The Swift Ditch

The Swift Ditch (old channel, only just canoeable - with weirs) outflows into the Thames at the top of Culham Reach.
There is a wooden towpath bridge , and then beyond it a pool below the old Bridge.
Beyond that the Swift Ditch is crossed by the modern replacement for the old Bridge, carrying the A415 This is the downstream end of what was the main navigation stream. Notice the 1820 quotation for Abingdon Bridge in which what is now the main stream was referred to as 'the new cut'. (New, that is, in the ninth century!)
I notice some understandable confusion as to which is the old river and which is the new cut - the new cut goes under Abingdon Bridge to the Abingdon Lock. The old river course is what we now call the Swift Ditch.

Culham Old Bridge was possibly at one time the most important bridge at Abingdon.
A civil war skirmish was fought on this old Culham Bridge. The Royalists unsuccessfully tried to attack the Roundheads in Abingdon.
1645 -

Colonel Sir Henry Gage was mortally wounded attempting to destroy Culham Bridge and establish a fort against Abingdon; he is replaced as Governor of Oxford by William Legge.

1848: Thought to be the Swift Ditch -
from "Pleasant Spots around Oxford" by Alfred Rimmer -

A channel of the Thames near Abingdon, 1848
from Pleasant Spots around Oxford by Alfred Rimmer

1929: A Thames Survey -

Culham Bridges. The old bridge was built in 1416 by the Guild of the Brotherhood of Christ, who erected Abingdon Bridge: it is of stone with medieval arches, 23 feet wide between parapets, including one side-walk 3 feet 3 inches wide.
Owing to its age and condition it is now only open to pedestrians and all other traffic has been diverted to the New Bridge, built 1927-8, which is of stone, well designed, having one large elliptical arch spanning the stream and two side semi-circular arches. The roadway and new approaches are of generous width with two side-walks. Headway above normal water-level, 15 feet 6 inches.
Tolls are payable at the toll-house on the Berkshire side.

1963: Culham old Bridge,the Burycroft listed as of special historic or architectural interest -

CULHAM THE BURYCROFT SU5095 (West side) 10/35 Culham Old Bridge 18/07/63
Bridge. c.1416, built by the Abingdon Guild of the Holy Cross, widened and north side rebuilt C18.
Parapet restored mid C20. Squared uncoursed stone.
Five 4-centred arches of varying heights. Plain parapet.
North side has 5 round arches.
History:
during the Civil War, in May 1644 the parliamentarians seized the bridge and attacked royalist convoys to Oxford.
This led to an unsuccessful royalist attempt to recapture and demolish the bridge (the Battle of Culham Bridge, January l645).
Scheduled Ancient Monument. (V.C.H.: Oxfordshire, Vol.7, 1962, p.27 and p.31).