Ellen Wohl

Ellen Wohl
Colorado State University | CSU · Department of Geosciences

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487
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Introduction
Skills and Expertise

Publications

Publications (487)
Article
Compared to perennial streams, studies investigating the impact of large wood on sediment transport and river corridor morphology in ephemeral streams are lacking. Due to the flashy nature of ephemeral flow regimes, opportunities to directly investigate the influence of wood in ephemeral channels are limited. Additionally, given prior studies showi...
Article
Full-text available
Spatial and temporal heterogeneity, or messiness, is a broadly desirable characteristic of river corridors and an indicator of many of the geomorphic processes that sustain fluvial ecosystems. However, quantifying geomorphic heterogeneity is complicated by a lack of consistent metrics, classification schemas for dividing the river corridor into the...
Article
Full-text available
We observed a low-discharge flooding phenomenon on Little Beaver Creek, a tributary to the Cache la Poudre River in the Southern Rocky Mountains of Colorado, USA. Ice ranging in thickness from a few centimeters to 0.5 m occupied a large volume of the channel, forcing flows out of its banks. On two occasions, multiple consecutive days of uncharacter...
Preprint
Spatial and temporal heterogeneity, or messiness, is a broadly desirable characteristic of river corridors and an indicator of many of the geomorphic processes that sustain fluvial ecosystems. However, quantifying geomorphic heterogeneity is complicated by a lack of consistent metrics, classification schemas for dividing the river corridor into the...
Article
Full-text available
We use 11 years of annual surveys in streams of the Southern Rockies of Colorado, USA, to examine the persistence and geomorphic effects of logjams. Each year’s survey includes ∼300 logjams along more than 21 km of four mountain streams in primarily old‐growth subalpine forest. Streams alternate longitudinally between laterally confined reaches wit...
Article
We use Google Earth imagery, drone imagery, and ground-based field measurements to assess the abundance, spatial distribution, and size of accumulations of organic matter in perennial, intermittent, and ephemeral channels in drylands of the southwestern United States. We refer to these accumulations as organic matter jams (OMJs). We examine correla...
Article
Full-text available
The South Fork McKenzie River (SFMR) in western Oregon, USA hosts one of the largest Stage 0 stream restoration projects implemented to date. Stage 0 refers to a multichannel planform with strong hydrologic connectivity to the adjacent floodplain and surface‐subsurface connectivity. Stage 0 restoration was implemented on a 900‐m‐long reach of the S...
Article
Full-text available
The loss of beaver populations has commonly been accompanied by the failure of beaver dams, leading to stream incision, water table lowering, and the eventual transition from a beaver meadow to a drier riparian corridor. Widespread decline in North American beaver populations (Castor canadensis) has been documented from pre‐European settlement to t...
Chapter
Large rivers of the North American arctic and subarctic remain among the least‐altered large rivers in the world, and thus provide opportunities that no longer exist within temperate latitudes to investigate and understand large‐river process and form in the absence of human manipulations. The Mackenzie and Yukon Rivers are the largest arctic/subar...
Chapter
The climate and hydrology of each of the world's major river drainages are inherently diverse because these drainages cover such large areas that they encompass diverse atmospheric circulation patterns, geology, topography, vegetation, and land use. The peak unit discharge of major rivers also reflects precipitation‐generating mechanisms. The flood...
Preprint
Heterogeneity, or messiness, is a broadly desirable characteristic of river corridors and an indicator of many of the geomorphic processes that sustain fluvial ecosystems. However, quantifying geomorphic heterogeneity is complicated by a lack of consistent metrics, methods of dividing up the river corridor into the patches that form the basis for t...
Article
A blowdown in 2011 along a 1200‐m length of Glacier Creek in the Southern Rockies of Colorado, USA substantially increased the number of channel‐spanning logjams and initiated formation of a 100‐m‐long multithread channel segment. Annual logjam surveys during 2012‐2020 indicate that these effects have persisted for a decade, with the number of logj...
Article
We examine a 9.4-km-long portion of a montane river corridor in the Southern Rockies, the upper 8 km of which burned in 2020. We focus on sediment storage in logjam backwaters and how spatial heterogeneity in the river corridor attenuates downstream fluxes of material following the wildfire. Wider portions of river corridor exhibit greater spatial...
Article
Rivers historically transported unquantified volumes of driftwood to the ocean. Driftwood alters coastal sediment dynamics and provides food and habitat for diverse organisms. Floating driftwood supports open-ocean organisms. Sunken wood sustains seafloor communities. Centuries of deforestation, flow regulation, and channel engineering have substan...
Conference Paper
Full-text available
The ambition of this symposium was to review and create knowledge and praxis in bedload management, support the implementation of restoration measures in Switzerland and strengthen the international network among scientists and practitioners. Switzerland has the legal goal and the financial tools to restore its rivers from the impacts of sediment...
Article
Full-text available
Restoration aimed at rewetting the valley floor has the potential to increase organic carbon stock in the form of floodplain soil carbon, downed wood, and riparian vegetation. The primary goal of stream restoration is typically to restore habitat or maintain balance between natural ecosystem function and human land use. Although many benefits resul...
Article
Full-text available
Log jams alter gradients in hydraulic head, increase the area available for hyporheic exchange by creating backwater areas, and lead to the formation of multiple channel branches and bars that drive additional exchange. Here, we numerically simulated stream‐groundwater interactions for two constructed flume systems—one without jams and one with a s...
Article
Full-text available
Plain Language Summary Logjams are accumulations of three or more large wood pieces in streams and stream environments. Logjams can obstruct flow and create frictional resistance in small stream channels, creating many physical and beneficial ecological effects in stream environments. This includes, but is not limited to, temporary storage of water...
Article
Full-text available
Floodplains perform diverse functions, including attenuation of fluxes of water, solutes, and particulate material. Critical details of floodplain storage including magnitude, duration, and spatial distribution are strongly influenced by floodplain biogeochemical processes and biotic communities. Floodplain storage of diverse materials can be conce...
Article
We quantified floodplain large wood load (m³ wood/ha) and spatial distribution on the Upper Merced River in Yosemite National Park, California, USA. The upstream portion of the study area includes a recently burned section of the Merced River corridor and the downstream portion contains floodplain with undisturbed forest, facilitating investigation...
Article
Wood researchers increasingly rely on remote sensing products to augment field information about wood deposits in river corridors. The availability of very high resolution (<1 m) satellite imagery makes capturing wood over greater spatial extents possible, but previous studies have found difficulty in automatically extracting wood deposits due to t...
Article
Full-text available
River-wetland corridors form where a high degree of connectivity between the surface (rheic) and subsurface (hyporheic) components of streamflow creates an interconnected system of channels, wetlands, ponds, and lakes. River-wetland corridors occur where the valley floor is sufficiently wide to accommodate a laterally unconfined river planform that...
Article
Full-text available
The flow of organic matter (OM) along rivers and retention within floodplains contribute significantly to terrestrial carbon storage and ecosystem function. The storage and cycling of OM largely depend upon hydrogeomorphic characteristics of streams and valleys, including channel geometry and the connectivity of water across and within the floodpla...
Article
We measured coarse particulate organic matter (CPOM) transport along a wood‐rich, pool‐riffle mountain stream in the Southern Rockies of Colorado, USA, to examine how spatial variations in storage features and temporal variations in discharge influence the transport of CPOM. Ecologists have found that the majority of annual CPOM export occurs durin...
Article
Full-text available
Wood is an integral part of a river ecosystem and the number of restoration projects using log placements is increasing. Physical model tests were used to explore how the wood position and submergence level (discharge) affect wake structure, and hence the resulting habitat. We observed a von-Kármán vortex street (VS) for emergent logs placed at the...
Article
Full-text available
Through their modifications of channels and floodplains, beavers are a premier example of ecosystem engineers. Historical and stratigraphic records suggest that hundreds of millions of beavers once modified small to medium rivers throughout the northern hemisphere. Where beavers actively modify the channel and floodplain with dams, ponds, and canal...
Article
Full-text available
Article
The cover image is based on the Original Article Reflections on the History of Research on Large Wood in Rivers by Frederick J. Swanson et al., https://doi.org/10.1002/esp.4814. The cover image depicts Large wood in Lookout Creek, H.J. Andrews Experimental Forest, western Cascade mountains, Oregon, USA, which is the location of studies of effects o...
Preprint
Full-text available
The flow of organic matter (OM) along rivers and its retention within floodplains are fundamental to the function of aquatic and riparian ecosystems and are significant components of terrestrial carbon storage and budgets. Carbon storage and ecosystem processing of OM largely depends upon hydrogeomorphic characteristics of streams and valleys. To e...
Chapter
Despite their diversity of process and form, high-latitude rivers have distinctive characteristics that derive from the presence of permafrost and seasonal ice cover on channels. Permafrost enhances the erosional resistance of channel banks, although the permafrost is subject to thermal erosion when exposed along the channel. Permafrost also restri...
Chapter
As with the first edition of this treatise on fluvial geomorphology, the second edition is designed to review the broad and multidisciplinary body of technical literature that has grown up around river form and process. From the beginning of systematic studies of rivers in the late 19th century, individual investigators have approached the physical...
Article
We use four stream segments along a wood‐rich, pool‐riffle mountain stream in the Southern Rockies of Colorado, USA to examine how spatial variations in wood load and variations in discharge during and after the snowmelt peak flow influence the magnitude of surface and subsurface transient storage. Segments range in complexity from a single channel...
Article
Full-text available
Logjams that span the bankfull channel strongly influence hydraulics and downstream fluxes of diverse materials. Several studies quantify the longitudinal distribution of channel‐spanning logjams, but fewer studies examine changes in longitudinal distribution in response to disturbances such as floods. We use 10 years of annual surveys of a populat...
Article
Full-text available
We used the Beaver Restoration Assessment Tool (BRAT) developed at Utah State University to develop spatially explicit estimates of maximum beaver‐carrying capacity in a 160 km2 watershed in the foothills of the Southern Rockies. The watershed does not currently have beaver but has extensive evidence of past beaver occupation. BRAT uses input data...
Article
Previous work on the eastern side of Rocky Mountain National Park (RMNP), Colorado indicated correlations among waterfall location, waterfall morphology, and the characteristics of bedrock joints. Characteristics of waterfalls on the western side of the national park do not correlate as strongly with joint geometry. Longitudinal river profiles on t...
Article
Full-text available
We use field measurements and airborne‐lidar data to quantify the potential effects of valley geometry and large wood on channel erosional and depositional response to a large flood (estimated 150‐year recurrence interval) in 2011 along a mountain stream. Topographic data along 3 km of Biscuit Brook in the Catskill Mountains, New York, USA reveal r...
Article
Human impacts such as timber harvesting, channel engineering, beaver removal, and urbanization alter the physical and chemical characteristics of streams. These anthropogenic changes have reduced fallen trees and loose wood that form blockages in streams. Logjams increase hydraulic resistance and create hydraulic head gradients along the streambed...
Article
Organic carbon (OC) in valley bottom downed wood and soil that cycles over short to moderate timescales (101 to 105 yr) represents a large, dynamic, and poorly quantified pool of carbon whose distribution and residence time affects global climate. We sought to quantify this potentially important OC pool at the watershed scale to estimate its magnit...
Technical Report
Full-text available
Reviews existing knowledge of large wood and beaver dams in streams and provides guidelines for management decisions involving removal, retention, or reintroduction of logjams and beaver.
Article
Full-text available
Enthusiasm for using beaver dam analogues (BDAs) to restore incised channels and riparian corridors has been increasing. BDAs are expected to create a similar channel response to natural beaver dams by causing channel bed aggradation and overbank flow, which subsequently raise water tables and support vegetation growth. However, lack of funding for...
Article
Dynamics and functions of large wood have become integral considerations in the science and management of river systems. Study of large wood in rivers took place as monitoring of fish response to wooden structures placed in rivers in the central US in the early 20th century, but did not begin in earnest until the 1970s. Research has increased in in...
Poster
Full-text available
Numerous rivers have been confined and are eco-morphologically impaired, resulting in an increased demand for river restoration projects. Wood placements are a common and inexpensive measure. To plan and evaluate river restoration projects including wood placements, it is important to understand the interactions between flow, wood, and sediment. Fl...
Article
Downed large wood on floodplains creates similar geomorphic and ecological effects as wood in the active channel, but has been the subject of fewer geomorphic studies. I propose floodplain large wood process domains that are distinguished based on recruitment source at the reach to river‐length scale. Wood recruited to the floodplain can be autocht...
Article
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 effor...
Article
Full-text available
Legacies are persistent changes in natural systems resulting from human activities. Legacies that affect river ecosystems can result from human alterations outside of the river corridor, such as timber harvest or urbanization, or from alterations within the river corridor, including flow regulation, river engineering, and removal of large wood and...
Article
Full-text available
Floodplain spatial heterogeneity describes the three‐dimensional patchiness of floodplain substrate, surface elevation, and land cover. This heterogeneity results primarily from lateral channel migration and avulsion and decreases under diverse forms of management. Heterogeneity influences floodplain storage time, resilience to disturbance, and bio...
Article
We draw on published studies of floodplain organic carbon storage, wildfire‐related effects on floodplains in temperate and high latitudes, and case studies to propose a conceptual model of the effects of wildfire on floodplain organic carbon storage in relation to climate and valley geometry. Soil organic carbon typically constitutes the largest c...
Article
Full-text available
High-elevation mountain streams are commonly viewed as erosive environments, but they can retain sediment along river corridors for thousands of years. In 2013, an extreme flood evacuated floodplain sediment in the Colorado Front Range, USA. We use fifty-two ¹⁴C ages collected along four streams prior to the flood to estimate mean residence time of...
Data
Uncalibrated and calibrated radiocarbon ages of charcoal fragments from fine floodplain sediment and study site characteristics from North Saint Vrain Creek and Rocky Mountatin National Park, Wild Basin in northern Colorado, United States. Also included are GIS shapefiles and output data from geomorphic change detection of lidar digital elevation m...
Article
Full-text available
The natural wood regime forms the third leg of a tripod of physical processes that supports river science and management, along with the natural flow and sediment regimes. The wood regime consists of wood recruitment, transport, and storage in river corridors. Each of these components can be characterized in terms of magnitude, frequency, rate, tim...
Article
Although there have been studies on changes to hydrology in permafrost regions and exports of nutrients and organic matter to the Arctic Ocean, little is known about how geomorphic dynamics of rivers in permafrost regions will change in the future under a warming climate and the effects of those changes on floodplains. We focus on river dynamics in...
Article
Full-text available
High-latitude permafrost regions store large stocks of soil organic carbon (OC), which are vulnerable to climate warming. Estimates of subsurface carbon stocks do not take into account floodplains as unique landscape units that mediate and influence the delivery of materials into river networks. We estimate floodplain soil OC stocks within the acti...
Article
Full-text available
Inorganic sediment is not the only solid-fraction component of river flows; flows may also carry significant amounts of large organic material (i.e., large wood), but the characteristics of these wood-laden flows (WLF) are not well understood yet. With the aim to shed light on these relatively unexamined phenomena, we collected home videos showing...
Article
Extreme storms in forested environments commonly increase inputs of coarse particulate organic matter (CPOM) and large wood (LW) to streams. Protruding boulders and bedforms, mid‐channel bars, and standing trees can trap CPOM and LW. These organic accumulations can become large enough to span the bankfull channel width, or the accumulations can be...
Article
Full-text available
River beads refer to retention zones within a river network that typically occur within wider, lower gradient segments of the river valley. In lowland, floodplain rivers that have been channelized and leveed, beads can also be segments of the river in which engineering has not reduced lateral channel mobility and channel-floodplain connectivity. De...
Article
Full-text available
River networks modify material transfer from land to ocean. Understanding the factors regulating this function for different gaseous, dissolved, and particulate constituents is critical to quantify the local and global effects of climate and land use change. We propose the River Network Saturation (RNS) concept as a generalization of how river netw...
Article
During the past 50 yr, the number and variety of papers written by U.S. fluvial geomorphologists that examine human alterations of rivers has accelerated substantially. From an initial focus primarily on how human-induced changes in land cover influence sediment yield and river dynamics, the literature has expanded to emphasize the effects of flow...
Article
Full-text available
Mountain rivers have the potential to retain OC-rich soil and store large quantities of organic carbon (OC) in floodplain soils. We characterize valley bottom morphology, floodplain soil, and vegetation in two disparate mountain river basins: the Middle Fork Snoqualmie in the Cascade Mountains and the Big Sandy in the Wind River Range of the Rocky...
Preprint
Wood in rivers creates habitat, shapes the morphology of valley bottoms, and acts as a pool of organic carbon (OC). Effective riverine wood management depends on a robust understanding of the spatial distribution of wood throughout river networks. This motivates the analysis of wood load in relation to both reach- and basin-scale processes. We pres...
Preprint
Carbon stored on the land has the potential to be released to the atmosphere and act as a greenhouse gas, influencing global climate. To predict future climate, it is imperative to understand where and how much carbon is stored across the landscape to understand how much carbon might be released to and/or sequestered from the atmosphere in the futu...
Preprint
Wood jams in rivers and on floodplains play an essential role in shaping valley bottoms. Jams are inherently complex and difficult to measure, and collecting data on wood jam dynamics during high flows is complicated by the recurrence interval between flows that measurably change or mobilize a jam. We present the Wood Jam Dynamics Database and Asse...
Article
Full-text available
Organic material (i.e., trees, branches, wood in general) is commonly neglected among the classical criteria to distinguish flow types, mostly due to the lack of direct observations of flows in which this load is significant. However, in forested basins, large amounts of wood can be transported. Here we define and characterize, for the first time,...
Article
Full-text available
Beavers are widely recognized as ecosystem engineers for their ability to shape river corridors by building dams, digging small canals, and altering riparian vegetation. Through these activities, beavers create beaver meadows, which are segments of river corridor characterized by high geomorphic heterogeneity, attenuation of downstream fluxes, and...
Preprint
Fractures are discontinuities in rock that can be exploited by erosion. Fractures regulate cohesion, profoundly affecting the rate, style, and location of Earth surface processes. By modulating the spatial distribution of erodibility, fractures can focus erosion and set the shape of features from scales of fluvial bedforms to entire landscapes. Alt...
Article
Western U.S. rivers are currently influenced by legacy effects of reduced large wood (LW) loading and retention that has substantially reduced in‐stream habitat complexity. Large wood is typically associated with streams in undisturbed old‐growth forest and in the correct geomorphic context can drastically alter stream and valley habitat complexity...
Article
Wood in rivers creates habitat, shapes the morphology of valley bottoms, and acts as a pool of organic carbon (OC). Effective riverine wood management depends on a robust understanding of the spatial distribution of wood throughout river networks. This motivates the analysis of wood load in relation to both reach- and basin-scale processes. We pres...
Article
Fractures are discontinuities in rock that can be exploited by erosion. Fractures regulate cohesion, profoundly affecting the rate, style, and location of Earth surface processes. By modulating the spatial distribution of erodibility, fractures can focus erosion and set the shape of features from scales of fluvial bedforms to entire landscapes. Alt...