View source for River Taff

{{Short description|River in Wales which flows into Cardiff Bay}}
{{distinguish|River Taf}}
{{Use dmy dates|date=April 2022}}
{{Infobox river
| name               = River Taff
| native_name        ={{native name|cy|Afon Taf}}
<!---------------------- IMAGE & MAP -->
| image              = River_Taff_-_geograph.org.uk_-_1530156.jpg
| image_size         = 250
| image_caption      = The Taff flowing through [[Llandaff]]
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<!---------------------- LOCATION -->
| subdivision_type1  = Country
| subdivision_name1  = [[Wales]]
| subdivision_type2  = Historic county
| subdivision_name2  = [[Glamorgan]]
| subdivision_type3  = 
| subdivision_name3  = 
| subdivision_type4  = Unitary Authority
| subdivision_name4  = [[Merthyr Tydfil]], [[Rhondda Cynon Taf]], [[Cardiff]]
| subdivision_type5  = Settlements
| subdivision_name5  = [[Merthyr Tydfil]], [[Treharris]], [[Pontypridd]], [[Cardiff]]
<!---------------------- PHYSICAL CHARACTERISTICS -->
| length_km = 67
| length_ref = <ref>{{cite journal |last1=Pickup |first1=R. W. |last2=Rhodes |first2=G. |last3=Arnott |first3=S. |last4=Sidi-Boumedine |first4=K. |last5=Bull |first5=T. J. |last6=Weightman |first6=A. |last7=Hurley |first7=M. |last8=Hermon-Taylor |first8=J. |title=Mycobacterium avium subsp. paratuberculosis in the Catchment Area and Water of the River Taff in South Wales, United Kingdom, and Its Potential Relationship to Clustering of Crohn's Disease Cases in the City of Cardiff |journal=Applied and Environmental Microbiology |date=April 2005 |volume=71 |issue=4 |pages=2133 |doi=10.1128/AEM.71.4.2130-2139.2005 |pmid=15812047 |pmc=1082532 |bibcode=2005ApEnM..71.2130P |quote=The longest path length of the river Taff uninterrupted by inflows is 67 km|doi-access=free }}</ref>
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| discharge1_location= 
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| discharge2_location= [[Cardiff Bay]]
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<!---------------------- BASIN FEATURES -->
| source1            = Taf Fawr
| source1_location   = [[Corn Du]], [[Brecon Beacons]], [[Powys]], [[Wales]]
| source1_coordinates= 
| source1_elevation  = 
| source2            = Taf Fechan
| source2_location   = [[Pen y Fan]], [[Brecon Beacons]], [[Powys]], [[Wales]]
| source2_coordinates= 
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| mouth              = [[Cardiff Bay]]
| mouth_location     = [[Cardiff]], [[Wales]]
| mouth_coordinates  = 
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| progression        = 
| river_system       = 
| basin_size         = 
| tributaries_left   = Bargoed Taf
| tributaries_right  = [[River Cynon|Cynon]], [[River Rhondda|Rhondda]]
| custom_label       = 
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}}
[[Image:River Taff.jpg|thumb|right|{{center|Part of the River Taff, running through Cardiff}}]]
[[Image:River Taff Weir and Footbridge.jpg|right|thumb|A [[weir]] and footbridge (Blackweir Bridge) over the River Taff (Cardiff)]]

The '''River Taff''' ({{langx|cy|Afon Taf}}) is a river in [[Wales]]. It rises in the [[Brecon Beacons]] as two rivers, the Taf Fechan ("little Taff") and the Taf Fawr ("great Taff") before becoming one just north of [[Merthyr Tydfil]]. At [[Cardiff]], it empties into the [[Bristol Channel]].

The river supports several species of [[migratory fish]], including [[salmon]], [[sewin]]s (sea trout), and [[eel]]s.

==Course==
From its confluence at Cefn-coed-y-cymmer, the river flows south, passing several towns. It picks up a few tributaries, such as the [[River Cynon]], [[River Rhondda]], [[Taff Bargoed|Bargoed Taf]] and [[Nant Clydach]]. It flows through Pontypridd and through to [[Taff's Well]], the site of Wales' only thermal spring.  It flows underneath the [[M4 Motorway]], before turning southeastward and flowing past the Cardiff suburbs of [[Radyr]], [[Whitchurch, Cardiff|Whitchurch]], [[Llandaff]], [[Pontcanna]], the city centre and [[Grangetown, Cardiff|Grangetown]], before emptying into [[Cardiff Bay]], near to the mouth of the [[River Ely]].

===Taf Fawr===
The Taf Fawr rises below the peak of  [[Corn Du]], south-west of [[Pen y Fan]] and soon flows in a generally southerly direction through a steep-sided valley,<ref name=osmap>Ordnance Survey, 1:25,000 map</ref> which was identified by Cardiff's Borough Engineer John Avery Brandon Williams as the best source of water for the town when he assessed all possible sources of water for the newly formed [[Cardiff Corporation Waterworks]] in 1881.{{sfn |Wheatley |1905 |pp=461-462}} A bill was presented to Parliament in November 1883, and despite serious opposition from riparian landowners, Royal Assent was obtained for the Cardiff Corporation Act 1884 on 7 August. It allowed the corporation to build three reservoirs.{{sfn |Wheatley |1905 |pp=461-462}}

The catchment of the upper Taf Fawr was {{convert|10400|acre|km2}} but it was split into an upper area of {{convert|4000|acre|km2}} and a lower one of {{convert|6400|acre|km2}}. Any works had to provide compensation water to maintain the flow in the Taf Fawr, and working on the upper area first meant that the Corporation only had to supply {{convert|3|e6impgal|Ml}} per day of compensation flow until work started on the lower area. [[Cantref Reservoir]], the lower of the two in the upper area, was constructed first. Work began on 4 May 1886 and was completed on 14 September 1892.{{sfn |Bowtell |Hill |2006 |pp=9-10}} Construction of [[Beacons Reservoir]], the highest in the chain, began shortly afterwards, in April 1893, in advance of the Corporation obtaining a second [[Act of Parliament]] to increase the capacity of the reservoir and to move the dam further upstream, where the foundations would be better, in the light of geological investigation.{{sfn |Wheatley |1905 |p=464}} Impounding of the water began on 17 September 1897.{{sfn |Bowtell |Hill |2006 |p=14}}

Construction of [[Llwyn-on Reservoir]], the third in the chain, did not start until 1911, and again, its capacity was increased by an Act obtained in 1909 to {{convert|1260|e6impgal|Ml}}, almost double that specified in 1884.<ref name="Coflein">{{cite web|url=https://coflein.gov.uk/en/site/404686/details/llwyn-on-reservoir-taff-fawr-reservoirs-cardiff-waterworks|title=Llwyn-on Reservoir, Taff Fawr Reservoirs, Cardiff Waterworks |website=www.coflein.gov.uk|access-date=1 June 2020}}</ref> Impounding of water began on 23 June 1926, and the reservoir was full by November, but formal commissioning did not take place until May 1927.{{sfn |Bowtell |Hill |2006 |p=19}} Once built, it supplied {{convert|7.75|e6impgal|Ml}} of compensation water per day to maintain the flow in the river.{{sfn |Wheatley |1905 |p=465}}

Below Llwyn-on, the river is crossed by the [[A470 road|A470 Brecon to Merthyr road]], the [[A465 road|A465 Heads of the Valleys road]], and as it passes to the south-west of [[Cefn-coed-y-cymmer]], the Cefn Railway Viaduct. which consists of 15 arches built on a curve. It was to have been built of stone, but a masons strike in 1866 resulted in the [[Brecon and Merthyr Railway]] buying 800,000 bricks to complete it. It is [[grade II* listed]] as its history and architecture surpass that of most other railway viaducts in Wales.<ref>{{NHAW |num=11377 |desc=Cefn Railway Viaduct |accessdate=28 August 2020}}</ref> On the west bank are the remains of a leat, constructed in 1766 for the [[Cyfarthfa Ironworks]]. It is fed by a stone weir with a [[cast iron]] sluice. Parts of the leat are cut into solid rock, and parts have stone walls and buttresses.<ref>{{Watprn |Cadw |3123 |title=Tai Mawr Leat for Cyfarthfa Ironworks |access-date=28 August 2020}}</ref> The river is joined by the Taf Fechan near [[Cyfarthfa Castle]].<ref name=osmap/>

===Taf Fechan===
[[File:Pontsticill Water Treatment Works.jpg|thumb|Pontsticill Water Treatment Works]]
The Taf Fechan rises immediately to the south of Pen y Fan and runs southwards through three reservoirs and a former fourth, now abandoned.<ref name=osmap/> Whereas the Taf Fawr was the preserve of Cardiff Corporation, the Taf Fechan was used to supply water to Merthyr Tydfil Corporation. Of the Upper Neuadd and Lower Neuadd reservoirs, the lower one was built first, authorised by an Act of Parliament obtained in 1876. Like those on the Taf Fawr, it had an earth embankment with a clay core. The clay had to be imported, and for this purpose a private branch line was built from the [[Brecon and Merthyr Tydfil Junction Railway]] near [[Torpantau railway station]]. The contract for the work was given to William Jones of Neath, and the project was completed in 1884. Now decommissioned,<ref>{{cite web |title=Welsh water to restore reservoir to its natural state |url=https://corporate.dwrcymru.com/en/news-media/2019/welsh-water-to-restore-reservoir-to-its-natural-state |website=Welsh Water |publisher=Dwr Cymru Welsh Water |access-date=5 December 2020}}</ref> the water level when the reservoir was full was at {{convert|1413|ft|m}} above [[Ordnance Datum]], and it held {{convert|74|e6impgal|Ml}}.

The Upper Neuadd Reservoir was rather larger, and was authorised by an Act of Parliament obtained in 1895. The dam which is {{convert|75|ft|m}} high was constructed of masonry, and some 100,000 [[Long ton|tons]] were carried along an extended railway to the construction site. Although the contractors Holme and King of Liverpool were employed to do much of the preparatory work, the building of the dam was carried out by direct labour, with Merthyr Corporation's surveyor, Thomas F Harvey, acting as resident engineer. Work began in 1896 and finished in 1902. It held {{convert|340|e6impgal|Ml}}, and with a water level at {{convert|1506|ft|m}}, it was one of a very small number of artificial lakes built above the {{convert|1500|ft|m|adj=on|sigfig=3}} contour.{{sfn |Bowtell |Hill |2006 |pp=36-37}} The dam had a small tower to the west, and a larger one to the east, below which a tunnel outlet built in Piranesi style sat at the base of the dam.<ref>{{NHAW |num=84824 |desc=Dam at the Upper Neuadd Reservoir |accessdate=28 August 2020}}</ref> Neuadd House, built as part of the reservoir project in 1896, is just downstream from the dam.<ref>{{NHAW |num=84830 |desc=Neuadd House |accessdate=28 August 2020}}</ref> An octagonal building at the east side of the Lower Neuadd dam is also a listed structure.<ref>{{NHAW |num=84832 |desc=Octagonal building at Lower Neuadd Reservoir |accessdate=28 August 2020}}</ref>{{Clarify|date=February 2024|reason=When was this dam and reservoir decommissioned?}}

The river continues southwards through a steep-sided wooded valley and is crossed by Pont Cwmyfedwen, an early- to mid-19th century single span bridge<ref>{{NHAW |num=21160 |desc=Pont Cwmyfedwen |accessdate=28 August 2020}}</ref> before it reaches [[Pentwyn Reservoir]], the oldest of the four reservoirs. It was built by the Merthyr Board of Health between 1859 and February 1863, and the consulting engineer for the project was [[Thomas Hawksley]], but despite this, the dam was built over a geological fault, which led to large volumes of leakage. This leakage was one of the main factors that led to the construction of the Lower Neuadd Reservoir. Remedial work was carried out at regular intervals, but never seemed to last for long. Repairs undertaken in 1912/13 reduced the level of leakage from {{convert|11|to|2|e6impgal|Ml|0}} which was sufficient until [[Pontsticill Reservoir]] could be built to impound the leaking water.{{sfn |Bowtell |Hill |2006 |p=40}} The corporation had obtained the Act of Parliament to authorise it in 1911, and awarded a contract to [[Sir Robert McAlpine]] & Sons on 16 June 1913. The contract price of £232,000 included various ancillary work including diverting the roads on both sides of the valley. The top of the earth dam was {{convert|110|ft|m}} above the valley floor, and the reservoir was designed to hold {{convert|3290|e6impgal|Ml}}, although this was subsequently increased a little by raising the water level by {{convert|12|ft|m}}. Completion was delayed by the onset of the First World War, and when work resumed in 1922, the Corporation used direct labour. The Taf Fechan Water Supply Act had been passed in 1921, creating the Taf Fechan Water Supply Board, uniting the Rhymney Valley Water Board, the Pontypridd and Rhondda Joint Water Board, the Urban District Councils of Aberdare and Llantrisant & Llantwit Fardre, and Merthyr Tydfil Corporation. The reservoir was opened by Lord Buckland of Bwlch on 21 July 1927.{{sfn |Bowtell |Hill |2006 |pp=42-44}}

The valve tower is octagonal and built in Gothic style, with a copper-covered spire. The outflow is a large funnel with convex sides and concrete ribs. Both are grade II listed, together with the dam and a lattice steel bridge.<ref>{{NHAW |num=81199 |desc=Dam, valve tower, bridge and outflow on Pontsticill Reservoir |accessdate=28 August 2020}}</ref> The filter house, with its twelve rapid gravity filter beds, which have been little altered since 1923, is also listed,<ref>{{NHAW |num=21733 |desc=Filter House at Pontsticill Water Treatment Works  |accessdate=28 August 2020}}</ref> as are the turbine house, which controlled how much water flowed over the weir,<ref>{{NHAW |num=21732 |desc=Turbine House at Pontsticill Water Treatment Works |accessdate=28 August 2020}}</ref> and the compensation basin below that, which is used to regulate the flow in the Taf Fechan below the reservoir.<ref>{{NHAW |num=21731 |desc=Compensation Basin at Pontsticill Water Treatment Works |accessdate=28 August 2020}}</ref> Below the works is Pont Sticill, a single span bridge with a datestone showing it was built in 1825, which gives its name to the village.<ref>{{NHAW |num=81194 |desc=Pont Sticill (also known as Pontsticill Bridge)  |accessdate=28 August 2020}}</ref>

Below [[Pontsticill]] the river forms the boundary of the Brecon Beacons National Park<ref name=osmap/> and descends into a wooded gorge, where it is crossed by the seven-arched Pontsarn Viaduct built for the Brecon and Merthyr Railway in 1866. It is {{convert|92|ft|m}} high and {{convert|420|ft|m|sigfig=3}} long.<ref>{{NHAW |num=11484 |desc=Pontsarn Railway Viaduct |accessdate=28 August 2020}}</ref> Just to the south of the viaduct is Pont-sarn, a stone bridge built in 1864 after the previous wooden one collapsed. This occurred because the parishes of Merthyr and Vaynor were supposed to maintain it jointly, but could not agree, and so it became dilapidated.  There were proposals to widen it in 1955, but the plans were withdrawn when there was stiff opposition from local people.<ref>{{NHAW |num=11482 |desc=Pont-sarn |accessdate=28 August 2020}}</ref> Below the bridge, the river plunges into Pwll Glas or the Blue Pool.<ref>{{cite web |title=Pwll Glas |url=https://coflein.gov.uk/en/site/411452/details/pwll-glas-blue-pool-pontsarn |website=coflein |publisher=RCAHMW |access-date=5 December 2020}}</ref> The river continues to flow south-westwards around the  hamlet of Trefechan, and as it approaches [[Cefn-coed-y-cymmer]], there is a tramway and leat on the east bank. The tramway was built in 1792, and was used to carry limestone to the Cyfarthfa Ironworks from Gurnos quarries, while the leat was constructed in 1825. Its main function was to provide the ironworks with a good supply of water, but it also fed the ornamental lake at Cyfarthfa Castle through a syphon.<ref>{{Watprn |Cadw |2299 |title=Gurnos Quarry Tramroad & Leat |access-date=3 September 2020}}</ref> After passing under the A465 and the A4054 roads, the Taf Fechan merges with the Taf Fawr at the wooded [[confluence]] that gives Cefn-coed-y-cymmer its name.

The river holds a large population of wild [[brown trout]], many of which were killed in 2006 when three tonnes of [[aluminium sulphate]] spilled into the river from the Pontsticill Water Treatment Works, which United Utilities operate on behalf of [[Dwr Cymru Welsh Water]]. The pollution turned the water white for at least {{convert|3|mi|km|0}} downstream of the works<ref>{{cite web |url=http://news.bbc.co.uk/1/hi/wales/4789121.stm |title=River polluted by chemical spill |archive-url=https://web.archive.org/web/20071222011417/http://news.bbc.co.uk/1/hi/wales/4789121.stm |archive-date=22 December 2007 |url-status=live |publisher=BBC News |date=14 August 2006}}</ref> and killed approximately 23,000 fish, including wild brown trout, [[European bullhead|bullhead]]s, [[stickleback]] and [[pike (fish)|pike]], and a large number of invertebrates. [[Environment Agency Wales]] estimated that the river would take six to twelve years to recover.<ref>{{cite web |url=http://www.martinjamesfishing.co.uk/cgi-bin/news/news.cgi?article=774&vf=true&site=mjfishing |archive-url=https://web.archive.org/web/20200902173838/http://www.martinjamesfishing.co.uk/cgi-bin/news/news.cgi?article=774&vf=true&site=mjfishing |archive-date=2 September 2020 |url-status=live |title=ACA News Update |publisher=Martin James Fishing |year=2007}}</ref> The trout population had resumed breeding by 2009.{{citation needed|date=November 2016}}

===Below the confluence===
Just below the confluence of the Taf Fawr and Taf Fechan, the river is crossed by the [[Pont-y-Cafnau]] tramroad bridge. This was probably the first iron railway bridge to be built, and was unusual in that it had three levels. The main deck carried the {{railgauge|4ft}}-gauge Gurnos Tramway, beneath which there was an iron trough to carry water from the Taf Fechan leat, while a second water supply was carried in a wooden launder above the tramway tracks. The cast iron structure was manufactured at the Cyfarthfa Ironworks.<ref>{{Watprn |Cadw |317 |title=Pont y Cafnau Tramroad Bridge |access-date=3 September 2020}}</ref> On the west bank of the river are the remains of the ironworks, which began operating in 1765. The artifacts include seven blast furnaces, which formed part of the largest ironworks in the world in its heyday.<ref>{{Watprn |Cadw |3118 |title=Remains of Blast Furnaces, Cyfarthfa Ironworks |access-date=3 September 2020}}</ref> The river runs through the western edges of [[Merthyr Tydfil]], where it is crossed by modern bridges carrying the A4054 and A4102 roads, and by Jackson's Bridge, an early 19th century single span structure that carried the Dowlais tramway and a road.<ref>{{NHAW |num=11388 |desc=Jackson's Bridge |accessdate=3 September 2020}}</ref>

Two modern bridges in central Merthyr Tydfil carry the northbound carriageway of the A4054 across the river to its west bank and back again, with a weir between them. Nant Rhyd-y-car joins on the west bank at Cae-draw, just before the A4102 crosses. As it approaches Abercanaid Industrial Estate, the railway from [[Merthyr Tydfil railway station]] joins the east bank of the river and runs parallel to it for much of its length. It curves around the eastern edge of [[Abercanaid]], below which it is crossed by the A4060 road bridge. At [[Troed-y-rhiw]] the B4285 Bridge Street crosses, and the [[Afon Tâf High School]] if located on the east bank. A little further south, [[Ynysowen]] Community Primary School is on the west bank and the river curves around the eastern edge of [[Aberfan]], part of the Merthyr Vale community.<ref name=osmap/> Below Aberfan, the river enters a wooded section, and the remains of the [[Merthyr Tramroad]] are sandwiched between the river and the modern railway. The Merthyr or Penydarren Tramroad was built in 1793, and was the scene of the first passenger carrying train journey in the world, when [[Richard Trevithick]]'s high pressure steam locomotive pulled wagons containing 5 [[imperial ton|tons]] of iron ore and seventy passengers in 1804. The tramway ceased operation around 1880, and this section, which is a scheduled monument, is particularly well preserved.<ref>{{Watprn |Cadw |319 |title=Merthyr Tramroad: Pont y Gwaith section and associated bridges |accessdate=6 October 2020}}</ref>

The river is crossed by an old farm access bridge at Pont y Gwaith, with a single span of {{convert|55|ft|m|1}} and a width of {{convert|14|ft|m}}. It carries a date plaque stating it was built in 1811, but that probably refers to an earlier wooden bridge, and the main arch was rebuilt in 1993.<ref>{{NHAW |num=11515 |desc=Pont y Gwaith Bridge |accessdate=6 October 2020}}</ref> The river turns to the east to flow around the southern edge of [[Treharris]], and then in a large loop around higher ground on which is Goitre-Coed. Three listed bridges cross the loop. The first was built by [[Isambard Kingdom Brunel]] in 1840–41, and consists of six arches on a slight curve. It carried the single track [[Taff Vale Railway]], but was doubled in width within 20 years, to enable it to carry twin tracks.<ref>{{NHAW |num=11514 |desc=Quakers Yard Railway Viaduct |accessdate=13 October 2020}}</ref> The second was part of the Merthyr Tramroad, and was built in 1815 after the original wooden bridge collapsed into the river when a train crossed it. It has a span of {{convert|63|ft|m|1}} and is one of the earliest railway bridges, but was in poor condition in 2002,<ref>{{NHAW |num=80907 |desc=Greenfield Bridge, Penydarren Tramroad |accessdate=13 October 2020}}</ref> as is the Victoria Bridge, which was also rebuilt in 1815.<ref>{{NHAW |num=80910 |desc=Victoria Bridge, Penydarren Tramroad |accessdate=13 October 2020}}</ref>

Continuing to the south-west, the river is crossed by the A472 and A470 roads, and at Abercynon is crossed by the B4275 road. Immediately to the south of the bridge was an aqueduct carrying the defunct [[Glamorganshire Canal]] over the river. The [[River Cynon|Afon Cynon]] joins on the right bank, and close to the junction is spanned by a skewed railway bridge with two arches of unequal sizes.<ref>{{NHAW |num=80763 |desc=Taff Vale Railway Bridge at Abercynon |accessdate=13 October 2020}}</ref> The valley then widens, and the river begins to meander. On the northern edge of [[Glyncoch]], the river is joined by the [[Nant Clydach]] on its right bank, and to the south of the settlement is crossed by a three-bay girder viaduct, built in 1885 to carry a branch of the Taff Vale Railway over the river to [[Albion Colliery]] at [[Cilfynydd]].<ref>{{NHAW |num=24849 |desc=Taff Vale Railway Viaduct over River Taff |accessdate=13 October 2020}}</ref> Just to the south is White or Berw Bridge, designed by Pontypridd Urban District Council's surveyor, P R A Willoughby. It was built in 1907, aided by L G Mouchel & Partners, who pioneered the use of reinforced concrete, and the {{convert|115|ft|m|adj=on}} span over the river was the longest arch in Britain using this material when it was constructed.<ref>{{NHAW |num=24848 |desc=White Bridge (also known as Berw Bridge) |accessdate=13 October 2020}}</ref> The next crossing is Pontypridd Bridge, a high-arched single span of {{convert|140|ft|m}}. It was built in 1756 by an Independent minister and self-taught civil engineer called William Edwards, and was his third attempt, after his two earlier bridges collapsed. It features three round openings in its spandrels, a device he used to relieve the pressure on an unusually wide arch. It was repaired by Edward David and Thomas Evan in 1798, and is attached to the newer Victoria Bridge on its south side.<ref>{{NHAW |num=13497 |desc=Pontypridd Bridge |accessdate=13 October 2020}}</ref>

On the east bank is [[Ynysangharad War Memorial Park|Ynysangharad Park]], where there is an [[Arts and Crafts movement|Arts and Crafts]] lido, designed in the 1920s and opened in 1923. It is now disused, but is grade II listed, as it is one of the earliest outdoor lidos in South Wales.<ref>{{NHAW |num=24891 |desc=Lido at Ynysangharad Park |accessdate=26 October 2020}}</ref> On the west bank, the river is joined by the [[River Rhondda|Afon Rhondda]], before it sweeps to the east in a large bend. The A4058 dual carriageway crosses the bend at an angle, and as the river resumes its southward course, it is crossed by Machine Bridge, which is also known as Pont y Doctor, as it was built by Dr Richard Griffiths in 1809, as part of a tramway to carry coal from the Hafod Uchaf pit to the Glamorganshire Canal. It has three arches, and was widened around 1910, in an early use of reinforced concrete. Some of the 19th century fabric remains, and is thought to be the earliest multi-span railway bridge still in existence in the world.<ref>{{NHAW |num=24912 |desc=Machine Bridge (also known as Pont y Doctor) |accessdate=26 October 2020}}</ref> Two more modern road bridges are located on its south side, and further downstream is Castle Bridge, a narrow structure with three arches dating from the early 19th century. It formerly carried a road, but is now only used by pedestrians.<ref>{{NHAW |num=24869 |desc=Castle Bridge |accessdate=26 October 2020}}</ref> Next there is a large, crescent-shaped weir, which was built in 1834–5 to provide water power to the [[Treforest tinplate works]]. The sluice to control the flow of water to the works is at the western end of the weir, and probably dates from a little later. The works continued in operation until 1939, and a fish ladder was added in 2003, to allow migrating fish to access the upper river.<ref>{{NHAW |num=80670 |desc=Treforest Tinplate Works Feeder Sluice and Weir |accessdate=26 October 2020}}</ref> Many of the building still exist, some distance to the south of the weir, including a casting house,<ref>{{NHAW |num=13506 |desc=Former Casting House and Workshop at Treforest Tinplate Works |accessdate=26 October 2020}}</ref> a workshop,<ref>{{NHAW |num=13507 |desc=Workshop NW of Tinning House at Treforest Tinplate Works |accessdate=26 October 2020}}</ref> a tinning house,<ref>{{NHAW |num=13508 |desc=Former Tinning House at Treforest Tinplate Works    |accessdate=26 October 2020}}</ref> a smithy,<ref>{{NHAW |num=13509 |desc=Former Smithy at Treforest Tinplate Works |accessdate=26 October 2020}}</ref> a rolling mill,<ref>{{NHAW |num=13510 |desc=Former Rolling Mill at Treforest Tinplate Works |accessdate=26 October 2020}}</ref> and the retaining wall for the leat. The leat had seven sluices with gates to feed the works, but all have been bricked up.<ref>{{NHAW |num=24882 |desc=Leat Retaining Wall at Treforest Tinplate Works |accessdate=26 October 2020}}</ref>

===Diversion in Cardiff===
In the early 1840s the [[South Wales Railway]] was trying to find a suitable site for a railway station, but the area that is now [[Cardiff Central railway station]] was prone to flooding. At this point the main route of the Taff was around [[Cardiff Castle]] and down what is now [[Westgate Street (Cardiff)|Westgate Street]], with the lands where [[Cardiff Arms Park]] and the [[Millennium Stadium]] are now sited tidal flats which were prone to flood.

[[Isambard Kingdom Brunel]]'s solution was to divert the Taff to the west, creating a larger and safer site for the station. The station was opened by the South Wales Railway in 1850.<ref name="Brunel">{{cite web|url=https://cricketarchive.com/Glamorgan/History/Cardiff_Arms_Park/Creation.html|publisher=Cardiff Council|title=Cardiff Arms Park, A short History - The Creation of the Arms Park|access-date=2008-05-22|url-status=dead|archive-url=https://web.archive.org/web/20121015004127/http://cricketarchive.com/Glamorgan/History/Cardiff_Arms_Park/Creation.html|archive-date=2012-10-15}}</ref>

==Tributaries==
===Nant Ffrwd===
[[File:Waterfall on the Taff upstream of the disused railway bridge - geograph.org.uk - 78996.jpg|right|thumb|215px|Waterfall on the Taff near [[Pontypridd]]]]
Underneath the [[Cefn Coed Viaduct]], the [[Nant Ffrwd]], a tributary that runs eastward in a deep wooded gorge before flowing into the Taf Fawr above the confluence with the [[Taf Fechan]], emerges into the river from a deep, narrow gorge.

===Nant Morlais and Nant Rhydycar===
The Taff continues south through the centre of [[Merthyr Tydfil]], where it is joined by the [[River Taff#Taf Fechan|Nant Morlais]] which emerges at [[Abermorlais]] from a culvert in the east bank. Just south of Merthyr weir, the [[Nant Rhydycar]] joins.

===Taff Bargoed, Cynon, Nant Clydach and Rhondda===
South of Merthyr, the Taff begins to [[meander]] its way between [[Pentrebach]] and [[Abercanaid]] and through [[Troed-y-rhiw]], [[Merthyr Vale]] and [[Aberfan]] towards [[Quakers Yard]]. Here, the [[Taff Bargoed]], [[Nant Mafon]] and then down into [[Abercynon]] in the [[Cynon Valley]] where the [[River Cynon|Afon Cynon]] merge with the Taff and, slightly further downstream the [[Nant Clydach]] joins.<ref>{{cite web |url=http://www.cardiff.gov.uk/objview.asp?object_id=9589 |archive-url=https://web.archive.org/web/20120319181802/http://www.cardiff.gov.uk/objview.asp?object_id=9589 |archive-date=19 March 2012 |url-status=dead |title=River Taff Corridor Action Plan |date=April 2007 |page=7}}</ref> At [[Pontypridd]] it is joined by the [[River Rhondda|Afon Rhondda]]. From Pontypridd, it runs roughly south before arriving at the northern boundary of the city of [[Cardiff]].

==Mouth of the Taff==
[[Image:RiverTaffFrozen.jpg|thumb|Frozen river at the [[Millennium Stadium]] (2010)]]
In Cardiff, the natural course of the river was changed during the 19th century; from [[Cardiff Castle]] it now follows an artificial riverbed west of where it previously flowed, following a path through [[Bute Park]], past the [[Cardiff Arms Park]] and the [[Millennium Stadium|Principality Stadium]]. The Taff flows into [[Cardiff Bay]], an artificial lake created by the construction of the [[Cardiff Bay Barrage]] in the 1990s, before flowing into the [[Severn Estuary]].

==See also==
* [[Pont-y-Cafnau]], world's earliest surviving iron railway bridge
* [[Cardiff Rivers Group]]

==Bibliography==
{{Refbegin}}
*{{cite book
  |last1=Bowtell |first1=Harold D |last2=Hill |first2=Geoffrey
  |title=Reservoir Builders of South Wales
  |publisher=Industrial Railway Society
  |year=2006
  |isbn=978-0-9540726-2-9
  }}
*{{cite book
  |url=https://www.british-history.ac.uk/cardiff-records/vol5/pp457-469
  |last=Wheatley |first=Joseph Larke
  |title=History of the Cardiff Corporation Waterworks Undertaking
  |series=Cardiff Records: Volume 5
  |publisher=British History Online
  |year=1905
  }}
{{Refend}}

===References===
{{Reflist}}

==External links==
*[http://www.ggat.org.uk/historic%20landscapes/Merthyr%20Tydfil/English/Merthyr_Features.htm Glamorgan-Gwent Archaeological Trust] {{Webarchive|url=https://web.archive.org/web/20060925020745/http://www.ggat.org.uk/historic%20landscapes/Merthyr%20Tydfil/English/Merthyr_Features.htm |date=2006-09-25 }} Merthyr Tydfil Features

{{coord|51|28|N|3|11|W|display=title|region:GB_type:river_source:GNS-enwiki}}

{{Rhondda Cynon Taf|state=collapsed}}
{{authority control}}

{{DEFAULTSORT:Taff}}
[[Category:River Taff| ]]
[[Category:Rivers of Cardiff]]
[[Category:Rivers of Merthyr Tydfil County Borough]]
[[Category:Rivers of Rhondda Cynon Taf]]
[[Category:River navigations in the United Kingdom]]