English: doctrine of accretion and diluvion
Welsh: athrawiaeth crynodiant a chrebachiant
Subject: Cyfraith
Welsh definition: The doctrine of accretion and diluvion recognises the fact that where land is bounded by water, the forces of nature are likely to cause changes in the boundary between the land and the water. We would expect these changes to be gradual and imperceptible. As the watercourse changes naturally and progressively with time, so the land boundary follows it. There may be some gain, there may be some loss. The law accepts this and considers it to be fair.