Hydraulic Impact Study of a Diversion Weir

Overview

Expanding urban water supply often requires the construction of new diversion structures on mountain streams. These works modify the flow regime and can affect upstream inundation areas and downstream hydraulic conditions. Anticipating such impacts is critical for ensuring both the reliability of water supply and the safety of the surrounding environment.

The Challenge

The planned diversion weir raised questions about how flood events of different magnitudes would alter water levels, inundation extents, and flow regimes in the affected reach. A combined hydrological and hydraulic modeling approach was required to provide robust predictions.

Our Contribution

HCS carried out an integrated hydrological and hydraulic study to quantify the impacts of the proposed structure. Hydrological modeling with long-term rainfall and flow records established design discharges for return periods up to 500 years. A detailed two-dimensional hydraulic model was then implemented to simulate the river both in natural conditions and with the weir in place. The results showed how the structure modifies inundation patterns, backwater effects, and flow regimes, particularly under extreme scenarios. The study provided essential technical input to validate the design and to support decision-making on flood safety and environmental compatibility.