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- Impacts of distinct spatial arrangements of impervious surfaces on runoff and sediment fluxes from laboratory experimentsPublication . Ferreira, C. S. S.; Moruzzi, R.; Isidoro, Jorge M. G. P.; Tudor, M.; Vargas, M.; Ferreira, A. J. D.; de Lima, J. L. M. P.Urbanization affects runoff processes and sediment transport, but the magnitude of the impacts remains poorly understood. Different spatial patterns of pervious and impervious surfaces influence flow and sediment connectivity between hillslopes and stream networks. Following years of research on the peri-urbanizing Ribeira dos Covoes catchment in Portugal, this study uses laboratory rainfall simulation experiments to better assess the impact of soil and pavement patterns on runoff (amount, runoff start and stop times) and sediment transport. Based on urban cores observed in the study catchment, the investigation focused on seven spatial patterns: bare soil (S), 100% pavement (P), and 60% pavement under continuous - C - surface placed upslope (CU) and downslope (CD), and dispersed - D - over the surface with regular (DR), irregular (DI) and linear (DL) distribution. A 1.00 m x 1.00 m flume, 0.05 m deep with a 9 degrees slope, facilitated the experiments. The study used sandy-loam soil (1500 kg m(-3)) with concrete slabs representing pavement. Each experiment comprised a series of four rainfall simulations, each lasting 20 min (50 mm h(-1)), separated by 30-min intervals, to assess the impact of different initial soil moisture conditions. Results indicate that both spatial pattern and soil moisture drive runoff. Under dry conditions, CD provides runoff that is 7 times faster and about 4% higher than that for CU. Already wet conditions, however, produced 12% more runoff on CU than on CD. The greater runoff arose from faster soil saturation, driven by soil moisture increasing more quickly during the rainfall, as well as upstream runoff from paved surfaces, though runoff took longer to reach the outlet. The dispersed pavement pattern only affected runoff amount, with DL producing the highest coefficients (40-71%) and DI the lowest (25-55%), since longer flow paths increase the opportunities for water infiltration. Additionally, CU yielded 40% more sediment transport than CD, but the three dispersed patterns did not show a significant impact (p > 0.05). The results suggest that appropriate planning can reduce flood hazard and land degradation in urban areas, in particular by using dispersed patterns of sealed surfaces to enhance water infiltration and retention. (C) 2019 Elsevier Ltd. All rights reserved.
- Infiltration of Portuguese cobblestone pavements - An exploratory assessment using a double-ring infiltrometerPublication . Rocheta, Vera Lúcia; MGP Isidoro, Jorge; de Lima, Joao L. M. P.The present study aims to evaluate small-scale infiltration losses of Portuguese cobblestone pavements. This type of pavement consists of rectangular hand-cut natural stones, mainly limestone, with different sizes and it is the most usual type of pavement for sidewalks and squares in Portuguese villages and cities. Portuguese cobblestone pavement can also be seen in several urban environments worldwide. A double-ring infiltrometer under constant and falling head was used for the field research work. Portuguese cobblestone pavements with small and coarse blocks were studied. The latter yield lower infiltration rates when compared to the former. The results show that, despite the block size, Portuguese cobblestone pavement contribute to reduce runoff, when compared with other impervious urban pavements.
- Enhancing the spatial rainfall uniformity of pressurized nozzle simulatorsPublication . Silveira, Alexandre; MGP Isidoro, Jorge; Deus, Fábio P. de; Reis, Simone Siqueira dos; Silva, António Marciano da; Gonçalves, Flávio A.; Bretanha Junker Menezes, Paulo Henrique; Tiezzi, Rafael de O.Purpose - Rainfall simulators are used on experimental hydrology, in areas such as, e.g., urban drainage and soil erosion, with important timesaving when compared to real scale hydrological monitoring. The purpose of this paper is to contribute to increase the quality of rainfall simulation, namely, for its use with scaled physical models. Design/methodology/approach - Two pressurized rainfall simulators are considered. M1 uses three HH-W 1/4 FullJet nozzles under an operating pressure of 166.76 kPa and was tested over a 4.00 m length by 2.00 m width V-shaped surface. M2 was prepared to produce artificial rainfall over an area of 10.00m length by 10.00m width. The spatial distribution of rainfall produced from a single nozzle was characterized in order to theoretically find the best positioning for nozzles to cover the full 100m(2) area with the best possible rainfall uniformity. Findings - Experiments with M1 led to an average rainfall intensity of 76.77-82.25 mm h(-1) with a 24.88 per cent variation coefficient and a Christiansen Uniformity Coefficient (CUC) of 78.86 per cent. The best result with M2 was an average rainfall intensity of 75.12-76.83 mm h(-1) with a 21.23 per cent variation coefficient and a CUC of 83.05 per cent. Practical implications - This study contributes to increase the quality of artificial rainfall produced by pressurized rainfall simulators. Originality/value - M2 is the largest rainfall simulator known by the authors worldwide. Its use on rainfall-runoff studies (e.g. urban areas, erosion, pollutant transport) will allow for a better understanding of complex surface hydrology processes.