The fields around the lower Bure, the Yare, Waveney etc are largely water meadows, where the water is meant to go in a flood situation. The EA and BESL have largely prevented that with their works over the last 20 years or so.
I recall the first tidal surge after the work on the Chett had been completed. Yards in Loddon were covered in up to 3' of water, whilst the water meadows lower down remained dry. When challenged, EA engineers proudly claimed that it was exactly as the computer model expected.