Flood monitoring stations-England
The real-time data API provides information on readings of water levels and flows take at a variety of measurement stations. A given station may provide more than one set of measurements, for example, both water level and flow rate or water level at two different spots (e.g. up-stream and down-stream of a sluice or weir). The API provides metadata on these stations and on the different measures available from each one, as well as the readings themselves.
this uses Environment Agency flood and river level data from the real-time data API (Beta)
More details available at: http://environment.data.gov.uk/flood-monitoring/doc/reference#introduction