River Severn - Afon Hafren

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Afon Hafren

The River Severn/Afon Hafren, the longest river in Great Britain emerges at around 2000ft(610m) on the slopes of Plynlimon, Wales and flows for 220 miles (345km) eventually discharging into the Bristol Channel.

Source

The summit of Plynlimon has an annual rainfall of around eight feet (2400mm). This runs off the peat which overlies the Paleozoic shales, grits and mudstones. The extent of forestation has reduced in recent years by felling.

Hafren Forest to Llanidloes

The river drops rapidly through the forestry dropping to almost one half of its starting height by the time it reaches a measuring flume near to the public car park at 331m AOD. The mean flow in the river is 0.5m3/s or 6000 gallons/minute.






Pennygreen or 'The Colonel's' footbridge dates from 1975 and was named after Colonel Davies-Jenkins.



The Short Bridge at Llanidloes is a Thomas Penson design dating from 1849.



At Llanidloes the river is joined by the Afon Clywedog.



The Long Bridge designed by County Surveyor Thomas Penson dates from 1826 replacing an earlier timber bridge.



The river has dropped a further 173m to 158m AOD at the measuring station at Llanidloes. It is still a largely natural upland catchment as the river flows within boulder clay and fluvial gravel overlying Paleozoic shales. The river flows in the summer are influenced by releases from the Clywedog Reservoir.

Llanidloes to Newtown

A timber bridge survives from the 1859 Newtown to Llanidloes railway which closed in 1960.



The reinforced concrete Dolwen Bridge dates from 1926. Its low soffit can result in flooding during heavy rainfall.



Llandinam Bridge is a Grade II listed structure designed by Thomas Penson and built by David Davies in 1846. The cast iron river span is 90 feet (27.5m). Thomas Penson also designed the Caerhowel bridge a few years later.





The Roman fort at Caersws is sited at the ancient crossing point of the upper River Severn at the confluence with the Afon Cerist.







The three arch bridge opened in 1821 was built to a design by Thomas Penson.



The Festival footbridge at Aberhafesp was erected in 1951 at the time of the Festival of Britain.



The Cambrian Line between Newtown and Machynllyth crosses and recrosses a loop in the river.



Newtown is a major settlement on the river built in the late thirteenth century on the instructions of Edward I by the Mortimers as a new town at the ford downstream of the current Long Bridge.



The Dolerw Park Footbridge is a suspension bridge dating from 1973 was designed by Consulting Engineers Mott, Hay and Anderson. They were perhaps better known as designers of the Severn, Forth and Tamar bridges.



The Long bridge is a Thomas Penson design from 1827 and was widened in 1857.



The current Halfpenny Footbridge dates from 1972 and is the fourth bridge on this site since 1830.



The Bypass Bridge opened in 1993 taking traffic away from the town centre.



The pump house provided water to top up levels in the Montgomery Canal. The canal linked to the Shropshire Union Canal. The Severn Way, long distance footpath, follows the canal towpath to Welshpool.

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