Others before me have pointed out the irony in the fact that Kenfig survived many assaults by armed men but then yielded to the sea and sand. The site of the town is about a mile from the sea and it lies roughly ten metres above sea level. At the time of its foundation there would have been sand dunes along the beach, but it is likely that they were in a stable state. The first inhabitants of the town would have had no reason to fear the catastrophe that was to come.
Sand dunes form where there is a large reserve of sand, the prevailing winds blow towards the shore, and the coast rises gently rather than in the form of cliffs. All of these conditions are met at Kenfig. Indeed as South Wales is directly exposed to the force of the Atlantic Ocean dunes have formed at many places along the coast. An additional factor in the Bristol Channel is that it has an exceptionally high tidal range, one consequence of which is that a much larger area of sand is exposed between successive high tides. More sand will have time to dry out and be carried inland by the wind.
A wind speed of at least 8 knots is needed to cause saltation, that is to roll sand. A wind speed of 20 knots will lift sand into the air and carry it. Research done by Luke Toft has demonstrated that around Kenfig the wind speed is over 8 knots on about 240 days per year, and over 20 knots on about 80 days per year.
See L A Toft, A Study of Coastal Village Abandonment in the Swansea Bay Region 1270-1540, Morgannwg, 1988, XXXII 21-37. You can read this article on the National Library of Wales website. Two additional factors were relevant during the medieval period. There is evidence that a rise in sea level took place at this time. In addition tidal levels follow a 1700 year cycle as well as the more obvious annual cycle. Both cycles are related to the relative positions of the earth, the sun, and the moon. The longer cycle reached the point of highest tides in 1433.
On the face of it, then, it seems that the people of Kenfig were the unlucky victims of a combination of natural factors that brought the sand gradually closer to their town. It covered the fields and areas of pasturage between the sea and the southern edge of the town, it then surmounted the town walls, and finally it submerged the town itself. Indeed it moved on and covered the castle as well.
The true story is almost certainly more complicated. The shoreline north of the River Kenfig was subjected to the same natural forces and it had dunes along the fringes of the beach, and yet there the dunes remained stable and did not come inland. The crucial difference is that only the dunes on the south side of the river were subjected to the impact of human occupation.
The first recorded evidence of encroachment by the sea and the sand comes in an account supplied by the Bailiff of Glamorgan in the year 1316. It refers to a field called Conyger, where the rent for pasture over the previous six months had been 2s 6d. A similar account two years earlier indicates that the rent in 1314 was 3s 6d for just three months. Moreover, the document from 1316 adds as an explanation for the reduced rent that "the greater part is drowned by the sea".
The field known as Conyger lay close to the sea. Its name indicates the presence of rabbits, and indeed there is other evidence that the dunes were deliberately used as rabbit warrens. The rabbits would have been culled at regular intervals. Their meat would have been eaten and their skins used for clothing. In addition, it is clear that the field was being used to graze farm animals. The combination of rabbits and livestock grazing would have destroyed the vegetation that kept the sand dunes in a stable state. Patches of bare sand would have emerged and the wind would have carried it successively further inland.
We do not know how and when the people of Kenfig decided to leave, but it is likely that their departure from the town took place in a series of stages. The final abandonment may have occurred in 1439 following a major storm. In other sections we will look more closely at the processes of decision making people go through when the desertion of a community is gradual, but at Kenfig each person would have made an individual decision based on their particular circumstances. Some would have had good reason to leave at an early stage, others would have preferred to stay until it was clear that life in the town was no longer possible.