English: Lower Lock Gate, Howard Lock, Floating Harbour, Bristol This lower lock gate separates the Floating Harbour from the tidal River Avon. The Avon is on the right the floating harbour on the left.

The floating harbour was built in 1809 to ensure that boats loading and unloading in Bristol's harbour could remain floating at all times. Previously the huge tidal range of the river at this point meant that boats were beached on the mud at low tide. The floating harbour occupies the section of the river Avon that used to flow through the centre of the city, from Temple Meads station down to this point. Because of this lock it now has a constant water level. The tidal Avon now flows through a new channel called New Cut which runs from the Howard Lock upstream to Temple Meads. The water level on the tidal river can vary by as much as 40ft. The New Cut is in the left rear of this image. A feeder canal was cut from Temple Meads upstream to Netham Lock on the Avon to supply the floating harbour with water. Most of the boats using the lock to pass from the river to the floating harbour are now small leisure craft but the lock itself is huge and was designed to take large sailing ships. A problem soon arose after construction from the silting up of the floating harbour which is also fed by the River Frome which also flows through the city centre but is contained in a culvert and is not visible below the bridge at Wade St.

Brunel designed the Underfall sluices which were designed to produce a scouring action to remove silt from the harbour into the New Cut of the Avon. This was partially successful but the harbour still had to be dredged regularly and the dredging continues to this day.