Journal articles on the topic 'Hillslope zones'
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1
Kim, C. P., G. D. Salvucci, and D. Entekhabi. "Groundwater-surface water interaction and the climatic spatial patterns of hillslope hydrological response." Hydrology and Earth System Sciences 3, no. 3 (September 30, 1999): 375–84. http://dx.doi.org/10.5194/hess-3-375-1999.
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Abstract. A transient, mixed analytical-numerical model of hillslope hydrological behaviour is used to study the patterns of infiltration, evapotranspiration, recharge and lateral flow across hillslopes. Computational efficiency is achieved by treating infiltration and phreatic surface movement analytically. The influence of dynamic coupling of the saturated and unsaturated zones on the division of hillslopes into units of distinct hydrological behaviour is analyzed. The results indicate the importance of downhill groundwater flow on the lateral distribution of soil moisture and hydrological fluxes; unsaturated lateral flow is shown to be of relatively minor importance. For most conditions, the hillslope organizes itself into three distinct regions; an uphill recharge and a downhill discharge zone separated by a midline zone over which there is, on average, no recharge or discharge. A temporal perturbation analysis of the phreatic surface, made to quantify the deviations between the equivalent-steady water table derived by Salvucci and Entekhabi (1995) and the long-term mean water table, shows that the equivalent-steady water table effectively couples the unsaturated and saturated zone dynamics across storm and interstorm periods and divides the hillslope into distinct hydrological regions. The second order closure terms in the perturbation analysis, expressed as the gradient of water table variance, quantify the deviations and tend to make the hydrological zones relatively less distinct.
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Herron, N. F., and P. B. Hairsine. "A scheme for evaluating the effectiveness of riparian zones in reducing overland flow to streams." Soil Research 36, no. 4 (1998): 683. http://dx.doi.org/10.1071/s96098.
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Two time-independent equations are developed to assess the effectiveness of riparian zones in reducing overland flow to streams for events in which the time-scale of subsurface water redistribution exceeds that of the rainfall event. In one equation, the effectiveness of the riparian area is limited by the storage capacity of its soils, while in the other equation, the infiltration rate determines the buffer’s effectiveness. Riparian zone widths, expressed as a proportion of total hillslope length, are calculated for a number of different climate, antecedent moisture, and management scenarios for hillslopes of varying topographic convergence. A riparian zone width not exceeding 20% of total hillslope length is proposed as a practical management option in this paper. Riparian zone widths that fall within these bounds are predicted for areas where both the hillslopes and riparian areas are in good condition. Where conditions in either area are degraded, disproportionately large riparian buffer widths are predicted. The results suggest that land management initiatives need to be directed at the catchment as a whole if riparian buffers of realistic widths are to be effective.
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Martínez-Carreras, N., C. E. Wetzel, J. Frentress, L. Ector, J. J. McDonnell, L. Hoffmann, and L. Pfister. "Hydrological connectivity inferred from diatom transport through the riparian-stream system." Hydrology and Earth System Sciences 19, no. 7 (July 16, 2015): 3133–51. http://dx.doi.org/10.5194/hess-19-3133-2015.
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Abstract. Diatoms (Bacillariophyta) are one of the most common and diverse algal groups (ca. 200 000 species, ≈ 10–200 μm, unicellular, eukaryotic). Here we investigate the potential of aerial diatoms (i.e. diatoms nearly exclusively occurring outside water bodies, in wet, moist or temporarily dry places) to infer surface hydrological connectivity between hillslope-riparian-stream (HRS) landscape units during storm runoff events. We present data from the Weierbach catchment (0.45 km2, northwestern Luxembourg) that quantify the relative abundance of aerial diatom species on hillslopes and in riparian zones (i.e. surface soils, litter, bryophytes and vegetation) and within streams (i.e. stream water, epilithon and epipelon). We tested the hypothesis that different diatom species assemblages inhabit specific moisture domains of the catchment (i.e. HRS units) and, consequently, the presence of certain species assemblages in the stream during runoff events offers the potential for recording whether there was hydrological connectivity between these domains or not. We found that a higher percentage of aerial diatom species was present in samples collected from the riparian and hillslope zones than inside the stream. However, diatoms were absent on hillslopes covered by dry litter and the quantities of diatoms (in absolute numbers) were small in the rest of hillslope samples. This limits their use for inferring hillslope-riparian zone connectivity. Our results also showed that aerial diatom abundance in the stream increased systematically during all sampled events (n = 11, 2011–2012) in response to incident precipitation and increasing discharge. This transport of aerial diatoms during events suggested a rapid connectivity between the soil surface and the stream. Diatom transport data were compared to two-component hydrograph separation, and end-member mixing analysis (EMMA) using stream water chemistry and stable isotope data. Hillslope overland flow was insignificant during most sampled events. This research suggests that diatoms were likely sourced exclusively from the riparian zone, since it was not only the largest aerial diatom reservoir, but also since soil water from the riparian zone was a major streamflow source during rainfall events under both wet and dry antecedent conditions. In comparison to other tracer methods, diatoms require taxonomy knowledge and a rather large processing time. However, they can provide unequivocal evidence of hydrological connectivity and potentially be used at larger catchment scales.
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Wainwright, Haruko M., Sebastian Uhlemann, Maya Franklin, Nicola Falco, Nicholas J. Bouskill, Michelle E. Newcomer, Baptiste Dafflon, et al. "Watershed zonation through hillslope clustering for tractably quantifying above- and below-ground watershed heterogeneity and functions." Hydrology and Earth System Sciences 26, no. 2 (January 31, 2022): 429–44. http://dx.doi.org/10.5194/hess-26-429-2022.
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Abstract. In this study, we develop a watershed zonation approach for characterizing watershed organization and functions in a tractable manner by integrating multiple spatial data layers. We hypothesize that (1) a hillslope is an appropriate unit for capturing the watershed-scale heterogeneity of key bedrock-through-canopy properties and for quantifying the co-variability of these properties representing coupled ecohydrological and biogeochemical interactions, (2) remote sensing data layers and clustering methods can be used to identify watershed hillslope zones having the unique distributions of these properties relative to neighboring parcels, and (3) property suites associated with the identified zones can be used to understand zone-based functions, such as response to early snowmelt or drought and solute exports to the river. We demonstrate this concept using unsupervised clustering methods that synthesize airborne remote sensing data (lidar, hyperspectral, and electromagnetic surveys) along with satellite and streamflow data collected in the East River Watershed, Crested Butte, Colorado, USA. Results show that (1) we can define the scale of hillslopes at which the hillslope-averaged metrics can capture the majority of the overall variability in key properties (such as elevation, net potential annual radiation, and peak snow-water equivalent – SWE), (2) elevation and aspect are independent controls on plant and snow signatures, (3) near-surface bedrock electrical resistivity (top 20 m) and geological structures are significantly correlated with surface topography and plan species distribution, and (4) K-means, hierarchical clustering, and Gaussian mixture clustering methods generate similar zonation patterns across the watershed. Using independently collected data, we show that the identified zones provide information about zone-based watershed functions, including foresummer drought sensitivity and river nitrogen exports. The approach is expected to be applicable to other sites and generally useful for guiding the selection of hillslope-experiment locations and informing model parameterization.
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Martínez-Carreras, N., C. E. Wetzel, J. Frentress, L. Ector, J. J. McDonnell, L. Hoffmann, and L. Pfister. "Hydrological connectivity as indicated by transport of diatoms through the riparian–stream system." Hydrology and Earth System Sciences Discussions 12, no. 2 (February 24, 2015): 2391–434. http://dx.doi.org/10.5194/hessd-12-2391-2015.
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Abstract. Diatoms (Bacillariophyta) are one of the most common and diverse algal groups (ca. 200 000 species, ≈10–200 μm, unicellular, eukaryotic). Here we investigate the potential of terrestrial and aerophytic diatoms (i.e. diatoms nearly exclusively occurring outside water bodies, on wet, moist or temporarily dry places) to infer surface hydrological connectivity between hillslope–riparian–stream (HRS) landscape units during storm runoff events. We present data from the Weierbach catchment (0.45 km2, NW Luxembourg) that quantifies the relative abundance of terrestrial and aerophytic diatom species on hillslopes and in riparian zones (i.e. surface soils, litter, bryophytes and vegetation) and within streams (i.e. stream water, epilithon and epipelon). We tested the hypothesis that different diatom species assemblages inhabit specific moisture domains of the catchment (i.e. HRS units) and, consequently, the presence of certain species assemblages in the stream during runoff events offers the potential for recording if there was or not hydrological connectivity between these domains. We found that a higher percentage of terrestrial and aerophytic diatom species was present in samples collected from the riparian and hillslope zones than inside the stream. However, diatoms were absent on hillslopes covered by dry litter, limiting their use to infer hillslope–riparian zone connectivity in some parts of the catchment. Our results also showed that terrestrial and aerophytic diatom abundance in the stream increased systematically during all sampled events (n = 11, 2010–2011) in response to incident precipitation and increasing discharge. This transport of terrestrial and aerophytic diatoms during events suggested a rapid connectivity between the soil surface and the stream. Diatom transport data was compared to two-component hydrograph separation, and end-member mixing analysis (EMMA) using stream water chemistry and stable isotope data. This research suggests that diatoms were likely sourced exclusively from the riparian zone, since it was not only the largest terrestrial and aerophytic diatom reservoir, but also riparian zone water was a major streamflow source during rainfall events under both wet and dry antecedent condition.
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Burt, T. P., and G. Pinay. "Linking hydrology and biogeochemistry in complex landscapes." Progress in Physical Geography: Earth and Environment 29, no. 3 (September 2005): 297–316. http://dx.doi.org/10.1191/0309133305pp450ra.
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This review seeks to examine connections between hydrology and biogeochemistry at the landscape scale. A review of research on landscape structure and organization provides a context for what follows, and seeks to integrate work at relevant scales in ecology and geomorphology; the degree of functional ‘connectedness’ between different landscape elements provides the key theme. Following a review of hillslope hydrology, links between hillslope runoff pathways and nutrient dynamics are then considered. We focus in particular on riparian zones, where nutrient dynamics has relevance for water-quality management in catchments. In conclusion, we argue that future studies need to focus on the critical near-stream zone, given its importance in coupling hillslope and channel systems.
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Bernal, S., and F. Sabater. "Changes in discharge and solute dynamics between hillslope and valley-bottom intermittent streams." Hydrology and Earth System Sciences 16, no. 6 (June 4, 2012): 1595–605. http://dx.doi.org/10.5194/hess-16-1595-2012.
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Abstract. To gain understanding on how alluvial zones modify water and nutrient export from semiarid catchments, we compared monthly discharge as well as stream chloride, carbon, and nitrogen dynamics between a hillslope catchment and a valley-bottom catchment with a well-developed alluvium. Stream water and solute fluxes from the hillslope and valley-bottom catchments showed contrasting patterns between hydrological transitions and wet periods, especially for bio-reactive solutes. During transition periods, stream water export decreased >40% between the hillslope and the valley bottom coinciding with the prevalence of stream-to-aquifer fluxes at the alluvial zone. In contrast, stream water export increased by 20–70% between the hillslope and valley-bottom catchments during wet periods. During transition periods, stream solute export decreased by 34–97% between the hillslope and valley-bottom catchments for chloride, nitrate, and dissolved organic carbon. In annual terms, stream nitrate export from the valley-bottom catchment (0.32 ± 0.12 kg N ha−1 yr−1 [average ± standard deviation]) was 30–50% lower than from the hillslope catchment (0.56 ± 0.32 kg N ha−1 yr−1). The annual export of dissolved organic carbon was similar between the two catchments (1.8 ± 1 kg C ha−1 yr−1). Our results suggest that hydrological retention in the alluvial zone contributed to reduce stream water and solute export from the valley-bottom catchment during hydrological transition periods when hydrological connectivity between the hillslope and the valley bottom was low.
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Voytek, Emily B., Caitlin R. Rushlow, Sarah E. Godsey, and Kamini Singha. "Identifying hydrologic flowpaths on arctic hillslopes using electrical resistivity and self potential." GEOPHYSICS 81, no. 1 (January 1, 2016): WA225—WA232. http://dx.doi.org/10.1190/geo2015-0172.1.
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Shallow subsurface flow is a dominant process controlling hillslope runoff generation, soil development, and solute reaction and transport. Despite their importance, the location and geometry of these flow paths are difficult to determine. In arctic environments, shallow subsurface flow paths are limited to a thin zone of seasonal thaw above permafrost, which is traditionally assumed to mimic the surface topography. We have used a combined approach of electrical resistivity tomography (ERT) and self-potential (SP) measurements to map shallow subsurface flow paths in and around water tracks, drainage features common to arctic hillslopes. ERT measurements delineate thawed zones in the subsurface that control flow paths, whereas SP is sensitive to groundwater flow. We have found that areas of low electrical resistivity in the water tracks were deeper than manual thaw depth estimates and varied from the surface topography. This finding suggests that traditional techniques might underestimate active-layer thaw and the extent of the flow path network on arctic hillslopes. SP measurements identify complex 3D flow paths in the thawed zone. Our results lay the groundwork for investigations into the seasonal dynamics, hydrologic connectivity, and climate sensitivity of spatially distributed flow path networks on arctic hillslopes.
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Williams, C. Jason, Frederick B. Pierson, Peter R. Robichaud, Osama Z. Al-Hamdan, Jan Boll, and Eva K. Strand. "Structural and functional connectivity as a driver of hillslope erosion following disturbance." International Journal of Wildland Fire 25, no. 3 (2016): 306. http://dx.doi.org/10.1071/wf14114.
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Hydrologic response to rainfall on fragmented or burnt hillslopes is strongly influenced by the ensuing connectivity of runoff and erosion processes. Yet cross-scale process connectivity is seldom evaluated in field studies owing to scale limitations in experimental design. This study quantified surface susceptibility and hydrologic response across point to hillslope scales at two degraded unburnt and burnt woodland sites using rainfall simulation and hydrologic modelling. High runoff (31–47 mm) and erosion (154–1893 g m–2) measured at the patch scale (13 m2) were associated with accumulation of fine-scale (0.5-m2) splash-sheet runoff and sediment and concentrated flow formation through contiguous bare zones (64–85% bare ground). Burning increased the continuity of runoff and sediment availability and yield. Cumulative runoff was consistent across plot scales whereas erosion increased with increasing plot area due to enhanced sediment detachment and transport. Modelled hillslope-scale runoff and erosion reflected measured patch-scale trends and the connectivity of processes and sediment availability. The cross-scale experiments and model predictions indicate the magnitude of hillslope response is governed by rainfall input and connectivity of surface susceptibility, sediment availability, and runoff and erosion processes. The results demonstrate the importance in considering cross-scale structural and functional connectivity when forecasting hydrologic and erosion responses to disturbances.
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Votrubova, Jana, Michal Dohnal, Tomas Vogel, Martin Sanda, and Miroslav Tesar. "Episodic runoff generation at Central European headwater catchments studied using water isotope concentration signals." Journal of Hydrology and Hydromechanics 65, no. 2 (June 1, 2017): 114–22. http://dx.doi.org/10.1515/johh-2017-0002.
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AbstractHydrological monitoring in small headwater catchments provides the basis for examining complex interrelating hydraulic processes that govern the runoff generation. Contributions of different subsurface runoff mechanisms to the catchment discharge formation at two small forested headwater catchments are studied with the help of their natural isotopic signatures. The Uhlirska catchment (Jizera Mts., Czech Republic) is situated in headwater area of the Lusatian Neisse River. The catchment includes wetlands at the valley bottom developed over deluviofluvial granitic sediments surrounded by gentle hillslopes with shallow soils underlain by weathered granite. The Liz catchment (Bohemian Forest, Czech Republic) is situated in headwater area of the Otava River. It belongs to hillslope-type catchments with narrow riparian zones. The soil at Liz is developed on biotite paragneiss bedrock. The basic comparison of hydrological time series reveals that the event-related stream discharge variations at the Uhlirska catchment are bigger and significantly more frequent than at Liz. The analysis of isotope concentration data revealed different behavior of the two catchments during the major rainfall-runoff events. At Uhlirska, the percentage of the direct runoff formed by the event water reaches its maximum on the falling limb of the hydrograph. At Liz, the event water related fraction of the direct outflow is maximal on the rising limb of the hydrograph and then lowers. The hydraulic functioning of the Uhlirska catchment is determined by communication between hillslope and riparian zone compartments.
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Li, Guangxuan, Xi Chen, Zhicai Zhang, Lichun Wang, and Chris Soulsby. "Effects of passive-storage conceptualization on modeling hydrological function and isotope dynamics in the flow system of a cockpit karst landscape." Hydrology and Earth System Sciences 26, no. 21 (November 7, 2022): 5515–34. http://dx.doi.org/10.5194/hess-26-5515-2022.
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Abstract. Conceptualizing passive storage in coupled flow–isotope models can improve the simulation of mixing and attenuation effects on tracer transport in many natural systems, such as catchments or rivers. However, the effectiveness of incorporating different conceptualizations of passive storage in models of complex karst flow systems remains poorly understood. In this study, we developed a coupled flow–isotope model that conceptualizes both “fast-flow” and “slow-flow” processes in heterogeneous aquifers as well as hydrological connections between steep hillslopes and low-lying depression units in cockpit karst landscapes. The model tested contrasting configurations of passive storage in the fast- and slow-flow systems and was optimized using a multi-objective optimization algorithm based on detailed observational data of discharge and isotope dynamics in the Chenqi Catchment in southwestern China. Results show that one to three passive-storage zones distributed in hillslope fast-/slow-flow reservoirs and/or depression slow-flow reservoirs provided optimal model structures in the study catchment. This optimization can effectively improve the simulation accuracy for outlet discharge and isotope signatures. Additionally, the optimal tracer-aided model reflects dominant flow paths and connections of the hillslope and depression units, yielding reasonable source area apportionment for dominant hydrological components (e.g., more than ∼ 80 % of fast flow in the total discharge) and solute transport in the steep hillslope unit of karst flow systems. Our coupled flow–isotope model for karst systems provides a novel, flexible tool for more realistic catchment conceptualizations that can easily be transferred to other cockpit karst catchments.
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Feranie, S., T. M. Khoiriyah, F. D. E. Jabbar, and A. Tohari. "The Effect of Rainfall Intensity to Landslide Run-Out Prediction and Velocity: A Parametric Study on Landslide Zones in West Java-Indonesia." Journal of Southwest Jiaotong University 56, no. 3 (June 30, 2021): 540–48. http://dx.doi.org/10.35741/issn.0258-2724.56.3.45.
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Assessment and management of landslide risk require the knowledge of landslide run-out distance and velocity. However, the landslide volume as the basis for calculating landslide run-out distance and velocity is governed by slip surface development during rainfall. Thus, it is necessary to understand how rainfall characteristics influence landslide run-out and velocity. This paper presents a parametric study to clarify the effect of rainfall intensity on landslide run-out and velocity of two steep volcanic cut-hillslopes in West Java, Indonesia. The landslide volumes were estimated from the potential sliding surface obtained from slope stability analysis under a rainfall infiltration. The landslide run-out and velocity were then calculated using an energy conservation formula in a lumped mass model. This study shows that the slip surface developed at a different depth in each slope, depending on the rainfall intensity. As a result, the landslide run-out and velocity of both cut-hillslope are significantly different and, in general, decrease to reach a constant value with increasing rainfall intensity. Thus, the results of this study can be used as a guideline to assess the rainfall-induced landslide movement, especially in cut-hillslopes.
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Pabst, Robert J., and Thomas A. Spies. "Distribution of herbs and shrubs in relation to landform and canopy cover in riparian forests of coastal Oregon." Canadian Journal of Botany 76, no. 2 (February 1, 1998): 298–315. http://dx.doi.org/10.1139/b97-174.
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In this study we characterized the distribution of herb and shrub species relative to landform and forest canopy attributes of streamside forests in the moist, conifer-dominated mountains of coastal Oregon. Species cover and environmental data were collected along transects at 94 sites. Species with relatively similar distributions were classified into 10 species groups to identify major patterns in the vegetation. Although these patterns were highly variable, ordination and gradient analyses indicated that vegetation composition is ordered along a complex environmental gradient running from streamside to hillslope. Similarly, species diversity followed a decreasing trend from active fluvial surfaces to lower hillslopes. Vegetation patterns were related to specific landforms, topographic positions, microsites, and coniferous tree cover within the trans-riparian gradient. We hypothesize that the environmental features correlated with these patterns are surrogates for the underlying mechanisms responsible for them. These are (i) hillslope processes and associated moisture gradients; (ii) hydrological disturbance; (iii) tolerance of saturated, valley-floor soils; (iv) shade tolerance; and (v) mineral soil disturbance. This study indicates that valley-floor and lower-slope plant communities are distinct elements in these forest landscapes, supporting the assumption that riparian zones require a different management and conservation strategy than upland forest communities.Key words: riparian vegetation, ordination, gradient analysis, species groups, landform. Nomenclature is based on that of Hitchcock and Cronquist (1973).
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Jackson, C. Rhett, Menberu Bitew, and Enhao Du. "When interflow also percolates: downslope travel distances and hillslope process zones." Hydrological Processes 28, no. 7 (February 17, 2014): 3195–200. http://dx.doi.org/10.1002/hyp.10158.
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Barbieri, Diogo Mazza, José Marques Júnior, Luis Reynaldo Ferracciú Alleoni, Fernando José Garbuio, and Livia Arantes Camargo. "Hillslope curvature, clay mineralogy, and phosphorus adsorption in an Alfisol cultivated with sugarcane." Scientia Agricola 66, no. 6 (December 2009): 819–26. http://dx.doi.org/10.1590/s0103-90162009000600015.
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Hillslope curvatures are associated with specific environments that correlate to chemical and mineralogical attributes of soil, so determining specific management zones. Phosphorus is one of the main limiting factors to the development and longevity of sugarcane. The type and the mineralogical constitution of the clay fraction play an important role in the phosphorus (P) adsorption of soil. High proportion of gibbsite (Gb) in soil may be the major responsible for P adsorption. The relationships among spatial variability as a function of hillslope curvature, the proportion of kaolinite (Kt) and Gb, and phosphorus adsorption were evaluated in an Alfisol cultivated with sugarcane. Two plots of 1 ha of a concave and a convex hillslope area were selected and 121 samples were collected in each area. The maximum P adsorption was determined in six samples taken randomly in each area. Data were submitted to descriptive statistical and geostatistical analysis. The lowest average values of available phosphorus were found in the convex area. In this area, the proportion of gibbsite, expressed by the values of the ratio [Gb/(Gb + Ct)] and the values of maximum adsorption capacity of phosphorus were higher than in the concave area.
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Schaller, Mirjam, and Todd A. Ehlers. "Comparison of soil production, chemical weathering, and physical erosion rates along a climate and ecological gradient (Chile) to global observations." Earth Surface Dynamics 10, no. 1 (February 15, 2022): 131–50. http://dx.doi.org/10.5194/esurf-10-131-2022.
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Abstract. Weathering of bedrock to produce regolith is essential for sustaining life on Earth and global biogeochemical cycles. The rate of this process is influenced not only by tectonics, but also by climate and biota. We present new data on soil production, chemical weathering, and physical erosion rates from the large climate and ecological gradient of the Chilean Coastal Cordillera (26 to 38∘ S). Four Chilean study areas are investigated and span (from north to south) arid (Pan de Azúcar), semi-arid (Santa Gracia), Mediterranean (La Campana), and temperate humid (Nahuelbuta) climate zones. Observed soil production rates in granitoid soil-mantled hillslopes range from ∼7 to 290 t km−2 yr−1 and are lowest in the sparsely vegetated and arid north and highest in the Mediterranean setting. Calculated chemical weathering rates range from zero in the arid north to a high of 211 t km−2 yr−1 in the Mediterranean zone. Chemical weathering rates are moderate in the semi-arid and temperate humid zones (∼20 to 50 t km−2 yr−1). Similarly, physical erosion rates are lowest in the arid zone (∼11 t km−2 yr−1) and highest in the Mediterranean climate zone (∼91 t km−2 yr−1). The contribution of chemical weathering to total denudation rates is lower in the arid north than further south. However, due to heterogeneities in lithologies and Zr concentrations, reported chemical weathering rates and chemical depletion fractions are affected by large uncertainties. Comparison of Chilean results to published global data collected from hillslope settings underlain by granitoid lithologies documents similar patterns in soil production, chemical weathering, and total denudation rates for varying mean annual precipitation and vegetation cover amounts. We discuss the Chilean and global data in the light of contending model frameworks in the literature and find that observed variations in soil production rates bear the closest resemblance to models explicitly accounting for variations in soil thickness and biomass.
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Fovet, O., L. Ruiz, M. Hrachowitz, M. Faucheux, and C. Gascuel-Odoux. "Hydrological hysteresis and its value for assessing process consistency in catchment conceptual models." Hydrology and Earth System Sciences 19, no. 1 (January 7, 2015): 105–23. http://dx.doi.org/10.5194/hess-19-105-2015.
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Abstract. While most hydrological models reproduce the general flow dynamics, they frequently fail to adequately mimic system-internal processes. In particular, the relationship between storage and discharge, which often follows annual hysteretic patterns in shallow hard-rock aquifers, is rarely considered in modelling studies. One main reason is that catchment storage is difficult to measure, and another one is that objective functions are usually based on individual variables time series (e.g. the discharge). This reduces the ability of classical procedures to assess the relevance of the conceptual hypotheses associated with models. We analysed the annual hysteric patterns observed between stream flow and water storage both in the saturated and unsaturated zones of the hillslope and the riparian zone of a headwater catchment in French Brittany (Environmental Research Observatory ERO AgrHys (ORE AgrHys)). The saturated-zone storage was estimated using distributed shallow groundwater levels and the unsaturated-zone storage using several moisture profiles. All hysteretic loops were characterized by a hysteresis index. Four conceptual models, previously calibrated and evaluated for the same catchment, were assessed with respect to their ability to reproduce the hysteretic patterns. The observed relationship between stream flow and saturated, and unsaturated storages led us to identify four hydrological periods and emphasized a clearly distinct behaviour between riparian and hillslope groundwaters. Although all the tested models were able to produce an annual hysteresis loop between discharge and both saturated and unsaturated storage, the integration of a riparian component led to overall improved hysteretic signatures, even if some misrepresentation remained. Such a system-like approach is likely to improve model selection.
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Fovet, O., L. Ruiz, M. Hrachowitz, M. Faucheux, and C. Gascuel-Odoux. "Hydrological hysteresis in catchments and its value for assessing process consistency in conceptual models." Hydrology and Earth System Sciences Discussions 11, no. 5 (May 28, 2014): 5663–707. http://dx.doi.org/10.5194/hessd-11-5663-2014.
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Abstract. While most hydrological models reproduce the general flow dynamics, they frequently fail to adequately mimic system internal processes. In particular, the relationship between storage and discharge, which often follows annual hysteretic patterns in shallow hard-rock aquifers, is rarely considered in modelling studies. One main reason is that catchment storage is difficult to measure and another one is that objective functions are usually based on individual variables time series (e.g. the discharge). This reduces the ability of classical procedures to assess the relevance of the conceptual hypotheses associated with models. We analyzed the annual hysteric patterns observed between stream flow and water storage both in the saturated and unsaturated zones of the hillslope and the riparian zone of a headwater catchment in French Brittany (ORE AgrHys). The saturated zone storage was estimated using distributed shallow groundwater levels and the unsaturated zone storage using several moisture profiles. All hysteretic loops were characterized by a hysteresis index. Four conceptual models, previously calibrated and evaluated for the same catchment, were assessed with respect to their ability to reproduce the hysteretic patterns. The observed relationship between stream flow, saturated, and unsaturated storages led to identify four hydrological periods and emphasized a clearly distinct behaviour between riparian and hillslope groundwaters. Although all the tested models were able to produce an annual hysteresis loop between discharge and both saturated and unsaturated storage, integration of a riparian component led to overall improved hysteretic signatures, even if some misrepresentation remained. Such systems-like approach is likely to improve model selection.
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Slaymaker, Olav. "A global perspective on denudation data, primarily specific sediment yield in mountainous regions." Landform Analysis 36 (December 30, 2018): 19–31. http://dx.doi.org/10.12657/landfana.036.003.
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A brief review of the evolution of denudation research since the 1960s is followed by a review of specific sediment yield variability in mountainous regions of the world as a function of spatial scale, relief, glaciation, lithology and disturbance type and location within the basin. A general model of scalar relations of suspended sediment yield for Canadian regions warns against comparing data from basins with areas ranging over several orders of magnitude. A regional summary of specific sediment yield in mountainous British Columbia confirms that in basins <1 km2 and >30,000 km2 specific sediment yield decreases with basin size whereas in basins of intermediate size (between 1 km² and 30,000 km²) specific sediment yield increases with basin size. This effect is interpreted in terms of three distinct process zones in every mountain basin. These zones can be characterized as a) generally degrading hillslope zones, b) generally aggrading footslopes and valley sides, and c) channelized flows on valley floors demonstrating either net aggradation or degradation. These are identifiable repeating elements in such landscapes. Suspended sediment yield data from mountainous regions around the world are considered in light of the British Columbia model. Some support for the model is found where basins are stratified according to scale, relief, lithology, disturbance types, and location within each basin. Disturbance types include the presence of glaciers, land use activities of various kinds, such as increasing population pressure in the intertropical montane zone, changing population distribution and associated economic activities in the temperate montane zone, and potentially hydroclimate change.
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Devadoss, Jashvina, Nicola Falco, Baptiste Dafflon, Yuxin Wu, Maya Franklin, Anna Hermes, Eve-Lyn S. Hinckley, and Haruko Wainwright. "Remote Sensing-Informed Zonation for Understanding Snow, Plant and Soil Moisture Dynamics within a Mountain Ecosystem." Remote Sensing 12, no. 17 (August 24, 2020): 2733. http://dx.doi.org/10.3390/rs12172733.
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In the headwater catchments of the Rocky Mountains, plant productivity and its dynamics are largely dependent upon water availability, which is influenced by changing snowmelt dynamics associated with climate change. Understanding and quantifying the interactions between snow, plants and soil moisture is challenging, since these interactions are highly heterogeneous in mountainous terrain, particularly as they are influenced by microtopography within a hillslope. Recent advances in satellite remote sensing have created an opportunity for monitoring snow and plant dynamics at high spatiotemporal resolutions that can capture microtopographic effects. In this study, we investigate the relationships among topography, snowmelt, soil moisture and plant dynamics in the East River watershed, Crested Butte, Colorado, based on a time series of 3-meter resolution PlanetScope normalized difference vegetation index (NDVI) images. To make use of a large volume of high-resolution time-lapse images (17 images total), we use unsupervised machine learning methods to reduce the dimensionality of the time lapse images by identifying spatial zones that have characteristic NDVI time series. We hypothesize that each zone represents a set of similar snowmelt and plant dynamics that differ from other identified zones and that these zones are associated with key topographic features, plant species and soil moisture. We compare different distance measures (Ward and complete linkage) to understand the effects of their influence on the zonation map. Results show that the identified zones are associated with particular microtopographic features; highly productive zones are associated with low slopes and high topographic wetness index, in contrast with zones of low productivity, which are associated with high slopes and low topographic wetness index. The zones also correspond to particular plant species distributions; higher forb coverage is associated with zones characterized by higher peak productivity combined with rapid senescence in low moisture conditions, while higher sagebrush coverage is associated with low productivity and similar senescence patterns between high and low moisture conditions. In addition, soil moisture probe and sensor data confirm that each zone has a unique soil moisture distribution. This cluster-based analysis can tractably analyze high-resolution time-lapse images to examine plant-soil-snow interactions, guide sampling and sensor placements and identify areas likely vulnerable to ecological change in the future.
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Blodgett, Troy A., and Bryan L. Isacks. "Landslide Erosion Rate in the Eastern Cordillera of Northern Bolivia." Earth Interactions 11, no. 19 (December 1, 2007): 1–30. http://dx.doi.org/10.1175/2007ei222.1.
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Abstract The northeastern edge of the Bolivian Eastern Cordillera is an example of a tectonically active plateau margin where orographically enhanced precipitation facilitates very high rates of erosion. The topography of the steepest part of the margin exhibits the classic signature of high erosion rates consisting of high-relief V-shaped valleys where landsliding is the dominant process of hillslope erosion and bedrock rivers are incising into the landscape. The authors mapped landslide scars on multitemporal aerial photographs to estimate hillslope erosion rates. Field surveys of landslide scars are used to calibrate a landslide volume versus area relationship. The mapped area of landsliding, in combination with an estimate of the time for landslide scars to revegetate, leads to an erosion rate estimate. The estimated revegetation time, 10–35 yr, is based on analysis of multitemporal aerial photographs and tree rings. About 4%–6% of two watersheds in the region considered were affected by landslides over the last 10–35 yr. This result implies an erosion rate of 9 ± 5 mm yr−1 assuming that 90% of a single landslide reaches the river on average. Classified Landsat Thematic Mapper images show that landslides are occurring at approximately the same rate all across an approximately 40-km-wide swath within the high-relief zones of the cordillera.
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Kohlhepp, Bernd, Robert Lehmann, Paul Seeber, Kirsten Küsel, Susan E. Trumbore, and Kai U. Totsche. "Aquifer configuration and geostructural links control the groundwater quality in thin-bedded carbonate–siliciclastic alternations of the Hainich CZE, central Germany." Hydrology and Earth System Sciences 21, no. 12 (December 1, 2017): 6091–116. http://dx.doi.org/10.5194/hess-21-6091-2017.
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Abstract. The quality of near-surface groundwater reservoirs is controlled, but also threatened, by manifold surface–subsurface interactions. Vulnerability studies typically evaluate the variable interplay of surface factors (land management, infiltration patterns) and subsurface factors (hydrostratigraphy, flow properties) in a thorough way, but disregard the resulting groundwater quality. Conversely, hydrogeochemical case studies that address the chemical evolution of groundwater often lack a comprehensive analysis of the structural buildup. In this study, we aim to reconstruct the actual spatial groundwater quality pattern from a synoptic analysis of the hydrostratigraphy, lithostratigraphy, pedology and land use in the Hainich Critical Zone Exploratory (Hainich CZE). This CZE represents a widely distributed yet scarcely described setting of thin-bedded mixed carbonate–siliciclastic strata in hillslope terrains. At the eastern Hainich low-mountain hillslope, bedrock is mainly formed by alternated marine sedimentary rocks of the Upper Muschelkalk (Middle Triassic) that partly host productive groundwater resources. Spatial patterns of the groundwater quality of a 5.4 km long well transect are derived by principal component analysis and hierarchical cluster analysis. Aquifer stratigraphy and geostructural links were deduced from lithological drill core analysis, mineralogical analysis, geophysical borehole logs and mapping data. Maps of preferential recharge zones and recharge potential were deduced from digital (soil) mapping, soil survey data and field measurements of soil hydraulic conductivities (Ks). By attributing spatially variable surface and subsurface conditions, we were able to reconstruct groundwater quality clusters that reflect the type of land management in their preferential recharge areas, aquifer hydraulic conditions and cross-formational exchange via caprock sinkholes or ascending flow. Generally, the aquifer configuration (spatial arrangement of strata, valley incision/outcrops) and related geostructural links (enhanced recharge areas, karst phenomena) control the role of surface factors (input quality and locations) vs. subsurface factors (water–rock interaction, cross-formational flow) for groundwater quality in the multi-layered aquifer system. Our investigation reveals general properties of alternating sequences in hillslope terrains that are prone to forming multi-layered aquifer systems. This synoptic analysis is fundamental and indispensable for a mechanistic understanding of ecological functioning, sustainable resource management and protection.
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Sabzevari, T., A. Talebi, R. Ardakanian, and A. Shamsai. "A steady-state saturation model to determine the subsurface travel time (STT) in complex hillslopes." Hydrology and Earth System Sciences Discussions 6, no. 6 (November 23, 2009): 7179–212. http://dx.doi.org/10.5194/hessd-6-7179-2009.
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Abstract. The travel time of subsurface flow in complex hillslopes (hillslopes with different plan shape and profile curvature) is an important parameter in predicting the subsurface flow in catchments. This time depends on the hillslopes geometry (plan shape and profile curvature), soil properties and climate conditions. The saturation capacity of hillslopes affect the travel time of subsurface flow. The saturation capacity, and subsurface travel time of compound hillslopes depend on parameters such as soil depth, porosity, soil hydraulic conductivity, plan shape (convergent, parallel or divergent), hillslope length, profile curvature (concave, straight or convex) and recharge rate to the groundwater table. An equation for calculating subsurface travel time for all complex hillslopes was presented. This equation is a function of the saturation zone length (SZL) on the surface. Saturation zone length of the complex hillslopes was calculated numerically by using the hillslope-storage Boussinesq (hsB) model in the steady state conditions, so an analytical equation was presented for calculating the saturation zone length of the straight hillslopes and all plan shapes geometries. Based on our results, the convergent hillslopes become saturated very soon and they showed longer SZL with shorter travel time compared to the parallel and divergent ones. The subsurface average flow rate in convergent hillslopes is much less than the divergent ones in the steady state conditions. Concerning to subsurface travel time, convex hillslopes have more travel time in comparison to straight and concave hillslopes. The convex hillslopes exhibit more average flow rate than concave hillslopes and their saturation capacity is very low. Finally, the effects of recharge rate variations, average bedrock slope and soil depth on saturation zone extension were investigated.
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Sabzevari, T., A. Talebi, R. Ardakanian, and A. Shamsai. "A steady-state saturation model to determine the subsurface travel time (STT) in complex hillslopes." Hydrology and Earth System Sciences 14, no. 6 (June 4, 2010): 891–900. http://dx.doi.org/10.5194/hess-14-891-2010.
Full textAbstract:
Abstract. The travel time of subsurface flow in complex hillslopes (hillslopes with different plan shape and profile curvature) is an important parameter in predicting the subsurface flow in catchments. This time depends on the hillslopes geometry (plan shape and profile curvature), soil properties and climate conditions. The saturation capacity of hillslopes affect the travel time of subsurface flow. The saturation capacity, and subsurface travel time of compound hillslopes depend on parameters such as soil depth, porosity, soil hydraulic conductivity, plan shape (convergent, parallel or divergent), hillslope length, profile curvature (concave, straight or convex) and recharge rate to the groundwater table. An equation for calculating subsurface travel time for all complex hillslopes was presented. This equation is a function of the saturation zone length (SZL) on the surface. Saturation zone length of the complex hillslopes was calculated numerically by using the hillslope-storage kinematic wave equation for subsurface flow, so an analytical equation was presented for calculating the saturation zone length of the straight hillslopes and all plan shapes geometries. Based on our results, the convergent hillslopes become saturated very soon and they showed longer SZL with shorter travel time compared to the parallel and divergent ones. The subsurface average flow rate in convergent hillslopes is much less than the divergent ones in the steady state conditions. Concerning to subsurface travel time, convex hillslopes have more travel time in comparison to straight and concave hillslopes. The convex hillslopes exhibit more average flow rate than concave hillslopes and their saturation capacity is very low. Finally, the effects of recharge rate variations, average bedrock slope and soil depth on saturation zone extension were investigated.
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Gabet, Emmanuel J. "Lithological and structural controls on river profiles and networks in the northern Sierra Nevada (California, USA)." GSA Bulletin 132, no. 3-4 (July 15, 2019): 655–67. http://dx.doi.org/10.1130/b35128.1.
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Abstract In this study, the strong lithological heterogeneity of the northern Sierra Nevada (California, USA) is exploited to elucidate the role of lithology on river profiles and patterns at the mountain-range scale. The analyses indicate that plutonic, metavolcanic, and quartzite bedrock generally host the steepest river reaches, whereas gentle reaches flow across non-quartzite metasedimentary rocks and fault zones. In addition, the largest immobile boulders are often in the steepest reaches, suggesting that wide joint spacing plays a role in creating steep channels, and a positive relationship between boulder size and hillslope angle highlights the coupling of the hillslope and fluvial systems. With respect to river network configurations, dendritic patterns dominate in the plutonic bedrock, with channels aligned down the slope of the range; in contrast, river reaches in the metamorphic belts are mainly longitudinal and parallel to the structural grain. River profiles and patterns in the northern Sierra Nevada, therefore, bear a strong lithological imprint related to differential erosion. These observations indicate that attempts to infer uplift and tilting of the range based on the gradients and orientations of paleochannel remnants should first account for the effect of bedrock erodibility. Indeed, the differences in gradients of Tertiary paleochannel remnants used to argue for late Cenozoic uplift of the range can be wholly explained by differences in lithology.
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Talebi, A., R. Uijlenhoet, and P. A. Troch. "Soil moisture storage and hillslope stability." Natural Hazards and Earth System Sciences 7, no. 5 (September 12, 2007): 523–34. http://dx.doi.org/10.5194/nhess-7-523-2007.
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Abstract. Recently, we presented a steady-state analytical hillslope stability model to study rain-induced shallow landslides. This model is based on kinematic wave dynamics of saturated subsurface storage and the infinite slope stability assumption. Here we apply the model to investigate the effect of neglecting the unsaturated storage on the assessment of slope stability in the steady-state hydrology. For that purpose we extend the hydrological model to compute the soil pore pressure distribution over the entire flow domain. We also apply this model for hillslopes with non-constant soil depth to compare the stability of different hillslopes and to find the critical slip surface in hillslopes with different geometric characteristics. In order to do this, we incorporate more complex approaches to compute slope stability (Janbu's non-circular method and Bishop's simplified method) in the steady-state analytical hillslope stability model. We compare the safety factor (FS) derived from the infinite slope stability method and the more complex approach for two cases: with and without the soil moisture profile in the unsaturated zone. We apply this extended hillslope stability model to nine characteristic hillslope types with three different profile curvatures (concave, straight, convex) and three different plan shapes (convergent, parallel, divergent). Overall, we find that unsaturated zone storage does not play a critical role in determining the factor of safety for shallow and deep landslides. As a result, the effect of the unsaturated zone storage on slope stability can be neglected in the steady-state hydrology and one can assume the same bulk specific weight below and above the water table. We find that steep slopes with concave profile and convergent plan shape have the least stability. We also demonstrate that in hillslopes with non-constant soil depth (possible deep landslides), the ones with convex profiles and convergent plan shapes have slip surfaces with the minimum safety factor near the outlet region. In general, when plan shape changes from divergent to convergent, stability decreases for all length profiles. Finally, we show that the applied slope stability methods and steady-state hydrology model based on the relative saturated storage can be used safely to investigate the relation between hillslope geometry and hillslope stability.
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Levy, Joseph S., Andrew G. Fountain, Michael N. Gooseff, J. E. Barrett, Robert Vantreese, Kathy A. Welch, W. Berry Lyons, Uffe N. Nielsen, and Diana H. Wall. "Water track modification of soil ecosystems in the Lake Hoare basin, Taylor Valley, Antarctica." Antarctic Science 26, no. 2 (July 10, 2013): 153–62. http://dx.doi.org/10.1017/s095410201300045x.
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AbstractWater tracks are zones of high soil moisture that route shallow groundwater down-slope, through the active layer and above the ice table. A water track in Taylor Valley, McMurdo Dry Valleys, was analysed for surface hydrogeological, geochemical, and biological characteristics in order to test the hypothesis that water tracks provide spatial structure to Antarctic soil ecosystems by changing the physical conditions in the soil environment within the water tracks from those outside the water tracks. The presence of the water track significantly affected the distribution of biotic and abiotic ecosystem parameters: increasing soil moisture, soil salinity, and soil organic matter within the water track relative to soils outside the water track, and reducing soil phosphate, soil pH, and the population of nematodes and other invertebrates in water track soils relative to off track soils. These results suggest that water tracks are distinct and extreme ecological zones in Taylor Valley that provide long-range (kilometre to multi- kilometre) structure to Antarctic hillslope ecosystems through physical control on soil moisture and solute content. Contrary to expectations, these high soil-moisture sites are not hotspots for faunal biological activity because high soil salinity makes them suitable habitats for only the most halo-tolerant organisms.
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Penna, D., H. J. Tromp-van Meerveld, A. Gobbi, M. Borga, and G. Dalla Fontana. "The influence of soil moisture on threshold runoff generation processes in an alpine headwater catchment." Hydrology and Earth System Sciences Discussions 7, no. 5 (October 15, 2010): 8091–124. http://dx.doi.org/10.5194/hessd-7-8091-2010.
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Abstract. This study investigates the role of soil moisture on the threshold runoff response in a small headwater catchment in the Italian Alps that is characterised by steep hillslopes and a distinct riparian zone. This study focuses on: (i) the threshold soil moisture-runoff relationship and the influence of catchment topography on this relation; (ii) the temporal dynamics of soil moisture, streamflow and groundwater that characterize the catchment's response to rainfall during dry and wet periods; and (iii) the combined effect of antecedent wetness conditions and rainfall amount on hillslope and riparian runoff. Our results highlight the strong control exerted by soil moisture on runoff in this catchment: a sharp threshold exists in the relationship between soil water content and runoff coefficient, streamflow, and hillslope-averaged depth to water table. Low runoff ratios were related to the response of the riparian zone, which was always close to saturation. High runoff ratios occurred during wet antecedent conditions, when the soil moisture threshold was exceeded. In these cases, subsurface flow was activated on hillslopes, which became major contributors to runoff. Antecedent wetness conditions also controlled the catchment's response time: during dry periods, streamflow reacted and peaked prior to hillslope soil moisture whereas during wet conditions the opposite occurred. This difference resulted in a hysteretic behaviour in the soil moisture-streamflow relationship. Finally, the influence of antecedent moisture conditions on runoff was also evident in the relation between cumulative rainfall and total stormflow. Small storms during dry conditions produced low runoff amounts, mainly from overland flow from the near saturated riparian zone. Conversely, for rainfall events during wet conditions, hillslopes contributed to streamflow and higher runoff values were observed.
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Poblador, Sílvia, Anna Lupon, Santiago Sabaté, and Francesc Sabater. "Soil water content drives spatiotemporal patterns of CO<sub>2</sub> and N<sub>2</sub>O emissions from a Mediterranean riparian forest soil." Biogeosciences 14, no. 18 (September 21, 2017): 4195–208. http://dx.doi.org/10.5194/bg-14-4195-2017.
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Abstract. Riparian zones play a fundamental role in regulating the amount of carbon (C) and nitrogen (N) that is exported from catchments. However, C and N removal via soil gaseous pathways can influence local budgets of greenhouse gas (GHG) emissions and contribute to climate change. Over a year, we quantified soil effluxes of carbon dioxide (CO2) and nitrous oxide (N2O) from a Mediterranean riparian forest in order to understand the role of these ecosystems on catchment GHG emissions. In addition, we evaluated the main soil microbial processes that produce GHG (mineralization, nitrification, and denitrification) and how changes in soil properties can modify the GHG production over time and space. Riparian soils emitted larger amounts of CO2 (1.2–10 g C m−2 d−1) than N2O (0.001–0.2 mg N m−2 d−1) to the atmosphere attributed to high respiration and low denitrification rates. Both CO2 and N2O emissions showed a marked (but antagonistic) spatial gradient as a result of variations in soil water content across the riparian zone. Deep groundwater tables fueled large soil CO2 effluxes near the hillslope, while N2O emissions were higher in the wet zones adjacent to the stream channel. However, both CO2 and N2O emissions peaked after spring rewetting events, when optimal conditions of soil water content, temperature, and N availability favor microbial respiration, nitrification, and denitrification. Overall, our results highlight the role of water availability on riparian soil biogeochemistry and GHG emissions and suggest that climate change alterations in hydrologic regimes can affect the microbial processes that produce GHG as well as the contribution of these systems to regional and global biogeochemical cycles.
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Yeakley, J. A., W. T. Swank, L. W. Swift, G. M. Hornberger, and H. H. Shugart. "Soil moisture gradients and controls on a southern Appalachian hillslope from drought through recharge." Hydrology and Earth System Sciences 2, no. 1 (March 31, 1998): 41–49. http://dx.doi.org/10.5194/hess-2-41-1998.
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Abstract. Soil moisture gradients along hillslopes in humid watersheds, although indicated by vegetation gradients and by studies using models, have been difficult to confirm empirically. While soil properties and topographic features are the two general physio-graphic factors controlling soil moisture on hillslopes, studies have shown conflicting results regarding which factor is more important. The relative importance of topographic and soil property controls was examined in an upland forested watershed at the Coweeta Hydrologic Laboratory in the southern Appalachian mountains. Soil moisture was measured along a hillslope transect with a mesic-to-xeric forest vegetation gradient over a period spanning precipitation extremes. The hillslope was transect instrumented with a time domain reflectometry (TDR) network at two depths. Soil moisture was measured during a severe autumn drought and subsequent winter precipitation recharge. In the upper soil depth (0-30 cm), moisture gradients persisted throughout the measurement period, and topography exerted dominant control. For the entire root zone (0-90 cm), soil moisture gradients were found only during drought. Control on soil moisture was due to both topography and storage before drought. During and after recharge, variations in soil texture and horizon distribution exerted dominant control on soil moisture content in the root zone (0-90 cm). These results indicate that topographic factors assert more control over hillslope soil moisture during drier periods as drainage progresses, while variations in soil water storage properties are more important during wetter periods. Hillslope soil moisture gradients in southern Appalachian watersheds appear to be restricted to upper soil layers, with deeper hillslope soil moisture gradients occurring only with sufficient drought.
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Penna, D., H. J. Tromp-van Meerveld, A. Gobbi, M. Borga, and G. Dalla Fontana. "The influence of soil moisture on threshold runoff generation processes in an alpine headwater catchment." Hydrology and Earth System Sciences 15, no. 3 (March 1, 2011): 689–702. http://dx.doi.org/10.5194/hess-15-689-2011.
Full textAbstract:
Abstract. This study investigates the role of soil moisture on the threshold runoff response in a small headwater catchment in the Italian Alps that is characterised by steep hillslopes and a distinct riparian zone. This study focuses on: (i) the threshold soil moisture-runoff relationship and the influence of catchment topography on this relation; (ii) the temporal dynamics of soil moisture, streamflow and groundwater that characterize the catchment's response to rainfall during dry and wet periods; and (iii) the combined effect of antecedent wetness conditions and rainfall amount on hillslope and riparian runoff. Our results highlight the strong control exerted by soil moisture on runoff in this catchment: a sharp threshold exists in the relationship between soil water content and runoff coefficient, streamflow, and hillslope-averaged depth to water table. Low runoff ratios were likely related to the response of the riparian zone, which was almost always close to saturation. High runoff ratios occurred during wet antecedent conditions, when the soil moisture threshold was exceeded. In these cases, subsurface flow was activated on hillslopes, which became a major contributor to runoff. Antecedent wetness conditions also controlled the catchment's response time: during dry periods, streamflow reacted and peaked prior to hillslope soil moisture whereas during wet conditions the opposite occurred. This difference resulted in a hysteretic behaviour in the soil moisture-streamflow relationship. Finally, the influence of antecedent moisture conditions on runoff was also evident in the relation between cumulative rainfall and total stormflow. Small storms during dry conditions produced low stormflow amounts, likely mainly from overland flow from the near saturated riparian zone. Conversely, for rainfall events during wet conditions, higher stormflow values were observed and hillslopes must have contributed to streamflow.
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Cohen, Denis, and Massimiliano Schwarz. "Tree-root control of shallow landslides." Earth Surface Dynamics 5, no. 3 (August 17, 2017): 451–77. http://dx.doi.org/10.5194/esurf-5-451-2017.
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Abstract. Tree roots have long been recognized to increase slope stability by reinforcing the strength of soils. Slope stability models usually include the effects of roots by adding an apparent cohesion to the soil to simulate root strength. No model includes the combined effects of root distribution heterogeneity, stress-strain behavior of root reinforcement, or root strength in compression. Recent field observations, however, indicate that shallow landslide triggering mechanisms are characterized by differential deformation that indicates localized activation of zones in tension, compression, and shear in the soil. Here we describe a new model for slope stability that specifically considers these effects. The model is a strain-step discrete element model that reproduces the self-organized redistribution of forces on a slope during rainfall-triggered shallow landslides. We use a conceptual sigmoidal-shaped hillslope with a clearing in its center to explore the effects of tree size, spacing, weak zones, maximum root-size diameter, and different root strength configurations. Simulation results indicate that tree roots can stabilize slopes that would otherwise fail without them and, in general, higher root density with higher root reinforcement results in a more stable slope. The variation in root stiffness with diameter can, in some cases, invert this relationship. Root tension provides more resistance to failure than root compression but roots with both tension and compression offer the best resistance to failure. Lateral (slope-parallel) tension can be important in cases when the magnitude of this force is comparable to the slope-perpendicular tensile force. In this case, lateral forces can bring to failure tree-covered areas with high root reinforcement. Slope failure occurs when downslope soil compression reaches the soil maximum strength. When this occurs depends on the amount of root tension upslope in both the slope-perpendicular and slope-parallel directions. Roots in tension can prevent failure by reducing soil compressive forces downslope. When root reinforcement is limited, a crack parallel to the slope forms near the top of the hillslope. Simulations with roots that fail across this crack always resulted in a landslide. Slopes that did not form a crack could either fail or remain stable, depending on root reinforcement. Tree spacing is important for the location of weak zones but tree location on the slope (with respect to where a crack opens) is as important. Finally, for the specific cases tested here, intermediate-sized roots (5 to 20 mm in diameter) appear to contribute most to root reinforcement. Our results show more complex behaviors than can be obtained with the traditional slope-uniform, apparent-cohesion approach. A full understanding of the mechanisms of shallow landslide triggering requires a complete re-evaluation of this traditional approach that cannot predict where and how forces are mobilized and distributed in roots and soils, and how these control shallow landslides shape, size, location, and timing.
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Leach, J. A., and R. D. Moore. "Winter stream temperature in the rain-on-snow zone of the Pacific Northwest: influences of hillslope runoff and transient snow cover." Hydrology and Earth System Sciences 18, no. 2 (February 27, 2014): 819–38. http://dx.doi.org/10.5194/hess-18-819-2014.
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Abstract. Stream temperature dynamics during winter are less well studied than summer thermal regimes, but the winter season thermal regime can be critical for fish growth and development in coastal catchments. The winter thermal regimes of Pacific Northwest headwater streams, which provide vital winter habitat for salmonids and their food sources, may be particularly sensitive to changes in climate because they can remain ice-free throughout the year and are often located in rain-on-snow zones. This study examined winter stream temperature patterns and controls in small headwater catchments within the rain-on-snow zone at the Malcolm Knapp Research Forest, near Vancouver, British Columbia, Canada. Two hypotheses were addressed by this study: (1) winter stream temperatures are primarily controlled by advective fluxes associated with runoff processes and (2) stream temperatures should be depressed during rain-on-snow events, compared to rain-on-bare-ground events, due to the cooling effect of rain passing through the snowpack prior to infiltrating the soil or being delivered to the stream as saturation-excess overland flow. A reach-scale energy budget analysis of two winter seasons revealed that the advective energy input associated with hillslope runoff overwhelms vertical energy exchanges (net radiation, sensible and latent heat fluxes, bed heat conduction, and stream friction) and hyporheic energy fluxes during rain and rain-on-snow events. Historical stream temperature data and modelled snowpack dynamics were used to explore the influence of transient snow cover on stream temperature over 13 winters. When snow was not present, daily stream temperature during winter rain events tended to increase with increasing air temperature. However, when snow was present, stream temperature was capped at about 5 °C, regardless of air temperature. The stream energy budget modelling and historical analysis support both of our hypotheses. A key implication is that climatic warming may generate higher winter stream temperatures in the rain-on-snow zone due to both increased rain temperature and reduced cooling effect of snow cover.
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Leach, J. A., and R. D. Moore. "Winter stream temperature in the rain-on-snow zone of the Pacific northwest: influences of hillslope runoff and transient snow cover." Hydrology and Earth System Sciences Discussions 10, no. 10 (October 31, 2013): 12951–3003. http://dx.doi.org/10.5194/hessd-10-12951-2013.
Full textAbstract:
Abstract. Stream temperature dynamics during winter are less well studied than summer thermal regimes, but the winter season thermal regime can be critical for fish growth and development in coastal catchments. The winter thermal regimes of Pacific Northwest headwater streams, which provide vital winter habitat for salmonids and their food sources, may be particularly sensitive to changes in climate because they can remain ice-free throughout the year and are often located in rain-on-snow zones. This study examined winter stream temperature patterns and controls in small headwater catchments within the rain-on-snow zone at the Malcolm Knapp Research Forest, near Vancouver, British Columbia, Canada. Two hypotheses were addressed by this study: (1) winter stream temperatures are primarily controlled by advective fluxes associated with runoff processes and (2) stream temperatures should be depressed during rain-on-snow events, compared to rain-on-bare-ground, due to the cooling effect of rain passing through the snowpack prior to infiltrating the soil or being delivered to the stream as saturation-excess overland flow. A reach-scale energy budget analysis of two winter seasons revealed that the advective energy input associated with hillslope runoff overwhelms the effects of energy exchanges at the stream surface during rain and rain-on-snow events. Historical stream temperature data and modelled snowpack dynamics were used to explore the influence of transient snow cover on stream temperature over 13 winters. When snow was not present, daily stream temperature during winter rain events tended to increase with increasing air temperature. However, when snow was present, stream temperature was capped at about 5 °C, regardless of air temperature. The stream energy budget modelling and historical analysis support both of our hypotheses. A key implication is that climatic warming may generate higher winter stream temperatures in the rain-on-snow zone due to both increased rain temperature and reduced cooling effect of snow cover.
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Liu, Muxing, Wenzheng Du, and Hailin Zhang. "Changes of preferential flow path on different altitudinal zones in the Three Gorges Reservoir Area, China." Canadian Journal of Soil Science 94, no. 2 (May 2014): 177–88. http://dx.doi.org/10.4141/cjss2013-021.
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Liu, M., Du, W. and Zhang, H. 2014. Changes of preferential flow path on different altitudinal zones in the Three Gorges Reservoir Area, China. Can. J. Soil Sci. 94: 177–188. Preferential flow in soil macropores plays an important role in runoff control and soil and water conservation. The aim of this study was to investigate the distribution of preferential flow paths in the soil profile of various altitudinal belts, analyze its variation among different soil horizons, and define the cause of soil macropores. A dye tracer method combined with photographic analysis was conducted for four hillslope sites in the Three Gorges Reservoir Area of China (TGRA). The results show that stained area proportion, as well as its vertical distribution in soil sections, presented varied patterns due to changes of forest vegetation and soil type with altitude. Stained area ratio of soil profiles increased, while stained depth decreased with increasing altitude. For soil sections in the subalpine belt, mid-mountain belt, and low-mountain belt of TGRA, stained area ratios were 62, 42, and 45%, and stained depths were 52.4, 56.4, and 69.5 cm, respectively. For brown earth covered with subalpine temperate deciduous broad-leaved forest, stained area ratios were the largest, but dyed patches were concentrated in the humus horizon. For yellow earth covered with low-mountain warm coniferous forest, stained depth reached 69.5 cm, and stained patches existed in the total soil profile. Compared with forest soil, stained depth and stained area ratio of abandoned farmland in low-mountain belt were lower, and the depth of dye infiltration was even shallower.
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Watts, L. G., and A. Calver. "Effects of Spatially-Distributed Rainfall on Runoff for a Conceptual Catchment." Hydrology Research 22, no. 1 (February 1, 1991): 1–14. http://dx.doi.org/10.2166/nh.1991.0001.
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A physically-based rainfall-runoff model is used to investigate effects of moving storms on the runoff hydrograph of throughflow dominated idealised catchments. Simulations are undertaken varying the storm speed, direction, intensity, the part of the catchment affected by rainfall, and the spatial definition of rainfall zones. For a 100 km2 catchment, under the circumstances investigated, an efficient spatial resolution of rainfall data is around 2.5 km along the path of the storm. Storms moving downstream produce earlier, higher peaks than do storms moving upstream. Error is most likely to be introduced into lumped-rainfall predictions for slower storm speeds, and the likely direction of this error can be specified. Differences in magnitude of peak response between downstream and upstream storm directions reach a maximum at a storm speed and direction similar to the average peak channel velocity. These results are qualitatively similar to those reported for overland flow dominated catchments, but differences in peak runoff between downstream and upstream storm directions are much smaller where rainfall inputs are modified by a period of hillslope throughflow.
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Ireson, A. M., and A. P. Butler. "A critical assessment of simple recharge models: application to the UK Chalk." Hydrology and Earth System Sciences Discussions 9, no. 10 (October 25, 2012): 12061–102. http://dx.doi.org/10.5194/hessd-9-12061-2012.
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Abstract. A framework for the rigorous quantification of the timing and magnitude of groundwater recharge is proposed. This involves developing a physically based model for the flow processes in the unsaturated and saturated zones that is consistent with the conceptualisation of the system, and with field observations. Subsequently, the essential behaviour of this model is emulated using a simpler model that can be applied within operational groundwater models. We take a UK Chalk aquifer as a case study. Flow processes are simulated convincingly using a dual permeability, equivalent continuum, Richards' equation model, applied to a 2-D hillslope transect along which four monitoring wells recorded water levels in the unconfined aquifer. A simple conventional recharge model that has been widely used was calibrated to reproduce the water table response simulated by the physically based model. The performance in reproducing the water table was surprisingly good, given the known discrepancies between the actual processes and the model representation. However, comparisons of recharge fluxes simulated by each model highlighted problems with the recharge processes in the simple model. Specifically, artificial bypass flow events during the summer were compensating for recharge that should have come from slow, continual drainage of the unsaturated zone. Such a model may still be useful for assessment of groundwater resources on a monthly basis, under non-extreme climatic conditions. However, under extreme wet or dry conditions, or under a changed climate the predictive capacity of such models is likely to be inadequate.
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Chen, X., and D. Wang. "Evaluating the effect of partial contributing storage on the storage–discharge function from recession analysis." Hydrology and Earth System Sciences 17, no. 10 (October 31, 2013): 4283–96. http://dx.doi.org/10.5194/hess-17-4283-2013.
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Abstract. Hydrograph recession during dry periods has been used to construct water storage–discharge relationships and to quantify storage dynamics and evaporation when streamflow data is available. However, variable hydrologic connectivity among hillslope–riparian–stream zones may affect the lumped storage–discharge relationship, and as a result, affect the estimation of evaporation and storage change. Given observations of rainfall and runoff, and remote-sensing-based observations of evaporation, the ratio (α) between estimated daily evaporation from recession analysis and observed evaporation, and the ratio (β) between estimated contributing storage and total watershed storage are computed for 9 watersheds located in different climate regions. Both evaporation and storage change estimation from recession analysis are underestimated due to the effect of partial contributing storage, particularly when the discharge is low. It was found that the values of α decrease significantly during individual recession events, while the values of β are relatively stable during a recession event. The values of β are negatively correlated with the water table depth and vary significantly among recession events. The partial contributing storage effect is one possible cause for the multi-valued storage–discharge relationship.
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Chen, X., and D. Wang. "Evaluating the effect of partial contributing storage on storage–discharge function from recession analysis." Hydrology and Earth System Sciences Discussions 10, no. 5 (May 7, 2013): 5767–98. http://dx.doi.org/10.5194/hessd-10-5767-2013.
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Abstract. Hydrograph recession during dry periods has been used to construct water storage–discharge relationship, and to quantify storage dynamics and evaporation when streamflow data is available. However, variable hydrologic connectivity among hillslope-riparian-stream zones may affect the lumped storage–discharge relationship, and as a result, affect the estimation of evaporation and storage change. Given observations of rainfall and runoff, and remote sensing-based observation of evaporation, the ratio (α) between estimated daily evaporation from recession analysis and observed evaporation, and the ratio (β) between estimated contributing storage and total watershed storage are computed for 9 watersheds located in different climate regions. Both evaporation and storage change estimation from recession analysis are underestimated due to the effect of partial contributing storage, particularly when the discharge is low. It was found that the values of α decrease significantly during individual recession events, while the values of β are relatively stable during a recession event. The values of β are negatively correlated with the water table depth, and vary significantly among recession events. The partial contributing storage effect is one possible cause for the multi-valued storage–discharge relationship.
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Wilcox, Evan J., Dawn Keim, Tyler de Jong, Branden Walker, Oliver Sonnentag, Anastasia E. Sniderhan, Philip Mann, and Philip Marsh. "Tundra shrub expansion may amplify permafrost thaw by advancing snowmelt timing." Arctic Science 5, no. 4 (December 1, 2019): 202–17. http://dx.doi.org/10.1139/as-2018-0028.
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The overall spatial and temporal influence of shrub expansion on permafrost is largely unknown due to uncertainty in estimating the magnitude of many counteracting processes. For example, shrubs shade the ground during the snow-free season, which can reduce active layer thickness. At the same time, shrubs advance the timing of snowmelt when they protrude through the snow surface, thereby exposing the active layer to thawing earlier in spring. Here, we compare 3056 in situ frost table depth measurements split between mineral earth hummocks and organic inter-hummock zones across four dominant shrub–tundra vegetation types. Snow-free date, snow depth, hummock development, topography, and vegetation cover were compared to frost table depth measurements using a structural equation modeling approach that quantifies the direct and combined interacting influence of these variables. Areas of birch shrubs became snow free earlier regardless of snow depth or hillslope aspect because they protruded through the snow surface, leading to deeper hummock frost table depths. Projected increases in shrub height and extent combined with projected decreases in snowfall would lead to increased shrub protrusion across the Arctic, potentially deepening the active layer in areas where shrub protrusion advances the snow-free date.
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Vlček, Lukáš, Kristýna Falátková, and Philipp Schneider. "Identification of runoff formation with two dyes in a mid-latitude mountain headwater." Hydrology and Earth System Sciences 21, no. 6 (June 23, 2017): 3025–40. http://dx.doi.org/10.5194/hess-21-3025-2017.
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Abstract. Subsurface flow in peat bog areas and its role in the hydrologic cycle has garnered increased attention as water scarcity and floods have increased due to a changing climate. In order to further probe the mechanisms in peat bog areas and contextualize them at the catchment scale, this experimental study identifies runoff formation at two opposite hillslopes in a peaty mountain headwater; a slope with organic peat soils and a shallow phreatic zone (0.5 m below surface), and a slope with mineral Podzol soils and no detectable groundwater (> 2 m below surface). Similarities and differences in infiltration, percolation and preferential flow paths between both hillslopes could be identified by sprinkling experiments with Brilliant Blue and Fluorescein sodium. To our knowledge, this is the first time these two dyes have been compared in their ability to stain preferential flow paths in soils. Dye-stained soil profiles within and downstream of the sprinkling areas were excavated parallel (lateral profiles) and perpendicular (frontal profiles) to the slopes' gradients. That way preferential flow patterns in the soil could be clearly identified. The results show that biomat flow, shallow subsurface flow in the organic topsoil layer, occurred at both hillslopes; however, at the peat bog hillslope it was significantly more prominent. The dye solutions infiltrated into the soil and continued either as lateral subsurface pipe flow in the case of the peat bog, or percolated vertically towards the bedrock in the case of the Podzol. This study provides evidence that subsurface pipe flow, lateral preferential flow along decomposed tree roots or logs in the unsaturated zone, is a major runoff formation process at the peat bog hillslope and in the adjacent riparian zone.
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Patton, A. I., S. R. Rathburn, D. Capps, R. A. Brown, and J. S. Singleton. "Lithologic, geomorphic, and permafrost controls on recent landsliding in the Alaska Range." Geosphere 16, no. 6 (November 2, 2020): 1479–94. http://dx.doi.org/10.1130/ges02256.1.
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Abstract Because landslide regimes are likely to change in response to climate change in upcoming decades, the need for mechanistic understanding of landslide initiation and up-to-date landslide inventory data is greater than ever. We conducted surficial geologic mapping and compiled a comprehensive landslide inventory of the Denali National Park road corridor to identify geologic and geomorphic controls on landslide initiation in the Alaska Range. The supplemental geologic map refines and improves the resolution of mapping in the study area and adds emphasis on surficial units, distinguishing multiple glacial deposits, hillslope deposits, landslides, and alluvial units that were previously grouped. Results indicate that slope angle, lithology, and thawing ice-rich permafrost exert first-order controls on landslide occurrence. The majority (84%) of inventoried landslides are <0.01 km2 in area and occur most frequently on slopes with a bimodal distribution of slope angles with peaks at 18° and 28°. Of the 85 mapped landslides, a disproportionate number occurred in unconsolidated sediments and in felsic volcanic rocks. Weathering of feldspar within volcanic rocks and subsequent interactions with groundwater produced clay minerals that promote landslide initiation by impeding subsurface conductivity and reducing shear strength. Landslides also preferentially initiated within permafrost, where modeled mean decadal ground temperature is −0.2 ± 0.04 °C on average, and active layer thickness is ∼1 m. Landslides that initiated within permafrost occurred on slope angles ∼7° lower than landslides on seasonally thawed hillslopes. The bimodal distribution of slope angles indicates that there are two primary drivers of landslide failure within discontinuous permafrost zones: (1) atmospheric events (snowmelt or rainfall) that saturate the subsurface, as is commonly observed in temperate settings, and (2) shallow-angle landslides (<20° slopes) in permafrost demonstrate that permafrost and ice thaw are also important triggering mechanisms in the study region. Melting permafrost reduces substrate shear strength by lowering cohesion and friction along ice boundaries. Increased permafrost degradation associated with climate change brings heightened focus to low-angle slopes regionally as well as in high-latitude areas worldwide. Areas normally considered of low landslide potential will be more susceptible to shallow-angle landslides in the future. Our landslide inventory and analyses also suggest that landslides throughout the Alaska Range and similar climatic zones are most likely to occur where low-cohesion unconsolidated material is available or where alteration of volcanic rocks produces sufficient clay content to reduce rock and/or sediment strength. Permafrost thaw is likely to exacerbate slope instability in these materials and expand areas impacted by landslides.
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An, Jung-Gi. "Test for the TOPMODEL′s Ability to Predict Water Table Depths of the Transient Saturation Zones which Are Formed on the Steep Hillslope." Journal of Korea Water Resources Association 36, no. 6 (December 1, 2003): 1035–47. http://dx.doi.org/10.3741/jkwra.2003.36.6.1035.
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Garvelmann, J., C. Külls, and M. Weiler. "A porewater – based stable isotope approach for the investigation of subsurface hydrological processes." Hydrology and Earth System Sciences Discussions 8, no. 5 (October 11, 2011): 9089–112. http://dx.doi.org/10.5194/hessd-8-9089-2011.
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Abstract. Predicting and understanding subsurface flowpaths is still a crucial issue in hydrological research. We present an experimental approach to reveal present and past subsurface flowpaths of water in the unsaturated and saturated zone. Two hillslopes in a humid moutainous catchment have been investigated. The H2O(liquid) – H2O(vapor) equilibration laser spectroscopy method was used to obtain high resolution δ2H vertical depth profiles of porewater at various points along a fall line of a pasture hillslope in the southern Black Forest, Germany. The Porewater Stable Isotope Profile (PSIP) approach was developed to use the integrated information of several vertical depth profiles of deuterium along two transects at the hillslopes. Different shapes of depth profiles were observed in relation to hillslope position. The statistical variability (inter-quartile range and standard deviation) of each profile was used to characterize different types of depth profiles. The profiles upslope or with a weak affinity for saturation as indicated by a low topographic wetness index preserve the isotopic input signal by precipitation with a distinct seasonal variability. These observations indicate mainly vertical movement of soil water in the upper part of the hillslope before sampling. The profiles downslope or at locations with a strong affinity for saturation do not show a similar seasonal isotopic signal. The input signal is erased in the foothills and a large proportion of pore water samples are close to the isotopic values of δ2H in stream water during base flow. Near the stream indications for efficient mixing of water from lateral subsurface flow paths with vertical percolation are found.
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Perez Filho, Archimedes, Vinícius B. Moreira, Luca Lämmle, André O. Souza, Bruno A. Torres, Pedro I. C. Aderaldo, Éverton V. Valezio, et al. "Genesis and Distribution of Low Fluvial Terraces Formed by Holocene Climate Pulses in Brazil." Water 14, no. 19 (September 22, 2022): 2977. http://dx.doi.org/10.3390/w14192977.
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Low fluvial terraces present azonal spatialization, encompassing several geomorphological compartments and climate zones in Brazil. Their genesis is directly related to river dynamics. When influenced by allogenic forces, such as Holocene climate pulses, it results in channel incision and posterior abandonment of the floodplain. Relatively plain landforms at different altimetric levels identified between the current floodplain and hillslope (low river terraces) are a result of these processes. Previous works using Optically Stimulated Luminescence (OSL) in low terraces of several rivers in Brazil have indicated morpho-chronologic similarities between depositional events, raising the hypothesis of feedbacks and fluvial adjustments relatively simultaneous to Holocene climate events. Considering these dynamics, this study employed OSL to obtain absolute dating information for 114 samples taken from distinct levels of the low river terraces of 30 rivers in Brazil, integrating the database of the IG-UNICAMP laboratory of Geomorphology and Environmental Analysis. Based on the data and statistical analysis (cluster and correlation analysis), this study aimed to identify relationships between different variables which might have controlled spatial homogenous and heterogeneous feedbacks during distinct paleoenvironmental contexts. The proposed methodology tested a fundamental hypothesis of the regional climatic geomorphology, and the results obtained may contribute to future discussions on the relationship between low river terraces and anthropic occupation.
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Sheridan, Chris D., and Deanna H. Olson. "Amphibian assemblages in zero-order basins in the Oregon Coast Range." Canadian Journal of Forest Research 33, no. 8 (August 1, 2003): 1452–77. http://dx.doi.org/10.1139/x03-038.
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Zero-order basins, extending from ridgelines to the initiation of first-order streams, were sampled in the Coast Range of Oregon to (i) characterize spatial distribution patterns of amphibian species and assemblages along longitudinal and lateral gradients, and relative to three geomorphic surfaces (valleys, headmost areas, and slopes); and (ii) develop empirical specieshabitat models. Unmanaged zero-order basins were hotspots for amphibian diversity, with significant differences across geomorphic gradients. Captures of riparian-associated amphibians were higher in valley areas, usually within 2 m of basin center. Upland-associated amphibians were captured two times farther from basin centers than riparian-associated species, but highest densities occurred only 25 m from basin center. The most useful empirical models related captures of individual amphibian species to geomorphic, disturbance, moisture, and overstory variables. Ordination and indicator species analysis characterized geomorphic and other environmental gradients in amphibian assemblages and suggested spatial compression of fluvial habitats and riparian-associated species in zero-order basins, in comparison with downstream areas. Our findings have implications for headwater areas managed to hedge risk to and uncertainty in amphibian persistence, namely in the delineation of zones with species management priority, and in the maintenance of natural fluvial and hillslope disturbance regimes, along with the microhabitat features created by these regimes.
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Orfánus, Tomáš, Marián Jenčo, Juraj Bebej, and Martin Benko. "Simulation of the effects of forest roads on stormflow generation using GIS and 2D vadose zone hydrological model." Ekológia (Bratislava) 36, no. 1 (March 1, 2017): 25–39. http://dx.doi.org/10.1515/eko-2017-0003.
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Abstract There was a destructive flood on Gidra river on June induced by 104-mm rainfall during 3 h on 7 June 2011. The total flood discharge was estimated to be 531,000 m3. The upper part of the Gidra river catchment is forested by more than 95%, but the forest floor has been disrupted to a large extent by intensive logging activities in the basin. Forest road density is up to 10 km/km2 in the catchment. The field inspections in the catchments revealed that approximately 25% of forest roads have been deepened down to the less permeable subsoil directly during their construction or by subsequent traffic and soil erosion. Forest roads affect runoff generation via two mechanisms: (1) generation of infiltration-excess runoff on road surfaces and (2) capturing of hillslope surface and subsurface water by road incisions. Infiltration-excess water runoff from all compacted surfaces was estimated to be about 54,000 m3 by simply multiplying the compacted area by the difference between the precipitation and infiltration. More challenging was to quantify the transformation of hillslope water to the road-surface runoff. We have suggested the methodological approach that combines the GIS analyses of the terrain with mathematical simulations of the subsurface water exfiltration from hillslopes to the road surfaces using HYDRUS 2D model. Simulations based on the variability of slope inclinations and slope lengths within catchment revealed that drainage of the upward hillslopes by forest roads and deeper logging lines increased the forest road runoff by another 6,000-15,000 m3 of water.
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Šanda, M., A. Kulasová, and M. Císlerová. "Hydrological processes in the subsurface investigated by water isotopes and silica." Soil and Water Research 4, Special Issue 2 (March 19, 2010): S83—S92. http://dx.doi.org/10.17221/472-swr.
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The hillslope rainfall-outflow interactions, groundwater fluxes, and hydrological balance were examined in the small mountainous headwater catchment Uhlířská, the Jizera Mountains, the Czech Republic. The hillslope soil profile is formed by paleozoic crystalline bedrock overlaid by shallow highly permeable shallow Cambisol, and by thick saturated glacial deposits in the valley, overlaid by Histosol. A quick communication of the vadose zone with the granitic bedrock via preferential subsurface flowpaths is hypothesised, in agreement with the observation of storm-caused instant water transformation to outflow through the permeable Cambisol. A quick response of a high magnitude outflow occurs regularly, although the surface runoff is very rare. Standard climatic and hydrological monitoring in the Uhlířská catchment is supplemented by the measurements of the soil moisture, soil pore water suction, subsurface hillslope stormflow in the vadose zone, and water table fluctuation in the saturated subsurface, and is accompanied by water sampling for the analyses of the contents of the isotope <SUP>18</SUP>O and <SUP>2</SUP>H and geochemical tracer silica in the form of SiO<SUB>2</SUB>. The episode based isotopic data serve for the separation of the outflow hydrograph to determine the contributions of the event and pre-event water in the hypodermic hillslope outflow and in the catchment outflow. The variation of silica content in the water cycle components was examined to assess the contributions from the soil profile and the aquifer. Up to 75% of the event catchment runoff was assigned to pre-event water, of which about 50% had been stored in the shallow soil subsurface on the hillslopes. The hypothesis was confirmed that the hillslope soil layers control the distribution of the flow into the groundwater recharge and/or the shallow subsurface flow during the rainfallrunoff episode.
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Manaljav, Samdandorj, Andrea Farsang, Károly Barta, Zalán Tobak, Szabolcs Juhász, Péter Balling, and Izabella Babcsányi. "The Impact of Soil Erosion on the Spatial Distribution of Soil Characteristics and Potentially Toxic Element Contents in a Sloping Vineyard in Tállya, Ne Hungary." Journal of Environmental Geography 14, no. 1-2 (April 1, 2021): 47–57. http://dx.doi.org/10.2478/jengeo-2021-0005.
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Abstract Soil erosion is a main problem in sloping vineyards, which can dramatically affect soil quality and fertility. The present study aimed to evaluate the spatial patterns of selected physico-chemical soil characteristics and the soil’s potentially toxic element (PTE) contents in the context of erosion. The study was conducted in a 0.4 ha vineyard plot on a steep slope in Tállya, part of the wine-growing region of Tokaj-Hegyalja (Hungary). A total of 20 topsoil samples (0-10 cm) were collected and analysed for PTEs (B, Co, Ba, Sr, Mn, Ni, Cr, Pb, Zn, and Cu), soil pH (deionized water and KCl solution), particle-size distribution, soil organic matter (SOM), (nitrate+nitrite)-N, P2O5, and carbonate content. Among the selected PTEs, only Cu (125±27 mg/kg) exceeds the Hungarian standards set for soils and sediments (75 mg/kg) due to the long-term use of Cu-based pesticides in the vineyard. Examined PTEs are negatively correlated with the sand content of the topsoil, except for Mn, while the significant positive relationship with the clay content shows the role of clay in retaining PTEs in soil. SOM seems to play a minor role in binding PTEs, as Cu is the only element for which a significant correlation with the SOM content can be detected. The spatial distribution maps prepared by inverse distance weighting (IDW) and lognormal kriging (LK) methods show higher PTE contents at the summit and the shoulder of the hillslope and lower contents at the backslope and the footslope zones. The low slope gradients (0-5 degree) and the high contents of the coarse fraction (> 35%) likely protect the soil at the summit and the hillslope’s shoulder from excessive erosion-induced losses. While the reraising PTE contents at the toeslope are likely due to the deposition of fine soil particles (silt and clay). The highest SOM contents at the summit and the toeslope areas, and increased contents of the coarse fraction at the backslope, confirm the effects of soil erosion on the spatial distribution patterns of main soil quality indicators. Overall, the LK outperformed the IDW method in predicting the soil parameters in unsampled areas.
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Yang, Ci-Jian, Li-Wei Yeh, Yeuan-Chang Cheng, Chia-Hung Jen, and Jiun-Chuan Lin. "Badland Erosion and Its Morphometric Features in the Tropical Monsoon Area." Remote Sensing 11, no. 24 (December 17, 2019): 3051. http://dx.doi.org/10.3390/rs11243051.
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Climatically driven processes are important controls on the Earth’s surface and on interactions between the hydrological cycle and erosion in drainage basins. As a result, landscape forms such as hillslope topography can be used as an archive to reconstruct historical climatic conditions. Recent progress in the Structure-from-Motion (SfM) photogrammetric technique allows for the construction of high-resolution, low-cost topography data using remote-controlled unmanned aerial vehicle (UAV) surveys. Here, we present the climatic effects on the hillslope erosion rate that can be obtained from the drainage frequency of hillslopes. We quantify the centimeter-scale accuracy of surveys across 72 badland hillslopes in SE Taiwan, which is a tropical monsoon area with an annual precipitation of over 2 m. Our observations indicate that climatic erosion results in a higher drainage frequency and the number of furrows, instead of drainage density. Additionally, the morphometric slope index (MSI) has a strong positive correlation with erosion and its rate but shows a negative correlation with drainage length and a positive correlation with inclination. This suggests that the erosion pattern is due to gravitational mass wasting instead of hydrological erosion. MSI should always be calculated relying on the normalized slope length and is less applicable to landslide-dominated erosion. We, therefore, suggest that UAV-driven digital elevation models (DEMs) are integrated into erosion mapping to aid in identifying erosion patterns. We highlight the unique opportunity for cross-climate zone comparative studies offered by badland landscapes and differential rainfall patterns, with remote sensing techniques and the morphometric slope index.