The threat has increased over time due to the slow but continuous rise in high water level over the centuries (20 cm (8 inches) / 100 years) and the slow "tilting" of Britain (up in the north and west, and down in the south and east) caused by post-glacial rebound.
ð ə WORD_BOUNDARY θ ɹ ɛ t WORD_BOUNDARY h ʌ z WORD_BOUNDARY ɪ ŋ k ɹ iː s t WORD_BOUNDARY oʊ v ə ɹ WORD_BOUNDARY t aɪ m WORD_BOUNDARY d uː WORD_BOUNDARY t ə WORD_BOUNDARY ð ə WORD_BOUNDARY s l oʊ WORD_BOUNDARY b ʌ t WORD_BOUNDARY k ə n t ɪ n j uː ə s WORD_BOUNDARY ɹ aɪ z WORD_BOUNDARY ɪ n WORD_BOUNDARY h aɪ WORD_BOUNDARY w ɔ t ə ɹ WORD_BOUNDARY l ɛ v ə l WORD_BOUNDARY oʊ v ə ɹ WORD_BOUNDARY ð ə WORD_BOUNDARY s ɛ n t̠ʃ ə ɹ ɹ i z WORD_BOUNDARY t w ɛ n t i WORD_BOUNDARY s iː ɛ m WORD_BOUNDARY eɪ t WORD_BOUNDARY ɪ n t̠ʃ ɪ z WORD_BOUNDARY s l æ ʃ WORD_BOUNDARY w ʌ n h ʌ n d ɹ ɪ d WORD_BOUNDARY j ɪ ɹ z WORD_BOUNDARY æ n d WORD_BOUNDARY ð ə WORD_BOUNDARY s l oʊ WORD_BOUNDARY t ɪ l t ɪ ŋ WORD_BOUNDARY ʌ v WORD_BOUNDARY b ɹ ɪ t ə n WORD_BOUNDARY ʌ p WORD_BOUNDARY ɪ n ð ə WORD_BOUNDARY n ɔ ɹ θ WORD_BOUNDARY æ n d WORD_BOUNDARY w ɛ s t WORD_BOUNDARY æ n d WORD_BOUNDARY d aʊ n WORD_BOUNDARY ɪ n ð ə WORD_BOUNDARY s aʊ θ WORD_BOUNDARY æ n d WORD_BOUNDARY iː s t WORD_BOUNDARY k ɔ z d WORD_BOUNDARY b aɪ WORD_BOUNDARY p oʊ s t ɡ l eɪ ʃ ə l WORD_BOUNDARY ɹ ɪ b aʊ n d WORD_BOUNDARY