Abstract The paper is devoted to the long-term project concerning monitoring and stability analysis of a 40 m high phosphogypsum heap located at Wiślinka, Poland. The research presented in the paper focused on collecting and processing rainfall data, which subsequently allows us to perform numerical simulation of rainfall impact on heap’s behaviour. Such analysis requires time history of rainfall intensity, that is recorded by an automatic precipitation station. Since this is not common monitoring equipment, the characteristics of the station installed in the immediate vicinity of the heap are presented, and the data obtained in two experiments conducted in the laboratory are discussed. The analysis revealed that di erences between introduced and measured total rain are as large as 10% for very heavy rains. Moreover, the recorded maximum rainfall intensity often includes errors. The data processing procedure to obtain time history of rainfall intensity is presented on the basis of data collected in the first half of the hydrological year 2023 (the first period of the station’s operation). The total precipitation registered was 107 mm, and the maximum daily rain was only 26 mm. However, first single and multi-stage rainfall models for the Wiślinka region that would be applied into numerical simulations are presented.

Abstract The waste warm waters from power plants, owing to their temperature regime (25–38°C) and the volumes of discharge, allow for their use for heating of open ground areas in agriculture. Underground heating by such water is a new, special heat and irrigation method which enables not only purposeful regulation of temperature conditions of the crop growing environment, but also dissipates heat in the soil, thus cooling the water for its reuse. This makes it possible to reduce the thermal pollution of water sources.

Abstract Bankfull discharge is an important criterion for flash flood warnings. In this study, the authors propose a new approach to determine the bankfull discharge for basins in Ha Giang province, Vietnam. The study combines the field survey to determine the bankfull discharge through the bankfull indicators and develop a multivariate regression equation between the bankfull discharge and the basin characteristics. The results of the study give a simple equation with 2 independent variables. They are the catchment area and the main river length. They show a strong relationship with the bankfull discharge with the R 2 indexes in developing and validating process equal to 95.3% and 92.7%, respectively. With this approach, the workload is significantly reduced. However, the accuracy and flexibility of the total discharge calculation are enhanced. This will be the foundation to reduce uncertainty in flash flood warnings.

Abstract Since accurate estimation of the flow kinetic energy ( α ) and momentum ( β ) is not easily possible in compound channels, determining their accurate correction coefficients is an important task. This paper has used the “flood channel facility (FCF)” data and the “conveyance estimate system (CES)” model (which is 1D, but considers a term related to the secondary flow) to study how the floodplain width and the main channel wall slope and asymmetry affect the values of α and β . Results have shown that their maximum values at the highest floodplain width are, respectively, 1.36 and 1.13 times of those at the lowest case; an increase in the slope increased their maximum values by 1.05 and 1.01 times, respectively. The mean of error values showed that the CES model estimated the values α and β more accurately than the flow discharge. The maximum differences between the estimated and experimental values were 12.14% for α and 4.3% for β ; for the flow discharge, it was 24.4%.

Abstract The paper presents a 3D (spatial) analysis of deformation processes in the landslide slope Bystrzyca in Szymbark near Gorlice (Low Beskid – Carpathians; N 49°37′ 09″, E 21°05′ 49″) carried out by the computer code FLAC3D based on the finite difference method. The numerical analysis was performed to determine the influence of the orientation of layers and discontinuities and of hydrogeological conditions on slope deformations and the failure mechanism during sliding processes. The massif is modeled as an elasto-plastic medium obeying the Coulomb-Mohr criterion. Two variants of hydrogeological conditions are analyzed, namely the “dry slope” (without water) and the “wet slope” (entirely saturated). The influence of the orientation of discontinuities (modeled as “ubiquitous”) on the landslide mechanism is investigated as well. Few orientations of discontinuities with respect to the dip direction of the slope surface are considered, namely consequent, insequent, and subsequent (two variants in each case). The results show a clear impact of the pattern of discontinuities and hydrogeological conditions on the deformational behavior of the landslide and the shape of the slip surface. The 3D approach and results of the numerical simulation of the landslide movement prove the necessity of 3D modeling in some cases.

Abstract The paper discusses difficulties of identifying the causes of a landslide. These difficulties are illustrated in the example of a catastrophic landslide on the embankment of the western bank of the Brda River, which affected a bridge abutment of a disused narrow-gauge railway line from Bydgoszcz to Koronowo (Polish Lowlands). The railway was closed in 1992, and after the removal of the track, the bridge served as a pedestrian overpass. The landslide occurred in February 2011. Investigations revealed that the first signs of the landslide were cracks and subsidence that appeared at the embankment crest. Then, an initially slow movement accelerated suddenly, resulting in an over 45 m total displacement of the soil mass. The primary passive cause of the landslide movement resulted from the geology of the mass (loose soils underlain by cohesive soils) and from the steep inclination of the embankment surface. Active causes, however, are often ambiguous. In this case, no significant apparent phenomena which could trigger the movement occurred in the days preceding its initiation. Therefore, a detailed analysis of atmospheric conditions was carried out to identify and explain the causes. It was proved that the fundamental triggering cause of the landslide was a combination of rainfall, snowfall, snow-melting and air temperature. Moreover, an important cause was a faulty construction of a ditch with a sewage pipe on the crest of the embankment.

Abstract The paper presents recent investigations of beach run-up phenomena at the Coastal Research Station of the Institute of Hydro-Engineering of the Polish Academy of Sciences at Lubiatowo, Poland. The local beach is typical of open-sea coasts of the south Baltic Sea, featuring multiple longshore bars that form predominantly dissipative systems. Measurements were taken to verify the existing formulas for the run-up height, bearing in mind that they had been derived for entirely different, oceanic conditions. The results indicate that these formulations can be adapted to south Baltic Sea conditions. This however, will require significantly larger data sets, which we intend to obtain in the near future.

Abstract This paper presents the results of a numerical simulation of a slope deformation process. The landslide slope “Grabina” in Koronowo near Bydgoszcz (Poland) serves as an example. A slope profile located in the central part of the slope, between the main scarp and the toe of the landslide, was selected. The average dip of the slope is about 10, and its length is approximately 55 m. Elasticity, plasticity and viscosity properties were taken into account in the model of the soil mass that composes the slope. The visco-elastic properties are described by the Burgers model (Mainardi and Spada 2011), and the plastic ones by the Coulomb-Mohr law. A numerical simulation was carried out by the computer code FLAC2D in the plane strain state with the assumption of the Lagrange routine. The model was discretized taking into account the results of inclinometric measurements, which proved that the slide movement was concentrated in a narrow loam zone of 0.5–1.0 m thickness. No tests of the viscosity parameters were performed, so they were determined by the back analysis and a trial and error method. The calculation results were verified by comparison with the displacement measured by the inclinometric method in three boreholes. The analysis performed demonstrated the possibility of approximating and forecasting landslide displacements by the combined Burgers and Coulomb-Mohr models.

Abstract The flow field of many practical open channel flow problems, e.g. flow over natural bed forms or hydraulic structures, is characterised by curved streamlines that result in a non-hydrostatic pressure distribution. The essential vertical details of such a flow field need to be accounted for, so as to be able to treat the complex transition between hydrostatic and non-hydrostatic flow regimes. Apparently, the shallow-water equations, which assume a mild longitudinal slope and negligible vertical acceleration, are inappropriate to analyse these types of problems. Besides, most of the current Boussinesq-type models do not consider the effects of turbulence. A novel approach, stemming from the vertical integration of the Reynolds-averaged Navier-Stokes equations, is applied herein to develop a non-hydrostatic model which includes terms accounting for the effective stresses arising from the turbulent characteristics of the flow. The feasibility of the proposed model is examined by simulating flow situations that involve non-hydrostatic pressure and/or nonuniform velocity distributions. The computational results for free-surface and bed pressure profiles exhibit good correlations with experimental data, demonstrating that the present model is capable of simulating the salient features of free-surface flows over sharply-curved overflow structures and rigid-bed dunes.

Abstract The paper deals with research uncertainties, difficulties, inaccuracies and unreliabilities related to the modelling of physical phenomena involving coastal lithodynamics. The considerations are focused on processes of wave transformation, wave-driven currents and sediment transport itself. It is shown that possible inaccuracies at individual stages of the modelling of coastal hydrodynamics can lead to serious uncertainties with respect to the ultimate modelling output, namely bed shear stresses and sediment transport rates. These inaccuracies result mostly from arbitrarily assumed parameters and constants. Other modelling biases discussed in the paper comprise simplifications and approximations with respect to sediment resources and size-graded properties, randomness of hydrodynamic impacts, bottom roughness and land-borne factors involved in coastal lithodynamics.