Ellen Wohl

Colorado State University | CSU · Department of Geosciences

We use the five landscape ecology metrics of aggregation index, percentage of like adjacencies, interspersion and juxtaposition index, patch density, and Shannon’s evenness index to assess spatial heterogeneity at 15 floodplains in the continental United States. Assessments are based on floodplain classes and patches delineated remotely using topog...

River corridors along non‐perennial stream networks provide diverse physical and ecological functions that are thought to be related to the spatial and temporal variability of geomorphic units, also known as geomorphic heterogeneity. While studies on the characteristics and drivers of geomorphic heterogeneity have been developed in perennial stream...

Floodplain restoration can enhance the capacity for carbon sequestration by facilitating higher water tables, deposition of fine sediment, and increased input and residence time of organic matter. We measured floodplain soil organic carbon stocks in nine stream restoration projects across the western United States and compared them to nearby degrad...

River corridors integrate the active channels, geomorphic floodplain and riparian areas, and hyporheic zone while receiving inputs from the uplands and groundwater and exchanging mass and energy with the atmosphere. Here, we trace the development of the contemporary understanding of river corridors from the perspectives of geomorphology, hydrology,...

Accumulations of wood in rivers can alter three-dimensional connectivity and facilitate channel bifurcations. Bifurcations divide the flow of water and sediment into secondary channels and are a key component of anastomosing rivers. While past studies illustrate the basic scenarios in which bifurcations can occur in anastomosing rivers, understandi...

Plain Language Summary The Arctic is warming rapidly, and this can increase landscape erosion. Consequently, carbon can be transferred into rivers and transported toward the Arctic Ocean. To date, work has tracked finer material dissolved in river water and the size of sand grains but has missed large pieces of wood that fall or slide into rivers....

Floodplain restoration can enhance capacity for carbon sequestration by facilitating higher water tables, deposition of fine sediment, and increased input and residence time of organic matter. We measured floodplain soil organic carbon stocks in nine stream restoration projects across the western United States and compared them to nearby degraded a...

Alteration to the sediment supply of fluvial channels is well understood to trigger morphological adjustment, but the particularities and peculiarities that arise in any specific situation – the magnitude and direction of change that occurs in response to a given sediment supply modification – have long complicated broad conceptualizations of chann...

Logjams in a stream create backwater conditions and locally force water to flow through the streambed, creating zones of transient storage within the surface and subsurface of a stream. We investigate the relative importance of logjam distribution density, logjam permeability, and discharge on transient storage in a simplified experimental channel....

Large wood is inherently mobile in naturally functioning river corridors, yet river management commonly introduces wood that is anchored to limit hazards. Wood that is periodically mobilized is important for: replacing stationary large wood that performs diverse physical and ecological functions; contributing to the disturbance regime of the river...

Floodplains provide numerous ecosystem services that depend on the spatial heterogeneity, or patchiness, of the floodplain. Direct and indirect human alterations of rivers can reduce floodplain heterogeneity and function, but relatively little is known of patterns of floodplain heterogeneity in natural, fully functional floodplains. We quantify flo...

The Interim Draft National OHWM Manual provides draft technical guidance for identifying and delineating the OHWM using a scientifically supported, rapid framework. The OHWM defines the lateral extent of U.S. Army Corps of Engineers’ (USACE) jurisdiction of non-tidal aquatic resources such as streams, rivers, and lakes in the U.S., and provides USA...

Prompted by field observation of an aufeis‐induced channel avulsion along the Hula Hula River in June 2021, we use measurements of channel migration zone width along 15 rivers flowing north across the Arctic coastal plain in Alaska, USA. We differentiated sites with aufeis that covered ≥1 km² in early summer during the period 2017–2021 from sites w...

The lack of watershed-scale estimates of floodplain carbon stocks limits recognition of the important role of floodplains and river corridor restoration in efforts to enhance carbon sequestration. We use the South Platte River watershed of Colorado, USA as a case study to illustrate spatial patterns of, and controls on, floodplain carbon stocks at...

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...

In this article we describe the natural hydrogeomorphological and biogeochemical cycles of dryland fluvial ecosystems that make them unique, yet vulnerable to land use activities and climate change. We introduce Natural Infrastructure in Dryland Streams (NIDS), which are structures naturally or anthropogenically created from earth, wood, debris, or...

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...

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...

Artificial levees are a major human modification of river corridors, but we still do not have a clear understanding of how artificial levees affect floodplain extent at regional and larger scales. We estimated changes in river-floodplain connectivity due to artificial levees in the contiguous United States (CONUS) using a combination of artificial...

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...

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...

Despite the recognition of floodplain importance in the scientific community, floodplains are not afforded the same legal protection as river channels. In the United States alone, flood-related economic losses were much higher in the second half of the 20th century than the first half despite the expenditure of billions of dollars on flood defenses...

Artificial levees are anthropogenic structures designed to hydrologically disconnect rivers from floodplains. The extent of artificial levees in the contiguous United States (CONUS) is unknown. To better estimate the distribution of artificial levees, we tested several different geomorphic, land cover, and spatial variables developed from the Natio...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

Floodplain storage of water, nutrients, and sediment is critical to sustaining river ecosystems but has been reduced by human activities.

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...

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...

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...

Sediment waves, a term that describes the fluvial transport of a discrete sediment influx, have been studied in regard to channel response to infrequent catastrophic events, such as mass movements or dam removal. However, few researchers have studied (1) the potential presence of sediment waves of annual or sub-annual scale in mixed eolian-fluvial...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

Connectivity refers to the degree to which materials and organisms can move between components of a geomorphic system such as a drainage basin or mountain range. Geomorphic systems can be represented as networks with compartments, links, and nodes that exhibit connectivity at differing spatial and temporal scales. Although connectivity can be diffi...

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...

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.

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...

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...

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...

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...

By late April, the snow is gone from the beaver meadow. The promises of March are starting to be fulfilled: insects are on the wing, some of the willows have furry catkins along their branches, and fish jump from the quiet waters of the beaver ponds. I can no longer easily get around the beaver meadows on foot unless I wear chest waders. The sound...

February: when I first notice the days begin to stretch out after the tight curl of December and January. February: the month for creating new beavers. Somewhere sheltered from the cold light of sun reflecting off snow, in a bank den or a lodge, perhaps even in the water, the beavers are mating. The North St. Vrain beaver meadow is good habitat, an...

Just when spring appears to have arrived, a late-season storm blows down from the north. Despite the overcast sky, the temperature at first is beguilingly warm. Rain starts to fall, then changes to sleet as the temperature drops. “Rough winds do shake the darling buds of May,” indeed. The sleet becomes graupel—crusty, rounded pellets of snow—and th...

By mid-July, abundant water continues to move in all directions within the beaver meadow. Water flows noisily down the main channel, creating deep pools where it mixes with water entering from secondary channels. Deeper waters well up from beneath overhung banks and the willow stems along the banks remain partly submerged. Pieces of driftwood colle...

There is a place, about a mile long by a thousand feet wide, that lies in the heart of the Southern Rocky Mountains in Colorado. Here at the eastern margin of Rocky Mountain National Park, along a creek known as North St. Vrain, everything comes together to create a bead strung along the thread of the creek. The bead is a wider portion of the valle...

At the nadir of the year, this is how morning comes to the beaver meadow. Just as the sun rises above the eastern horizon, a flush of pale rose lights the snow newly fallen on the highest peaks. The beaver meadow remains in shadow, silent but for the creek flowing quietly between its rims of ice. The air temperature is well below freezing and frost...

By mid-March, daytime temperatures above freezing have left muddy puddles all over the unpaved road that runs above and beside the beaver meadow. This road extends to the national park trailhead farther upstream but is now closed for winter. I enter the beaver meadow on a lightly overcast day that is windy, as I expect March to be. Lack of recent s...

By mid-October, the first snow has fallen on the beaver meadow. There is no sign of snow when I visit a few days later, but the air feels chill in the shadows and a cool breeze leavens the sunshine’s warmth. Mostly, the beaver meadow seems a golden place. Many of the willow, aspen, and birch leaves have already fallen, but enough remain to create a...

The ability of beavers to create an abundant habitat for a diverse array of plants and animals has been analyzed time and again. The disappearance of beavers across the northern hemisphere, and what this effects, has yet to be comprehensively studied. Saving the Dammed analyzes the beneficial role of beavers and their dams in the ecosystem of a riv...

Emily Dickinson wrote a lovely poem using a brook as a metaphor for one’s interior life. The poem includes the lines: . . . And later, in August it may be, When the meadows parching lie, Beware lest this little brook of life Some burning noon go dry! . . . No chance of the little brook going dry if it runs through a beaver meadow. The movement of w...

By late November, snow covers much of the beaver meadow. I visit on a sunny day well above freezing, but the low-angle light comes with long, long shadows. The meadow is noisy with continuously rushing wind that keeps the bare willow branches swaying and sculpts the snow on the lee side of plants into streamlined mounds. Individual grass stems have...

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...

Legacies are persistent changes in natural systems resulting from human