By EUR ING Brian M Back
With a plethora of communications technologies now available, it is easy for decision-makers to be persuaded by the latest innovation when designing flood warning systems, managing flood interventions, or architecting wider Disaster Risk Management (DRM) solutions.
However, in critical infrastructure, it is essential to pause and reflect. Beyond the well-discussed issue of cybersecurity, there are several fundamental considerations that must never be overlooked. These include:
- Denial-of-service vulnerability
- Technological obsolescence
- Third-party dependency and lack of service level agreements
- Testability and maintainability
- Availability of skilled support
- Legal protection from interference
- Overall system safety integrity
Ultimately, the importance of each factor depends on the consequence of failure. In flood risk management, where lives, infrastructure and public confidence are at stake, communications resilience is not optional - it is fundamental.
Designing for failure
Nothing is infallible. Therefore, a critical flood warning system must:
- Automatically detect and report its own failure
- Fail gracefully
- Include a fallback provision
Where systems are genuinely critical, redundancy should be built in from the outset. Dual redundancy provides two independent paths for operation; triple redundancy provides three. This may include parallel sensors, independent power supplies, or multiple communication channels.
Autonomy is equally important. Systems that rely heavily on third-party infrastructure may introduce hidden vulnerabilities.
The reality of cellular networks
Cellular networks are frequently perceived as ubiquitous and reliable. In practice, they are neither.
They:
- Do not offer 100% availability
- Do not proactively notify users of outages
- Can become overloaded during disasters
- Experience coverage variability
- Are weather-sensitive
- Are in constant technological transition
The sector’s focus on higher speeds and new standards means that obsolescence can quickly undermine long-term infrastructure investment.
For these reasons, cellular should rarely be the sole bearer for critical flood systems. A parallel, independent network - such as Iridium satellite - can provide valuable resilience.
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Radio telemetry: degrees of resilience
Radio telemetry remains one of the most autonomous communication media available. Properly designed, it can create a localised network around the asset requiring protection.
There are three broad categories:
1. Licence-free
Licence-free spectrum can be effective for short-range applications, particularly where signals do not cross third-party land. However, it offers no protection from interference. Adopters are encouraged to engage with the Low Power Radio Association (LPRA), which provides valuable guidance.
2. Licence-free LPWAN (e.g., LoRa)
Low Power Wide Area Networks can offer cost-effective connectivity but often rely on third-party gateways and internet backhaul. This dependency can undermine resilience if not carefully managed.
Backhaul resilience must always be considered as carefully as the sensor network itself.
3. Licensed radio
Licensed radio telemetry is arguably the most resilient option.
In the UK, licences are issued by Ofcom. Exclusive licences provide the highest protection, albeit at greater cost. However, they offer:
- Legal protection against interference
- Criminal liability for eavesdropping
- Full architectural control
System topology is determined by the architect. A particularly resilient approach involves multiple transmitters broadcasting to multiple receivers, creating inherent redundancy at network level.
Consequence-driven design
Flood warning systems are safety-critical systems. The communication architecture must be selected based on consequence of failure, not convenience or fashion.
In many cases, the most resilient solution is not a single technology, but a layered architecture combining:
- Licensed radio
- Satellite backup
- Carefully managed cellular where appropriate
The guiding principles should always be autonomy, redundancy and graceful degradation.
Because when floodwaters rise, communications must not fail.
About the Author
EUR ING Brian M Back
Since 1987, Brian has spent nearly 40 years designing and building radio communication systems from the protocol layer upwards. His systems deliver billions of messages annually and are deployed in applications ranging from groundwater and sewer flood monitoring to railway and national grid flood safety systems.
He is Vice Chair of the Low Power Radio Association (LPRA) and has served on Ofcom working groups including BRIG and TAG, as well as contributing to ETSI in Europe and the FCC in the United States.
Brian is a Chartered Engineer, Fellow of the IET, and Senior Warden Elect of the Worshipful Company of Engineers.