Flood

Floods can be very high-impact events. Annual flooding is a natural phenomenon long associated with increased soil fertility, but human habitation and land-use practices lead to many adverse impacts. Less frequent but unexpected flooding, caused by the interplay of natural and human factors, occur worldwide.

Natural causes include: high-intensity or prolonged rains, storms and storm surges, sudden melting of snow or ice, sudden release of water held or diverted by ice or debris jams, drought. Man-made causes include: the failure of water containment and drainage system, human-generated refuse in riverbeds, and run-off channels, deforestation, unsustainable land management, urban cement and asphalt cover.

Flood impacts include death, injury, damage to property and infrastructure, severe erosion, ground instability, food shortage, containment of drinking water and deposits of mud, sand and gravel. Floods can lead to loss of shelter and livelihoods, and can disrupt lifeline infrastructure and destroy communities.

[Source: IFRC, “Public Awareness & Public Education For Disaster Risk Reduction: Key Messages”]

Household

Individuals and households play an essential role in protecting themselves and their communities from flood risk by reducing their exposure to flood risk, educating household members on how to prepare for and respond during a flood, helping protect community resources, ensuring the safety of vulnerable neighbors, strengthening their own coping and recovery strategies, and advocating for greater government attention to risk reduction. Key steps individuals and households can take:

Know your area’s flood risks

  • If flood plains have been mapped, find out whether you are located on a flood plain, and learn about the elevation of your property and building relative to predictable flood levels
  • Maintain communication with neighbors located above and below you
  • Speak with local authorities and neighbors to find out whether your area is prone to flooding and how flood risk is being addressed
  • Households can begin by identifying the likelihood of floods in their community and factors that might increase this risk to flooding (e.g. new road construction that may alter traditional drainage patterns)

Store valuables and dangerous materials above likely water levels

  • If there is significant chance of flooding, households may want to take steps to ensure that key assets are stored above ground and if possible in raised areas to protect them from flood risks which may develop very rapidly.
  • Keep important papers, equipment, feedstock and other valuables above potential flood levels, using waterproof containers where possible
  • Keep hazardous chemicals above anticipated flood levels

Consider relocating or mitigating and adapting

  • If you live in a place prone to frequent or serious flooding, consider relocating, building elevated storage buildings or using floating shelters

Plan to protect your animals

  • consider precautionary evacuation of your livestock and pets

Know your area’s expected flood evacuation routes

  • Idenitify your safe evacuation routes, using any forms of transportation available to you, as well as routes that can be used on foot
  • Create family disaster plan–households should plan together in advance how each household member will get to a safe place from any of the locations where they spend significant amounts of time (school, workplace, daycare, etc.); how they will contact one another and get back together if separated; and what they will do in different situations

Build and maintain your home with floods in mind

  • If you live on a flood plain, build an appropriate foundation and elevate your home
  • Construct wells and latrines in safe places, above expected flood levels
  • If you are advised to for your specific conditions, install back-flow valves in plumbing to prevent floodwater from backing up into drains
  • When you make renovations or alterations, wet-flood proof the construction
  • Choose flood damage-resistant materials for areas that usually get wet, raise electrical circuits 1.2M (4ft) above the floor, put appliances on pedestals, and design walls so that cavities drain

Maintain water channels

  • If you change the natural course of a river or stream, make sure its water-carrying capacity is not reduced
  • Keep water channels, drainpipes and gutters clear of debris

Provide a raised plinth for animals

  • If you have livestock or large animals that cannot be transported, create a raised plinth, with access, so that the animals can move to higher ground in the event of flooding

Construct barriers to prevent floodwater from entering buildings

  • Construct levees, berms or flood walls in accordance with local building regulations, to prevent floodwater from entering your building
  • Identify the best methods to prevent water from entering your home, depending on your construction type and location
  • If possible, create a barrier in front of your doors and vents to keep water out
  • Make sure you have the supplies and time available to implement your solution (examples of temporary barrier solutions include washboards, sandbags and anchored heavy plastic sheeting that can be used to channel water away from your building)
  • If you plan to fight floods with barriers, decide in advance when you will abandon the fight and save your life

Keep supplies to protect your home

  • If you live in an area prone to flooding, keep supplies (such as plywood , plastic sheeting, nails, hammers, a saw, a crow bar, sand, shovels and sandbags), to protect it
  • During rainy season and flood conditions, keep your family vehicle’s fuel tank filled

Keep supplies to protect people from drowning and as floating transportation

  • Buy or make personal flotation devices
  • Keep a ladder and rope for escaping to the roof
  • Keep an inflatable boat or make an improvised group flotation platform

[Source: IFRC, “Public Awareness & Public Education For Disaster Risk Reduction: Key Messages”]

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Workplace

Workplaces play a key role in flood preparedness through business continuity planning to protect their employees, lessen the financial impact of floods, and re-open their businesses quickly to support economic recovery in the community. In addition, workplaces can also be advocates in the community for flood preparedness and resilience to protect their employees and suppliers as well as their markets in communities that might potentially be affected.

Know your area’s flood risks

  • If flood plains have been mapped, find out if your business is located on a flood plain, and learn about the elevation of the property and building relative to predictable flood levels
  • Maintain communication with neighbors/tenants located above and below you
  • Speak with local authorities and neighbors to find out whether your area is prone to flooding and how flood risk is being addressed
  • Workplaces can begin by identifying the likelihood of floods in their community and factors that might increase this risk to flooding (e.g. new road construction that may alter traditional drainage patterns)
  • Identify industrial activity that may create hazardous materials release and contamination risks during flooding

Store valuables and dangerous materials above likely water levels

  • If there is significant chance of flooding, workplaces may want to take steps to ensure that key assets are stored above ground and if possible in raised areas to protect them from flood risks which may develop very rapidly.
  • Keep important papers, equipment, feedstock and other valuables above potential flood levels, using waterproof containers where possible
  • Keep hazardous chemicals above anticipated flood levels

Consider relocating or mitigating and adapting

  • If you live in a place prone to frequent or serious flooding, consider relocating, building elevated storage buildings or using floating shelters

Know your area’s expected flood evacuation routes

  • Idenitify your safe evacuation routes, using any forms of transportation available to you, as well as routes that can be used on foot
  • Create a workplace disaster plan–staff should plan together in advance how each member will get to a safe place; how they will be in contact with one another and business leadership; and learn what they will do in different situations

Select a safe site for your building

  • Avoid building within 200m (650 ft) of a high-tide coastline
  • Avoid building on riverbanks, gullies or fllod plains, unless you elevate and reinforce your building (with the exception of delta areas, where riverbanks are on high ground)

Build and maintain your workplace with floods in mind

  • If you decide to develop on a flood plain, build an appropriate foundation and elevate your business
  • Construct wells and latrines in safe places, above expected flood levels
  • If you are advised to for your specific conditions, install back-flow valves in plumbing to prevent floodwater from backing up into drains
  • When you make renovations or alterations, wet-flood proof the construction
  • Choose flood damage-resistant materials for areas that usually get wet, raise electrical circuits 1.2M (4ft) above the floor, put appliances on pedestals, and design walls so that cavities drain

Maintain water channels

  • If you change the natural course of a river or stream, make sure its water-carrying capacity is not reduced
  • Keep water channels, drainpipes and gutters clear of debris

Construct barriers to prevent floodwater from entering buildings

  • Construct levees, berms or flood walls in accordance with local building regulations, to prevent floodwater from entering your building
  • Identify the best methods to prevent water from entering your business, depending on your construction type and location
  • If possible, create a barrier in front of the doors and vents to keep water out
  • Make sure you have the supplies and time available to implement your solution (examples of temporary barrier solutions include washboards, sandbags and anchored heavy plastic sheeting that can be used to channel water away from your building)

Keep supplies to protect your business

  • If your business is located in an area prone to flooding, keep supplies (such as plywood , plastic sheeting, nails, hammers, a saw, a crow bar, sand, shovels and sandbags), to protect it
  • During rainy season and flood conditions, keep your work vehicles’ fuel tanks filled

Keep supplies to protect people from drowning and as floating transportation

  • Buy or make personal flotation devices
  • Keep a ladder and rope for escaping to the roof
  • Keep an inflatable boat or make an improvised group flotation platform

[Source: IFRC, “Public Awareness & Public Education For Disaster Risk Reduction: Key Messages”]

Additionally, consider creating a or revising your current workplace’s Business Continuity Program.

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Community Organization

Community organizations play an important linking and service delivery role in flood preparedness and resilience. Local residents and organizations are in a position to best identify their immediate needs, coordinate preparations, supplement government response efforts by implementing response programs, and contribute to local decision making for future events. [Source: ‘Effective Community Response to Disaster: A Community Approach to Disaster Preparedness and Response’]

Community organizations are an important liaison between community residents and local authorities, helping to channel community initiative and providing entry points for government support. This intermediary role can be especially important in isolated communities where community organizations often play a pivotal role in early warning and communication with at-risk communities.

To play these role, it is important for community organizations to build up the capacity and ability of communities themselves to over time design and carry out preparedness initiatives and be directly engaged in resource mobilization and advocacy with local authorities.

Stay Informed

  • Find out what types of disaster are likely to occur in your area or community and how to prepare for each
  • Find out how local authorities will contact the community during a disaster
  • Contact your local Red Cross Chapter for details about community disaster education presentations that may be arranged or are available in your community organization
  • Get trained in CPR and first aid so you will know how to respond to emergencies and aid your community in the event that help is delayed
  • Identify families who have gone through severe flooding and are willing to tell how they are better prepared and serve as disaster advocates for the community
  • Partner with Red Cross chapters and local emergency response units who may have upcoming community events in which they could share the preparedness message and hand out brochures

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Local and National Government

Local and national governments manage the strategies, planning, and investment for disaster preparedness and resilience undertaken by the state and its local subsidiaries. Moving beyond the dynamics of individual communities, it is local and national government that are the seat for societal decision-making on disaster risks related floods and other hazards, although other stakeholders play important advocacy roles in the governance process. Flood preparedness in particular requires a wide scope, as flood strategy should cover the entire flood catchment area (e.g. around a river basin) and promote coordinated development and management of actions regarding water, land and related resources. (European Union, 2004, ‘Best Practices on Flood Prevention, Protection and Mitigation’)

Know your area’s flood risks

  • Know the local terrain, water sources, catchment area and weather patterns, to better understand the risks
  • Map flood plains; if flood plains have been mapped, find out whether your community or parts of your community are located on a flood plain, and learn about the elevations of your community and buildings relative to predictable flood levels
  • Consider risk factors such as proximity to rivers, dykes and coastlines, blockage of channels or gullies, and urban infrastructure
  • Investigate historical experience and the potential impact of climate change on your community
  • Speak with neighboring jurisdictions to find out whether your communities are prone to flooding and how flood risk is being addressed
  • Maintain communication with neighboring jurisdictions
  • Identify industrial activity that may create hazardous materials release and contamination risk during flooding

[Source: IFRC, “Public Awareness & Public Education For Disaster Risk Reduction: Key Messages”]

Governments have a wide variety of options open to them for reducing flood risk. These include:

Types of approach Examples
structural / engineering: channel modifications; dams; retention ponds; levees, dikes, and floodwalls; floodway
non-structural: floodplain zoning; floodplain building codes; floodplain buyout programs; mortgage limitations
community-based

[Source:Tulane University, Dept. Earth & Environmental Sciences]

Consider useful partnerships

  • Partner with local Red Cross chapter departments and other emergency management agencies who may have upcoming community events in which they could share the preparedness message and hand out brochures
  • Contact local or national weather service offices or emergency management agencies for information on local hurricane warning systems and link this information into other local and national government websites
  • Invite local meteorologist and disaster preparedness practitioners to provide tips for the local population on air
  • Team up with local merchants for a display about an emergency preparedness kit
  • Publish a special section in local newspapers with emergency information on hurricane watch and warnings that includes the phone numbers of local emergency services offices, local Red Cross chapters, and the nearest hospitals
  • If meteorologists are predicting flooding, pitch preparedness tips to radio and television stations, as well as posting those tips immediately on local and national government websites

Depending on their size and severity, floods can roll boulders and vehicles, tear out trees, destroy buildings and bridges, bring down power lines, cover roads and fill basements. Floodwater may rise to several stories, reaching heights of 3-6m (10-20ft), and can trigger deadly debris slides. Debris in floodwater can accumulate in tight passages, creating flooding above the blockage and flash flooding below when the dam breaks. In coastal outlet areas, floodwater can move at 10-15km (6-10mph), spreading widely as the terrain permits.

The two main types of floods are inundation floods (which are slow, developing over hours or days) and flash floods (which occur without warning, in places where there are no streams, generally within six hours of a rain event, or after dam or levee failure). Within these two types, the major kinds of flooding are:

  1. river flooding: a natural event for any river, creek or stream when the catchment receives more water than usual. Development on the flood plain and alteration of the flood plain terrain can cause flooding or make it worse. It may be slow or fast.
  2. run-off from higher ground: water flowing from mountains toward the sea may collect in low or flattened areas, creating ‘sheet flooding’ run-off
  3. costal flooding: inundation caused by sea water above normal tides. Causes can include prolonged or strong onshore flow of wind, storm surges and  astronomical tides or tsunamis generated by earthquakes
  4. outburst flooding: created by unexpected dam or glacial breakage
  5. urban flooding: created by impermeable ground cover (such as concrete and asphalt) that increases run-off two-to-six times more than natural terrain. Urban streets can become swiftly moving rivers, while basements and viaducts can collect water

In addition to standard disaster preparedness measures, early warning is a critical tool for limiting the loss of life and assets due to floods. New technologies are continuing to provide improved tools for measuring flood hazard conditions and enabling easy communication.

[Source: IFRC, “Public Awareness & Public Education For Disaster Risk Reduction: Key Messages”]

Floods can also potentially increase the transmission of the following communicable diseases:

  • water-borne diseases, such as typhoid fever, cholera, leptospirosis and hepatitis A
  • vector-borne diseases, such as malaria, dengue and dengue hemorrhagic fever, yellow fever, and West Nile Fever

Flooding is associated with an increased risk of infection, however this risk is low unless there is significant population displacement and/or water sources are compromised.

Communicable disease risks from flooding can be reduced if proper guidelines are followed.

Other health risks posed by flooding:

  • drowning and injuries or trauma
  • hypotermia (particularly in children), if trapped in floodwaters of length perods
  • respiratory tract infections due to exposure (loss of shelter, exposure to flood waters and rain)
  • power cuts related to floods may disrupt water treatment and supply plans, thereby increasing the risk of water-borne diseases

[Source: WHO]

  • river flooding: a natural event for any river, creek or stream when the catchment receives more water than usual. Development on the flood plain and alteration of the flood plain terrain can cause flooding or make it worse. It may be slow or fast.
  • run-off from higher ground: water flowing from mountains toward the sea may collect in low or flattened areas, creating ‘sheet flooding’ run-off
  • costal flooding: inundation caused by sea water above normal tides. Causes can include prolonged or strong onshore flow of wind, storm surges and  astronomical tides or tsunamis generated by earthquakes
  • outburst flooding: created by unexpected dam or glacial breakage
  • urban flooding: created by impermeable ground cover (such as concrete and asphalt) that increases run-off two-to-six times more than natural terrain. Urban streets can become swiftly moving rivers, while basements and viaducts can collect water

[Source: IFRC, “Public Awareness & Public Education For Disaster Risk Reduction: Key Messages”]

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