Flood Control Strategies PDF

Republic of the Philippines NUEVA ECIJA UNIVERSITY OF SCIENCE AND TECHNOLOGY Cabanatuan City, Nueva Ecija, Philippines COLLEGE OF ENGINEERING “Flood Control Strategies (Structural and Non-Structural Mitigation Measures) Alleviation of Flooding” Flood Control and Drainage Engineering Prepared by Ambrocio, Michael Angelo J. Cato, Jayson Gabriel S. Gaspar, John Ellis Pacio, Kenneth Clarence Pajarillaga, Camille Palon, Brixter BSCE-4E Engr. Derick Aldrin Esteban Instructor August 2024 Republic of the Philippines NUEVA ECIJA UNIVERSITY OF SCIENCE AND TECHNOLOGY Cabanatuan City, Nueva Ecija, Philippines Table of contents I. STRUCTURAL MITIGATION MEASURES A. Conventional methods 1. Levees 2. Floodwalls 3. Seawalls 4. Dams 5. Floodway 6. Spillway 7. Bypass and Diversion Channels 8. Structural Mitigation Through Improved Levee Design a. Controlled Overtopping and Breaching of Levees b. Levee Armoring c. Seepage Berms and Cutoff Walls B. Green technologies 1. Permeable pavement 2. Detention and Retention basin 3. Green roofs II. NONSTRUCTURAL FLOOD MITIGATION MEASURES 1. Structure elevation 2. Natural Systems 3. Risk Mapping 4. Hazard Forecasting, Early Warning Systems, and Emergency Plan 5. Dry and Wet Floodproofing 6. Land-Use Planning and Zoning 7. Public Education and Awareness 8. Wetland Restoration 9. Floodplain Management III. COMBINATION OF STRUCTURAL AND NONSTRUCTURAL MEASURES IV. CONSTRUCTION STANDARDS AND BUILDING CODES 1 Republic of the Philippines NUEVA ECIJA UNIVERSITY OF SCIENCE AND TECHNOLOGY Cabanatuan City, Nueva Ecija, Philippines Objectives Understand Key Concepts: Define and differentiate between structural and non-structural flood mitigation measures. Identify Structural Measures: List and describe various structural flood control methods, such as levees, dams, floodwalls, and stormwater management systems. Examine Non-Structural Approaches: Explore non-structural strategies like land use planning, flood forecasting, floodplain zoning, and public awareness programs. Assess Environmental Impact: Discuss the environmental and social implications of different flood control measures. Introduction Flooding is a natural disaster that affects millions of people worldwide, causing extensive damage to infrastructure, displacing communities, and leading to significant economic losses. As urbanization and climate change exacerbate the frequency and intensity of floods, it has become increasingly vital to develop and implement effective flood control strategies. These strategies can be broadly categorized into two main types: structural and non-structural mitigation measures. Structural measures involve physical interventions, such as building dams, levees, and floodwalls, designed to control and redirect floodwaters, thereby protecting vulnerable areas. Non-structural measures, on the other hand, focus on minimizing flood risk through planning, policy, and public awareness efforts, such as land-use regulations, early warning systems, and community education. In this lesson, we will explore both types of flood mitigation strategies, examining how they work individually and in combination to alleviate the impact of flooding. By understanding the strengths and limitations of these approaches, students will gain insights into developing integrated flood management solutions that are sustainable, effective, and adaptable to the challenges posed by a changing environment. 2 Republic of the Philippines NUEVA ECIJA UNIVERSITY OF SCIENCE AND TECHNOLOGY Cabanatuan City, Nueva Ecija, Philippines STRUCTURAL MITIGATION MEASURES Physical structures or engineering solutions intended to lessen or prevent the effects of flooding are known as structural flood mitigation methods. These steps are intended to protect infrastructure, regulate water flow and storage, and prevent property and human lives from being harmed by flooding. These structures lessen the severity and aftereffects of flooding events by controlling water flow and reducing exposure to flooding. The Importance of Structural Flood Mitigation Measures One of the primary benefits of structural flood mitigation measures is their ability to provide immediate and tangible protection to communities. Levees and floodwalls, for example, are designed to hold back rising waters, preventing them from inundating homes, businesses, and critical infrastructure. These structures can significantly reduce the extent of flooding in urban and rural areas, thereby minimizing property damage and loss of life. STRUCTURAL MITIGATION MEASURES I. Levees Levees are embankments or natural ridges built along the edges of rivers, lakes, or other bodies of water to prevent flooding of the adjacent land. They are designed to hold back water, particularly during periods of high flow, such as during heavy rains or snowmelt, to protect populated areas, agricultural land, or infrastructure from being flooded. 3 Republic of the Philippines NUEVA ECIJA UNIVERSITY OF SCIENCE AND TECHNOLOGY Cabanatuan City, Nueva Ecija, Philippines Levees vs. Dikes Levee - Location: Built along the sides of rivers, lakes, or coastal areas. - Purpose: To prevent floodwaters from spilling over into adjacent land, protecting areas that are usually dry. - Structure: Typically runs parallel to the water body and is designed to contain water during high flow conditions. Dike - Location: Constructed to separate specific low-lying areas from surrounding water bodies, often in reclaimed land or coastal regions. - Purpose: To keep water out of areas that are below the general water level, often used to protect agricultural or industrial land. - Structure: Can be built around entire areas, creating a barrier that keeps water out, essentially enclosing a region. In summary, levees control water flow along existing water bodies, while dikes enclose and protect specific low-lying areas from outside water. Strengths of Levees: Primary Defense: Levees are highly effective in preventing flooding in areas adjacent to rivers, lakes, or coastal regions by containing high water levels and preventing them from spilling over into populated areas. Immediate Impact: When properly designed and maintained, levees can provide immediate and substantial protection against flooding, helping to safeguard lives, properties, and infrastructure. 4 Republic of the Philippines NUEVA ECIJA UNIVERSITY OF SCIENCE AND TECHNOLOGY Cabanatuan City, Nueva Ecija, Philippines Weaknesses of Levees: Design Limitations: Levees are designed to handle specific flood levels. If water levels exceed this design capacity, the levee can be overtopped, leading to sudden and severe flooding. Structural Failure: Levees can breach if they are not adequately maintained, if they are poorly constructed, or if they experience pressure beyond their design limits. Breaching can result in catastrophic flooding, often more severe than if no levee were present. Repair and Reinforcement: After significant flood events, levees may need repairs or reinforcement, further adding to the maintenance burden. Areas of Application - Riverine Systems: Levees are extensively used along rivers to manage and control water flow. They help prevent rivers from overflowing their banks during heavy rains or snowmelt, protecting communities, homes, and infrastructure situated in floodplains. - Urban Areas: Levees are crucial in urban settings to protect cities and towns from floodwaters. They help manage flood risks by keeping river or lake waters from spilling over into streets, buildings, and other infrastructure. - Floodplains: Levees are also important in floodplains, where they help contain and redirect floodwaters to minimize the impact on the surrounding areas. 5 Republic of the Philippines NUEVA ECIJA UNIVERSITY OF SCIENCE AND TECHNOLOGY Cabanatuan City, Nueva Ecija, Philippines Levees in the Philippines 1. Marikina River Levees The Marikina River Levees are crucial in protecting the city of Marikina, which is located in a flood-prone area along the Marikina River. These levees are designed to manage the river's flow and prevent overflow during heavy rains and typhoons. They have been part of a larger flood management system that includes river dredging and the construction of flood walls. 2. Pasig River Levees The Pasig River Levees help control flooding along the Pasig River, which flows through several cities in Metro Manila. These levees are part of a broader effort to manage river flooding and improve waterway conditions. The levees are intended to protect surrounding communities from potential floodwaters and are complemented by other flood mitigation measures. 6 Republic of the Philippines NUEVA ECIJA UNIVERSITY OF SCIENCE AND TECHNOLOGY Cabanatuan City, Nueva Ecija, Philippines 3. Pampanga River Levees The Pampanga River Levees are designed to manage flooding in the Pampanga River Basin, an area that experiences frequent flooding during the rainy season. These levees help protect agricultural lands, residential areas, and infrastructure from the impacts of river overflow. II. Floodwalls Floodwalls are vertical barriers designed to prevent or control the flow of water and protect areas from flooding. Unlike levees, which are typically wide embankments made of earth, floodwalls are usually constructed from concrete, steel, or other durable materials. They are particularly useful in urban areas where space is limited, and building wide embankments isn't feasible. 7 Republic of the Philippines NUEVA ECIJA UNIVERSITY OF SCIENCE AND TECHNOLOGY Cabanatuan City, Nueva Ecija, Philippines Strengths of Floodwalls: Compact Design: Floodwalls require significantly less space than levees, making them ideal for densely populated urban areas where land is limited. Their vertical design allows for effective flood protection without the need for wide embankments. High Resistance: Constructed from materials like reinforced concrete or steel, floodwalls are highly durable and can withstand significant water pressure. They are designed to resist the impact of strong floodwaters, including storm surges and rapid river flows. Long Lifespan: When properly maintained, floodwalls can last for decades, providing long-term protection against flooding. Weaknesses of Floodwalls: Expensive Construction: Floodwalls are generally more expensive to construct than levees, especially when designed to protect large areas or withstand high water pressure. The use of reinforced materials like concrete and steel, along with the complexity of construction, contributes to higher costs. Barrier to Wildlife: Floodwalls can act as barriers to wildlife, preventing the movement of animals and altering natural habitats. This can be particularly problematic in areas where seasonal flooding is part of the natural ecological cycle. Vulnerability to Extreme Events: While floodwalls are designed to withstand significant water pressure, extreme events like major storm surges, earthquakes, or severe floods can potentially overwhelm or damage them. A failure in a floodwall can lead to catastrophic flooding, especially if it occurs suddenly. Areas of Application of Floodwalls: - Protection of Cities and Towns: Floodwalls are widely used in urban environments where space constraints make levees impractical. They protect densely populated areas, including residential neighborhoods, commercial districts, and critical infrastructure, from river or coastal flooding. - Defense Against Storm Surges: Coastal regions are particularly vulnerable to storm surges and rising sea levels. Floodwalls are a key component of coastal defense systems, 8 Republic of the Philippines NUEVA ECIJA UNIVERSITY OF SCIENCE AND TECHNOLOGY Cabanatuan City, Nueva Ecija, Philippines protecting coastal cities, ports, and infrastructure from the impact of ocean water during storms. - Flood Management Along Rivers: Floodwalls are used along rivers to manage flood risks in areas where levees might not be feasible or sufficient. They protect adjacent communities, agricultural lands, and infrastructure from river overflows during periods of heavy rain or snowmelt. Floodwalls in the Philippines 1. Cebu Coastal Floodwalls In Cebu City, floodwalls have been constructed along certain coastal areas to protect against storm surges and rising sea levels. These floodwalls are particularly important in protecting the city’s waterfront areas, including ports and commercial zones, from flooding during typhoons and high tides. 2. Laguna Lake Shore Floodwalls The floodwalls along the shore of Laguna de Bay, the largest lake in the Philippines, are designed to protect surrounding towns and cities from rising water levels. These floodwalls are part of a larger effort to manage flooding in the Laguna Lake Basin, particularly during typhoons and periods of heavy rain, which can cause the lake’s water levels to rise significantly. 3. San Juan River Floodwalls The San Juan River, which runs through parts of San Juan City and Manila, has floodwalls constructed along its banks to control flooding. These floodwalls are crucial in preventing the river from overflowing, particularly during the monsoon season when the risk of flooding is high. The floodwalls also help protect residential and commercial areas adjacent to the river. 9 Republic of the Philippines NUEVA ECIJA UNIVERSITY OF SCIENCE AND TECHNOLOGY Cabanatuan City, Nueva Ecija, Philippines III. Seawalls Seawalls are coastal defence structures designed to protect shorelines, harbours, and coastal communities from the effects of ocean waves, storm surges, and rising sea levels. These structures are typically built parallel to the coast and serve as a barrier that absorbs and reflects the energy of incoming waves, preventing erosion and flooding of the land behind them. Strengths of Seawalls: Wave Energy Reduction: Seawalls are highly effective at reducing the energy of incoming waves, protecting the shoreline from erosion, storm surges, and high tides. They act as a physical barrier, preventing water from reaching the land behind them. Robust Construction: Seawalls are typically made from reinforced concrete, steel, or stone, which makes them durable and capable of withstanding harsh marine conditions. When properly maintained, they can last for decades, providing long-term protection. Preservation of Economic Activities: By protecting harbors, ports, and other coastal infrastructure, seawalls ensure the continuity of economic activities such as shipping, tourism, and fishing. 10 Republic of the Philippines NUEVA ECIJA UNIVERSITY OF SCIENCE AND TECHNOLOGY Cabanatuan City, Nueva Ecija, Philippines Weaknesses of Seawalls: Limited Flexibility: Once built, seawalls are not easily modified or adapted to changing conditions, such as increased sea levels or shifts in coastal dynamics. This inflexibility can make them less effective over time as environmental conditions change. Limited Longevity: Despite their durability, seawalls have a finite lifespan and may eventually need to be replaced or upgraded, especially in the face of rising sea levels and increasingly severe storms due to climate change. Restricted Access: In some cases, seawalls can limit access to the beach or shoreline, reducing recreational opportunities for the public. This can lead to social tensions, especially in communities that rely on beach access for tourism or local enjoyment. Areas of Application of Seawalls: - Harbors and Ports: Coastal cities with harbors or ports often use seawalls to protect against the erosive forces of waves and to maintain the integrity of the port facilities. These seawalls help ensure the continuous operation of shipping and other maritime activities. - Beach Resorts: Seawalls are used in beachfront resorts and tourist areas to protect against coastal erosion and to maintain the attractiveness of the beach. These structures help preserve the sandy shorelines that are vital to the tourism industry. - Tsunami-Prone Regions: In areas at risk of tsunamis, seawalls can provide some level of protection by absorbing and reducing the impact of the waves. While not foolproof, these seawalls can mitigate damage and reduce the severity of flooding caused by tsunamis. Seawalls in the Philippines 1. Manila Bay Seawall One of the most famous seawalls in the Philippines, the Manila Bay Seawall runs along Roxas Boulevard in Manila. It was originally constructed to protect the city from storm surges and high tides coming from Manila Bay. The seawall also serves as a popular 11 Republic of the Philippines NUEVA ECIJA UNIVERSITY OF SCIENCE AND TECHNOLOGY Cabanatuan City, Nueva Ecija, Philippines promenade, where people gather to watch the famous Manila Bay sunset. Despite its historical significance and iconic status, the seawall has required periodic reinforcement due to the strong wave action and occasional flooding. 2. Dumaguete City Seawall Dumaguete City’s seawall stretches along the Rizal Boulevard, a popular waterfront area in the city. This seawall protects the coastal road and nearby establishments from wave action and erosion. The area is also a key social and recreational space for residents and tourists, with the seawall providing both protection and aesthetic value to the city's coastline. 3. Legazpi City Seawall The seawall in Legazpi City protects the urban area from the strong waves of Albay Gulf. This structure is particularly important given the city’s proximity to the active Mayon 12 Republic of the Philippines NUEVA ECIJA UNIVERSITY OF SCIENCE AND TECHNOLOGY Cabanatuan City, Nueva Ecija, Philippines Volcano, which can cause lahar flows during heavy rains that could reach the coastline. The seawall helps protect the city from both marine and volcanic-related flooding. Breakwater Breakwaters are structures built to protect coastal areas, harbors, and shorelines from the force of waves and to reduce erosion. In the Philippines, a country with extensive coastlines and numerous islands, breakwaters play a crucial role in protecting both natural and man-made environments. 1. Manila Bay Breakwater One of the most significant breakwaters in the Philippines is located in Manila Bay. This breakwater is part of the larger effort to protect the shoreline of Metro Manila, including the areas around Roxas Boulevard and the Manila Yacht Club. It helps 13 Republic of the Philippines NUEVA ECIJA UNIVERSITY OF SCIENCE AND TECHNOLOGY Cabanatuan City, Nueva Ecija, Philippines mitigate the impact of strong waves and storm surges, which are common in this area due to typhoons and other weather disturbances. IV. Dams A dam is a large structure built across a river, stream, or other body of water to block, control, or divert the flow of water. Dams serve a variety of important functions, including water storage, flood control, hydroelectric power generation, irrigation, and recreation. They are essential infrastructure in many parts of the world, providing benefits for agriculture, industry, and human settlements. Purposes of Dams: 1. Water Supply: ○ Dams provide a reliable source of water for domestic, agricultural, and industrial use. By storing water in reservoirs, dams ensure a steady supply even during dry periods. 2. Flood Control: ○ Dams help manage flood risk by controlling the flow of water downstream. During heavy rains or snowmelt, dams can store excess water and release it gradually, reducing the likelihood of flooding. 3. Hydropower Generation: ○ Many dams are equipped with turbines and generators to produce electricity. Hydropower is a renewable energy source that relies on the flow of water to generate electricity, making it a key component of energy systems in many countries. 14 Republic of the Philippines NUEVA ECIJA UNIVERSITY OF SCIENCE AND TECHNOLOGY Cabanatuan City, Nueva Ecija, Philippines Types of Dams 1. Sabo Dam A sabo dam is a type of dam constructed primarily to prevent the flow of sediment, debris, and rocks carried by rivers or streams, especially in mountainous regions. The term "sabo" comes from the Japanese word "sabo," which means "sand control." These dams are crucial in areas prone to landslides, volcanic activity, and heavy rainfall, where they help protect downstream areas from sediment-related disasters, such as mudflows or debris flows. One notable example of a sabo dam in the Philippines is the Busol Sabo Dam located in the Bicol region. This dam is part of a larger network of sabo dams constructed around Mayon Volcano to mitigate the risks of lahar flows following volcanic eruptions. Busol Sabo Dam Purpose: The Busol Sabo Dam is designed to trap and control volcanic debris, including lahars, which are mudflows composed of volcanic material, water, and debris that can be triggered by heavy rainfall or the melting of snow during an eruption. These lahars pose significant risks to the surrounding communities. 2. Multipurpose Dam A multipurpose dam is a dam that is designed and constructed to serve multiple functions, rather than just a single purpose such as water storage or flood control. These dams play a crucial role in managing water resources efficiently by combining various uses that are essential for regional development and environmental sustainability. 15 Republic of the Philippines NUEVA ECIJA UNIVERSITY OF SCIENCE AND TECHNOLOGY Cabanatuan City, Nueva Ecija, Philippines San Roque Dam Functions: 1. Flood Control: San Roque Dam plays a critical role in flood management along the Agno River Basin, one of the largest river systems in Luzon. By regulating the flow of the river, the dam reduces the risk of flooding in downstream areas, especially during the typhoon season. 2. Hydropower Generation: The dam is equipped with a hydroelectric power plant that has a capacity of up to 345 megawatts. This makes it one of the largest hydroelectric power producers in the country, supplying electricity to the Luzon grid and contributing significantly to the region's energy needs. 3. Irrigation: San Roque Dam supports the irrigation of approximately 70,000 hectares of farmland in Pangasinan and neighboring provinces. This ensures a reliable water supply for agriculture, particularly in rice production, which is vital for the local economy. 4. Water Supply: The dam also contributes to the domestic water supply in the surrounding regions, supporting both agricultural and urban needs. 5. Recreation: The reservoir formed by the dam, known as San Roque Lake, has become a site for recreational activities such as fishing, boating, and tourism, boosting local economic opportunities. 16 Republic of the Philippines NUEVA ECIJA UNIVERSITY OF SCIENCE AND TECHNOLOGY Cabanatuan City, Nueva Ecija, Philippines Strengths of Dams: Reliable Water Source: Dams provide a dependable source of water for domestic use, agriculture, and industry, particularly in regions where natural water supply is unpredictable. Flood Management: Dams can significantly reduce the risk of downstream flooding by controlling the release of water during periods of heavy rainfall or snowmelt. They can hold back excess water and release it gradually, preventing sudden, devastating floods. Renewable Energy Source: Dams used for hydropower generation produce electricity without emitting greenhouse gases, making them a clean and renewable energy source. Weaknesses of Dams: Expensive to Build: Dams are costly to design and construct, requiring significant financial investment. Large-scale dam projects can run into billions of dollars, and cost overruns are common. Dam Failure: Although rare, dam failures can have catastrophic consequences, including loss of life, widespread flooding, and significant environmental and economic damage. The risk of failure can be exacerbated by factors such as poor design, inadequate maintenance, natural disasters, and aging infrastructure. Altered Water Temperature and Quality: Dams can change the temperature and chemical composition of water released downstream, potentially harming aquatic life and affecting water quality for human use. Other Dams in the Philippines The Philippines has several dams across the country that play crucial roles in water supply, irrigation, flood control, and hydropower generation. Here are some notable examples: 1. Angat Dam Angat Dam is one of the most significant dams in the Philippines, providing water supply to Metro Manila and irrigation to surrounding agricultural areas. It also generates 17 Republic of the Philippines NUEVA ECIJA UNIVERSITY OF SCIENCE AND TECHNOLOGY Cabanatuan City, Nueva Ecija, Philippines hydroelectric power. The dam creates the Angat Reservoir, which is crucial for water storage and flood control. The dam's water management is vital for the drinking water needs of millions of people in Metro Manila. 2. Pantabangan Dam Pantabangan Dam is one of the oldest and largest dams in the Philippines, constructed in the 1970s. It is primarily used for irrigation, supplying water to vast agricultural lands in Nueva Ecija and surrounding provinces, known as the "Rice Granary of the Philippines." The dam also generates electricity through its hydroelectric power plant and serves as a flood control structure. 3. La Mesa Dam La Mesa Dam is part of the water supply system for Metro Manila, serving as the final reservoir before water is distributed to the city's households. The La Mesa Watershed, where the dam is located, also serves as a protected area that helps 18 Republic of the Philippines NUEVA ECIJA UNIVERSITY OF SCIENCE AND TECHNOLOGY Cabanatuan City, Nueva Ecija, Philippines maintain the quality of water. La Mesa Dam is smaller compared to others like Angat or San Roque but is critically important for Metro Manila's water supply. V. Floodway A floodway is a designated area of land that is intentionally preserved or engineered to manage excess water during flooding events. The purpose of a floodway is to allow floodwaters to flow freely and safely through a particular area, reducing the risk of flooding in surrounding communities and infrastructure. Floodways are crucial components of floodplain management strategies, helping to mitigate the impacts of floods by directing water away from developed areas. Importance of Floodways: Flood Risk Reduction: Floodways help manage and reduce the risk of flooding in urban and rural areas by providing a controlled pathway for floodwaters. Environmental Management: Floodways can also serve as natural habitats for wildlife, helping to maintain biodiversity and ecological balance in flood-prone areas. Economic Benefits: By preventing or minimizing flood damage, floodways help protect infrastructure, homes, and agricultural lands, reducing the economic impact of floods. Strengths of Floodways: Lower Construction and Maintenance Costs: Floodways can be more cost-effective than constructing large dams or levee systems, especially in areas where natural topography already provides a suitable path for excess water. 19 Republic of the Philippines NUEVA ECIJA UNIVERSITY OF SCIENCE AND TECHNOLOGY Cabanatuan City, Nueva Ecija, Philippines Can Handle Varying Water Levels: Floodways are designed to handle a range of water levels, making them adaptable to different flood events. They can manage both regular, seasonal flooding and more extreme flood events. Complementary to Other Systems: Floodways can be integrated with other flood management systems like levees, dams, and reservoirs, providing an additional layer of protection and flexibility in flood management strategies. Weaknesses of Floodways: Large Land Requirements: Floodways often require large areas of land to function effectively. This can lead to the displacement of communities or the loss of land that could otherwise be used for agriculture, housing, or other purposes. Potential for Erosion: The concentrated flow of water through a floodway can lead to erosion of the land and riverbanks within and downstream of the floodway. This can result in sedimentation issues and the degradation of water quality. Requires Regular Maintenance: Floodways need to be maintained to ensure they remain effective. This includes clearing debris, managing vegetation, and monitoring for erosion or sediment buildup. Floodway in the Philippines - Manggahan Floodway Location: The Manggahan Floodway is located in Metro Manila, stretching from the Pasig River in the city of Pasig to the Laguna de Bay in Taytay, Rizal. Purpose: The Manggahan Floodway was constructed to divert excess water from the Pasig River during periods of heavy rainfall, particularly during typhoons and monsoon seasons. By redirecting water to the Laguna de Bay, the floodway helps prevent the Pasig River from overflowing and flooding densely populated areas in Metro Manila, such as Mandaluyong, Makati, and Manila. Construction: The Manggahan Floodway was completed in 1986 as part of the Metro Manila Flood Control Project, which aimed to protect the capital region from devastating floods. 20 Republic of the Philippines NUEVA ECIJA UNIVERSITY OF SCIENCE AND TECHNOLOGY Cabanatuan City, Nueva Ecija, Philippines Design and Function: The floodway is about 10.7 kilometers long and has a design capacity to divert 2,400 cubic meters of water per second. During periods of heavy rainfall, water from the Marikina River and the Pasig River is channeled through the Manggahan Floodway, reducing the risk of flooding in urban areas. Challenges and Issues: Over the years, the Manggahan Floodway has faced challenges such as siltation, encroachments by informal settlers, and reduced carrying capacity due to sediment buildup and garbage. These issues have affected its efficiency, leading to calls for dredging, clearing of obstructions, and improved management. VI. Spillway A spillway is a crucial structure in dam engineering, designed to safely release excess water from a reservoir to prevent overflow or damage to the dam. It serves as a safety valve for the dam, ensuring that water levels do not exceed the capacity of the reservoir, especially during periods of heavy rainfall, snowmelt, or other conditions that lead to increased water inflow. Importance of Spillways: Flood Management: Spillways play a critical role in flood management by releasing excess water in a controlled manner, reducing the risk of flooding downstream. Dam Safety: By preventing overtopping, spillways protect the structural integrity of dams, ensuring their longevity and safety. 21 Republic of the Philippines NUEVA ECIJA UNIVERSITY OF SCIENCE AND TECHNOLOGY Cabanatuan City, Nueva Ecija, Philippines Environmental Protection: Controlled water release helps mitigate the environmental impact of large-scale water discharge, protecting downstream ecosystems and communities. Strengths of Spillways: Protects Dam Integrity: By providing a controlled outlet for excess water, spillways protect the structural integrity of the dam. This safety feature is critical for preventing dam breaches and ensuring the long-term stability of the structure. Adjustable Flow Rates: Gated spillways allow for precise control over the amount of water released, enabling dam operators to manage reservoir levels in response to varying inflows and downstream requirements. Floodplain Management: Spillways help manage water levels in a way that can support floodplain ecosystems, maintaining the natural balance in areas prone to seasonal flooding. Weaknesses of Spillways: Water Quality Issues: The rapid release of large volumes of water through a spillway can lead to changes in water quality, such as increased turbidity, temperature changes, or the release of accumulated sediments and pollutants, which can harm aquatic life. Relocation Costs: In some cases, communities may need to be relocated to make way for spillway construction, leading to social and economic disruption. Land Use Restrictions: The areas downstream of spillways often need to be kept free of development due to the risk of flooding. This can limit land use and development opportunities in these regions. Spillways in the Philippines 1. San Roque Dam Spillway Location: San Manuel, Pangasinan 22 Republic of the Philippines NUEVA ECIJA UNIVERSITY OF SCIENCE AND TECHNOLOGY Cabanatuan City, Nueva Ecija, Philippines Description: The San Roque Dam, a large multipurpose dam, includes a spillway system designed to handle high inflows from the Agno River. The spillway is crucial for flood control, irrigation, and power generation. Function: The spillway directs excess water away from the reservoir, helping manage flood risks in the Agno River Basin and downstream areas. It also includes energy dissipation features to reduce the impact of discharged water on the environment. 2. Magat Dam Spillway Location: Ramon, Isabela Description: The Magat Dam features a spillway that helps regulate the water levels of the Magat Reservoir. This dam is important for irrigation and hydroelectric power generation in the Cagayan Valley. Function: The spillway controls excess water flow from the reservoir, preventing overflow and mitigating the risk of flooding in the Cagayan Valley and downstream areas. 23 Republic of the Philippines NUEVA ECIJA UNIVERSITY OF SCIENCE AND TECHNOLOGY Cabanatuan City, Nueva Ecija, Philippines 3. Ipo Dam Spillway Location: Norzagaray, Bulacan Description: The Ipo Dam is part of the Angat-Ipo-La Mesa water system, and it includes a spillway designed to manage water flow and maintain reservoir levels. Function: The spillway ensures that excess water is safely released from the Ipo Reservoir, which helps in the overall management of water supply to Metro Manila. VII. Bypass and Diversion Channels Bypass Channels A bypass channel is a specially constructed or natural watercourse designed to divert water around a specific area, such as a city or agricultural land, to prevent flooding or reduce water flow impact. It essentially "bypasses" the area at risk by redirecting water flow to a different location. Advantages: Flood Risk Reduction: By redirecting floodwaters, bypass channels protect vulnerable areas from flooding, reducing the risk of property damage and loss of life. Environmental Impact: When well-designed, bypass channels can mitigate environmental damage by preventing uncontrolled flooding in sensitive areas. Flexibility: Bypass channels can be adjusted to handle varying flood conditions and can be integrated with other flood management systems. 24 Republic of the Philippines NUEVA ECIJA UNIVERSITY OF SCIENCE AND TECHNOLOGY Cabanatuan City, Nueva Ecija, Philippines Disadvantages: High Construction Costs: Building a bypass channel can be expensive, particularly if it requires significant excavation or the construction of complex structures. Maintenance Requirements: Regular maintenance is needed to keep the channel clear of debris and sediment to ensure effective operation. Land Use Impact: The construction of a bypass channel may require significant land use changes and can affect local ecosystems and communities. Bypass Channels in the Philippines 1. Albay Gulf Bypass Channel Location: Albay Province, Philippines Description: The Albay Gulf Bypass Channel is part of the flood control infrastructure in Albay, designed to manage floodwaters from the surrounding river systems and prevent flooding in urban areas. Purpose: The bypass channel helps divert excess water from the rivers that flow into Albay Gulf, reducing the risk of flooding in the city of Legazpi and surrounding communities. Features: This channel includes embankments and control structures to manage the flow and direction of floodwaters. 2. Cagayan River Floodway Location: Cagayan Valley, Philippines Description: The Cagayan River Floodway is designed to manage and redirect excess water from the Cagayan River to prevent flooding in nearby areas. It plays a vital role in flood control in the Cagayan Valley region. Purpose: By diverting overflow from the Cagayan River, the floodway helps reduce flood risks in agricultural lands and settlements in the valley, supporting agricultural productivity and protecting local communities. Features: The floodway includes engineered channels and structures to handle high volumes of water during flood events. 25 Republic of the Philippines NUEVA ECIJA UNIVERSITY OF SCIENCE AND TECHNOLOGY Cabanatuan City, Nueva Ecija, Philippines Diversion Channels A diversion channel is a watercourse constructed to divert water from one river or stream to another. This can be done for various purposes, including flood control, irrigation, or water supply. The primary goal is to redirect water flow to manage its distribution and usage more effectively. Advantages: Resource Management: Diversion channels can help optimize water use for agriculture, industrial processes, or municipal water supply. Flood Prevention: By redirecting water away from flood-prone areas, diversion channels can reduce the risk of flooding and protect infrastructure. Economic Benefits: Improved water management through diversion channels can boost agricultural productivity and support economic development. Disadvantages: Environmental Impact: Diverting water can affect ecosystems, disrupt natural water flow patterns, and impact aquatic life in both the source and receiving watercourses. Construction and Maintenance Costs: Building and maintaining diversion channels can be costly, particularly if they require significant engineering or land acquisition. Complexity: Managing and regulating diversion channels can be complex, requiring careful planning and coordination to avoid unintended consequences. Diversion Channels in the Philippines 1. Agno River Irrigation System Location: Pangasinan, Central Luzon, Philippines Description: The Agno River Irrigation System features diversion channels that redirect water from the Agno River to irrigate agricultural fields in the region. Purpose: These diversion channels support irrigation for crops, enhancing agricultural productivity and ensuring reliable water supply for farming in the Pangasinan area. 26 Republic of the Philippines NUEVA ECIJA UNIVERSITY OF SCIENCE AND TECHNOLOGY Cabanatuan City, Nueva Ecija, Philippines Features: The system includes channels, canals, and distribution networks designed to effectively manage and utilize water resources for irrigation. 2. Laguna Lake Development Authority (LLDA) Flood Control Projects Location: Laguna de Bay Basin, Southern Luzon, Philippines Description: Various flood control projects managed by the Laguna Lake Development Authority include diversion channels to manage water flow and reduce flooding around Laguna Lake. Purpose: These channels help in flood management by diverting excess water from surrounding rivers and streams away from populated areas and into Laguna Lake or designated flood storage areas. Features: The projects involve constructing and maintaining diversion channels, embankments, and other infrastructure to manage floodwaters effectively. STRUCTURAL MITIGATION THROUGH IMPROVED LEVEE DESIGN OR MODIFICATION Structural mitigation through improved levee design or modification involves enhancing the effectiveness and resilience of levees to better protect areas from flooding. This approach is crucial in adapting to changing climate conditions, increased urbanization, and evolving flood risk profiles. Here’s a comprehensive overview of how improved levee design or modification can contribute to more effective flood management: A. Controlled Overtopping and Breaching of Levees Controlled Ovetopping Controlled overtopping refers to the deliberate design and management of levees to allow water to flow over the top under controlled conditions. This approach is typically used to manage extreme flood events when water levels exceed the capacity of the levee. 27 Republic of the Philippines NUEVA ECIJA UNIVERSITY OF SCIENCE AND TECHNOLOGY Cabanatuan City, Nueva Ecija, Philippines Benefits: Reduced Risk of Catastrophic Failure: Controlled overtopping can prevent more severe damage by allowing water to flow in a controlled manner, reducing the risk of a sudden and uncontrolled levee breach. Managed Flooding: By directing overtopping to specific areas, controlled overtopping can help manage floodwaters and reduce the impact on critical infrastructure and populated areas. Cost-Effective: Designing levees to accommodate controlled overtopping can be more cost-effective than building them to handle the highest possible flood levels. Challenges: Maintenance Requirements: Areas designed for controlled overtopping must be regularly maintained to ensure they remain effective and do not become prone to excessive erosion or damage. Land Use Impact: The designated overtopping zones must be managed to avoid significant damage to land and property in those areas. Controlled Breaching Controlled breaching involves intentionally creating a breach in a levee to relieve flood pressure and prevent more catastrophic failures. This approach is typically used as a last resort to manage extreme flooding situations. 1. Benefits: ○ Flood Pressure Relief: Controlled breaching can reduce flood pressures on levees, preventing more severe and uncontrolled breaches that could lead to extensive damage. ○ Prevention of Catastrophic Failure: By creating a controlled breach, the risk of sudden and catastrophic levee failure is reduced, helping to manage floodwaters more effectively. 28 Republic of the Philippines NUEVA ECIJA UNIVERSITY OF SCIENCE AND TECHNOLOGY Cabanatuan City, Nueva Ecija, Philippines 2. Challenges: ○ Unpredictable Outcomes: Even with controlled breaching, the behavior of water flow can be unpredictable, and there is a risk of unintended consequences. ○ Significant Damage: Controlled breaching can cause significant damage to the areas where the breach occurs, requiring careful planning and management to minimize impacts. B. Levee Armoring Levee armoring is a technique used to enhance the durability and effectiveness of levees by protecting their surfaces from erosion, damage, and other forms of degradation. This process involves applying various materials and methods to reinforce and protect the levee structure. Here's a detailed overview of levee armoring: Purpose of Levee Armoring 1. Erosion Protection: Armoring helps prevent erosion caused by flowing water, wind, and other environmental factors. This is crucial for maintaining the structural integrity of the levee and ensuring its long-term effectiveness. 2. Increased Durability: By reinforcing the surface, armoring increases the lifespan of the levee, reducing the need for frequent repairs and maintenance. 3. Flood Risk Reduction: Proper armoring helps the levee withstand higher water pressures and extreme weather events, thus improving flood protection for adjacent areas. Common Armoring Techniques 1. Riprap: Description: Riprap consists of large, loose rocks or stones placed on the surface of the levee to prevent erosion. The rocks are typically arranged in a layered manner. Advantages: Riprap provides robust protection against erosion and is relatively easy to install. It can withstand strong water flows and is effective in high-energy environments. 29 Republic of the Philippines NUEVA ECIJA UNIVERSITY OF SCIENCE AND TECHNOLOGY Cabanatuan City, Nueva Ecija, Philippines Disadvantages: It can be expensive to install, and the large rocks may be displaced over time, requiring periodic maintenance. 2. Gabions: Description: Gabions are wire mesh baskets filled with rocks or other materials. They are used to create a protective barrier against erosion. Advantages: Gabions are flexible and can conform to irregular surfaces. They are durable and provide effective erosion control. Disadvantages: Gabions can be visually intrusive and may require maintenance if the wire mesh becomes damaged or rusted. C. Seepage Berms and Cutoff Walls Seepage berms and cutoff walls are critical components in levee and flood control systems designed to manage and mitigate the risks associated with seepage and internal erosion. 30 Republic of the Philippines NUEVA ECIJA UNIVERSITY OF SCIENCE AND TECHNOLOGY Cabanatuan City, Nueva Ecija, Philippines Seepage Berms Seepage berms are engineered embankments or structures placed at the base or along the sides of levees to control and manage seepage, the slow movement of water through or beneath the levee. Purpose: Reduce Seepage: Berms help to intercept and manage seepage water before it can weaken the levee structure or cause erosion. Stabilize Levees: By controlling seepage, berms contribute to the overall stability of the levee, preventing issues such as piping or internal erosion that can lead to failure. Advantages: Enhanced Levee Stability: By managing seepage effectively, berms help maintain the structural integrity of levees and prevent failures. Cost-Effective: Seepage berms are relatively simple and cost-effective compared to more complex engineering solutions. Disadvantages: Maintenance Needs: Regular maintenance is required to ensure that seepage berms remain effective, especially in areas prone to erosion or water flow changes. Land Use Impact: The construction of berms can affect land use, particularly if they occupy significant space or alter natural drainage patterns. 31 Republic of the Philippines NUEVA ECIJA UNIVERSITY OF SCIENCE AND TECHNOLOGY Cabanatuan City, Nueva Ecija, Philippines Cutoff Walls Cutoff walls are vertical barriers constructed to block or control the flow of water through the base of a levee or dam. They are used to prevent seepage and reduce the risk of internal erosion. Purpose: Control Seepage: Cutoff walls prevent water from seeping through the levee’s foundation, which can cause internal erosion and lead to failure. Protect Levee Foundations: By blocking seepage paths, cutoff walls protect the structural integrity of the levee and extend its operational life. Advantages: Effective Seepage Control: Cutoff walls provide a highly effective means of blocking seepage paths and protecting levee foundations. Durability: Concrete and grout cutoff walls are durable and resistant to erosion and other forms of damage. Disadvantages: Cost: The construction of cutoff walls can be expensive due to the materials and techniques involved. Complexity: Installing cutoff walls can be complex, particularly in challenging soil conditions or where existing infrastructure must be worked around. 32 Republic of the Philippines NUEVA ECIJA UNIVERSITY OF SCIENCE AND TECHNOLOGY Cabanatuan City, Nueva Ecija, Philippines I. GREEN TECHNOLOGIES Green technology, also known as sustainable technology or environmental technology, refers to products, processes, and systems that aim to reduce or eliminate negative environmental impacts. It involves using renewable resources, minimizing waste, and promoting energy efficiency to create environmentally friendly and sustainable solutions. The primary goals of green technology are to conserve and promote the sustainable use of natural resources, reduce greenhouse gas emissions and air pollutants, enhance biodiversity by protecting ecosystem, and mitigate the effects of climate change, all while supporting economic growth and development. Key aspects of Green Technology: Energy Efficiency Renewable Energy Waste Management Water Conservation Sustainable Construction Pollution Reduction 1. Permeable Pavement Permeable pavements are designed to allow stormwater to filter pollutants from the water as it passes through layers of soil and aggregate, reduce flooding by decreasing runoff, and helping with groundwater recharge. These systems often use a base and subbase material that supports the weight of traffic while allowing water infiltration. Additionally, it reduces the need for stormwater drainage infrastructure. 33 Republic of the Philippines NUEVA ECIJA UNIVERSITY OF SCIENCE AND TECHNOLOGY Cabanatuan City, Nueva Ecija, Philippines There are several types of permeable pavements, such as: Porous Asphalt: Allows water to drain through pores in the surface. Pervious Concrete: Contains little or no sand, creating voids for water passage. Interlocking Concrete Pavers: Spaces between the pavers allow water infiltration. 2. Catch basin A catch basin is a crucial component in stormwater management systems, designed to capture and direct runoff water from streets, parking lots, and other surfaces into the drainage system. It helps prevent flooding by collecting excess water and debris, ensuring that the drainage system functions efficiently. 34 Republic of the Philippines NUEVA ECIJA UNIVERSITY OF SCIENCE AND TECHNOLOGY Cabanatuan City, Nueva Ecija, Philippines 3. Green Roofs Green roofs consist of vegetation planted over a waterproof membrane on top of a building. They can be extensive (shallow, with minimal maintenance plants like moss and sedum) or intensive (deeper soils, with a wider variety of plants, including shrubs and trees). Benefits of Green Roofs: Helps in stormwater management by retaining rainwater and slowing runoff. Provides insulation, reducing energy usage for heating and cooling. Mitigates the urban heat island effect. Improves air quality by absorbing pollutants and carbon dioxide. Extensive Green Roofs: Intensive Green Roof: 35 Republic of the Philippines NUEVA ECIJA UNIVERSITY OF SCIENCE AND TECHNOLOGY Cabanatuan City, Nueva Ecija, Philippines F. NONSTRUCTURAL FLOOD MITIGATION MEASURES Nonstructural flood mitigation measures refer to strategies and actions that reduce the risk of flood damage without constructing physical barriers or modifying the landscape. Instead of focusing on physical infrastructure, these measures work through policy, planning, and adaptive practices to prevent or minimize flood impacts. Nonstructural measures vary in cost and effectiveness and the physical and political effort required to implement them. Examples of Nonstructural Flood Mitigation Measures: 1. Flood Early Warning Systems (FEWS) The Philippine Atmospheric, Geophysical, and Astronomical Services Administration (PAGASA) operates a flood forecasting and warning system to alert the public of impending floods. These systems help communities prepare and evacuate in advance, reducing loss of life and damage to property. The Metro Manila Flood Management Project includes enhanced FEWS, using rainfall and river gauges to predict flood risks and disseminating timely warnings via text messages and local media. 2. Floodplain Zoning and Land Use Regulation Local governments in flood-prone areas implement zoning ordinances that limit development in high-risk floodplains. This measure prevents new developments in these vulnerable areas, thereby minimizing future exposure to flood risks. Marikina City, which frequently experiences flooding due to its proximity to the Marikina River, has implemented zoning policies to restrict residential and commercial 36 Republic of the Philippines NUEVA ECIJA UNIVERSITY OF SCIENCE AND TECHNOLOGY Cabanatuan City, Nueva Ecija, Philippines development near the riverbanks. The city also relocates informal settlers from these high-risk areas. 3. Community-Based Disaster Risk Reduction and Management (CBDRRM) Programs Local government units (LGUs) and NGOs have developed community-based programs that increase awareness and preparedness for flooding. These programs focus on training communities to respond effectively during floods and creating evacuation plans. The Philippine Disaster Resilience Foundation (PDRF) conducts disaster preparedness training and simulation exercises in flood-prone regions, including Cagayan de Oro, Metro Manila, and Leyte. 4. National Flood Insurance Program (NFIP) Although not as widely adopted as in other countries, insurance for properties located in flood-prone areas is promoted to financially protect citizens. The Government Service 37 Republic of the Philippines NUEVA ECIJA UNIVERSITY OF SCIENCE AND TECHNOLOGY Cabanatuan City, Nueva Ecija, Philippines Insurance System (GSIS) offers insurance to properties against natural disasters, including floods, helping citizens recover more quickly after flood events. GSIS’s natural calamity insurance coverage provides compensation to government employees and local government properties in flood-affected areas. 5. Rainwater Harvesting and Water Retention Projects Rainwater harvesting helps mitigate floods by capturing excess rainfall and storing it for future use. This approach reduces stormwater runoff and can be used for irrigation or domestic purposes in both urban and rural areas. The Department of Public Works and Highways (DPWH) has encouraged the use of rainwater catchment systems in flood-prone areas like Laguna and Metro Manila as a flood mitigation measure. 38 Republic of the Philippines NUEVA ECIJA UNIVERSITY OF SCIENCE AND TECHNOLOGY Cabanatuan City, Nueva Ecija, Philippines NONSTRUCTURAL FLOOD MITIGATION MEASURES 1. Structure Elevation Structure elevation is a flood mitigation technique where a building or structure is raised above the expected flood levels to prevent floodwaters from entering. This can involve elevating a home on stilts, columns, or raised platforms, ensuring the lowest floor is above the base flood elevation (BFE). Purpose: To reduce the risk of flood damage by physically elevating buildings above expected flood levels. To comply with local floodplain management regulations, especially in high-risk areas. Strengths: Effectively minimizes flood damage to the building's main structure. Long-term protection, reducing repair costs after floods. Weaknesses: Can be expensive, depending on the size and structure of the building. May not be suitable for all building types (e.g., large commercial buildings). 2. Natural Systems Natural systems refer to ecosystems like wetlands, forests, rivers, and mangroves that naturally help absorb, store, and manage water, reducing the impact of floods, erosion, and 39 Republic of the Philippines NUEVA ECIJA UNIVERSITY OF SCIENCE AND TECHNOLOGY Cabanatuan City, Nueva Ecija, Philippines other natural hazards. These systems act as buffers against floods by slowing water flow and storing excess water. Purpose: - To leverage natural ecosystems for flood mitigation and water management. - To provide long-term environmental sustainability while reducing flood risks. Strengths: - Environmentally sustainable and low-maintenance once established. - Offers additional benefits like habitat creation, water purification, and carbon sequestration. Weaknesses: - May take time to establish and restore natural systems. - Requires large areas of land to be effective, which may not be available in urban settings. Example: Restoring coastal mangroves to protect against storm surges in the Philippines. 3. Risk Mapping Risk mapping involves creating visual representations of areas susceptible to hazards like floods, earthquakes, or landslides. These maps identify zones with varying levels of risk, helping inform land-use planning, emergency response, and public awareness. 40 Republic of the Philippines NUEVA ECIJA UNIVERSITY OF SCIENCE AND TECHNOLOGY Cabanatuan City, Nueva Ecija, Philippines Purpose: - To identify and communicate the level of risk in different geographical areas. - To guide development, zoning, and land-use decisions to minimize exposure to hazards. Strengths: - Helps policymakers and the public understand risk and take preventive actions. - Essential for disaster preparedness and insurance purposes. Weaknesses: - Mapping requires continuous updating to reflect changing environmental conditions (e.g., climate change). - May lead to decreased property values in high-risk zones. Example: The Flood Hazard Mapping project by PAGASA in the Philippines. 4. Hazard Forecasting, Early Warning Systems, and Emergency Plans Hazard Forecasting: Predicting natural hazards like floods, typhoons, or earthquakes based on weather data, geological surveys, and modeling. 41 Republic of the Philippines NUEVA ECIJA UNIVERSITY OF SCIENCE AND TECHNOLOGY Cabanatuan City, Nueva Ecija, Philippines Early Warning Systems (EWS): Systems designed to provide timely information and alerts to the public and authorities about potential hazards to enable preparedness and action. Emergency Plans: Pre-planned actions and protocols set in place for individuals, organizations, and governments to respond effectively to emergencies, reducing casualties and damage. Purpose: - To provide timely alerts to prevent loss of life and property during natural disasters. - To ensure preparedness and a coordinated response in the event of emergencies. Strengths: - Saves lives and reduces economic damage by allowing timely evacuations and preparations. - Builds community resilience and preparedness for disasters. Weaknesses: - Requires reliable infrastructure, data collection, and communication networks. - Effectiveness depends on public trust and response to warnings. Examples: PAGASA's typhoon forecasting and flood warning systems in the Philippines. 42 Republic of the Philippines NUEVA ECIJA UNIVERSITY OF SCIENCE AND TECHNOLOGY Cabanatuan City, Nueva Ecija, Philippines 5. Dry and Wet Floodproofing Dry Floodproofing: Protecting a building from floodwaters by sealing walls, doors, and windows to prevent water from entering. This involves using waterproof coatings, barriers, and installing flood shields. Wet Floodproofing: Allowing water to enter and exit a building but designing it to minimize damage. This is done by using water-resistant materials and ensuring that critical utilities are elevated above flood levels. Purpose: - Dry Floodproofing: To prevent floodwaters from entering the building. - Wet Floodproofing: To reduce the damage by letting water pass through but minimizing its impact on the building's structure. Strengths: - Dry Floodproofing: Provides strong protection for non-residential buildings. - Wet Floodproofing: Cost-effective for buildings that cannot be elevated, especially in flood-prone areas. 43 Republic of the Philippines NUEVA ECIJA UNIVERSITY OF SCIENCE AND TECHNOLOGY Cabanatuan City, Nueva Ecija, Philippines Weaknesses: - Dry Floodproofing: Not suitable for areas with high flood depths, as walls may collapse under pressure. - Wet Floodproofing: Requires proper design to prevent long-term water damage and mold growth. 6. Land Use Planning and Zoning Land use planning is a nonstructural method that encourages the careful management of land and natural resources, directing investments to maximize community benefits from development (UNECE 2008). It involves a process led by public authorities to assess and determine various land use options, taking into account long-term economic, social, and environmental goals, as well as the impacts on different communities and stakeholders. This process results in the creation and communication of plans that outline the allowed or suitable uses of the land (UNISDR 2009). Benefits of Land Use Planning Different opportunities to manage flood risk, with the flexibility to address flood types, precipitation and runoff uncertainty, population growth, and land cover changes Coordination of flood risk in multiple sectors that involve land development (critical infrastructure and utilities, open space, and housing). Coordination of flood risk at multiple scales, from local plans for specific communities to multijurisdictional watershed planning A safe, productive, and livable urban environment at lower cost as compared to using structural systems 44 Republic of the Philippines NUEVA ECIJA UNIVERSITY OF SCIENCE AND TECHNOLOGY Cabanatuan City, Nueva Ecija, Philippines How can land use planning reduce flood risk? Flood risk can be reduced by not locating development (homes, business, infrastructure) in areas that are at high risk of flooding, for example floodplains. Parks as well as private gardens can be planned and designed to absorb and contain large amounts of water during and after heavy rainfall. Natural flood plains and wetlands will do the same. Strengths of Land Use Planning: - Keeps People Safe: Smart planning directs buildings away from flood zones, reducing potential damage. - Builds for the Future: Considering flood risks early on helps cities grow sustainably and stay resilient. - Saves Money: It's cheaper to plan ahead than to repair after a flood. - Protects Nature: Preserving natural floodplains helps absorb floodwaters, reducing impacts. - Supports Recovery: Placing key services in safer areas means communities can bounce back faster. Weaknesses of Land Use Planning: - Hard to Enforce: Effective planning needs strong rules and enforcement, which isn’t always easy. - Pressure to Build: Economic and political pressures can lead to risky development. - Slow to Adapt: Once plans are set, they can be hard to change, even if flood risks increase. - Could Deepen Inequality: Safer areas might become more expensive, impacting low-income communities. - Needs Good Data: Effective planning relies on accurate data and resources, which aren’t always available. Land use planning plays a crucial role in flood mitigation by guiding how land is developed and used to reduce the risk and impact of floods. Here are some key areas of application: 1. Zoning and Land Use Regulation Setting rules about where you can build helps keep buildings away from flood-prone areas, reducing damage and danger. 45 Republic of the Philippines NUEVA ECIJA UNIVERSITY OF SCIENCE AND TECHNOLOGY Cabanatuan City, Nueva Ecija, Philippines 2. Stormwater Management Designing cities with things like green roofs and permeable pavements helps manage rainwater and lessen flooding. 3. Floodplain Mapping and Risk Assessment Using flood maps to guide where and how to build, which helps in planning to avoid high-risk areas. 4. Community Planning and Public Education Getting people involved in planning and educating them about flood risks helps everyone be more prepared. 5. Climate Change Adaptation Planning for the future by considering how climate change might increase flood risks and adapting accordingly. Examples: Metro Manila Flood Management Master Plan This plan addresses flood risks in Metro Manila through a combination of land use planning, infrastructure improvements, and zoning regulations. It includes measures like relocating informal settlers from flood-prone areas and implementing better drainage systems. Cagayan de Oro City Land Use Plan Cagayan de Oro City has integrated flood risk management into its land use planning by designating flood-prone areas as non-buildable zones and implementing strict zoning regulations. This approach aims to prevent development in areas at high risk of flooding. 46 Republic of the Philippines NUEVA ECIJA UNIVERSITY OF SCIENCE AND TECHNOLOGY Cabanatuan City, Nueva Ecija, Philippines 7. Public Education and Awareness It has been noted that floods often cause panic and confusion due to a lack of flood defense education. People are unsure how to respond effectively to such natural events. Integrating flood defense strategies into the education curriculum as a mandatory subject—especially for those living in flood-prone areas—can address this issue. With proper training, individuals will be better equipped to handle flood situations themselves, reducing the potential for major damage. This approach not only minimizes flood-related harm but also saves public funds that would otherwise be spent on relief and rehabilitation efforts. Public education and awareness about floods are really important for keeping people safe, but they come with their own set of strengths and challenges. Strengths 1. Better Preparedness Helps people understand flood risks and what they can do to stay safe. Knowing how to read flood maps and where to go during an evacuation can make a big difference when a flood hits. 2. Encourages Safety Measures Motivates people to take steps to protect themselves and their homes. Awareness campaigns might inspire homeowners to elevate their property or set up emergency kits. 3. Improves Public Safety Provides clear instructions on what to do during a flood, which can prevent injuries and save lives. Training sessions on flood safety help people act quickly and calmly when a flood occurs. 47 Republic of the Philippines NUEVA ECIJA UNIVERSITY OF SCIENCE AND TECHNOLOGY Cabanatuan City, Nueva Ecija, Philippines Weaknesses 1. Limited Reach Not everyone might see or act on the information provided. For example, people without access to the internet might miss important updates about flood safety. 2. Understanding and Remembering Information Some people might not fully grasp or remember the flood safety tips they receive. Knowing where to evacuate is important, but if someone doesn’t practice it, they might not react quickly in an emergency. 3. Inconsistent Efforts The quality of flood education can vary, leading to uneven preparedness. Some areas might have great programs, while others have limited or less effective ones. Application of public education and awareness in flood mitigation 1. Flood Risk Education. It helps people understand their flood risks and what it means for their homes and communities. ○ Workshops and Seminars: Local groups and experts hold sessions to explain flood risks and how to stay safe. ○ Informational Materials: Flyers, brochures, and online resources give clear details on flood zones, evacuation routes, and safety tips. 2. Emergency Preparedness Training. It prepares individuals and families to handle floods effectively. ○ Training Sessions: Emergency services teach first aid, how to make family emergency plans, and how to prepare disaster kits. ○ Drills and Simulations: Communities practice evacuation and response to ensure everyone knows what to do when a flood occurs. 3. Community Engagement Programs. Encourages people to get involved in preventing and managing floods. ○ Volunteer Programs: Activities like river clean-ups and local flood watch groups help keep communities active in flood prevention. ○ Local Awareness Campaigns: Community-led efforts spread the word about flood risks and safety measures. 48 Republic of the Philippines NUEVA ECIJA UNIVERSITY OF SCIENCE AND TECHNOLOGY Cabanatuan City, Nueva Ecija, Philippines Examples In the Philippines, several efforts focus on educating the public and raising awareness about flood risks: Project NOAH: This initiative provides real-time weather updates and flood forecasts, along with training for local officials and communities on how to use this information effectively. Pagasa’s Flood Alerts: The weather agency offers timely flood warnings and educational resources through TV, radio, and online platforms, helping people stay informed about flood risks. NDRRMC Campaigns: The National Disaster Risk Reduction and Management Council runs nationwide campaigns and simulations to teach people how to prepare for and respond to floods. School Education: Schools incorporate flood safety into their curriculums, teaching students about flood risks and how to stay safe through lessons and drills. 8. Wetland Restoration Wetland restoration is a vital approach for managing floods due to its natural water-handling abilities and the ecological benefits it brings. Wetlands function like nature’s sponges, absorbing and holding water until it can slowly seep into the ground. This is especially important in urban areas, where much of the runoff comes from past groundwater use. Any water that doesn’t get absorbed is gradually released into nearby streams by the wetland, helping to prevent floods during heavy rains. The plants in wetlands also play a role in slowing down the flow of water across the land. By combining these functions, wetlands offer significant water storage, reduce flood heights, and minimize erosion. In cities, wetlands can also help filter out harmful pollutants. Overall, wetlands help balance out the negative impacts that urban development can have on watersheds. 49 Republic of the Philippines NUEVA ECIJA UNIVERSITY OF SCIENCE AND TECHNOLOGY Cabanatuan City, Nueva Ecija, Philippines Strengths 1. Natural Flood Control. Wetlands act like sponges, soaking up excess water during heavy rains. This helps reduce the amount of water flowing into rivers and streams, easing flood risks. 2. Cleaner Water. Wetlands filter out pollutants from water before it reaches larger bodies of water, improving overall water quality and helping to prevent flood-related contamination. Restored wetlands can trap nutrients and pollutants from agricultural runoff, keeping waterways cleaner and healthier. 3. Biodiversity Boost. Wetlands support a wide range of plants and animals, which helps keep ecosystems healthy and resilient. This added biodiversity can enhance the wetlands' ability to manage floods. 4. Cost-Effective Long-Term. After they're established, wetlands require relatively little maintenance compared to man-made flood control structures, making them a sustainable option for flood management. Weaknesses 1. Takes Time to Develop. Wetlands don’t offer immediate flood relief. It can take years for them to fully establish their flood management functions. Newly restored wetlands may not provide the same level of flood protection right away as more established systems. 2. Land Use Conflicts. Restoring wetlands often requires repurposing land that could otherwise be used for farming or development, which can lead to disagreements with landowners and developers. 3. Need for Ongoing Care. Although wetlands are generally low-maintenance, they still need regular care to keep them healthy and effective. Issues like invasive species or pollution can require attention. 4. Not a Complete Solution. Wetlands alone might not be enough to handle very severe floods, especially in highly developed areas or places with significant flood risks. 50 Republic of the Philippines NUEVA ECIJA UNIVERSITY OF SCIENCE AND TECHNOLOGY Cabanatuan City, Nueva Ecija, Philippines How wetland restoration helps with flooding? 1. Floodplain Reconnection. By reconnecting wetlands with floodplains, we allow these areas to naturally absorb excess water from floods. This reduces the intensity of floods in nearby rivers and streams. 2. Creating and Enhancing Wetlands. Building new wetlands or improving existing ones increases their ability to hold and slowly release water, which helps manage floodwaters. 3. Coastal Wetland Restoration. Restoring coastal wetlands like mangroves and salt marshes provides a natural barrier against storm surges and tidal floods, protecting coastal communities. 4. Urban Wetland Integration. Incorporating wetlands into urban areas helps manage stormwater runoff and reduces the risk of flooding in cities. Example: The Agusan Marsh Wildlife Sanctuary, nestled in Agusan del Sur, is like a giant natural shield for the region. This vast wetland was given a new lease on life to help handle floodwaters from the Agusan River Basin. When heavy rains hit, the marsh soaks up excess water, acting like a giant sponge. This means that surrounding communities experience less severe flooding, keeping homes and lives safer. The restored marsh also works as a natural water filter, trapping pollutants and improving the quality of water flowing into local rivers. Due to the marsh's restoration, the area has seen fewer severe floods and cleaner water. This has not only helped the local environment thrive but has also made life better for people living nearby. 51 Republic of the Philippines NUEVA ECIJA UNIVERSITY OF SCIENCE AND TECHNOLOGY Cabanatuan City, Nueva Ecija, Philippines 9. Floodplain Management Floodplain management is about creating and executing strategies to manage floodplains in a way that reduces flood damage. It combines thoughtful land use planning, regulatory measures, and flood control infrastructure to oversee the areas surrounding rivers and streams that are susceptible to flooding. Flood-plain zoning is a concept central to flood plain management. Flood-plain zoning measures aim at demarcating zones or areas likely to be affected by floods of different magnitudes or frequencies and probability levels and specify the types of permissible developments in these zones, so that whenever floods actually occur, the damage can be minimized, if not avoided. Flood plain zoning requires careful delineation of flood risk zones. Strengths 1. Reduces Flood Risk: By carefully planning how land is used and built upon in flood-prone areas, floodplain management lowers the risk of flood damage. For example, zoning laws can keep new construction out of high-risk areas, helping to protect homes and businesses. 2. Safeguards Lives and Property: It ensures that buildings are constructed to withstand floods and that flood-prone areas are kept clear of new developments. This approach can save lives and prevent property damage. For instance, requiring homes to be built on stilts can prevent them from being flooded. 3. Improves Water Quality: By restoring natural features like wetlands, floodplain management enhances the natural filtering of water. This helps to keep rivers and lakes cleaner by removing pollutants before they spread. Weaknesses 1. High Costs: Implementing floodplain management measures can be expensive. Building and maintaining flood defenses like levees and floodwalls requires a lot of money. 52 Republic of the Philippines NUEVA ECIJA UNIVERSITY OF SCIENCE AND TECHNOLOGY Cabanatuan City, Nueva Ecija, Philippines 2. Ongoing Maintenance: Flood control infrastructure needs regular upkeep to stay effective. Levees and other structures must be inspected and repaired to prevent failures. 3. Limitations in Extreme Floods: Even with the best planning and infrastructure, extremely severe floods might still cause significant damage. Protective measures can only do so much against the most extreme weather events. Applications of Flood Plain Management 1. Smart Land Use Planning: Carefully designing how land in flood-prone areas is used to minimize flood risks. 2. Building Codes and Regulations: Setting standards for how buildings should be constructed in flood-prone areas to withstand flood damage. 3. Flood Control Infrastructure: Building physical structures to manage floodwaters and protect communities. 4. Restoring Natural Areas: Reviving natural floodplain features, like wetlands and forests, to help manage floodwaters naturally. Pasig River Rehabilitation Program This program is a major initiative focused on restoring and managing the Pasig River, which flows through Metro Manila. The project aims to improve flood management and environmental conditions along the river. The program includes dredging the river to deepen it, restoring riverbanks, and upgrading drainage systems. There’s also a focus on managing the floodplain to prevent illegal settlements and reduce flood risks. By revitalizing the Pasig River and its surrounding areas, the program helps reduce flooding, improves water quality, and enhances the urban environment. It’s a critical effort for Metro Manila, where flooding is a significant challenge, and the river’s restoration benefits both local ecosystems and communities. 53 Republic of the Philippines NUEVA ECIJA UNIVERSITY OF SCIENCE AND TECHNOLOGY Cabanatuan City, Nueva Ecija, Philippines G. COMBINING STRUCTURAL AND NON-STRUCTURAL MEASURES Combining structural and non-structural flood mitigation measures is like creating a balanced safety net for communities. Imagine a town where a sturdy levee guards against a nearby river’s floodwaters. The town planners ensure that new homes are built on higher ground, away from the most flood-prone areas. Meanwhile, residents receive regular updates about flood risks and participate in community drills, so they know exactly how to respond if the water levels rise. This combination of physical protection and informed action makes the community much more resilient to floods. By working together, these structural and non-structural measures create a layered approach to flood mitigation, reducing risks and helping communities adapt to changing environmental conditions. They make sure that, even if one measure fails or the flood is worse than expected, there are other safeguards in place to protect lives and livelihoods. This combined approach is effective because it offers layers of protection. While levees might hold back rising waters, things like zoning laws ensure that new homes aren’t built in areas likely to flood. By educating communities, people know how to respond when floods happen, adding another layer of safety. Pros Multiple Layers of Safety: If one measure falters, others are in place to keep the community safe. Flexible Adaptation: Non-structural strategies are adaptable, allowing quick changes in response to new risks without needing major construction projects. Nature-Friendly: By focusing on non-structural measures, communities can protect natural areas that help manage floodwaters and support biodiversity. Empowered Communities: Engaging people in flood preparedness means they’re more informed, proactive, and involved in protecting their own neighborhoods. Cons High Costs: Building and maintaining large structures like dams can be expensive and require ongoing investment. False Confidence: Relying too much on physical barriers might lead people to underestimate the importance of preparedness and planning. Environmental Disruption: Large-scale construction projects can disrupt ecosystems, affecting wildlife and natural water flows. 54 Republic of the Philippines NUEVA ECIJA UNIVERSITY OF SCIENCE AND TECHNOLOGY Cabanatuan City, Nueva Ecija, Philippines Complex Coordination: Managing this combined approach involves many different groups working together, which can be challenging to organize effectively. H. CONSTRUCTION STANDARDS AND BUILDING CODES In the Philippines, construction standards and building codes are essential tools for building safer communities, especially in areas at risk of flooding. These rules ensure that when we build homes, schools, and other infrastructure, they’re designed to withstand the challenges of floods, protecting both lives and properties. 1. National Building Code of the Philippines (NBCP) The NBCP, also known as Presidential Decree No. 1096, serves as the guiding framework for building construction across the country. It ensures that structures are not only functional but also resilient against natural disasters, including floods. For those living in flood-prone areas, the NBCP requires that buildings be elevated above known flood levels. It’s like raising homes on higher ground to keep them safe when floodwaters rise. This code also ensures that proper drainage systems are in place, and that materials used in construction can resist water damage. 2. Water Code of the Philippines Republic Act No. 9275, the Philippine Clean Water Act of 2004, along with Presidential Decree No. 1067 (The Water Code), regulates the management of water resources, including how we handle floodwaters. These laws are like a blueprint for managing water bodies and floodplains. They highlight the importance of building flood control systems—like drainage channels and flood barriers—to protect communities from the dangers of flooding. 3. Revised Implementing Rules and Regulations (IRR) of the National Building Code The IRR offers detailed instructions for implementing the NBCP, providing specific guidelines for building in areas prone to flooding. Imagine living in a flood zone—under these regulations, your house would need to be designed to minimize potential flood damage. This might involve choosing the right site, raising your home above flood levels, and using materials that can handle being wet without falling apart. 55 Republic of the Philippines NUEVA ECIJA UNIVERSITY OF SCIENCE AND TECHNOLOGY Cabanatuan City, Nueva Ecija, Philippines 4. Local Government Ordinances Local governments in the Philippines can create additional rules to complement national laws, especially in flood-prone areas. These local ordinances allow communities to take extra precautions, like requiring even higher building elevations or more robust drainage systems in areas that frequently flood. It’s a way for communities to tailor solutions to their specific needs. 5. Zoning Ordinances Zoning ordinances help manage how land is used, ensuring that development doesn’t increase flood risks. These rules might restrict construction in vulnerable areas like floodplains or wetlands. They can also require developers to incorporate features like retention ponds or advanced drainage systems to manage floodwaters effectively. 6. Disaster Risk Reduction and Management (DRRM) Act Republic Act No. 10121, known as the Philippine Disaster Risk Reduction and Management Act of 2010, focuses on making communities more resilient to disasters. This law encourages the integration of disaster preparedness into every aspect of community planning, including building codes. It’s about creating neighborhoods that can not only survive floods but recover quickly from them. 56 Republic of the Philippines NUEVA ECIJA UNIVERSITY OF SCIENCE AND TECHNOLOGY Cabanatuan City, Nueva Ecija, Philippines REFERENCES: Brunner, G. W. (2021). Hydraulic considerations for levees and floodwalls. U.S. Army Corps of Engineers. Retrieved from https://www.hec.usace.army.mil/ U.S. Army Corps of Engineers. (2019). Design and construction of levees. Engineer Manual 1110-2-1913. Retrieved from https://www.publications.usace.army.mil/ Godschalk, D. R., & Beatley, T. (2019). Floodplain management: Principles and current practices. Springer. Melville, B. W., & Coleman, S. E. (2020). Bridge scour. Water Resources Publications. Mays, L. W. (2010). Water resources engineering. John Wiley & Sons. Peters, J., & Kershner, B. (2021). Seepage berm design considerations for flood control levees. Journal of Hydraulic Engineering, 147(5), 1-12. https://doi.org/10.1061/(ASCE)HY.1943-7900.0001786 Resio, D. T., & Westerink, J. J. (2015). Modeling hurricane storm surges for flood risk analysis. Coastal Engineering, 93, 1-11. https://doi.org/10.1016/j.coastaleng.2014.07.004 National Research Council. (2012). Dam and levee safety and community resilience: A vision \ for future practice. National Academies Press. https://doi.org/10.17226/13393 World Bank. (2019). Flood risk management: Leveraging resources to enhance resilience. World Bank Publications. Retrieved from https://www.worldbank.org/en/topic/floodriskmanagement Philippines Department of Public Works and Highways. (2017). National flood control program. Retrieved from https://www.dpwh.gov.ph/dpwh/references/flood_control_program Federal Emergency Management Agency. (n.d.). Elevating your house. FEMA. https://www.fema.gov/ Wetlands International. (n.d.). Ecosystem-based flood management. https://www.wetlands.org/ Ramsar Convention on Wetlands. (n.d.). Wetlands and disaster risk reduction. https://www.ramsar.org/ Philippine Atmospheric, Geophysical and Astronomical Services Administration. (n.d.). \ Hazard mapping and assessment for effective community-based disaster risk 57 Republic of the Philippines NUEVA ECIJA UNIVERSITY OF SCIENCE AND TECHNOLOGY Cabanatuan City, Nueva Ecija, Philippines management (READY). https://www.pagasa.dost.gov.ph/ United Nations Office for Disaster Risk Reduction. (n.d.). Early warning systems. UNDRR. https://www.undrr.org/ Philippine Atmospheric, Geophysical and Astronomical Services Administration. (n.d.). Flood early warning systems. PAGASA. https://www.pagasa.dost.gov.ph/ United Nations Office for Disaster Risk Reduction. (n.d.). Early warning systems. UNDRR. https://www.undrr.org/ Cagayan de Oro City Government. “Cagayan de Oro City Comprehensive Land Use Plan 2013-2022.” Retrieved from Cagayan de Oro City Website. White, G. F., & Haas, J. E. (1975). “Assessment of Research on Floodplain Management.” University of Chicago Press Project NOAH: Department of Science and Technology (DOST). (n.d.). Project NOAH: Nationwide Operational Assessment of Hazards. Retrieved from DOST Website. Pagasa’s Flood Early Warning System: Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA). (n.d.). Flood Early Warning System. Retrieved from PAGASA Website. National Disaster Risk Reduction and Management Council (NDRRMC). (n.d.). National Disaster Resilience Month. Retrieved from NDRRMC Website. Local Government Initiatives: City Government of Marikina. (n.d.). Flood Management Programs. Retrieved from Marikina City Government Website. School-Based Programs: Department of Education (DepEd). (n.d.). Disaster Risk Reduction and Management (DRRM) Curriculum. Retrieved from DepEd Website. Community-Based Disaster Risk Reduction and Management (CBDRRM): Asian Development Bank (ADB). (2010). Community-Based Disaster Risk Management in the Philippines. Retrieved from ADB Website. Richardson, C. J. (1994). Ecosystem services of wetlands. In G. M. Carter (Ed.), Wetlands in a Changing Environment (pp. 65-80). Springer. Burby, R. J., & May, P. J. (1997). Intergovernmental environmental management: The role of local governments in environmental policy. Environment and Planning C: Government and Policy, 15(1), 47-64. Department of Public Works and Highways (DPWH). (2021). Pasig River Rehabilitation Program. Retrieved from DPWH website. 58 Republic of the Philippines NUEVA ECIJA UNIVERSITY OF SCIENCE AND TECHNOLOGY Cabanatuan City, Nueva Ecija, Philippines Department of Public Works and Highways (DPWH). National Building Code of the Philippines (PD 1096). Republic Act No. 9275. Philippine Clean Water Act of 2004. Republic Act No. 10121. Philippine Disaster Risk Reduction and Management Act of 2010. Presidential Decree No. 1067. The Water Code of the Philippines. Bardhan, M. (n.d.). Non-Structural Measures for Flood Mitigation and Sustainable Development of a Country. International Conference on Hydropower and Dam Development for Water and Energy Security – Under Changing Climate. Flood Resilience Portal. (2021, May 25). How can land use planning reduce flood risk? - Flood Resilience Portal. https://floodresilience.net/how-can-land-use-planning-reduce-flood-risk/ 59

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