Disaster Risk Management of Cultural Heritage in Urban Areas

Flood prevention and Mitigation Techniques, Lecture 11, International Training Course 2011
Instructor: Yoshifumi Satofuka | Duration: 80 minutes

As a result of this session, participants were introduced to the following concepts:

• Understanding of the types of floods that may occur in a country/ region.
• How to predict floods.
• How to mitigate the impact of a flood.
• How to protect historical buildings from the occurrence of floods.

The presentation highlighted through detailed diagrams and case studies the various types of floods as well as mitigation techniques. Diagrams are a simple graphical tool that helps participants retain the information introduced in the session.

The mechanism of a flood was explained.

Heavy rainfall over an extended period of time is one of the leading causes of large-scale devastation in various areas. In Japan, the configuration of the ground is very steep and the levels of precipitation are exceedingly high. In the events of fast falling and large-scale precipitation, extensive damage has occurred in the past, and is likely to happen in the future as well. Debris flow is one of the most dangerous phenomena in Japan. There has been extensive damage to life and property in a single event during the rainy season or as the result of a typhoon.

Floods may be classified into the following categories:

1. Flooding in a mild slope area.
2. Flooding in a steep slope area.

The various techniques to mitigate and prevent damage due to floods were listed:

1. Rainfall runoff control.
2. Flood control.
3. Drainage system development.
4. Land use regulation.
5. Anti-flood buildings and houses.
6. Hazard-maps and flood warning systems.

Monitoring systems for flood
Source: Yoshifumi Satofuka

Movement of soil as a result of heavy rainfall
Source: Yoshifumi Satofuka

Seismic Performance of Japanese Historical Structures, Lecture 6, International Training Course 2011
Instructor: Kazuyuki Izuno | Duration: 60 minutes

This lecture presented an introduction to assessment techniques, investigation into past history of risks and disaster and examination of methods used to assess damage to structures (discussed in Module 2). Based on detailed risk assessment techniques, the instructor also introduced mitigation processes for buildings to be able to resist seismic activity.

The successive stages of the risk assessment module were also briefly discussed through the example of the Kiyomizu Temple.

The session highlighted the need to carefully assess and mitigate risks at the site. He illustrated in detail the difference between static and dynamic ways of testing for seismic performance of buildings and also the advantages of dynamic analysis.

The three modes of disaster reduction for timber buildings in Japan were introduced, namely:

• Earthquake resistant design: Emphasis was laid on improving a building’s ductility to resist seismic movement. The addition of stable truss structures, hoop ties and steel jackets was discussed as a possibility.
• Seismic isolation: Lead rubber bearings and high damping rubber bearing examples were illustrated. Historic examples of seismic isolation were also discussed.
• Vibration control: Various kinds of dampers which may be used to control vibrations of a building during an earthquake were discussed. The viscous type, hysteretic type and friction type of dampers were introduced.

Each mode was discussed in detail with several examples from buildings in Japan.

Landslide Prevention and Mitigation Techniques, International Training Course 2011
Instructor: Ryoichi Fukagawa | Duration: 80 minutes

Examples of slope failures and monitoring and recovery systems in Japan were highlighted by the instructor. Different conditions were explained, and priority based interventions for prevention, mitigation and recovery were listed. As a result of this session, participants were explained the characteristics of slope failures caused by earthquakes and heavy rainfall, typical prevention and mitigation methods for slope failures and be able to understand the advanced techniques for slope failure monitoring systems.

In Japan, natural disasters such as typhoons, heavy rainfall, and heavy snow have occurred because of geographical, topographical and meteorological conditions. Because of this there is a high risk from natural disasters due to earthquakes, heavy rainfall, and typhoons.

The following aspects of landslides were highlighted:

• Differences between a landslide and steep slope failure.
• Characteristics of slope failures caused by an earthquake.
• Important items used to evaluate the safety of a slope in an earthquake.
• Characteristics of slope failures caused by heavy rainfall.

Typical methods of prevention and mitigation for slope failures

Control and emergency countermeasures including methods to control the movement of the slope by changing the natural conditions of topography, soil properties, and underground water flow, amongst others, were explained.

Slope stability monitoring systems in Kiyomizu-dera-temple (this case study was also part of a site visit made by the participants making it easier for them to relate to information). The work that the Geo-hazard Research group of Ritsumeikan University, which has been conducting field measurements in Kiyomizu-dera-temple in Kyoto was described briefly.

Stone wall damage investigation of Sendai Castle caused by the Tohoku-Taiheiyooki-Earthquake.

Field investigations have been carried out on damage to the stone walls of Sendai Castle caused by Tohoku-Taiheiyooki-Earthquake. The field investigations were conducted by mainly NSWS in-situ testing device, which is an improved device of the Swedish sounding test, and a three-dimensional laser scanning system.

Investigation of debris flow causing heavy damage to Kumano-Nachi-Taisha during Typhoon No.12 in 2011.

The secondary case example of typhoon No.12 in September 2011 was also used to illustrate slope analysis techniques. The typhoon caused severe damage to Kumano-Nachi-Taisha, one of the most significant shrines in the country. The shrine and its surrounding areas experienced record rainfall and the heavy rainfall resulted in the rush of debris flow and the failure of steep slopes. One of the debris flows damaged the Kumano-Nachi-Taisha. The geo-hazard group investigated the debris flow, especially the mechanical profile of the top, and carried out slope stability analysis using different technologies.

Reference:

Kazunari Sako, Ryoichi Fukagawa and Tomoaki Satomi (2011) Slope monitoring system at a slope behind an important cultural asset, Journal of Disaster Research, Vol.6, No.1, , pp.70-79.

Planning Process and Project Management; Environmental Water Supply System for Protection of Wooden Cultural Heritages from Post-earthquake Fire, International Training Course 2011, 12
Instructor:Takeyuki Okubo | Duration: 80 minutes

This lecture explained the planning process and management methods to develop an environmental water supply system (EWSS) for mitigating post earthquake fires. The concept of EWSS opens up possibilities for a sustainable water environment and the restoration of historical cities, maintaining beauty and safety for the benefit of future generations.

The methodology for developing EWSS was highlighted through the following steps:

• Research on characteristics of the region.
• Study of development strategies.
• Development and operational planning of the water system.
• Evaluation of the maintenance plan.

The following secondary case examples of projects and management methods were used to supplement the lecture:

• Use of Rivers and Waterways for the Emergency water supply system of Shirakawa, Ono-gun, Gifu.
• Use of Waterways and Underground Water for the Emergency water supply system of Kanazawa, Ishikawa.

This lecture stated the need of practical planning for the optimum usage of various kinds of natural water in the Kiyomizu area to develop (EWSS) for disaster prevention. Such uninterrupted water supply systems could be used for fire prevention in historic cities that have a substantial number of wooden structures and thus preserve the historic urban environment.

Structural Vulnerability and Capacity of Historic Buildings in Patan Area and their Seismic Retrofitting Techniques, International Training Course 2009. Site: Patan, Kathmandu Valley
Instructors: Kai Weise, Prem Nath Maskey, Rohit Jigyasu, Rohit Ranjitkar | Duration: 60 minutes +180 minutes

Reducing Disaster Vulnerability of Traditional Housing

The workshop intended to introduce the participants to the basic methodology for the structural vulnerability assessment of traditional buildings in the historic town of Patan in the Kathmandu Valley, and applying this to the case study buildings. Each group was given specific structures in Patan. Each group collected data necessary to evaluate the structural condition and seismic performance of traditional buildings. This would include general characteristics, principle materials used, structural systems, building type, use and nature of occupancy, and architectural features that might affect seismic performance.

The groups then evaluated the structural vulnerability of the building. This included the load path system of the building, geometry, condition and performance of individual building elements, vertical discontinuities, mass of the building, openings in walls, characteristics of adjacent buildings and strength related evaluation. Weak and soft stories were identified in structures that may pose a serious risk to the building’s safety in the event of an earthquake. Adjacent structures were also documented for their potential impact. A tentative proposal for strengthening the building using traditional material and technology was prepared. Each group presented their findings followed by group discussion.

Study on The Tombs of Buganda Kings at Kasubi Tombs, Uganda, World Heritage Site, International Training Course, 2011
Participant: Remigius Kigongo

Background

The Kasubi Tombs in Uganda are a series of four tombs of the Buganda Kings inscribed as a UNESCO World Heritage Site. The unique architecture of the tombs set it apart as a cultural masterpiece associated with high intangible heritage value. The site is exposed to development pressures and is highly vulnerable to earthquake, wind, and fire. The structures constructed in traditional materials such as wood, grass, reeds and fibres are especially vulnerable to fire.

The participant focused on mitigating and reducing disaster risks to Kasubi tombs through organization, people and facilities as outlined below.