Flood zoning is a non-structural flood mitigation technique that identifies areas with varying degrees of flood risk. It involves classifying land into flood hazard zones like low, medium, and high based on the probability of flooding. This information is then used for land use planning and regulation to restrict development in high flood risk areas. The key benefits are preventing flood damage to property and infrastructure through regulating construction in floodplains.

1. Flood Proofing, Land-Watershed Management,
Flood Hazard Risk, Flood Zoning, Flood Forecast
and Warning
Dr. Shahid Ali

13. FLOOD PROOFING
• Is a process for preventing or reducing flood damages to the structure and/or to the contents of buildings located in
flood hazard area.
• It involves altering or changing existing properties.
• Can be incorporated into the design and construction of new buildings.
Flood proofing is done
• By making structural or non structural changes.
• By adjustment in the design, construction.
BASIC TECHNIQUE
• Raising the foundation above the flood level using fill or supports.
• Surrounding the building with flood proof masonry or concrete walls or berms.
• Sealing all openings below the flood line.
Flood proofing on the basis of types of protection

14. ADVANTAGES OF THE TECHNOLOGY
• Can be undertaken by individual property owners without waiting for Government.
• Much more cost effective approach to reducing flood risk.
• Does not require the additional land that would be needed to offer the same degree of flood protection through
seawalls or dikes.
• Flood proofed structures are less likely to fail during floods.
DISADVANTAGES OF THE TECHNOLOGY
• Require current knowledge about flood Hazards, flood mapping and flood warning studies.
• Is effective where flood level is low.
• Does little to minimize damage caused by high velocity flood flow and wave action.
DEVELOPING A FLOOD PROOFING STRATEGY Considerations:
• Analysis of Flood Hazards
• Site Characteristics
• Building Characteristics
• Regulations
• Appearance
• Accessibility
• Benefit/Cost Analysis

15. How to choose your option ANALYSIS OF FLOOD HAZARDS
• Determination of potential depth of flood.
• To calculate the force acting upon a structure(hydrostatic, hydrodynamic,
and impact loads).
• Hydrodynamic forces consist of frontal impact by the mass of moving
water.
• Impact loads are imposed on the structure by objects carried by moving
water
Site Characteristics
• Should be evaluated with respect to mapped floodplains and
floodways and the potential for local flooding from storm water
conveyance elements.
• Soil properties during conditions of flooding (saturated soil
pressures, allowable bearing capacity, potential for scour, frost
zone location, permeability, and shrink-swell potential.)

16. BUILDING CHARACTERISTICS
• The building should be evaluated with respect to the type of construction and the condition of the structure.
• The type of foundation, foundation materials, wall materials, and the method of connection all play a role in
deciding which retrofitting method will be most applicable.
Appearance
• The final appearance of a building and property after retrofitting will depend largely on the retrofitting method used
and the Flood Protection Elevation (FPE).
• A change in appearance will not necessarily be a change for the worse.
Accessibility
• Accessibility refers to how easy or difficult it is to routinely reach and enter the building after the retrofitting project
is completed.
• In general, costs will increase as the FPE increases, but there may be tradeoffs between alternative methods.
The Federal Emergency Management Agency (FEMA)
• FEMA has published numerous references on the subject of flood proofing (FEMA 1984, 1986a, 1986b, 1991,
1993a, 1993b, 1993c, 1993d, 1993e, 1994, 1995, 1996)

17. Methods of flood proofing FEMA outlines six methods of flood proofing:
• Elevation
• Wet Flood Proofing
• Relocation
• Dry Flood Proofing
• Levees and Floodwalls
• Demolition

18. ELEVATION
• Raising the structure so that the lowest floor is above the flood level.
• Can be done by elevating the entire building, including the floor, or by leaving the building in its existing position and
constructing a new, elevated floor within the building.
Advantages
• Well known, and qualified contractors are often readily available.
• Reduces the flood risk to the building and its contents.
Disadvantages
• Cost may be prohibitive.
• Access to the building may be adversely affected.
• Additional costs are likely
• Lighter wood frame buildings are easier and cheaper
to raise than masonry buildings. Masonry buildings
not only are more expensive to raise, but are
susceptible to cracks

19. Elevation method

20. WET FLOOD PROOFING
• Is done by modifying the uninhabited portions (such as a crawl space or an unfinished basement) so that floodwaters
will enter but not cause significant damage to either the building or its contents
• Interior and exterior hydrostatic pressures is equal.
Advantages
• The loads on walls and floors will be less than
in a dry flood-proofed building.
• Wet flood-proofing measures are often less
costly than other types of retrofitting.
• The appearance of the building is usually not
adversely affected.
Disadvantages
• Limits the uses of the floodable area of the
building.
• Periodic maintenance may be required.
• Extensive cleanup may be necessary.

21. Relocation
• Moving a building to high ground, outside the flood hazard area
• Relocating a building usually involves jacking it up and placing it on
a wheeled vehicle, which delivers it to the new site.
Advantages
• Significantly reduces flood risk to the building and its contents.
• Techniques are well known, and qualified contractors are often
readily available.
Disadvantages
• Cost may be prohibitive.
• A new site must be located and purchased.

22. Dry Flood Proofing
• Requires sealing the walls with waterproof coatings, impermeable
membranes, or supplemental layers of masonry or concrete.
• The flood characteristics that affect the success of dry flood proofing are
flood depth, flood duration, flow velocity, and the potential for wave
action and flood-borne debris.
Precautions It is very tempting for the owner of a dry flood proofed
building to try to keep the flood out if floodwaters get deeper than two or
three feet. This can result in collapsed walls, buckled floors, and danger to
the occupants.
Advantages
• Less costly than other retrofitting
methods.
• Does not require the additional land
that may be needed for levees and
floodwalls.
Disadvantages
• Ongoing maintenance is required.
• Flood shields may not be aesthetically
pleasing.
• Damage to the exterior of the building
and other property may not be
reduced.

23. Levees and Floodwalls
• Levees and floodwalls are types of flood protection barriers
• Greater depths result in greater water pressures, so taller levees and floodwalls must be designed and constructed to
withstand the increased pressures.
• Levees are natural barriers made of clay, sand or sandy clay.
• Floodwall types are made of cement block bricks or poured concrete.
Advantages
• No significant changes to the building
will be required.
• The building can be occupied during
construction of levees and floodwalls.
Disadvantages
• An interior drainage system must be
provided.
• Local drainage can be affected, possibly
creating or worsening flood problems
for others.
• A large area may be required for
construction, especially for levees.

24. Demolition
• Means tearing down a damaged house and re-building it on the same place or a less vulnerable spot.
• May be the most practical of all when a building has sustained extensive damage, especially severe structural
damage.
• Whether rebuilding or moving, the damaged building must be torn down and the site restored.
• The advantages and disadvantages of demolition depend on the decision of where to rebuild the structure.
EMERGENCY FLOOD PROOFING MEASURES
• Emergency flood proofing measures are
set in motion on short notice.
• The techniques commonly used entail
building dykes or barriers using whatever
natural or stored materials may be on
hand at the site.
• Hard work involved.

25. Women involved in homestead raising
Making the strategy sustainable
Turfing and plants to protect the raised homestead from erosion
Strategy to development
• Flood plinth level study
• Flood hazard study
• House clustering
• Connecting road
• Providing training

26. WATERSHED
Area bounded by a drainage divide and draining all the water incident upon it through a common outlet (stream or river),
or to a common point/place (lake, pond).
Problems Associated with Watersheds
• Flooding
• Unstable Slopes / Land Slides
• Erosion from Denuded Land
• Deficient Water Supplies
• Energy Shortage
• Food Shortage
• Poor Quality Drinking Water
• Polluted Streams / Reduced Fishing
• Sedimentation of Navigation Tracks.
Watershed management is the study of the relevant characteristics of a watershed aimed at
• the sustainable distribution of its resources
• processing of creating and implementing plans, programs, and projects
• Enhancing watershed functions that affect the plant, animal, and human communities within a watershed boundary

27. Components of Watershed Management
• Entry Point Activity (EPA)
• Land and Water Conservation Practices
• Integrated Pest and Nutrient Management
• Crop Diversification and Intensification
• Use of Multiple Resources
• Capacity Building
Watershed Management Measures
Watershed Management Needs Both
Integrated Approach
Consideration of All Measures
Consortium Approach
Consideration of Stakeholders

28. Program Design Considerations
• How far should the concept of integrated watershed management go?
• Who should be the target (and receive the most benefits) of a watershed program –upstream farmers and rural
inhabitants or downstream town and city dwellers?
• Should planning be carried out at the farm level or watershed level?
• Should a watershed program emphasize rehabilitation or prevention?
Program Design Considerations
• What type of protection or rehabilitation should be emphasized: structural or vegetative?
• Should watershed programs include incentive schemes to encourage upstream inhabitants to participate in a
watershed program?
• Can market mechanisms help to increase the services that watersheds provide, such as quantity and quality of water?

29. Watershed Development & Modelling
• Watershed Characteristics.
• Hydrology of watershed.
Parameters of Watershed
• Size
• Shape
• Physiography
• Climate
• Drainage
• Land use
• Vegetation
• Geology and Soils
• Hydrology
• Hydrogeology
• Socioeconomics
Watershed modelling steps
• Formulation
• Calibration/verification
Application Watershed model constitutes
• Input function
• Output function
• Transform function

31. Models Broadly classified into three types
Black Box Models: These models describe mathematically the relation between rainfall and surface runoff
without describing the physical process by which they are related. e.g. Unit Hydrograph approach
Lumped models: These models occupy an intermediate position between the distributed models and Black
Box Models e.g. Stanford Watershed Model
Distributed Models:
These models are based on complex physical theory, i.e. based on the solution of unsteady flow equations.
General Classification of Models

32. Concepts and Principles of IWM
Objectives:
• Water has multiples uses and must be managed in an integrated way.
• Water should be managed at the lowest appropriate level.
• Water allocation should take account of the interests of all who are affected.
• Water should be recognized and treated as an economic good.
Strategies:
• A long term, viable sustainable future for basin stake holders.
• Equitable access to water resources for water users.
• The application of principles of demand management for efficient utilization.
• Prevention of further environmental degradation(short term) and the restoration of
• degraded resources (long term).
The four engineering and management tools for effective and sustainable development of water resources
in semi-arid regions:
• Appropriate technologies
• Decentralized development system
• Catchment based water resources planning
• Management information system

33. Water Conservation
• Important step for solutions to issues of water and environmental conservation is to change people's attitudes and habits
• Conserve water because it is right thing to do!.
What you can do to conserve water?
• Use only as much water as you require. Close the taps well after use. While brushing or other use, do not leave the tap
running, open it only when you require it. See that there are no leaking taps.
Use a washing machine that does not consume too much water. Do not leave the taps running while washing dishes and
clothes.
• Install small shower heads to reduce the flow of the water. Water in which the vegetables & fruits have been washed -use
to water the flowers & plants.
• At the end of the day if you have water left in your water bottle do not throw it away, pour it over some plants.
• Re-use water as much as possible
• Change in attitude & habits for water conservation
• Every drop counts!
Rain Water Harvesting?.
• Rain Water Harvesting RWH-process of collecting, conveying & storing water from rainfall in an area for beneficial
use.
• Storage –in tanks, reservoirs, underground storage-groundwater
Water Conservation and Harvesting

34. • RWH -yield copious amounts of water. For an average rainfall of 1,000 mm, approximately four million litres of
rainwater can be collected in a year in an acre of land (4,047 m2), post-evaporation.
• As RWH -neither energy-intensive nor labor-intensive
• It can be a cost-effective alternative to other water-accruing methods.
• With the water table falling rapidly, & concrete surfaces and landfill dumps taking the place of water bodies,
RWH is the most reliable solution for augmenting groundwater level to attain self-sufficiency
RWH –Methodologies
• Roof Rain Water Harvesting
• Land based Rain Water Harvesting
• Watershed based Rain Water harvesting
• For Urban & Industrial Environment
• Roof & Land based RWH
• Public, Private, Office & Industrial building
• Pavements, Lawns, Gardens & other open spaces

36. Rain Water Harvesting–Advantages
• Provides self-sufficiency to water supply
• Reduces the cost for pumping of ground water
• Provides high quality water, soft and low in minerals
• Improves the quality of ground water through dilution when recharged
• Reduces soil erosion & flooding in urban areas
• The rooftop rain water harvesting is less expensive & easy to construct, operate and maintain
• In desert, RWH only relief
• In saline or coastal areas & Islands, rain water provides good quality water

37. Impacts of land use on flood hazards
With increasing human alteration and development of the catchment area, the runoff generation process is
changed, especially through decreasing the infiltration capacity of the soil and the change of soil cover. This has
lead to concern over the role human alterations of the catchments play in increasing flood hazards.

38. Effect of specific development intervention on flood hazards
Construction of transport infrastructure and cross drainage works

39. Effect of land use change processes on flood hazards Urbanization

40. Agricultural Practice

41. Impact of land use on flood damage potential Flood

42. Land use planning and flood management
Land use Planning
Regional planning,
Town and country planning,
Urban planning
Spatial planning
Land use planning processes

43. Flood management planning processes

44. Other Planning Processes

45. Development management techniques in the flood hazard context

46. Planning permits

49. Flood Risks

53. Factors Influencing Flood Hazard

58. Assessment of Flood Vulnerability

60. Flood Risk Estimation
For example, if D=10 million Rupees for a 20 year return flood, therefore

63. Flood Frequency Analysis
Inundation map at different return period

64. Crop stage-damage curve has been developed
through several field survey are conducted to
gathering of crop damage data from actual
flood event for agricultural crops

67. Flood Zoning
• is a non structural measure of flood mitigation
• procedure to identify areas of varying flood hazard
• a precursor to land use regulation
• provides helpful information about flood risk management
Flood Zones
• Land area in terms of risk of flooding
• adapted flood hazard maps for planning purposes
• Classified as low, medium or high hazards according to varying levels of flood risk &type of flooding
for development of detailed hazard zoning maps, following graph is used indicating:
• Red: elevated danger
• Blue: medium danger
• Yellow: low/residual danger
• Yellow- white: indication of an extreme event
Flood Zoning Maps
A graphical system used in
some Scandinavian countries
Federal Emergency Management Agency (FEMA)

68. Flood Insurance Rate Map (FIRM)
• official map of a community indicating special hazard areas
• display areas that fall within the 100 year flood boundary
• used in town planning, insurance industry, by individuals for protecting properties
• used to set rates of insurance against risk of flood
• FEMA's Digital Flood Insurance Rate Map (DFIRM) database

69. Classification of Flood Zones
• Flood Zone 1 –Low Probability
land which have probability of river or sea flooding less than 1 in 1,000 annual(<0.1%).
• Flood Zone 2 –Medium Probability
zone comprises land assessed as having between a 1 in 100 and 1 in 1,000 annual probability of river flooding (1% –0.1%),
or between a 1 in 200 and 1 in 1,000 annual probability of sea flooding (0.5% –0.1%) in any year

73. Data Required for Flood Zoning

74. Modified rational model integrated with GIS Stage
Stage 1
Stage 2
Stage 3
Stage 4

77. Role of Flood zoning as non-structural measure:
Advantages
• no new roads or buildings will be constructed to reduce damage
• provides recreational opportunities
• flooding is more predictable
• provides helpful information about flood risk management
• helps in assigning priority for the development of very high risk, moderate high risk & low risk areas
• management implications for emergency preparedness (aid and relief)
• public awareness
Disadvantages
• It restricts development, which is a problem when there is a shortage of housing
• It can't be used in areas which are already urbanized

78. Flood Forecasting is the use of real-time precipitation and stream flow data in rainfall-runoff and stream
flow routing models to forecast flow rates and water levels for periods ranging from a few hours to days
ahead, depending on the size of the watershed or basin.
• outcome of flood forecasting is a set of forecast time-profiles of channel flows or river levels at various
locations
• "flood warning" is the task of making use of these forecasts to make decisions about whether warnings of
floods should be issued to the general public or whether previous warnings should be rescinded or
retracted.
Flood Forecasting and Modelling

79. Role of flood forecasting in flood management

80. Limitations of flood forecasting
• in mountain basins
• Every storm is different and rivers react differently
• too many uncertainties
• involved to give specific times for peak levels more than two to six hours ahead.

83. Measurement of water level and
Flow monitoring

84. 10. Model Verification

86. B

93. small