Reducing disaster risk to life and livelihoods by evaluating the seismic safety of Kathmandu’s historic urban infrastructure : enabling an interdisciplinary pilot.

Kathmandu’s medieval cities and shrines are exceptional architectural and artistic achievements underpinned by centuries of seismic adaptation. They host urban infrastructure of tangible and intangible value and play vital roles of cohesion in the life of thousands of people. They also represent portals where the heavens touch earth and individuals can commune with guiding deities. The 2015 Gorkha Earthquake and its related aftershocks were a human disaster, killing 9,000 people and displacing 2.8 million. Generating 7.6% of Nepal’s GDP through tourism, Kathmandu’s iconic skyline was dramatically altered by the earthquake. It destroyed 500,000 homes and undermined the sustainability of Nepal’s tourist industry and its 400,000 employees. However, it was also a cultural catastrophe damaging 403 monuments in Kathmandu, key elements within the Valley’s historic urban infrastructure. Their collapse caused multiple fatalities and first responders demolished others fearing that they might also fall and injure residents and visitors. With Overseas Development Assistance pledges of $2.5 billion US dollars, Nepal’s Government approved the rehabilitation of much of Kathmandu’s historic infrastructure but there is continued tension between interpretations of Sendai’s ‘Build Back Better’ framework and the obligation to preserve the authenticity and intangible values of its UNESCO World Heritage Properties. Many risk reduction strategies implemented in Kathmandu are demolishing historic buildings and rebuilding them in modern materials; while other monuments have been hybridised with metal bracing or concrete reinforcement. Mud mortars are frequently being replaced by cement and lime, although the resultant inflexibility is not necessarily seismically advantageous. Most monuments have been, or are being, rebuilt without research and analysis of why they collapsed, while their foundations, which in many cases preserve sequential experimental adaptations offering examples of practical seismic-resistant foundations which could be applied to other structures, are being demolished without record or research. With donor liability fears, contractors privilege modern materials, despite successful histories of vernacular systems. Costly historic bricks have been landfilled, causing supply chain delays and increased environmental impact from kilns. Residents, craftspeople and tour operators and businesses have been frequently excluded from decision-making but the risk to them, and their livelihoods, remains. Building on an interdisciplinary north-south partnership, we have piloted the integration of archaeology and geoarchaeology with 3D visualisation and geotechnical and structural engineering to co-produce and disseminate a methodology to assess, evaluate and improve the seismic safety of historic urban infrastructure within Kathmandu's UNESCO World Heritage Properties, reducing direct risk to life and livelihoods, while respecting and preserving Kathmandu’s authenticity and traditions.