The stream has a complicated history. Originally it was an agricultural drain for draining the fields and could flow in each direction, the northern outlet is known as the Washington Outfall and is marked by Trinity House. As the town developed, the fields disappeared and the drain became, by default, a surface water drainage ditch with various surface water sewers discharging into it.
After the War, development of Tre Creuddyn estate meant sections needed to be culverted. At some stage, the UDC asked the Gwynedd River Board to "adopt" ditch as a scheduled "main river". This meant that grants became available for the culverting.
As a "main river" it was given a name = The Afon Creuddyn - and maintenance of the outfalls was the responsibility. The final bit of culverting was around 1970/71 and involved works under the railway near the signal box.
In 1974 the sewerage undertaking (UDC) and the Afon Creuddyn were vested in one body, the Welsh National Water Development Authority. As the Afon Creuddyn was by now in effect a trunk surface water sewer with no land drainage component, Welsh Water decided to "demain" the Creuddyn and simultaneously adopt it as a public surface water sewer.
Nowadays the flow is intercepted at West Shore and pumped to Sarn y Mynach for treatment along with the foul flows. The old outfall at West Shore is used as an emergency overflow and subject to consent by NRW.
A section beyond the Links towards Craig y Don was significantly altered when Clarence Cresecent was built in the 1980s but a diverted open section is hidden in the bushes fronting Cae Clyd. A tank in the undergrowth at the entrance to Cae Clyd seems to mark a junction between the Afon Creuddyn and the Washington system.