Evaluasi Struktur Bangunan Pasar Inpress Blok IV Gedung B dengan Metode Pushover

Inpres market block IV Pasar Raya Padang is not designed as a shelter building, but is designated as a vertical evacuation site when a tsunami occurs. This study aims to evaluate the structural performance of Inpress market block IV zone B. The method used for this research is the pushover analysis method. According to FEMA P-646/2019, vertical evacuation refuge structures are included in tsunami risk category IV, based on the risk category the maximum performance level is at the Immediate Occupancy (IO). For loads on buildings, refer to SNI 1727:2020 and SNI 1726:2019 for earthquake loads. For the calculation of the capacity of concrete structural elements, refer to SNI 2847:2019. Structural analysis was carried out using the SAP2000 version 16. After analysis, based on performance points, drift ratio that occur due to earthquake loading in X-direction and Y-direction are 0,05875% and 0,0067%. The maximum total drift that occurs is smaller than that required by ATC-40 for the Immediate Occupancy performance level, which is 1%. Thus, the structure performance level is Immediate Occupancy. This means that the Inpress market block IV building is still strong enough against earthquake loads.

Mapping of IOC-UNESCO Tsunami Ready Indicators in the Pangandaran Village, Indonesia

Pangandaran Village is a tourist village located in Pangandaran Regency, West Java Province, Indonesia. The beautiful view of sand beaches and abundant marine resources make Pangandaran Village has great economic potential. However, in 2006, an earthquake with a magnitude of 7.7 Mw triggered a tsunami disaster in the Pangandaran area that caused more than 600 fatalities, injuries, and damage to buildings, especially in Pangandaran Village. Based on current research, there is potential for an 8.7 magnitude earthquake off the south coast of Java in the near future, triggering an enormous tsunami. The coastal community in Pangandaran Regency has been building a tsunami risk reduction strategy to anticipate the tsunami disaster. In Pangandaran Village, the local community is piloting the 12 tsunami ready indicators following the guideline from UNESCO-IOC. Therefore, this study aims to map 12 tsunami ready IOC-UNESCO indicators in Pangandaran Village to evaluate which indicators the government and community of Pangandaran Village. The method used in mapping 12 tsunami ready indicators in Pangandaran Village is to take data in the field by doing aerial photographs, conducting interviews with the village government and other related local stakeholders, mapping tsunami evacuation plan and infrastructure, and disseminating questionnaires to the community to find out the response to the tsunami disaster. Based on the IOC-UNESCO tsunami indicator mapping results, all indicators have been fulfilled. However, several other aspects of tsunami preparedness indicators still need to be improved to strengthen tsunami preparedness in Pangandaran.

Exposures of Building and Population to Tsunami Hazard in Pangandaran Beach, Indonesia

Pangandaran and Pananjung villages are located in the southern coast of Java Island, prone to tsunami hazard originating from a megathrust earthquake off south of Java Island. Those villages experience a tsunami earthquake on 2006 from an M7.8 earthquake. The National Center for Earthquake Studies released a map of the sources and hazards of Indonesia’s earthquake in 2017 with a potential earthquake of magnitude 8.7-9.2 in the megathrust of Java Island. This research aims to estimate the potential number of buildings and the population affected by tsunami inundation from two scenario; first scenario is based on historical event of a M7.8 intraplate earthquake, and second scenario is based on a plausible M8.7 intraplate earthquake. The first scenario tsunami modeling resulted an inundation of 108.606 ha, while in the second scenario estimate an 867.351 ha of inundation area. Building data is obtained by digitizing aerial photographs taken in November 2021. The calculation of potential affected buildings is carried out by overlaying the tsunami inundation data with the existing building data in the study area. Meanwhile, the population data used is obtained from the local government in 2021. To obtain the number of the affected population, population distribution is first carried out in each class of land cover, overlaid with the tsunami inundation data. The estimated number of buildings and population affected by scenario 1 and 2 in Pangandaran Village is 1,040 buildings along with 2,765 people, and 4,216 buildings with 11,209 people respectively. While in Pananjung Village, it is estimated a total of 149 buildings with 350 people affected, and 4,039 buildings with 9,493 people affected respectively. This indicate that scenario 2 impact is potentially 4 times greater than scenario 1 in Pangandaran village, and 27 times greater in Pananjung village, implying a different strategy of tsunami risk reduction should be taken to save more lives. The results of this study can be used as a basis for policymaking by the government in carrying out a more effective tsunami disaster mitigation efforts in Pangandaran and Pananjung Villages. This study also calls for reevaluation of coastal villages tsunami risk based on each plausible scenario.

Participatory Mapping of Tsunami Evacuation Routes (Case Study of Karangbenda Village Cilacap Regency)

Indonesia is one of the countries with a high tsunami risk, in this case the community plays an important role in disaster management, one of which can be done through the preparation of a tsunami evacuation route map which can be done through participatory mapping. This research was conducted in Karangbenda Village, Adipala District, Cilacap Regency, the purpose of this study was to determine how the skills of the community in determining tsunami evacuation routes were compared with the criteria for evacuation locations and effective evacuation routes and to test the effectiveness of tsunami evacuation routes prepared by the community. Data collection in this study was carried out through focus group discussions (FGD) and field surveys. The results show that the community can arrange a tsunami evacuation route properly, the evacuation route consists of the evacuation location and evacuation route, the designated evacuation location is in accordance with the evacuation location criteria and the evacuation route is in accordance with the route obtained through network analysis. The effectiveness level of the tsunami evacuation route was 98.82% and there were some people who were unable to reach the evacuation location within the specified time, totaling 36 people who were in the area of Dusun Congot to be precise in RT 02 / RW 02 because of the long distance from the evacuation location.

Disaster risk reduction through the reform of spatial structure and land use planning in Banda Aceh City

Reform of spatial structure and land use planning aims to reduce disaster risk and protect development outcomes. Ignoring spatial reform will increase the risk of more significant damage. A resilient city has the essential character to survive and to bounce back in no time. This decade, the development of global countries has focused on investing in resilience to protect development outcomes, including livelihoods. This study aims to determine the index of tsunami risk, vulnerability, and capacity and the proposed concept of spatial planning reform in the city of Banda Aceh. The research uses explanatory methods with geographic information systems and literature studies. The formula for calculating the vulnerability index was derived from Perka BNPB No. 2 of 2012. The high level of land use changing into settlements in coastal areas since the rehabilitation and reconstruction period until now, accompanied by a higher level of vulnerability (v), tsunami hazard (h), and low capacity (c) to reduce vulnerability exposure, indicates that it is necessary to reform the spatial plan of Banda Aceh City for mainstreaming the resilience infrastructure. Through investing in resilience infrastructure, the city’s capacity will increase and reduce the risk (r), and finally, the protection of development and citizens can be realized.

Mini Special Issue on Tsunami Numerical Modeling Benchmarks – Challenges of Tsunami Modeling Hackathon –

Numerical simulation and modeling became an essential technology in tsunami research and disaster management. Various numerical models were proposed and utilized for the development of tsunami risk assessment, inundation maps, and evacuation plans. The model verification and validation standards would be crucial to ensure sufficient reliability of tsunami risk assessment, inundation maps, as well as a consistency among various efforts. Common approach to ensure sufficient accuracy and reliability of numerical modeling is developing benchmark problems of hydraulic experiments and to use them for numerical model’s verification and validation. To satisfy this requirement, “Tsunami Modeling Hackathon” was held in September 2020 to organize new benchmark problems in numerical modeling of tsunamis and to improve their reliability and accuracy. Hackathon is an intensive-gathering event of computer programmers and others involved in software development to create outcomes by the end of the event. This event was organized by Prof. Tomoyuki Takahashi of Kansai University and his colleagues, who led the tsunami research subcommittee in Japan Society of Civil Engineers (JSCE). Tsunami modeling hackathon, in which about 23 teams and 162 researchers joined, included experiment and modeling teams in seven benchmark problems: urban tsunami inundation, landslide tsunami, tsunami loading on seawalls and coastal structures, sediment transport, drift of floating objects. The modeling groups performed the blind tests to cross-validate and interpret the results of their simulations in seven benchmark problems given by the experiment groups and discussed the improvement. This special issue reports the outcomes of the tsunami modeling hackathon, and includes six papers (five in this issue, one in the regular issue). We hope this issue will provide useful insights for tsunami modelers and contribute to establishing a standardized way to ensure that various tsunami numerical models would be validated through the benchmark problems.

Comparisons of Numerical Models on Formation of Sediment Deposition Induced by Tsunami Run-Up

Tsunami sediments provide direct evidence of tsunami arrival histories for tsunami risk assessments. Therefore, it is important to understand the formation process of tsunami sediment for tsunami risk assessment. Numerical simulations can be used to better understand the formation process. However, as the formation of tsunami sediments is affected by various conditions, such as the tsunami hydraulic conditions, topographic conditions, and sediment conditions, many problems remain in such simulations when attempting to accurately reproduce the tsunami sediment formation process. To solve these problems, various numerical models and methods have been proposed, but there have been few comparative studies among such models. In this study, inter-model comparisons of tsunami sediment transport models were performed to improve the reproducibility of tsunami sediment features in models. To verify the reproducibility of the simulations, the simulation results were compared with the results of sediment transport hydraulic experiments using a tsunami run-up to land. Two types of experiments were conducted: a sloping plane with and without coverage by silica sand (fixed and movable beds, respectively). The simulation results confirm that there are conditions and parameters affecting not only the amount of sediment transport, but also the distribution. In particular, the treatment of the sediment coverage ratio in a calculation grid, roughness coefficient, and bedload transport rate formula on the fixed bed within the sediment transport model are considered important.