1 Introduction

Most tsunamis are related to submarine earthquakes. The sweeping and periodic waves may have a powerful impact on land and even bring devastating disasters. NOAA et al. (2018) pointed out that the Pacific Ocean makes up 70% of the distribution of tsunami sources. Taiwan is located in the circum-Pacific seismic belt and has previously been affected by tsunamis. The 2011 Great East Japan Earthquake was one of the major tsunami warnings issued in recent years. The earthquake caused 19,074 deaths and 2633 missing persons in Japan (Kuroda 2014). The earthquake triggered a tsunami that resulted in the Chiba Oil Refinery storage tank exploding and catching fire. It also washed out the world’s longest breakwater outside the Kamaishi Port in Iwate Prefecture. Besides heavy casualties, the tsunami severely impacted economic activities in such industries as electronic parts, automobile parts, agriculture, and fisheries in East Japan. Tsunamis also washed away cars and oil storage tanks along with buildings, causing fires (Hasemi 2013; Hokugo 2013).

On the other hand, in Taiwan, the tsunami reached Keelung 4.5 h later, but the wave height was only about 10 cm. Although it did not cause a calamity in Taiwan, the country mobilized immediate disaster relief, and counties and cities within the tsunami warning range took corresponding contingency measures. The central government also dispatched mobile communication vehicles to the highlands near seashores to monitor sea-level changes and transmit first-hand data of initial sea-level changes to the Central Emergency Operations Center. After the earthquake, the Council for Transport Policy of Japan (2011) proposed “Port Comprehensive Tsunami Countermeasures” that corporate production lines and logistics facilities should meet the safety requirements and that tsunami inundation depth should be included in the business continuity plan (BCP) in order to maintain the operations in facilities. The Council also considered factors such as the time when the first wave of the tsunami approaches land, the time required for evacuation, and whether the resilience of evacuation facilities is capable of withstanding damages by ships and other drifting large objects, in order to strengthen evacuation facilities in inundation areas.

In 1867, a tsunami hit Keelung Port in Northern Taiwan and caused hundreds of casualties (Chen 2004; Lu 2004). The inundation extended about 22 km westward along the coastline to the Jinshan–Wanli area and about 15 km eastward along the coastline to the Ruifang area. What is more, the V shape of the Keelung Port concentrated the impact of the tsunami, making inroads 2 km into the inland of Keelung City (around the tip of the V shape). This tsunami was an event matching actual historical records, which necessitates a general inspection of the disaster resistance against tsunamis at the Keelung Port.

Keelung Port is one of the international commercial ports in Northern Taiwan. It is an important gateway to the nation and a major hub for passenger and cargo transportation by sea (Fig. 1). In 2019, there were 1,091,360 passengers, and the tonnage of transported cargo was 60,050,195 metric tons. On average, there are about 4,219 longshoremen at the Keelung Port a day. On the same day, five large cruise ships can dock simultaneously with 10,000 passengers at Keelung Port. Once a submarine earthquake initiates a tsunami, destruction to critical infrastructure and core personnel can result in severe consequences for the normal operation of the port area and neighboring residents. Therefore, ports should be diligent in disaster risk management regarding possible tsunami damage and assessing minimum acceptable disruption of operations, so as to minimize tsunami impacts and allow operations to resume as quickly as possible.

Fig. 1
figure 1

a Location of Taiwan and adjacent trenches in the Pacific Ocean; b the relative locations of cities along the seashore in Northern Taiwan; c location of Keelung Port in Taiwan and its surveyed infrastructures

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The purpose of this study is to prepare for disasters by exploring the impact factors of a tsunami on the Port, understanding the Port’s tsunami preparations, disaster-resistant factors and strategies, identifying potential problems of a tsunami's impact on Keelung Port, and lastly concluding with a model.

2 Research methods

We present a general inspection of the disaster resistance against tsunamis under the worst scenario at the Keelung Port based on the literature on tsunami simulations, damage assessment for buildings and infrastructure in the port area, and potential inundation maps. The research methods and steps are as follows:

  1. 1.

    Literature review: Determining the research questions and understanding the history and current situation by first collecting domestic and international tsunami literature facilitating in-depth interviews. This study cites research on the maximum wave height and arrival time of the first wave at ports around tsunami sources in the trenches adjacent to the circum-Pacific seismic belt by the Institute of Transportation, MOTC, and reviewed the articles focusing on major international tsunamis with case studies to understand how serious the tsunamis cause damage to the buildings and infrastructures in the port area.

  2. 2.

    Survey on Keelung Port: Next, we should have some survey on Keelung Port before preparing for the in-depth interview. Therefore, we searched for important information, like operations of port facilities, from the official Keelung Port Web site, and we also conducted a site visit to understand the types, numbers, and locations of critical infrastructure.

  3. 3.

    In-depth interview: After finding academic resources and surveying, an interview outline was developed targeting senior manager that can be categorized into port managers, port lessees, and governmental disaster prevention and relief agencies, with 1–2 interviewees from each office or business. The objective of in-depth interviews is to understand how manager personnel prioritizes the critical infrastructures and proposes the strategies against disasters.

3 Literary review

3.1 Tsunami simulation

Chen et al. (2017) used COMCOT version 1.7 software to analyze the very shallow earthquakes with a 15-km focal depth occurring in the oceanic trenches of the circum-Pacific seismic belt, and the simulation results showed that the wave heights reached their peaks when the resultant tsunami arrived at the observation point, which is 23 m deep and 400 m offshore, outside Keelung Port. Tsunamis originating from the Ryukyu Trench and Manila Trench, which are in close proximity to Taiwan, presented the greatest danger to Keelung Port due to the shortest warning time. The simulation results are summarized in Table 1.

Table 1 The tsunami simulation of moment magnitude scale, maximum wave height, and arrival time of the first wave [from Chen et al. (2017)]
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It has been 150 years since the 1867 Keelung Port tsunami. Few related survey can be found, so the highest wave height can only be estimated without historical record. Experts have different opinions on the causes of the tsunami. Hsu (1983), Lee et al. (2006), Chen et al. (2016) argued that the tsunami was caused by trenches or faults. Wu (2016) simulated the tsunami with virtual location and magnitude without underwater exploration and implied that the submarine landslide caused the tsunami. Besides, there is no breakwater at Keelung Port in 1867, and Hsu (1981), Yu (1994), and Yen (2017) had interviews with locals and investigated the geology to estimate the tsunami-affected area. Hence, since Chen et al. (2017) is an expert having a complete study of ports, we used his simulation data and define the worst case as the scenario with the highest wave height of 4.5 m and the first arrival wave of 58 min.

3.2 Potential tsunami inundation map of Keelung port

Yeh et al. (2014) simulated 600 events that previously affected the tsunami incidents around Taiwan, including different trenches in the circum-Pacific seismic belt. The maximum inundation depths are comprehensively evaluated to produce a potential tsunami inundation map. The National Science and Technology Center for Disaster Reduction (NCDR) developed a software combining Geographic Information System (GIS) and Google Earth to classify the average inundation depths into four categories, that is, < 0.3 m, 0.3 – 1 m, 1 –3 m, and ≧ 3 m. This classification can be found at the NCDR’s Web site (https://dmap.ncdr.nat.gov.tw/). The Web site of NCDR shows that all tsunami inundation depths at Keelung Port would be smaller than 3 m (Fig. 2). Therefore, through the officially published tsunami inundation potential research system, we can assess the impact of a tsunami on buildings and critical infrastructure and design appropriate storage locations for crucial resources or remote backup locations.

Fig. 2
figure 2

Potential tsunami inundation map for Keelung Port

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The Port and Airport Research Institute, Japan, in 2011 investigated the Great East Japan Earthquake, pointing out that, at Hachinohe Port, the wave height reached 5.4 m and that the inundation depth of buildings (measured from 100 m away from the edge of the wharf) was 2.47 m. Also, in the second container port of Hachitaro, the wave height and the inundation depth of buildings (measured from 150 m away from the edge of the wharf) were 6.42 and 2.9 m, respectively. Even though the two wave heights (5.4 and 6.42 m) were different, the inundation depths were both lower than 3 m because the land weakened the power of tsunami. Therefore, the wave height reached 4.5 m at the observation point (400 m outside Keelung Port) in Table 1, while the inundation depth in the Port was less than 3 m in Fig. 2.

3.3 Tsunami’s damage to buildings and infrastructures

Regarding the study on the damage to building materials caused by a tsunami inundation depth, in the literature on past Japanese tsunamis, a tsunami inundation depth of 2–4 m would completely demolish wooden structures, 7 m for brick structures, and 20 m for reinforced concrete building structures (Shuto 1993; Suppasri et al. 2012). According to the literature on the 2004 Indian Ocean tsunami, a tsunami inundation depth of 3 m would destroy light constructions on wood or timber without any design structures, 6 m for brick not reinforced masonry, and 7 m for brick with reinforced column and masonry filling (Valencia et al. 2011). Egyptian tsunami literature inferred that an inundation depth of 3 m would utterly destroy light constructions structures, 8 m for brick houses structures, 9 m for brick houses with some reinforced structural elements structures, and 12.5 m for reinforced concrete structures (Pagnoni et al. 2015). Therefore, the degree of damage depends on the inundation depths for different building materials. An inundation depth of more than 2 m completely destroys light-frame wooden structures; an inundation depth of more than 6 m and 12.5 m completely destroys brick house structures and reinforced concrete structures, respectively. It is inferred that reinforced concrete structures are the most tsunami-resistant building materials.

Besides, many other factors should be also considered in tsunami damage assessment for buildings. For example, a building with three or more stories is better than single-story building, and structures with reinforced concrete are the best tsunami-resistant construction. Also, open plan home design with deep foundations (compared to shallow ones) and open-breakable accesses (such as doors) can survive the forces of a tsunami wave. Besides, the extent of damage from polygon buildings (e.g., hexagonal, triangular, rounded, etc.) is less severe than rectangular-shaped, “L-shaped,” “T-shaped,” or “X-shaped” buildings. And those buildings closest to the coastline have risks of impacts from those floating objects like vehicles or vessels washed away by tsunamis. Also, natural barriers and breakwaters can reduce the impact of tsunamis (Angela et al. 2014; Doll’Osso et al. 2009; Doll’Osso et al. 2010; Ines et. al. 2015; Leelawat et al. 2014; Papathoma and Dominey-Howes 2003; Suppasri et al. 2015; Takagi and Jeremy 2014; Izquierdo et al. 2018). In our analysis of the building vulnerability caused by tsunamis, the building vulnerability of residential structures, which are located near coastlines, is the highest. The wharf structures are also vulnerable to tsunamis, so many tourists and local residents will be in danger when taking the ferry between cities (Doll’Osso et al. 2009; Dominey-Howes et al. 2010).

Most oil storage tanks are safe when the tsunami inundation depth is below 2 m; for 2–5 m, piping is damaged; over 5 m, most oil storage tanks will be washed away (Hatayama 2014; Ahmed et al. 2016). When the height of tsunami exceeds 14 m, the breakwater width less than 8 m will be severely damaged. When the height of tsunami is less than 6 m, the breakwater width greater than 14 m will not be affected (Takagi 2015).

4 Survey

4.1 Critical infrastructure

  1. (1)

    Oil storage tanks Taiwan lacks energy sources, relying on imports for 98%, of which crude oil and petroleum products account for half. They are imported by ships and transported to various storage tanks at ports with pipelines. There are 14 oil storage tanks at Keelung Port, with a total volume of 15,500 kiloliters. The average height of the oil storage tanks is 13 m and the average diameter is 10 m. The monitoring center maintains 1 person on duty for rotation 24 hours a day.

  2. (2)

    Large loading/unloading equipment Large loading/unloading equipment is required to carry out lifting operations for cargo ships at ports. The cargo tonnage of Keelung Port in 2019 was 60,050,195 tons and the container capacity was 1,455,293 TEU. Keelung Port has 30 bridge cranes and 4 portal cranes.

  3. (3)

    Wharves There are 56 wharves in the Keelung Port, including 15 container wharves, 2 oil wharves, 4 passenger wharves, 19 bulk cargo wharves, and 16 non-operating wharves. The wharf structures are categorized into “specific,” “A,” “B,” and “C” level. The reinforced earthquake-resistant wharves are categorized as “specific” level. If a wharf needs to facilitate reconstruction after an earthquake, its structure requires “specific” level. A specific-level structure must resist major earthquakes or tsunamis and withstand horizontal impacts of tsunamis. So, after an earthquake occurs, people can quickly evacuate from the wharf area and the post-earthquake transportation can be efficient. However, the Keelung Port only has “A” and “B” level of wharves without “specific” level.

  4. (4)

    BuildingsThe structure of port buildings is either RC or SRC, and most of buildings are warehouses. The shape of warehouses is rectangular, and the warehouse buildings have single or two stories. So, the warehouses are not tsunami resistant. When the inundation depth rises to a maximum of three meters and people have no time to evacuate to somewhere outside the port, people in inundation area should be evacuated to higher floors (higher than the third floor) of the on-site vertical shelter facilities. We find that there are 47 buildings in the potential inundation are at Keelung Port: 25 buildings have single or two stories and 22 buildings have more than three stories. Also, there are one building with maximum inundation depth of less than 0.3 meter, 14 buildings with maximum inundation depth of 0.3–1 meter, and 32 buildings with maximum inundation depth of 1–3 meters. One of important buildings in the port area is the five-story tourist center with a shape of rectangle. This tourist center is where tourists embark, and its potential inundation depth is from one to three meters.

  5. (5)

    Breakwaters Taiwan’s breakwaters are not designed for tsunamis. The total length of the eastern breakwater at Keelung Port is about 1280 m and the western breakwater is about 820 m (Ho et al. 2014). The caisson gaps of the eastern breakwater are too large and misaligned. In the basic stability analysis, the fact that the eastern breakwaters were finished in different years is added in our paper. The widths of three caissons and three locations of breakwaters are different, and the three eastern breakwaters can withstand the tsunamis with wave height of 3.44, 5, and 6.54 meters, respectively (Ho et al. 2016). Thus, the tetrapods are placed in the area where the width of the caisson is the smallest to increase the safety factors. Besides, according to the literature, breakwaters are effective in blocking the tsunami wave height and delaying the rise of the water level (Chen 2011); the design of breakwaters is similar to NOAA et al. (2001) concepts for disaster reducing capabilities during a tsunami, such as slow water currents, steer water forces, and block water forces.

4.2 Tsunami warning facilities

After receiving seismic data from various regions, the Pacific Tsunami Warning Center (PTWC) assesses the probability of a tsunami and then sends warnings to the regions along the Pacific coast with estimations of the arrival time and wave height of the tsunami. The Central Weather Bureau (CWB), receiving a tsunami warning from the PTWC, would issue a tsunami alert with a 6-h estimated arrival time to Taiwan and a tsunami warning with a 3-h estimated arrival time. Based on the tsunami alert/warning from the CWB, Port of Keelung Taiwan International Ports Corporation (TIPC) calculates the estimated arrival time of a tsunami at Keelung and its wave height, and timely inquires the latest warning information from the Keelung Weather Station to reduce possible casualties.

4.3 Off-site tsunami evacuation

The off-site tsunami shelter facilities are a kind of shelter facilities established by the government of Keelung City. This study calculated that the average time from the Keelung Port to the 10 nearby shelters and the appropriate paths which people have enough time to escape through are chosen (based on the most threatening time of 58 minutes from the tsunami source in the Manila Trench as seen in the simulation). While the Cabinet Office of Japan (2005) suggested that the average walking speed of the crowd is about 0.88–1.29 m/s, we estimate that people can walk from Keelung Port to the 10 nearby shelters around 8 to 44 minutes. This shows that before the arrival of the first wave of tsunamis, port administrators and longshoremen have enough time to walk to the 10 high grounds or shelters outside the port at an altitude above 20 meters.

While people walks from Keelung Port to the nearby shelters (from 8 to 44 min) after the government starts to evacuate people, there is something that has not been considered, such as securing the vessels and positioning the containers. If the emergency response groups cannot escape to the off-site tsunami shelter facilities in time, or if vessels cannot be moved out of the port immediately, the emergency response groups and the tourists in the inundation area should evacuate to the nearby 22 buildings with more than three stories.

Therefore, there are ten off-site tsunami shelter facilities. However, if people in the inundation area cannot evacuate to these ten locations, 22 buildings with more than three stories can be alternatives to shelter facilities for people to evacuate (Fig. 3).

Fig. 3
figure 3

Tsunami evacuation directions and locations of shelters for Keelung Port

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5 In-depth interview

The purpose of this interview is to select the critical infrastructure of Keelung Port and propose countermeasures for tsunami prevention and disaster relief.

5.1 Interviewee

The interview outline of this study was prepared in advance. The interviewees amount 16 people are senior manager, who ever participated in Port Tsunami Response Division, including three categories, port managers (Port of Keelung TIPC), port lessees (oil tank industry, loading and unloading industry, and shipping industry), and governmental disaster prevention (marine patrol, police, and fireman). We went to their working site and had interviews with each of them.

In-depth interviews are semi-structured interviews that collect information through in-person conversations, allowing interviewees to freely articulate their views. The 2011 Great East Japan Earthquake was one of the more important tsunami warnings in recent years as it was the first tsunami warning issued in Taiwan. First, interviewees were asked to look back on the 2011 Great East Japan Earthquake and tsunami and candidly describe domestic or international tsunami strategies that may prove valuable for disaster prevention and relief measurements in Taiwan. The interviewees were then gradually led to the research topics in order to analyze and comprehensively explain the research questions and provide specific operational strategies based on their respective experiences, backgrounds, and professional knowledge.

5.2 Outline of design

  1. 1.

    Port managers and port lessees: The outline of the visit includes strategies for critical infrastructure at the Port, the current conditions and strategies of the Port’s tsunami preparation, and strategies for the BCP of the Port.

  2. 2.

    Governmental disaster prevention agency: The outline of the visit includes strategies for the post-tsunami search and rescue system and strategies for the system of handling mass casualty incident after a tsunami

5.3 Interview summary

The recorded conversation during the interview and a survey of literature collection are summarized as follows:

  1. (1)

    Critical infrastructure.

 

Summarized strategy interview records

Oil storage tanks

The main bodies of oil storage tanks were regularly inspected, closed-circuit monitoring systems were widely set up, and there were daily shifts. The area joint prevention and control mechanism coordinated nearby human and material firefighting resources

Large loading/unloading equipment

Bridge cranes are capable of withstanding force Gale (equivalent to the wind speed of 17.2 m/s of a mild typhoon). In the face of tsunamis, they are moved and secured to piles and then reinforced with steel cables

Wharves

Currently, the design of some new wharves has taken into consideration the impact of disasters such as earthquakes and tsunamis by enhancing loading capacity and increasing structural strength

Buildings

1.Seismic reinforcement measures of the buildings are periodically evaluated

2.If the inundation depth reaches 3 m, “the impact on the company includes two levels of containers (2.9 m for each level), the first floor (4.5 m high) of the office building, and the warehouse” one employee from loading and unloading industry said

Breakwaters

The breakwaters are mostly gravity-type structures that break down partially when damaged, which should still be effective in terms of blocking waves and the static stability of the Port

  1. (2)

    The current conditions and strategies of the Port’s tsunami preparation.

 

Summarized strategy interview records

Rapid emergency response groups

Keelung Port receives a tsunami warning issued by the CWB. If the Port is within the warning area, a dedicated rotating staff of the monitoring center will notify members of the tsunami emergency response team to station themselves and promptly assign contingency responsibilities such as emergency repair, control, evacuation, and notification

The implementation of disaster prevention education and drills

Through the combination of disaster prevention training and self-defense fire drills, all those responsible can fully understand the mechanism of tsunami warning issuance and cancelation

Diverse tsunami warnings and information communication

Port of Keelung TIPC, disaster prevention and relief units, port lessees and docked ships, etc., are notified via line, group chats, broadcast and wireless intercom, and other means, so that the outdoor staff at the port can obtain tsunami information

Reviewing the veracity of tsunami warning signs

Tsunami warning signs are often ineffective due to negligence, such as the insufficient evacuation direction and location information

Effective off-site evacuation plans

All non-responsive personnel are evacuated to other places outside the port

Effective on-site vertical shelter facilities

East Japan’s experience with tsunamis revealed that many tsunami shelters were inundated due to insufficient building heights. As a result, the Port of Keelung TIPC installed the vertical emergency shelter (which is in the same building as the tourist center) and important systems for communication and information on its highest floor

Emergency evacuation for ships

Dangerous container ships and oil tankers enjoy top priority for emergency departure. For ships that fail to leave the Port in time, there are measures to prevent collision and increase the number of cables

The use of technology to monitor facilities to stay on top the situation

Port surveillance facilities include lighting, security guards, and CCTV surveillance equipment. For the monitoring of tsunamis, apart from the tsunami warning issued by the CWB, regular long-term monitoring of the initial changes of sea level under the breakwater precludes damages from sudden surges or shallow earthquakes offshore

  1. (3)

    Strategies for the BCP of the Port.

 

summarized strategy interview records

Core business priorities and repair goals

If important infrastructures, such as waterways and wharves, were damaged, the maximum limit of the service interruption that the loading and unloading industry could withstand can be no more than 1 week

Emergency transportation routes

In case of road destruction, tanker trucks would be unable to gain access for loading/feeding

Suppliers are contacted to assist in resource recovery

When operations are completely paralyzed after a tsunami, ships would be notified to dock at other commercial ports

Remote backup locations

Other than the Keelung Port, the loading and unloading industry has other bases in other ports of Taiwan

An emergency supply of water, power, and oil

Tsunamis damage power and water supply facilities. Port of Keelung TIPC notifies power and water supply services for emergency repairs

Risk communication

Port of Keelung TIPC builds an exclusive corporate social responsibility Web site to communicate

  1. (4)

    Strategies for the post-tsunami rescue and mass casualty incident system.

 

Summarized strategy interview records

Search and rescue system

1. The Great East Japan Earthquake caused a tsunami, fire, and nuclear power plant accidents to occur at the same time. A single affected prefectural and city government may not be able to respond timely, and there is a need to prepare for long-term disaster relief

2. The equipment required for search and rescue operations should, in principle, be carried by the agency responsible for the operation, and technology can also be used to assist in disaster relief

The system of handling mass casualty incident

The fire department will notify the public health bureau to initiate the mass casualty protocol, which dispatches paramedics and ambulances to the scene, notifies hospitals to be prepared to receive the victims and, if necessary, request nearby public health bureaus for assistance

6 Research findings

6.1 Disaster resistance factors against tsunamis for the Keelung Port

Through in-depth interviews with port managers, port lessees, and governmental disaster prevention and relief agencies, we summarize our interview as follows. First, we conclude that there are 21 disaster-resistant factors against tsunamis, and these factors belong to four major aspects, including (1) reinforcing essential port infrastructure, (2) strengthening early warnings for evacuation and information communication, (3) enhancing disaster relief and rescue performance, and (4) promoting BCP. First of all, the first category centered on reinforcing essential port infrastructure and avoiding tsunami damages, including oil storage tanks, large loading/unloading equipment, wharves, buildings, and breakwaters. The second category focused on strengthening early warnings for evacuation and information communication, including diverse tsunami warnings and information communication, reviewing the veracity of tsunami warning signs, effective off-site evacuation plans, effective on-site vertical shelter facilities, emergency evacuation for ships, and the use of technology to monitor facilities to stay on top the situation. The third category focused on enhancing disaster relief and rescue performance of the port, including rapid emergency response groups, the post-tsunami search and rescue system, the system of handling a post-tsunami mass casualty incident, and the implementation of disaster prevention education and drills. The fourth category was the BCP that recovers the basic operations of the Port as soon as possible after a disaster, including core business priorities and repair goals, emergency transportation routes, contact with suppliers, remote backup locations, an emergency supply of water, power, and oil, as well as risk communication (Fig. 4). In future, these resistance factors will be strengthened to maintain a certain level of resistance.

Fig. 4
figure 4

Disaster resistance factors against tsunamis for the port

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6.2 Identified problems

The 2011 Great East Japan Earthquake triggered unprecedented tsunamis and caused an unparalleled compound disaster. As the premier international commercial port in Northern Taiwan, the Keelung Port requires vigilance for its tsunami response strategies. Therefore, through surveying and in-depth interviews, this study found the following potential problems at the Keelung Port.

Regarding preparations for the Port’s critical infrastructure, none of the wharves of the Keelung Port currently meets the standard for the specific life-saving wharf. It is recommended that wharves with a large crowd such as those with oil storage tanks and visitor centers be upgraded to certain life-saving wharves. Wharves are subject to huge ground vibrations, followed by the severe impact of tsunamis. Specific life-sustaining wharves are designed for major disasters such as earthquakes and tsunamis with higher resistance to the horizontal impact of tsunamis, while maintaining the basic requirements for sea transportation. Additionally, the east breakwater that was completed in 1981 and 2010 has been found to have caissons with overly large gaps and misalignments. On regular days, there is no immediate danger, but we should increase the safety factors of sliding and overturning to reduce the impacts of tsunamis (Lee et al. 2015).

Consider preparations for strengthening early warnings for evacuation and information communication. (1) Since the tsunamis have different amplification effects due to different coastal terrain (Lra 2013), it is advised that the Harbor and Marine Technology Center develop a quick tsunami calculation system for international commercial ports to evaluate the inundation depths, ranges, and maximum wave heights for different wharves. This would be incredibly beneficial for the initial contingency measures before the arrival of the tsunami, such as contingency teams, ways and locations of evacuation, fixing and evacuation of items and equipment. (2) It is necessary to set up a sea-level monitoring system. Sea states of various harbors are available for enquiry on the Harbor Environment Information Web site. Tides and waves are non-real-time data with hourly updates, making it impossible to be promptly informed of threatening surges and swells. Therefore, it is recommended that the monitoring center of the Keelung Port be connected to the system for timely information, such as frequent tidal updates and warnings on abnormal sea-level changes.

With respect to preparations for enhancing disaster relief and rescue performance, the Port needs to prepare for long-term disaster relief. Sufficient training is the key to survival. Only with sufficient training, familiarity with the response protocols, disaster awareness, and skills for and knowledge about tsunamis on ordinary days can people respond properly and work together to evacuate in an orderly manner. Governmental disaster prevention and relief agencies should learn from disasters, and break up and reintegrate existing frameworks. Therefore, establishing a wide-area disaster prevention system with modular resource dispatching is the goal. Group responsibilities, personnel, and meeting points are planned. In a tsunami event, the central government is requested to require nearby counties and cities that are not affected by the tsunami to assist in disaster relief.

Regarding preparations for the promotion of BCP, a tsunami may bring about large-scale devastating disasters, and various post-disaster response tasks will face challenges. Port of Keelung TIPC should establish a clear, long-term strategy that assesses the impacts of disasters on core businesses in order to ensure business continuity within the maximum allowable interruption. In Taiwan, large enterprises are often expected to fulfill their social responsibilities and have independent disaster relief capabilities. Thus, Taiwan’s commercial ports have police and firefighting bases in place, specializing in port security and emergency services, rendering enterprises as agents for their own disaster prevention and relief. Leakage, fires, and explosion of an oil storage tank pose a life-threatening danger to oil storage tank operators, port companies, and residents of neighboring communities. If oil storage tanks could be incorporated into the Port’s critical infrastructure and listed as a key project for annual supervision, diversification, and improvement on transportation, life support system and risk communication would become possible. Oil storage tank operators would gain a better understanding of the disaster effects on transportation, life support system, supply chains, and stakeholders such as employees and customers. With the knowledge come specific measurements, such as disaster area joint prevention mechanism, evaluation of the main supply chain support mechanism, and remote backup bases. Consequently, the focus of disaster relief on the continuous BCP operation will be able to reduce the impact factors that interrupt operations in a tsunami event. As shown in Fig. 4, its resistance factors are related to the other three aspects. Therefore, the goal is to create senior manager’s crisis awareness of disaster prevention, educate businesses about the concept of disaster prevention, and budget for disaster prevention and preparation. In order to achieve this goal, it is suggested to promote BCP as the core of the “golden triangle” formed by reinforcing critical infrastructure, strengthening early warnings for evacuation and information communication, and enhancing disaster relief and rescue performance (Fig. 5). Then, no matter how one observes the triangle, BCP will always be intrinsic to the operation. Therefore, this golden triangle model is established as the core of promoting business continuity plan to solve the potential problems of tsunami impact at Keelung Port.

Fig. 5
figure 5

The golden triangle of the four major aspects

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6.3 Strategies

6.3.1 Strategies for critical infrastructure at the Port

  1. (1)

    Oil storage tanks The strategy of improving the stability of oil storage tanks involves lowering the oil level in the oil storage tank, increasing the weight of the ring foundation, increasing the weight of the outer ring foundation, installing emergency piping shut-off valves, or shutting off the source in advance, so as to prevent a large amount of leakage.

  2. (2)

    Large loading/unloading equipment In fact, if a tsunami hits the container wharf at the outer Keelung Port, bridge cranes and portal cranes will not be destroyed at the same time because they are located in different areas. The impact of tsunamis involves the direction of tsunamis, barrier protection, the water depth of wharves, the datum levels of wharves, and the bridge cranes being moved inland, and thus, the inundation depths are different due to various factors. Therefore, not all of the bridge cranes or portal cranes will be damaged because some of them are away from the disaster-affected area and are not destroyed by the tsunami.

  3. (3)

    Wharves To maintain shipping operations, the wharfs’ seismic resistance has to be greater than that required for the design (strength, displacement, etc.) for the forceful impact of a tsunami. Therefore, the seismic strength of Keelung Port wharves is designed to be 1.5-fold that of the standard for port structures considering the magnitude of earthquakes that recur every 2,450 years (Lia et al. 2012). Also, a water-level gauge should be installed at the wharf to detect changes of sea level in a timely manner.

  4. (4)

    Buildings Normally, the conditions, locations, and number of buildings should be recorded. The conditions of buildings include number of stories and earthquake-resistant structures warranty; the locations of buildings include the numbering of wharves, the distance from the coastline, and the risk of buildings being hit by large floating objects; and the number of buildings is restricted in the inundation area. Besides, if a new building is constructed in the future, the building will have more than three stories and will be constructed by reinforced concrete or steel-reinforced concrete, and the first floor should be used as a parking space. This will increase the open access and reduce the impact of tsunamis.

  5. (5)

    Breakwaters Since the breakwaters concern the effects of tsunami wave height and impact, Port of Keelung TIPC should dispatch personnel to inspect and fortify the breakwaters, so that the safety factors for the sliding and overturning of the caissons of the breakwaters are above particular safety standard. Alternatively, tetrapods may be increased, or the port surfaces inside the breakwaters may be reinforced. A water-level gauge should also be installed to measure the change of sea level.

6.3.2 Strategies for early warnings of evacuation and information communication at the Port

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    Diverse tsunami warnings and information communication For areas with potential tsunami danger, 4G operators provide disaster prevention warning information services, the real-time traffic condition system offers tsunami information, TV news adds news tickers and station-break announcements at specific stations, radio stations have audio station-break announcements, and the Internet is prioritized.

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    Reviewing the veracity of tsunami warning signs To enhance tsunami warning signs, the signs should be installed close to the crowds such as tourist centers; the information displayed should include the altitudes of, evacuation paths, and directions to shelter sites. On regular days, the time required to walk to shelter sites according to the signs’ directions should be estimated (Ricardo et al. 2017).

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    Effective off-site evacuation plans To effectively avoid departure delays and uncertainty in transportation methods for the staff, Port of Keelung TIPC directly sends vehicles into the Port to expedite evacuation, while staff outside the port evacuate on foot. Evacuation guidelines are set up and emergency shelters of highlands at an altitude over 20 m to ensure staff safety.

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    Effective on-site vertical shelter facilities

    On regular days, communication and lighting equipment is fully prepared, emergency generators are ready, and disaster relief equipment is centralized and stored at a high place.

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    Emergency evacuation for ships

    The drop between the ground level and the sea level of Keelung Port is about 2–3 m, and ships may seriously collide with, or push onto, wharves due to a tsunami. Thus, when a strong earthquake (Mw≧7) with prolonged shaking happens, the monitoring center can prepare to notify ships to stand by immediately and prepare to sail to sea. Moreover, pilots would adjust safety distances based on the conditions at sea.

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    The use of technology to monitor facilities to stay on top the situation When a tsunami arrives, CCTV keeps track of what is happening at the premises (including oil storage tanks and vessels), and it enables you to monitor the tsunami inundation. After the arrival of a tsunami, drones can be quickly deployed over disaster zones, and the on-site images can be received by drone video streaming.

6.3.3 Strategies for disaster relief and rescue performance at the Port

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    Rapid emergency response groups The tsunami emergency response team’s first priority is to evacuate. Control and evacuation are implemented by governmental agencies such as the police and fire departments. Each group of contingency personnel operates optimally until the tsunami warning is lifted.

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    The post-tsunami search and rescue system The Port needs to prepare for long-term disaster relief; hence, a wide-area disaster prevention system to respond to major compound disasters is required. In addition, tsunami shelters, breakwaters, and other facilities should be strengthened. The disaster prevention and rescue resource database is regularly updated and categorized. Disaster prevention education and training are reinforced for a quick and safe evacuation system. In response to large-scale disasters, an advanced command post is set up to mobilize special rescue teams and rescue dogs in the jurisdiction and neighboring fire departments, disaster medical rescue teams, heavy machinery rescue forces, volunteer firefighters, disaster prevention groups, and the national army and other disaster relief personnel and equipment. Drones are used to search for trapped people on the ground, and robots are used for those in collapsed buildings. Mobile phone positioning is utilized for a list of possibly trapped and missing persons and assessment of the requirements of heavy equipment and disaster relief special personnel.

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    The system of handling mass casualty incident after a tsunami When the medical bases are damaged by a tsunami, crucial medical supplies and consumables are sent in as soon as possible. Nearby medical institutions are notified to stand by, and the national army are coordinated for support, and a large number of porters are mobilized to carry patients. The seriously injured are given priority to be transported to hospitals by ambulance, while those with minor injuries can be transported by large vehicles such as buses and trucks. Bodies should be carefully handled to preclude post-tsunami infectious diseases.

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    The implementation of disaster prevention education and drills Port of Keelung TIPC incorporates tsunami lessons into continuous civil defense education. Depending on the needs of the scale of the drill, volunteer firefighters, the national army, disaster prevention groups, and other available resources are invited to discover weaknesses in the disaster relief strategies.

6.3.4 Strategies for the BCP of the Port

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    Core business priorities and repair goals Based on the information provided by Port of Keelung TIPC, after a tsunami, the priorities are waterway clearance, and the recovery of lighthouse, wharf facilities, and information and communication systems. To avoid the impact of disasters on the operations of core business, prioritization is done regarding sources of risks that may lead to business interruption. Effective responses and rapid recovery measures are developed with the aim of continuous, acceptable operations; operations are resumed within a prescribed time. Backup (alternative) solutions and staff immediately available are secured, and improving disaster resistance of the Port is at the core of disaster prevention.

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    Emergency transportation routes Tsunamis’ damage to transportation facilities at a port has to do with to tsunami inundation depth, so it is critical to establish multiple transportation means and routes, combining land, sea, and air transportation. Roads for disaster relief should mainly be over 15 m wide. An inter-port support mechanism is built to notify nearby safe ports to assist in disaster relief or temporarily take over sea transportation in the disaster area.

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    Suppliers are contacted to assist in resource recovery To avoid the interruption of supply chains, a database of contingency processes should be established by working with suppliers to regularly figure out possible risks, and key suppliers should be identified to consider increasing supply sources or inventory. Also, logistics management must be done to improve efficiency across supply chains.

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    Remote backup locations To avoid damage to the critical infrastructure of the waterway and the wharves, which may seriously affect operations, all units should know about well indispensable equipment and information, especially the backup system for salient information, which has to be backed up remotely.

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    An emergency supply of water, power, and oil.For important buildings, the water pipes are mainly made of cast iron, self-provided water towers are self-sufficient, generators are also self-provided, and the oil for emergency vehicles and tools must be prepared.

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    Risk communicationPort of Keelung TIPC should continue to build a new model of port-city collaborations, including a wider range of stakeholders such as neighboring community residents, businesses and administrative agencies, and establishing channels for dialogues between stakeholders, improving information transparency, establishing benign interactive relationships, and increasing trust (Kim and Lee 2018).

7 Closing remarks

Each disaster results in unique consequences. This study on the disaster resistance of the Port concludes with the four major aspects centered on BCP, with each aspect composed of different resistance factors, for which operational strategies were obtained through interviews and discussions. The central government strengthens the rapid communication protocol for strong earthquake and tsunami warnings. TIPC Port of Keelung fortifies the seismic reinforcement of important infrastructures such as buildings, breakwaters, and life-sustaining systems, and actively promotes BCP. These strategies can serve as reference for Port of Keelung TIPC for disaster prevention and rescue policies to reduce the risk of disasters. Future studies regarding disaster-resistant factors should focus on the anti-tsunami stability for breakwaters, waterways, ships, etc., and present new tsunami disaster prevention measures.