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In order to detect potential localized flooding on city streets before damage to property happens, it is necessary to know when a gully/drain is full before water spills out onto the pavement.

Following a call by Dublin County Council, Ireland, for a solution to this challenge, mSemicon has developed a sensor that can be attached (by standard metal bands, or even strong plastic wire-ties) to the underside of the grill that covers the gully*. If this sensor detects the presence of rising water, it sends a signal over the Sigfox or NB-IoT network to the cloud, after which it is processed and delivered to the operator who can despatch a team to take necessary action. The signal delivery time is typically much less than 30sec.

*For gullies that do not have grills: the sensor can be attached to a stainless steel bracket that can be fixed to the side of the gully.


There are two water level sensors on board:

  • a magnetic float

  • a proximity sensor

This offers redundancy.

There is also a motion detector on board. When the gully cover (the grill) is opened, the sensor detects this event and sends a signal to the server. This alerts the operator that a maintenance operation is occurring or that an unauthorized access to the gully has taken place.


One of the challenges is to make the device compatible not just with harsh weather, but also with the hazards of standard gully cleaning. The sensor is designed to withstand the rough treatment of this operation. It is not necessary to remove the sensor prior to cleaning.


Installation is quick and easy. The gully is first opened and the sensor attached to the underside of the grill cover at the appropriate location. The metal bands that are in common use by the technical staff of local authorities can be used for this. In some cases, where road traffic is light or non-existent, strong wire-ties can be used. The operation is fast and simple.


The dimensions are 100mm (length) x 45mm (width) x 65mm (height).