Tsunami evacuation risk change associated with urban recovery in Banda Aceh after 2004 Aceh tsunami

This study evaluates the changes in tsunami evacuation risk in Banda Aceh, Indonesia, two decades after the devastating 2004 Indian Ocean tsunami. Centered around the “Build Back Better” framework from the Sendai Framework for Disaster Risk Reduction, it investigates how urban recovery efforts, particularly the construction of tsunami evacuation buildings (TEBs) and population relocation, have impacted evacuation feasibility. Using spatial population data from WorldPop Hub and network-based simulations with ArcGIS, the researchers model evacuation scenarios in Meuraxa district—the area at highest tsunami risk in Banda Aceh. The analysis also considers how changes in population distribution over time interact with the availability and capacity of evacuation infrastructure.

The study finds that while urban recovery has led to significant reductions in tsunami evacuation risk, key vulnerabilities persist. In the most at-risk zone (R3), the population decreased to about 75% of its pre-tsunami level, while safer areas saw increases—suggesting some effective relocation. However, 29% of the population still lives in high-risk zones. Evacuation simulations showed that without TEBs (Scenario A), 84.5% of residents would fail to evacuate within 35 minutes—the estimated tsunami arrival time. This dropped to 3.1% with current TEBs (Scenario B) and 1.1% with the addition of nearby potential facilities (Scenario C). Despite reduced average evacuation times (from 49.7 to 14.7 minutes), many facilities are overcrowded—some exceeding capacity by over 1000%. The study concludes that while recovery efforts have improved evacuation readiness, uneven infrastructure distribution and growing population densities in risk zones mean that further investment in evacuation capacity and better spatial planning are critical to future resilience.