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1. Asymmetric hillslope erosion following wildfire in Fourmile Canyon, Colorado: asymetric hillslope erosion wildfire fourmile canyon

   https://doi.org/10.1002/esp.4348  

   Abrahams, Edward R.; Kaste, James M.; Ouimet, William; Dethier, David P. (July 2018, Earth Surface Processes and Landforms)
2. Impact of gully incision on hillslope hydrology

   https://doi.org/10.1002/hyp.13845  

   Chen, Xing; Kumar, Mukesh; deB Richter, Daniel; Mau, Yair (July 2020, Hydrological Processes)

   Abstract The Southern U.S. Piedmont ranging from Virginia to Georgia underwent severe gully erosion over a century of farming mainly for cotton (1800s–1930s). Although tree succession blanketed much of this region by the middle 20th century, gully erosion still occurs, especially during wet seasons. While many studies on gully erosion have focused on soil loss, soil carbon exchange, and stormwater response, the impacts on soil moisture, groundwater, and transpiration remain under‐studied. Using a newly developed 2D hydrologic model, this study analyzes the impacts of gully erosion on hillslope hydrologic states and fluxes. Results indicate that increases in gully incision lead to reduction in groundwater table, root zone soil moisture, and transpiration. These reductions show seasonal variations, but the season when the reduction is maximum differs among the hydrologic variables. Spatially, the impacts are generally the greatest near the toe of the hillslope and reduce further away from it, although the reductions are sometimes non‐monotonic. Overall, the impacts are larger for shallow gully depths and diminish as the incision goes deeper. Lastly, the extent of impacts on a heterogeneous hillslope is found to be very different with respect to a homogeneous surrogate made of dominant soil properties. These results show that through gully erosion, the landscape not only loses soil but also a large amount of water from the subsurface. The magnitude of water loss is, however, dependent on hydrogeologic and topographic configuration of the hillslope. The results will facilitate (a) mapping of relative susceptibility of landscapes to gullying, (b) understanding of the impacts of stream manipulations such as due to dredging on hillslope eco‐hydrology, (c) prioritization of mitigation measures to prevent gullying, and (d) design of observation campaigns to assess the impacts of gullying on hydrologic response. 

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3. Hillslope roughness reveals forest sensitivity to extreme winds

   https://doi.org/10.1073/pnas.2212105120  

   Doane, Tyler H.; Yanites, Brian J.; Edmonds, Douglas A.; Novick, Kimberly A. (January 2023, Proceedings of the National Academy of Sciences)

   Windthrow, or the uprooting of trees by extreme wind gusts, is a natural forest disturbance that creates microhabitats, turns over soil, alters hydrology, and removes carbon from the above-ground carbon stock. Long recurrence intervals between extreme wind events, however, make direct observations of windthrow rare, challenging our understanding of this important disturbance process. To overcome this difficulty, we present an approach that uses the geomorphic record of hillslope topographic roughness as a proxy for the occurrence of windthrow. The approach produces a probability function of the number of annual windthrow events for a maximum wind speed, allowing us to explore how windthrow or tree strengths may change due to shifting wind climates. Slight changes to extreme wind speeds may drive comparatively large changes in windthrow production rates or force trees to respond and change the distribution. We also highlight that topographic roughness has the potential to serve as an important archive of extreme wind speeds. 

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4. Influence of Climate‐Forcing Frequency on Hillslope Response

   https://doi.org/10.1029/2021GL094305  

   Godard, V.; Tucker, G. E. (September 2021, Geophysical Research Letters)

   Abstract Assessing rivers' and hillslopes' sensitivity to external forcing is paramount to understand landscape evolution, in particular as a response to Quaternary climate changes. River networks are usually considered to be the main conveyors of environmental signals, such as changes in precipitation, temperature, or baselevel. Yet because hillslopes provide the source of sediment for river networks, their response to environmental change also modulates landscape dynamics. In order to characterize such behavior, we analyze the response times of a transport‐limited hillslope. We use simple numerical models of denudation to study hillslope responses to oscillatory forcing and understand their filtering effects on environmental signals. Modifications in the frequency of climate oscillation, such as the change that occurred at the Mid‐Pleistocene Transition, can significantly modulate hillslope sediment‐flux response. We infer a wide range of hillslope responses, ranging from negligible change over the full range of climate‐forcing frequencies, to a significant filtering of long‐period signals. 

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5. The influence of diurnal snowmelt and transpiration on hillslope throughflow and stream response

   https://doi.org/10.5194/hess-22-4295-2018  

   Woelber, Brett; Maneta, Marco P.; Harper, Joel; Jencso, Kelsey G.; Gardner, W. Payton; Wilcox, Andrew C.; López-Moreno, Ignacio (January 2018, Hydrology and Earth System Sciences)

   Abstract. During spring, daily stream flow and groundwater dynamics in forested subalpine catchmentsare to a large extent controlled by hydrological processes thatrespond to the day–night energy cycle. Diurnal snowmelt and transpirationevents combine to induce pressure variations in the soil water storage thatare propagated to the stream. In headwater catchments these pressurevariations can account for a significant amount of the total pressure in thesystem and control the magnitude, duration, and timing of stream inflowpulses at daily scales, especially in low-flow systems. Changes in theradiative balance at the top of the snowpack can alter the diurnal hydrologicdynamics of the hillslope–stream system, with potential ecological andmanagement consequences. We present a detailed hourly dataset of atmospheric, hillslope, andstreamflow measurements collected during one melt season from a semi-alpineheadwater catchment in western Montana, US. We use this dataset toinvestigate the timing, pattern, and linkages among snowmelt-dominatedhydrologic processes and assess the role of the snowpack, transpiration, andhillslopes in mediating daily movements of water from the top of the snowpackto local stream systems. We found that the amount of snowpack cold contentaccumulated during the night, which must be overcome every morning beforesnowmelt resumes, delayed water recharge inputs by up to 3h early in themelt season. These delays were further exacerbated by multi-day storms (coldfronts), which resulted in significant depletions in the soil and streamstorages. We also found that both diurnal snowmelt and transpiration signalsare present in the diurnal soil and stream storage fluctuations, although theindividual contributions of these processes are difficult to discern. Ouranalysis showed that the hydrologic response of the snow–hillslope–streamsystem is highly sensitive to atmospheric drivers at hourly scales and thatvariations in atmospheric energy inputs or other stresses are quicklytransmitted and alter the intensity, duration, and timing of snowmelt pulsesand soil water extractions by vegetation, which ultimately drive variationsin soil and stream water pressures. 

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