From roots to reach: Network resilience in natural disasters

Disasters rarely announce themselves through collapsed buildings alone. They are also felt through absence, the sudden silence that follows when communication networks fail. In those early hours, before the scale of physical damage is fully understood, it is often the breakdown of connectivity that determines how broad the impact of a crisis becomes.

When communication networks break down, people cannot report their condition, responders lose situational awareness, and entire communities risk slipping beyond the reach of coordinated assistance. Network failure does not merely accompany disaster - it reshapes the human consequences.

Monsoon flooding is a structural condition

Few places illustrate this more clearly than Bangladesh. Shaped by one of the densest river networks in the world, the economy sits at the confluence of the Ganges, Brahmaputra and Meghna systems, with runoff from the Himalayas flowing through vast floodplains before reaching the Bay of Bengal. This geography sustains agriculture and livelihoods, but it also ensures that seasonal monsoon flooding is not an anomaly but a structural condition.

Each year, rising water levels submerge cellular base stations, disrupt power distribution and sever fibre backhaul that follows roads and embankments. Following floods, villages in low-lying and coastal regions often remain physically accessible only by boat, with no access to digital communications. Communication failures can delay rescue, complicate relief coordination and leave populations unable to request the specific help they need.

This fragility is not unique to Bangladesh, but the economy's geography exposes it with particular intensity. Across South Asia, similar patterns emerge at different scales.

Floods in Assam, Bihar and Kerala in India have repeatedly disrupted mobile and broadband services despite dense infrastructure deployment. In Pakistan, monsoon flooding along the Indus River has pushed entire rural districts offline, forcing emergency operations to rely on fragmented, ad-hoc communication. Urban flooding in China has revealed how much modern connectivity depends on uninterrupted power and hierarchical backhaul, with outages cascading rapidly through dependent systems.

These contexts differ politically and economically, yet they share a common weakness: Communication architectures optimized for stability struggle to function once stability disappears.

When physical shock coincides with energy loss

Beyond South Asia, other hazards reveal the same structural limitation.

Bushfires in Australia have cut off rural towns as fire fronts outpaced restoration crews. Wildfires in Spain and California have fragmented access networks through evacuation zones and precautionary power shutdowns. Earthquakes and tsunamis in Japan, as well as the aftermath of the Indian Ocean tsunami affecting Thailand, have demonstrated how quickly connectivity collapses when physical shock coincides with energy loss.

Storm events in Europe, prolonged droughts and floods across parts of Africa, and extreme weather in the Middle East region repeat the pattern in different forms. The technology stack varies by economy, but the failure mode remains remarkably consistent.

The issue is not poor engineering. Contemporary networks are designed with impressive efficiency, but they are also designed for continuity. They assume stable power, predictable traffic and persistent end-to-end paths.

Disasters violate all three simultaneously. Nodes become intermittently reachable. Mobility patterns are driven by survival rather than infrastructure. Energy availability becomes uncertain and uneven. Under these conditions, the collapse of communication is not an exception but an expected outcome of architectures unable to reinterpret their environment dynamically.

Space networking in disaster environments

Delay Tolerant Networking (DTN) operates on fundamentally different assumptions. Rather than attempting to preserve continuous paths, DTN treats disconnection as a normal operating condition. Messages are stored locally, carried by mobile nodes and forwarded opportunistically when contact becomes available.

These principles were originally developed for space and interplanetary communication, where delay and intermittency are inherent. What has become increasingly clear is that connectivity in disaster environments on Earth is more like a deep space network than traditional terrestrial networks.

Yet classical DTN protocols alone are not enough, particularly in regions with weak infrastructure, limited energy resources, and heterogeneous participation. Many DTN designs assume nodes with relatively capable hardware specifications, which will be where they are expected to be, and that will interact with other nodes in predictable ways.

Disaster environments, especially in developing regions, rarely meet these assumptions. Vehicles may not be smart or sensor-rich. Civilian devices may participate intermittently. Energy constraints dominate every decision. Contextual intelligence is just as important as tolerance to delay.

A network designed for human needs

This gap motivated the development of AZIZA, the Adaptive Zone-based Intelligent Fully Distributed Trust-Aware Delay Tolerant Networking Protocol. The starting point was a contradiction that has become difficult to ignore: Humanity can maintain communication across planetary distances, yet here on Earth, communities are frequently disconnected by seasonal floods and fires. The challenge is no longer how far networks can reach, but whether they are designed to function where human need is greatest. AZIZA was conceived as a response to this imbalance, focusing on adaptability rather than infrastructure dependence.

At its core, AZIZA is a unified routing framework that integrates:

• Spatial awareness
• Behavioural trust
• Energy consciousness

Disaster environments do not remain static. Floodwaters rise and recede, shelters form and dissolve, evacuation routes shift, and access corridors emerge unpredictably. AZIZA models this reality by dynamically partitioning the environment into evolving zones defined by mobility patterns, population density and functional roles. Routing decisions adapt as these zones change, allowing messages related to medical coordination, evacuation, or shelter management to be prioritized differently from routine traffic.

Trust plays an equally critical role. In opportunistic networks, not all nodes contribute equally to delivery reliability. Emergency vehicles, responders, and aerial platforms tend to follow more predictable patterns, while civilian devices may be constrained by battery limitations or uncertainty of movement. AZIZA continuously evaluates nodes based on observed forwarding behaviour, encounter stability, and delivery contribution, assigning trust scores that influence routing decisions. This mechanism does not exclude vulnerable participants, but it gradually shifts responsibility toward nodes that demonstrably sustain the network, reducing the impact of misbehaviour or instability without relying on central authority.

Energy awareness is woven into every aspect of the protocol. In disaster settings, energy is often the most limited resource, particularly in regions where access to charging infrastructure is sparse even before a crisis. AZIZA incorporates residual energy into forwarding logic, reducing unnecessary replication and protecting critical assets such as unmanned aerial relays or response vehicles. By balancing delivery performance against energy preservation, the protocol extends network lifetime and maintains operational capacity during prolonged disruptions.

AZIZA was evaluated using the Opportunistic Network Environment (ONE) simulator, incorporating real flood data from Bangladesh to model realistic mobility and disruption patterns. Simulated scenarios included pedestrians, boats, vehicles, and aerial platforms operating under varying levels of infrastructure degradation.

Across identical conditions, AZIZA demonstrated higher delivery probability, lower overhead and more balanced energy consumption compared with established DTN protocols. These results underscore a central insight: Resilience emerges not from aggressive replication, but from informed adaptation.

Systems that remain meaningful when continuity disappears

Although Bangladesh provided the primary case study, AZIZA's design is intentionally portable. The same mechanisms that support flood response in river deltas apply to wildfire scenarios with shifting exclusion zones, earthquake-affected urban environments with abrupt topology changes, and remote communities where permanent infrastructure is economically impractical. In such contexts, opportunistic and delay-tolerant systems are a viable communication layer. This portability is particularly relevant for regions with limited communications infrastructure, where classical DTN assumptions often break down.

Looking ahead, AZIZA is positioned as an evolving framework rather than a static protocol. Future extensions may incorporate lightweight learning models capable of anticipating contact opportunities or adapting to environmental cues without imposing heavy computational overhead.

Security enhancements, including stronger encryption, distributed trust verification and ledger-based mechanisms suited to disconnected operation, can further reduce vulnerability to malicious behaviour.

Continued optimization of storage, forwarding, and destination discovery will help minimize energy consumption, aligning resilience with sustainability. Most importantly, future iterations can deepen human-centred prioritization, ensuring that limited resources serve medical emergencies and evacuation coordination, and provide critical safety information first.

As climate-driven disasters intensify and infrastructure inequality persists, communication resilience can no longer be treated as a specialized concern. Systems must be designed to take uncertainty into account. AZIZA does not claim to solve disaster communication in isolation, but it demonstrates how networking research can build systems that remain meaningful when continuity disappears.

Read our paper for a more comprehensive explanation of AZIZA.

Md Main Uddin Hasan is a researcher in delay-tolerant networking, focusing on secure and resilient communication in intermittently connected environments, including disaster-affected regions, sparse terrestrial networks, and satellite-assisted and interplanetary systems.

The views expressed by the authors of this blog are their own and do not necessarily reflect the views of APNIC. Please note a Code of Conduct applies to this blog.