Flood Control Strategies PDF

FLOOD CONTROL STRATEGIES (STRUCTURAL AND NON- STRUCTURAL MITIGATION MEASURES ALLEVIATION OF FLOODING  LEARNING POINTS Discuss Explain how each Describe structural of these what m...

FLOOD CONTROL STRATEGIES (STRUCTURAL AND NON- STRUCTURAL MITIGATION MEASURES ALLEVIATION OF FLOODING  LEARNING POINTS Discuss Explain how each Describe structural of these what measures most measures relates flooding is. often used in to levees flood control WHAT IS FLOODING? Flooding is an overflow of a body of water onto the surrounding land.  CAUSES OF FLOODING DURATION HEAVY RAIN GEOLOGY VEGETATION Impermeable Increased Heavy rain Deforestation rocks rainfall reduces time increases underground duration for the rain flooding as increase saturates to infiltrate less water is surface run- the ground. the ground. absorbed. off. STRUCTURAL MITIGATION MEASURES Involve or dictate a necessity for some kind of construction, engineering, or other mechanical changes or improvements aimed at reducing hazard risk likelihood or consequence. LEVEES, FLOODWALLS, SEAWALLS, AND OTHER APPURTENANT STRUCTURES These structures are designed to prevent floodwaters and storm surges from reaching areas that are at risk.  EMBANKMENTS PROS CONS River banks are raised to hold more water. They are cheap It could flood to construct and downstream as they help to water flow contain the flood increases and they within the river. may look unnatural.  LEVEE VS. DIKE LEVEE DIKE Levees protect land Dikes protect land that that is normally dry would naturally be but that may be underwater most of the flooded when rain or time. Levees and dikes melting snow raises look alike, and the water level in a sometimes the terms body of water, such levee and dike are used interchangeably. as a river.  DAMS Barriers that impound PROS CONS hydrologic flows, dams retain floodwaters before they reach areas at risk. They can be used to produce They are electricity and expensive and they create a can be an eye reservoir which sore. They could attracts tourists also flood local and provides habitats. water to locals.  TYPES OF DAM EMBANKMENT BUTTRESS DAM DIVERSION DAM GRAVITY DAM DAM Any dam A dam A dam built to A dam constructed of consisting of a divert water from constructed of excavated natural watertight part a waterway or concrete and/or materials or of supported at stream into a masonry, which industrial waste intervals on the different relies on its materials. downstream watercourse. weight and side by a series internal strength of buttresses. for stability.  TYPES OF DAM EMBANKMENT BUTTRESS DAM DIVERSION DAM GRAVITY DAM DAM  FLOODWAYS, SPILLWAYS, AND CHANNELS PROS CONS Floodways, spillways, and channels are constructed to carry floodwaters around a It can reduce During high community or region where the capacity of flood risks flood levels it is a river to pass a large volume of floodwaters not possible to particularly in past a critical location is limited. urban areas. pass through them  STRUCTURAL MITIGATION THROUGH IMPROVED LEVEE DESIGN OR MODIFICATION The most serious challenges result from wave action against a levee face, the erosion of the land side of a levee as the levee is overtopped or subject to waves breaking over its top, and seepage under the levee that destroys the levee from within. CONTROLLED OVERTOPPING AND BREACHING OF LEVEES This can be done by using different levee heights, known as superiority, or notches or openings in a desired location.  The advantages of controlled overtopping in a designated area are (1) reducing the impact of overtopping failure in the selected area and in other parts of the levee system, (2) reducing the likelihood of overtopping in less desirable areas (i.e., areas with more development), and (3) reducing levee maintenance and repair costs after the flood event. FIGURE 6-3 A gated overflow spillway that would control flows into a desired area.  LEVEE ARMORING Armoring a levee involves making a levee less susceptible to erosion induced by floodwaters and overtopping. It involves the use of a variety of materials, from concrete to vegetation. Three key factors in determining levee survival in a significant flood event and overtopping are depth and duration of flow, flow velocity (a function of slope inclination, height of the drop, and flow friction), and the erosive resistance of the vegetation mat and underlying soils LEVEE ARMORING FIGURE 6-4 Example of an armored levee in Japan.  STRUCTURE ELEVATION By rising a structure above the expected flood level , flood damages can be prevented  BASE FLOOD ELEVATION (BFE) level that surface water will likely reach a base flood STRUCTURE ELEVATION NON-STRUCTURAL MITIGATION MEASURES Measures not involving physical construction which use knowledge, practice or agreement to reduce disaster risks and impacts NONSTRUCTURAL MITIGATION MEASURES NATURAL SYSTEM RISK MAPPING HAZARD FORECASTING DRY AND WET FLOOD PROOFING LAND USE PLANNING AND ZONING NATURAL SYSTEMS WETLANDS LAND IN PERIODIC CULTIVATION COASTAL SAND DUNES AFFORESTATION WETLANDS SPONGE FILTER PERMEABLE AGUSAN MARSH WILDLIFE SANCTUARY LAND IN PERIODIC CULTIVATION AGRICULTURAL HORTICULTURAL AGRICULTURAL LAND HORTICULTURAL LAND COASTAL SAND DUNE SLOW DOWN COASTAL EROSION PROTECT STRUCTURES IMPACT OF RISING STORM SURGE LA PAZ SAND DUNE ILOCOS NORTE AFFORESTATION PROS CONS There are benefits It could cause a for forestry reduction of Trees are planted in the river companies and farmland, as land is valley to reduce floods. new habitats for used to plant wildlife. trees. EXAMPLE OF AFFORESTATION IN PH NATIONAL GREENING PROGRAM HAZARD FORECASTING, EARLY WARNING SYSTEMS AND EMERGENCY PLANS  PROVIDE ADVANCE INFORMATION MUST BE RELIABLE REDUCE OR ELIMINATE CASUALTIES AND PROPERTY LOSSES  WARNING PROS CONS SYSTEMS Some people may It allows locals to not be able to prepare Newspapers, radios and social access the properties for media warn people of potential warning and it potential floods, floods. doesn't stop the so possessions flood from may be saved. happening.  DRY AND WET FLOOD PROOFING ADJUSTMENTS AND/OR ADDITIONS OF FEATURES TO BUILDINGS THAT ELIMINATE OR REDUCE THE POTENTIAL FOR FLOOD DAMAGE.  DRY FLOODPROOFING IS ANY MEASURE TO MAKE A STRUCTURE WATERTIGHT BELOW THE LEVEL THAT NEEDS FLOOD PROTECTION TO PREVENT FLOODWATERS FROM ENTERING. EXAMPLES OF DRY FLOODPROOFING APPLYING A WATERPROOF COATING OR MEMBRANE TO THE EXTERIOR WALLS OF THE BUILDING INSTALLING WATERTIGHT SHIELDS OVER DOORS, WINDOWS AND OTHER OPENINGS; ANCHORING THE BUILDING AS NECESSARY SO THAT IT CAN RESIST FLOATATION EXAMPLES OF DRY FLOODPROOFING INSTALLING BACKFLOW VALVES IN SANITARY AND STORM SEWER LINES; RAISING UTILITY SYSTEM COMPONENTS, MACHINERY AND OTHER PIECES OF EQUIPMENT ABOVE THE FLOOD LEVEL; ANCHORING FUEL TANKS AND OTHER STORAGE TANKS TO PREVENT FLOTATION EXAMPLES OF DRY FLOODPROOFING INSTALLING A SUMP PUMP AND FOUNDATION DRAIN SYSTEM; STRENGTHENING WALLS SO THAT THEY CAN WITHSTAND THE PRESSURES OF FLOODWATERS AND THE IMPACTS OF FLOOD BORNE DEBRIS;  WET FLOODPROOFING MAKES UNINHABITED PORTIONS OF A STRUCTURE RESISTANT TO FLOODS BY ALLOWING WATER TO ENTER AND FLOW THROUGH THE STRUCTURE DURING A FLOOD EXAMPLES OF WET FLOODPROOFING INSTALLATION OF VENTS TO ALLOW WATER TO MOVE THROUGH CRAWL SPACES UNDER HOMES (AVOIDING DIFFERENT WATER LEVELS OUTSIDE AND UNDER A HOME) EXAMPLES OF WET FLOODPROOFING FLOODPROOFING CAN ALSO INCLUDE PERMANENT OR TEMPORARY INSTALLATION OF BARRIERS SUCH AS MODULAR DAMS AND SMALL LEVEES DESIGNED TO KEEP FLOODWATERS AWAY FROM ONE OR MORE STRUCTURES FOR LIMITED PERIODS OF TIME. LAND-USE PLANNING AND ZONING -Jesusa Sta. Cruz  LAND USE PLANNING IS THE PROCESS OF ALLOCATING LAND FOR DIFFERENT PURPOSES, SUCH AS RESIDENTIAL, COMMERCIAL, INDUSTRIAL, AGRICULTURAL, RECREATIONAL, OR ENVIRONMENTAL. ZONING IS THE REGULATION OF THE USE, DENSITY, HEIGHT, AND DESIGN OF BUILDINGS AND STRUCTURES ON A GIVEN PARCEL OF LAND.  LAND USE PLANNING IS THE PROCESS OF ALLOCATING LAND FOR DIFFERENT PURPOSES, SUCH AS RESIDENTIAL, COMMERCIAL, INDUSTRIAL, AGRICULTURAL, RECREATIONAL, OR ENVIRONMENTAL. ZONING IS THE REGULATION OF THE USE, DENSITY, HEIGHT, AND DESIGN OF BUILDINGS AND STRUCTURES ON A GIVEN PARCEL OF LAND. THIS PROCESS IS AN ESSENTIAL COMPONENT OF ANY DEVELOPMENT PLAN, IT CAN HELP PREVENT LAND-USE CONFLICTS AND EVEN REDUCE EXPOSURE TO POLLUTANTS. NFIP (NATIONAL FLOOD INSURANCE PROGRAM) SFHA (SPECIAL FLOOD HAZARD AREA) BFE (BASE FLOOD ELEVATION)  LAND-USE PLANNING AND ZONING REGULATION PROMOTING SMART GROWTH PRESERVING NATURAL RESOURCES FOSTERING ECONOMIC DEVELOPMENT ENHANCING QUALITY OF LIFE MANAGING GROWTH AND REDUCING CONFLICTS RISK MAPPING A DATA VISUALIZATION TOOL FOR COMMUNICATING SPECIFIC RISK OF AN ORGANIZATION FACES  FEMA FEDERAL EMERGENCY MANAGEMENT AGENCY DELIVER QUALITY DATA THAT INCREASES PUBLIC AWARENESS AND LEADS TO ACTION THAT REDUCES RISK TO LIFE AND PROPERTY DISASTER RESPONSE AND CRISIS MANAGEMENT TASK FORCE (DRCMTF) GROUP 1 The End of the Presentation