Financial assessment of incremental seismic retrofitting of Nepali stone-masonry buildings
This work presents an incremental approach for the implementation of retrofitting so that total investment is spread over time in a gradual and cost-effective way. Despite its critical location, right on top of the Main Himalayan Thrust, the building stock of Nepal is mainly constituted by highly vulnerable non-engineered unreinforced masonry (URM) buildings. Most of them were realized with traditional construction techniques and locally available materials like field stones and mud mortar. The empirical evidence from historical earthquakes has shown that these buildings have very limited seismic capacity. On the contrary, if adequate retrofitting interventions are implemented, their seismic performance can improve substantially. Unfortunately, the upfront investment required by retrofitting remains an issue since it is considered too high and not associated with an immediate and tangible benefit.
Implementing retrofitting at scale is required to strengthen the existing knowledge on seismic risk. Better understanding of risk would also allow to incorporate financial resilience mechanisms like catastrophe insurance. To address the obstacle of high upfront ret-rofitting costs, an incremental strategy has been presented aiming at more flexibility in risk management actions. From the homeowner point of view, incremental retrofitting interventions could be carried out gradually when financial resources become available. The probabilistic cost-benefit assessment carried out in this work has shown that, despite the uncertainties around costing data and real discount rates, retrofitting Nepali stone in mud mortar buildings is in most cases financially advantageous. This means that the Government, supported by donors, could increase resilience in line with the Sendai goals and receive a higher return on its investment. This result represents an important outcome for policy makers and international organizations interested in financing risk reduction programs in Nepal and in other low-to-middle income nations affected by natural disasters.