The Environment Agency says it is due to tide locking, when high tides restrict river drainage to the sea.
The county council warns some are likely to close because of falling pupil numbers.
Teaching years 1 to 6 in one class is "almost impossible" says the local education authority.
Police believe the cyclist may have information about the crash in which Chris Greenaway was killed.
Chris Greenaway's family urge anyone with information about the crash to come forward.
A man is arrested following the death of a 55-year-old man in Cantley, Doncaster, on Saturday.
Joshua Rafferty lost control of his car and crashed, killing half-brother Aiden Allen.
Police say they have "deployed numerous resources" to try and locate Christine Stenson.
Police continue their search for a woman, 66, from Doncaster who has been missing for over a week.
