scholarly journals Detection of seasonal erosion processes at the scale of an elementary black marl gully from time series of Hi-Resolution DEMs

2015 ◽  
Vol 3 (4) ◽  
pp. 1555-1586 ◽  
Author(s):  
J. Bechet ◽  
J. Duc ◽  
A. Loye ◽  
M. Jaboyedoff ◽  
N. Mathys ◽  
...  
Keyword(s):  
Time Series ◽  
Seasonal Pattern ◽  
Laser Scanner ◽  
Sediment Budget ◽  
Research Station ◽  
Transport Capacity ◽  
Runoff Generation ◽  
Sediment Production ◽  
Erosion Processes ◽  
Surface Changes

Abstract. The Roubine catchment located in the experimental research station of Draix-Bléone (south French Alps) is situated in Callovo-Oxfordian black marls, a lithology particularly prone to weathering processes. Since 30 years, this small watershed (0.13 ha) has been monitored for analysing hillslope erosion processes at the scale of elementary gullies. Since 2007, a monitoring of surface changes has been performed by comparing of high-resolution digital elevation models (HR-DEMs) produced from Terrestrial Laser Scanner (TLS). The objectives are (1) to detect and (2) to quantify the sediment production and the evolution of the gully morphology in terms of sediment availability/transport capacity vs. rainfall and runoff generation. Time series of TLS observations have been acquired periodically based on the seasonal runoff activity with a very high point cloud density ensuring a resolution of the DEM at the centimetre scale. The topographic changes over a time span of 4 years are analysed. Quantitative analyses of the seasonal erosion activity and of the sediment fluxes contributing to the recharge of tributary gullies and rills are presented. According to the transport capacity generated by runoff, loose regolith soil sources are eroded at different periods of the year. These are forming transient deposits in the main reach when routed downstream, evolving from a transport-limited to a supply-limited regime through the year. The monitoring allows a better understanding of the seasonal pattern of erosion processes for black marls badland-type slopes and illustrates the mode of sediment production and the temporal storage/entrainment in similar slopes. The observed surface changes caused by erosion (ablation/deposition) are quantified for the complete TLS time-series, and sediment budget maps are presented for each season. Comparisons of the TLS sediment budget map with the in situ sediment monitoring (limnigraph and sedigraph) in the stream are discussed. Intense and long duration rainfall events are the triggering factor of the major erosive events.

scholarly journals Detection of seasonal cycles of erosion processes in a black marl gully from a time series of high-resolution digital elevation models (DEMs)

2016 ◽  
Vol 4 (4) ◽  
pp. 781-798 ◽  
Author(s):  
Jacques Bechet ◽  
Julien Duc ◽  
Alexandre Loye ◽  
Michel Jaboyedoff ◽  
Nicolle Mathys ◽  
...  
Keyword(s):  
Time Series ◽  
High Resolution ◽  
Digital Elevation Models ◽  
Slope Angle ◽  
Laser Scanner ◽  
Research Station ◽  
Runoff Generation ◽  
Erosion Processes ◽  
Antecedent Precipitation ◽  
Digital Elevation

Abstract. The Roubine catchment located in the experimental research station of Draix-Bléone (south French Alps) is situated in Callovo-Oxfordian black marls, a lithology particularly prone to erosion and weathering processes. For 30 years, this small watershed (0.13 ha) has been monitored for analysing hillslope processes on the scale of elementary gullies. Since 2007, surface changes have been monitored by comparing high-resolution digital elevation models (HRDEMs) produced from terrestrial laser scanner (TLS). The objectives are (1) to detect and (2) to quantify the sediment production and the evolution of the gully morphology in terms of sediment availability/transport capacity vs. rainfall and runoff generation. Time series of TLS observations have been acquired periodically based on the seasonal runoff activity with a very high point cloud density ensuring a resolution of the digital elevation model (DEM) on the centimetre scale. The topographic changes over a time span of 2 years are analysed. Quantitative analyses of the seasonal erosion activity and of the sediment fluxes show and confirm that during winter, loose regolith is created by mechanical weathering, and it is eroded and accumulates in the rills and gullies. Because of limited rainfall intensity in spring, part of the material is transported in the main gullies, which are assumed to be a transport-limited erosion system. In the late spring and summer the rainfall intensities increase, allowing the regolith, weathered and accumulated in the gullies and rills during the earlier seasons, to be washed out. Later in the year the catchment acts as a sediment-limited system because no more loose regolith is available. One interesting result is the fact that in the gullies the erosion–deposition processes are more active around the slope angle value of 35°, which probably indicates a behaviour close to dry granular material. It is also observed that there exist thresholds for the rainfall events that are able to trigger significant erosion; they are above 9 mm rainfall or of an intensity of more than 1 mm min−1, values which can vary if antecedent precipitation is significant within the last 5 days.This study improves knowledge of the spatial distribution of erosion seasonality in badlands and demonstrates the potential of careful 3-D high-resolution topography using TLS to improve the understanding of erosive processes.

scholarly journals Hydrological processes and their seasonal controls in a small Mediterranean mountain catchment in the Pyrenees

2002 ◽  
Vol 6 (3) ◽  
pp. 527-537 ◽  
Author(s):  
F. Gallart ◽  
P. Llorens ◽  
J. Latron ◽  
D. Regüés
Keyword(s):  
Soil Moisture ◽  
Vegetation Cover ◽  
Seasonal Pattern ◽  
Atmospheric Conditions ◽  
Runoff Generation ◽  
Spatial Organisation ◽  
Mountain Area ◽  
Physical Weathering ◽  
Erosion Processes ◽  
Marked Deficit

Abstract. The Vallcebre catchments are located in a middle mountain area of the Pyrenean ranges, built up by sedimentary rocks and loamy soils. The vegetation cover is pastures and forests of Pinus sylvestris, mostly occupying former agricultural terraces. Some relatively small, heavily eroded landscapes (badlands) occur in the catchments, playing a relevant hydrological and geomorphic role. Annual precipitation is 924 mm and potential (reference) evapotranspiration is about 700 mm. Rainfall interception in forests represents about 24% of precipitation; interception rates were similar throughout the seasons because of a compensation between rainfall intensities and atmospheric conditions. Soil moisture showed a temporal pattern characterised by the occurrence of marked deficit periods in summer and also, but less pronounced, in winter. During most of the year, subsurface flows on hillslopes drove the spatial organisation of soil moisture and the occurrence of saturated areas. Nevertheless, this spatial organisation was also controlled by the patterns of vegetation cover. During dry periods, subsurface flow ceased, saturated areas disappeared and the spatial patterns of soil moisture changed. Stream flow from these catchments was dominated by storm flow, and the runoff generating mechanisms showed a clear seasonal pattern, controlled mainly by the soil moisture and the extent of saturated areas. During the dry periods, runoff was produced only on impervious areas and badlands. At the end of the dry periods, some large rainfall events generated significant runoff because of the perched saturation of the shallow soil horizons. Thereafter, runoff generation was dominated by the role of saturated areas. Stream waters in catchments with badlands had very high suspended sediment concentrations. The seasonal pattern of erosion processes in badlands was characterised by physical weathering during winter, regolith breakdown and vigorous hillslope erosion during spring and summer, and efficient transport of sediments in autumn.

scholarly journals Modelling Effects of Rainfall Patterns on Runoff Generation and Soil Erosion Processes on Slopes

Water ◽  
2019 ◽  
Vol 11 (11) ◽  
pp. 2221
Author(s):  
Qihua Ran ◽  
Feng Wang ◽  
Jihui Gao
Keyword(s):  
Soil Erosion ◽  
Rainfall Intensity ◽  
Temporal Patterns ◽  
Runoff Generation ◽  
Slope Length ◽  
Erosion Processes ◽  
Total Runoff ◽  
Wide Range ◽  
Critical Slope ◽  
Rainfall Patterns

Rainfall patterns and landform characteristics are controlling factors in runoff and soil erosion processes. At a hillslope scale, there is still a lack of understanding of how rainfall temporal patterns affect these processes, especially on slopes with a wide range of gradients and length scales. Using a physically-based distributed hydrological model (InHM), these processes under different rainfall temporal patterns were simulated to illustrate this issue. Five rainfall patterns (constant, increasing, decreasing, rising-falling and falling-rising) were applied to slopes, whose gradients range from 5° to 40° and projective slope lengths range from 25 m to 200 m. The rising-falling rainfall generally had the largest total runoff and soil erosion amount; while the constant rainfall had the lowest ones when the projective slope length was less than 100 m. The critical slope of total runoff was 15°, which was independent of rainfall pattern and slope length. However, the critical slope of soil erosion amount decreased from 35° to 25° with increasing projective slope length. The increasing rainfall had the highest peak discharge and erosion rate just at the end of the peak rainfall intensity. The peak value discharges and erosion rates of decreasing and rising-falling rainfalls were several minutes later than the peak rainfall intensity.

scholarly journals Holocene Sediment Production in Lillooet River Basin, British Colombia: A Sediment Budget Approach

2007 ◽  
Vol 45 (1) ◽  
pp. 45-57 ◽  
Author(s):  
Peter Jordan ◽  
Olav Slaymaker
Keyword(s):  
Sediment Yield ◽  
Debris Flows ◽  
Sediment Budget ◽  
Sediment Supply ◽  
Volcanic Complex ◽  
Minor Importance ◽  
The Holocene ◽  
Sediment Production ◽  
Clastic Sediment ◽  
Holocene Sediment

ABSTRACTA sediment budget approach is used to investigate the sources, storage, and yield of clastic sediment in Lillooet River watershed, in the southern Coast Mountains. The 3150 km2basin is heavily glacierised, and includes a Quaternary volcanic complex which has been active in the Holocene. The sediment yield has been determined from the rate of advance of the delta at the basin outlet. The floodplain of the main river valley is aggrading as the delta advances, and probably has been through most of the Holocene. Major sediment sources in the basin include glaciers and Neoglacial deposits, debris flows, and landslides in the Quaternary volcanic complex. Soil and bedrock creep, bank erosion of Pleistocene glacial deposits, and sediment from logging and agriculture are probably of minor importance. Estimates of sediment production from these sources explain only about half the observed clastic sediment yield plus the rate of valley aggradation. The unexplained sediment production may be associated with paraglacial sediments exposed by glacial retreat from the nineteenth century Neoglacial maximum; alternatively the frequency of occurrence of intermediate scale debris flows and landslides has been seriously underestimated. Sediment supply is highly episodic over time scales of centuries to thousands of years. Major factors in the temporal pattern of Holocene sediment supply are periods of volcanism, large landslides, the retreat of glaciers from the Neoglacial maximum, and recent river engineering works.

scholarly journals The association between seasonal influenza-like illness cases and foetal death: a time series analysis

2018 ◽  
Vol 147 ◽  
Author(s):  
I. S. Rasmussen ◽  
L. H. Mortensen ◽  
T. G. Krause ◽  
A-M. Nybo Andersen
Keyword(s):  
Time Series ◽  
Time Series Analysis ◽  
Spontaneous Abortion ◽  
Seasonal Pattern ◽  
Influenza Virus Infection ◽  
Temporal Association ◽  
Spontaneous Abortions ◽  
Foetal Death ◽  
Influenza Like Illness ◽  
Series Analysis

AbstractIt has been reported that foetal death follows a seasonal pattern. Influenza virus infection has been postulated as one possible contributor to this seasonal variation. This ecological study explored the temporal association between the influenza activity and the frequency of foetal death. Time series analysis was conducted using weekly influenza-like illness consultation proportions from the Danish sentinel surveillance system and weekly proportions of spontaneous abortions and stillbirths from hospital registers from 1994 to 2009. The association was examined in an autoregressive (AR) integrated (I) moving average (MA) model and subsequently analysed with cross-correlation functions. Our findings confirmed the well-known seasonality in influenza, but also seasonality in spontaneous abortion. No clear pattern of seasonality was found for stillbirths, although the analysis exposed dependency between observations. One final AR integrated MA model was identified for the influenza-like illness (ILI) series. We found no statistically significant relationship between weekly influenza-like illness consultation proportions and weekly spontaneous abortion proportions (five lags: P = 0.52; 11 lags: P = 0.91) or weekly stillbirths (five lags: P = 0.93; 11 lags: P = 0.40). Exposure to circulating influenza during pregnancy was not associated with rates of spontaneous abortions or stillbirths. Seasonal variations in spontaneous abortion were confirmed and this phenomenon needs further investigation.

Deciphering the pedogenic and sedimentary archives and long-term landform dynamics to reconstruct complex landscape evolution within a lowland gully catchment over the Holocene

2020 ◽  
Author(s):  
Vladimir Belyaev ◽  
Ilya Shorkunov ◽  
Ekaterina Garankina ◽  
Evgeniy Konstantinov ◽  
Alexey Rusakov ◽  
...  
Keyword(s):  
Land Use ◽  
Sediment Budget ◽  
Historical Period ◽  
Landscape Changes ◽  
Buried Soils ◽  
Fluvial Systems ◽  
Small Catchment ◽  
The Holocene ◽  
Erosion Processes ◽  
Duration Magnitude

<p>For the landscape and climatic conditions of the Eastern European Plain fluvial processes are considered to be the leading geomorphic force during the Holocene. Different hierarchical levels of fluvial landforms from individual hillslopes through gully network to river systems are characterized by various degrees of resilience and relaxation times in response to external impacts of different duration, magnitude and frequency. These characteristics of fluvial systems largely depend on their spatial scale, effective discharges and morphodynamics. Particularly important is understanding of hydrological and geomorphic connectivity at various scales, rates and patterns of hydrological and sedimentary signals propagation and variable sources-pathways-sinks structure of geomorphic cascades under changing climate and land use conditions. It is generally accepted that landscapes of the European plains have experienced alternating periods of relative stability and significant shifts in climate, soil and geomorphological development over the Holocene. A number of studies has been devoted to the Holocene soil and gully erosion processes in Russia and other European countries. Available sources of information on the past erosion and deposition cycles in small catchments include truncated soils, completely or partially infilled gullies, colluvial deposits and lake or reservoir sediments. The highest temporal resolution may be derived from lacustrine sediments. Such geoarchives are characterized by continuous records and often store signals of landscape changes, surface dynamics and vegetation variability (including land use patterns for the historical period) in decadal to seasonal resolution. However, because of the problem of variable fluvial connectivity and associated limited sediment delivery in cascade fluvial systems, quantification of small catchment sediment budget can be a very difficult task requiring thorough consideration of colluvial deposits storages and remobilization.<br>This study presents the new results of multidisciplinary reconstruction of interaction of geomorphic and soil-forming processes, landscape changes and stabilization phases during the Holocene for the Puzbol gully catchment (about 7.95 km2) draining the Borisoglebsk Upland northeastern slope towards the Nero Lake (Yaroslavl Region, central European Russia). The study is based on complex geomorphic, lithostratigraphic and soil surveys by means of detailed field description, photo-fixation, sampling and laboratory analysis of materials from >40 natural or artificial exposures, cores and soil sections. Observed absence of the early Holocene deposits can be explained by generally negative sediment budget of the catchment. It was more likely caused by high-magnitude low-frequency runoff events associated with climatic extremes rather than by dominance of continuous moderate erosion. A series of the middle Holocene 14C dates obtained by analyzing total organic carbon from humic layers of buried soils, lake gyttja and peats provides strong evidence of the synchronous phase of landscape stabilization in both upper and lower parts of the Puzhbol catchment accompanied by active infilling of smaller tributary gullies along its banks at middle part. The upper part of the Puzhbol Gully fan sediment shows clear evidence of synchronous accumulation of agrogenic colluvium and gully alluvium since XIIth Century on top of the Nero Lake terrace deposits.<br>The study is supported by the Russian Science Foundation (Project No. 19-77-10061).</p>

scholarly journals Atmospheric black carbon and sulfate concentrations in Northeast Greenland

2015 ◽  
Vol 15 (16) ◽  
pp. 9681-9692 ◽  
Author(s):  
A. Massling ◽  
I. E. Nielsen ◽  
D. Kristensen ◽  
J. H. Christensen ◽  
L. L. Sørensen ◽  
...  
Keyword(s):  
Black Carbon ◽  
Correlation Coefficient ◽  
Seasonal Pattern ◽  
Maximum Level ◽  
High Arctic ◽  
The Arctic ◽  
Research Station ◽  
Summer Period ◽  
Transport Pathways ◽  
Inorganic Matter

Abstract. Measurements of equivalent black carbon (EBC) in aerosols at the high Arctic field site Villum Research Station (VRS) at Station Nord in North Greenland showed a seasonal variation in EBC concentrations with a maximum in winter and spring at ground level. Average measured concentrations were about 0.067 ± 0.071 for the winter and 0.011 ± 0.009 for the summer period. These data were obtained using a multi-angle absorption photometer (MAAP). A similar seasonal pattern was found for sulfate concentrations with a maximum level during winter and spring analyzed by ion chromatography. Here, measured average concentrations were about 0.485 ± 0.397 for the winter and 0.112 ± 0.072 for the summer period. A correlation between EBC and sulfate concentrations was observed over the years 2011 to 2013 stating a correlation coefficient of R2 = 0.72. This finding gives the hint that most likely transport of primary emitted BC particles to the Arctic was accompanied by aging of the aerosols through condensational processes. BC and sulfate are known to have only partly similar sources with respect to their transport pathways when reaching the high Arctic. Aging processes may have led to the formation of secondary inorganic matter and further transport of BC particles as cloud processing and further washout of particles is less likely based on the typically observed transport patterns of air masses arriving at VRS. Additionally, concentrations of EC (elemental carbon) based on a thermo-optical method were determined and compared to EBC measurements. EBC measurements were generally higher, but a correlation between EC and EBC resulted in a correlation coefficient of R2 = 0.64. Model estimates of the climate forcing due to BC in the Arctic are based on contributions of long-range transported BC during spring and summer. The measured concentrations were here compared with model results obtained by the Danish Eulerian Hemispheric Model, DEHM. Good agreement between measured and modeled concentrations of both EBC/BC and sulfate was observed. Also, the correlation between BC and sulfate concentrations was confirmed based on the model results observed over the years 2011 to 2013 stating a correlation coefficient of R2 = 0.74. The dominant source is found to be combustion of fossil fuel with biomass burning as a minor, albeit significant source.

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