Vision on hydraulic engineering and environmental hydromechanics

In the past, hydraulic engineering mainly concerned flowing water and the (largely) empirical design and construction of structures to control it. Interactions of flowing water with sediment transport and ecological processes were largely omitted. Rivers were trained to improve navigation, reclaim fertile land in the flood plain, or mitigate flooding hazards. Dams and reservoirs were built to generate hydropower, reduce flood risks, or provide drinking and irrigation waters. Hydraulic engineering projects often perturbed the long-term morphodynamic equilibrium, leading to erosion or aggradation, with potentially devastating effects on flood hazards or navigation. Moreover, hydraulic engineering projects mostly led to a homogenization of discharge, velocities, substrate and morphology, with adverse impacts on the ecosystem.

“Hydraulic engineering and environmental hydromechanics” have evolved into science-based interdisciplinary fields at the interface of civil engineering, hydraulics, fluid mechanics, sediment transport, geomorphology, biology and chemistry (Fig. 1). Nowadays, hydraulic engineering and environmental hydromechanics concern the conciliation of multiple objectives: hazard mitigation (flooding, drought, pollution), the development of socio-economic functions (hydropower generation, navigation, irrigation) and the conservation or restoration of ecological functions. In a sloganized way, one could say that hydraulic engineering has evolved from building hydraulic structures to control the water, to building with nature by subtly influencing processes where flowing water, sediment and biota meet (Fig. 1). In developed countries, the focus has shifted from designing and building new structures to optimizing the design, operation and maintenance of existing ones, as well as mitigating adverse effects of existing ones.

Fig.1 Schematical presentation of the vision on hydraulic engineering and environmental hydromechanics and its main pillars

The societal relevance of this interdisciplinary and multi-objective approach in hydraulic engineering is highlighted in recent policy frameworks such as the EU Water Framework Directive and the UN Sustainable Development Goals. These policy frameworks highlight in particular the importance of the conservation or restoration of ecological functions. This interdisciplinary and multi-objective approach in hydraulic engineering and environmental hydromechanics is also scientifically relevant. Engineering tools are often characterized by uncomfortably high uncertainties, which can largely be attributed to a lack of understanding of processes at the interface of different disciplines.

This vision on hydraulic engineering and environmental hydromechanics is at the basis of our research and teaching activities.