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In a warming climate, an intensifying fire regime and higher likelihood of extreme rain are expected to increase watershed sediment yield in many regions. Understanding regional variability in landscape response to fire and post‐fire rainfall is essential for managing water resources and infrastructure. We measured sediment yield resulting from sequential wildfire and extreme rain and flooding in the upper Carmel River watershed (116 km2), on the central California coast, USA, using changes in sediment volume mapped in a reservoir. We determined that the sediment yield after fire and post‐fire flooding was 854–1,100 t/km2/yr, a factor of 3.5–4.6 greater than the long‐term yield from this watershed and more than an order of magnitude greater than during severe drought conditions. In this first large‐scale field validation test of the WEPPcloud/wepppy framework for the Water Erosion Prediction Project (WEPP) model on a burned landscape, WEPP predicted 81%–106% of the measured sediment yield. These findings will facilitate assessing and predicting future fire effects in steep watersheds with a Mediterranean climate and indicate that the increasingly widespread use of WEPP is appropriate for evaluating post‐fire hillslope erosion even across 100‐km2 scales under conditions without debris flows. Plain Language Summary: In a warming climate, more wildfire and more extreme rain will cause more erosion, producing more sediment that will be carried downstream by rivers. Understanding how much sediment a landscape produces after fire and extreme rain is essential for managing water resources and infrastructure, because sediment fills up storage space in reservoirs and can interfere with proper functioning of water systems and roads. We measured how much sediment was produced in a watershed due to wildfire followed by extreme rain and flooding, studying the Carmel River on the central California coast, USA. We evaluated how much sediment this watershed produced by measuring the volume of sediment deposited within a reservoir that the watershed drains into. We determined that the rate of sediment exported from the study watershed due to a large fire and post‐fire floods was much greater than the long‐term rate there. Having compared our results with the amount of sediment predicted by a model called the Water Erosion Prediction Project model, we found that the model performed well and realistically predicted the amount of sediment that this landscape would shed. These findings will facilitate assessing and predicting future fire effects in steep watersheds with a Mediterranean‐type climate. Key Points: A 116‐km2 central California watershed produced sediment yield of 854–1,100 t/km2/yr in the first year after a fire and extreme rainPost‐fire sediment yield in an extremely wet year without debris flows was 3.5–4.6 times greater than the long‐term rateThe Water Erosion Prediction Project model predicted 81%–106% of the measured post‐fire sediment eroded from hillslopes [ABSTRACT FROM AUTHOR]

Editors of the Journal of Geophysical Research—Earth Surface express their appreciation to those who served as peer reviewers for the journal in 2023. Key Points: The editors thank the 2023 peer reviewers of JGR—Earth Surface [ABSTRACT FROM AUTHOR]

The failure of a 144‐m‐high lava‐dam waterfall on the Río Coca, Ecuador, in February 2020 initiated a catastrophic watershed reset—regressive erosion upstream and a massive sediment pulse downstream—as the river evolves towards a new equilibrium grade. The evolution of this river corridor after a sudden base‐level fall embodies the "complex response" concepts long understood through laboratory experiments, numerical modelling and smaller‐scale field studies, but that have not been observed in the field before on this scale. This paper presents geomorphic and geotechnical data to characterize the evolution of the Río Coca since 2020. In the three years after the lava‐dam failure, the erosion front migrated almost 13 km upstream along the mainstem river and triggered secondary headcuts that began migrating up tributaries. Erosion of the mainstem and tributary valleys generated a sediment pulse estimated to be 277 million m3 and ~500 million tonnes (Mt) over three years, depositing sediment tens of meters thick over tens of kilometres downstream from the former waterfall. This sediment pulse is one of the largest in modern times, comparable to the annual sediment load of a major continent‐draining river but with orders‐of‐magnitude greater sediment yield. Geomorphic adjustment of the Río Coca represents a highly unusual natural disaster threatening life, property, water quality, the regional economy, major infrastructure and energy security. However, this event also provides a rare opportunity to learn how a large autogenic watershed disturbance and recovery evolve, with important lessons for interpreting the sedimentary record of volcanic landscapes. [ABSTRACT FROM AUTHOR]

December 2023 marks the 20th anniversary of the first issue of the Journal of Geophysical Research: Earth Surface. The past 20 years have brought rapid growth in the field of Earth‐surface processes, changes in AGU's structure and objectives, and new practices across the scientific publishing landscape. In recent years our mission has evolved to focus increasingly on science for the benefit of society and the global environment. The growth and diversification of the international Earth‐surface scientific community has enriched the science immeasurably, and we continue to reach out to scientists in parts of the globe that have remained under‐represented in the scientific literature. JGR Earth Surface strives to provide peer review that is rigorous, constructive, efficient, and with an increasing emphasis on also being civil and free of bias. As preferences and practices for publishing science change, the journal explores new opportunities, including publishing rigorous, insightful case studies and leading cross‐journal Special Collections. The Editorial Board thanks AGU for 20 years of support and the Earth‐surface scientific community for their continued dedication to moving our field forward. Key Points: JGR Earth Surface editors look back on the first 20 years of this journalOur field, AGU, and the publishing landscape continue to change, and the journal adapts to continue distributing rigorous, impactful scienceThe journal reaches out to scientists in parts of the globe that have remained understudied, to achieve an improved geographical coverage in the future [ABSTRACT FROM AUTHOR]

The steep, tectonically active terrain along the Central California (USA) coast is well known to produce deadly and destructive debris flows. However, the extent to which fire affects debris-flow susceptibility in this region is an open question. We documented the occurrence of postfire debris floods and flows following the landfall of a storm that delivered intense rainfall across multiple burn areas. We used this inventory to evaluate the predictive performance of the US Geological Survey M1 likelihood model, a tool that presently underlies the emergency assessment of postfire debris-flow hazards in the western USA. To test model performance, we used the threat score skill statistic and found that the rainfall thresholds estimated by the M1 model for the Central California coast performed similarly to training (Southern California) and testing (Intermountain West) data associated with the original model calibration. Model performance decreased when differentiating between "minor" and "major" postfire hydrologic response types, which weigh effects on human life and infrastructure. Our results underscore that the problem of false positives is a major challenge for developing accurate rainfall thresholds for the occurrence of postfire debris flows. As wildfire activity increases throughout the western USA, so too will the demand for the assessment of postfire debris-flow hazards. We conclude that additional collection of field-verified inventories of postfire hydrologic response will be critical to prioritize which model variables may be suitable candidates for regional calibration or replacement. [ABSTRACT FROM AUTHOR]

The summer of 2023 is a notable time for water‐resource management in the western United States: Glen Canyon Dam, on the Colorado River, turns 60 years old while the largest dam‐removal project in history is beginning on the Klamath River. This commentary discusses these events in the context of a changing paradigm for dam and reservoir management in this region. Since the era of large dam building began to wane six decades ago, new challenges have arisen for dam and reservoir management owing to climate change, population increase, reservoir sedimentation, declining safety of aging dams, and more environmentally focused management objectives. Today we also better understand dams' benefits, costs, and environmental impacts, including some that were unforeseen and took decades to become apparent. Where dams have become unsafe, obsolete (e.g., due to excessive reservoir sedimentation), and uneconomical beyond saving, dam removal has become common. The science and practice of dam removal are accelerating rapidly, and some long‐term physical and biological response studies are now available. Removal of four hydroelectric dams on the Klamath River will be a larger and more complex project than any previous dam removal. The imminency of this project reflects a very different situation for dam and reservoir management than 60 years ago. Looking forward, dam and reservoir management in the western United States and worldwide will require continued collaboration and innovative thinking to meet a wide range of objectives and to manage water resources sustainably for future generations. Plain Language Summary: The summer of 2023 marks an important moment for water‐resource management in the western U.S.: Glen Canyon Dam, one of the last and largest dams built on the Colorado River, turned 60 years old and the largest dam‐removal project in history began on the Klamath River. This commentary discusses these events in the context of a changing paradigm for dam and reservoir management. Substantial challenges exist for dam and reservoir management today owing to climate change, reservoirs filling with sediment, aging infrastructure, increasing population and water demands, and environmental compliance. We also better understand dams' benefits, costs, and environmental impacts. Where dams are unsafe, obsolete, and uneconomical beyond saving, dam removal is now common. The science and practice of dam removal are accelerating rapidly, with long‐term studies available on physical and biological responses. Removal of four hydroelectric dams on the Klamath River will be a larger, more complex project than any previous dam removal, reflecting a very different situation for dam and reservoir management today than 60 years ago. In the western U.S. and worldwide, dam and reservoir management requires greater collaboration and innovative thinking to meet a wide range of objectives and sustainably manage water resources for future generations. Key Points: Dam and reservoir management is evolving due to climate change, sedimentation, aging infrastructure, and changing management objectivesGlen Canyon Dam turns 60 years old amid greater knowledge of balancing dam operations with downstream resource protection and managementDam‐removal effects are now also better understood and the largest dam removal yet, on the Klamath River, is imminent [ABSTRACT FROM AUTHOR]

Measuring river response to dam removal affords a rare, important opportunity to study fluvial response to sediment pulses on a large field scale. We present a before–after/control–impact study of the Carmel River, California, measuring fluvial geomorphic and grain‐size evolution over 8 years, six of which postdated removal of a 32 m‐high dam (one of the largest dams removed worldwide) and included 11 flow events exceeding the 2‐year flood magnitude. We find that the reservoir‐sediment pulse following dam removal was relatively small (97 000 ± 24 000 t over 4 years), owing to deliberate reservoir‐sediment stabilization. Scaled to the size of the Carmel River watershed and compared against long‐term bedrock denudation rates, the post‐dam‐removal sediment release was slightly less than the annualized long‐term sediment export from this basin. New sediment transited >30 km to the river mouth in less than 2 years, assisted by floods 2 and 4 years after dam removal. The sediment pulse fined the downstream riverbed while causing mostly low‐magnitude bed‐elevation changes: commonly 0.5 to 1 m or smaller, occurring as discontinuous sediment patches or interstitial deposits, aside from the filling and subsequent partial scour of deep pools. There was no major geomorphic reset downstream from the dam site. Geomorphic changes were driven almost entirely by flow rather than by the modest increase in sediment supply, in contrast to recent examples from other large dam removals. The relatively minor disturbance caused by dam removal on the Carmel River is likely analogous to many future dam removals: a relatively small sediment pulse after deliberate limitation of reservoir‐sediment erosion, and with an upstream dam remaining in place. Thus, a large dam removal need not lead to major downstream impacts. [ABSTRACT FROM AUTHOR]

Members of the editorial board of the Journal of Geophysical Research—Earth Surface express their appreciation to those who served as peer reviewers for this journal in 2022. Plain Language Summary: Editors of the Journal of Geophysical Research—Earth Surface express their appreciation to those who served as peer reviewers for the journal in 2022. Key Points: The editors thank the 2022 peer reviewers [ABSTRACT FROM AUTHOR]

Increasing wildfire and declining snowpacks in mountain regions threaten water availability. We combine satellite‐based fire detections with snow seasonality classifications to examine fire activity in California's seasonal and ephemeral snow zones. We find a nearly tenfold increase in fire activity during 2020–2021 versus 2001–2019. Accumulation season broadband snow albedo declined 25%–71% at two burned sites (2021 and 2022) according to in‐situ data relative to un‐burned conditions, with greater declines associated with increased burn severity. By enhancing snowpack susceptibility to melt, both decreased snow albedo and canopy drove midwinter melt during a multi‐week dry spell in 2022. Despite similar meteorological conditions in December–February 2013 and 2022–linked to persistent high pressure weather regimes–minimal melt occurred in 2013. Post‐fire snowpack differences are confirmed with satellite measurements. With growing geographical overlap between wildfire and snow, our findings suggest California's snowpack is increasingly vulnerable to the compounding effects of dry spells and wildfire. Plain Language Summary: Satellite fire detections indicate substantial increases in wildfire activity in California's snow‐covered landscapes during 2020 and 2021, suggesting wildfire is increasingly altering mountain hydrology. During 2022, a multi‐week mid‐winter drought, or dry spell, occurred. A meteorologically‐similar dry spell occurred in 2013, and the 2022 event provides a test case to examine how post‐fire changes (canopy loss and deposition of burned dark material on snowpack) alter snowmelt patterns. Using field observations, weather station data, and satellite remote sensing of snow, we find large reductions in snow albedo and canopy cover drove rapid melt during the 2022 dry spell in burned areas whereas during 2013, minimal melt occurred. The societal connection between mountains and humans will be strained as mountains face increasing climate‐related stressors. Midwinter drought, snow loss, and increasing wildfire are expectations of a warming world. Addressing these challenges requires innovative water and forest management paradigms. Our findings motivate additional research into assessing and planning for post‐fire hydrologic changes in snow‐dominated landscapes as both wildfire and dry spells will increase in frequency with climate warming. Key Points: A 9.8x increase in satellite fire detections in California's snow zones in 2020–2021 versus 2001–2019 implies growing overlap in fire and snowPost‐fire accumulation season broadband snow albedo declined 25%–71%, driving fewer snow‐covered days and lower snow‐cover fractionCompared with the meteorologically similar 2013 dry spell, albedo and canopy declines led to rapid midwinter melt in 2022 [ABSTRACT FROM AUTHOR]

Ongoing sea-level rise has brought renewed focus on terrestrial sediment supply to the coast because of its strong influence on whether and how long beaches, marshes and other coastal landforms may persist into the future. Here, we summarise findings of sediment discharge from several coastal rivers, revealing that infrequent, large-magnitude events have disproportionate influence on the morphodynamics of coastal landforms and littoral cells. These eventdominated effects are most pronounced for small, steep mountainous rivers that supply beach and wetland sediment along the world's active tectonic margins, although infrequent events are important drivers of sediment discharge for rivers worldwide. Additionally, extreme events (recurrence intervals of decades to centuries) that follow wildfires, earthquakes, volcanic eruptions, extreme precipitation or - most notably - combinations of these factors can redefine coastal sediment budgets and morphology. Some of these extreme events (e.g., wildfires plus rainfall) are increasing in magnitude and frequency under modern climate warming, with the likely result of increasing sediment flux to affected coastlines. Climate change is also altering watershed processes in both high latitudes and high altitudes, resulting in increased sediment supply to downstream catchments. We conclude that sediment inputs to coastal systems are highly variable with time, and that the variability and trends in sediment input are as important to characterise as long-term averages. [ABSTRACT FROM AUTHOR]

Today, climate change is affecting virtually all terrestrial and nearshore settings. This commentary discusses the challenges of measuring climate‐driven physical landscape responses to modern global warming: short and incomplete data records, land use and seismicity masking climatic effects, biases in data availability and resolution, and signal attenuation in sedimentary systems. We identify opportunities to learn from historical and paleo data, select especially sensitive study sites, and report null results to better characterize the extent and nuances of climate‐change effects. We then discuss efforts to improve attribution practices, which will lead to better predictive capabilities. We encourage the Earth‐science community to prioritize scientific research on climate‐driven physical landscape changes so that societies will be better prepared to manage the effects on health and safety, infrastructure, water–food–energy security, economics, and ecosystems that follow from climate‐driven physical landscape change. Plain Language Summary: Modern global warming will ultimately affect physical landscape processes virtually everywhere on Earth, and some of those effects are evident already. This commentary describes the challenges to measuring climate‐driven physical landscape responses to global warming: short and incomplete data records, land use and earthquakes masking climatic effects, biases in data availability and resolution, and climate signals becoming harder to read at the downstream end of a landscape. We discuss ways to collect more informative data in key locations to better understand climate‐change impacts, while also diligently reporting where impacts are not evident. Forming a more complete picture in these ways will mean societies are better prepared to predict and manage impacts on human health and safety, infrastructure, water–food–energy security, economics, and ecosystems that are linked to climate‐driven physical landscape change. Key Points: Modern anthropogenic climate change affects a vast range of geomorphic settingsWe identify challenges of measuring physical landscape response to modern climate change and opportunities to improve studiesBetter understanding physical landscape impacts will prepare societies to manage hazards and economic effects of climate change [ABSTRACT FROM AUTHOR]

The Editors of the Journal of Geophysical Research—Earth Surface express their appreciation to those who served as peer reviewers for the journal in 2021, and explain the newly formalized opportunity for early‐career scientists to co‐review manuscripts. Plain Language Summary: Editors of the Journal of Geophysical Research—Earth Surface express their appreciation to those who served as peer reviewers for the journal in 2021, and explain the newly formalized opportunity for early‐career scientists to co‐review manuscripts. The new co‐reviewing functionality allows an invited reviewer to include and recognize one or two early‐career co‐reviewers who contribute comments on a manuscript. Co‐reviewing of manuscripts by students, postdoctoral scholars, and other early‐career scientists is encouraged, in order to enhance these scientists' reviewing skills and to broaden the diversity of perspectives in the journal's review process. Key Points: The editors thank the 2021 peer reviewersCo‐reviewing protocols are explained and encouraged [ABSTRACT FROM AUTHOR]

Floods play a critical role in geomorphic change, but whether peak magnitude, duration, volume, or frequency determines the resulting magnitude of erosion and deposition is a question often proposed in geomorphic effectiveness studies. This study investigated that question using digital elevation model differencing to compare and contrast three hydrologically distinct epochs of topographic change spanning 18 years in the 37‐km gravel–cobble lower Yuba River in northern California, USA. Scour and fill were analysed by volume at segment and geomorphic reach scales. Each epoch's hydrology was characterized using 15‐min and daily averaged flow to obtain distinct peak and recurrence, duration, and volume metrics. Epochs 1 (1999–2008) and 3 (2014–2017) were wetter than average with large floods reaching 3206 and 2466 m3/s, respectively, though of different flood durations. Epoch 2 (2008–2014) was a drought period with only four brief moderate floods (peak of 1245 m3/s). Total volumetric changes showed that major geomorphic response occurred primarily during large flood events; however, total scour and net export of sediment varied greatly, with 20 times more export in epoch 3 compared to epoch 1. The key finding was that greater peak discharge was not correlated with greater net and total erosion; differences were better explained by duration and volume above floodway‐filling stage. This finding highlights the importance of considering flood duration and volume, along with peak, to assess flood magnitude in the context of flood management, frequency analysis, and resulting geomorphic changes. [ABSTRACT FROM AUTHOR]

Wildfire risk has increased in recent decades over many regions, due to warming climate and other factors. Increased sediment export from recently burned landscapes can jeopardize downstream infrastructure and water resources, but physical landscape response to fire has not been quantified for some at‐risk areas, including much of northern California, USA. We measured sediment yield from three watersheds (13–29 km2) that drain to Whiskeytown Lake, California, within the area burned by the 2018 Carr Fire. Structure‐from‐Motion photogrammetry on aerial images combined with sonar bathymetric mapping of submerged areas indicated first‐year post‐fire sediment yields of 4,080 ± 598 t/km2 (Brandy Creek), 2,700 ± 527 t/km2 (Boulder Creek), and 305 ± 58.0 t/km2 (Whiskey Creek)—some of the first post‐fire yields measured in northern California and 64, 42, and 4.8 times greater than pre‐fire yields, respectively. These were measured during a wet year and resulted largely from rilling erosion and fluvial sediment transport, without post‐fire debris flows. Rilling preferentially developed in contact with dirt roads, aided by thin soils and exposed bedrock, and on slopes vegetated by chaparral pre‐fire. The second post‐fire year (a dry year) was characterized by fluvial reworking and delta progradation of the first‐year deposits and relatively little new sediment export. First‐year sedimentation of 111,000 m3 represented minor loss of storage capacity in Whiskeytown Lake but would be detrimental to smaller reservoirs; in general, increased sediment yields from western US watersheds as fire and extreme rainfall increase will likely pose risks to water quality and storage. Plain Language Summary: Climate change is increasing wildfires across many regions, including California. Burned landscapes typically produce large amounts of sediment after a fire, which reduces water quality, decreases space for water storage in reservoirs, and sometimes produces hazardous debris flows. We investigated landscape response after the 2018 Carr Fire in northern California. Sediment yield measured in the first year after the fire (a wet year) varied among three study watersheds, ranging from one to two orders of magnitude greater than before the fire. The primary means of sediment mobilization was by water flowing over the land surface, instead of by landslides. These results will aid prediction of future fire response elsewhere in northern California, a growing research need given the increasing tendency for large fires to affect northern California. Key Points: Aerial photogrammetric and sonar bathymetric mapping quantify sediment volume change for 2 years after the major 2018 Carr Fire, CaliforniaFirst‐year post‐fire sediment yields in three watersheds were 64, 42, and 4.8 times greater than long‐term yields, some of the first post‐fire data from northern CaliforniaHillslope erosion was dominated by rilling rather than landslides; rilling commonly occurred downslope of dirt roads [ABSTRACT FROM AUTHOR]

Key Points: The editors thank the 2020 peer reviewers [ABSTRACT FROM AUTHOR]

Hydroclimatic changes associated with global warming over the past 50 years have been documented widely, but physical landscape responses are poorly understood thus far. Detecting sedimentary and geomorphic signals of modern climate change presents challenges owing to short record lengths, difficulty resolving signals in stochastic natural systems, influences of land use and tectonic activity, long‐lasting effects of individual extreme events, and variable connectivity in sediment‐routing systems. We review existing literature to investigate the nature and extent of sedimentary and geomorphic responses to modern climate change, focusing on the western United States, a region with generally high relief and high sediment yield likely to be sensitive to climatic forcing. Based on fundamental geomorphic theory and empirical evidence from other regions, we anticipate climate‐driven changes to slope stability, watershed sediment yields, fluvial morphology, and aeolian sediment mobilization in the western United States. We find evidence for recent climate‐driven changes to slope stability and increased aeolian dune and dust activity, whereas changes in sediment yields and fluvial morphology have been linked more commonly to nonclimatic drivers thus far. Detecting effects of climate change will require better understanding how landscape response scales with disturbance, how lag times and hysteresis operate within sedimentary systems, and how to distinguish the relative influence and feedbacks of superimposed disturbances. The ability to constrain geomorphic and sedimentary response to rapidly progressing climate change has widespread implications for human health and safety, infrastructure, water security, economics, and ecosystem resilience.Plain Language Summary: Climatic changes associated with global warming over the past 50 years have been documented widely, but physical landscape responses are poorly understood. Detecting landscape signals of modern climate change is difficult for many reasons but is important because these problems relate closely to human health and safety, infrastructure, water security, and ecosystems. We reviewed the scientific literature to investigate landscape responses to modern climate change in the western United States, focusing on slope failures, watershed sediment output, river shape, and wind‐blown sediment. Some changes to slope stability and wind‐blown sediment are evident, whereas factors other than climate have been more important thus far in controlling sediment output and river shape. We identify ways in which more information is needed from many more places, in the western United States and globally, to understand landscape response to ongoing climate change.Key Points: Geomorphic theory indicates that climate change will affect slope stability, sediment yield, fluvial morphology, and aeolian sediment mobilizationSome climate‐driven changes have become evident in recent decades, especially to slope stability and aeolian sedimentWe identify new research directions to advance understanding of landscape response to climate change [ABSTRACT FROM AUTHOR]

Landscapes evolve in response to prolonged and/or intense precipitation resulting from atmospheric processes at various spatial and temporal scales. Whereas synoptic (large‐scale) features (e.g., atmospheric rivers and hurricanes) govern regional‐scale hydrologic hazards such as widespread flooding, mesoscale features such as thunderstorms or squall lines are more likely to trigger localized geomorphic hazards such as landslides. Thus, to better understand relations between hydrometeorological drivers and landscape response, a knowledge of mesoscale meteorology and its impacts is needed. Here we investigate the extreme geomorphic response associated with one type of mesoscale meteorological feature, the narrow cold frontal rainband (NCFR). Resulting from low‐level convergence and shallow convection along a cold front, NCFRs are narrow bands of high‐intensity rainfall that occur in midlatitude areas of the world. Our study examines an NCFR impacting the Sierra Nevada foothills (California, USA) that initiated over 500 landslides, mobilized ~360,000 metric tons of sediment to the fluvial system (as much as 16 times the local annual sediment yield), and severely damaged local infrastructure and regional water transport facilities. Coupling geomorphological field investigations with meteorological analyses, we demonstrate that precipitation associated with the NCFR was both intense (maximum 15 min intensity of 70 mm/hr) and localized, resulting in a highly concentrated band of shallow landsliding. This meteorological phenomenon likely plays an important role in landscape evolution and hazard initiation. Other types of mesoscale meteorological features also occur globally and offer new avenues for understanding the effects of storms on landscapes. Plain Language Summary: Major storms can cause extreme and hazardous landscape disturbances, but links between storm conditions and landscape response such as erosion and landslides remain poorly constrained. This is partly due to the lack of attention generally given to the finer‐scale details of storms. We examined one type of atmospheric feature that is common in western North America (as well as in other regions), the narrow cold frontal rainband, and studied its effects on the landscape. In 2018, one such event in the Tuolumne River watershed, California, caused more than 500 landslides in a narrow area, moving more sediment in one day than the river would normally transport in a year. We find that landscape change, including potentially hazardous events such as landslides, can be driven primarily by fine‐scale rainfall patterns rather than by the larger‐scale storm conditions. More integration between weather and landscape scientists can advance knowledge of how storms influence landscapes and produce hazards, especially during extreme events. Key Points: Mesoscale atmospheric processes such as narrow cold frontal rainbands play key roles in triggering landscape responsesOne such event in the Tuolumne River canyon, California, generated >500 landslides and 1.5–16 times the usual annual sediment yieldPredictions of extreme, hazardous landscape response will benefit by incorporating mesoscale atmospheric processes driving intense rainfall [ABSTRACT FROM AUTHOR]

During 2019, the Journal of Geophysical Research‐Earth Surface handled a record‐high number of submitted manuscripts. Managing these in order to deliver the highest‐quality published science relies, of course, on obtaining quality peer review. We all recognize the demand that this places on the reviewers' time, especially as members of the Earth surface scientific community receive ever increasing numbers of requests to review manuscripts for many journals. The editors wish to extend our sincere thanks to all the 674 reviewers who volunteered their time to provide 962 reviews for JGR‐Earth Surface in 2019. We certainly appreciate the time and effort that these reviewers have put into writing insightful, constructive review comments, an essential part of moving the science forward. Key Point: The Editors thank the 2019 peer reviewers [ABSTRACT FROM AUTHOR]

The process of completing and communicating rigorous, high‐impact science depends heavily on obtaining quality peer review prior to publication. As AGU journals strive continually to publish excellent work, we recognize the demand that this places on reviewers' time, especially as most of us seem to receive ever‐increasing numbers of requests to review manuscripts. JGR‐Earth Surface typically strives to obtain three reviews per manuscript, to best ensure the quality of the science that we publish. We thank the members of the earth‐surface community who volunteered their time to complete these reviews for JGR‐Earth Surface in 2018: a total of 874 reviews provided by 650 scientists. We greatly appreciate your time, your thoughtful and constructive review comments, and especially your dedication to this all‐important part of producing high‐quality science. Key Points: The Editors thank the 2018 peer reviewers [ABSTRACT FROM AUTHOR]

Dam removal provides a valuable opportunity to measure the fluvial response to changes in both sediment supply and the processes that shape channel morphology. We present the first study of river response to the removal of a large (32‐m‐high) dam in a Mediterranean hydroclimatic setting, on the Carmel River, coastal California, USA. This before‐after/control‐impact study measured changes in channel topography, grain size, and salmonid spawning habitat throughout dam removal and subsequent major floods. During dam removal, the river course was re‐routed in order to leave most of the impounded sediment sequestered in the former reservoir and thus prevent major channel and floodplain aggradation downstream. However, a substantial sediment pulse occurred in response to base‐level fall, knickpoint migration, and channel avulsion through sediment in the former reservoir above the newly re‐routed channel. The sediment pulse advanced ~3.5 km in the first wet season after dam removal, resulting in decreased riverbed grain size downstream of the dam site. In the second wet season after dam removal, high flows (including a 30‐year flood and two 10‐year floods) transported sediment > 30 km downstream, filling pools and reducing cross‐channel relief. Deposition of gravel in the second wet season after dam removal enhanced salmonid spawning habitat downstream of the dam site. We infer that in dam removals where most reservoir sediment remains impounded and where high flows follow soon after dam removal, flow sequencing becomes a more important driver of geomorphic and fish‐habitat change than the dam removal alone. © 2018 John Wiley & Sons, Ltd. We present the first study of river response to removal of a large dam in a Mediterranean hydroclimatic setting. We demonstrate that when a substantial proportion of sediment is sequestered in place, high flows can become relatively more important as drivers of geomorphic change than is the dam removal alone. This result contrasts many previous dam removals from other bioregions where studies found little connection between post‐dam‐removal flow magnitude and the coupled processes of reservoir‐sediment erosion and downstream deposition. [ABSTRACT FROM AUTHOR]

In river valleys, sediment moves between active river channels, near-channel deposits including bars and floodplains, and upland environments such as terraces and aeolian dunefields. Sediment availability is a prerequisite for the sustained transfer of material between these areas, and for the eco-geomorphic functioning of river networks in general. However, the difficulty of monitoring sediment availability and movement at the reach or corridor scale has hindered our ability to quantify and forecast the response of sediment transfer to hydrologic or land cover alterations. Here we leverage spatiotemporally extensive datasets quantifying sediment areal coverage along a 28 km reach of the Colorado River in Grand Canyon, southwestern USA. In concert with information on hydrologic alteration and vegetation encroachment resulting from the operation of Glen Canyon Dam (constructed in 1963) upstream of our study reach, we model the relative and combined influence of changes in (a) flow and (b) riparian vegetation extent on the areal extent of sediment available for transport in the river valley over the period from 1921 to 2016. In addition, we use projections of future streamflow and vegetation encroachment to forecast sediment availability over the 20 year period from 2016 to 2036. We find that hydrologic alteration has reduced the areal extent of bare sediment by 9% from the pre- to post-dam periods, whereas vegetation encroachment further reduced bare sediment extent by 45%. Over the next 20 years, the extent of bare sediment is forecast to be reduced by an additional 12%. Our results demonstrate the impact of river regulation, specifically the loss of annual low flows and associated vegetation encroachment, on reducing the sediment available for transfer within river valleys. This work provides an extendable framework for using high-resolution data on streamflow and land cover to assess and forecast the impact of watershed perturbation (e.g. river regulation, land cover shifts, climate change) on sediment connectivity at the corridor scale. [ABSTRACT FROM AUTHOR]

Abstract: Small, steep watersheds are prolific sediment sources from which sediment flux is highly sensitive to climatic changes. Storm intensity and frequency are widely expected to increase during the 21st century, and so assessing the response of small, steep watersheds to extreme rainfall is essential to understanding landscape response to climate change. During record winter rainfall in 2016–2017, the San Lorenzo River, coastal California, had nine flow peaks representing 2–10‐year flood magnitudes. By the third flood, fluvial suspended sediment showed a regime shift to greater and coarser sediment supply, coincident with numerous landslides in the watershed. Even with no singular catastrophic flood, these flows exported more than half as much sediment as had a 100‐year flood 35 years earlier, substantially enlarging the nearshore delta. Annual sediment load in 2017 was an order of magnitude greater than during an average‐rainfall year, and 500‐fold greater than in a recent drought. These anomalous sediment inputs are critical to the coastal littoral system, delivering enough sediment, sometimes over only a few days, to maintain beaches for several years. Future projections of megadroughts punctuated by major atmospheric‐river storm activity suggest that interannual sediment‐yield variations will become more extreme than today in the western USA, with potential consequences for coastal management, ecosystems, and water‐storage capacity. The occurrence of two years with major sediment export over the past 35 years that were not associated with extremes of the El Niño Southern Oscillation or Pacific Decadal Oscillation suggests caution in interpreting climatic signals from marine sedimentary deposits derived from small, steep, coastal watersheds, to avoid misinterpreting the frequencies of those cycles. Published 2018. This article is a U.S. Government work and is in the public domain in the USA. [ABSTRACT FROM AUTHOR]

Climate change affects cryosphere-fed rivers and alters seasonal sediment dynamics, affecting cyclical fluvial material supply and year-round water-food-energy provisions to downstream communities. Here, we demonstrate seasonal sediment-transport regime shifts from the 1960s to 2000s in four cryosphere-fed rivers characterized by glacial, nival, pluvial, and mixed regimes, respectively. Spring sees a shift toward pluvial-dominated sediment transport due to less snowmelt and more erosive rainfall. Summer is characterized by intensified glacier meltwater pulses and pluvial events that exceptionally increase sediment fluxes. Our study highlights that the increases in hydroclimatic extremes and cryosphere degradation lead to amplified variability in fluvial fluxes and higher summer sediment peaks, which can threaten downstream river infrastructure safety and ecosystems and worsen glacial/pluvial floods. We further offer a monthly-scale sediment-availability-transport model that can reproduce such regime shifts and thus help facilitate sustainable reservoir operation and river management in wider cryospheric regions under future climate and hydrological change. [ABSTRACT FROM AUTHOR]

Identifying the relative contributions of physical and ecological processes to channel evolution remains a substantial challenge in fluvial geomorphology. We use a 74-year aerial photographic record of the Hoh, Queets, Quinault, and Elwha Rivers, Olympic National Park, Washington, USA, to investigate whether physical or trophic-cascade-driven ecological factors - excessive elk impacts after wolves were extirpated a century ago - are the dominant drivers of channel planform in these gravel-bed rivers. We find that channel width and braiding show strong relationships with recent flood history. All four rivers widened significantly after having been relatively narrow in the 1970s, consistent with increased flood activity since then. Channel planform also reflects sediment-supply changes, evident from landslide response on the Elwha River. We surmise that the Hoh River, which shows a multi-decadal trend toward greater braiding, is adjusting to increased sediment supply associated with rapid glacial retreat. These rivers demonstrate transmission of climatic signals through relatively short sediment-routing systems that lack substantial buffering by sediment storage. Legacy effects of anthropogenic modification likely also affect the Quinault River planform. We infer no correspondence between channel evolution and elk abundance, suggesting that trophic-cascade effects in this setting are subsidiary to physical controls on channel morphology. Our findings differ from previous interpretations of Olympic National Park fluvial dynamics and contrast with the classic example of Yellowstone National Park, where legacy effects of elk overuse are apparent in channel morphology; we attribute these differences to hydrologic regime and large-wood availability. Published 2016. This article is a U.S. Government work and is in the public domain in the USA [ABSTRACT FROM AUTHOR]

The Editors of the Journal of Geophysical Research—Earth Surface present a new strategic plan for the journal. The journal will contribute to the objectives of AGU to embrace advancing Earth and space science for the benefit of human societies and the environment, while continuing to value fundamental science deeply. Many scientific topics covered by JGR Earth Surface are closely connected to urgent, complex problems affecting humanity and the global environment today, including climate change and a variety of natural hazards; this strategic plan is intended to ensure that published science is robust, impactful, and ultimately used to help address those problems. The plan prioritizes (1) publishing high‐impact science using the highest standards of scientific ethics and rigor; (2) advancing mechanistic understanding needed to address societal challenges; and (3) ensuring that a diverse talent pool contributes to the science through a fair, equitable review and publication process. Key Point: A strategic plan for JGR Earth Surface is presented, in alignment with AGU's goals and objectives [ABSTRACT FROM AUTHOR]

A substantial increase in fluvial sediment supply relative to transport capacity causes complex, large-magnitude changes in river and floodplain morphology downstream. Although sedimentary and geomorphic responses to sediment pulses are a fundamental part of landscape evolution, few opportunities exist to quantify those processes over field scales. We investigated the downstream effects of sediment released during the largest dam removal in history, on the Elwha River, Washington, USA, by measuring changes in riverbed elevation and topography, bed sediment grain size, and channel planform as two dams were removed in stages over two years. As 10.5 million t (7.1 million m 3 ) of sediment was released from two former reservoirs, downstream dispersion of a sediment wave caused widespread bed aggradation of ~ 1 m (greater where pools filled), changed the river from pool–riffle to braided morphology, and decreased the slope of the lowermost river. The newly deposited sediment, which was finer than most of the pre-dam-removal bed, formed new bars (largely pebble, granule, and sand material), prompting aggradational channel avulsion that increased the channel braiding index by almost 50%. As a result of mainstem bed aggradation, floodplain channels received flow and accumulated new sediment even during low to moderate flow conditions. The river system showed a two- to tenfold greater geomorphic response to dam removal (in terms of bed elevation change magnitude) than it had to a 40-year flood event four years before dam removal. Two years after dam removal began, as the river had started to incise through deposits of the initial sediment wave, ~ 1.2 million t of new sediment (~ 10% of the amount released from the two reservoirs) was stored along 18 river km of the mainstem channel and 25 km of floodplain channels. The Elwha River thus was able to transport most of the released sediment to the river mouth. The geomorphic alterations and changing bed sediment grain size along the Elwha River have important ecological implications, affecting aquatic habitat structure, benthic fauna, salmonid fish spawning and rearing potential, and riparian vegetation. The response of the river to dam removal represents a unique opportunity to observe and quantify fundamental geomorphic processes associated with a massive sediment influx, and also provides important lessons for future river-restoration endeavors. [ABSTRACT FROM AUTHOR]

Manuscripts submitted to the Journal of Geophysical Research: Earth Surface will require a Plain Language Summary beginning in July 2021. Plain Language Summary: Starting in July 2021, authors of manuscripts submitted to the Journal of Geophysical Research: Earth Surface will be required to write a short description using minimal jargon of the research presented in their paper ("Plain Language Summary"). Key Point: Authors of manuscripts submitted to Journal of Geophysical Research: Earth Surface must include a Plain Language Summary with their submission beginning in July 2021 [ABSTRACT FROM AUTHOR]