The distribution of archaeological finds suggests that the western end of the river between Bath and Avonmouth formed a border between the Dobunni and Durotriges during the late Iron Age, prior to the Roman conquest of Britain.
Further east, between Bath and what is now Wiltshire, it may also have formed a border of the territory ruled by the Belgae.
After the Roman occupation the river formed a boundary between the lands of the Hwicce (which became Mercia) and the kingdom of Wessex.

The river Avon had been navigable from Bristol to Bath during the early years of the 13th century but construction of mills on the river forced its closure.
The floodplain of the Avon, on which the city centre of Bath is built, has an altitude of about 59 ft (18 m) above sea level.
The river, once an unnavigable series of braided streams broken up by swamps and ponds, has been managed by weirs into a single channel.
Periodic flooding, which shortened the life of many buildings in the lowest part of the city, was normal until major flood control works were completed in the 1970s.

The Bristol Avon Navigation, which runs the 15 miles (24 km) from the Kennet and Avon Canal at Hanham Lock to the Bristol Channel at Avonmouth, was constructed between 1724 and 1727, following legislation passed by Queen Anne, by a company of proprietors and the engineer John Hore of Newbury.
The first cargo of 'Deal boards, Pig-Lead and Meal' arrived in Bath in December 1727.
It is now administered by the Canal & River Trust.

Throughout Bristol's history the Avon Gorge has been an important transport route, carrying the River Avon, major roads and two railways.
The Bristol Channel has a very high tidal range of 15 metres (49 ft), second only to Bay of Fundy in Eastern Canada; and the gorge is relatively narrow and meandering, making it notoriously difficult to navigate.
Several vessels have grounded in the gorge including the SS Demerara soon after her launch in 1851, the schooner Gipsy in 1878, the steam tug Black Eagle in 1861 and the Llandaff City.

In 1877, Halfpenny Bridge, a pedestrian toll bridge, crossing the river from Bath Spa railway station to Widcombe collapsed with the loss of about 10 lives amongst a large crowd going to the Bath and West Agricultural show.

The Avon has flooded several times in its recorded history.
These floods include the one in 1799/1800 damaging Pulteney Bridge.
Various points along the river including the valley around Freshford are at risk of fluvial flooding, as a result of sediment entering the river and narrowing the channel.
To help cope with this some areas on the banks of the river are designated as a functional floodplain to cope with increased flow volumes.
The potential  changes to weather patterns as a result of climate change suggest that further measures are likely to be needed to protect the population from flooding risk.
A tidal surge, combined with high water levels from the flooding of the surrounding area caused flooding in the city of Bristol.
The distribution of archaeological finds suggests that the western end of the river between Bath and Avonmouth formed a border between the Dobunni and Durotriges during the late Iron Age, prior to the Roman conquest of Britain. Further east, between Bath and what is now Wiltshire, it may also have formed a border of the territory ruled by the Belgae. After the Roman occupation the river formed a boundary between the lands of the Hwicce (which became Mercia) and the kingdom of Wessex.
The river Avon had been navigable from Bristol to Bath during the early years of the 13th century but construction of mills on the river forced its closure. The floodplain of the Avon, on which the city centre of Bath is built, has an altitude of about 59 ft (18 m) above sea level. The river, once an unnavigable series of braided streams broken up by swamps and ponds, has been managed by weirs into a single channel. Periodic flooding, which shortened the life of many buildings in the lowest part of the city, was normal until major flood control works were completed in the 1970s.
The Bristol Avon Navigation, which runs the 15 miles (24 km) from the Kennet and Avon Canal at Hanham Lock to the Bristol Channel at Avonmouth, was constructed between 1724 and 1727, following legislation passed by Queen Anne, by a company of proprietors and the engineer John Hore of Newbury. The first cargo of 'Deal boards, Pig-Lead and Meal' arrived in Bath in December 1727. It is now administered by the Canal & River Trust.
Throughout Bristol's history the Avon Gorge has been an important transport route, carrying the River Avon, major roads and two railways. The Bristol Channel has a very high tidal range of 15 metres (49 ft), second only to Bay of Fundy in Eastern Canada; and the gorge is relatively narrow and meandering, making it notoriously difficult to navigate. Several vessels have grounded in the gorge including the SS Demerara soon after her launch in 1851, the schooner Gipsy in 1878, the steam tug Black Eagle in 1861 and the Llandaff City.
In 1877, Halfpenny Bridge, a pedestrian toll bridge, crossing the river from Bath Spa railway station to Widcombe collapsed with the loss of about 10 lives amongst a large crowd going to the Bath and West Agricultural show.
The Avon has flooded several times in its recorded history. These floods include the one in 1799/1800 damaging Pulteney Bridge. Various points along the river including the valley around Freshford are at risk of fluvial flooding, as a result of sediment entering the river and narrowing the channel. To help cope with this some areas on the banks of the river are designated as a functional floodplain to cope with increased flow volumes. The potential  changes to weather patterns as a result of climate change suggest that further measures are likely to be needed to protect the population from flooding risk. A tidal surge, combined with high water levels from the flooding of the surrounding area caused flooding in the city of Bristol.
River Avon, Bristol