The flood damage depends on the flood occurrence frequency and vulnerability of assets. Their vulnerability is characterized by fragility curves. Therefore, it is necessary to develop the fragility curves to estimate the damage of flood events. The fragility curves are often derived from experience of experts or the field survey data of historical flood events.
Tuyển tập Hội nghị Khoa học thường niên năm 2018 ISBN: 978-604-82-2548-3 AN APPLICATION OF RIACT TO COLLECT FLOODDAMAGED BUILDINGS IN HA TINH PROVINCE Nguyen Thanh Thuy , Vu Thanh Tu , Sheng-Lin Lin2 , Kelvin Berryman2 Faculty of Hydrology and Water resources, Thuyloi University Email: thanhthuy_rt@tlu.edu.vn GNS Science, s.lin@gns.cri.nz INTRODUCTION The survey was conducted in the The flood damage depends on the flood downstream of Ngan Truoi reservoir in Ha Tinh province Corresponding to the dam occurrence frequency and vulnerability of assets Their vulnerability is characterized by break scenario for the Ngan Truoi reservoir provided by Damwatch, the attributes and fragility curves Therefore, it is necessary to develop the fragility curves to estimate the damage information from previous events (if any) for building assets (including key damage of flood events The fragility curves are often derived from experience of experts facilities, such as hospital, schools and government office) were collected in Vu or the field survey data of historical flood events As the survey objective is to collect Quang, Huong Khe, Duc Tho and Huong Son districts ( ?) These areas are lowlands and practical information on typical Vietnam buildings for developing exposure models, a distributed along Ngan Truoi, Ngan Sau and Ngan Pho rivers broad range of building types (e.g concrete, masonry, and traditional house) were visited METHODOLOGY in Ha Tinh province The buildings are The survey was implemented with the spatial distributed and variable in structure Therefore, it is no doubt that a collection tool support of RiACT, which is a field data to store the location and characteristics of the collection application developed by GNS buildings needs to be used RiACT (Real- Science (Lin et al 2014, 2018) RiACT time Asset Collection Tool) application was enables surveyors to georeference building locations, photograph, to assign a unique selected for this study identifier number and fill in pre-populated fields STUDY AREA related to building attributes and damage Building attributes collected for each surveyed building are provided When the building attributes could not be identified, the term “Unknown” was applied Beside the location, the collected information of each building for constructing damage curves and/or estimating flood damages are clustered into groups, including building information, construction information and exposure The building information includes the building usage, construction year, number of floors below Figure Surveyed areas in Ha Tinh province 592 Tuyển tập Hội nghị Khoa học thường niên năm 2018 ISBN: 978-604-82-2548-3 and above ground, footprint area The construction information contains construction standard, ground floor form, height of ground floor to surface, main material of supporting columns, main material of walls, main material of roof, building types (as the building classification of Vietnam) The data in RiACT can be export to “.csv” file or upload into the online database Over the three-day survey period, around 500 buildings were visited These buildings were evenly distributed across four districts, namely Vu Quang (205), Huong Khe (140), Huong Son (88) and Duc Tho (59) For each building, building and exposure attributes were surveyed, and general observations of previous damage (e.g water level) were recorded RESULTS AND DISCUSSIONS Building attributes Among the building attributes, the building materials, ground floor material and floor height which are controlling factors of building’s vulnerability are presented in this paper Four hundred and eighteen buildings were surveyed (85%) with concrete or brick/stone supporting columns with external wall cladding comprised of similar material (85%) Most of concrete frames observed were reinforced with steel although density of reinforcing was highly variable In many cases, exposed reinforcing observed for buildings under construction was ‘light’ in density It was difficult to determine the presence and density of concrete reinforcing for all respective buildings Therefore, concrete masonry is a general term used here representing both reinforced (i.e reinforced concrete) and unreinforced (i.e brick/stone) construction frames (Figure a) A very small number of iron/steel and wooden framed building were also surveyed External walls were cladded with either brick or stone masonry (83%), wood (6%), slabs or bamboo screen (5%) External walls for industrial building were cladded with sheet metal or corrugated iron External walls constructed of other materials such as metal and reinforced concrete collectively account for less than 4% of buildings surveyed External wall cladding was cited as ‘other’ or undefined by surveyors for 10 buildings due to reasons such as mixed use of materials (Figure b) (a) (a) (b) Figure Contributions of different building materials in total surveyed buildings (b) Figure Contribution of different ground floor materials (a) and ground floor height (b) in total surveyed buildings 593 Tuyển tập Hội nghị Khoa học thường niên năm 2018 ISBN: 978-604-82-2548-3 Huong Khe is flooded every flood season; however, the flood losses tend to decrease A modern multi-storey concrete building alongside with old one-story building has been common in this area in recent years (Figure 2) People and assets are evacuated to higher floors when the flood warning is received stone masonry wall cladding, and cement tile or metal sheeting roof cladding The ground floor heights are mainly less than 1.2 m The information on the consequence of historical flood events were collected occasionally in this study and should be focused on the coming surveys The collected information should be cross-checked between different sources such as data of the local authority reports, interviews and satellite images The practical building attributes which were surveyed and described in this study is going to support the future development of exposure data for the consequence impact modelling from the failure of Ngan Truoi dam ACKNOWLEDGEMENT The survey was in the framework of Viet Nam – New Zealand Dam Safety Project Figure Improved construction practice to funded by the New Zealand government We cope with the potential floods would like to thank Nguyen Cam Van, Luong Thi Thanh Huong and Phil Glassey for Flood water depth The surveyed maximum water depth varies supporting us to conduct the survey We also from 0.6 to m and from to 3.5 m in the would like to thank the Vu Quang, Huong flood events in 2010 and 2016, respectively Khe, Huong Son and Duc Tho Districts for A comparison was done by overlaying the permissions to conduct the survey and recorded water depth with flood water maps District/Commune officers who travelled published by UNOSAT in 2010, and 2016 with us to guide the survey areas There is some level of discrepancy between REFERENCES the surveyed and satellite-detected water level during these floods As stated, a [1] Lin, S.-L., King, A.B., Matcham, I (2014) Exposure Data Development Framework: relatively high degree of uncertainty Rea-time Individual Asset Attribute associated with the flood water detection and Collection Tool (RiACT), Inventory classification is expected in the UNOSAT Repository & Asset Repository Web Portal, maps because of the complexity of the mixed in Proceedings, NZSEE Annual Technical urban, marshland and aquaculture Conference & AGM, Auckland, New environment On the other hand, the Zealand reliability of the water depth provided by the Lin, S.-L.; King, A.B.; Horspool, N.; Sadashiva, house owners might be doubting due to the V.; Paulik, R.; Williams, S (2018) Field Data absence of official documentation and Collection Framework Development and measurement Applications, in Proceedings, NZSEE Annual Technical Conference & AGM, Auckland, New Z CONCLUSIONS Most of surveyed buildings are residential with concrete masonry construction, brick or 594 ... columns, main material of walls, main material of roof, building types (as the building classification of Vietnam) The data in RiACT can be export to “.csv” file or upload into the online database Over... warning is received stone masonry wall cladding, and cement tile or metal sheeting roof cladding The ground floor heights are mainly less than 1.2 m The information on the consequence of historical... varies supporting us to conduct the survey We also from 0.6 to m and from to 3.5 m in the would like to thank the Vu Quang, Huong flood events in 2010 and 2016, respectively Khe, Huong Son and Duc