River oil spills are generally more frequent and pose greater environmental and public health risk than coastal and offshore oil spills. However, the river oil spill research has received a negligible amount of academic attention in the past three decades, while at the same time the coastal and offshore oil spill research has expanded and evolved tremendously. This paper provides the state-of-the-art review of river oil spill modeling and summarizes the developments in the field from 1994 to present. The review has revealed that the majority of the gaps in knowledge still remain. Thus, there is a need for (i) experimental studies in order to develop and validate new models and better understand the main physicochemical processes, (ii) studies on inter-linking of the governing processes, such as hydrodynamics, advection–dispersion, and weathering processes, (iii) adaptation and validation of coastal and offshore oil spill models for applications in riverine environments, and (iv) development of river oil spill remote sensing systems and detection techniques. Finally, there is a need to more actively promote the importance of river oil spill research and modeling in the context of environmental and public health protection, which would form the basis for obtaining more research funding and thus more academic attention.

Fishways have a great ecological importance as they help mitigate the interruptions of fish migration routes. In the present work, the novel DualSPHysics v4.4 solver, based on the smoothed particle hydrodynamics method (SPH), has been applied to perform three-dimensional (3-D) simulations of water flow in a vertical slot fishway (VSF). The model has been successfully calibrated against published field data of flow velocities that were measured with acoustic Doppler velocity probes. A state-of-the-art algorithm for the treatment of open boundary conditions using buffer layers has been applied to accurately reproduce discharges, water elevations, and average velocity profiles (longitudinal and transverse velocities) within the observed pool of the VSF. Results herein indicate that DualSPHysics can be an accurate tool for modeling turbulent subcritical free surface flows similar to those that occur in VSF. A novel relation between the number of fluid particles and the artificial viscosity coefficient has been formulated with a simple logarithmic fit.

Worldwide, the overwhelming number of man-made barriers in fluvial systems has been identified as one of the major causes of the reported staggering average declines of migratory fish. Fish passages have been shown to help mitigate such problems. Close-to-nature types of fish passages, such as bottom ramps, bypass channels, and fish ramps can be used to minimize the impact of artificial steep drops (e.g., weirs) on the migration of aquatic fauna, especially in cases of low-head barriers. This study focuses on the characterization of the flow pattern in a bottom ramp. A 3-D numerical model based on the meshless smoothed particle hydrodynamics (SPH) method was successfully validated and then employed for the simulation of turbulent free-surface flow in a straight channel with complex geometry. The effects of bed roughness, channel slope, and flow rate were quantified in terms of flow depth, velocity fields, and area‒velocity ratios. During the study, several new tools were developed, leading to new functionalities in pre-processing, solver, and post-processing which increase the applicability of DualSPHysics in the field of eco-hydraulics.