Image-based 3D modeling as a damage prioritization tool for historic buildings in post-disaster areas: The case of the 2020 Beirut blast

On August 4th, 2020, a colossal blast at the port of the Lebanese capital, one of the largest in history not caused by a nuclear reaction, changed Beirut's historic neighborhoods within seconds from a busy, vibrant and living cultural hub into an urban fabric of shattered buildings, collapsed masonry walls and scratched pitched roofs. With not enough preparedness for such a calamitous event, the affected local community faced significant challenges as they attempted to recover from the damage done. Once a heritage site is lost, damaged or destroyed, the recovery and rehabilitation process is slow, if (at all) possible. In the wake of such events, there has been a growing interest to digitize historic sites and buildings to preserve them (digitally) against unforeseen threats such as natural or man-made disasters. However, little work has been done to explore the role of 3D documentation for post-blast inspection of masonry historic buildings. The objective of this work is to expose an efficient workflow for accelerating the assessment process of damaged historic buildings by the application of digital technology in post-disaster areas, through the case study on the Beirut Blast. The originality of this work resides in the fact that this was the first time ever that Beirut and its historic buildings were massively digitized. This paper outlines how and why 3D image-based modeling was implemented, emphasizing on the timely benefits for disaster recovery and improvement of decision making in a similar emergency case. The results of the documentation produced a fast yet accurate 3D models of the affected historic buildings in Beirut, despite the challenging structural properties of the post-blast built environment. Post-processing of the data provided cultural heritage experts and engineers with valuable documents for structural deficiencies, damages and accessibility, which facilitated the remote assessment of the buildings and accelerated the implementation of emergency interventions.