Designing New Hydraulics Works Based on Existing Real-World Constraints: How to Make Sure to Be Efficient and Reliable

Designing new hydraulics works / networks is today very common. A lot of tools are now existing in order to find the appropriate dimensions based on given flows and downstream conditions. However, a lot of problems still happens because some real-world specific local constraints are not “correctly” taken into account through this designing process.

Two typical contexts are regularly encountered: (i) the design of a new road based on an existing path where existing culverts are already existing; (ii) the design of a new storm water network, near the existing “old” combined network that is becoming the sewer water network. In both cases the existing conditions are essential and cannot be ignored to guarantee the success of the projects.

Two projects were developed and are here presented to illustrate how it is now possible to take into account more efficiently specific local constraints that can have significant impacts on the future project feasibility. New 3D rendering tool can make a great difference in the analysis and decisions efficiency.

For the first project, a new road has to be implemented on around 1.5 km closed to Ajaccio city in Corsica, the French island in the Mediterranean Sea. The new road being located in the flooding area of a “small” river upstream to the city, one of the biggest questions was, can we keep the existing culverts along the initial pathway? We will see that understanding the culvert locations and on site behaviors within the future project is a key to make the “correct” choices to avoid increasing the floods in the area.

For the second project, a new storm sewer network has to be designed at Saint Jean de Richelieu City in Quebec, Canada, in parallel to the existing combined network that will become a unique wastewater network. The biggest question in that case was, how can we optimize the design step while taking into account spatial conflicts with the existing network? It has to be noted that in this case, no change can be done on the current network because of the multiple existing connections. So, if the new design storm network is in conflict with the waste water network, its design has to be done again until both the performance and the spatial aspects are satisfactory. A lot of time can then be spent to find the optimal solution through a trial-and-error process.

In both cases, developing a 1D-2D model along with a combined 3D rendering was essential for the engineers and the stakeholders teams to be able to choose the more relevant design based on real local constraints in order to make the best financial and technical decisions for the collectivity