Predicting post-disaster waste disposal times to improve resilience to tsunamis and earthquakes

Tsunamis and earthquakes pose devastating threats to coastal communities worldwide. However, beyond the immediate destructive power of these events, the negative impact of the disaster waste they produce is sometimes overlooked.

For example, when the 2011 Great East Japan Earthquake struck, approximately 23 million tons of waste were generated, severely hindering post-disaster recovery processes. Similarly, the 2024 Noto Peninsula Earthquake produced 2.7 million tons of waste—equivalent to seven years of normal waste disposal. Thus, rapid processing of disaster waste is essential for restoring community functionality, making it a critical component of resilience.

Effective disaster waste management hinges on the seamless operation of the waste disposal system (WDS), which encompasses collection sites, temporary storage, and processing facilities. However, these systems don’t function in isolation, as they are critically dependent on the functionality of the road network system (RNS) for the transportation of waste.

Unfortunately, previous methods for estimating post-disaster waste disposal times have often overlooked the interdependencies between these two systems, particularly in the face of events that can simultaneously damage both.

Against this backdrop, a research group led by Professor Mitsuyoshi Akiyama and Adjunct Researcher Koki Aoki from Waseda University, Japan, has developed a novel probabilistic framework for estimating the disaster waste disposal time in coastal communities under the combined threat of seismic and tsunami hazards. Their latest study, which was made available online in Reliability Engineering & System Safety on May 14, 2025, focuses on key interdependencies between WDS and RNS, offering a more realistic prediction of post-disaster recovery timelines.

The newly proposed methodology begins with the modeling of buildings, the WDS, and the RNS within the analyzed region. This is followed by a detailed seismic and tsunami hazard assessment, considering the spatial correlation of hazard intensities. The framework incorporates a seismic and tsunami fragility surface for buildings, existing processing facilities, and bridges, enabling the estimation of damage probabilities under combined hazards.

Afterward, based on damage assessments, the amount of generated disaster waste and the initial functionality loss of both the WDS and RNS are estimated. The core of the method lies in its time-dependent evaluation of the functionalities of the two systems, accounting for both the hazard-related interdependency (simultaneous damage) and the subsequent restoration processes for both systems.

Using Monte Carlo simulations, the framework estimates the probability of completing waste disposal within a specific timeframe, considering the transportation and removal of waste based on minimum cost flow principles and the time-varying capacities of both systems.

To showcase their method, the research group applied the framework to a hypothetical 990 km² coastal community in Mie Prefecture, Japan, anticipating the predicted Nankai Trough earthquake. This illustrative example demonstrated how disaster waste disposal time is significantly affected by road network functionality, with damaged bridges creating bottlenecks even when processing facilities remain operational.

“Our findings suggest retrofitting bridges in the RNS and sparse placement of processing facilities in the WDS before the event can reduce disaster waste disposal time,” the researchers highlight.

Taken together, the results highlight the critical importance of collaborative decision-making between stakeholders managing waste disposal and transportation infrastructure. Among various intervention strategies, including improvements to existing processing facilities and increasing road network redundancy, the quick installation of temporary processing facilities has the greatest impact on waste disposal timeframes.

However, the effectiveness of improvements to WDS is significantly constrained by road network functionality, emphasizing the interconnected nature of these systems. “The proposed method provides critical insights for future disaster waste management to enhance community resilience before the anticipated Nankai Trough earthquake,” conclude the researchers.

Overall, this framework represents a significant advancement in disaster preparedness, offering coastal communities a scientifically sound tool for evaluating their resilience to seismic and tsunami hazards. More informed decision-making regarding infrastructure investments and emergency planning will hopefully improve recovery outcomes when disaster finally strikes.

The study was co-authored by Adjunct Researcher Koki Aoki from Waseda University, Japan; Professor Mitsuyoshi Akiyama from Waseda University, Japan; Assistant Professor Abdul Kadir Alhamid from Bandung Institute of Technology, Indonesia; Professor Dan M. Frangopol from Lehigh University, U.S.; and Professor Shunichi Koshimura from Tohoku University, Japan.