Urban Floods and Disaster Management

What to remember

• A disaster is a hazard that meets a weak community. Risk grows with hazard and exposure, and falls with capacity. Good planning reduces exposure and raises capacity.
• The Disaster Management Act, 2005 gives a three-tier system: National (NDMA), State (SDMA) and District (DDMA). The ward level carries out early warning, evacuation help and relief.
• Urban floods are mostly man-made in their effect. Blocked drains, encroached water bodies and paved surfaces turn normal rain into a flood.

Basic terms

A hazard is a natural or human event that can cause harm (cyclone, flood, earthquake, fire). A disaster is a serious disruption of a community that it cannot handle with its own resources. Vulnerability is how easily people, houses and services can be hurt. Capacity is the strength to prepare for, face and recover from a hazard. A simple way to remember: Risk = (Hazard x Vulnerability) / Capacity.

Disasters are grouped as natural (flood, cyclone, drought, earthquake, tsunami, landslide, heat wave), human-made (industrial accident, fire, stampede, chemical leak) and hybrid (urban flood made worse by poor drainage). Hazards also differ by speed: rapid onset (earthquake, flash flood) and slow onset (drought).

Disaster management cycle

Disaster management is a cycle, not a single act.

The first hour after an event is called the golden hour for saving lives.

Legal and institutional framework

The Disaster Management Act, 2005 is the main law. It created:

• National Disaster Management Authority (NDMA): chaired by the Prime Minister. It makes national policy and plans.
• State Disaster Management Authority (SDMA): chaired by the Chief Minister. In Andhra Pradesh this is the State Disaster Management Authority.
• District Disaster Management Authority (DDMA): chaired by the District Collector. The elected head of the local body (the Zilla Parishad chairperson in rural areas) is the co-chair.
• National Executive Committee, National Institute of Disaster Management (NIDM) and the National Disaster Response Force (NDRF), a specialist force for rescue. States have their own State Disaster Response Force (SDRF).
• Funds: National and State Disaster Response Funds for relief, and Mitigation Funds for prevention work.

Local bodies, including urban local bodies, must prepare and follow disaster plans within the district plan. Municipal corporations are responsible for drains, storm-water works and fire services.

International frameworks: the Yokohama Strategy (1994), Hyogo Framework (2005-2015) and the Sendai Framework for Disaster Risk Reduction (2015-2030). The Sendai Framework has seven global targets and four priorities: understanding risk, strengthening risk governance, investing in risk reduction, and better preparedness with "build back better".

Why cities flood

Urban floods are different from river floods. They are caused by heavy rain in a short time falling on a city that cannot drain it.

• 1. Impervious surfaces: roads, roofs and concrete stop rain from soaking into the ground, so runoff is faster and larger.
• 2. Poor or small drains: old storm-water drains built for lower rain, choked with plastic and silt.
• 3. Encroachment: tanks, lakes, canals and natural streams are built over, so water has nowhere to go.
• 4. Low-lying settlements and construction in flood plains.
• 5. Tidal effect in coastal cities: high tide or a storm surge blocks drains from emptying into the sea or river.
• 6. Climate change: more intense short-duration rain events.
• 7. Poor solid-waste management and weak maintenance before the monsoon.
• 8. Dam or tank releases upstream at the same time as heavy rain.

A flash flood comes within hours of intense rain, with little warning. A cloudburst is very heavy rain over a small area in a short time.

Prevention and management of urban floods

Structural measures are physical works. Non-structural measures are rules, plans, warnings and training, and are usually cheaper. A good plan uses both. The Central Water Commission issues river flood forecasts. The India Meteorological Department (IMD) issues weather warnings. The Indian National Centre for Ocean Information Services (INCOIS), Hyderabad, issues tsunami and ocean state warnings.

Cyclones and AP

Andhra Pradesh has a long coastline on the Bay of Bengal and is prone to cyclones, storm surge and coastal flooding, besides floods in the Godavari and Krishna basins. Visakhapatnam and other coastal towns face both wind and flood risk. Cyclones are named by the regional system for the north Indian Ocean.

IMD cyclone classes by maximum sustained wind speed:

IMD colour-coded warnings: Green (no action), Yellow (be aware), Orange (be prepared), Red (take action).

Cyclone safety: move to a designated cyclone shelter, keep a radio, stay away from the coast, switch off power, and do not go out until officials give an all-clear. Flood safety: move to higher ground, do not walk or drive through moving water, keep drinking water boiled, and avoid live electric wires.

Earthquake zones in India under the Bureau of Indian Standards are Zones II, III, IV and V; Zone V is the most severe.

Role of ward-level officials

A ward secretary is the first link between people and the system. Duties include keeping a list of vulnerable families (elderly, disabled, pregnant women, children), spreading early warnings, helping the evacuation and shelter, reporting blocked drains and encroachments to the municipality, helping damage assessment, and linking with health and sanitation teams to prevent disease after floods. Women, children and the disabled need special care in shelters.

Planning for resilient cities

Good urban planning treats disaster risk as part of every land-use decision. The city development plan should map flood-prone zones, natural drainage lines and low-lying areas, and keep them free of building. Buildings need to follow safety codes for earthquakes, wind and fire. Hospitals, schools and shelters should be placed on safe ground and have power and water backups.

Other useful steps are:

• Hazard, vulnerability and risk maps shared with ward offices, so that officials know which streets flood first.
• Community-based disaster management: trained local volunteers, self-help groups and youth who know the area and can act within minutes.
• Sanitation after floods: chlorination of water, clearing of waste and fogging to prevent cholera, dengue and leptospirosis.
• Insurance and compensation for housing and crops, and quick assessment of damage.
• Communication: alerts through loudspeakers, SMS, local television and radio, in the local language, with clear instructions on where to go.
• Special needs: separate space, toilets and privacy for women, safe places for children, and ramps or help for people with disabilities.

Relief work follows basic standards: shelters with safe water, toilets, food, health care and security. Records of families, damage and aid must be kept so that help reaches the right persons. After the event, lessons are written down and the plan is improved. This learning step closes the disaster management cycle.

Exam traps

• NDMA is chaired by the Prime Minister; SDMA by the Chief Minister; DDMA by the District Collector. Do not mix these.
• Hyogo (2005-2015) comes before Sendai (2015-2030).
• Mitigation is before the event; response is during and after; recovery is later.
• Structural means physical works; non-structural means rules, planning and warnings.
• A flash flood is fast and local; a river flood is slow and wide.
• Depression is the weakest cyclone class; super cyclonic storm is the strongest.
• IMD gives weather warnings; CWC gives river flood forecasts; INCOIS gives tsunami warnings.
• NDRF is the national response force; SDRF belongs to the state.

One-liners

• 1. The Disaster Management Act was passed in 2005.
• 2. The NDMA is headed by the Prime Minister.
• 3. The District Collector chairs the DDMA.
• 4. The Sendai Framework runs from 2015 to 2030.
• 5. The Hyogo Framework was for 2005-2015.
• 6. NDRF is the specialist force for disaster response.
• 7. INCOIS in Hyderabad gives tsunami warnings.
• 8. Impervious surfaces increase runoff in cities.
• 9. IMD red warning means take action.
• 10. A cyclonic storm has winds of 62-88 km/h.
• 11. Rainwater harvesting reduces runoff and recharges groundwater.
• 12. The first hour after a disaster is the golden hour.

Practice questions

1. Who chairs the National Disaster Management Authority under the Disaster Management Act, 2005?

   1. The Prime Minister
   2. The Chief Justice
   3. The Home Minister
   4. The President
   Answer

   A. The Prime Minister

   The Act names the Prime Minister as chairperson of the NDMA.

2. Who chairs the District Disaster Management Authority?

   1. The Revenue Divisional Officer
   2. The District Collector
   3. The Zilla Parishad chairperson
   4. The Superintendent of Police
   Answer

   B. The District Collector

   The Collector is chairperson; the elected local body head is co-chair.

3. The State Disaster Management Authority is chaired by

   1. The Governor
   2. The Chief Minister
   3. The Revenue Minister
   4. The Chief Secretary
   Answer

   B. The Chief Minister

   The Act gives the Chief Minister the chair of the SDMA.

4. The Sendai Framework for Disaster Risk Reduction covers the period

   1. 2015-2030
   2. 1994-2004
   3. 2020-2040
   4. 2005-2015
   Answer

   A. 2015-2030

   Sendai was adopted in 2015 as the successor to the Hyogo Framework.

5. Which framework came immediately before the Sendai Framework?

   1. Kyoto Protocol
   2. Yokohama Strategy
   3. Paris Agreement
   4. Hyogo Framework
   Answer

   D. Hyogo Framework

   Hyogo (2005-2015) was followed by Sendai.

6. Which phase of the disaster cycle includes building codes and flood zoning?

   1. Response
   2. Recovery
   3. Relief
   4. Mitigation
   Answer

   D. Mitigation

   Measures that reduce effects before an event are mitigation.

7. The first hour after a disaster, important for saving lives, is called the

   1. Golden hour
   2. Response clock
   3. Silver hour
   4. Critical window
   Answer

   A. Golden hour

   The golden hour is the first hour for rescue and first aid.

8. Which agency gives tsunami warnings in India from Hyderabad?

   1. NIDM
   2. CWC
   3. INCOIS
   4. NDRF
   Answer

   C. INCOIS

   INCOIS issues ocean state and tsunami warnings.

9. Which body issues river flood forecasts in India?

   1. NDMA
   2. Central Water Commission
   3. INCOIS
   4. India Meteorological Department
   Answer

   B. Central Water Commission

   CWC prepares river flood forecasts; IMD gives weather warnings.

10. In the IMD colour code, which colour means "take action"?

    1. Orange
    2. Yellow
    3. Red
    4. Green
    Answer

    C. Red

    Red is the highest warning level.

11. Which colour in the IMD warning code means "be prepared"?

    1. Orange
    2. Green
    3. Yellow
    4. Red
    Answer

    A. Orange

    Orange asks people to be prepared.

12. Which of the following is a non-structural flood measure?

    1. Embankment
    2. Retention pond
    3. Storm-water pump
    4. Early warning system
    Answer

    D. Early warning system

    Warnings, rules and planning are non-structural; physical works are structural.

13. Heavy rain over a small area in a very short time is called

    1. Monsoon break
    2. Cloudburst
    3. Western disturbance
    4. Drizzle
    Answer

    B. Cloudburst

    A cloudburst is very intense rain in a small area.

14. A cyclone with maximum sustained winds of 62-88 km/h is classed by IMD as a

    1. Cyclonic storm
    2. Deep depression
    3. Severe cyclonic storm
    4. Depression
    Answer

    A. Cyclonic storm

    62-88 km/h is the cyclonic storm class.

15. A cyclone with winds of 222 km/h and above is called a

    1. Severe cyclonic storm
    2. Extremely severe cyclonic storm
    3. Very severe cyclonic storm
    4. Super cyclonic storm
    Answer

    D. Super cyclonic storm

    The highest IMD class is the super cyclonic storm.

16. Which factor most directly increases surface runoff in a city?

    1. Permeable soil
    2. Paved and concrete surfaces
    3. Tree cover
    4. Open parks
    Answer

    B. Paved and concrete surfaces

    Impervious surfaces stop infiltration, so runoff rises.

17. Risk in disaster studies is best expressed as

    1. Vulnerability minus hazard
    2. Hazard plus capacity
    3. Hazard multiplied by vulnerability divided by capacity
    4. Capacity divided by hazard
    Answer

    C. Hazard multiplied by vulnerability divided by capacity

    Risk rises with hazard and vulnerability and falls with capacity.

18. A city drain built for old rain norms overflows in a new heavy rain. The main lesson is that

    1. Drains should be closed during rain
    2. Rain is always predictable
    3. Drain capacity must match changing rainfall and be maintained
    4. Floods are only natural
    Answer

    C. Drain capacity must match changing rainfall and be maintained

    Poor design and maintenance turn heavy rain into an urban flood.

19. Building over tanks and natural streams in a city mainly leads to

    1. Better groundwater recharge
    2. Less silt
    3. Lower runoff
    4. Loss of natural water storage and flooding
    Answer

    D. Loss of natural water storage and flooding

    Encroachment removes the storage and drainage routes of floodwater.

20. Which measure both cuts runoff and recharges groundwater?

    1. Closing drains
    2. Rainwater harvesting pits
    3. Concrete lining of tanks
    4. Higher compound walls
    Answer

    B. Rainwater harvesting pits

    Harvesting lets rain soak into the ground and reduces runoff.

21. A high tide at the time of heavy rain in a coastal city worsens flooding because

    1. It stops drains from emptying into the sea
    2. It removes silt
    3. It raises rain intensity
    4. It increases soil absorption
    Answer

    A. It stops drains from emptying into the sea

    Tidal backwater prevents storm drains from discharging.

22. Mock drills and training of volunteers belong to the phase of

    1. Mitigation
    2. Preparedness
    3. Reconstruction
    4. Recovery
    Answer

    B. Preparedness

    Getting ready to act is preparedness.

23. "Build back better" is a priority of

    1. The Kyoto Protocol
    2. The Yokohama Strategy
    3. The Montreal Protocol
    4. The Sendai Framework
    Answer

    D. The Sendai Framework

    Sendai includes better preparedness and building back better in recovery.

24. Who is the co-chair of the District Disaster Management Authority in a rural district?

    1. The District Judge
    2. The Superintendent of Police
    3. The Zilla Parishad chairperson
    4. The Block Development Officer
    Answer

    C. The Zilla Parishad chairperson

    The Act names the elected head of the local body as co-chair.

25. Seismic zoning of India by the Bureau of Indian Standards places the most severe area in

    1. Zone V
    2. Zone II
    3. Zone III
    4. Zone I
    Answer

    A. Zone V

    Zone V is the highest-risk earthquake zone.

26. Which is NOT a cause of urban flooding?

    1. Encroached water bodies
    2. Plastic choking the drains
    3. Wide, regularly desilted drains
    4. Extensive paved area
    Answer

    C. Wide, regularly desilted drains

    Properly maintained drains reduce flooding.

27. Which statement about disasters is correct?

    1. Disasters are always natural
    2. Capacity increases the damage
    3. Every hazard is a disaster
    4. A hazard becomes a disaster when it meets a vulnerable community
    Answer

    D. A hazard becomes a disaster when it meets a vulnerable community

    Disasters arise when a hazard exceeds the community's capacity.

28. At the ward level, an important duty during a flood warning is to

    1. Keep a list of vulnerable families and help them move to shelter
    2. Close all schools permanently
    3. Wait for the river to fall
    4. Stop all communication
    Answer

    A. Keep a list of vulnerable families and help them move to shelter

    Elderly, disabled and pregnant persons need early help.

29. Which pair is correctly matched?

    1. Earthquake - slow onset
    2. Flash flood - fast onset
    3. Drought - rapid onset
    4. Cloudburst - long duration
    Answer

    B. Flash flood - fast onset

    Flash floods come within hours; drought is slow onset.

30. Which is a hybrid (natural plus human) disaster?

    1. Lunar tide
    2. Urban flood made worse by blocked drains
    3. Volcanic eruption
    4. Solar eclipse
    Answer

    B. Urban flood made worse by blocked drains

    Rain is natural but poor drainage and encroachment worsen the flood.

31. Which of the following lowers vulnerability to cyclones in a coastal village?

    1. Cyclone shelters and early warning
    2. Building near the shore
    3. Removing mangroves
    4. Ignoring warnings
    Answer

    A. Cyclone shelters and early warning

    Shelters and warnings reduce loss of life.

32. Consider the statements on the Disaster Management Act, 2005: 1. It provides a National, State and District level structure. 2. The NDMA is chaired by the Chief Minister.

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    A. 1 only

    The Act creates three tiers, but the NDMA is chaired by the Prime Minister.

33. Consider the statements: 1. Structural measures include embankments and pumps. 2. Early warning is a structural measure.

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    A. 1 only

    Early warning is non-structural; embankments and pumps are physical works.

34. Consider the statements: 1. The Hyogo Framework preceded the Sendai Framework. 2. The Sendai Framework has four priorities.

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    C. Both 1 and 2

    Hyogo (2005-2015) came first, and Sendai lists four priorities.

35. Consider the statements: 1. INCOIS gives tsunami warnings. 2. CWC gives river flood forecasts.

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    C. Both 1 and 2

    Both agencies perform these roles.

36. Consider the statements: 1. A flash flood has little warning time. 2. Slow-onset hazards include drought.

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    C. Both 1 and 2

    Flash floods are sudden; drought develops slowly.

37. Consider the statements: 1. A depression is the strongest class of cyclone. 2. A super cyclonic storm has winds of 222 km/h and above.

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    B. 2 only

    Depression is the weakest class; super cyclonic storm is the strongest.

38. Consider the statements: 1. Mitigation takes place only after a disaster. 2. Preparedness includes mock drills.

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    B. 2 only

    Mitigation reduces effects before an event; mock drills are preparedness.

39. Consider the statements: 1. Permeable pavements reduce runoff. 2. Concrete surfaces reduce runoff.

    1. 1 only
    2. 2 only
    3. Both 1 and 2
    4. Neither 1 nor 2
    Answer

    A. 1 only

    Permeable surfaces let water soak in; concrete increases runoff.

40. Match the body with its role: NDRF, INCOIS, CWC, IMD

    1. Tsunami warning, weather warnings, rescue force, river forecasts
    2. Weather warnings, rescue force, tsunami warning, river forecasts
    3. River forecasts, rescue force, weather warnings, tsunami warning
    4. Rescue force, tsunami warning, river forecasts, weather warnings
    Answer

    D. Rescue force, tsunami warning, river forecasts, weather warnings

    NDRF rescues, INCOIS warns of tsunami, CWC forecasts rivers, IMD warns on weather.

41. Match the phase with an example in order: Mitigation, Preparedness, Response, Recovery

    1. Search and rescue, house repair, mock drill, flood zoning
    2. House repair, search and rescue, flood zoning, mock drill
    3. Mock drill, flood zoning, house repair, search and rescue
    4. Flood zoning, mock drill, search and rescue, house repair
    Answer

    D. Flood zoning, mock drill, search and rescue, house repair

    Each example fits the stated phase of the cycle.

42. If a catchment is paved so that runoff rises, which change in a storm-water drain should be expected for the same rain?

    1. Lower peak flow
    2. No change in flow
    3. Higher peak flow arriving sooner
    4. Flow only after a day
    Answer

    C. Higher peak flow arriving sooner

    Impervious area gives faster and larger runoff.

43. Why are non-structural measures often preferred along with structural ones?

    1. They stop all rain
    2. They remove the need for any drain
    3. They are always permanent works
    4. They are cheaper and cover warning, planning and training
    Answer

    D. They are cheaper and cover warning, planning and training

    A good plan uses both; non-structural measures are low-cost and wide in reach.

44. Which is the correct order of the IMD cyclone classes from weakest to strongest?

    1. Deep depression, depression, severe cyclonic storm, cyclonic storm
    2. Depression, deep depression, cyclonic storm, severe cyclonic storm
    3. Cyclonic storm, depression, deep depression, severe cyclonic storm
    4. Severe cyclonic storm, cyclonic storm, depression, deep depression
    Answer

    B. Depression, deep depression, cyclonic storm, severe cyclonic storm

    The classes rise by wind speed in that order.