the weir can be navigated by crossing over the top during high spring tides. on the city-side of the weir is the united kingdom's only example of a weirgate, a low height single lock gate that can be opened to provide extra draft once the water levels on each side of the weir have equalised. this allows carefully planned passage from the non-tidal river dee, via the short tidal estuary section, onto the dee branch of the shropshire union canal (originally the chester canal) at certain times of year.