback on how collectively we can better increase our knowledge and understanding of these practices as a restoration and engineering community.
Upper Milk Creek: Stream Condition and Restoration Potential
Yochum, S.E. (2016). Upper Milk Creek: Stream Condition and Restoration Potential. U.S. Forest Service, National Stream and Aquatic Ecology Center, Project Report for the White River National Forest, November 30, 2016.
SUMMARY: Milk Creek, a tributary to the Yampa River between Meeker and Craig, Colorado, is home to a core conservation population of Colorado River cutthroat trout, a subspecies conserved under an agreement that includes the Forest Service. This population of cutthroat trout is uncommon – genetic testing indicates that the population is 99% pure Colorado River cutthroat trout, with 1% introgression from other subspecies of cutthroat trout. This is a valuable population of native trout, with potentially the highest genetic purity in the Yampa River basin. A primary impairment of Milk Creek that is likely inhibiting population increase is excessive summer stream temperatures on the downstream reaches. A reach on upper Milk Creek, on the White River National Forest, was visited to assess its general condition and develop restoration strategies, if needed. The primary impairments to this reach include: channel incision from past disturbances; high rates of streambank erosion and meander migration, which have potential for cutting off meanders, decreasing sinuosity, and increasing local channel slope and channel incision; overly-wide channel width in some locations; lack of tree canopy for shading, for reducing solar heating during low flow; and a lack of instream large wood due to firewood removal for hunting camps. Considering that this Colorado River cutthroat trout population is a core conservation population, and the situation of excessive downstream stream temperatures, a high rate of warming within this reach, poor canopy cover, and the direct removal of instream large wood for hunting camps, introduction of large instream wood, plus vegetation plantings and management is recommended for implementation.
Mogollon Rim Stream Instability Assessments
Yochum, S.E. (2016). Mogollon Rim Stream Instability Assessments. U.S. Forest Service, National Stream and Aquatic Ecology Center, Project Report for the Coconino National Forest, October 25, 2016.
SUMMARY: Four impaired stream reaches were visited on the Mogollon Rim ranger district, specifically Buck Springs, Houston Draw, Dick Hart Draw, and Willow Valley. All of the reaches but Willow Valley have not had livestock grazing for about 10 years but do experience large impacts from elk grazing and browsing. These channels have been disturbed with historic livestock grazing and current elk grazing and browsing, resulting in incision of varying depths and spatial extent. The riparian vegetation disturbance has resulted in channel bank and valley bottom instability, from the lack of root density and depth providing mechanical resistance to erosive flow. Local incision leads to deepening and widening of channels and floodplain disconnections, with increased unit stream power and shear stress. Low amounts of flow resistance also increase the erosion and incision potential of the stream reaches. Generally, woody vegetation, large in-channel wood, bedforms, and sinuosity are the primary sources of flow resistance in these channel types. Restoration and rehabilitation options and recommendations are provided for each of the four visited streams. Expansion of the use of existing methods for arresting headcuts is one option. However, these structures will need periodic inspection and potential maintenance in perpetuity, due to the rapid drop in longitudinal profile at the stabilized headcuts being likely locations of future incision, especially during large flood events. Additionally, they maintain the current lower grade and impaired conditions (compared to pre-disturbance conditions) with constrained riparian hydrologic and vegetative conditions. An alternative approach is to perform full meadow restorations, which is preferred where possible given the availability of sufficient borrow material and funding. Restoration of channel and floodplain connectivity provides for long term stabilization and ecosystem recovery, and can best satisfy goals and objectives. This is done through earth movement, grade control, revegetation efforts, provision of bank structures or large wood, and channel bed armoring and floodplain vegetation. Such restoration provides for a gradually-varied longitudinal profile, as well as appropriate planform and sinuosity.
Colorado front Range Flood of 2013: Peak Flows and Flood Frequencies
Yochum, S.E. (2015). Colorado front Range Flood of 2013: Peak Flows and Flood Frequencies. Proceedings of the 3rd Joint Federal Interagency Conference on Sedimentation and Hydrologic Modeling, April 19-23, 2015, Reno, Nevada, USA.
ABSTRACT: In September of 2013, the Colorado Front Range foothills experienced an extensive period of rainfall that culminated in a major flood that peaked in many streams on Friday, the 13th. Rainfall depths of up to 18 inches were recorded over a 10 day period, with a large proportion of the rainfall falling over a 36 hour period. These foothill locations on average receive between 17 and 19 inches of precipitation annually; this event delivered an average year of rainfall at some locations. In response, many streams in the South Platte and Arkansas River basins flooded. To quantify the magnitude of the flood peaks, several entities implemented forensic hydrology methods to develop peak flow estimates, including the NRCS, USGS, and retired USGS hydrologist Bob Jarrett. Peak discharges of up to 60,000 cfs were quantified. Peak flow unit discharges varied by catchment size, as would be expected. Unit discharges as large as 1340 cfs/mi2 were measured. For locations with streamgages, revised flow frequency estimates were developed using the logPearson methodology as presented in Bulletin 17B. The 2013 peaks were included in this analysis. For the larger streams impacted by the flooding, this flood had return intervals ranging from a 5- to 25-year flood (Fountain Creek), 25- to 50-year flood (Cache la Poudre River, South Platte River), 100-year flood (Big Thompson River), 100- to 200-year flood (Boulder Creek, Coal Creek), and greater than the 200-year flood (Lefthand Creek, Saint Vrain Creek, Fish Creek).
Battle Creek: Lessons Learned from Tinkering at a Confluence
Yochum, S.E. (2015). Battle Creek: Lessons Learned from Tinkering at a Confluence. Proceedings of the 3rd Joint Federal Interagency Conference on Sedimentation and Hydrologic Modeling, April 19-23, 2015, Reno, Nevada, USA.
ABSTRACT: In the Autumn of 2008 a stream restoration project was constructed in Battle Creek just above the confluence with the Little Snake River, on the border between Colorado and Wyoming. Relevant structures were cross vanes and stream barbs, with the objectives apparently being bank stabilization and habitat enhancement for game fish. After construction, floods occurred in 2009, 2010, and 2011, including a 100-year flood in the Little Snake. With this flooding, a substantial volume of sediment was deposited in the vicinity of the Battle Creek cross vanes, forcing a channel avulsion and rapid bank erosion along multiple reaches. A review was performed to determine the likely causes of this problem. Based on a site assessment, an evaluation of historic aerial imagery, and a hydraulic model, it was concluded that the installed structures did not cause the sediment deposition and resulting bank erosion. Decreased sediment transport capacity due to backwater effects imposed by the Little Snake flooding was most likely the cause of the deposition, with the problem compounded by riparian grazing reducing the quality of the vegetative condition. Structural measures should not have been installed on Battle Creek in the vicinity of the confluence due to periodic aggradation induced by Little Snake River flooding. While these structures likely did not worsen the aggradation problem, they also provided little benefit since bank destabilization is primarily the result of backwater-induced sediment deposition and insufficient vegetative cover. Instead, riparian fencing and grazing management should have been the focus, to encourage robust riparian vegetation growth that can resist destabilization induced by the periodic sediment deposition. This project illustrates an example where livestock management should have been the core approach used in riparian restoration, rather than an engineered approach; more detailed analysis and planning by a stream-focused group of specialists was needed early in this project.
Government Creek: Stream Restoration Assessment
Yochum, S.E. (2015). Government Creek: Stream Restoration Assessment. U.S. Forest Service, National Stream and Aquatic Ecology Center, Project Report for the Ashley National Forest, September 17, 2015.
SUMMARY: Government Creek in Government Park has a series of headcuts propagating along the channel that are creating incised channels, bank instability, channel widening, and drops in local water table levels, greatly reducing the areal extent of riparian-obligate vegetative species. As a result, wet meadows are being replaced by upland vegetative species on terraces. Without taking action, additional wet meadows will be lost as the headcutting continues. Fortunately, these headcuts are relatively low and can be arrested with a reasonable amount of confidence for success. Additionally, as a small headwater stream the channel has lower stream power for widening and transporting sediment; the amount of eroded material is reasonable and could be replaced. It is feasible to fill these incised channels with local borrow material at a reasonable cost for excavation, restoring the local channel elevation and water table. Combined with grade-control structures, Government Park has the potential for restoration to what is assumed to be pre-settlement conditions of a relatively-wide wet meadow. A full wet meadow restoration, with grade control structures and livestock grazing exclusion is recommended for implementation.
Windy Park: Stream Restoration Assessment
Yochum, S.E. (2015). Windy Park: Stream Restoration Assessment. U.S. Forest Service, National Stream and Aquatic Ecology Center, Project Report for the Ashley National Forest, October 1, 2015.
SUMMARY: Windy Park has a high-quality wet meadow that is being threatened by headcut development and incision. The resulting reduction in the local water table levels will greatly reduce the areal extent of riparian-obligate vegetative species in this wetland. Without mitigation, the wet meadow will be replaced by upland vegetative species on terraces. Fortunately, these headcuts are relatively low and can be arrested with a high level of confidence for success. The limited extent of incision can be filled and, in combination with grade-control structures, the wet meadow in Windy Park can be maintained and restored. Grade Control Structures and Infill, with Livestock Grazing Exclusion is recommended for implementation, since it would prevent the loss of additional wet meadow area and restore the lost meadow extent.
Wildfire-Induced Flooding and Erosion-Potential Modeling: Examples from Colorado, 2012 and 2013
Yochum, S.E., Norman, J.B. (2015). Wildfire-Induced Flooding and Erosion-Potential Modeling: Examples from Colorado, 2012 and 2013. Proceedings of the 3rd Joint Federal Interagency Conference on Sedimentation and Hydrologic Modeling, April 19-23, 2015, Reno, Nevada, USA.
ABSTRACT: Flooding and erosion potential for the High Park, Black Forest and West Fork Complex wildfires, in Colorado, were modeled using the Natural Resources Conservation Service (NRCS) curve number (CN) and Revised Universal Soil Loss Equation (RUSLE) methodologies. The CN technique, implemented within HEC-HMS, estimated direct runoff from rain events for both pre- and post-fire conditions, to develop estimates of increased flood hazard and potential threat to life and property. A spatial version of RUSLE was developed to predict pre- and post-fire sediment yields for each 10×10 meter area for hydrologic flow paths connected to the burn area. The pre- and post-fire CN runoff and RUSLE sediment erosion estimates were summarized at strategically-located pour points within and downstream of the wildfire burn areas. Results were computed at 96 pour points for the High Park Fire (87,000 acres), 52 pour points for the Black Forest wildfire (14,300 acres), and 70 pour points for the West Fork Complex wildfire (109,000 acres). Post-fire conditions were simulated to result in 100-year floods from 10-year rainfall events in the most severely-impacted watersheds and up to 70 to >200 times of sediment expected on an annual basis. The results are most appropriately used in a comparative manner, between catchments.
Spatial characterization of roughness elements in high-gradient channels of the Fraser Experimental Forest, Colorado, USA
Yochum, S.E., Bledsoe, B.P., Wohl, E., David, G.C.L. (2014). Spatial characterization of roughness elements in high-gradient channels of the Fraser Experimental Forest, Colorado, USA. Water Resources Research 50.
ABSTRACT: We collected high-resolution LiDAR-based spatial and reach-average flow resistance data at a range of flows in headwater stream channels of the Fraser Experimental Forest, Colorado, USA. Using these data, we implemented a random field approach for assessing the variability of detrended bed elevations and flow depths for both the entire channel width and the thalweg-centered 50% of the channel width (to exclude bank effects). The spatial characteristics of these channels, due to bedforms, large clasts and instream wood, were compared with Darcy-Weisbach f and stream type through the use of the first four probability density function moments (mean, variance, skewness, kurtosis). The standard deviation of the bed elevations (sigma z) combined with depth (h), as relative bedform submergence (h/sigma z), was well correlated with f (R2 = 0.81) for the 50% of channel width. The explained variance decreased substantially (R2 = 0.69) when accounting for the entire width, indicating lesser contribution of channel edges to flow resistance. The flow depth skew also explained a substantial amount of the variance in f (R2 = 0.78). A spectrum of channel types is evident in depth plots of skew versus kurtosis, with channel types ranging from plane bed, transitional, step pool/cascade, to cascade. These results varied when bank effects were included or excluded, although definitive patterns were observed for both analyses. Random field analyses may be valuable for developing tools for predicting flow resistance, as well as for quantifying the spectrum of morphologic change in high-gradient channel types, from plane bed through cascade.
Photographic Guidance for Selecting Flow Resistance Coefficients in High-Gradient Channels
Yochum, S.E.; Comiti, F.; Wohl, E.; David, G.C.L.; Mao, L. (2014). Photographic Guidance for Selecting Flow Resistance Coefficients in High-Gradient Channels. Gen. Tech. Rep. RMRS-GTR-323. Fort Collins, CO: U.S. Department of Agriculture, Forest Service, Rocky Mountain Research Station. 91 p.
ABSTRACT: Photographic guidance is presented to assist with the estimation of Manning’s n and Darcy-Weisbach f in high-gradient plane-bed, step-pool, and cascade channels. Reaches both with and without instream wood are included. These coefficients are necessary for the estimation of reach average velocity, energy loss, and discharge. Using data collected in 19 stream channels located in the State of Colorado and the Eastern Italian Alps, on slopes ranging from 2.4 to 21 percent, guidance is provided for low through bankfull flows. Guidance for low flow resistance estimation is additionally provided using data collected in 29 channels in the State of Washington, New Zealand, Chile, and Argentina. Bankfull n values range from 0.048 to 0.30 and low flow n values range from 0.057 to 0.96. Discussions of flow resistance mechanisms and quantitative prediction tools are also presented.
Colorado Front Range Flood of 2013: Peak Flow Estimates at Selected Mountain Stream Locations
Yochum, S.E., Moore, D.S. (2013). Colorado Front Range Flood of 2013: Peak Flow Estimates at Selected Mountain Stream Locations. USDA Natural Resources Conservation Service, Colorado State Office, December 16, 2013.
ABSTRACT: Peak flow estimates were developed in 15 mountain streams for the Front Range Flood of September 2013. These measurements were collected to inform resource managers of the flood severity, aid in the development of revised flow-frequency relationships, and quantify the flood response of key catchments burned during the 2012 High Park Fire. These stream reaches ranged from Jamestown in the South to catchments draining the High Park Fire area in the Poudre Canyon in the North, though are only a sample of the mountain streams impacted by the flooding. The critical depth method was used in this analysis, using replicate cross sections in channels with slopes greater than 1 percent. The highest peak flows were measured in the North Fork of the Big Thompson River upstream of Drake (18,400 cubic feet per second, cfs), the Little Thompson River at Pinewood Springs (14,600 cfs), West Creek upstream of Glen Haven (11,000 cfs) and Buckhorn Creek upstream of Masonville (11,000 cfs). The highest flow yields (peak flow normalized by drainage area) were measured in Fish Creek upstream of Lake Estes (442 cfs/mi2), West Creek upstream of Glen Haven (477 cfs/mi2), Little James Creek upstream of Jamestown (579 cfs/mi2), Fox Creek upstream of Glen Haven (486 cfs/mi2), and Skin Gulch upstream of Stove Prairie Road (720 cfs/mi2). The streams with the highest flow yields correspond to the channels (and adjacent properties) that received a large amount of flood damage, with large disturbances to channel-stabilizing bank vegetation. The highest peak flow yield (Skin Gulch) flowed from a catchment with a substantial amount of high soil burn severity from the 2012 High Park Fire. Overall, the peak flows measured in these 15 reaches correspond to return intervals ranging from a 25-year flood event to approximately 5 times the 100-year flood.
Characterizing spatial variability in velocity and turbulence intensity using 3-D acoustic Doppler velocimeter data in a plane-bed reach of East St. Louis Creek, Colorado, USA
David, G.C.L., Legleiter, C.J., Wohl, E., Yochum, S.E. (2013). Characterizing spatial variability in velocity and turbulence intensity using 3-D acoustic Doppler velocimeter data in a plane-bed reach of East St. Louis Creek, Colorado, USA. Geomorphology 183, 28-44.
ABSTRACT: We investigated the influence on flow resistance of flow structure and turbulence at the reach scale in a mountain channel using 3-D velocity measurements and geostatistical analysis to understand the complexity of the flow structure in a reach with limited bed irregularities. The increase in flow resistance at low flows in a plane-bed reach was not fully explained by grain resistance, therefore detailed 3-D velocity measurements were made to investigate spatial variability in velocity and turbulence components and potential controls on flow resistance. One plane-bed reach was surveyed over two stages in Fraser Experimental Forest, Colorado, using a combination of a total station, LiDAR (Light Detection and Ranging), and a SonTek Flowtracker handheld ADV (acoustic Doppler velocimeter). LiDAR was used to capture bank and channel geometry at low flows, whereas the water surface and bed data were collected with the total station at all flows. We used the standard deviation of bed elevation (σb) within a moving window as an index of roughness height (ks) and calculated the relative submergence of the bed at different stages as h/ks, where h is the local flow depth. ADV measurements were collected on a grid with a 0.3 m to 0.5 m spacing. Geostatistical analysis of the velocity data indicated that the flow was highly three-dimensional and varied based on stage, demonstrating that even small irregularities in the bed have a significant influence on the flow characteristics…
Velocity prediction in high-gradient channels
Yochum, S.E., Bledsoe, B.P., David, G.C.L., Wohl, E. (2012). Velocity prediction in high-gradient channels. Journal of Hydrology 424-425, 84-98.
In 15 mountain stream reaches containing instream wood, we characterized velocity and flow resistance at bankfull through low flows. These data were: (1) used to assess the accuracy of previously published velocity prediction techniques for high-gradient channels; and (2) were combined with field data from other studies to develop general methodologies for predicting velocity and flow resistance in alluvial and mixed alluvial-bedrock channels both with and without step-forming instream wood. Velocity and flow resistance were poorly predicted by variables characterizing grain size and relative grain submergence. Conversely, methods based on detrended standard deviation of bed elevations (sigma z) and relative bedform submergence (h/sigma z) explained up to 84% of the variance in the measured flow resistance coefficients and 97% of the variance in dimensionless velocity. With an average velocity of 0.44 m/s for the collected measurements, velocity was predicted with RMS (root mean square) error as low as 0.071 m/s (16% of average) when discharge and bedform geometry is known and 0.10 m/s (23%) when only bedform geometry is known. Additionally, an empirical relationship indicates V/u* = h/sigma z, supporting previously published laboratory findings using a field-based dataset in complex high-gradient channels. Interactions between instream wood and clasts result in substantially enhanced step heights and flow resistance. This compound effect defies description by grain size and relative grain submergence. However, sigma z and h/sigma z quantify variability due to both clasts in combination with wood and clasts alone, providing relatively accurate predictions for the tested dataset and indicating substantial predictive capabilities in channels where bedforms are the primary source of flow resistance.
Comparative analysis of bed resistance partitioning in high-gradient streams
David, G.C.L., Wohl, E., Yochum, S.E., Bledsoe, B.P. (2011). Comparative analysis of bed resistance partitioning in high-gradient streams. Water Resources Research 47, W07507.
ABSTRACT: Total flow resistance can be partitioned into its components of grain (ff grain), form (ffstep), wood (ffwood), and spill (ffspill) resistance. Methods for partitioning flow resistance developed for low-gradient streams are commonly applied to high-gradient systems. We examined the most widely used methods for calculating each component of resistance, along with the limitations of these methods, using data gathered from 15 high-gradient (0.02 < S0 < 0.195) step-pool, cascade, and plane-bed reaches in Fraser Experimental Forest. We calculated grain resistance using three equations that relate relative submergence (R/Dm) to ff grain as well as using an additive drag approach. The drag approach was also used for calculating ff wood and ff step. The ff grain contributed the smallest amount toward all reaches at all flows, although the value varied with the method used. The Parker and Peterson (1980) equation using D90 best represented ff grain at high flows, whereas the Keulegan (1938) equation using D50 best characterized ff grain at base flows, giving a lower bound for grain resistance. This suggests that ff grain may be better represented if two grain sizes are used to calculate this component of resistance. The drag approach, which is used to calculate wood resistance, overestimated the significance of individual logs in the channel. The contribution of ff spill was reduced at higher flows when form drag around the step is accounted for at higher flows. We propose a method for evaluating the contribution of ff step that accounts for form drag around the steps once they are submerged at higher flows. We evaluated the potential sources of error for the estimation of each component of resistance. Determination of the drag coefficient was one of the major sources of error when calculating drag around wood, steps, or boulders.
Boxelder B-3: Dam Breach Analysis
Yochum, S.E. (2011). Boxelder B-3: Dam Breach Analysis. USDA Natural Resources Conservation Service, Colorado State Office, January 14, 2011.
SUMMARY: Predictions have been made of the likely extent and timing of flooding resulting from a catastrophic breach of the Boxelder B-3 flood retention structure. This report details the dam breach analysis performed on the reservoir for the purpose of evaluating the hazard classification and for use in an emergency action plan. In the unlikely case of such a breach, farm and ranch land will be flooded, several highways and I-25 will be inundated, and bridges may be damaged. The extent of inundation with expected depth*velocity products greater than 7 indicate that many homes and businesses will be threatened with damage or destruction. Due to this loss of life potential, it is recommended that the hazard classification of this structure be increased from its current significant level to a high hazard classification.
Flow Resistance Estimation in High-Gradient Streams
Yochum, S.E., Bledsoe, B. (2010). Flow Resistance Estimation in High-Gradient Streams. Proceedings of the 4th Federal Interagency Hydrologic Modeling Conference, June 27 – July 1, 2010, Riviera Hotel, Las Vegas, Nevada.
ABSTRACT: Methods for predicting resistance coefficients in high-gradient streams are essential for hydraulic modeling, stream restoration, geomorphic analysis, and quantifying ecological habitat characteristics. Nine figures documenting Manning’s n and Darcy-Weisbach ff are provided for low, mid and near-bankfull flows in cascade, step pool and plane bed stream reaches in the Fraser Experimental Forest, Colorado. Photographs from multiple perspectives and flows are given to illustrate reach characteristics. Profile plots and bed material D84 are also included. The stream reaches have slopes ranging from 1.5 to 20 percent, with measurements during discharges ranging from 0.0067 to 0.61 cms (0.23 to 21 cfs). Manning’s n varied from 0.048 to 0.52.
Controls on at-a-station hydraulic geometry in steep headwater streams, Colorado, USA
David, G.C.L., Wohl, E., Yochum, S.E., Bledsoe, B.P. (2010). Controls on at-a-station hydraulic geometry in steep headwater streams, Colorado, USA. Earth Surface Processes and Landforms.
ABSTRACT: Detailed hydraulic measurements were made in nine step-pool, five cascade and one plane-bed reach in Fraser Experimental Forest, Colorado to better understand at-a-station hydraulic geometry (AHG) relations in these channel types. Average values for AHG exponents, m (0·49), f (0·39), and b (0·16), were well within the range found by other researchers working in steep gradient channels. A principal component analysis (PCA) was used to compare the combined variations in all three exponents against fi ve potential control variables: wood, D84, grain-size distribution (σ), coefficient of variation of pool volume, average roughness-area (projected wetted area) and bed gradient. The gradient and average roughness-area were found to be significantly related to the PCA axis scores, indicating that both driving and resisting forces influence the rates of change of velocity, depth and width with discharge. Further analysis of the exponents showed that reaches with m > b + f are most likely dominated by grain resistance and reaches below this value (m < b + f) are dominated by form resistance.
Controls on spatial variations in flow resistance along steep mountain streams
David, G.C.L., Wohl, E., Yochum, S.E., Bledsoe, B.P. (2010). Controls on spatial variations in flow resistance along steep mountain streams. Water Resources Research 46, W03513.
ABSTRACT: Detailed channel and water surface surveys were conducted on 15 mountain stream reaches (9 step‐pool, 5 cascade, and 1 plane‐bed) using a tripod‐mounted Light Detection and Ranging scanner and laser theodolite. Reach‐average velocities were measured at varying discharges with dye tracers and fluorometers. Multiple regressions and analysis of variance tests were used to test hypothesized correlations between Darcy‐Weisbach friction coefficient, f, and potential control variables. Gradient (S0) and relative grain submergence (Rh/D84) individually explained a low proportion of the variability in f (R2 = 0.18), where Rh is hydraulic radius, D84 is the 84th percentile of the cumulative grain size distribution, and R2 is equal to the coefficient of determination. Because channel type, grain size, and S0 are interrelated, we tested the hypothesis that f is highly correlated with all three of these variables or a combination of the above variables with flow period (a categorical variable) or dimensionless unit discharge (q*). Total resistance correlated strongly (adj‐R2 = 0.74, 0.69, and 0.64) with S0, flow period, wood load (volume of wood/m2 of channel), q*, and channel type (step‐pool, cascade, plane‐bed). Total resistance differed between step‐pool and plane‐bed and between cascade and plane‐bed reaches. Significant differences in f in step‐pool and cascade reaches were found at the same values of flow and S0. The regression analyses indicate that discharge explains the most variability in f, followed by S0 when discharge is similar among channel reaches, but that Rh/D84 is not an appropriate variable in these steep mountain streams to represent variations in both resistance and discharge. Results also indicate that the forms of resistance among channel types are sufficiently different to change the relationship of the control variables with f in each channel type. These results can be used to further the development of predictive equations for high‐gradient mountain streams.
Flow Resistance Prediction in High-Gradient Streams
Yochum, S.E. (2010). Flow Resistance Prediction in High-Gradient Streams. PhD Dissertation. Colorado State University, Department of Civil and Environmental Engineering, Fort Collins, Colorado. Fall, 2010.
ABSTRACT: Flow resistance measurements were collected on high-gradient streams in the Fraser Experimental Forest, Colorado, for bankfull through low flows using Rhodamine WT dye tracing, ground-based LiDAR scans, and laser theodolite surveying of longitudinal profiles and below-water features. A dataset of 59 resistance measurements was collected on fifteen reaches with instream wood present in varying densities. Values of Manning’s n ranged from 0.05 to 0.52, and Darcy-Weisbach f varied from 0.28 to 56. All measurements indicated subcritical reach-average conditions, with Froude numbers ranging from 0.15 to 0.78. Relative grain submergence (R/D84) was a poor predictor of flow resistance while relative bedform submergence, defined as the ratio of depth or hydraulic radius to the standard deviation of the residuals of a bed profile regression (hm/σz, R/σz), explained up to 76 and 80 percent of the variance of n and f, respectively. Both clasts and instream wood contribute to bed variability; steps are heightened by wood lodging among the clast steps. Hence relative bedform submergence captures the combined influence of wood and clasts, which contribute both form and spill resistance. Relative bedform submergence is less effective for prediction in reaches with substantial non-step-forming instream wood and in steep channels. In the steepest reaches, with slopes over about 18 percent, the data indicate a shift towards a skimming regime with a partial submergence of bedforms and a threshold reduction in flow resistance. Three-dimensional measures of geometric variability were explored, to assess the correlation of flow resistance with higher-order spatial variation due to composite effects of bedforms, large clasts, and instream wood. With the exclusion of bank effects, a normalized variable (ha3/σz3) explained 77 and 81 percent of the variance of n and f, respectively. Multivariate regression models with variables describing bedforms, bankforms, and instream wood explained 87 percent of the variance of n and f. On average, flow resistance due to bedforms (form and spill) are the greatest contributor to overall flow resistance in these high-gradient streams, followed by form resistance generated by bankforms, and lastly, by form resistance induced by non-step instream wood.
Boxelder B-2, B-3, and B-4: Probable Maximum Flood Analysis
Yochum, S.E. (2010). Boxelder B-2, B-3, and B-4: Probable Maximum Flood Analysis. USDA Natural Resources Conservation Service, Colorado State Office, August 26, 2010.
SUMMARY: Rainfall-runoff analyses were performed of the probable maximum precipitation (PMP) event in the Boxelder B-4, -3 and -2 watersheds. In the event of a Probable Maximum Flood (PMF), the Boxelder B-4 structure will be substantially overtopped, by 4.0 and 2.3 feet for the 6- and 24-hour events, respectively. The existing spillways will convey about 45 percent of the PMP. The B-3 embankment will be overtopped, by 6.0 and 5.1 feet for the 6- and 24-hour events. The existing spillways will convey about 37 percent of the PMP. The B-2 embankment will be overtopped by 8.7 and 6.1 feet for the 6- and 24-hour events. This model assumes that the B-5 and B-6 structures breach. The existing spillways will convey about 37 percent of the PMP. Considering the lack of armor, patchy vegetative cover of the downstream face, and substantial depth and duration of overtopping for all five Boxelder flood control reservoirs, all the embankments will likely fail in the case of either a 6-hour or 24-hour PMP event.
Boxelder B-4: Dam Breach Analysis
Yochum, S.E. (2009). Boxelder B-4: Dam Breach Analysis. USDA Natural Resources Conservation Service, Colorado State Office, Junw 2, 2009.
SUMMARY: Predictions have been made of the likely extent and timing of flood flow resulting from a catastrophic breach of the Boxelder B-4 flood retention structure. This report details the dam breach analysis performed on the reservoir for the purpose of evaluating the hazard classification and for use in an emergency action plan. In the unlikely case of such a breach, farm and ranch land will be flooded, several highways and I-25 will be inundated, and bridges may be damaged. Most substantially, four residences will be threatened with substantial damage, with a depth*velocity product greater than 7. Due to this potential for loss of life, it is recommended that the hazard classification of this structure be increased from its current significant level to a high hazard classification. If these few structures were relocated or removed, retaining a significant hazard classification may be possible.
Boxelder B-2: Dam Breach Analysis
Yochum, S.E. (2009). Boxelder B-2: Dam Breach Analysis. USDA Natural Resources Conservation Service, Colorado State Office, March 3, 2009.
SUMMARY: Predictions have been made of the likely extent and timing of flood flow resulting from a catastrophic breach of the Boxelder B-2 flood retention structure. This report details the dam breach analysis performed on the reservoir for the purpose of reevaluating the hazard classification and for use in an emergency action plan, in the unlikely case of a breach. The breach hydrograph was routed using HEC-RAS 4.0 from the embankment to the confluence with the Poudre River, 20 miles downstream. According to the model, the flow attenuates to 75,000 cfs at the northern limit of Wellington, 72,000 cfs at the southern limit of Wellington, 56,000 cfs in the eastern suburbs of Fort Collins, and 52,000 cfs at the Poudre River. This final discharge corresponds to about 4.5-times the 100-year flood event of 11,200 cfs. In the most-populated portion of the floodway, Wellington, the extent of inundation with expected depth*velocity products greater than 7 indicate that hundreds of homes and businesses will be threatened with damage or destruction, farm and ranch land will be flooded, a railroad, several highways and I-25 will be inundated, bridges may be damaged, and many lives could be lost. Due to this potential, it is recommended that the hazard classification of the Boxelder B-2 structure be increased from its current significant level to a high hazard.
Case Study of the Big Bay Dam Failure: Accuracy and Comparison of Breach Predictions
Yochum, S.E., Goertz, L.A., Jones, P.H. (2008). Case Study of the Big Bay Dam Failure: Accuracy and Comparison of Breach Predictions. ASCE Journal of Hydraulic Engineering, 134(9), 1285-1293. doi:10.1061/ASCE0733-94292008134:91285.
ABSTRACT: The Big Bay Dam embankment failure occurred on March 12, 2004, releasing 17,500,000 m3 14,200 acre-ft of water. In all, 104 structures were documented as being damaged or destroyed as a result of this failure. No human lives were lost. This paper documents data gathered and analyses performed on the hydraulics of the failure. High water levels from the failure were marked and measured. A HEC-RAS unsteady flow model was developed. Using observed breach geometry, HEC-RAS provided results that agreed with the measured high water marks from −0.02 to −0.90 m and 0.01 to 0.62 m with associated modeled flow depths ranging from 9.3 to 5.7 m from 30 to 19 ft. A peak breach flow of 4,160 m3 / s 147,000 ft3 / s was predicted at the embankment. Breach peak flow prediction equations were found to substantially underpredict the peak flow indicated by HEC-RAS for this failure. HEC-RAS modeling utilizing predicted breach geometry and formation time also underpredicted the peak flow, but by a lesser amount. The National Resources Conservation Service models WinTR-20 and TR 66 were also assessed. WinTR-20 results compared reasonably well with the high water marks for this failure. TR-66 results did not compare well.
Willow Creek Stream Restoration: Planning Study
Yochum, S., Villa, C., Brown, R., Burt, R., Weber, T., Sims, M. (2007). Willow Creek Stream Restoration: Planning Study. USDA Natural Resources Conservation Service, Colorado State Office, April 13, 2007.
SUMMARY: Willow Creek downstream of Creede, Colorado is currently in an unstable, braided condition due to disturbance from historic mining activities. The 1.5 mile section of stream and floodplain from the mouth of Creede’s flood-control flume to the confluence with the Rio Grande requires a restoration plan to provide alternatives on approaches to restore stream function and provide a more visually-pleasing entrance to the historic tourist-town of Creede. Historic mining activities have negatively impacted the natural resources of the watershed surrounding the community of Creede, most visibly within the Willow Creek floodplain. Formed by the confluence of East and West Willow Creeks upstream of Creede, Willow Creek is a tributary of the Rio Grande. The ecosystem within Willow Creek’s floodplain has had significant impairments due to historic mining activities and the resulting physical and chemical legacy (metals; especially cadmium, lead and zinc) from the mining and processing activities. Willow Creek is currently in a braided form, an unsightly and locally atypical geomorphic condition that, in combination with the water and soil contamination, has led to poor ecosystem function. The substantial water-quality impairments and poor morphologic conditions are preventing significant invertebrate and fish populations. Additional problems in this floodplain stem for poor grass and willow populations due to physical disturbance from the braiding, mechanized manipulation, lack of soil, and contaminated soils and groundwater. The residents of the town of Creede and the surrounding community have developed a community-based effort to identify and address the most pressing environmental concerns with the Willow Creek watershed. The Willow Creek Reclamation Committee (WCRC) is directing efforts aimed at improving water quality and physical habitat in the watershed as part of a long-term watershed management program which focuses on restoring the stream and reducing impacts to the Rio Grande. The purpose of this planning report is to collect and present available data and publications on the floodplain into one package, to provide informed alternatives and recommendations for a restoration. Cost estimates are needed to seek out funding opportunities for the restoration and have been provided. Once funding is secured, a full design will then be needed for construction. Due to the high degree of destruction and neglect of the floodplain by the mining activities, the challenges of this project are substantial – the costs of a reconstruction will also be substantial.
NRCS Stream Restoration Design
NRCS. (2007). Stream Restoration Design, USDA Natural Resources Conservation Service, National Engineering Handbook, Part 654.
The management of streams is a continuing balance between what people want and what plants and animals need. In an ideal world, a stream can satisfy both—in reality, the balance is ephemeral, at best, as streams evolve and humans continue to imprint their desires on the adjoining or upland landscape. Intervention is often needed when the balance becomes so skewed that the function of streams for either people or nature is at risk. Just as one would consult a doctor regarding an illness affecting the body’s function, one should consult a hydraulic engineer, stream ecologist, geomorphologist, aquatic biologist, or other riparian specialist for the diagnosis or treatment of a stream disorder or problem. An inappropriate or poorly designed restoration project can worsen or broaden the disorder. Site-specific designs based on sound, scientific experience are needed to properly select the size, orientation, and location of stream restoration techniques. Effective designs also need to include appropriate management techniques that remove sources of disturbance, allow the design elements to function well together, and enhance the stream’s ability for ecological regeneration. In planning and designing solutions to some stream problems, simply modifying adjacent land and riparian management practices may be all that is needed to improve degraded stream conditions. Streams are integrators of all upland problems, so some stream conditions are symptomatic of mismanagement of their surrounding watershed(s). In these cases, solutions may lie not only in restoring the stream directly, but in changing land uses and management practices throughout the entire watershed
Hydrologic Study of Wray Floodwater Detention Structures
Yochum, S.E. (2006). Hydrologic Study of Wray Floodwater Detention Structures. USDA Natural Resources Conservation Service, Colorado State Office, October 23, 2006.
Predictions have been made of the expected hydrologic response of the watersheds above, from and immediately below six floodwater detention structures in Wray, Colorado. All six of the structures were found to be capable of conveying the probable maximum precipitation (PMP) event through their principal and emergency spillways without overtopping their embankments. For all structures, the six hour storm was found to cause higher pool water surface elevations than the 24-hour storm. Modeling of structures 1 and 2 indicate that the PMP will fill the reservoirs to within 3.0 and 0.5 feet, respectively, of the top of embankment. Modeling of structures 3 and 4 indicate that the PMP will fill the reservoirs to within 2.5 and 0.8 feet, respectively, of the top of embankment. Modeling of structures 5 and 6 indicate that that the PMP will fill the reservoirs to within 3.2 and 1.5 feet, respectively, of the top of embankment.
Willow Park Reservoir Probable Maximum Precipitation (PMP) Analysis
Yochum, S.E. (2006) Willow Park Reservoir PMP Analysis. USDA Natural Resources Conservation Service, Rocky Mountain Engineering Team, Lakewood, Colorado.
CONCLUSIONS: Four hydrologic analyses were performed to assess the capability of the existing Willow Park principal and emergency spillways in passing the Probable Maximum Flood response to the PMP event. It is common practice through the United States for a high hazard dam, such as Willow Park, to be able to pass the PMF safely. The analyses included simulations for both the 6- and 24-hour storms, with and without a simulated Cloud Peak reservoir embankment failure. The results of the simulations are provided in Figure 15 and Tables 3 through 6. The analyses indicate that the emergency spillway for Cloud Peak reservoir is significantly undersized – it can only pass 14 to 11 percent of the PMF. If a PMP occurs, both the Cloud Peak and Willow Park reservoir embankments will be overtopped and most likely fail.
Cloud Peak Reservoir Dam Breach Analysis
Yochum, S.E. (2005) Cloud Peak Reservoir Dam Breach Analysis. USDA Natural Resources Conservation Service, Rocky Mountain Engineering Team, Lakewood, Colorado.
ABBREVIATED SUMMARY: A catastrophic breach of Cloud Peak dam will initially cause a peak flow of 29,900 cfs. The following Willow Park dam failure will increase the peak flow to 133,000 cfs. Eighty-one linear miles of mountain valleys, floodplains and agricultural production areas along South Piney Creek, Piney Creek, and Clear Creek will be inundated before the floodwave finally attenuates to about 15,900 cfs at the confluence of Clear Creek and the Powder River. This is approximately a 12-year event according to the streamgage on the Powder River at Morehead, near the Montana state line. Figure 31 provides the routed breach hydrographs at 11 points within the analysis zone. In the case of such a breach, hundreds of homes and businesses will be threatened with damage or destruction, farm and ranch land will be flooded, several highways and one interstate will be inundated, bridges may be damaged, and many lives could be lost.
Mancos Valley Salinity: Hydrologic Study Report
Yochum, S.E. (2004). Mancos Valley Salinity: Hydrologic Study Report. USDA Natural Resources Conservation Service, Northern Plains Engineering Team. Lakewood, Colorado.
ABBREVIATED SUMMARY: The Mancos Valley is an agricultural valley located in the lower portions of a 203 square mile Mancos River watershed. As of 1994, there were 14,900 acres being used for agriculture, of which 11,700 acres were irrigated. Of this irrigated area, 9900 acres are irrigated by flood practices while 1800 acres are irrigated by sprinklers. Irrigation water is diverted at approximately 46 locations of the Mancos River and its tributaries with an average diverted volume of 42,100 ac-ft. The average system efficiency was found to be 32 percent. Exposures of Mancos Shale are extensive in the watershed. The low gentle folds of this formation are interspersed by faults and uplift of a few hundreds of feet or less. These uplift features appear to have a direct relationship to salt yield from the watershed. It appears that the lower portion of the unit is extremely salty while upper portions contain moderate to low levels of salt. This variability in salt availability can also be observed in soil conductivity data collected throughout the valley. Water quantity and quality data have been collected by various federal and state agencies and the Ute Mountain Reservation. In addition to this, several synoptics were conducted in 2001. The synoptics indicated total dissolved solid concentrations ranging from 32 to 3070 mg/l. The results from earlier (1979-81) NRCS synoptics indicate a similar range, though some higher values were noted in the Mud and Weber watersheds. Baseflow concentrations, load, and concentration gradients all indicate a zone of high salinity contribution (a “hot zone”) in a strip of land passing from the northwest to the southeast, with lesser to little contribution outside of this zone. Specifically, the Mud Creek reaches, the Mancos River reach between Mancos to a bit below the Mud Creek confluence, and the upper Weber Drainage appear to be large salt contribution areas. Agricultural land to the immediate northeast of this zone appears to be a moderate contributor of salt, while land above the town of Mancos appears to contribute only slightly to the river’s salt load. There does not appear to be significant contribution of salt downstream of the agricultural portion of the watershed. These observations and interpretations agree with the geologic mapping and soil conductivity levels in the basin. Interestingly, the soil conductivity measurements also shows this hot zone continuing across the drainage divide into the vicinity of Dolores, which has been shown in previous salinity control studies to be a large contributor of salt. Total dissolved solid load was computed using a seven-parameter regression model for thirty years of record and an average load of 42,300 tons/year was estimated. This value agrees remarkably well with the previous estimate of 43,000 tons/year (SCS 1984). A baseflow separation was also performed and an average load of 26,200 tons/year was estimated.
Dullknife Reservoir Dam Breach Analysis
Yochum, S.E. (2004) Dullknife Reservoir Dam Breach Analysis, USDA Natural Resources Conservation Service, Rocky Mountains Engineering Team, Lakewood, Colorado.
ABBREVIATED SUMMARY: A catastrophic breach of Dullknife dam, with an initial peak flow of about 160,000 cfs, will inundate 58 miles of floodplains along the North Fork of the Powder River and the Powder River before attenuating to about 14,500 cfs in the Powder River at Sussex. This is approximately a 12-year event for this point on the Powder River. Figure 42 provides the routed breach hydrographs at seven points within the analysis zone. In the case of such a breach, dozens of homes and ranches will be threatened with damage or destruction, several highways and one interstate will be inundated (overtopped), bridges may be damaged, and lives could be lost.
Willow Park Reservoir Dam Breach Analysis
Yochum, S.E. (2004) Willow Park Reservoir Dam Breach Analysis. USDA Natural Resources Conservation Service, Northern Plains Engineering Team, Lakewood, Colorado.
ABBREVIATED SUMMARY: A catastrophic breach of Willow Park dam, with an initial peak flow of about 75,200 cfs, will inundate 80 miles of floodplains and agricultural production areas along South Piney Creek, Piney Creek, and Clear Creek before finally attenuating to about 18,800 cfs in the Powder River a few miles downstream of the Clear Creek confluence. This is approximately a 25-year event for this point on the Powder River. Figure 28 provides the routed breach hydrographs at 12 points within the analysis zone. In the case of such a breach, hundreds of homes and businesses will be threatened with damage or destruction, farm and ranch land will be flooded, several highways and one interstate will be inundated, bridges may be damaged, and many lives could be lost.
Regional Bankfull Characteristics for the Lower Willow Creek Stream Restoration
Yochum, et. al. (2003) Regional Bankfull Characteristics for the Lower Willow Creek Stream Restoration. USDA Natural Resources Conservation Service, Northern Plains Engineering Team, Lakewood, Colorado.
INTRODUCTION: Willow Creek downstream of Creede is currently in a braided condition (Figure 1, 7 and aerial photo on report cover). This condition is atypical for streams in this region. There is a strong desire among the local community and in various agencies to restore the stream to a more typical sinuous condition, a physical condition that would better support aquatic life once water-quality improvements are made throughout the historically heavily mined watershed. The Natural Resources Conservation Service (NRCS) has taken on the task of designing the stream restoration project. In support of this design effort, a regional bankfull characteristics analysis was performed. This report documents the development and application of regional bankfull curves for application by NRCS designers, local officials, community members, and other interested parties.
Kearney Reservoir Dam Breach Analysis
Yochum, S.E. (2003) Kearney Reservoir Dam Breach Analysis. USDA Natural Resources Conservation Service, Northern Plains Engineering Team, Lakewood, Colorado
ABBREVIATED SUMMARY: A catastrophic breach of Kearney Dam, with an initial peak flow of about 94,400 cfs, will inundate the floodplains of 84 miles of stream valley of Kearney Creek, South Piney Creek, Piney Creek, and Clear Creek before finally attenuating to about 14,100 cfs in the Powder River near the Clear Creek confluence. This is a 10-year event for this point on the Powder River. Figure 28 provides the routed breach hydrographs at 12 points within the analysis zone. In the case of such a breach, hundreds of homes and businesses will be threatened with damage or destruction, several highways and one interstate will be inundated, bridges may be damaged, and many lives could be lost.
Factors Affecting Nutrient Trends in Major Rivers of the Chesapeake Bay Watershed
Sprague, L.A., Langland, M.J., Yochum, S.E., Edwards, R.E., Blomquist, J.D., Phillips, S.W., Shenk, G.W., Preston, S.D. (2000) Factors Affecting Nutrient Trends in Major Rivers of the Chesapeake Bay Watershed. U.S. Geological Survey Water-Resources Investigations Report 00-4218.
ABSTRACT: Trends in nutrient loads and flow-adjusted concentrations in the major rivers entering Chesapeake Bay were computed on the basis of water-quality data collected between 1985 and 1998 at 29 monitoring stations in the Susquehanna, Potomac, James, Rappahannock, York, Patuxent, and Choptank River Basins. Two computer models — the Chesapeake Bay Watershed Model (WSM) and the U.S. Geological Survey’s ‘Spatially Referenced Regressions on Watershed attributes’ (SPARROW) Model — were used to help explain the major factors affecting the trends. Results from WSM simulations provided information on temporal changes in contributions from major nutrient sources, and results from SPARROW model simulations provided spatial detail on the distribution of nutrient yields in these basins. Additional data on nutrient sources, basin characteristics, implementation of management practices, and ground-water inputs to surface water were analyzed to help explain the trends. The major factors affecting the trends were changes in nutrient sources and natural variations in streamflow. The dominant source of nitrogen and phosphorus from 1985 to 1998 in six of the seven tributary basins to Chesapeake Bay was determined to be agriculture. Because of the predominance of agricultural inputs, changes in agricultural nutrient sources such as manure and fertilizer, combined with decreases in agricultural acreage and implementation of best management practices (BMPs), had the greatest impact on the trends in flow-adjusted nutrient concentrations. Urban acreage and population, however, were noted to be increasing throughout the Chesapeake Bay Watershed, and as a result, delivered loads of nutrients from urban areas increased during the study period. Overall, agricultural nutrient management, in combination with load decreases from point sources due to facility upgrades and the phosphate detergent ban, led to downward trends in flow-adjusted nutrient concentrations atmany of the monitoring stations in the watershed. The loads of nutrients, however, were not reduced significantly at most of the monitoring stations. This is due primarily to higher streamflow in the latter years of the monitoring period, which led to higher loading in those years.Results of this study indicate a need for more detailed information on BMP effectiveness under a full range of hydrologic conditions and in different areas of the watershed; an internally consistent fertilizer data set; greater consideration of the effects of watershed processes on nutrient transport; a refinement of current modeling efforts; and an expansion of the non-tidal monitoring network in the Chesapeake Bay Watershed.
A Revised Load Estimation Procedure for the Susquehanna, Potomac, Patuxent, and Choptank Rivers
Yochum, S.E. (2000) A Revised Load Estimation Procedure for the Susquehanna, Potomac, Patuxent, and Choptank Rivers. U.S. Geological Survey Water Resources investigations Report 00-4156.
ABSTRACT: The U.S. Geological Survey’s Chesapeake Bay River Input Program has updated the nutrient and suspended-sediment load data base for the Susquehanna, Potomac, Patuxent, and Choptank Rivers using a multiple-window, center-estimate regression methodology. The revised method optimizes the seven-parameter regression approach that has been used historically by the program. The revised method estimates load using the fifth or center year of a sliding 9-year window. Each year a new model is run for each site and constituent, the most recent year is added, and the previous 4 years of estimates are updated. The fifth year in the 9-year window is considered the best estimate and is kept in the data base. The last year of estimation shows the most change from the previous year’s estimate and this change approaches a minimum at the fifth year. Differences between loads computed using this revised methodology and the loads populating the historical data base have been noted but the load estimates do not typically change drastically. The data base resulting from the application of this revised methodology is populated by annual and monthly load estimates that are known with greater certainty than in the previous load data base.