Importance of DTM accuracy, precision and acquisition technique for estimating contributing areas of post-fire erosion at the slope and catchment scale

Wildfires are a frequent phenomenon in Portugal, affecting over 300.000 ha in dry years like 2003 and 2005. Directly and/or indirectly, wildfires can strongly enhance the hydrological response and associated sediment losses and, thereby, negatively affect land-use sustainability as well as ecosystem functioning of downstream aquatic habitats. Therefore, the EROSFIRE projects aim at developing a GIS-tool for predicting soil erosion hazard following wildfire and post-fire land management practices. Assessment and modeling of runoff and soil erosion rates critically depends on accurate estimates of the contributing areas. In the case of catchments as well as unbounded erosion plots (arguably, the only practical solution for slope-scale measurements), delineation of contributing area requires a Digital Terrain Model (DTM) with an adequate resolution and accuracy. The DTM that was available for the Colmeal study area (Goís municipality, central Portugal) was that of the 1:25.000 topographic map produced by the Military Geographic Institute. Since this study area involves a rather small experimental catchment of roughly 10 ha and relatively short study slopes of less than 100 m long, two different data acquisition techniques were used to produce high-resolution and high-accuracy DTM. One is aerial photogrammetry, whilst the other is terrestrial laser scanning. To produce a DTM by photogrammetric means, a dedicated digital aerial photography mission was carried out. The images had a pixel size of 10 cm. Manual measurements permitted to measure breaklines and were complemented by automatic measurements. In this way, a DTM in a TIN format was produced. This was further converted to grid format using the ArcGIS software system. Signalized control points allowed obtaining the DTM in the same global reference system as that employed for terrestrial laser scanning. The terrestrial laser scanning was done using a Riegl LMS Z360I, stationed in 8 points within the area to provide a complete coverage. The resulting dense cloud of points was filtered – by the company carrying out the scanning mission - to remove the non-terrain points (in particular vegetation). Several grids of different sizes were produced (0.10 x 0.10, 0.20 x 0.20, 0.50 x 0.50, 1 x 1 and 2 x 2 m2). The proposed work will compare and analyze estimates of contribution areas that were obtained with the two above-mentioned data acquisition techniques and for different spatial resolutions. This will be done for selected slope-scale sediment fences as well as for the outlet of the experimental catchment. In addition, different algorithms available in ArcGIS for TIN-to-grid conversion will be compared, since preliminary results have suggested that these procedures produce markedly different results

Effect of the Resolution and Accuracy of DTM produced with Aerial Photogrammetry and Terrestrial Laser Scanning on Slope- and Catchment-scale Erosion Assessment in a Recently Burnt Forest Area: a Case Study

Wildfires are a common phenomenon in Portugal, affecting on average 100.000 ha of rural areas per year and up to 400.000 ha in dramatic years like 2003 and 2005. Wildfires can strongly enhance the hydrological response and associated sediment losses in recently burnt forest catchments and, thereby, negatively affect land-use sustain- ability of the affected terrains as well as ecosystem functioning of downstream aquatic habitats. Therefore, the EROSFIRE-I and –II projects aim at developing a GIS-tool for predicting soil erosion hazard following wildfire and, ultimately, for assessing the implications of alternative post-fire land management practices. Assessment of runoff and soil erosion rates critically depends on accurate estimates of the corresponding runoff areas. In the case of catchments as well as unbounded erosion plots (arguably, the only practical solution for slope-scale measurements), delineation of runoff area requires a Digital Terrain Model (DTM) with an adequate resolution and accuracy. The DTM that was available for the Colmeal study area, localized in the mountain range of Lousã, in the central part of Portugal, of EROSFIRE-II project is that of the 1:25.000 topographic map produced by the Military Geographic Institute. Since the Colmeal area involves a rather small experimental catchment of roughly 10 ha and relatively short study slopes of less than 100 m long, two different data acquisition techniques were used to produce high-resolution and high-accuracy DTM. One of the data acquisition techniques is aerial photogrammetry whilst the other is terrestrial laser scanning. In order to produce a DTM by photogrammetric means, a dedicated digital aerial photography mission was carried out. The images have a pixel size of 10 cm. Manual measurements permitted to measure breaklines and were complemented by automatic measurements. In this way, a DTM in a TIN format was produced. This was further converted to grid format using the ArcGIS software system. Signalized control points allowed obtaining the DTM in the same global reference system as that employed for terrestrial laser scanning. The terrestrial laser scanning was done using a Riegl LMS Z360I, stationed in 8 points within the area to provide a complete coverage. The resulting dense cloud of points was filtered – by the company carrying out the scanning mission - to remove the non-terrain points (in particular vegetation). Several grids of different sizes were produced (0.10 x 0.10, 0.20 x 0.20, 0.50 x 0.50, 1 x 1 and 2 x 2 m2). This work will study the effect on runoff and erosion rates at the slope- and catchment-scale of DTM with differ- ent resolution, but produced with data collected with the same acquisition technique, and of DTM with the same resolution, but produced with data collected with the two different acquisition techniques. The study is being carried out in ArcGIS using DTM in a grid format. Preliminary results suggest that the conver- sion of TIN-to-grid in ArcGIS produces results that depend on the procedure being applied. Therefore, the different algorithms available at ArcGIS for TIN-to-grid conversion are currently being tested, using an artificially produced DTM. This testing includes various interpolation techniques for grid generation, and will be extended to different algorithms for computation of drainage flow direction

References

www.biogeosciences-discuss.net/11/8373/2014/ doi:10.5194/bgd-11-8373-2014 © Author(s) 2014. CC Attribution 3.0 License. This discussion paper is/has been under review for the journal Biogeosciences (BG). Please refer to the corresponding final paper in BG if available. Wind-induced upwelling in the Kerguele

Mothers and Infants in the Prehistoric Santa Clara Valley: What Stable Isotopes Tell Us about Ancestral Ohlone Weaning Practices

Breast-feeding and weaning are a part of childhood in all human populations, but the exact timing of these milestones varies between groups. As infants incorporate the nutrients from breast milk into their growing bones, chemical evidence is captured in the form of higher stable nitrogen (δ15N) isotope values. This study interprets δ15N values in the bone collagen of children (n = 24) buried at the Yukisma Mound (CA-SCL-38), in Santa Clara County, California. Radiocarbon dates for this site span 2200-250 B.P., but primarily fall during the Late period (740-230 B.P.). In the one probable mother-infant pair available for study, a 2.9 per mil enrichment of δ15N values was observed, consistent with the expected trophic level enrichment of breast-feeding infants. δ15N values of children under seven years old suggest the introduction of weaning foods between 1.5 and 2 years of age, and cessation of breast-feeding by 3 to 3.5 years of age. These results differ from the practices reported in the ethnohistoric literature. This paper includes photos of human remains, taken during excavation at CA-SCL-38 by Ohlone Family Consulting Services, the CRM arm of the Muwekma Ohlone Tribe (which also served as the Most Likely Descendant tribal group for this project). The images were provided to the authors by the tribe, and specific permission was granted to include them in this publication

Survey on Plum pox virus in Norway

In 1998 Plum pox virus (PPV) was detected for the first time in Norway. Virus-like symptoms were observed on several trees in a collection of plum cultivars at Njøs Research Station in the Sogn og Fjordane County in West Norway. The Norwegian Food Safety Authority and the Norwegian Crop Research Institute immediately started surveying other variety collections around the country, nuclear stock material and orchards in all important plum-growing areas. Since 1998 we have surveyed the main part of the commercial plum orchards in Norway. About 75 000 individual trees have been tested. About 1 % of the trees have been found infected by PPV. Only the PPV-D strain has been found. It is suspected that the main infection source was infected plums or apricots imported to Njøs around 1970 or earlier. In most plum orchards in Norway, the spread of PPV by aphids is relatively slow. Therefore, we expect to be able to eradicate PPV from commercial plum orchards in the near future. The eradication work is continuing.Keywords: Plum pox virus, surve

Biodegradation of mono-, di- and trifluoroacetate by microbial cultures with different origins

This work focused on the biodegradation of three structurally related fluoroacetates (FAs), mono- (MFA), di- (DFA) and trifluoroacetate (TFA), using as microbial inocula samples collected from a site with a long history of industrial contamination and activated sludge obtained from a municipal wastewater treatment plant. Biodegradation experiments were carried out under different modes of substrate supplementation, which included (i) FAs fed as sole carbon sources; (ii) FAs (only for DFA and TFA) fed in co-metabolism with sodium acetate; and (iii) mixtures of MFA with DFA or TFA. Biodegradation of the target compounds was assessed through fluoride ion release. Defluorination was obtained in the cultures fed with MFA, while DFA and TFA were recalcitrant in all tested conditions. When present in mixture, DFA was shown to inhibit biodegradation of MFA, while TFA had no effect. A total of 13 bacterial isolates obtained from MFA degrading cultures were found to degrade 20mgL-1 of this compound, as single strains, when supplemented as a sole carbon source. Sequencing of the 16S rRNA gene indicated that among these degrading bacteria only Delftia acidovorans had been previously reported to be able to degrade MFA. This work shows that, despite their similar chemical structures, biodegradation of the three tested FAs is very distinct and draws attention to the unknown impacts that the accumulation of DFA and TFA may have in the environment as a result of their high recalcitrance.info:eu-repo/semantics/publishedVersio

A cidade do Rio de Janeiro e as chuvas de março/93: (des) organização urbana e inundações

The mountainous arcas of Rio de Janeiro act as water divergent areas, converging to the valley-flats. In the last decades, urban expansion has advanced fastly to still forested upward lands, mainly on the north slope of the Tijuca Massif, where numerous "favelas" are located. Changes in the slopes and valley-flats hydrologic behaviour generate major runoff budgets. So major flows-sediment's and flows-garbage's concentrations into the drained valley-axis, naturally or artificially (channels and pluvial tubulations), spreading inundations on the respectives street of the districts's major density population . The Joana, Maracanã and Comprido basins studied in detail show that the mud-flows and garbage-flows concentrate on the knick slopes and the floods on the valley-axis. These events are aggravated by the cumulated rainstorms due to the inadequacy of the urban pluvial drainage system.Os maciços montanhosos da cidade do Rio de Janeiro funcionam como centros dispersores de águas pluviais, as quais, naturalmente, convergem para os fundos de vales. Nas últimas décadas, a expansão urbana tem avançado rapidamente em direção às áreas mais elevadas da cidade, ainda florestadas, principalmente na vertente norte do Maciço da Tijuca, onde se espraiam numerosas favelas. Mudanças no comportamento hidrológico nas encostas e fundos de vales geraram uma maior produção de escoamento superficial. Em decorrência, uma maior concentração de fluxos de sedimentos e lixos dentro dos eixos de vales drenados, naturalmente ou artificialmente (canais e tubulações pluviais), propagando inundações nas respectivas ruas dos bairros de maior densidade populacional. Um estudo detalhado nas bacias dos rios Joana, Maracanã e Comprido mostra que os fluxos de lama e lixos concentram-se nas zonas de ruptura de declive, e as enchentes nos eixos de vales. Estes eventos são agravados pelas chuvas acumuladas devido a insuficiência do sistema de drenagem pluvial urbano

Construction and validation of a low-cost system for indoor air quality measurements in livestock facilities

In recent years, there has been an increase in demand for food of ani-mal origin. The number of intensive production systems such as pig and poultry farming has been increasing more and more and exerting great impacts on the environment, due to a large amount of particulate material and gaseous pollutants that are generated within these facilities. Thus, low-cost devices emerge as a cheap alternative that provides farmers with information on indoor air quality in its facilities. However, it is important that these devices make precise and accu-rate measurements, providing reliable concentration readings. Therefore, the ob-jective of this study is the construction and validation of a low-cost system capa-ble of measuring, storing and sending, via the mobile network, the concentrations of hydrogen sulfide, ammonia, carbon dioxide, PM2.5, PM10, temperature, and relative humidity. Preliminary inter-comparison tests showed that the built sys-tem had a reliable behavior in relation to all variables, even though the CO2 sen-sor was the one with the highest determination coefficient. The built device is able to provide continuous monitoring of atmospheric pollutants concentrations, at low cost and with simple handling.This study was supported by the Fundação para a Ciência e Tecnologia (FCT, Portugal) and FEDER under the PT2020 Program through financial support to CIMO (UID/AGR/00690/2013) and by the bilateral project established between the Polytechnic Institute of Bragança (Portugal) and the Federal University of Technology – Paraná (Brazil).info:eu-repo/semantics/publishedVersio