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physwbgy. Third edition, McGraw Hill, New York Belding, H. S. and Hatch, T. F. (1955) Index for

evaluating heat stress in terms of the resulting phys- iological strain. Heat. ripng Airconditioning, 27, pp.

De Freitas, C. R and Ryken, M. G. (1989) Climate and physiological heat strain during exercise. Znt, J. BwmetemL, 33, pp. 157-164

De Freitas, C. R., Dawson, N. J., Young, A. A. and Mackey, W. J. (1985) Microclimate and heat stress of runners in mass participation events. J. Clim. AppL Meteml., 24, pp. 184191

Fox, E. L. and Mathews, D. K. (1981) Thephysiological bask ofphysical education and athletics. Third edition, Saunders College Publishers, New York

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Missenard, A. (1937) L'homme et le climat. Paris Spellman, G. (1996) Marathon running - an all-

weather sport? Weather, 51, pp. 11&125 Trapasso, L. M. and Cooper, J. D. (1989) Record

performances at the Boston Marathon: Bio- meteorological factors. Znt. J. Bwmeteml., 33, pp. 235237

Vugts, H. F. (1985) Je dag hebben en de rest. De Veteraan, 19, pp. &9

Young, K. C. (1979) The influence of environmental parameters on heat stress during exercise. J. AppL Meteml., 18, pp. 886-898

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Heavy rain September

D. J. Naylor

and floods in Glamorgan, 1909

Meteorological Office, RAF Lyneham

A quick glance at a mean annual rainfall map of the British Isles will show that one of the wettest areas in the southern part of Great Britain is the northern part of the county of Glamorgan, South Wales. A close inspection of a relief map of this area (Fig. 1) shows a striking resemblance to the average rainfall pattern -

Fig. 1 Places mentioned in the text and the main rivers

confirming the importance of orography to the rainfall distribution in this part of Britain.

During 28 September 1909, more especially the evening of that date, heavy rain fell over a wide area of Glamorgan resulting in rivers and streams rising rapidly, then overflowing, caus- ing flooding and much grief to many valley communities and also to the main towns situ- ated at the mouths of the valleys. This was at a time when the area was heavily industrialised and trying to keep pace with a rapidly expand- ing coal-mining industry. Although not as se- vere over as wide an area as the floods and damage caused by the heavy rains of November 1929 and the Decembers of 1960 and 1979, the flooding nevertheless caused very great distress due to the time of its onset - so soon after the rains that caused it.

Synoptic situation

At 0700GMT on 28 September, a large anti- cyclone stretched from the Faeroe Islands to

107

Fig. 2 Symptzc chart for 0700GibrT on 28 Septeniber 1909. Dashed line indicates the position of the trough1 posszble wanlz front.

a ridge west-north-westwards to the Faeroe Islands. Meanwhile, the axis of the troughi warm front moved a little further south. More importantly, pressure fell steadily to the south- west of Ireland and along the trough, causing it to sharpen considerably by 1800GMT, probably (as far as can be discerned from the weather maps of the day) with two small depressions on the troughiwarm front (one centred near Rosslare and the other near Porthmadog - Fig. 3). By 0700GMT on 29 September, a depres- sion with a centre slightly less than 1009mbar was centred over the Isles of Scilly (the main depression was still centred over the Atlantic between the west of Ireland and longitude 25"W) with a broad trough along the English Channel. This trough was probably the re- mains of the small depression that was centred over Porthmadog at 1800GMT the previous day. By the end of the 29th the depression over the Isles of Scilly had drifted east into north- east France and filled, leaving a broad trough aligned west-east along latitude 50"N.

The heavy rain and its effects

Outbreaks of rain occurred over mOSt of Wales on the 27th, mostly slight but with some heav- ier rain in the north and parts of west Wales (e.g. 47.5mm at Holyhead). The rain con- tinued throughout the 28th, initially mostly slight but becoming heavy at times during the late afternoon in mid Wales and during the evening in Glamorgan.

All of the upland area of Glamorgan (north of a line from Bridgend to Cardim received more than 50mm of rain, with a large part of the north-west of the county receiving more than 75mm (Fig. 4). Although these totals are credited to the period from 0900GMT on the 28th to 0 9 0 0 G ~ T on the 29th, most of the rain fell during the evening of the 28th. The area of the heaviest fall was concentrated over the whole catchment of the River Afan (which

the sea at Port Talbot), the upper reaches of the Rhondda and Ogmore valleys and the south-eastern part of the fiver Neath catchment area, SO it is no surprise to find that the most afflicted places were in the Afan valley (and tributaries) and most notably port Talbot itself.

Fig. 3 Synuptic chan for 1800c;~r on 28 Septeniber 1909. Dashed line nidtcates the posznon of the troughlpossible wanti jkont.

St. Petersburg (Fig. 2) with a major Atlantic depression centred near 49"N, 28"W. A shal- low troughipossible warm front lay from Valen- tia to Darlington, with a very shallow low pressure area over central Ireland. During the day, the centre of the anticyclone became es- tablished over western Russia but still extended

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The observer at Glynconwg recorded 79 mm of rain at 0900GMT on the 29th stating that most of this fell between 2030 and 2330GMT on the 28th. The River Conwg (a tributary of the Afan) running through the village rose by 2.lm in one hour, causing considerable damage to property, the mines, and the railway. The main steel girder bridge across the river was washed away by the very swollen river at about 2300 local time, along with a local haul- ier who was passing over it at the time in the darkness and was drowned. In the Glynconwg area, the District Council estimated the total

I

kT\\ 65 I

. L 4 5 - 7 Q / I

I I

Fig. 4 To& rainfd (mm) fmm 09OoGMT on 28 S e p m - ber 1909 to 0900 GMT on 29 September 1909

damage caused by the floods to be nearly E3000.

Further down the valley, near the village of Cwmavon, 27.5m of the Rhondda-Swansea Bay railway was washed away by the heavily swollen River Afan, causing about 700 colliers travelling to work in the various mines in the valley to return home.

The worst affected place, however, was Port Talbot, especially the district of Aberavon close to where the River Afan enters the sea. The aptly named Water Street (the main thor- oughfare of the district) was under 1.2m of fast- flowing water by the early hours of the 29th and the force of the water washed away many of the doors, windows, and staircases of the houses, filling the downstairs rooms to a depth of 1.8m. Rescue missions were launched between 2200 GMT on the 28th and OOOOGMT on the 29th to

evacuate families from their water-ruined homes, most being rescued through their bedroom windows. At the nearby slaughter house, 15 sheep were drowned. The floods left 100 families homeless and destitute in Aber- avon and, to make matters worse, ironically, the district was completely without running tap water on the 29th due to part of a pipe (which carried the water to Aberavon from a reservoir at Cwmavon) being washed away along with part of a sewer. These pipes were fixed on trestles based on the river bed. Two stone bridges in Port Talbot were also washed away by flood waters.

Flooding occurred throughout the nearby Neath valley and the town of Neath was badly affected. The rainfall total from 09OOGMT on the 28th to 0900 GMT on the 29th at Neath was 70.8mm, a record in over 25 years of observa- tions. Throughout the Neath valley, mines were rendered idle due to flood damage and, in some cases, notably around Resolven, the in- clines built up to the entrances to the mines had been completely washed away.

A similar story of floods and widespread damage was reported from communities in the upper parts of the South Wales valleys. At Blaenrhondda a haulage engine at the entrance to one of the mines was carried away by flood waters, and several bridges over the River Rho- ndda Fawr suffered a similar fate. A surveyor inspecting a bridge near Merthyr was swept away by the swollen river and was feared drowned. In a bizarre incident, the Merthyr coroner pronounced a “supposed death from fright” verdict on a 55-year old woman who, it was reported (by the Western Mad), “before retiring to rest at night became frightened at the terrible downpour of rain and soon after she had gone to bed was found dead”.

Further west at Swansea, things were not so bad, although the main road from Swansea to Mumbles was under water and the South Wales Daily Post reported that, “people returning home from the theatre had to wade through dirty floodwater several inches deep”.

Under the heading “Flood Flotsam”, the Glamorgun Gazette of 8 October 1909 reported,

“An echo of the recent disastrous flood at Blaenrhondda was heard at Ystrad on Mon-

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~~ ~

day [4 October] when Morgan Roberts and Thomas Rogers, colliers, Tynewydd, were charged with stealing a log of timber valued at L2, part of the wreckage carried down the river belonging to the Fernhill Colliery Com- pany. P. C. Williams, Tynewydd, spoke to having seen the defendants sawing the log up. They were fined 10 shillings [5Op] each [about a third of a week’s wages].”

Conclusion

This heavy rainfall event, amounting to be- tween 36 and 56 per cent of the total month’s rainfall for the various reporting stations in Glamorgan, brought untold misery to many people in the county with widespread damage and destruction at a time when the mining industry was expanding rapidly and approach- ing its heyday along with other associated industries.

Over the upland area of Glamorgan, May 1909 was a sunny month with the total rainfall (using figures for Glyncorrwg (221m above mean sea-level) as representative of the upland area) 69 per cent of average. The months of June and July were very dull and cool with rainfall (June and July combined) 129 per cent of average. August 1909, however, was excep- tionally dry and quite sunny with total rainfall only 35 per cent of average. The dryness of August would have, to a great extent, ensured that the poorly drained land at the head-waters of the rivers and streams would not have been ‘over saturated’ prior to this rainfall event, and it follows that the intensity of the downpour must have been a major contributory factor to the events that followed. A comparison of the isohyets of this rainfall event and those of the annual rainfall map shows a striking re- semblance, inferring the importance of orographic influences. This being the case, then it is almost certain that the total rainfall on the high ground enclosed by the 75 mm isohyet (Fig. 4) was much higher than indicated. The intensity of the rain would suggest some em- bedded instability but there were no reports of thunderstorms on 27, 28 or 29 September. One clue, however, can be gleaned from an event a few days prior to this heavy rainfall event. A similar situation (a small depression

moving east across southern Ireland leaving in its wake a trough from the main Atlantic de- pression) occurred between the 22nd and 25th and produced some thunderstorms over the Isle of Arran and North Wales on the 24th and over Essex on the 25th. It follows that the air over the Atlantic associated with the depression was unstable in nature and this instability was released as thunderstorms on the 24th and 25th over some parts of Britain. It is probable chat some degree of instability was associated with the airmass in the troughlwarm front and chat this was ‘released’ in the form of heavy rain. The small depression centred near Porthmadog was probably the cause of the heavy rain, convergence in this feature combined with ex- tra uplift by the hills being the triggers to release the instability.

Due to the expanding industrialisation at the time, the hillsides were laid bare of trees, much of the timber being used for pit props for example (before industrialisation it was said that a squirrel could go from Glyncornvg to Port Talbot without its feet touching the ground). This, combined with the steep-sided nature of the hillsides, exacerbated the problem of runoff water and the narrowness of the valleys helped increase the force of the very swollen fast-flowing rivers which caused so much grief and destruction.

Acknowledgements

I would like to thank the following for their assistance in the preparation of this article: the staff at the National Meteorological Library and Archive, Bracknell, the Mid Glamorgan Library Local History Section, the West Glam- organ Library Local History Section and Glyn Thomas of the Welsh Miners Museum.

Bibliography British Rainfall (1909) Heavy falls on rainfall days,

September 1909, pp. 96-97 Dady Weather Repon (1909) September, Meteorological

Office Transactions ofthe Cardzff Naturalists’ Society (1909) Vol.

XLII, Meteorological observations in the Society’s District, pp. 1-14

Thomas, G. (1985) Glimpses ofthepast in the Afan valley Vol. 2, Welsh Miners’ Museum Committee, 62 pp.

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