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Water Practice & Technology Vol 12 No 3 doi: 10.2166/wpt.2017.067

Emergency scenarios in the Banger polder, Semarang City: a case study to identify different emergency scenarios S. Imam Wahyudia,*, Rick Heikoopb, Henny Pratiwi Adia, Tom Overgaauwb, Bram Schipperb and Roel Persoonb a

Sultan Agung Islamic University, Jl. Raya Kaligawe KM 4, Semarang 50112, Indonesia

b

Rotterdam University Applied Sciences, G.J. de Jonghweg 4-6, Rotterdam 3015 GG, The Netherlands

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

Abstract In Semarang urban coastal areas experience daily flooding from the sea during high tide (tidal flooding). Flourishing residential areas have changed into unhealthy slums with the nuisance of daily flooding in parts of the city. To overcome these problems a polder system was implemented to address the tidal flooding. The Semarang polder system is the first fully operational polder system in a densely populated urban area in Indonesia. This article describes the polder system that prevents flooding in the Eastern part of the city; the Banger polder area. An important element of the polder system is an emergency response plan that prepares for a flood emergency condition. The emergency response plan provides different emergency scenarios and identifies emergency levels and criteria. The management of emergency situations can be divided into four phases, namely mitigation, preparedness, response and recovery. The research results provide a detailed description of four emergency scenarios with 3 emergency levels for each scenario in the Banger polder area. The scenarios are; pumping stations operational damage, high-intensity rainfall in combination with high tide, failure of levees and dams, and an inflow of water from the west and east side of Polder system area. Key words: drainage, emergency response, flooding, floods, polder, scenario

INTRODUCTION Land subsidence forms a serious threat for millions of people in the Northern Part of Java Island in Indonesia. As a result of land subsidence, several cities in Java like Semarang, Jakarta and Pekalongan are partially flooded during high tide. A polder system can be a solution to manage the water levels and protect residential areas. A fully operational polder system in a densely populated urban area is a new phenomenon in Semarang. The Banger Polder is a small polder system which covers an area of around 670 hectares. There are about 90,000 inhabitant living in this area. The Polder area is prone to flooding caused by high water levels during high tide and during heavy rain. This area is also facing land subsidence, with a typical rate of land subsidence in the range of 5 to 10 cm per year (Wahyudi et al. 2012a). Climate change which may result in sea level rise forms a serious daily threat for the coastal areas of Semarang that are located at sea level. A river embankment protects the Banger polder area from flooding caused by the influx of seawater during high tide in the Java Sea. The sea water then flows into the Banger River and the East Flood Canal. The flood protection consists of a levee along the East Flood Canal and the North levee for protection against high water levels in the Java Sea. Recently a dam in the Banger river was

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constructed which closed the open connection between the Banger polder and the Banger river. A pumping station pumps the excess water from the low-lying polder area to the Banjir Kanal Timur (East Flood Canal) which flows into the sea (Mondel 2009). Events that may provoke failure of the polder drainage system in a worst case scenario are heavy rain in combination with high tide. In that situation the pumping capacity could be insufficient which would result in flooding of the Banger area. Anticipation on a technical failure in a future event is prevented by good management of inspection and maintenance system (Guihéneuf 2009). A water level control plan describes the (water level) management and the maintenance of the polder system as a whole to prevent emergency and disaster conditions. The purpose of the emergency response plan is to establish different emergency scenarios, levels and actions to enable the polder management to respond properly to the emergency conditions. A case study in Semarang was done to identify different scenarios for the Banger Polder system. The case study describes various worst case scenarios and specific conditions of the polder system. For each scenario important steps are identified and guidelines are formulated that the polder management can use during an emergency situation. This enables faster and more effective response by the polder management, when an emergency condition occurs (Capodagio et al. 2016). An emergency response plan provides guidance for the response of the polder management and allocation of resources for managing the polder system during emergency situations. In general, emergency management can be divided into four phases to reduce the impact of emergencies condition: preparedness, emergency response, recovery, mitigation (Nema 2016). This study focuses primarily on the response stage and the actions of the preparedness stage. The four stages are illustrated in Figure 1.

Figure 1 | The four phases of disaster mitigation management of polder system (Goh et al. 2015).

METHODS To be able to prepare an emergency response plan for the Banger polder area for future calamities, different emergency situations need to be identified. Different water management experts from Water Board Hoogheemraadschap Schieland and Krimpernerwaard (HHSK) in Rotterdam, The Netherlands, were interviewed as well as various stakeholders and a literature review was undertaken. This study took place within a larger collaboration between Dutch and Indonesian public, semi-public and academic partners. This approach was named RDM approach, see Figure 2 RDM Approach. The RDM approach requires establishment of a Community of Practice. A Community of Practice requires a domain, a shared interest, a community, the members of the domain, and practitioners, which develop a shared repertoire of resources which can include helpful tools, stories and

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Figure 2 | RDM Approach (Boogaard et al. 2017).

experiences, ways to handling a typical problem (Wenger 2001). In this research the domain is water safety in Semarang, the community is represented by the Indonesian and Dutch stakeholders (the public, semi-public and private sector, residents and academic institutions). The practitioners were represented by Dutch and Indonesian researchers. The RDM approach goes a step further and requires; (1) a real life challenge or wicked problem, in this case represented by the Banger area flood problem and (2) an educational approach such as international comparative cases, (3) involvement of international experts and (4) a living lab approach (Boogaard et al. 2017). A Triple Helix connects companies and governments to higher education institutions through students, lecturers and researchers who apply their specialised expertise in a specific sector to real-life challenges (Nuffic 2017). In this study Dutch and Indonesian student researchers and professors worked together in a living lab approach. The research was further supported by (HHSK) in Rotterdam and SIMA Water Board in Semarang. The functioning and organisation of the Dutch polder system was compared with the Banger polder system. The study revealed several scenarios of emergency conditions that need to be anticipated. The most important emergency scenarios that were identified are operational failure of the pumping station, high intensity of rainfall in combination with high tide, levee or dam failure and water flow from the western part of Banger Polder into the Eastern part of the polder area. The study proceeded with the evaluation and identification of the organizational levels and criteria of the different emergency conditions (Ten Vedhuis & Clemens 2009). The emergency conditions can be related to three organizational levels. To determine the procedures of the required organizational levels, three important questions must be answered: What kind of emergency is happening? What is the disaster emergency level? And, where does the disaster occur? Based on the answers to these questions, SIMA, the Semarang Water Board, the organization managing the Banger polder system can decide on the emergency stages and disaster scale: Stage 1- Incident: where the condition are caused by a combination of factors. If the incidents are not handled in a proper way, the situation can rise to stage 2 (emergency) or 3 (disaster) according to (Goh et al. 2015). However, at stage 1, the conditions will not have a big impact on the functioning of the polder system. Incident level one is a local and small incident that causes little disorder, which is relatively easy to solve.

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Stage 2 - Emergency: this is a sudden and unexpected event requiring immediate action as this may bring negative consequences to the health and safety as well as to the environment or property. Local and large disruption of the polder system in a wider scale may occur. Action must be taken immediately to minimize the damage and to prevent a worsening situation. Stage 3 - Disaster: where events provoke serious disruption of daily life. It has a large impact to the environment or property. In most cases, people need to be evacuated from the location. Emergency response should be undertaken immediately to limit the damage and to restore the emergency level to level 2 or level 1.

RESULTS AND DISCUSSION A risk assessment for the Banger polder area was undertaken and identified four emergency scenario’s (Wahyudi et al. 2015). The 1st scenario is the incident of an operational failure of the pumping station. The 2nd scenario is the incident of heavy rainfall in combination with high tide. The 3rd scenario is the incident of failure of the levee or dam. And the 4th scenario is the incident of water flow from the west side of Banger Polder into the eastern part of the Banger polder. The following paragraphs describe the organizational levels of the SIMA Water Board, the assessment criteria for each emergency situation and anticipation of four scenarios. Scenario 1: operational failure of the pumping station

The pumping station (see Figure 3) is one of the major components of the polder system to control the water level in the polder area. In the event of operational failure of the pumping station, the water is unable to exit the Banger Polder area, provoking an increase in the water level in the polder system, which eventually causes flooding (Wahyudi et al. 2012b). The operational failure of the pumping station can be the result of several causes, including but not limited to: fire, broken or jammed pumps, dysfunction of power generators, damaged or clogged pipe inlet/outlet due to trash. The emergency conditions for each level of pump damage and the specific criteria for each level are described in Table 1.

Figure 3 | Pumping station operating in Banger polder (Wahyudi et al. 2016).

Scenario 2: high rainfall intensity in combination high tide

Indonesia is located in a tropical climate. Especially in the months of October to March heavy rainfall (high rainfall intensity) frequently happens. The polder was designed for a rainfall situation with a return period 10 year (T ¼ 10). The polder was tested by a simulation for a rainfall intensity that occurs once in 10 years (Wahyudi et al. 2011).


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Table 1 | The 3 levels and criteria of operational failure of the pumping station Level of operational failure of the pumping station

1

2

3

Criteria

• • • • • • • • •

1 or 2 pumps are not operational, pump capacity decreases between 2 to 4 m3 /s No flooding yet, water level is stable or there is a low increase of the water level in combination of high rainfall intensity and high tide 3 or 4 pumps are not operational, pump capacity decreases between 6 to 8 m3 /s Water level increases to a danger situation, especially when there is a combination of high rainfall intensity and high tide. Mobile pump is prepared All pumps are not operational. Pump capacity is 0 m3/s The Mobile pump must function Weirs and levees can be damaged Residents need to be evacuated, especially when there is a situation of high water level in the East Canal and the Java sea an high rain intensity

The water in the Banger area will be pumped and discharged into the East Flood Canal. The pumping station can start pumping before an expected heavy rain period as a preventive measure and to lower the water level in the Banger polder. With a lower water level in the Banger polder area, the Banger polder area will be able to store more water. When a heavy rain situation occurs at the same time with high tide or flood at the East Flood Canal, maintaining the strength of the embankments and an acceptable water level in the Banger area and East Flood Canal will become difficult. This situation was already taken into considering during the design of the river embankments to avoid critical water levels and/or a collapse of the embankments. The emergency scenario when heavy rain and high tides occur simultaneously, has to take several important aspects into consideration, namely high sea water levels during a high tide situation (or even spring tide), the rainfall intensity, water level in the polder system as well as the maximum allowable water level in the polder system. Levels and criteria for emergencies caused by heavy rains and high tide are shown in Table 2. Scenario 3: levee or dam failure

The Banger polder area is separated from the sea and river by levees and a dam (see Figure 4). The levees can be categorized into primary and secondary levees (Khalifa et al. 2002). The primary Table 2 | The 3 levels and emergency criteria of heavy rainfall simultaneously with high tide conditions Emergency level of heavy rainfall simultaneously with high tide conditions

1

2

3

Criteria

• • • • • • • • • • • • •

Heavy rainfall over a longer period of time Tide is quite high Water level in the polder system is higher than the maximal acceptable water level Small local inundation is happening Heavy rainfall over a longer period of time Water level in the polder is higher than the danger water level High tide sea level Local and large flooding is happening Heavy rainfall happening over a longer period of time High water level in East River High tide sea level Many areas are flooded and wider flooding areas Buildings and infrastructure in Banger polder area are damaged


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Table 3 | Levels and emergency criteria of levee and dam Level of levee and dam emergency conditions

Criteria

1

•

2

• • •

3

• • • • • • •

The protection level of the levee decreases because there was a sliding of the upper part or subsidence of the levee Based on the technical inspection, strengthening of the levee and/or dam is required No flooding occurs and water level elevation is still relatively safe The protection level of the levee decreases because levee or dam damage as a result of sliding and subsidence Normal water level Heavy rain and high tide. Threat to the levee is overflowing. Damage of levee and dam in some location sand not fatal. Water level decreases but not yet dangerous Levee and dam failure are caused by sliding and collapse Water level rises, it endangers the inhabitants in the polder area Buildings, levees and infrastructure are damaged

Figure 4 | Levee and temporary dam (Wahyudi et al. 2016).

levees protect the Banger polder area against the water from the sea and the rivers, while the secondary levees protect the water from an overflow of the smaller channel within the polder system. Emergency situations can occur when a levee or embankment becomes instable, moves or slides. An emergency condition usually starts from cracks in the embankments which develop into a damaged embankment. Non-technical conditions can also result in a damaged levee or embankment, such as sabotage or an explosion of the pipeline. Conditions will be more dangerous if this occurs simultaneously in a heavy rain and high tide situation. Criteria for determining the emergency level of levee and dam failure use the level of damage to levees and weirs, the damage location, the number of damages, weather conditions and sea and river water levels. The levels and emergency criteria are given in Table 3. Scenario 4: water flow into the polder system from the west side of Banger polder area

The Banger polder system is protected from an inflow of water from the outside by levees and a dam. On the north side the polder system is protected by the Port Arterial Road. In the eastern part it is protected by the levee of the East Flood Canals. On the west side there is no levee, but the polder system is bordered by a road (Jl. Ronggowarsito and Jl. Haryono), the road separator. Since the Northern part of Semarang is prone to land subsidence, and roads do subside in this area, there is a flooding risk due to a water flow from the western part of Banger polder into the polder system (Wahyudi et al. 2017). Figure 4


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illustrates the border of Banger polder area and the road that separates the western side of the city from the polder area. The red arrows show the water flow into the polder system (Figure 5). Several factors are considered to determine the levels and criteria for emergency conditions caused by the water flow into the polder area from the west side of Jl. Ronggowarsito and Jl. Haryono roads. These factors are; the water elevation in the west side area of the polder, the weather conditions; the flooded areas, the flooding depth at the polder of the western area as well as the actual condition of the water level in Banger polder system. Table 4 indicates the levels and emergency criteria of an influx of water from area west of the polder system.

Table 4 | Levels and emergency criteria of an influx of water from the area west of the polder system Level of emergency from inflow of water from the western part of the polder area

1 2

3

Criteria

• • • • • •

Heavy rain over a longer period of time Local and small inundation in the western area of the polder Inundation in the western area of the polder .30 cm Road separator inundated Water level in the Banger polder is higher than normal Water flow is continuously passing through the road separator

CONCLUSIONS Emergency scenarios for the Banger polder area were successfully identified and levels and actions to enable the polder management to respond properly to the emergency conditions were established for the Banger polder system. This study is very important as prior to the establishment of the polder, 90,000 people used to suffer from daily flood in their houses. But still, due to soil subsidence and sea level rise and failure of the polder system calamities can occur, which are a threat to the operation of the polder system and the people that live in the polder area. Identification of risks and emergency scenarios is a prerequisite for the proper functioning of this polder system, now and in the future. Since the Banger polder is the first polder system in a densely populated urban area in Indonesia, it is of utmost importance that this showcase polder will not fail and that the different risks, the emergency scenarios and emergency levels for each scenario are identified, classified and communicated with the polder management and the public. Other delta cities, that are experiencing frequent flooding or that lie just above or below the sea level or which are threatened by land subsidence and rising sea levels, might as well in the near future shift to polder systems, in which water levels can be artificially controlled with pumping stations. Risk assessment is the foundation of the prevention of calamities. 1. The 4 emergency scenarios for the Banger polder area that were identified are: (1) operational failure of the pumping station, (2) high rainfall intensity in combination high tide, (3) levee or dam failure, and (4) water flow into the polder system from the west side of Banger polder area. 2. For each emergency scenario three different levels of emergency were identified. The emergency levels that were identified are: incidents, emergencies and disaster. 3. For each level of emergency, specific indicators and criteria were formulated, which resulted in 12 different emergency level descriptions of the four emergency scenario’s. 4. Four scenarios have been formulated for the Banger polder. For each scenario 3 emergency levels have been identified. The next step in the process to create a functional polder system would be the identification of specific response actions that the polder management could take during each emergency level. The emergency levels have now been identified but we do not yet know what

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Figure 5 | Water flow into the polder system from the west side (Wahyudi et al. 2015).

emergency responses have to be formulated, an emergency response system. This requires further research. 5. For the proper functioning of the polder system during an emergency situation, we also need to know what emergency preparedness and response items we need to store, such as mobile barriers, emergency pumps, sand bags, shovels, reserve parts and others, and at what location in the polder we need to store these emergency preparedness and response items, so that these items are nearby and easy to access in case of calamity. 6. The RDM approach has proven to be a very successful methodology to address real life problems, conduct applied research and formulate applied solutions based on actual problems in Semarang and specifically the Banger polder area. A Community of Practice requires a domain, a shared interest, a community, the members of the domain, and practitioners. All were present in the Banger polder study. In addition to the Community of Practice a Living Lab approach in which Dutch and Indonesian students and professors worked together in mixed teams proved to be a very efficient way to share experiences and formulate practical solutions. The involvement of Water boards HHSK in Rotterdam, Netherlands and Banger SIMA in Semarang, RISTEK, the

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Higher Education Ministry of Indonesia and NESO, The Netherlands Educational Support Office in Jakarta represented the public sector involvement in the Living Lab. All of them were to some degree involved in the research which contributed in the sustainability of the cooperation.

REFERENCES Boogaard, F., Heikoop, R., Boer, E. & Palsma, M. 2017 Effective international knowledge exchange to rehabilitate rivers in Urban Delta’s with RDM approach. In: Matec Web of Conferences, 13p. Capodagio, A. G., Ghilardi, P. & Boguniewicz-Zabocka, J. 2016 New paradigms in urban water management for conservation and sustainability. Water Practice and Technology 11(1), 176–186. doi:10.2166/wpt.2016.022. Goh, S., Heng, G. & Goh, M. H. 2015 Business continuity management planning methodology. International Journal of Disaster Recovery and Business Continuity 6, 9–16. https://scholar.google.com/citations?view_op=view_citation&hl=en&us. Guihéneuf, B. 2009 A landscape charter: French Regional Nature Parks – pioneers of sustainable development in France. In: Irish National Landscape Conference. Khalifa, M. A. O. A., Wahyudi, I. & Thomas, P. 2002 New extension of Darcy’s Law to unsteady flows. Soils and Foundations 42 (6), 53–63. doi:10.3208/sandf.42.6_53. Mondel, H. 2009 Banger Polder Semarang Conceptual Design Report. Wittee Boss The Netherlands. Nema 2016 Emergency Management: A Vital Government Function. An Elected Official’s Guide to Emergency Management, 1–6. Nuffic, N. 2017 Living Labs. on Water Opgehaald van Nuffic, The Dutch Organisation for Internationalisation in Education. https://www.nuffic.nl/english/internationalisation/market-information. Ten Vedhuis, J. A. E. & Clemens, F. H. L. R. 2009 Uncertainty in risk analysis of urban pluvial flooding: a case study. Water Practice and Technology 4(1), doi:10.2166/wpt.2009.018. Wahyudi, S. I., Lebras, G. & Adi, H. P. 2011 Issues, methods and institution management to overcome tidal flood in La Briere France, Rotterdam The Netherlands and pilot project in Semarang Indonesia. In: The 25th ICID European Regional Conference. Groningen, The Netherlands. Wahyudi, S. I., Adi, H. P. & Lebras, G. 2012a The evaluation of land and sea level in attempts to control drainage system of tidal flood area in Semarang Indonesia. In International Commision Irrigation and Drainage (ICID) Conference 63rd International EC Meeting. Adelaide, Australia. Wahyudi, S. I., Ni’am, M. F. & Le Bras, G. 2012b Problems, causes and handling analysis of tidal flood, erosion and sedimentation in northern coast of central java: review and recommendation. International Journal of Civil & Environmental Engineering 12(4), 65–69. Wahyudi, S. I., Overgaauw, T., Schipper, B., Persoon, R., Heikoop, R. & Adi, H. P. 2015 Kriteria Kondisi Darurat Banjir dalam Sistem Polder: Studi Kasus Banger Polder Area Semarang. Riptek 9(1), 1–8. Wahyudi, S. I., Adi, H. P. & Niam, M. F. 2016 Simulating and Arranging of Operation, Inspection, Maintenance and Emergency Respond Model in Polder Drainage System to Handle Tidal Flood Caused by Climate Change. Research Report, Unissula, Semarang. Wahyudi, S. I., Adi, H. P., Santoso, E. & Heikoop, R. 2017 Simulating on water storage and pump capacity of ‘Kencing’ river polder system in Kudus Regency, Central Java, Indonesia. In AIP Conference Proceedings, doi:10.1063/1.4976928. Wenger, E. 2001 ‘Communities of Practice.’ International Encyclopedia of the Social Behavorial Sciences.