More Like this

1. Predicting Head Loss and Hydraulic Roughness of Channel‐Spanning Large Wood Jams

   https://doi.org/10.1029/2026GL122411  

   Hahn, Aleah; Morrison, Ryan R; Triantafillou, Shayla; Wohl, Ellen (May 2026, Geophysical Research Letters)

   Log jams enhance hydraulic and geomorphic diversity in river corridors. Channel‐spanning log jams induce backwatering, increase local flow heterogeneity, promote sediment deposition, and improve aquatic habitat diversity. Despite their increasing popularity in river restoration, predicting their hydraulic effects remains a challenge. We developed a model to predict dimensionless head loss through log jams for sub‐bankfull flows as traditional backwater methods are limited in variable natural channels. We developed the model from historical flume studies and tested the model application on field data from natural jams. As solid volume fraction increased, we found that dimensionless head loss also increased. Field application of our model successfully predicted head loss in naturally occurring log jams. Roughness values (Manning's and Darcy‐Weisbach ) varied but generally decreased with increased unit discharge. Our approach for determining head loss and roughness allows for better prediction and design of the localized hydraulic impacts of log jams. 

   more » « less
2. Assessing Channel Bank‐Height Adjustments and Flood Frequency Trends in a Dynamic Channel‐Levee Evolution Model

   https://doi.org/10.1029/2024JF008137  

   Han, J; Kim, W; Edmonds, D A (March 2025, Journal of Geophysical Research: Earth Surface)

   Abstract Natural levees form through sediment delivery from channels, dispersal onto floodplains, and storage at channel margins. When levees breach, they release water and sediment onto the floodplain, occasionally causing river avulsions. Despite their significance, levee growth remains poorly understood, and no existing models capture the dynamic channel‐levee evolution systems. A common assumption is that levee and channel bed aggradation rates are coupled or equal; however, this cannot be true because levees do not accumulate everywhere along aggrading channel belts. Using a one‐dimensional numerical model, we investigate levee growth decoupled from channel bed aggradation under flood scenarios wherein the flooded level: (a) exceeds the levee crest height (i.e., front loading); or (b) is lower than the levee crest partially inundating distal levee deposits (i.e., back loading). Front loading events initially aggrade the levee crest, which confines the channel, increases bankfull depth, and reduces flooding. During confinement, levee growth restricts flooding, and minor back loading events are more common. Over this period, the channel bed aggrades until bankfull depth decreases sufficiently to trigger larger floods. This channel‐releasing process increases flood likelihood and enhances overbank accumulation, promoting front loading and re‐confining the channel. Our findings suggest aggradational channels may experience confined‐release phases characterized by episodic levee growth and fluctuating bankfull depth. Rapid in‐channel aggradation increases flood frequency and variability with more confined‐release cycles. These results imply that river avulsions and associated floods might preferentially occur when the channel bed aggrades faster than adjacent levees, whereby the channel becomes shallower and destabilized. 

   more » « less
3. Hydrogeomorphic response of steep streams following severe wildfire in the Western cascades, Oregon

   https://doi.org/10.1002/esp.5982  

   Busby, David M; Wilcox, Andrew C (October 2024, Earth Surface Processes and Landforms)

   Severe wildfire may alter steep mountain streams by increasing peak discharges, elevating sediment and wood inputs into channels, and increasing susceptibility to landslides and debris flows. In the Pacific Northwest, where mean annual precipitation is high and mean fire‐return intervals range from decades to centuries, understanding of steep stream response to fire is limited. We evaluate the hydrologic and geomorphic response of ~100‐m‐long steep stream reaches to the large‐scale and severe 2020 fires in the Western Cascade Range, Oregon. In the two runoff seasons after the fires, peak flows in burned reaches were below the 2‐year recurrence interval flood, a level sufficient to mobilize the median grain size of bed material, but not large enough to mobilize coarser material and reorganize channel morphology. Sediment inputs to study streams consisted of two road‐fill failure landslides, slumps, sheetwash, and minor bank erosion; precipitation thresholds to trigger debris flows were not exceeded in our sites. There was a 50% increase in the number of large wood pieces in burned reaches after the fires. Changes in fluxes of water, sediment, and wood induced shifts in the balance of sediment supply to transport capacity, initiating a sequence of sediment aggradation and bed‐material fining followed by erosion and bed‐material coarsening. Gross channel form showed resilience to change, and an unburned reference reach exhibited little morphologic change. Post‐fire recruitment of large wood will likely have long‐term implications for channel morphology and habitat heterogeneity. Below‐average precipitation during the study period, combined with an absence of extreme precipitation events, was an important control on channel responses. Climate change may have a complex effect on stream response to wildfire by increasing the propensity for both drought and extreme rain events and by altering vegetation recovery patterns. 

   more » « less
4. The floodplain wood budget: Linking wood dynamics and ecogeomorphic processes

   https://doi.org/10.1002/esp.70244  

   Lininger, Katherine B; Welsh, Josie; Ruiz‐Villanueva, Virginia (January 2026, Earth Surface Processes and Landforms)

   Abstract Und erstanding floodplain wood transport, deposition and storage is necessary to fully close wood budgets in river corridors (the channel, floodplain and hyporheic zone). However, most work on wood in river corridors has focussed on in‐channel wood. Here, we review current understanding of wood dynamics in floodplains using a floodplain wood budget to highlight the processes that change floodplain wood storage. We discuss autochthonous and hillslope recruitment to the floodplain, floodplain wood decay and burial/exhumation, controls on lateral wood fluxes between the floodplain and the channel, and fluvial wood transport within the floodplain itself. We compile wood load data for floodplains and channels in locations in which data on floodplain wood loads exist, finding that floodplains are an important storage location for wood within the river corridor across diverse environments. We briefly review the impacts of floodplain wood on physical and ecological processes and then summarise important knowledge gaps that limit understanding of floodplain wood dynamics. We emphasise that future research should address methods to determine wood piece source location and track wood within the river corridor; mechanistically explore coupled flow‐sediment‐vegetation‐wood processes across spatial and temporal scales; extend observations of floodplain wood loads and storage characteristics and explore multiple size classes of organic matter; and work to inform management decisions related to floodplain wood. Because it may be less likely to be transported downstream and interact with infrastructure, floodplain wood may be less hazardous than in‐channel wood but can still provide ecological benefits and enhance physical complexity. Improving our understanding of wood dynamics on floodplains is thus important for supporting river management. 

   more » « less
5. Quantifying bankfull flow width using preserved bar clinoforms from fluvial strata

   https://doi.org/10.1130/G48729.1  

   Greenberg, Evan; Ganti, Vamsi; Hajek, Elizabeth (May 2021, Geology)

   Abstract Reconstruction of active channel geometry from fluvial strata is critical to constrain the water and sediment fluxes in ancient terrestrial landscapes. Robust methods—grounded in extensive field observations, numerical simulations, and physical experiments—exist for estimating the bankfull flow depth and channel-bed slope from preserved deposits; however, we lack similar tools to quantify bankfull channel widths. We combined high-resolution lidar data from 134 meander bends across 11 rivers that span over two orders of magnitude in size to develop a robust, empirical relation between the bankfull channel width and channel-bar clinoform width (relict stratigraphic surfaces of bank-attached channel bars). We parameterized the bar cross-sectional shape using a two-parameter sigmoid, defining bar width as the cross-stream distance between 95% of the asymptotes of the fit sigmoid. We combined this objective definition of the bar width with Bayesian linear regression analysis to show that the measured bankfull flow width is 2.34 ± 0.13 times the channel-bar width. We validated our model using field measurements of channel-bar and bankfull flow widths of meandering rivers that span all climate zones (R2 = 0.79) and concurrent measurements of channel-bar clinoform width and mud-plug width in fluvial strata (R2 = 0.80). We also show that the transverse bed slopes of bars are inversely correlated with bend curvature, consistent with theory. Results provide a simple, usable metric to derive paleochannel width from preserved bar clinoforms. 

   more » « less