Low-cost flood sensors that local communities can run themselves
Small, battery-powered sensors measure how high the water is and send the readings to a public website, so people can see what is happening, as it happens.
What we have done in South Oxford
We have worked with the South Oxford Flood Action Group (SOFLAG) to put water-level monitoring across South Oxford. There are now 18 monitoring points:
- 3boreholes, tracking groundwater
- 5radar sensors, measuring water level from above
- 10gauge boards, read by local people and reported from a phone
How SOFLAG uses it
SOFLAG is a residents' group, supported by Project Groundwater and the Oxford Flood Alliance, that helps people in South Oxford get ready for floods and keep up with one while it happens. Flood Network runs the monitoring behind its Local Monitoring page. Volunteers and local residents fit the sensors. From then on the boreholes and radars report every 15 minutes, with nobody needing to visit. Volunteers read the gauge boards and send in the level from a phone. All of it reaches the SOFLAG website within minutes. Each site has a graph, a five-day trend, a place on a map and a note on what its level means for flooding nearby, shown alongside the Environment Agency's own river gauges.
We turn every reading into a height above sea level, as well as a depth at the site. That means a borehole, a lake and a stream can go on the same chart, so SOFLAG can show how groundwater falls from Grandpont towards New Hinksey, or how water stands from the Hinksey Stream across to the Weirs Mill Stream. In a flood, residents can watch the sites nearest them rather than waiting for a general warning. Every flood we record also helps pin down the level at each site at which homes and gardens start to flood, so the group can give earlier and clearer warnings next time.
How it works
A radar sensor on a bracket measures the distance down to the water surface, without touching it. Knowing how high the sensor sits, we can work out the depth of the water.
The sensor sends the reading by a low-power radio network to a nearby receiver, and from there to the website. It runs on batteries, so it can sit by a stream or down a borehole where there is no mains power or Wi-Fi.
See the readings
The live graphs and map are on the SOFLAG website.
See SOFLAG's live monitoringWhere it started
Flood Network began in Oxford in 2014, testing whether cheap Internet of Things sensors could watch flooding. It became a company in 2015 and went on to work with Bradford, Cardiff and Slow the Flow in Calderdale. Flood Network Ltd closed in 2023. The idea, the know-how and some of the kit carry on in the work above.