Damage-cost assessment of vernacular buildings against coastal flooding

Coastlines across the globe have been experiencing threats due to rising sea-level. The global average rise in the annual sea level is projected to be 2 -3 mm putting the coastlines across the globe into a threat. South-East Asian countries would experience sea-level variation from 1.5 mm to 4.4 mm per year, exacerbating inundation risk due to tidal anomalies. Many of these countries bear relatively higher population density and fall under developing economy – hence under-equipped to follow proactive strategies for adaptation.

Recurring flood hazard incapacitates regional sustainability. Rapidly changing climate scenarios further add to the climate-hazard sensitivity by increasing the frequency of extremes. The coastal communities experience multiple threats of such climate sensitivity due to rising sea-level and high tide anomalies In the form of loss of life and livelihood, overbearing losses from disaster-related damages to the infrastructure damages. Particularly those associated with residential building impose significant liability on marginal groups, presenting ‘disaster recovery’ nearly an impossible target to achieve. Therefore, damage reduction becomes an inevitable parameter for disaster risk reduction (DRR).

This research presents a methodology for the assessment of vernacular building typology in coastal areas of Sundarbans in eastern India. The area adjoining the Bay of Bengal is the part of largest Mangrove delta in the world The case area, Sagar Island has 75 percent of its population residing within traditional housing system that is now under potential economic stress due to reoccurring floods. The process begins with probing insight on the damage and failure pattern induced by floodwater to the housing and helps in the development of a systematic framework for ‘damage preventing intervention’ for primary building typology. The study categorizes damage stages associated with the high tide flooding levels using the synthetic method of data collection. This is followed by damage cost calculation for the flood levels considering the available remedies. Therefore, suggesting a proactive approach for disaster resilient design depending on robustness and cost-effectiveness of the chosen remedies. As the vernacular buildings are still a popular habitat choice in various parts of developing/ urbanizing South Asia, the research finds a generic application for upgrading vernacular housing design standards for regional sustainability.

Keywords: flood hazard, high tide flooding, climate change, vernacular housing, damage assessment