Climate change is expected to affect the occurrence of heavy rainfall. We analyzed trends of heavy rainfall days for the last decades in Germany. For all available stations with daily data, days ...exceeding daily thresholds (10, 20, 30 mm) were counted annually. The Mann–Kendall trend test was applied to overlapping periods of 30 years (1951–2019). This period was extended to 1901 for 111 stations. The stations were aggregated by natural regions to assess regional patterns. Impacts of data inconsistencies on the calculated trends were evaluated with the metadata and recent hourly data. Although the trend variability depended on the chosen exceedance threshold, a general long-term trend for the whole of Germany was consistently not evident. After 1951, stable positive trends occurred in the mountainous south and partly in the northern coastal region, while parts of Central Germany experienced negative trends. The frequent location shifts and the recent change in the time interval for daily rainfall could affect individual trends but were statistically insignificant for regional analyses. A case study supported that heavy rains became more erosive during the last 20 years. The results showed the merit of historical data for a better understanding of recent changes in heavy rainfall.
The universal soil loss equation (USLE) is widely used to identify areas of erosion risk at regional scales. In Brandenburg, USLE R factors are usually estimated from summer rainfall, based on a ...relationship from the 1990s. We compared estimated and calculated factors of 22 stations with 10-minutes rainfall data. To obtain more realistic estimations, we regressed the latter to three rainfall indices (total and heavy-rainfall sums). These models were applied to estimate future R factors of 188 climate stations. To assess uncertainties, we derived eight scenarios from 15 climate models and two representative concentration pathways (RCP), and compared the effects of index choice to the choices of climate model, RCP, and bias correction. The existing regression model underestimated the calculated R factors by 40%. Moreover, using heavy-rainfall sums instead of total sums explained the variability of current R factors better, increased their future changes, and reduced the model uncertainty. The impact of index choice on future R factors was similar to the other choices. Despite all uncertainties, the results indicate that average R factors will remain above past values. Instead, the extent of arable land experiencing excessive soil loss might double until the mid-century with RCP 8.5 and unchanged land management.
Sediment yields in river catchments may be modelled using a range of digital elevation models (DEM) and data algorithms. We assessed the impact of alternative choices on the evaluation of empirical ...modelling approaches. The model framework in this study consisted of the universal soil loss equation, a published local sediment delivery ratio (SDR), and commonly available input data. The study area comprised the catchments of 31 monitoring gauges for which daily data of suspended solids (SS) was available. For these stations, we studied the effects of two interpolation schemes for daily SS concentrations and of two approaches to separate erosion-related ("critical") fractions from total SS yields (SY) on model evaluation. Despite a good agreement between modelled and critical SY, the unexplained spatial variability was considerable. For additional 109 catchments, we quantified impacts of two DEM resolutions, two slope algorithms, and three slope length algorithms on modelled SY. DEM resolution and slope algorithm proved to be most relevant for the model uncertainty. High correlation coefficients between the respective alternatives revealed the minor relevance of data or algorithm choices for model quality. Correlation analyses showed that the SDR model lacked a hydrological parameter. Adjusting the modelled SDR accordingly significantly increased the explained variability of SY.
Bayesian networks (BN) have increasingly been applied in water management but not to estimate the efficacy of riparian buffer zones (RBZ). Our methodical study aims at evaluating the first BN to ...predict the RBZ efficacy to retain sediment and nutrients (dissolved, total, and particulate nitrogen and phosphorus) from widely available variables (width, vegetation, slope, soil texture, flow pathway, nutrient form). To evaluate the influence of parent nodes and how the number of states affects prediction errors, we used a predefined general BN structure, collected 580 published datasets from North America and Europe, and performed classification tree analyses and multiple 10-fold cross-validations of different BNs. These errors ranged from 0.31 (two output states) to 0.66 (five states). The outcome remained unchanged without the least influential nodes (flow pathway, vegetation). Lower errors were achieved when parent nodes had more than two states. The number of efficacy states influenced most strongly the prediction error as its lowest and highest states were better predicted than intermediate states. While the derived BNs could support or replace simple design guidelines, they are limited for more detailed predictions. More representative data on vegetation or additional nodes like preferential flow will probably improve the predictive power.
The influence of thermally sprayed aluminum coatings (Al99%; arc spraying) on the fatigue strength of gas metal arc welded (GMAW) non-alloyed structural steel specimens with respect to foundations ...for offshore wind turbines was investigated. Additionally, the corrosion protection effect of such coatings for water conditions similar to the Baltic Sea was determined. Wöhler tests were carried out on test specimens with different weld details in the as-welded condition as well as in the thermal spray coat under the consideration of different kinds of surface preparation (blast cleaning with corundum and grit). Substrate and coating were characterized by scanning electron microscopy and the influence on the residual stress states was determined. Corrosion rate monitoring via LPR measurements was carried out as well as the monitoring of the galvanic current between coated and uncoated steel to characterize the coatings’ sacrificial capability for minor defects. Fatigue strength was significantly increased through thermal spraying, especially for test specimens with welded transverse stiffeners (Δσc,var = 127 MPa after coating compared to Δσc,var = 89 MPa as welded). With a characteristic value of the stress range of Δσc,var = 153 MPa, the welded butt joint specimens already exhibited a high fatigue strength in the as-welded condition. The corrosion studies demonstrated that thermally sprayed Al99% coatings have a high resistance to corrosion in seawater environments and are suitable as planar sacrificial anodes sufficiently polarizing bare steel below 0.8 V. The combination of fatigue strength improvement and corrosion protection makes the thermally sprayed Al coatings promising for design and operation of e.g., offshore structures.
Arc brazing is an alternative joining technology well-suited for processing thermally sensitive materials and to produce mixed material connections. Due to the technological similarities of gas metal ...arc brazing to gas metal arc welding, it can be assumed that the process-related hydrogen input is of similar magnitude for both joining technologies. Since diffusible hydrogen is known to cause embrittlement in metallic materials, it is necessary to know the amount of diffusible hydrogen introduced by different manufacturing processes. Regarding the qualification of welding procedures, hydrogen ingress is an important factor to evaluate the risk of hydrogen-assisted cold cracking, especially when processing high-strength steels. For arc brazing, there is a lack of knowledge about the process-related hydrogen input. Hence, to study the influence of different brazing filler materials and varying levels of heat input on the diffusible hydrogen concentration in arc braze metal, a methodology to determine hydrogen content in arc weld metal in accordance with international standard ISO 3690 based on carrier gas hot extraction was applied to arc brazed specimens. Very low diffusible hydrogen concentrations of about HD = 0.1 to 0.3 mL/100 g were found for GMAB without significant influence of arc energy or filler metal used.
Ich bin im März 2020 im Grunde zeitgleich mit dem ersten Lockdown und den ersten Verschärfungen aufgrund der Corona-Pandemie hierhergekommen. Das sind auch ehrenwerte Aufgaben, die dazu gehören, ...damit es einem Patienten gut geht. Ob das im Endeffekt gut ist, wird die Zeit zeigen. Gut ausgebildetes Personal, das gute Arbeitsbedingungen hat — das heißt „mehr Qualität“.
Growing population and urbanization challenge water resources sustainability and require stringent solutions in terms of emission measurements and pollution controls. Advancements in observation ...techniques have improved the availability of impervious surface data that cover both urban and non-urban areas to assess the impacts of urbanization. However, most models used in macroscale studies continue to derive surface imperviousness based on land-use classes and population data, and the contributions of non-urban impervious surfaces to runoff and nutrient emissions remain largely ignored. Effects of different impervious surface data on the predicted runoff and nutrient emissions is investigated in this study for macroscale urban and non-urban areas in tandem by means of an extended urban module MONERIS - PCRaster to enable scenarios with high-resolution imperviousness data. The results showed that approximately 70% of the total runoff and nutrient emissions nationwide originated from low-to-medium populated impervious surfaces rather than from major urban catchments. Using high-resolution imperviousness data at various aggregation levels resulted in lower biased outputs of predicted runoff and nutrient emissions when compared to results using the estimated impervious data from land-use and population information. The impervious surface shares between urban and non-urban lands revealed the opposite trends of urbanization developments in the less populated areas versus an increasing contribution of emissions from non-urban areas rather than urban centers in densely populated municipalities. Overall, the non-urban impervious surface areas contributed 5–20% of the “hidden” runoff volumes and nutrient emissions from all impervious areas. The results of this study highlight the need of model adaptations regarding the increased availability of high-resolution imperviousness data and the trend of urbanization development beyond urban areas for more accurate quantification of potential flood risks and emission hotspots of macroscale urbanized areas for sustainable water resources management.
•The study quantified impervious surface impacts on macroscale urban emissions.•Highest total national emissions originated from low-to-medium populated areas.•Population-derived imperviousness underestimated emissions from low populated areas.•Satellite-image impervious surface data identified critical emission hotspots.•Non-urban impervious areas represented 5–20% of the total emissions.
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