J. Hydrol. Hydromech., Vol. 66, No. 1, 2018, p. 1 - 11, doi: 10.1515/johh-2017-0037
Scientific Paper, English

Peter Chifflard, Julius Kranl, Georg zur Strassen, Harald Zepp: The significance of soil moisture in forecasting characteristics of flood events. A statistical analysis in two nested catchments

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• We examine the feasibility and added value of upscaling point data of soil moisture from a small- to a mesoscale catchment for the purpose of single-event flood prediction. We test the hypothesis that in a given catchment, the present soil moisture status is a key factor governing peak discharge, flow volume and flood duration. Multiple regression analyses of rainfall, pre-event discharge, single point soil moisture profiles from representative locations and peak discharge, discharge duration, discharge volume are discussed. The soil moisture profiles are selected along a convergent slope connected to the groundwater in flood plain within the small-scale catchment Husten (2.6 km²), which is a headwater catchment of the larger Hüppcherhammer catchment (47.2 km², Germany). Results show that the number of explanatory variables in the regression models is higher in summer (up to 8 variables) than in winter (up to 3 variables) and higher in the meso-scale catchment than in the small-scale catchment (up to 2 variables). Soil moisture data from selected key locations in the small catchment improves the quality of regression models established for the meso-scale catchment. For the different target variables peak discharge, discharge duration and discharge volume the adding of the soil moisture from the flood plain and the lower slope as explanatory variable improves the quality of the regression model by 15%, 20% and 10%, respectively, especially during the summer season. In the winter season the improvement is smaller (up to 6%) and the regression models mainly include rainfall characteristics as explanatory variables. The appearance of the soil moisture variables in the stepwise regression indicates their varying importance, depending on which characteristics of the discharge are focused on. Thus, we conclude that point data for soil moisture in functional landscape elements describe the catchments’ initial conditions very well and may yield valuable information for flood prediction and warning systems.
  
  KEY WORDS: Soil moisture; Runoff prediction; Catchment hydrology; Spatial-temporal variability; Multivariate statistics.
  
  Address:
  - Peter Chifflard, Department of Geography, Philipps-University Marburg, Deutschhausstr. 10, 35032 Marburg, Germany. (Corresponding author. Tel.:+49(0)6421 28-24155 Fax.: +49(0)6421 28-28950 Email: peter.chifflard@geo.uni-marburg.de)
  - Julius Kranl, Department of Geography, Ruhr- University Bochum, Universitätsstr. 150, Building NA, 44780 Bochum, Germany.
  - Georg zur Strassen, Ruhrverband, Kronprinzenstr. 37, 45128 Essen, Germany.
  - Harald Zepp, Department of Geography, Ruhr- University Bochum, Universitätsstr. 150, Building NA, 44780 Bochum, Germany.

J. Hydrol. Hydromech., Vol. 66, No. 1, 2018, p. 12 - 22, doi: 10.1515/johh-2017-0044
Scientific Paper, English

Viliam Macura, Zuzana Štefunková, Martina Majorošová, Peter Halaj, Andrej Škrinár: Influence of discharge on fish habitat suitability curves in mountain watercourses in IFIM methodology

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• In this study, the quality of the aquatic habitats of mountain and piedmont streams was evaluated using the ‘Instream Flow Incremental Methodology (IFIM)’ decision-making tool. The quality of habitats was interpreted from the behaviour of bioindicators in the form of habitat suitability curves (HSCs). From 1995 until the present, 59 different reaches of 43 mountain streams in Slovakia and 3 validation reaches were evaluated, and the results analysed. The aim of this study was to generalize the parameters of the HSCs for the brown trout. The generalized curves will be useful for water management planning. It is difficult and time-consuming to take hydrometrical and ichthyological measurements at different water levels. Therefore, we developed a methodology for modifying suitability curves based on an ichthyological survey during a low flow and a flow at which fish lose the ability to resist the flow velocity. The study provides the information how such curves can be modified for a wider flow range. In summary, this study shows that generalized HSCs provide representative data that can be used to support both the design of river restoration and the assessment of the impacts of the water use or of climate change on stream habitat quality.
  
  KEY WORDS: Instream Flow Incremental Methodology (IFIM); Weighted Usable Area (WUA); Habitat suitability curves (HSCs); Brown trout.
  
  Address:
  - Viliam Macura, Department of Land and Water Resources Management, Faculty of Civil Engineering, Slovak University of Technology in Bratislava, Bratislava, Slovakia.
  - Zuzana Štefunková, Department of Hydraulic Engineering, Faculty of Civil Engineering, Slovak University of Technology in Bratislava, Bratislava, Slovakia.
  - Martina Majorošová, Department of Land and Water Resources Management, Faculty of Civil Engineering, Slovak University of Technology in Bratislava, Bratislava, Slovakia.
  - Peter Halaj, Department of Landscape Engineering, Faculty of Horticulture and Landscape Engineering, Slovak University of Agriculture in Nitra, Nitra, Slovakia.
  - Andrej Škrinár, Department of Land and Water Resources Management, Faculty of Civil Engineering, Slovak University of Technology in Bratislava, Bratislava, Slovakia. (Corresponding author. Tel.: Fax.: Email: andrej.skrinar@stuba.sk)

J. Hydrol. Hydromech., Vol. 66, No. 1, 2018, p. 23 - 31, doi: 10.1515/johh-2017-0032
Scientific Paper, English

Magdalena M. Mrokowska, Paweł M. Rowiński, Leszek Książek, Andrzej Strużyński, Maciej Wyrębek, Artur Radecki-Pawlik: Laboratory studies on bedload transport under unsteady flow conditions

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• Two sets of triangular hydrographs were generated in a 12-m-long laboratory flume for two sets of initial bed conditions: intact and water-worked gravel bed. Flowrate ranging from 0.0013 m3 s–1 to 0.0456 m3 s–1, water level ranging from 0.02 m to 0.11 m, and cumulative mass of transported sediment ranging from 4.5 kg to 14.2 kg were measured. Then, bedload transport rate, water surface slope, bed shear stress, and stream power were evaluated. The results indicated the impact of initial bed conditions and flow unsteadiness on bedload transport rate and total sediment yield. Difference in ratio between the amount of supplied sediment and total sediment yield for tests with different initial conditions was observed. Bedload rate, bed shear stress, and stream power demonstrated clock-wise hysteretic relation with flowrate. The study revealed practical aspects of experimental design, performance, and data analysis. Water surface slope evaluation based on spatial water depth data was discussed. It was shown that for certain conditions stream power was more adequate for the analysis of sediment transport dynamics than the bed shear stress. The relations between bedload transport dynamics, and flow and sediment parameters obtained by dimensional and multiple regression analysis were presented.
  
  KEY WORDS: Bedload; Bed shear stress; Dimensional analysis; Hysteresis; Stream power; Unsteady flow.
  
  Address:
  - Magdalena M. Mrokowska, Institute of Geophysics, Polish Academy of Sciences, ul. Ks. Janusza 64, 01-452 Warsaw, Poland. (Corresponding author. Tel.:+48 22 69 15 849 Fax.: +48 22 87 76 722 Email: m.mrokowska@igf.edu.pl)
  - Paweł M. Rowiński, Institute of Geophysics, Polish Academy of Sciences, ul. Ks. Janusza 64, 01-452 Warsaw, Poland.
  - Leszek Książek, University of Agriculture in Krakow, Faculty of Environmental Engineering and Land Surveying, Department of Hydraulic Engineering and Geotechnics, Al. Mickiewicza 24/28, 30-059 Kraków, Poland.
  - Andrzej Strużyński, University of Agriculture in Krakow, Faculty of Environmental Engineering and Land Surveying, Department of Hydraulic Engineering and Geotechnics, Al. Mickiewicza 24/28, 30-059 Kraków, Poland.
  - Maciej Wyrębek, University of Agriculture in Krakow, Faculty of Environmental Engineering and Land Surveying, Department of Hydraulic Engineering and Geotechnics, Al. Mickiewicza 24/28, 30-059 Kraków, Poland.
  - Artur Radecki-Pawlik, University of Agriculture in Krakow, Faculty of Environmental Engineering and Land Surveying, Department of Hydraulic Engineering and Geotechnics, Al. Mickiewicza 24/28, 30-059 Kraków, Poland. Institute of Structural Mechanics, Cracow University of Technology, ul. Warszawska 24, 31-155 Kraków, Poland.

J. Hydrol. Hydromech., Vol. 66, No. 1, 2018, p. 32 - 42, doi: 10.1515/johh-2017-0041
Scientific Paper, English

Jaime G. Cuevas, José L. Arumí, Alejandra Zúniga-Feest, Christian Little: An unusual kind of diurnal streamflow variation

 Full Text in PDF     44 DOWNLOADS

• During hydrological research in a Chilean swamp forest, we noted a pattern of higher streamflows close to midday and lower ones close to midnight, the opposite of an evapotranspiration (Et)-driven cycle. We analyzed this diurnal streamflow signal (DSS), which appeared mid-spring (in the growing season). The end of this DSS coincided with a sustained rain event in autumn, which deeply affected stream and meteorological variables. A survey along the stream revealed that the DSS maximum and minimum values appeared 6 and 4 hours earlier, respectively, at headwaters located in the mountain forests/ plantations than at the control point in the swamp forest. Et in the swamp forest was higher in the morning and in the late afternoon, but this process could not influence the groundwater stage. Trees in the mountain headwaters reached their maximum Ets in the early morning and/or close to midday. Our results suggest that the DSS is a wave that moves from forests high in the mountains towards lowland areas, where Et is decoupled from the DSS. This signal delay seems to convert the link between streamflow and Et in an apparent, but spurious positive relationship. It also highlights the role of landscape heterogeneity in shaping hydrological processes.
  
  KEY WORDS: Evapotranspiration; Groundwater; Riparian zones; Streamflow; Swamp forests.
  
  Address:
  - Jaime G. Cuevas, Centro de Estudios Avanzados en Zonas Áridas (CEAZA), Av. Raúl Bitrán 1305, La Serena, Chile. Instituto de Ingeniería Agraria y Suelos, Universidad Austral de Chile, Valdivia, Chile. (Corresponding author. Tel.:+56 51 2204378 Fax.: Email: jxcuevas@ceaza.cl)
  - José L. Arumí, Facultad de Ingeniería Agrícola, Departamento de Recursos Hídricos, Centro CRHIAM, Universidad de Concepción, Chillán, Chile.
  - Alejandra Zúniga-Feest, Centro de Investigaciones en Suelos Volcánicos (CISVo), Universidad Austral de Chile, Valdivia, Chile. Laboratorio de Biología Vegetal, Instituto de Ciencias Ambientales y Evolutivas, Facultad de Ciencias, Universidad Austral de Chile, Valdivia, Chile.
  - Christian Little, Instituto Forestal (INFOR), Sede Los Ríos, Fundo Teja Norte s/n, Valdivia, Chile. Center For Climate and Resilience Research (CR)2, Chile.

J. Hydrol. Hydromech., Vol. 66, No. 1, 2018, p. 43 - 54, doi: 10.1515/johh-2017-0027
Scientific Paper, English

Michal Jenicek, Hana Pevna, Ondrej Matejka: Canopy structure and topography effects on snow distribution at a catchment scale: Application of multivariate approaches

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• The knowledge of snowpack distribution at a catchment scale is important to predict the snowmelt runoff. The objective of this study is to select and quantify the most important factors governing the snowpack distribution, with special interest in the role of different canopy structure. We applied a simple distributed sampling design with measurement of snow depth and snow water equivalent (SWE) at a catchment scale. We selected eleven predictors related to character of specific localities (such as elevation, slope orientation and leaf area index) and to winter meteorological conditions (such as irradiance, sum of positive air temperature and sum of new snow depth). The forest canopy structure was described using parameters calculated from hemispherical photographs. A degree-day approach was used to calculate melt factors. Principal component analysis, cluster analysis and Spearman rank correlation were applied to reduce the number of predictors and to analyze measured data. The SWE in forest sites was by 40% lower than in open areas, but this value depended on the canopy structure. The snow ablation in large openings was on average almost two times faster compared to forest sites. The snow ablation in the forest was by 18% faster after forest defoliation (due to the bark beetle). The results from multivariate analyses showed that the leaf area index was a better predictor to explain the SWE distribution during accumulation period, while irradiance was better predictor during snowmelt period. Despite some uncertainty, parameters derived from hemispherical photographs may replace measured incoming solar radiation if this meteorological variable is not available.
  
  KEY WORDS: Snowpack distribution; Canopy structure; Leaf area index; Degree-day; Bark beetle.
  
  Address:
  - Michal Jenicek, Department of Physical Geography and Geoecology, Faculty of Science, Charles University, Albertov 6, 128 43 Prague, Czech Republic. (Corresponding author. Tel.: Fax.: Email: michal.jenicek@natur.cuni.cz)
  - Hana Pevna, Department of Physical Geography and Geoecology, Faculty of Science, Charles University, Albertov 6, 128 43 Prague, Czech Republic.
  - Ondrej Matejka, Department of Physical Geography and Geoecology, Faculty of Science, Charles University, Albertov 6, 128 43 Prague, Czech Republic.

J. Hydrol. Hydromech., Vol. 66, No. 1, 2018, p. 55 - 64, doi: 10.1515/johh-2017-0045
Scientific Paper, English

Dariusz Wrzesiński, Leszek Sobkowiak: Detection of changes in flow regime of rivers in Poland

 Full Text in PDF     66 DOWNLOADS

• The aim of this study is to detect changes in flow regime of rivers in Poland. On the basis of daily discharges recorded in 1951–2010 at 159 gauging stations located on 94 rivers regularities in the variability of the river flow characteristics in the multi-year period and in the annual cycle were identified and also their spatial uniformity was examined. In order to identify changes in the characteristics of river regime, similarities of empirical distribution functions of the 5-day sets (pentads) of discharges were analyzed and the percent shares of similar and dissimilar distributions of the 5-day discharge frequencies in the successive 20-year sub-periods were compared with the average values of discharges recorded in 1951–2010. Three alternative methods of river classification were employed and in the classification procedure use was made of the Ward’s hierarchical clustering method. This resulted in identification of groups of rivers different in terms of the degree of transformation of their hydrological regimes in the multi-year and annual patterns.
  
  KEY WORDS: Flow regime; Detection of changes; Empirical distribution function; Typological classification; Ward’s hierarchical clustering method.
  
  Address:
  - Dariusz Wrzesiński, Adam Mickiewicz University, Institute of Physical Geography and Environmental Planning, Chair of Hydrology and Water Management, Bogumiła Krygowskiego 10 str., 61-680 Poznań, Poland.
  - Leszek Sobkowiak, Adam Mickiewicz University, Institute of Physical Geography and Environmental Planning, Chair of Hydrology and Water Management, Bogumiła Krygowskiego 10 str., 61-680 Poznań, Poland. (Corresponding author. Tel.: Fax.: Email: lesob@amu.edu.pl)

J. Hydrol. Hydromech., Vol. 66, No. 1, 2018, p. 65 - 78, doi: 10.1515/johh-2017-0039
Scientific Paper, English

Fasikaw A. Zimale, Mamaru A. Moges, Muluken L. Alemu, Essayas K. Ayana, Solomon S. Demissie, Seifu A. Tilahun, Tammo S. Steenhuis: Budgeting suspended sediment fluxes in tropical monsoonal watersheds with limited data: the Lake Tana basin

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• Soil erosion decreases soil fertility of the uplands and causes siltation of lakes and reservoirs; the lakes and reservoirs in tropical monsoonal African highlands are especially affected by sedimentation. Efforts in reducing loads by designing management practices are hampered by lack of quantitative data on the relationship of erosion in the watersheds and sediment accumulation on flood plains, lakes and reservoirs. The objective of this study is to develop a prototype quantitative method for estimating sediment budget for tropical monsoon lakes with limited observational data. Four watersheds in the Lake Tana basin were selected for this study. The Parameter Efficient Distributed (PED) model that has shown to perform well in the Ethiopian highlands is used to overcome the data limitations and recreate the missing sediment fluxes. PED model parameters are calibrated using daily discharge data and the occasionally collected sediment concentration when establishing the sediment rating curves for the major rivers. The calibrated model parameters are then used to predict the sediment budget for the 1994–2009 period. Sediment retained in the lake is determined from two bathymetric surveys taken 20 years apart whereas the sediment leaving the lake is calculated based on measured discharge and observed sediment concentrations. Results show that annually on average 34 t/ha/year of sediment is removed from the gauged part of the Lake Tana watersheds. Depending on the up-scaling method from the gauged to the ungauged part, 21 to 32 t/ha/year (equivalent to 24–38 Mt/year) is transported from the upland watersheds of which 46% to 65% is retained in the flood plains and 93% to 96% is trapped on the flood plains and in the lake. Thus, only 4–7% of all sediment produced in the watersheds leaves the Lake Tana Basin.
  
  KEY WORDS: Erosion; Saturation excess; Hydrology; Discharge; Flood plain; Ethiopia; East Africa; Horn of Africa.
  
  Address:
  - Fasikaw A. Zimale, Faculty of Civil and Water Resources Engineering, PhD program in Integrated Water Management, Bahir Dar Institute of Technology, Bahir Dar University, Bahir Dar, Ethiopia.
  - Mamaru A. Moges, Faculty of Civil and Water Resources Engineering, PhD program in Integrated Water Management, Bahir Dar Institute of Technology, Bahir Dar University, Bahir Dar, Ethiopia.
  - Muluken L. Alemu, Faculty of Civil and Water Resources Engineering, PhD program in Integrated Water Management, Bahir Dar Institute of Technology, Bahir Dar University, Bahir Dar, Ethiopia.
  - Essayas K. Ayana, Faculty of Civil and Water Resources Engineering, Bahir Dar Institute of Technology, Bahir Dar University, Bahir Dar, Ethiopia. Department of Ecology, Evolution and Environmental Biology, Columbia University, New York, NY, USA.
  - Solomon S. Demissie, Ethiopian Institute of Water Resources, Addis Ababa, Ethiopia.
  - Seifu A. Tilahun, Faculty of Civil and Water Resources Engineering, Bahir Dar Institute of Technology, Bahir Dar University, Bahir Dar, Ethiopia.
  - Tammo S. Steenhuis, Faculty of Civil and Water Resources Engineering, Bahir Dar Institute of Technology, Bahir Dar University, Bahir Dar, Ethiopia. Department of Biological and Environmental Engineering, 206 Riley Robb Hall, Cornell University, Ithaca NY 14853 USA. (Corresponding author. Tel.: Fax.: Email: tss1@cornell.edu)

J. Hydrol. Hydromech., Vol. 66, No. 1, 2018, p. 79 - 86, doi: 10.1515/johh-2017-0043
Scientific Paper, English

Shengqi Jian, Xueli Zhang, Dong Li, Deng Wang, Zening Wu, Caihong Hu: The effects of stemflow on redistributing precipitation and infiltration around shrubs

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• The experiments of stemflow of two semiarid shrubs (Caragana korshinskii and Hippophae rhamnoides) and its effect on soil water enhancement were conducted from 1st May to 30th September of 2009–2013 in the Chinese Loess Plateau. Stemflow values in C. korshinskii and H. rhamnoides averaged 6.7% and 2.4% of total rainfall. The rainfall threshold for stemflow generation was 0.5 and 2.5 mm for C. korshinskii and H. rhamnoides. When rainfall was less than 17.0 mm, the funnelling ratios were highly variable, however, stable funnelling ratios were found for rainfall greater than 17.0 mm for C. korshinskii. The funnelling ratios of H. rhamnoides first increased until a threshold value of 10.0 mm and then the funnelling ratios begin stabilize. The wetting front depths in the area around stem was 1.4–6.7 and 1.3–2.9 times deeper than area outside the canopy for C. korshinskii and H. rhamnoides. Soil moisture at soil depth 0–200 cm was 25.6% and 23.4% higher in soil around stem than that outside canopy for C. korshinskii and H. rhamnoides. The wetting front advanced to depths of 120 and 100 cm in the area around stem and to depths of 50 cm in the area outside the canopy for C. korshinskii and H. rhamnoides suggested that more rain water can be conserved into the deep soil layers through shrub stemflow. Soil moisture was enhanced in the area outside the shrub canopy, only when rainfall depth is > 4.7 and 5.1 mm, which is an effective rainfall for the area for C. korshinskii and H. rhamnoides. While for the area around stem of C. korshinskii and H. rhamnoides, the corresponding threshold values are 3.2 and 4.3 mm. These results confirmed that stemflow has a positive effect on soil moisture balance of the root zone and the enhancement in soil moisture of deeper soil layers.
  
  KEY WORDS: Stemflow; Wetting front; C. korshinskii; H. rhamnoides; Loess Plateau; China.
  
  Address:
  - Shengqi Jian, College of Water Conservancy & Environment, Zhengzhou University, Science road 100, Zhengzhou, China.
  - Xueli Zhang, Zhongyuan District Environmental Protection Bureau, Zhengzhou City, Gangpo road 4, Zhengzhou, China.
  - Dong Li, College of Water Conservancy & Environment, Zhengzhou University, Science road 100, Zhengzhou, China.
  - Deng Wang, College of Water Conservancy & Environment, Zhengzhou University, Science road 100, Zhengzhou, China.
  - Zening Wu, College of Water Conservancy & Environment, Zhengzhou University, Science road 100, Zhengzhou, China.
  - Caihong Hu, College of Water Conservancy & Environment, Zhengzhou University, Science road 100, Zhengzhou, China. (Corresponding author. Tel.:+86 18603814081 Fax.: Email: jiansq@zzu.edu.cn)

J. Hydrol. Hydromech., Vol. 66, No. 1, 2018, p. 87 - 96, doi: 10.1515/johh-2017-0031
Scientific Paper, English

Nina Stoppe, Rainer Horn: Microstructural strength of tidal soils – a rheometric approach to develop pedotransfer functions

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• Differences in soil stability, especially in visually comparable soils can occur due to microstructural processes and interactions. By investigating these microstructural processes with rheological investigations, it is possible to achieve a better understanding of soil behaviour from the mesoscale (soil aggregates) to macroscale (bulk soil). In this paper, a rheological investigation of the factors influencing microstructural stability of riparian soils was conducted. Homogenized samples of Marshland soils from the riparian zone of the Elbe River (North Germany) were analyzed with amplitude sweeps (AS) under controlled shear deformation in a modular compact rheometer MCR 300 (Anton Paar, Germany) at different matric potentials. A range physicochemical parameters were determined (texture, pH, organic matter, CaCO3 etc.) and these factors were used to parameterize pedotransfer functions. The results indicate a clear dependence of microstructural elasticity on texture and water content. Although the influence of individual physicochemical factors varies depending on texture, the relevant features were identified taking combined effects into account. Thus, stabilizing factors are: organic matter, calcium ions, CaCO3 and pedogenic iron oxides; whereas sodium ions and water content represent structurally unfavorable factors. Based on the determined statistical relationships between rheological and physicochemical parameters, pedotransfer functions (PTF) have been developed.
  
  KEY WORDS: Rheology; Deformation; Soil micromechanics; Structural stability; Structure degradation; Pedotransfer functions.
  
  Address:
  - Nina Stoppe, Institute of Plant Nutrition and Soil Science, Christian-Albrechts-University Kiel, Hermann-Rodewaldstr. 2, D-24118 Kiel, Germany. (Corresponding author. Tel.:0049 431 880-4079 Fax.: 0049 431 880-2940 Email: n.stoppe@soils.uni-kiel.de)
  - Rainer Horn, Institute of Plant Nutrition and Soil Science, Christian-Albrechts-University Kiel, Hermann-Rodewaldstr. 2, D-24118 Kiel, Germany.

J. Hydrol. Hydromech., Vol. 66, No. 1, 2018, p. 97 - 106, doi: 10.1515/johh-2017-0034
Scientific Paper, English

Saleh Yousefi, Seyed Hamidreza Sadeghi, Somayeh Mirzaee, Martine van der Ploeg, Saskia Keesstra, Artemi Cerda: Spatio-temporal variation of throughfall in a hyrcanian plain forest stand in Northern Iran

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• Elucidating segregation of precipitation in different components in forest stands is important for proper forest ecosystems management. However, there is a lack of information on important rainfall components viz. throughfall, interception and stemflow in forest watersheds particularly in developing countries. We therefore investigated the spatiotemporal variation of important component of throughfall for a forest stand in a Hyrcanian plain forest in Noor City, northern Iran. The study area contained five species of Quercus castaneifolia, Carpinus betulus, Populus caspica and Parrotia persica. The research was conducted from July 2013 to July 2014 using a systematic sampling method. Ninetysix throughfall collectors were installed in a 3.5 m × 3.5 m grid cells. The canopy covers during the growing/leaf-on (i.e., from May to November) and non-growing/leaf-off (i.e., from December to March) seasons were approximately 41% and 81%, respectively. The mean cumulative throughfall during the study period was 623±31 mm. The average throughfall (TF) as % of rainfall (TFPR) during leaf-on and leaf-off periods were calculated 56±14% and 77±10%, respectively. TF was significantly (R2 = 0.97, p = 0.00006) correlated with gross precipitation. Percent of canopy cover was not correlated with TF except when gross precipitation was <30 mm. A comparison between leaf-off and leaf-on conditions indicated a significantly higher TFPR and corresponding hotspots during leaf-on period. TFPR also differed between seasons with a maximum amount in winter (82%). The results of the study can be effectively used by forest watershed managers for better perception of hydrological behavior of the Hyrcanian forest in the north of Iran under different silvicultural circumstances leading to getting better ecosystem services.
  
  KEY WORDS: Caspian Hyrcanian Forest; Deciduous forest; Forest hydrology; Interception storage; Precipitation loss.
  
  Address:
  - Saleh Yousefi, Department of Watershed Management, Faculty of Natural Resources, Tarbiat Modares University, Tehran, Iran.
  - Seyed Hamidreza Sadeghi, Department of Watershed Management Engineering, Faculty of Natural Resources, Tarbiat Modares University, Noor 46417-76489, Iran. (Corresponding author. Tel.:+98 11 44553102 Fax.: +98 11 44553909 Email: sadeghi@modares.ac.ir)
  - Somayeh Mirzaee, Department of Watershed Management, Faculty of Natural Resources, Lorestan University, Khoramabad, Iran.
  - Martine van der Ploeg, Soil Physics and Land Management Group, Wageningen University, Droevendaalsesteeg 4, 6708PB Wageningen, The Netherlands.
  - Saskia Keesstra, Soil Physics and Land Management Group, Wageningen University, Droevendaalsesteeg 4, 6708PB Wageningen, The Netherlands.
  - Artemi Cerda, Soil Erosion and Degradation Research Group, Department of Geography, University of Valencia, Valencia, Spain.

J. Hydrol. Hydromech., Vol. 66, No. 1, 2018, p. 107 - 120, doi: 10.1515/johh-2017-0028
Scientific Paper, English

Paola Gualtieri, Sergio De Felice, Vittorio Pasquino, Guelfo Pulci Doria: Use of conventional flow resistance equations and a model for the Nikuradse roughness in vegetated flows at high submergence

 Full Text in PDF     54 DOWNLOADS

• This study examines the problem of flow resistance due to rigid vegetation in open channel flow. The reliability of the conventional flow resistance equations (i.e. Keulegan, Manning and Chézy-Bazin) for vegetated flows at high submergence, i.e. h/k >5, (where h = flow depth and k = vegetation height) is assessed. Several modern flow resistance equations based on a two-layer approach are examined, showing that they transform into the conventional equations at high submergences. To compare the conventional flow resistance equations at high submergences, an experimental methodology is proposed and applied to the experimental data reported in the literature and collected for this study. The results demonstrate the reliability of the Keulegan equation in predicting the flow resistance. Based on the obtained results, a model to evaluate the Nikuradse equivalent sand-grain roughness, kN, starting from the vegetation height and density, is proposed and tested.
  
  KEY WORDS: Open channel flows; Vegetated flows; Rigid vegetation; Flow resistance; Roughness coefficients; Nikuradse equivalent sand-grain roughness.
  
  Address:
  - Paola Gualtieri, University of Naples Federico II, Department of Civil, Architectural and Environmental Engineering, Via Claudio 21 80125 Napoli, Italy. (Corresponding author. Tel.: Fax.: Email: paola.gualtieri@unina.it)
  - Sergio De Felice, University of Naples Federico II, Department of Civil, Architectural and Environmental Engineering, Via Claudio 21 80125 Napoli, Italy.
  - Vittorio Pasquino, University of Naples Federico II, Department of Civil, Architectural and Environmental Engineering, Via Claudio 21 80125 Napoli, Italy.
  - Guelfo Pulci Doria

J. Hydrol. Hydromech., Vol. 66, No. 1, 2018, p. 121 - 128, doi: 10.1515/johh-2017-0042
Scientific Paper, English

Gianandrea Vittorio Messa, Renan De Lima Branco, José Gilberto Dalfré Filho, Stefano Malavasi: A combined CFD-experimental method for abrasive erosion testing of concrete

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• Serious damage may occur to concrete hydraulic structures, such as water galleries, spillways, and stilling basins, due to the abrasive erosion caused by the presence of solid particles in the flow. This underlines the importance of being capable in providing characterization of the concrete from the point of view of its vulnerability to abrasive erosion, in order to improve the design of the structure and the material selection. Nevertheless, the existing apparatus for concrete abrasive erosion testing are either far from allowing realistic simulation of the actual environment in which this phenomenon occurs, or show a large degree of complexity and cost. An alternative method has been developed with the aid of Computational Fluid Dynamics (CFD). CFD was first employed to verify the effectiveness of a new laboratory equipment. Afterwards, a parameter has been introduced which, by successful comparison against preliminary experiments, proved suitable to quantify the effect of the fluid dynamic conditions on the concrete abrasive erosion, thereby opening the way to CFD-based customization of the apparatus. In the future, the synergy of numerical and physical modelling will allow developing predictive models for concrete erosion, making it possible to reliably simulate real structures.
  
  KEY WORDS: Abrasive erosion; Computational fluid dynamics; Concrete; Experiments; Two-phase flow.
  
  Address:
  - Gianandrea Vittorio Messa, FLUIDLab group, Department of Civil and Environmental Engineering, Politecnico di Milano, Piazza Leonardo Da Vinci, 32, 20133 Milano, Italy. (Corresponding author. Tel.:+39 02 2399 6287 Fax.: Email: gianandreavittorio.messa@polimi.it)
  - Renan De Lima Branco, College of Civil Engineering, Architecture and Urbanism, University of Campinas, Av. Albert Einstein, 951, Campinas, SP, Brazil.
  - José Gilberto Dalfré Filho, College of Civil Engineering, Architecture and Urbanism, University of Campinas, Av. Albert Einstein, 951, Campinas, SP, Brazil.
  - Stefano Malavasi, FLUIDLab group, Department of Civil and Environmental Engineering, Politecnico di Milano, Piazza Leonardo Da Vinci, 32, 20133 Milano, Italy.