Movable Weir

Water Level Sensor Map

The HVUSSS is Hong Kong's first flood storage tank provided with a “Movable Crest Weir” that works in connection with a "Supervisory Control and Data Acquisition" (SCADA) system. This design effectively lowers construction cost and time, as well as operation power consumption, addressing flood prevention and environmental initiatives in tandem.

Design and Operation:

Through the SCADA system, the positioning of the movable weir is controlled based on the real-time tidal level and water levels inside the tank, and upstream and downstream of it in the box culvert. This allows overflowing of stormwater from the box culvert to the tank to be invoked at the most optimal time.

Compared to the conventional fixed-weir design, the real-time SCADA-controlled movable weir prevents pre-mature or belated filling of the tank, thereby maximizing the effectiveness of the storage capacity and allowing a smaller design tank volume.

Furthermore the tanks is of a shallow-depth design. After heavy rain, as water level in the downstream box culvert subsides, the movable weir can be lowered further to allow about one-third of the stored stormwater to be discharged by gravity back to the box culvert, reducing the need for pumping.