Following Hurricane Rita in September 2005, which caused the Lorette River to flood the Wilfrid-Hamel Boulevard area, the City of Quebec selected Tetra Tech to develop the Lorette River Catch Basin Drainage Master Plan. Tetra Tech carried out the design and implementation of a real-time control (RTC) solution for flooding mitigation in this area.

Tetra Tech provided the City of Quebec various flood protection solutions to decrease flood occurrences and hydraulic restrictions in the sewer, the storm network, and the Lorette River banks for existing and future conditions.

The City of Quebec opted for a RTC solution to regulate flooding conditions for a centennial storm event. The flood protection solution involves constructing two 26 million gallon (100,000 m3) retention basins along the two main tributary creeks—Des Friches and Mont-Châtel. It also includes new pumping stations and control of storage location gates to secure hydraulic levels in the downstream urban sectors of the Lorette River.

Tetra Tech’s incorporation of RTC ensures effective operation of the flood protection works and significantly decreases construction costs by reducing the size of the retention basins compared to a static control method.

The designed RTC system provides continuous rainfall and hydraulic forecasts, based on real-time hydraulic model simulations, forecasted more than 12 hours in the future. The decision-making system provides control actions that are triggered at the right time to ensure the rainfall/hydraulic peak response is caught in storage, and thereby preventing sensitive areas from flooding.

Tetra Tech provides these forecasts in a comprehensive chart tool for the benefit of system operators and the City’s administrative and emergency staff. The RTC system’s first storage basin has been in operation since the spring of 2013. A second storage basin was integrated into the system in July 2015.