Philippine Science High School Main Campus Decision and Impact Analysis of a Proposed Stormwater Management and Road Tunnel in Metro Manila Patricia Carmela V. Caronan Ma. Angeline W. Jumangit Arvin John S. Malapo May 2020 Decision and Impact Analysis of a Proposed Stormwater Management and Road Tunnel in Metro Manila by Patricia Carmela V. Caronan Ma. Angeline W. Jumangit Arvin John S. Malapo Submitted to the Faculty of the Philippine Science High School - Main Campus In partial fulfillment of the requirement for Research 3 May 2020 ABSTRACT Typhoons are the most common disasters that the Philippines experiences, resulting in numerous instances of urban flooding. Heavy traffic also remains to be one of the main problems here, specifically in the Metro Manila area. These problems are continuously being attempted to be solved through various policies and revised systems being implemented in the country, though the search for optimal solutions still persists. The study was conducted to assess the feasibility and impact of a Stormwater Management and Road Tunnel System in Metro Manila. The assessment of the proposed floodwater and tunnel system was done by gathering data from various government and research institutions in order to assess the optimal location for the proposed infrastructure. The data gathered was analyzed through different tests to determine the significant values and figures that will be used in the simulation. The simulation of the proposed system was then done using Vensim in order to assess and determine the most effective mechanism for the system. The ideal route of the floodway was identified to start from the Marikina River in the area near SM Marikina and end at Manila Bay while the road tunnel was determined to start from the R6-C4 intersection and end at the R8-C2 intersection. The simulated model showed that the system is effective in mitigating the flood levels in the Marikina River at different precipitation rates. Simulation of the infrastructure systems through a physical model incorporated flood and traffic data is recommended for further testing. Keywords: tunnel, traffic, flood mitigation, Metro Manila, Marikina River APPROVAL SHEET This research work entitled, “Decision and Impact Analysis of a Proposed Stormwater Management and Road Tunnel in Metro Manila” by Patricia Carmela V. Caronan, Ma. Angeline W. Jumangit, and Arvin John S. Malapo, presented to the Faculty of the Philippine Science High School - Main Campus in partial fulfillment of the requirements in Research 3, is hereby accepted. _____________________________ _____________________________ Jejomar O. Bongat Mc Jervis S. Villaruel Research Teacher Research Teacher i ACKNOWLEDGMENTS The researchers would like to thank Mr. Jejomar Bongat and Mr. McJervis Villaruel for their constant support and help in providing valuable insights that led to the completion of the project. The researchers would also like to express their gratitude to Ms. Jordanne Zamora, a student from the Department of Psychology at the University of the Philippines - Diliman, for helping in the procurement of important references for this study. ii TABLE OF CONTENTS Page Approval Sheet…………………………………………………………………………………….i Acknowledgments………………………………………………………………………………...ii Table of Contents…………………………………………………………………………………iii List of Figures…………………………………………………………………………………….iv Introduction………………………………………………………………………………………..1 Background of the Study………………………………………………………………….1 Objectives of the Study……………………………………………………………………3 Significance of the Study………………………………………………………………….3 Scope and Limitations……………………………………………………………………..3 Literature Review………………………………………………………………………………….4 Philippine Geography……………………………………………………………………..4 Floods……………………………………………………………………………………...4 Factors affecting floods……………………………………………………………5 Flooding in the Philippines………………………………………………………..6 Traffic……………………………………………………………………………………..7 Factors affecting traffic……………………………………………………………8 Effects of traffic………………………………………………………………….10 Traffic in the Philippines………………………………………………………...11 Hazard Mitigation………………………………………………………………………..13 Flood Mitigation Systems………………………………………………………..14 Traffic Congestion Solutions…………………………………………………….15 SMART Tunnel………………………………………………………………………….16 Construction of SMART Tunnel………………………………………………...18 Mechanism of the system……………………………………………………..….20 Effects of tunnel utilization……………………………………………………....21 Methodology……………………………………………………………………………………..22 Process Flowchart…………………………………………………………………….….22 Collection of Flood and Traffic Data Sets……………………………………………….22 iii Simulation of Proposed Tunnel System………………………………………………….22 Data Analysis…………………………………………………………………………….23 Results and Discussion……………………………………………………….………………….24 Analysis of Flood and Traffic Data Sets…………………………………...…………….24 Simulation of Proposed Tunnel System………………………………………………….26 Summary and Conclusion……………………………………………………………….……….28 Recommendations…………………………………………………………………………….….29 Bibliography……………………………………………………………………………………..30 iv List of Figures Figure Title Page 1 Metro Manila radial and circumferential road layout (“Metro Manila Road Network”, 2015) 13 2 and 3 Junction of the Klang and Gombak River at the center of the city (River of Life (Phase 1), 2018; Lai, 2016) 17 4 SMART Tunnel structure (Dethan, Kavitha, & Nair, 2018) 18 5 Tunnel Boring Machine operation at the SMART Tunnel site (Kannapiran, 2005) 19 6 Double deck interior of the SMART Tunnel (Isah & Ali, 2015c) 20 7 SMART Tunnel modes of operation (Santhiman & Weei, 2006) 21 v INTRODUCTION Background of the Study The rapid occurrence and increasing expansion of natural disasters remains to be a major threat to the welfare and safety of individuals in present day society (Bronfman, Cisternas, Repetto, & Castañeda, 2019). Through the numerous efforts to analyze the nature of these calamities, it was found that Asia is the most-disaster prone region in the world due to it having the highest incidence rates of flooding, earthquakes, and typhoons (Chan, Man, Lam, 2019). Numerous factors, such as geography, climate, and the abundance of industrial advancements, have been found to affect the prevalence of these conditions (Garcia & Hernandez, 2017). The Philippines is no stranger to these occurrences and has been coined as one of the most disaster-prone areas in the world with typhoons as one of the most frequently occurring catastrophes (World Bank, 2005). Typhoons are natural disasters that adversely impact the people and environment of the affected region. An average rate of 19.4 typhoons are experienced annually by the Philippines from 1951 to 2013 (Cinco et al., 2016). This is a phenomenon that is observable at different magnitudes throughout the various regions of the country (De Viana, 2016), one of which includes Metro Manila. The topographical characteristics of the region allow it to be directly affected by incoming typhoons, as well as resulting floods and landslides (PAGASA, 2015). Other geographical features, which include it being surrounded and traversed by rivers (Bankoff, 2003), contribute to the occurrence of severe flooding that could be witnessed during long and short periods of rainfall (Lagmay et al., 2017). Numerous projects have been established to counter the detrimental effects of these situations, though they still remain inadequate in fully mitigating the incidents (Gilbuena et al., 2013). Additionally, the severity of the flooding conditions in this area is increased by the continuous pollution of the rivers found here (Helmer et al., 1997). 1 The frequent flooding in such urban areas then results in the disruption of transportation systems (Pregnolato, Ford, Wilkinson, & Dawson, 2017). This involves the presence of intensified traffic congestion, which has been identified as one of the major obstacles in the development of a country (Teknomo et al., 2019). The increase of privately-owned vehicles has contributed to the escalation of the congestion (Enslin, 2018). In line with this, innovations in road infrastructure are constantly being developed in order to produce more sustainable and efficient systems to address these problems. Numerous roadway structures have been designed to better suit the existing infrastructure and lifestyle conditions in their area of placement. An example of which is the use of underground tunnels as alternative passageways that minimizes the disruption of established surface area life (Balasubramanian, 2014). Furthermore, multi-purpose structures that aim to simultaneously address particular environmental issues, such as urban flooding, have also been implemented. The Stormwater Management and Road Tunnel (SMART) System is one of such structural innovations designed to address the problems and consequences of flooding and traffic in urban regions. Located in Kuala Lumpur, Malaysia, the SMART Tunnel is a multipurpose tunnel that is utilized both as a roadway and a flood management system. It was found to be effective in alleviating the frequent floods that occur in the area caused by inadequate drainage systems aggravated by Malaysia’s typhoon-prone geographic location. The Philippines, currently having problems with inefficient traffic and floodwater management systems, is in need of similar innovations in order to improve the overall state of the country in the event of such natural disasters. 2 Objectives of the Study This study aimed to assess the effectivity of a proposed multipurpose tunnel system for flood and traffic mitigation to be constructed in Metro Manila. To achieve this, the study was able to determine the most optimal location for tunnel placement within the Metro Manila region through data analysis. It was also able to produce a simulation model for the working mechanism of the proposed tunnel system through the use of the Vensim simulation software. Significance of the Study Findings from this study will serve as a framework for future construction projects, policies, and proposals that aim to implement a SMART roadway or other similar initiatives in a Metro Manila setting. Additionally, the study offers an insight to the possibilities of multipurpose structures that address the problems of both flooding and traffic in highly urbanized areas. Scope and Limitations The study was able to identify the most ideal location for the tunnel system within Metro Manila, as well as determine its mechanism through the analysis of existing data points. Because of this, the study is limited only to the theoretical aspect of the tunnel simulation. Furthermore, other factors, such as the cost of building such a tunnel and consequent environmental impacts to the area of construction, were not considered due to the lack of reliable sources for calculations and due to time constraints. 3 LITERATURE REVIEW Philippine Geography The Philippine archipelago is composed of over 7,100 islands, encompassing 2,200,000 square kilometers of water area and approximately 300,000 square kilometers of land area. These islands range in size from tiny islets to the large expanse of Luzon. The topography is highly diverse with mountain ranges traversing the major islands from north to south, narrow coastal plains bound islands and a complex network of inland waters that offers rich resources of coral reefs, marine life and mangrove forests (Licuanan, Cabreira, & Aliño, 2019). It is also surrounded by an array of seas and straits that stretch from Southeast Asia to Australia. The Celebes Sea to the south, the Sulu Sea to the southwest, the Philippine Sea and Pacific Ocean to the east and the West Philippine Sea to the west and north. Located near the equator, the Philippines is found in the torrid zone and experiences tropical climate. This climate is affected by the monsoons, or the major wind systems that affect the temperature trend over land and oceans. They respond to the adjacent seas, more specifically, the Pacific Ocean as weather systems travel from east to west (Case, 1927). The warm temperature near the equator affects the wind such that moisture and pressure increase which causes winds to move quickly, later forming a typhoon. The Philippines is prone to tropical cyclones as a result of its geographical location and experiences approximately 20 tropical cyclones every year. Floods Floods are one of the most frequent and destructive types of natural disasters that occur as any area where rain falls is vulnerable to them. Natural floods occur when water falls more quickly than water can be absorbed or exceeds the river channel’s capacity, and consequently spills over the embankments (Alfieri et al., 2018). The earliest civilization settlements were built near coasts 4 and the people enjoyed the excess water to support their basic necessities and livelihoods, this soon became a serious problem when floods began to threaten their health, properties, economic activity and safety (Dobrovicova, Dobrovic, Dobrovic, 2015). In the recent decade, floods have caused more than $104 billion in damage worldwide every year and are reported to cause the most damage compared to other natural disasters (Blöschl et al., 2017) These damages amount from structural, economic and agricultural loss, and also significant impacts on the health and safety of the people. Through the years, floods have become more common as a result of increased frequency of heavy rainfall. Factors affecting floods While most floods take time to develop, multiple factors can accelerate flooding, thus affecting the degree of damage it can cause its affected areas. Natural geographic features such as landforms and bodies of water surrounding an area heavily affects susceptibility to flooding. Coastal flooding, sourced from nearby bodies of water is common in coastal areas wherein water can reach miles from shores, onto rivers and across flat land as the sea level rises (Nicholls et al., 2011). Local factors such as the natural elevation, vegetation present, and subsidence also increase the flood risk in these areas. Similarly, the presence of different landforms influences the risk of flood in an area. Mountains affect wind patterns as the pressure difference as the height increases attracting air to rise, forming depressions and storms. Most mountainous areas tend to have wetter climates than low lying areas (Spreafico, 2006). Additionally, other environmental factors such as the forests and plant life impact the frequency and magnitude of floods. Deforestation and plant cover are commonly associated with reduction in soil infiltration capacity and erosion. While the previously mentioned processes both occur naturally, the removal of plant cover accelerates it and increases 5 sediment runoff that occurs during rainfall (Gholami, 2013). Combined with other factors such as the terrain gradient, soil type and geological factors, some areas naturally considered to be more flood prone than others. Though flooding is considered a natural hazard, human activities have made more areas susceptible to flood. The natural progression and modernization of the society have changed the use of land with the intent of creating a more advanced and efficient way of living. However, rapid growth of the population and inadequate urban planning are the main reasons behind clogged waterways and blocked sewage systems that leave urban cities vulnerable to flooding. With the human population expected to triple by 2050, the densification of buildings and residential areas will continue to affect the natural environment such as the use of urban concrete which affects the rate and volume of infiltration (Hammond et al., 2015). An increase in population without effective urban planning in drainage networks increases runoff to streams causing them to limit their capacity of floodwaters (Lagmay et al., 2017). Most flood-prone areas are found in urban areas where streets and creeks intersect. The continuous removal of vegetation in and around urban areas also increases the runoff volume which increases the pressure of the canals, resulting in a faster rate of water level rising during heavy rainfall (Mei, et al., 2017). Flooding in the Philippines In the Philippines, floods and landslides are closely related to tropical cyclones. As a result of its geographical features, the Philippines is named to be highly prone to natural disasters such as earthquakes, volcanic eruptions but most especially, tropical cyclones and floods. The country is most exposed to tropical storms in the world, averaging about 20 typhoons to enter Philippine egion (Mohammed, 2018). The rainfall season, heavily influenced by the “Habagat” or southwest monsoon, is normally pronounced from May until September. This is characterized by frequent heavy rainfall and humid weather. 6 Despite being a recurring weather pattern in the country, records from the last two decades have shown an increase in loss and damage from floods. Among the 20 tropical cyclones that enter Philippine region, four to five are said to be potentially destructive (Mercado, Kawamura, & Amaguchi, 2019). Severe destruction of houses, livelihoods, injuries and deaths of people in the country are some of the worst effects from typhoons and floods. In recent records, the socioeconomic costs of floods and landslides have totaled to $1 billion from Typhoon Bopha in 2012 and $4.3 billion form Typhoon Ketsana (Ondoy) and Parma (Pepeng) in 2009 (Acosta et al., 2016). Natural disasters, not just flooding, impact travel conditions and road networks. As a result of these events, some areas would be less accessible or be greatly inconvenient for transport. This event, combined with the dense population and the failing urban planning and drainage designs of Metro Manila, all contribute to an increased volume in vehicles and road traffic during floods. According to Tomtom’s 2019 Traffic Index, Manila is named as the second most traffic-congested city in the world. An average Filipino in Manila spends an extra 71% on transportation alone and road traffic conditions still worsen when heavy rain builds up to floods (Abad & Fillone, 2017). Traffic Continuous modernization in numerous countries and cities have resulted in the increased occurrence of road traffic. This results to an increase in traffic congestion within these areas, making it one of the most significant problems found here (Rithesh, Vignesh, & Anala. 2018). Traffic congestion is a worldwide societal issue that happens when the road capacity is insufficient in accommodating the requirements of roadway users (Isa, Mohamed, & Yusoff, 2015). The aspect of time and space are heavily considered in determining the state of traffic, resulting in the two types of such phenomenon: regular and occasional traffic congestion (Dong, Ma, Guo, & Liu, 2012). Regular traffic congestion is the result of the continuous inadequacy of road facilities in 7 line with the transportation networks of the area while occasional traffic congestion occurs during the presence of accidents or other unforeseen events such as natural calamities. Factors affecting traffic Traffic congestion is affected by multiple factors, but these are simplified into four categories, namely: environmental, mechanical, human, and infrastructural. The first three categories are collectively known to be non-recurring types, meaning they happen occasionally and are transitory. Infrastructural factors, on the other hand, are considered to be of the recurring type as they occur regularly and happen when vehicles overcrowd due to the physical limitations of existing roadways (Geotab, 2018; Federal Highway Authority, 2020). The state of development in an urbanized region is often influenced by numerous aspects, some of which directly affect the magnitude of traffic congestion apparent in these areas (Koźlak & Wach, 2018). The weight of each of these factors as contributors to the problem vary depending on the period of observation and location of the area. Poor conditions in the fields of transportation, urban planning, and population or individual behavior are some of the major contributors to this. The modes of public transit present in respective cities are some of the most crucial elements in the function of a society (Stjernborg & Mattisson, 2016). Despite the problem of high number of vehicles being addressed, the mere presence of public transportation options remains insufficient unless the consequent demand from travelling individuals for these services are met (Beaudoin & Lawell, 2017). Furthermore, attempts at reduction of traffic congestion through public transportation is highly affected by the proper implementation of such initiatives (Koźlak & Wach, 2018). An example of this is the negative effects of bus transportation to the overall state of traffic congestion due to the placement of bus stops, varying bus operation methods, and road behavior, such as the number of lanes taken up by these vehicles (Nguyen-Phuoc, Young, Currie, 8 & De Gruyter, 2020). Poor public transport conditions due to the lack of convenience and comfort offered to its users result in an increased reliance of individuals on private modes of transportation instead (İmre & Çelebi, 2017). The increase of private vehicles increases the road density on highways significantly, thus worsening the state of traffic (Masood, Khan, & Naqvi, 2011). Furthermore, the urban planning of a land area, specifically its road networks and public transit locations, play a vital role in traffic congestion. An initial foundation of a city layout is crucial since a lack of such results in any infrastructure-related modernization and development to be increasingly difficult (Maji, 2017). According to He & Zhao (2013), travel time on roads is significantly affected by mass of vehicles at intersections, as well as the placement of bus stops. The layout and placement of roads and their utilities, such as speed bumps and stop lights, contribute to the occurrence of bottlenecks on highways and disturbs the flow of traffic (Mahona, Mhilu, Kihedu, & Bwire, 2019). Additionally, the presence of residential areas was found to contribute to the rate of congestion due to the direct correlation between the density of residing citizens and the need for transportation options (Zhang, Sun, Yao, & Rong, 2017). The rapid urbanization of countries and cities around the world would also mean that there is a rapid increase in the human population (Buhaug & Urdal, 2013). As the number of citizens increase, so will the necessity for the utilization of various roadway facilities (Vencataya, Pudaruth, Dirpal, & Narain, 2018). This contributes heavily to the congestion problem since it was found that at peak hours, bumper to bumper traffic is mainly caused by the number of vehicles on the road at the given time period. It was also found that cities with high population rates are at greater risk of an increase in congestion, travel time, and accidents (Goetz, 2019). Other than the number of the population, its behavior also serves as a factor (Arai & Sentinuwo, 2012). A common example of this is the changing of lanes of vehicles while on the highway, which was 9 found to disrupt the smooth flow of traffic due to its consequent impact on surrounding vehicles (Laval & Daganzo, 2006). Another is the occurrence of road blocking due to the improper use of designated parking spaces or the illegal use of non-designated ones (Rumidi, 2014), as well as the disruption caused by the entrance and exit of vehicles into such parking lots. Effects of traffic The vital role of transportation as an element of the proper function of society is apparent through the effects of traffic beyond the transportation sector. Its negative impact could be evident in aspects such as the economy, environment, and individual health, lifestyles, and safety (Falcocchio & Levinson, 2015). Traffic congestion has been observed to be an indicator of economic activity since it could be caused by road use for profession-related tasks of a company or an individual (Harriet, Poku, & Emmanuel, 2013). However, it is also associated with a slower rate of productivity in the output and production of goods (Sweet, 2013). Much time used for work is often invested in the prolonged travel time caused by congestion, limiting the efficiency of execution of assigned activities for job completion (Anciaes, Metcalfe., & Heywood, 2016). Numerous problems in various occupational sectors, such as logistics or transportation, can also be observed due to such phenomenon (Kellner, 2015). According to Levy, Buonocore, & von Stackelberg (2010), a huge economic loss annually results from these conditions alone. Traffic has been constantly recorded as a source of declined quality in the lifestyles of various individuals (Anciaes, Metcalfe, & Heywood, 2016). A study by (Ghazali, 2019) has found that most citizens formulate their daily routines and practices based on the state of traffic in their area of residence. Furthermore, the simple act of being on the road has been found to result in varied behavioral reactions, ranging from aggression to distraction, among drivers (Hennessy & 10 Wiesenthal, 1999). This deterrent effect on the mental state of individuals could then be reflected in physical manifestations like chest pains and nausea. This could lead to road accidents occurring in congested areas, which though are lower in fatality compared to accidents free-flowing vehicle situations, could still occur more frequently due to the higher traffic volume (Wang, Quddus, & Isan, 2009). Other than this, a decline in the health of citizens could occur due to environmental impacts of traffic. Carbon emissions from road vehicles are a major source of air pollution, thus reducing the air quality within the area (Zhang & Batterman, 2013). The extremity of this contamination results in around 60% of atmospheric pollution to come from this congestion, under which around 90% comes from private vehicles (Chin & Rahman, 2011). Furthermore, varying levels of noise pollution is observable due to the different vehicles and road structures found within a city (Marve, Bhorkar, & Bautule, 2016). Overall, episodes of traffic congestion contribute to the depletion of natural resources and deterioration of the ecosystem (Condurat, Nicuţă, & Andrei, 2017). Traffic in the Philippines Among many developing countries, the Philippines experiences rapid urbanization with effects apparent through the increase in economic progression and population density in the city center, Metro Manila (Yujuico, 2015). However, this immense productivity has resulted in problems as the resources of the region, specifically in the transportation sector, are unable to accommodate all of the users residing in the region. This then results in the heavy traffic conditions that are apparent throughout various parts of the city. The Metro Manila transport scene, just like the rest of the country, relies heavily on onroad transit (Muromachi et al., 2015). Despite the presence of rail transit, specifically the Metro Manila Rail Transit System (MRT), that could alleviate some of the vehicle mass found on the 11 roads, most modes of public transportation (Mijares, Suzuki, & Yai, 2016) still occur on highways. Furthermore, regardless of the presence of paratransit, such as jeepneys, tricycles, or FX services that could help alleviate traffic on main highways (Mabazza, 2018), they are still considered as individual operators that add to the road density apparent during travel hours. Poor public transportation methods then result in increased reliance on private vehicles that worsen the traffic conditions of the city (DOTR, GIZ, 2016). Based on a study by Lidasan, Espada, & De Leon (2010), Metro Manila traffic is mainly caused by the poor urban planning and management systems present. As seen in Figure 1, the layout of the city road network is comprised of radial and circumferential roads ten and five in number respectively (Roth, 2001). Within this area, the Epifanio de los Santos Avenue (EDSA), or C4 road, is one of the busiest routes due to the high number of vehicles passing through here (DOTr, GIZ, 2018). Despite the establishment of C5 road to alleviate the motor density on EDSA, the state of traffic is yet to improve for both these areas (Boquet, 2013). 12 Figure 1. Metro Manila radial and circumferential road layout (“Metro Manila Road Network”, 2015) Hazard Mitigation Hazard mitigation is concerned with diminishing the harmful impacts of disasters, as opposed to preventing their occurrence altogether. The concept recommends policies to be proactive, rather than reactive, to the consequences of forthcoming disasters. There is also a tendency for policies to be reparative when it comes to addressing the aftermath of disasters. These solutions, although effective, prove to be costly in the long run due to the repetitive cycle of damage and restoration. Mitigative policies avoid this cycle by reducing the amount of damage that would normally happen which, in turn, will incur less economic consequences and loss of life, ultimately cutting the cost for repairs (Godschalk, 2003; Los Angeles Emergency Management Department, n.d.). Flood Mitigation Systems Communities employ the concept of flood mitigation through various strategies that manage and control the movement of floodwaters and people. These strategies are categorized either as structural or non-structural, depending on the method used. Structural flood mitigation is identified by the Northern Territory Government of Australia (2018) as methods “where physical structures are constructed or modified to reduce the impact of flooding on individual properties or whole catchments.” Some methods classified under this category include the building of dams, levees (embankment), culverts, canals, and bridges; the installation of flood-proofing devices, such as door flood barriers and flood vents; and the maintenance and improvement of such structures (Northern Territory Government of Australia, 2018). On the other hand, non-structural flood mitigation centers on improving the disaster-preparedness of people within the community (Reed, 2015). Reducing flood impact is achieved through this type of flood mitigation by establishing and following relocation plans for people and properties, property surveys, building and development 13 codes, flood modeling, and early warning systems, among other methods (Northern Territory Government of Australia, 2018). The two types of flood mitigation strategies are equally effective in minimizing the harmful effects of floods; however, according to the National Conference of State Legislatures (2019), structural flood mitigation strategies have become less favored due to the gradual weakening of existing structures. To address this, Reed (2015) suggests utilizing both types in future solutions for added reliability and safety. The Philippines, most especially metropolitan areas such as Metro Manila and Metro Cebu, actively utilizes various flood control structures combined with flood forecasts and warning systems to alleviate and prepare for devastating effects of inundations. Deficiencies in these existing solutions, however, were identified in a study by Gilbuena et al. (2013). Faulty structural designs and unreliable information and warning systems are among the enumerated problems that significantly contributed to the flooding in Metro Manila after Typhoon Ketsana (Ondoy) (Gilbuena et al., 2013). Traffic Congestion Solutions Akin to floods, traffic congestion may also be alleviated through structural and nonstructural methods. Still, these methods are further subdivided into two, temporary and virtuous, wherein the type of reduction method is determined by whether the population adjusts to the situation (temporary) or changes transportation preference (virtuous) accordingly (Smarter Cambridge Transport, 2016). Temporary methods are, as the name implies, not meant to be long-term solutions to traffic congestion; they must only be used to alleviate daily traffic conditions in the meantime while more large-scale and radical solutions are in progress. Included in this category are solutions such as 14 increasing road capacity, improving road junctions, designing and implementing traffic plans, rationing of road space, and strategizing traffic policies (Kumarage, 2004). In these methods, people adjust to the traffic situation in their respective communities. In contrast, virtuous methods provide solutions to improve the quality, convenience, and dependability of alternative transportation, particularly of public transportation systems (PTS). Solutions under this type allow for positive feedback loops to occur: people start preferring public vehicles, such as trains and buses, over private ones, which will increase the demand and operation times for the former. In turn, PTS becomes more reliable and appealing for the people; they will gradually shift away from driving private vehicles, ultimately relieving road congestion (Smarter Cambridge Transport, 2016). Improving the compatibility of the PTS with the benefitting population and accommodating their needs and wants is an example of a virtuous-type solution. In the Philippines, there are numerous road widening projects along major roads throughout the country. Additionally, daily road space rationing through the Unified Vehicular Volume Reduction Program (UVVRP), popularly known as number coding, is also observed in Metro Manila and other populous municipalities (Aguilar, 2018). These solutions are considered temporary methods in alleviating traffic. Although these can effectively reduce congestion problems, the fast rate of urbanization in metropolitan areas still renders these solutions inefficient in the long-run as the demand overwhelms the resources. Furthermore, Sergio R. Ortiz-Luis, Jr., president of the Philippine Exporters Confederation notes that the number coding system will urge people to purchase more private vehicles in an attempt to bypass it, ultimately defeating its purpose and potentially worsening traffic (Tubadeza, 2015). As such, solutions that combat the need for private vehicle usage are recommended (Miguel, 2019). 15 SMART Tunnel The Stormwater Management and Road Tunnel, or the SMART Tunnel, is an infrastructural innovation located in Kuala Lumpur, Malaysia intended for the alleviation of the immense flooding that occurs within the area while also functioning as an alternate route for road vehicles during strong weather disturbances (Varadharajan & Bailey, 2013). Its strategic location was established due to the topography of Kuala Lumpur, which makes it one of the most heavily affected areas during typhoons. The city is surrounded by numerous rivers with the center of the city situated near the convergence of two major rivers, the Klang and Gomback river, as seen in Figures 2 and 3. Rapid modernization of the areas from these bodies allow them to overflow during periods of rainfall, thus intensifying the magnitude of the impact of these calamities (Lai, 2016). This resulted in the construction of the SMART Tunnel in order to alleviate the damages caused by these flash floods by rerouting some of the water from these rivers. Figures 2 and 3. Junction of the Klang and Gombak River at the center of the city (River of Life (Phase 1), 2018; Lai, 2016) The tunnel finished construction in 2007 and began operation in the same year. As seen in Figure 4, the resulting infrastructure was composed of two parts: a 9.7-kilometer-long waterway for flood diversion and a 3 kilometers double-decked roadway segment (Soon, Isah, Ali, & Ahmad, 2017). It also has a diameter of 13 meters and a water capacity of 3,000,000 cubic meters for flood 16 diversion. Other components of the system include a holding pond, storage reservoir, diversion tunnel, road gates, and flood gates (Dethan, Kavitha, & Nair, 2018). The holding pod is located at the beginning of the tunnel for the collection of the water from the river and into the tunnel, while the storage reservoir is located at the end for flood discharge. These two features are connected by the diversion tunnel. On the other hand, the road and flood gates are structures used to manage the contained flood water during varied weather conditions. Figure 4. SMART Tunnel structure (Dethan, Kavitha, & Nair, 2018) Construction of SMART Tunnel Underground infrastructure projects, such as the SMART tunnel, require the execution of preliminary geotechnical investigations prior to their construction (Balasubramanian, 2016). This is essential since the geological features of the site for construction serves as a basis for the suitable methods and materials to be utilized, as well as the environmental impact of the project (Isah & Ali, 2015a). For the SMART Tunnel, it was found that the underlying features of the soil of Kuala Lumpur included much karstic limestone, thus resulting in the presence of numerous underground holes or caves (Parise, Gabrovsek, Kaufmann, & Ravbar, 2018). This, along with the urbanized 17 surface conditions of the target location, was heavily considered in finalizing the structure design in order to limit the risk of any disasters or disturbances to already existing landmarks. Despite the presence of numerous options for machinery, the Tunnel Boring Machine (TBM), specifically the Slurry Shield TBM, was chosen for the SMART tunnel (Isah & Ali, 2015b), which can be seen in Figure 5. This machine was deemed optimal for the project due to its efficiency given the geologic and groundwater conditions of the area. The Slurry Shield TBM allows continuous underground drilling and tunnel lining production while balancing the pressure all throughout the affected points of construction (Ochmański, 2015). Other than the hydraulics system in the machine that allows this consistency, the Slurry Shield TBM also fills in underground holes with a plaster-like substance for evenly distributed pressure and security of placement throughout the structure. Other than the advantages in terms of effectivity, utilization of a Slurry Shield TBM also ensures safer conditions on a surface level since it minimizes the risk of arising sinkholes (Kannapiran, 2005). Figure 5. Tunnel Boring Machine operation at the SMART Tunnel site (Kannapiran, 2005 ) Aside from the actual tunnel, other safety features were established within the tunnel structure. Among these include various systems for lighting, ventilation, radio and cellular communication, CCTV, thermal systems, and fire protection (Isah & Ali, 2015c). As seen in Figure 6, another unique feature of the tunnel is its double-decked roadway structure that allows travel in 18 only one direction per level. An emergency lane could also be found on top of each of these, as well as exit routes every 250 meters for sudden occurrences of disasters. Maintenance of the tunnel is also ensured on a weekly to monthly basis. Figure 6. Double deck interior of the SMART Tunnel (Isah & Ali, 2015c) Mechanism of the system The SMART Tunnel operates under three various conditions depending on the amount of rainfall and flood water height, which are shown in Figure 7. The first mode is the normal condition of performance, which occurs when there is low rainfall or no tropical cyclone. This allows the roadways to be utilized by vehicles while the water from the rivers are contained in the lowest floodway level of the tunnel. For the second mode, this involves closing off the lower roadway level for its utilization as a flood containment unit during moderate storms. Finally, during extreme typhoon conditions, all levels of the SMART tunnel would be utilized for holding of the flood water (Santhiman & Weei, 2006). Upon returning to normal weather conditions, the tunnel is slowly drained and cleared of debris to allow resumption of normal operations within a span of 48 hours (UNOSSC, 2012) 19 Figure 7. SMART Tunnel modes of operation (Santhiman & Weei, 2006) The resulting mode of operation of the SMART Tunnel is determined through the flood detection system of the structure (Kannapiran, 2005). Through the flood monitoring stations situated along the rivers near the tunnel, information regarding the criticality of the current water level is easily accessible and quickly analyzed. This data could then be easily disseminated to the public by the assigned authorities to do so through telecommunication methods, specifically SMS. Effects of tunnel utilization Utilization of the SMART Tunnel as a flood management system has been frequent, specifically 83 times during different periods of rainfall, and has resulted in effective flood mitigation since the beginning of its operation in 2007 (Isah & Ali, 2015). It has significantly minimized damage and risk from flood-related disasters throughout its surrounding areas. Consistent maintenance checks of its features have also been done to ensure proper execution of the tunnel objectives, specifically the conditions of the flood gates and proper cleaning of the tunnel. In the traffic mitigation aspect of the project, it has also been successful in improving the conditions of traffic flow through lessened travel time and more manageable state of traffic in the city (UNOSSC, 2012). Furthermore, travel time to the center of the city has significantly lessened to 4 minutes from the original time of 15 minutes. 20 METHODOLOGY Process Flowchart Collection of Flood and Traffic Data Sets Simulation of Proposed Tunnel System Data Analysis Collection of flood and traffic data sets Various government and research institutions were contacted to request for information, specifically data sets and statistics, regarding the state of flooding and traffic in Metro Manila. Maps of the existing and proposed mass transportation systems within the region and the environmental impact assessment of the Metro Manila Subway Project were obtained from the Department of Transportation. Other than this, flood height data in specific coordinates throughout Metro Manila were retrieved from Kaggle, an online data science and machine learning community, which was accessed through public data sets (Kaggle, 2019). The annual average daily traffic from the years 2012 to 2018 was also retrieved from the Metropolitan Manila Development Authority. From this, the respective traffic density for the major road systems of the area were computed (Al-Soby & Mousa, 2016). Additional traffic data and simulation models were then retrieved from the University of the Philippines National Center for Transportation Studies (UPNCTS). Simulation of Proposed Tunnel System A model on Vensim Software for simulating the floodway mechanism of the tunnel was designed for the determination of the effectiveness of the system during various rainfall conditions. 21 A variable representing Marikina River during these conditions was also included in the model as the basis for the activation of the actual flood mitigation system throughout the tunnel. Quantified values for precipitation, elevation, flood height, and river level were incorporated into the system. On the other hand, the program for the traffic mitigation system was designed for the determination of the optimal entry and exit points of the tunnel system. The data values for the traffic density in various routes of the Manila Road System were taken into account for the simulation model. Data Analysis The flood data set was subjected to multiple linear regression in order to identify the flood heights with respect to the elevation and precipitation in specific coordinates. Significant values, such as the R2 and p-values, were observed and interpreted to determine the validity and significance of the data. The coordinates with the highest flood elevation were then identified, and examined with the existing floodways in Metro Manila, in order to determine the optimal tunnel entry and exit points for effective flood mitigation. The traffic data was then analyzed to determine the most congested areas in Metro Manila, thus serving as a basis for the route of the tunnel within the region. The traffic simulation of the UP-NCTS was also viewed to aid in determining the ideal locations of exit points along the length of the tunnel. 22 RESULTS AND DISCUSSION Analysis of flood and traffic data sets Through linear regression of the elevation and precipitation data set, an R2 = 0.005879 and p-values of 0.000328 for elevation and 0.000702 for precipitation. The R2 level assesses the accuracy of the predictability of the model. A low R2 implies that the model cannot accurately predict the outcome if external factors that affect flood height are included. However, the p-values of the elevation and precipitation variables are smaller than 0.05 which indicates that there is strong evidence of a relationship between the variables and the flood height variable. Figure 8. Scatter plots of projected flood heights (left) and residuals (right) fitted to the map of Metro Manila The low value for the R2 variable of the linear regression of the elevation and precipitation data set was caused by the lack of other variables considered during the analysis. Several other factors such as soil type, presence of infrastructures, and environmental conditions during the 23 period of data collection were not addressed, explaining the low predictability (Pradita & Ariyaningsih, 2018). From the procured flood data set, it was found that the eastern part of Metro Manila was the most susceptible to flooding. It was then decided that the area of Marikina River near SM Marikina and Riverbanks was the most ideal location for the entry gate of the flood tunnel since it is easily flooded and a visual measuring tool for the river level has already been installed there. On the other hand, the Annual Average Daily Traffic (AADT) data set showed that the densest roads in terms of traffic are R6, R8, and C2, which are all in the Manila area. The C4 road, which is found in the eastern part of the region, was also found to attain the highest AADT. This allowed the determination of the direction of the tunnel system to begin from the Marikina area leading all the way to the Manila area in order to tackle both problems. The openings for the floodway system of the tunnel were then determined to open at a point near Marikina River with a route traced to the C4-R6 intersection, which would then be the opening for the road tunnel system, leading all the way to an exit point for the tunnel mechanism in Manila Bay, with the end of the road tunnel being at the C2-R8 intersection. Figure 9. Entry and exit points of the tunnel 24 The traffic data showed that the roads with the highest number of vehicles did not necessarily mean they had the highest density due to the varying lengths and widths of the roads (Al-Soby & Mousa, 2016). This explains why despite C4 having the highest AADT for each year, the dimensions of the road allowed it to be low in traffic congestion. Furthermore, the establishment of the tunnel in the designated locations allows an increase in road capacity within these heavily congested areas (Chowdhury et al., 2016). Simulation of Proposed Tunnel System The model was able to successfully show the conditions of the Marikina River with respect to various elevation and precipitation rates. From testing the model at a constant elevation, it was found that as the level of precipitation increased, so did the height of the resulting flood. As the flood height increased, the river level of the Marikina River also increased with the rate of increase depending on the tested precipitation. The inflow mechanism of the tunnel was then identified to be effective in mitigating the flooding in Marikina River at a rate of 0 to 0.875 meters of water to inflow through the tunnel opening. The resulting rate was successful in lessening the flood level of the Marikina River. Figure 10. Simulation model for the flood mechanism of the tunnel 25 The restriction of the tunnel inflow rate to 0 to 0.875 meters allows outflow of the Marikina River volume that is either equal or slightly greater than the volume increase rate of the river brought by any precipitation rate. The immediate-release through the tunnel system of any increased volume of water (tunnel outflow - river volume inflow from rainfall) allows a constant river level throughout the period of rainfall (O’Bannon & Ma, 2019). Other than ensuring that the river level would not be greater than 15 meters, the controlled rate allows it to never reach drastic conditions by ensuring a resulting river level that would not go lower than 10 meters. 26 SUMMARY AND CONCLUSION The study found that the R6-C4 intersection and R8-C2 intersection in Metro Manila were the optimal locations for the ends of the road tunnel system. The increase in road capacity within these areas would allow the effective mitigation of the traffic congestion present here. However, the floodway’s entry and exit points would be in SM Marikina and the Manila Bay. This system is seen to be effective as it allows the instant release of the increased river volume during any rainfall condition, constantly keeping the river in safe water level conditions. 27 RECOMMENDATIONS Future implementation of the study highly recommends the creation of a simulation model for the traffic component for the tunnel. 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