Bengkulu City Community Adaptation of non-engineering structure development in swampland based on earthquake disaster risk reduction

Proceeding of SustaiN 2014 ISSN: 2188-0999

Disaster Preparedness, Management and Recovery

19-20 November 2014. Bali, Indonesia

161

The 5th Sustainable Future for Human Security (SustaiN 2014)

Bengkulu City Community Adaptation of Non-Engineering Structure Development in Swampland Based

on Earthquake Disaster Risk Reduction

Muhammad Fauzia*, Dwi Setyawanb, Budhi Setiawanc, Ridhah Taqwad aCivil Engineering, Bengkulu University. Kandang Limun street, Bengkulu, He is currently undertaking his PhD Program at

Environmental Science, Sriwijaya University. bSoil Science and Environment Science, Sriwijaya University. Padang Selasa 524 street, Bukit Besar, Palembang 30139,

Indonesia cCivil Engineering and Environment Science, Sriwijaya University

dSocial Science and Environment Science, Sriwijaya University

Abstract

The earthquake has caused many casualties and property loss. The public’s understanding of the risks of living in an earthquake prone area, such as the city of Bengkulu, is very important especially for areas with low soil bearing capacity such as marshland. This study aims to determine the form of adaptation that public has made on wetlands in order to minimize losses due to earthquake engineering and social approach based on Disaster Risk Reduction. This study uses purposive sampling method to decide the location of the study and random sampling method to choose the sample. The research that has been conducted is an effort to adaptation based Disaster Risk Reduction by the community, namely the construction of buildings in terms of adaptation and behavioral adaptation. Adaptation in terms of construction includes basic soil structure improvement, adaptation to the foundation, and adaptation to the type of roof used. In addition, this study has formulated an assessment of the modest house on wetlands. Assessment is designed to enable the public to judge for themselves the Non Engineering Structure they owned. This assessment is a spreadsheet with the final result of a category of the simple earthquake-resistant construction of their homes, whether it is appropriate (green color), less appropriate (yellow), or does not fit (red). Keywords : simple house, adaptation, Disaster Risk Reduction

1. Introduction

Swamp area in Bengkulu Province covers 12,411 ha consisting of 11,609 ha lowland heath and bog ebb and flow of around 802 Ha (BPS Bengkulu Province, 2010). Despite the fact that the area has low carrying capacity, the settlement in such this marshland increases, and it creates an insecurity. Given the Bengkulu province at quake 4 territory, it is vulnerable to major earthquake disaster. The real evidence is the big earthquakes on June 4, 2000 at magnitude 7.3 on the Richter Scale (SR) to the position of the epicenter located around 60 km below sea level. In the aftermath, 93 people were found dead, 2065 were injured, ± 40 thousand buildings and residential homes were

* Corresponding author. E-mail address: [email protected]




162

damaged (Zen, 2003). In addition, a large quake also occurred on 12 September 2007 with a strength of 7.9 on the Richter Scale (SR) and the epicenter was 10 km below sea level with 14 people dead, 38 people injured, and ± 21 thousand housing residents damaged (Satkorlak North Bengkulu, 2008).

An important lesson from this tragedy is the importance to reduce the risk of danger (hazard mitigation) and to increase the level of security (survival rate) through improvement of housing and residential environment and environmental engineering. Building damages and casualties due to earthquake disasters can be reduced by way of adapting to the environment where our people live. Adaptation within the question is how communities adapt grammar residential neighborhood with environmental condition which is very prone to earthquake hazards. It incorporates excellent efforts and an attempt to minimize the occurrence of damage to the construction of buildings and to reduce fatalities.

2. Basic Theory

2.1 Land Use

In general, the use of land in Indonesia is the real result of a long process of continual interaction, a balance, as well as the dynamic state of the population between activities on land and limitations in the surroundings where they live (As-syakur, 2010). Increasing land use by humans such as for a place to stay or to do business in compliance with public access and other facilities will cause a narrowing of available land. The issue of environmental degradation will affect the balance of the ecosystem. This is due to the use of land which does not consider the ability, carrying capacity and shape designation of the land, as for the example is wetlands (Pewista, 2013). The area of wetlands decreases as people put up buildings thereon, which is apparently with high risk of getting easily damaged during earthquake since they are built above swamp.

2.2 Wetlands

According to the Ramsar Convention (1991), wetlands is an area of brackish, swamps, peatland or water area, whether natural or artificial, permanent or temporary (provisional), with water flowing or stationary, fresh, brackish or salt, including the region with marine water the depth of which at low tide (low tide) does not exceed 6 meters. Indonesian Government Regulation No. 27 Year 1991 about the Swamp mentions that swamp is the land that is naturally waterlogged continuously or seasonally since natural drainage is impeded and has specific physical, chemical, and biological characteristics.

2.3 Building

House is defined as a building that serves as a home or residence and means of family building. In house building, there are one or several bedrooms, livingroom, bathroom, toilet, and kitchen which are fully interconnected to each other. Based on its construction, home building consists of permanent and semi-permanent home. Permanent home means a home that is constructed with foundation, brick walls, a roof and a floor. In addition, the construction of permanent housing is made of concrete, stone and steel (Puspantoro, 1996).




163

According to Supribadi (2002), components of the structure constitute the main component because it serves to support the load, either vertically, horizontally or self-weight of the building. The structural components consist of: 1. Sub Structure

Sub structure is the part of the building which is located at the bottom floor of a building or part that is in the soil, such as concrete blocks (sloop) and foundation (Supribadi, 2002). The lowest part of a building is intended to hold the entire weight of the building on the foundation. It includes its own weight and the weight of soil directly above the foundation.

2. Upper Structure Upper structure is the part of the building that is located on the top floor surfaces such as walls, columns, doors, windows, ring beam and roof truss and its parts (Supribadi, 2002). These structures must be able to guarantee the top in terms of safety and comfort. Therefore, the materials used in this building have design criteria; among others are strong, fire resistant, durable for long term use, easy to obtain and set up, and economical (easy maintenance).

2.4 Adaptation and Mitigation of Earthquake Disaster

Adaptation is necessary in order to anticipate the effects of catastrophic disasters in various fields and to minimize the negative consequences of the disaster. According to Law Number 21 of 2008 on the Disaster Management, disaster mitigation is a series of efforts to reduce disaster risk, both physically and through the development of awareness and capacity building facing the threat of disaster. Each region has a way of mitigation and adaptation to different disaster strikes, such as earthquakes. An earthquake is a disaster that often occurs in Indonesia. This is because many regions in Indonesia are adjacent to the active fault zone. When efforts to predict earthquakes have not shown positive results, the best effort in anticipation of the earthquake is the mitigation and adaptation to the environment.

In order to carry out disaster risk reduction, the public must have a strategy. The strategy is a tactic intended to align the order of life in response to the situation of residence which is prone to earthquake (adaptation). This tactic is a way for the community to avoid or minimize the threat of the elements at risk. Having tactics in dealing with situation such as this is mandatory to achieve a peaceful life. For example, if the death toll n the earthquake is largely due to falling building / house collapse, then the act of adaptation is to build homes that will stand in earthquakes. For people who have not been possible to build earthquake-resistant housing with the construction standards of earthquake resistance, then the choice is to build a simple earthquake resistant houses with materials from wood or bamboo (Hardoyo, 2011).

According to Susetyo (2006), learning can mitigate through school, as well as directly to common people. For the general public, mitigation incorporates several stages, namely pre-disaster stage, disaster or emergency stage, and post-disaster phases.

3. Research Method

The research location was chosen based on purposive sampling method by taking into account various considerations and conditions as well as the state of research areas. As for the determination of the sample using random sampling methods, it took into account predetermined criteria.




164

3.1 Primary Data

The primary data were obtained by dealing directly against the object to be carried out by means of observation, interviews and distributing questionnaires to the respondents who were in the study site. Questionnaires were filled out by a surveyor through a direct interview with the respondent. Surveyors came directly to the houses selected as a sample and then explained the respondents about the items that they had to answer. Each house was given one questionnaire.

In this study, the population is the simple house that has a permanent construction and is built on swamp land at the study site. The number of respondents that should be qualified as minimum sample size was calculated based on the number of houses built on swamp land. The number of non-engineering structure built on swamp land is shown in Table 1.

Tabel 1. Data on the number of houses built on swamp land

Number

Sub-district The Number of Non Engineering Structure built on swamp land

(x) 1. Muara Bangkahulu 4037 2. Sungai Serut 4350 3. Ratu Agung 3277

Total (6 ) 6 x = 11664 Siregar (2010) states that the technique to determine the size of the total sample population is

known by using the Solvin formula. The reason of using this formula is to obtain a sample which is representative, more certain or near existing population.

¸¹·¨

©§�

21 eN

Nn (1)

Where as: n = Minimum sample of house built on swampland N = Number of population groups in the swamp land e = Percentage of research leeway because of sampling error (0.10) and

the 90% confidence level

Based on the number of houses built on swamp land shown in Table 1., equation (1) can be performed on a total sampling as follows:

sample15,9910116641

11664

1 22

�

�

¸¹·¨

©§¸

¹·¨

©§eN

Nn

Therefore, the number of sample taken is 100 sample respondents. The other way to calculate the number of samples to be taken is to use a sampling technique called unit sample fraction (fi) ie for each sub-population as the multiply factor. The total sample fraction is adjusted for the strata. Fi value is calculated through the following calculation:

The amount of per-stratum sampling fraction is:




165

iN

Ni

f (2)

The amount of per-stratum sub sampling fraction is: n

if

in u (3)

Where as: fi = Sampling fraction stratum. Ni = Number of individual elements contained in the stratum population. N = Number of individuals in the entire population. n = Number of members included in the sample. ni = Number of members included in the sub-samples per stratum.

The total sample of respondents is shown in Table 2:

Table 2. The total sample of respondents Number Sub-District The total sample (houses)

1 Muara Bangkahulu 35 2 Sungai Serut 37 3 Ratu Agung 28

Total (6 ) 6 x = 100

3.2 Secondary Data

The secondary data were collected through the study of literature from several books related to building materials and home structures in terms of the concept of earthquake resistant houses. Additional data were collected from various agencies, including JICA data, Bappeda Provinsi Bengkulu and BPBD (Regional Disaster Management Agency), PU, BPS, and some other sources from both printed and web-based materials.

4. Result and Discussion

According to Wikantiyoso (2009), disaster mitigation efforts in the perspective of spatial planning can be done by performing the process of anticipation not only by creating a comfortable environment but also by formulating the potential disaster and mitigation strategies. Conceptually, mitigation includes: 1. Architectural Design

Taking into account the principles of structural strength, avoiding vertical discontinuities, designing non-structural elements.

2. Preparing the Community Social Public awareness (social readiness) of the social aspects of disaster (warning systems, anticipation and response time of the disaster and post-disaster management, etc.). Survey research done in three districts in the city of Bengkulu showed a variety of answers from

the community as reflected in the answers of the respondents in the questionnaires. Answers from the public can provide a hint of adaptation measures of the local communities in the face of the earthquake. The steps or local adaptation strategies in the face of the earthquake, among others:




166

4.1 Construction Adaptation

There are two kinds of mitigation efforts according to Ishikawa (2002): structure mitigation and non-structure mitigation. Mitigation efforts in the form of the structure is the building and strengthening of infrastructure potentially affected by the disaster, such as making structural engineering and construction to hold and strengthen the building or build an earthquake retaining structure. Besides, avoiding the disaster area to anticipate the impact of disasters (through consideration and calculation of construction).

Forms of adaptation in terms of earthquake-resistant construction which have been done by the community, based on the questionnaire answers, are as follow: 1. Soil Structure

Subgrade structural repairs have been done by the community. The data demonstrate that 86% of respondents claimed to have made efforts related to the improvement of the basic soil structure, yet very few people understood how to stockpile soil correctly. This can be seen in Figure 1. It shows that nearly four out of five respondents were directly involved in land hoarding, and only 2% of respondents built channels to drain water in the marshland, and 5% of respondents created channels to drain water, then fill it with soil.

Fig. 1. Percentage of Community Adaptation of Sub grade soil structure 2. Foundations Construction

Foundation is the most important component in the construction of buildings because it is the structure of the lower part of the building that is directly related to the functioning of l building loads directly to the ground. Based on Figure 2, it can be learned that, in the case of community adaptation to the work of the foundation, 1% of respondents would be more likely to increase the size of the foundation, more than a third of respondents raise or increase the depth of the foundation, 13% spread a layer of sand, and more than half of the respondents made cerucuk under the foundation. Based on this statement, it can be concluded that the society had to adapt with the home building construction, especially the building foundation

Fig. 2. Percentage of Community Adaptation Against Foundation Work

14%

79%

2% 5%

Community Adaptation of Sub grade soil structure

Do not do anythingDo live land fillMake a drainage to dryMake a drainage to dry after that landfill

1% 31%

13% 55%

Community Adaptation Against Foundation Work

Enlarge size foundationElevating FoundationSand layer spreadCerucuk made under the foundation




167

Based on in-depth interviews with respondents, cerucuk used under the foundation is that of mangrove wood which mount every 1 meter along the building foundation with a diameter of approximately 10 cm and a depth of 1 meter. Cerucuk is used to increase the carrying capacity of the marshland and reduce land subsidence. In addition, the cerucuk use is based on indigenous communities, and it is found only in house construction in wetlands while it is not used in dry areas. This means that people already know how to minimize the potential damage of buildings due to an earthquake, especially for building foundation.

3. Roof Construction Almost all the community uses multiroof type of roof (see Figure 3). This suggests that the public option in using this type of roof is considered appropriate due to the preference of people who live in earthquake-prone region got a type of material that is lightweight and safe.

Fig. 3. Comparison of Roof Type Percentage

4.2 Behavior Adaptation

According to Wikantiyoso (2009), understanding the behavior of the earthquake (seismic lines, the epicenter, as well as the tendency of shifting the earth's crust), planning and design of cities and buildings, people anticipate earthquake conditions, quality of the construction, community preparedness, as well as the time of the earthquake. All these must be understood in the interest to minimize the impact of damage to buildings and cities due to the earthquake.

According to Malik (2012) in his study in Pangalengan District, the social unrest that made people in Pengalengan District suffered from heavy damage from the earthquake was due to the following reasons: 1. Total ignorance of disaster. 2. Ignorance of the public about the physical condition of the residential location. 3. Dense and clustered settlement pattern due to limited land.

So far, it can be learned that there is very little communnity’s preparedness in the face of disaster.

The extensive interviews during this research include the efforts to engage in dialogue about the various aspects of life, especially on matters relating to the concepts of people’s adaptation which is shown in how public build houses corresponding the seismicity associated with conditions that often occur in the city of Bengkulu. There are some interesting things concerning people’s behavior in order to adapt with the earthquake: 1. Binding cabinets that are connected directly to the wall

2% 8%

90%

Comparison of Roof Type

Sago palmRoof tileZincMultiroof




168

Binding cabinets that are connected directly to the wall in order that in the event of an earthquake, the closet did not fall and harm the occupants of the house.

2. Protecting and securing the house from thieves As a form of house protection against thieves, people install a trellis on the windows and doors added with a plated door lock. Therefore, during an earthquake, people sometimes find difficulty to run out of the house as soon as possible.

3. Parking cars facing highway At night, a car is parked in the garage of the house facing the street in order to facilitate access out of the house and then go to the evacuation route in the event of an earthquake. In addition, the car fuel is filled in full.

4. Timing of earthquakes Time of the earthquake could significantly affect the death toll. For example, earthquakes during the day will be more likely to cause casualties than at night. This is because at daytime people are at work and in community centers, so as they panic to save themselves, it potentially leads to more loss of life.

5. Degradation of adaptation process This is due to the assumption that human nature can cope with the knowledge that he has. Conditioned environment which is deliberately designed in accordance with human’s lifestyle is often unable to adapt with the place of residence.

6. Disaster Management Disaster management is necessary due to lack of knowledge that results in disaster unpreparedness of society in anticipation of damage to homes and even loss of life following an earthquake. Knowledge of disaster can be improved through socialization, training, seminars, raising public awareness of disaster-prone areas and others. Socialization and training on strategies in the face of disaster risk has actually been done by the local government and relevant agencies, but there are some things that make the socialization less effective, namely: a. Socialization is not done intensively, so people assume knowledge on disaster risk is not

important. b. Poor coordination between parties. c. Sosialization does not touch the society which requires knowledge of the disaster, such as

people who live in the wetlands. Instead socialization are applied only to government employees (administrative elite).

d. Socialization and pre-disaster-based training have been rarely done prior to disaster. Instead, socialization is often conducted after the disaster. It is not appropriate to anticipate the risk of disaster.

4.3 Non Engineering Structure Assessment on Disaster Swampland

Based on the results drawn from the questionnaires and interviews that have been conducted with the respondent, the writers of this research design the format of assessment towards building a simple home in swampland based on Disaster Risk Reduction. The assessment was made in a written sheet. Community is expected to make its own assessment of the Non Engineering Structure. The assessment was conducted on the use of building materials, foundation, walls, roof structure, and dimensions of concrete structures. The results of this assessment show categories: green, yellow and red colors..




169




170

The results of the assesment evaluation of simple house built on wetlands as it was construccted by the homeowners, manifested in the form of "Assessment Form" as follows: 1. Green (Figure 5.)

The green color indicates that the house complies with the rules on building simple construction of earthquake resistant houses on wetlands

2. Yellow (Figure 6.) The yellow color indicates that the house is less compatible with the rules for building simple construction of earthquake resistant houses in wetland. there are several components that do not fit

3. Red (Figure 7.) The red color indicates that the house does not comply with rules of building simple construction of earthquake-resistant houses in wetlands. There are many components evidenced by the house that does not fit. However, it does not mean that the house in green and yellow categories are home safe and will

not be damaged during the earthquake. Homeowners must remain vigilant and be sure to leave the house when the earthquake happen.

5. Conclusions and Suggestions

5.1 Conclusions

Of a series of research activities and data analysis, the researchers conclude that: 1. People have started doing adaptations to their homes building located on wetlands, such as

adaptation to the basic soil structure, adaptation to the foundation work, and adaptations to the roof.




171

2. In addition to adaptation, the society also have to equip themselves with doing strategies in the face of disaster risks, among others: using the funnel below the building foundation, choosing the proper materials used for the manufacture of brick foundation, and a closet that is directly connected to the wall.

3. There are some less appropriate things that people often do which result in inability to minimize the earthquake risk, among others are lifestyle that is less balanced with knowledge of disaster, the use of railings at the windows, and panic during an earthquake.

4. Assessment sheet as a guide to building a Disaster Risk Reduction (DRR) based house construction demonstrates the corresponding category (green color), less compatible (yellow), or does not fit (red color).

5.2 Suggestions

Suggestions as for advice to be conveyed by the author are as follows: 1. Ther is a need for a more detailed adaptation to the building structure, which is balanced with

sufficient knowledge of disaster. 2. It is expected that the presence of advanced research can provide sufficient information to the

community in adapting DRR based on the existing conditions in the city of Bengkulu as a region prone to earthquake.

References

1. Badan Pusat Statistik Provinsi Bengkulu, Provinsi Bengkulu Dalam Angka, Bengkulu; 2010. 2. Hardoyo, S. R. Strategis Adaptasi Masyarakat Dalam Menghadapi Bencana Banjir Pasang Air Laut di Kota

Pekalongan, program Magister Perencanaan dan Pengelolaan Daerah Aliran Sungai dan Pesisir (MPPDAS), RedCarpet Studio, Indonesia, Yogyakarta; 2011.

3. Ishikawa, M., Landscape Planning for a Safe City, Annals Geophysics Journal; 2002, 25(6), 833-841. 4. Konvensi Ramsar, The Convention on Wetlands of International Importance, especially as Waterfowl Habitat, Ramsar,

Iran; 1991. 5. Malik, Y., Penentuan Tipologi Kawasan Rawan Gempa Bumi Untuk Mitigasi Bencana di Kecamatan Pangalengan

Kabupaten Bandung, Fakultas Pendidikan Ilmu Pengetahuan Sosial, Universitas Pendidikan Indonesia, Jawa Barat, Bandung; 2012.

6. Puspantoro, B., Konstruksi Bangunan Gedung Tidak Bertingkat, Universitas Atma Jaya, Indonesia, Yogyakarta; 1996. 7. Republik Indonesia, Undang-Undang No. 21 Tahun 2008 tentang Penyelenggaraan Penanggulangan Bencana,

Sekretariat Negara, Jakarta; 2008. 8. Siregar, S., Statistik Deskriptif Untuk Penelitian, Rajagrafindo Persada, Indonesia, Jakarta; 2010. 9. Supribadi. Ilmu Bangunan Gedung, Armico, Indonesia, Bandung; 2002. 10. Susetyo, H., ‘Disaster Preparedness and Natural Disaster Victim Services: Lesson learned from Japan and Indonesia’,

Kyoto University, Center for Southeast Asian Studies 2 November; 2006. 11. Wikantiyoso, R. (ed)., Kearifan Lokal dalam Perencanaan dan Perancangan Kota; Untuk Mewujudkan Arsitektur Kota

Yang Berkelanjutan, Fakultas Teknik Universitas Merdeka Malang, Indonesia, Malang; 2009. 12. Zen, H. ‘Internasional Seminar/Workshop on Tsunami’, Makalah Gempa Bumi Gubernur Bengkulu, Jakarta; 2003 Hal

241-248.

Documents

Bengkulu City Community Adaptation of non-engineering structure development in swampland based on earthquake disaster risk reduction