Solution to Flood Risk for Environment Agency Wales

Environment Agency WalesDenca has been commissioned to replace the Flood Management control system at Llandudno Junction by Environment Agency Wales (EAW).

The area is defined as “an area of moderate or high flood risk where flood risk is already being effectively managed but where further action may be needed to keep pace with climate change”.

The area is susceptible to flooding from the Afon Wydden and Gyffin rivers in addition to surface water and sewer flooding.

The overall objective of the flood management scheme and its control system is to channel water down from the surrounding hills and mountains and provide interim flood water storage whilst controlling the release of the water in such a manner as to avoid the possibility of dangerous surges and the consequent flooding of domestic and commercial property in the area.

This is achieved using flood water storage compounds at three designated sites: the upstream flood storage area, BT flood storage area and the downstream flood storage area. Stored water is released in a controlled manner by three penstocks and level monitoring at ten locations along the water flood channel with these levels being used to determine the optimum position for each penstock to control the release of the stored water.

The existing control system was showing its age, having been installed way back in 1993 with spare parts becoming increasingly difficult to obtain. What’s more, a recent risk assessment survey has established the need for additional level sensors while an improved interface will facilitate the gathering of long term water level data through the regional telemetry system.

Since the operation of the control system does have a direct impact on the safety of the local inhabitants Denca were very pleased to be selected by EAW as the controls contractor for the implementation of this high profile project.

Some fifteen years ago, Denca was involved in installing a control system to automate the sluice gates and flood water control measures at Bala Lake and Denca’s team of engineers remains subcontracted to oversee annual maintenance.


First and foremost the Afon Wydden project involved replacing three existing controls kiosks and associated electrical installations and the refurbishment of the existing control building.

Each new kiosk and the refurbished control building contain a new control panel housing dedicated instrumentation and a Rockwell CompactLogix PLC with local input/output devices.

The central BTFSA Control building also houses a Rockwell PanelView Plus HMI displaying tabular and graphical information, logged data and a PSTN/Ethernet modern connection to remotely monitor or programme the entire control system. Both a Modbus RS485 interface and a hardwired interface to the client’s Regional Telemetry System have been installed at all four sites. Bespoke control software and bespoke HMI configuration have been provided with the 4 off PLCs interconnected via an Ethernet network implemented over a dual redundant fibre-optic connection using the client’s existing cabling system. As a result, although the BTFSA site is to be the central depot and display point, all information is made available at all four of the sites.

The control system responds to a combination of programmable set point values and data, maximum and minimum operational pre-set values, system processing demands based upon measured values, failsafe shut-down control and alarm messages and digitally-signalled feedback status.

Get in touch with us