Environmental Hydraulics in the New Millennium: Historical Evolution and Recent Research Trends

Environmental Hydraulics (EH) is the scientific study of environmental water flows and their related transport and transformation processes in natural water systems. This review provides some remarks about the historical development of EH throughout three different paradigms or ages, namely, the Public Health Age, the Water Quality Age, and finally the Integrated Environmental Hydraulics Age. We further evaluate how EH research has changed in the last 20 years through a bibliometric analysis of the proceedings of the International Symposium on Environmental Hydraulics (ISEH) and Environmental Fluid Mechanics (EFMC) journal articles conducted using Citespace and Leximancer. Authors and affiliations are analyzed to identify patterns of collaboration, followed by an analysis of the temporal evolution of the EFMC impact index as well as its highly-cited articles. Finally, the major EH topics are identified with a comparison between the topics extracted from the two different sources. As the EH field is becoming rapidly global, some topics were confirmed to have attracted more interest in EH such as Flow Condition, Numerical Modelling, Experimental Measurements. It is hoped that our findings could provide a reference for students, academics, and policy-makers related to EH.

Natural Fluvial Ecohydraulics

Ecohydraulics is the study of the mechanisms that explain hierarchically nested aquatic and riparian biotic phenomena. Mechanisms are sequential actions that can be physical, biological, or an interaction between the two. Biotic phenomena consist of individual, population, and community-level conditions, behaviors, and interactions. Hierarchical nesting means that phenomena are present across a wide range of spatial scales: from the smallest fluid continuum scale to the scale of the entire Earth. Many ecohydraulic studies prominently address scaling. Under this definitional framework and given the widespread occurrence of water on Earth, ecohydraulics is the “proximal” science mediating the influence of “distal” landscape drivers (e.g., climate, geology, and topography). Historically, scientists discovered empirical correlations relating biotic conditions to both proximal and distal abiotic variables. However, when such results are applied to practical societal problems (e.g., stream barrier passage, habitat rehabilitation, and flow regime specification), the accuracy and specificity is insufficient to solve them. That has led to widespread recognition of the need for a mechanistic understanding culminating in predictive numerical models. Driven by such necessity, physical and biological scientists and engineers have formed multidisciplinary teams to work out how water and biota interact. Through its marriage of conceptual understanding with quantitative analysis, ecohydraulics is playing a central role in methodological advancements to objectively, transparently, and repeatably explain biotic phenomena at multiple spatial scales. Students involved in ecohydraulics are part of an emerging interdisciplinary generation identifying more with problem-oriented applied science that responds to societal needs to solve specific ecological problems than disciplinarians driven by curiosity and traditional socio-scientific pathways. Nevertheless, it goes too far to conclude that ecohydraulics is nothing more than the application of other sciences, with no basic developments of its own. Necessity often motivates ecohydraulicists to undertake novel experiments revealing fundamental discoveries. As a result, a reasonable distinction can be made between basic ecohydraulics for studying natural phenomena and applied ecohydraulics for rehabilitating degraded phenomena. This annotated bibliography is the first of two spanning ecohydraulics, and it tackles the former, while the second addresses the latter. Due to space limitations, this article is narrowed to natural fluvial ecohydraulics. Within this domain, there are five essential topics: environmental fluid mechanics, flora ecohydraulics, fluvial habitat, faunal ecohydraulics, and fish migration. Finally, space limitations further limit the scope to an emphasis on observational studies over numerical modeling.