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types of flood & flood mitigation/management techniques - damages

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Flood Management
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types of flood & flood mitigation/management techniques - damages

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this presentation gives a brief about what are the different types of floods depending upon area & its cause.It is further aided with mitigation or management techniques to be implemented & types of damages.

this presentation gives a brief about what are the different types of floods depending upon area & its cause.It is further aided with mitigation or management techniques to be implemented & types of damages.

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types of flood & flood mitigation/management techniques - damages

  1. 1. Semester : BE - 5th Civil-A Subject : Hydrology & Water Resources Engineering Code : 2150602 Presentation On : Flood Management Prepared by : Eddy Ankit Gangani eddygangani@gmail.com
  2. 2.  What is Flood ?  What is Flood Management ?  Types of flood  Causes Of Flood
  3. 3.  Flood : A flood is an excess of water (or mud) on land that's normally dry and is a SITUATION wherein the inundation is caused by high flow, or overflow of water in an established watercourse, such as a river, stream, or drainage ditch; or ponding of water at or near the point where the rain fell. This is a unpredictable - duration type -natural and inevitable event.
  4. 4.  According to Duration : Slow-Onset Flooding Rapid-Onset Flooding Flash Flooding  According to Location : Coastal Flooding Storm surge Arroyos/Mud Flooding River Flooding Urban Flooding
  5. 5. 1. Riverine Floods: The majority of floods recorded globally are due to rivers overflowing as a result of long-lasting precipitation in the river basin. Melting snow and ice can also contribute to flooding. 2. Flash Floods : Flash floods generally occur due to local high-intensity precipitation in hilly or mountainous areas. The short warning time makes them difficult to predict. Discharges during flash floods are often much higher than normal flows in water courses. Flash floods are particularly dangerous on steep slopes. 3. Coastal Floods : Areas along the coast may be flooded due to tsunamis, hurricanes or/and unusually high tides. Also long-term phenomena like subsidence and sea-level rise can lead to the gradual encroachment of the sea. 4. Urban flooding : The urban area is paved with roads etc and the discharge of heavy rain can’t absorbed into the ground due to drainage constraints leads to flooding of streets, underpasses, low lying areas and storm drains 5. Stagnant and Urban Floods: Extreme rainfall in towns and cities combined with blocked drains can cause severe flooding. This often occurs in urban areas, where a large percentage of the surface is impermeable. 6. Lake and Canal Floods : High levels of precipitation or long-lasting inflows from streams can cause a substantial rise in water levels of lakes and canals that lack sufficient drainage capacity. Also, long periods of drought can cause man-made (peat) embankments to become unstable and fail – resulting in flooding.
  6. 6.  Uncontrolled unplanned urbanization - Unauthorized colonies , Poor Water and Sewerage Management  Deforestation + Population pressure  Lack of Flood Control Measures  Lack of attention to the nature of hydrological system  Slope Failures  Type of River  Intensity of Rainfall  Topography  Sedimentation of River/Reservoir  Obstructions in River flow  Contraction in River  Seismic effects
  7. 7. Mitigation Measures Mitigation Measures Flood plain zoning Flood forecasting Flood proofing Mathematical modeling Response planning Modifying loss burden Reservoirs-Flood gates Levees Flood wall Floodways Flood bypass Watershed Cut-off Rain Water Harvesting Channel improvement Drainage improvement Watershed management
  8. 8.  Reservoirs & Flood gates - Reservoirs can moderate the intensity and timing of the incoming flood. Floodgates are used to control the flow of water and can be a part of flood prevention. Floodgates are often incorporated into reservoir, river, stream, levee, or storm surge systems. Water flow can be either partially restricted or completely stopped, depending on the water level and desired effect. Expensive & potential error .
  9. 9.  Levees - A levee is a barrier built to keep a river, or other waterway away from people or sensitive habitats. Important considerations  First, it is important not to remove too much floodplain storage. Excess removal could restrict flood waters and slow drainage upstream. Second, levees are designed to protect an area from a certain flood level and storm intensity. If these levels are exceeded, a levee may be overtopped or may fail completely. Third, in order for a levee to continue functioning properly and provide security for those behind it, a levee should be regularly inspected and maintained.
  10. 10.  Floodwall - When construction space is low then a flood wall is implemented to protect low lying area. Does not reduce the flood flow but reduce spilling Acts as a retaining wall Section : Rectangular trapezoidal Sheet piling
  11. 11. Mitigation Measures • Cut-off - To have high velocity of water flow along a straight path To avoid ox bow lake Does not reduce the flood flow but reduce spilling
  12. 12. Mitigation Measures • Watershed Management - Long term effect Examples ; Afforestation Contour farming Check dams Gullying Bank protection Diversion drains
  13. 13. Mitigation Measures • Flood ways - Low lying are(depressions ) along the river course is known as floodways. Connected to natural channel or artificial channel Temporary storage Can be used for agriculture other than flood. Do not reduce the flood flow but reduce spilling
  14. 14. Mitigation Measures • Flood plain zoning-  Oftentimes floodplain management is not contained in a single comprehensive document, but instead is incorporated into other rules, guidelines, or regulations, including: • Floodplain Management Ordinance • Encourage appropriate development • Community Master Planning • Flood Hazard Zoning • Open Space Preservation Ordinance • Education and Outreach • Emergency Management Program • Mapping Program or GIS
  15. 15. Mitigation Measures • Flood forecasting -  For emergency evacuation  Flood forecasting through range of hydrodynamic/ snowmelt / flood routing models.  Flood warnings  CWC National Flood Forecasting Network
  16. 16. Mitigation Measures • Flood proofing -  Combination of structural change & emergency action.  Water proofing materials on windows  Water tight closure on doors  Example : use of flood wall or levees on periphery of building
  17. 17. Indirect Damage Direct Damage Flood Damage Analysis • clean-up costs • disruption to transport services ( disbility to provide community services) • disruption to utilities • disruption to public & emergency services • economic impacts of health issues • damage to building • external damage (pools, gardens, fences, shed contents) • motor vehicles • infrastructure (roads, bridges and other services) • clean-up costs for individual home owners • loss of stock • cost of re-instatement or rebuilding of houses and buildings. Tangible Damage
  18. 18. Non-monetary losses - variability -Loss of life & cattle -- Loss of health -Loss caused by social distress -Loss due to hindrance in development work -Physical ailments Flood Damage Analysis Intangible Damage
  19. 19.  Where applicable, the best practices described in here should be taken into ac-count, in particular on:  Integrated river basin approach  Public awareness, public participation and insurance  Research, education and exchange of knowledge  Retention of water and non-structural measures  Land use, zoning and risk assessment  Structural measures and their impact  Flood emergency  Prevention of pollution

Editor's Notes

  • FLMNTSRETAGE
  • fldmgmthandbook
    Reservoirs can moderate the intensity and timing of the incoming flood. They store the water during periods of high discharges in the river and release it after the critical high flow condition is over, so as to be ready to receive the next wave. Their effectiveness in moderating floods would depend on the reservoir capacity available at that time for absorbing the flood runoff and their proximity to the likely damage centre. They are operated with a carefully planned regulation schedule which takes into account both the safety of the dam and related structures and the safe carrying capacity of the lower reaches of the river in their present condition.
     
    Reservoirs are more effective for flood management if, apart from the incidental moderation available for any type of storage on a river, specific flood space is earmarked, as in the case of DVC dams across the Damodar and its tributaries. The operation schedule or rule curve being followed should be reviewed and a suitable operation schedule/rule curve prescribed for the monsoon filling to ensure space for flood moderation but which can be filled for conservation at a later stage when high flows end.
     
    In order to improve the efficiency of the reservoirs and improve the operation schedules for providing either incidental or specific flood moderation effects, arrangement for inflow forecasts should be made. 10.1.2 Detention Basins Detention basins are usually formed by utilizing natural depressions/ swamps and lakes by improving their capacity by constructing encircling embankments and providing suitable devices for regulating the release of stored waters. Since, the land under the marshes or low depression may hardly require much compensation and rehabilitation measures, this method are relatively in expensive. The Ghaggar detention basin in Rajasthan is a good example. Depressions available upstream of Srinagar City, on the left bank of river Jhelum, the Mokama Tal area in Bihar and Ottu, Bhindawas, Kotla lakes in Haryana and various beels/haors of Barak basin are some examples of a few natural basins.
     
  • fldmgmthandbook
    Reservoirs can moderate the intensity and timing of the incoming flood. They store the water during periods of high discharges in the river and release it after the critical high flow condition is over, so as to be ready to receive the next wave. Their effectiveness in moderating floods would depend on the reservoir capacity available at that time for absorbing the flood runoff and their proximity to the likely damage centre. They are operated with a carefully planned regulation schedule which takes into account both the safety of the dam and related structures and the safe carrying capacity of the lower reaches of the river in their present condition.
     
    Reservoirs are more effective for flood management if, apart from the incidental moderation available for any type of storage on a river, specific flood space is earmarked, as in the case of DVC dams across the Damodar and its tributaries. The operation schedule or rule curve being followed should be reviewed and a suitable operation schedule/rule curve prescribed for the monsoon filling to ensure space for flood moderation but which can be filled for conservation at a later stage when high flows end.
     
    In order to improve the efficiency of the reservoirs and improve the operation schedules for providing either incidental or specific flood moderation effects, arrangement for inflow forecasts should be made. 10.1.2 Detention Basins Detention basins are usually formed by utilizing natural depressions/ swamps and lakes by improving their capacity by constructing encircling embankments and providing suitable devices for regulating the release of stored waters. Since, the land under the marshes or low depression may hardly require much compensation and rehabilitation measures, this method are relatively in expensive. The Ghaggar detention basin in Rajasthan is a good example. Depressions available upstream of Srinagar City, on the left bank of river Jhelum, the Mokama Tal area in Bihar and Ottu, Bhindawas, Kotla lakes in Haryana and various beels/haors of Barak basin are some examples of a few natural basins.
     
  • fldmgmthandbook
    Reservoirs can moderate the intensity and timing of the incoming flood. They store the water during periods of high discharges in the river and release it after the critical high flow condition is over, so as to be ready to receive the next wave. Their effectiveness in moderating floods would depend on the reservoir capacity available at that time for absorbing the flood runoff and their proximity to the likely damage centre. They are operated with a carefully planned regulation schedule which takes into account both the safety of the dam and related structures and the safe carrying capacity of the lower reaches of the river in their present condition.
     
    Reservoirs are more effective for flood management if, apart from the incidental moderation available for any type of storage on a river, specific flood space is earmarked, as in the case of DVC dams across the Damodar and its tributaries. The operation schedule or rule curve being followed should be reviewed and a suitable operation schedule/rule curve prescribed for the monsoon filling to ensure space for flood moderation but which can be filled for conservation at a later stage when high flows end.
     
    In order to improve the efficiency of the reservoirs and improve the operation schedules for providing either incidental or specific flood moderation effects, arrangement for inflow forecasts should be made. 10.1.2 Detention Basins Detention basins are usually formed by utilizing natural depressions/ swamps and lakes by improving their capacity by constructing encircling embankments and providing suitable devices for regulating the release of stored waters. Since, the land under the marshes or low depression may hardly require much compensation and rehabilitation measures, this method are relatively in expensive. The Ghaggar detention basin in Rajasthan is a good example. Depressions available upstream of Srinagar City, on the left bank of river Jhelum, the Mokama Tal area in Bihar and Ottu, Bhindawas, Kotla lakes in Haryana and various beels/haors of Barak basin are some examples of a few natural basins.
     
  • Central water comission 20 river basins for gauge, discharge, sediment & water quality observations
  • (water, sewerage,
    communication)
    (water, sewerage,
    communication)
    (medical costs & disruption to work activities

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