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.
types of flood & flood mitigation/management techniques - damages
1.
2. Semester : BE - 5th Civil-A
Subject : Hydrology & Water Resources Engineering
Code : 2150602
Presentation On : Flood Management
Prepared by : Eddy Ankit Gangani
eddygangani@gmail.com
3. What is Flood ?
What is Flood Management ?
Types of flood
Causes Of Flood
4. 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.
5.
6. 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
7. 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.
8. 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
10. 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 .
11. 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.
12. 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
13. 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
15. 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
16. 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
17. Mitigation
Measures
• Flood forecasting -
For emergency evacuation
Flood forecasting through range
of hydrodynamic/ snowmelt /
flood routing models.
Flood warnings
CWC National Flood
Forecasting Network
18. 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
19. 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
20. 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
21. 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
Notas del editor
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
