The Cardiff tsunami

Shortly after the Indian Ocean tsunami of Boxing Day 2004 which killed 300,000 people, caused by the 3rd largest earthquake ever recorded on a seismograph (magnitude 9.2), Michael Disney, Professor of Astronomy at Cardiff University, claimed that there had been a similar event in the Severn Estuary 400 years previously and dubbed the well-documented ‘Great Flood’ of 1607 the ‘Cardiff tsunami’. Disney (now retired) is one of many academics at Cardiff over the years who have aimed for eye-catching headlines in the tabloid press in the mistaken belief that this will raise the University’s profile. But all the dons usually achieve is to damage its reputation as a serious institution, as Cardiff’s slide down the higher education ranking tables attests. This particular intervention was actually rather daft. There was no ‘Cardiff tsunami’ in 1607 – it was far more frightening than that.

It would take an Atlantic earthquake of at least magnitude 7 to generate any sort of tsunami up the Severn. Such a rare earthquake would have been felt across the whole of north-west Europe and tsunamis would have hit the coasts of Ireland, Pembrokeshire, Cornwall, Brittany and all points south to Portugal. None of that happened. Not one contemporary source reported earth tremors or unusually large waves. No; this was something far more serious than an outlandish, once-in-a-millennium tsunami. This was a concurrence of quite common phenomena that is all too capable of happening again: an exceptionally high spring tide in the Severn combined with a deep low-pressure Atlantic storm surge.

3,000 people died in the 1607 flood, but few if any perished in Cardiff, then a tumbledown fishing village with a population of under 2,000.  Most casualties were further east, on the Gwent levels, the Somerset levels and upriver as far as Gloucester. Cardiff’s moors were swamped as the waters over-topped the ancient sea-banks and came as far inland as Canton and Adamsdown, but since they were virtually uninhabited the main victims were sheep. In a town still confined within its medieval walls the Taff burst its banks and undercut the foundations of 11th century St Mary’s Church (damage it never recovered from and which led to St John’s replacing it as the town’s parish church) – but not one death was recorded. So it is anachronistic and ahistorical to make Cardiff the central victim of this ‘tsunami’. With the entirely undeveloped inter-tidal muds, marshes and creeks of the West Moors and East Moors doing their job as a natural sponge, and the town in any case sheltered from the onrushing water by the barrier of Penarth Head, Cardiff got off relatively lightly and was mainly affected by the ebbing back-wash.

To Cardiffians this was not a new experience, just a severe version of events that had regularly occurred from time immemorial. There were further major inundations in 1703, 1763, 1764, 1768, 1775, 1792 and 1827 before sea walls were raised in the 1830s to allow dock construction on the East Moors at the start of Cardiff’s coal era. Tidal flooding was greatly reduced, but not eliminated. When full-moon spring tides coincided with rain-swollen rivers and westerly gales, Cardiff suffered further soakings, most notably in 1960 and 1979. The opening of the Cardiff Bay Barrage in 1999 eased the routine tidal worry by dint of severing Cardiff’s connection to the sea, but introduced a new threat by raising the water table – and didn’t alter the fact that Cardiff is the 3rd most flood-vulnerable city in the UK (after London and Hull). The complete eradication of the absorbent moors plus the rising sea-levels and increase in extreme weather events caused by man-made climate change make the chances of another 1607 happening one day more likely – and next time it won’t be just sheep that get it.

Even now, when the Barrage is shut because the tide is in and when there’s been heavy rain in the Glamorgan hills, the artificial lake (still, oddly, unnamed) frequently rises above the boardwalk in the Inner Harbour. The uncomfortable truth for Cardiffians is that, were you starting from scratch, you most certainly would not build a city on a flood plain at the confluence of three turbulent rivers fed by countless mountain streams in one of the wettest parts of Europe and adjacent to a funnel-shaped estuary with the 2nd highest tidal range on the planet. The 1607 flood was not as exciting or as newsworthy as a tsunami – it was just geography. I think it’s wrong to ride the bandwagon of topical tragedies as a way to shoe-horn yourself into higher Google rankings, I really do…

Bay apartment dwellers get the sea view they were promised