scholarly journals Assessing the performance of a plastic optical fibre turbidity sensor for measuring post-fire erosion from plot to catchment scale

SOIL ◽  
2015 ◽  
Vol 1 (2) ◽  
pp. 641-650 ◽  
Author(s):  
J. J. Keizer ◽  
M. A. S. Martins ◽  
S. A. Prats ◽  
L. F. Santos ◽  
D. C. S. Vieira ◽  
...  
Keyword(s):  
Optical Fibre ◽  
Overland Flow ◽  
Sediment Concentration ◽  
First Year ◽  
Power Functions ◽  
Forest Residues ◽  
Catchment Scale ◽  
Light Loss ◽  
Erosion Mitigation ◽  
Study Sites

Abstract. This study is the first comprehensive testing of a novel plastic optical fibre turbidity sensor with runoff samples collected in the field and, more specifically, with a total of 158 streamflow samples and 925 overland flow samples from a recently burnt forest area in north-central Portugal, collected mainly during the first year after the wildfire, as well as with 56 overland flow samples from a nearby long-unburnt study site. Sediment concentrations differed less between overland flow and streamflow samples than between study sites and, at one study site, between plots with and without effective erosion mitigation treatments. Maximum concentrations ranged from 0.91 to 8.19 g L−1 for the micro-plot overland flow samples from the six burnt sites, from 1.74 to 8.99 g L−1 for the slope-scale overland flow samples from these same sites, and amounted to 4.55 g L−1 for the streamflow samples. Power functions provided (reasonably) good fits to the – expected – relationships of increasing normalized light loss with increasing sediment concentrations for the different sample types from individual study sites. The corresponding adjusted R2 values ranged from 0.64 to 0.81 in the case of the micro-plot samples from the six burnt sites, from 0.72 to 0.89 in the case of the slope-scale samples from these same sites, and was 0.85 in the case of the streamflow samples. While the overall performance of the sensor was thus rather satisfactory, the results pointed to the need for scale of site-specific calibrations to maximize the reliability of the predictions of sediment concentration by the POF (plastic optical fibre) sensor. This especially applied to the cases in which sediment concentrations were comparatively low, for example following mulching with forest residues.

scholarly journals Assessing the performance of a plastic optical fiber turbidity sensor for measuring post-fire erosion from plot to catchment scale

2015 ◽  
Vol 2 (1) ◽  
pp. 449-475
Author(s):  
J. J. Keizer ◽  
M. A. S. Martins ◽  
S. A. Prats ◽  
L. F. Santos ◽  
R. Nogueira ◽  
...  
Keyword(s):  
Optical Fiber ◽  
Overland Flow ◽  
Sediment Concentration ◽  
Plastic Optical Fiber ◽  
Power Functions ◽  
Forest Residues ◽  
Catchment Scale ◽  
Light Loss ◽  
Erosion Mitigation ◽  
Study Sites

Abstract. This study is the first comprehensive testing of a novel plastic optical fiber turbidity sensor with runoff samples collected in the field and, more specifically, with a total of 158 streamflow samples and 925 overland flow samples from a recently burnt forest area in north-central Portugal, collected mainly during the first year after the wildfire, as well as with 56 overland flow samples from a nearby long-unburnt study site. Sediment concentrations differed less between overland flow and streamflow samples than between study sites and, at one study site, between plots with and without effective erosion mitigation treatments. Maximum concentrations ranged from 0.91 to 8.19 g L−1 for the micro-plot overland flow samples from the six burnt sites, from 1.74 to 8.99 g L−1 for the slope-scale overland flow samples from these same sites, and amounted to 4.55 g L−1 for the streamflow samples. Power functions provided (reasonably) good fits to the – expected – relationships of increasing normalized light loss with increasing sediment concentrations for the different sample types from individual study sites. The corresponding adjusted R2's ranged from 0.64 to 0.81 in the case of the micro-plot samples from the six burnt sites, from 0.72 to 0.89 in the case of the slope-scale samples from these same sites, and was 0.85 in the case of the streamflow samples. While the overall performance of the sensor was thus rather satisfactory, the results pointed to the need for scale- and/or site-specific calibrations to maximize reliability of the predictions of sediment concentration by the POF sensor. This especially applied to the cases in which sediment concentration were comparatively low, for example following mulching with forest residues.

Post-fire mobilization of metals in a recently burnt area in North-Central Portugal: a contamination risk for waterbodies?

2021 ◽  
Author(s):  
Dalila Serpa ◽  
Ana Machado ◽  
Martha Santos ◽  
Isabel Campos ◽  
Fátima Jesus ◽  
...  
Keyword(s):  
Overland Flow ◽  
Fire Severity ◽  
Hazardous Substances ◽  
Burnt Area ◽  
North Central ◽  
Contamination Risk ◽  
Freshwater Bodies ◽  
Central Portugal ◽  
Study Sites

<p>Wildfires constitute a diffuse source of contamination to aquatic ecosystems. In burnt hillslopes, ash and sediments transported by overland flow are a source of potentially hazardous substances, like metals, posing a risk for downstream water bodies. In the present study, post-fire metal mobilization by overland flow was evaluated in 16 m<sup>2 </sup>bounded plots at a eucalypt stand in Albergaria-a-Velha (Aveiro district, North-Central Portugal) that burnt with moderate severity in September 2019. Overland flow samples were collected on a weekly to bi-weekly basis, depending on the occurrence of rain, during the first 6 months after fire. Aside from overland flow samples collected at slope scale, water and sediment samples were also collected in a fire-affected stream within the Albergaria burned catchment, to assess the contamination risk posed by the fire. Samples were collected at three sites along the stream: one upstream, one within and another downstream from the burnt area, after major rainfall events. The metals analysed in this study included, vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), arsenic (As), cadmium (Cd) and lead (Pb). Results showed that most metals exhibited a peak in exports immediately after the first significant post-fire rainfall event likely due to the wash-off of the ash layer and high sediment losses, but for some elements like Zn and Cu, exports were more or less constant over time. The fire seems to have had a low impact on the water quality of the affected stream, since metal concentrations were similar between the three study sites. The quality of stream sediments, on the other hand, was clearly affected by the fire, especially after the rainy season. As fire severity and frequency is forecasted to increase in the near future due to climate changes, the results of this work reinforce the importance of water managers to define adaptative strategies to effectively protect freshwater bodies.</p>

Dominant drivers of runoff in a slash-and-burn affected catchment in upland Eastern Madagascar

2021 ◽  
Author(s):  
Bob W. Zwartendijk ◽  
H.J. (Ilja) van Meerveld ◽  
Ryan J. Teuling ◽  
Chandra P. Ghimire ◽  
L. Adrian Bruijnzeel
Keyword(s):  
Soil Moisture ◽  
Overland Flow ◽  
Quantitative Information ◽  
Forest Loss ◽  
Runoff Generation ◽  
Catchment Scale ◽  
Valley Bottom ◽  
Antecedent Soil Moisture ◽  
Slash And Burn ◽  
Slash And Burn Agriculture

<p>In many tropical areas slash-and-burn agriculture is an important driver of forest loss. In areas where slash-and-burn agriculture has been practiced for decades, land cover is typically a mosaic of patches of remnant forest, fields under active cultivation, fallows in various stages of regrowth (ranging from young shrub to semi-mature), and degraded fire-climax grasslands. Although runoff generation mechanisms are expected to be different for these different patches, little quantitative information is available in this regard, particularly at the catchment scale and over longer time-scales (i.e., multiple slash-and-burn cycles).</p><p>We re-instrumented a 31 ha catchment in upland Eastern Madagascar, where slash-and-burn agriculture has been practiced for more than 70 years in 2015; it had been monitored between 1963 and 1972 as well<sup>1</sup>. We measured streamflow at two locations and overland flow and soil moisture for four hillside plots (0.05 – 1.93 ha): one plot under repeatedly coppiced and burned <em>Eucalyptus</em> and three plots under young shrub and tree fallows. One of the plots underwent rudimentary terracing in the past. We analysed the rainfall-runoff dynamics for 50 rainfall events (median 12 mm, maximum 71 mm).</p><p>For 60% of the events, the stormflow coefficient (minimum contributing area) was <3%, which is the proportion of valley-bottom wetlands and rice paddies in the catchment. Stable isotope sampling for five storm runoff events indicate a maximum total event-water contribution of 16%. However, instantaneous event-water contributions were as high as 66%. The hillside plot runoff response was dominated by saturation-excess overland flow and showed strong threshold behaviour in terms of the antecedent soil moisture storage in the upper 30 cm of the soil plus the event total rainfall amount (ASI + P). Average threshold values for overland flow occurrence ranged from 87 mm for the coppiced <em>Eucalyptus</em> to 137 mm for the young fallow plots (regardless of terrace presence). Stormflow also increased after an ASI+P-threshold was exceeded (100 mm based on the soil moisture sensors for the <em>Eucalyptus</em> plot and 150 mm for the sensors at the tree fallow plots).</p><p>These results indicate an increased hydrological connectivity between hillslopes and valley bottom under wetter conditions and that stormflow in the study catchment is strongly affected by variations in seasonal rainfall. The results will be used to validate a hydrological model to determine the net effect of concurrent changes in soil infiltrability and vegetation water use associated with forest loss and recovery on stormflow totals and the seasonal flow regime.</p><p><strong><sup>1</sup></strong>Bailly, C., de Coignac, G.B., Malvos, C., Ningre, J.M., and Sarrailh, J.M. (1974). Étude de l'influence du couvert naturel et de ses modifications á Madagascar. Expérimentations en bassins versants élémentaires. Cahiers Scientifiques, 4. Centre Scientifique Forestier Tropical, Nogent-sur-Marne, France, 114 pp.</p>

Advances in Understanding Landscape Influences on Freshwater Habitats and Biological Assemblages

2019 ◽  
Keyword(s):  
Forested Wetlands ◽  
Timber Harvest ◽  
Large Wood ◽  
Catchment Scale ◽  
Southeast Alaska ◽  
Riparian Management ◽  
Freshwater Habitats ◽  
Study Sites ◽  
Landscape Attributes ◽  
Landscape Influences

<i>Abstract.</i>—Currently, much is known about influences of landscape attributes, including timber harvest practices, on large wood dynamics in streams. Comparatively, much less is known about influences of catchment attributes on Southeast Alaska streams, in part because of a historical lack of consistent catchment-scale data available for the region. As in forested regions elsewhere, large wood is an important resource to stream habitats and fishes in Southeast Alaska. Therefore, the purpose of this study was to characterize catchment-scale influences, including various timber harvest practices, on large wood in Southeast Alaska stream sites. We delineated local catchment boundaries for all stream reaches in the region and summarized landscape influences, including natural and harvest-related attributes in local and network catchments. Relative amounts of variation in four large wood habitat variables explained by natural versus harvest practice-related landscape attributes were evaluated to compare different influences on 28 randomly selected study sites. We used those results to predict variation in large wood variables from our sites through use of both natural and harvest practice-related catchment attributes to identify those that may be most influential to large wood. Natural characteristics, including catchment area, deciduous forests, forested wetlands, and catchment slope, all had significant influences on large wood variables, as did various measures of contemporary and historical timber harvest practices. We found that large wood length was positively related to conventional harvest after 1990, suggesting the potential effectiveness of contemporary logging regulations in protecting large wood characteristics. In our study, both natural and timber harvest practice-related attributes had measureable influences on stream habitat, underscoring the importance of considering catchment-scale attributes, including riparian management schemes, for managing Southeast Alaska streams.

scholarly journals Mark-Recapture-Recovery Modeling and Age-Related Survival in Little Penguins (Eudyptula Minor)

The Auk ◽  
2007 ◽  
Vol 124 (3) ◽  
pp. 815-827
Author(s):  
Leesa A. Sidhu ◽  
Edward A. Catchpole ◽  
Peter Dann
Keyword(s):  
First Year ◽  
Model Parameters ◽  
Age Dependence ◽  
Mark Recapture ◽  
Annual Variations ◽  
Southeastern Australia ◽  
Age Related ◽  
Second Year ◽  
Study Sites ◽  
First Year Of Life

Abstract We analyzed yearly mark-recapture-recovery information collected over a 36-year period for the Little Penguins (Eudyptula minor) of Phillip Island in southeastern Australia. We show that it is feasible to model age-dependence for the survival, recapture, and recovery probabilities simultaneously, and that such a modeling scheme yields biologically realistic age structures for the model parameters. We provide illustrations of potentially erroneous results that may arise when researchers fail (1) to consider simultaneous age-dependence or (2) to detect annual variations that may mask age-dependence. From 1968 to 2004, 23,686 chicks were flipper-banded; 2,979 birds were encountered after fledging, and 1,347 were ultimately recovered dead. We found low survival of 17% in the first year of life, increasing to 71% in the second year of life, 78% in the third year, and 83% thereafter, and declining gradually after nine years of age. A population model allowing for immigration of birds from areas surrounding the study sites fits the observed stable population in the study sites. Modelado de Marca-Recaptura-Recuperación y Supervivencia Relacionada con la Edad en Eudyptula minor

Scale Effects of Sediment-Related Transport of Phosphorus

1993 ◽  
Vol 28 (3-5) ◽  
pp. 473-481 ◽  
Author(s):  
S. M. Bolton ◽  
T. J. Ward
Keyword(s):  
Total Phosphorus ◽  
Overland Flow ◽  
Sediment Load ◽  
Scale Effects ◽  
Sediment Concentration ◽  
Rainfall Simulation ◽  
Small Rivers ◽  
Phosphorus Transport ◽  
Simulation Experiments ◽  
Stream Type

Sediment and nutrient data from USGS gauged stream sites in New Mexico and from rainfall simulation experiments were compiled and analyzed. Above a suspended sediment concentration of about 500 mg/l, associated concentrations of total phosphorus are highest in overland flow and then progressively decrease from agricultural drains to ephemeral washes to undammed rivers. Within a stream type, sediment-related concentrations of total phosphorus typically differed between larger and smaller basins. Small rivers had higher phosphorus transport per unit of sediment load than larger rivers. Small and medium sized washes had different relationships between phosphorus and sediment than did large and very large washes.

Soil erosion processes. I. The relative importance of rainfall detachment and dunoff entrainment

Soil Research ◽  
1991 ◽  
Vol 29 (5) ◽  
pp. 671 ◽  
Author(s):  
APB Proffitt ◽  
CW Rose
Keyword(s):  
Soil Erosion ◽  
Overland Flow ◽  
Water Flux ◽  
Equilibrium Concentration ◽  
Sediment Concentration ◽  
Soil Types ◽  
Relative Importance ◽  
Runoff Water ◽  
Erosion Processes ◽  
Volumetric Flux

Experiments carried out in a simulated-rainfall tilting-flume facility are reported in which sediment concentrations (c) in runoff water resulting from overland flow only, or from a combination of rainfall and overland flow, were measured under controlled conditions using a series of slopes (0.1, 05, 1, 3 and 5%). The mixture of rainfall (of rate 100 mm h-1) and runon of water at the top of the flume were arranged to provide a constant volumetric flux (1.0x10-3 m3 m-l s-1) at exit from the 5.8 m long flume. Two contrasting soil types were studied: a cracking clay (black earth or vertisol), and a slightly dispersive sandy clay loam (solonchak or aridisol). Two major processes which can contribute to soil erosion under rainfall are rainfall detachment and runoff entrainment. For both soil types, c was generally highest for the steepest slope and decreased with slope. For constant rainfall and/or runoff conditions, c generally decreased with time until an equilibrium concentration was reached. At this equilibrium, the relative importance of rainfall detachment and entrainment in terms of soil loss was dependent on soil type and streampower which incorporates effects of slope and water flux. For streampowers <0.1 W m-2 for the black earth, and <0.3 W m-2 for the solonchak, the greatest contribution to c was by rainfall detachment, whilst at greater streampowers entrainment was the dominant contributor to c. At any streampower, the contribution by rainfall detachment was greater for the weakly structured solonchak than for the well aggregated black earth. At lower strearnpowers, the interaction between erosion processes was found to give higher c than the sum of both sediment concentrations resulting from the separately occurring processes. At streampowers greater than approximately 0.5 W m-2, rainfall reduced eroded sediment concentration by suppressing rill development. The findings in this study suggest that both runoff entrainment and rainfall detachment can contribute to sediment concentration from 'interrill' areas.

scholarly journals Impacts of wildfire and post-fire land management on hydrological and sediment processes in a humid Mediterranean headwater catchment

2021 ◽  
Author(s):  
Joao Pedro Nunes ◽  
Léonard Bernard-Jannin ◽  
María Luz Rodríguez-Blanco ◽  
Anne-Karine Boulet ◽  
Juliana Marisa Santos ◽  
...  
Keyword(s):  
Sediment Yield ◽  
Agricultural Landscape ◽  
Sediment Concentration ◽  
Dominant Factor ◽  
Severe Drought ◽  
Negative Consequences ◽  
Catchment Scale ◽  
Burnt Area ◽  
Rainfall Events ◽  
The North

&lt;p&gt;The extensive afforestation of the Mediterranean rim of Europe in recent decades has increased the number of wildfire disturbances on hydrological and sediment processes, but the impacts on headwater catchments is still poorly understood, especially when compared with the previous agricultural landscape. This work monitored an agroforestry catchment in the north-western Iberian Peninsula, with plantation forests mixed with traditional agriculture using soil conservation practices, for one year before the fire and for three years afterwards, during which period the burnt area was plowed and reforested. During this period, continuous data was collected for meteorology, streamflow and sediment concentration at the outlet, erosion features were mapped and measured after major rainfall events, and channel sediment dynamics were monitored downstream from the agricultural and the burnt forest area. Data from 202 rainfall events with over 10 mm was analysed in detail.&lt;/p&gt;&lt;p&gt;Results show that the fire led to a notable impact on sediment processes during the first two post-fire years, but not on streamflow processes; this despite the small size of the burnt area (10% of the catchment) and the occurrence of a severe drought in the first year after the fire. During this period, soil loss at the burnt forest slopes was much larger than that at most traditionally managed fields, and, ultimately, led to sediment exhaustion. At the catchment scale, storm characteristics were the dominant factor behind streamflow and sediment yield both before and after the fire. However, the data indicated a shift from detachment-limited sediment yield before the fire, to transport-limited sediment yield afterwards, with important increases in streamflow sediment concentration. This indicates that even small fires can temporarily change sediment processes in agroforestry catchments, with potential negative consequences for downstream water quality.&lt;/p&gt;

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