Types of flooding
Flooding in the Cape Town municipal area is complex due to the different types of flooding that can occur, and the possible linkage between them.
- Stormwater Flooding or Surface Run-off
- High-intensity rainfall can cause flooding when the stormwater systems and canals do not have the necessary capacity to drain away the amount of rainwater. Flooding (usually in urban areas) may also be caused by the lack of adequate drainage or caused by water running down surfaces that do not absorb water easily, i.e. hardened surfaces such as tarred roads and down mountain slopes in urban areas.
- Water-table or Seepage Flooding
- Flooding which occurs due to a high water table that results in water rising above ground level. This is often experienced in the Cape Flats areas of Cape Town, especially in what are considered the old wetland or vlei areas, after significant winter rainfall which fills the underground aquifers.
- River (Riverine and Estuarine)
- Flooding due to rain or severe storms in the catchment areas of our major rivers leading to the rising water level of these rivers and estuaries. The floodplains along the river may even have water levels rising to the 1 in 50-year and 1 in 100-year flood levels thereby creating a danger to those within those areas.
- Flash Floods
Flash flooding happens when intense thunderstorms result in large quantities of rain into steep or urban watersheds in a short period of time. Flash floods are difficult to predict, but even small, insubstantial or dry rivers and streams may suddenly experience an extremely rapid rise in water level with a very strong flow, and can therefore present many dangers.
- Coastal or Marine Flooding
Coastal areas that are flooded by seawater due to severe storms (Sea or Storm Surge) or geological events such as earthquakes under the ocean (Tsunami).
- Refers to low-lying and or marshy areas (vleis) with poor drainage soils, resulting in the accumulation of water that can take weeks to evaporate.
- Localised flooding occurring in the inside of poorly constructed buildings that are not properly water-proofed.
What can you do?
- When you learn of a major storm warning, also associate it with the possibility of inland flooding.
- Determine whether you live in a potential flood zone. (Near a river or stream is a possible flash flood zone, and on low-lying ground such as the Cape Flats area is a possible water-table flooding zone.)
- If advised by the authorities to evacuate, do so immediately.
- Keep abreast of road conditions through the news media.
- Move to a safe area before access is cut off by flood water.
- Do not attempt to cross flowing water. As little as 20cm of water depth may cause you to lose control of your vehicle.
Click on these digital brochures to learn more: Floods: Warning, Preparedness and Safety
Protect Yourself from Floods
Planning for a flood
Nobody can stop a flood, but if you are faced with one, there are actions you can take before, during and after to protect your family and keep your property losses to a minimum. The most important thing is to make sure your family is safe! Before a flood
What is your flood risk? Your community officials or local emergency management office are your best resources to learn about the history of flooding for your region. Ask whether your property is on the floodplain and if it is above or below the flood stage water level. By drafting your own Family Emergency Plan
Link to relevant document in Resources and identifying all your risks, including those hazards affecting your own environment, you can make a positive contribution to preparedness. Have disaster supplies on hand
- Flashlights and extra batteries.
- Portable, battery-operated radio and extra batteries tuned to a local station, and follow emergency instructions.
- First aid kit and manual.
- Emergency food and bottled water.
- Non-electric can opener.
- Essential medicines.
- Cash and credit cards.
- Sturdy shoes.
- Cell phones.
- Dry clothing.
If you live in a frequently flooded area, take preventative measures and stockpile emergency building materials
- Plywood, plastic sheeting, timber, nails, hammer and saw, pry-bar, shovels and sandbags.
- Have check-valves installed in building sewer traps to prevent flood waters from backing up in sewer drains.
- As a last resort, use large corks or stoppers to plug showers, tubs, or basins.
Plan and practice an evacuation route
- Learn flood-warning signs and your community's alert signals.
- Contact your local emergency management office for a copy of the community flood evacuation plan.
- This plan should include information on the safest routes to shelters. People living in potential flash flood areas should have several alternative routes. Request information on preparing for floods and flash floods.
Develop an emergency communication plan
Time permitting, these steps can be taken before the flood waters arrive
- In case family members are separated from one another during floods or flash floods (a real possibility during the day when adults are at work and children are at school), have a plan for getting back together.
- Ask an out-of-town relative or friend to serve as the "family contact." After a disaster, it's often easier to call long distance. Make sure everyone in the family knows the name, address and phone number of the contact person.
- Make sure that all family members know how to respond after a flood or flash flood. Teach all family members how and when to turn off the gas, electricity and water.
- Teach children how and when to call emergency numbers (police, ambulance, fire and rescue services, electricity and water services), and which radio station to tune into for emergency information.
- Be prepared to evacuate.
During a flood
- Turn off all utilities at te main power switch and close the main gas valve if evacuation appears necessary.
- Move valuables, such as documents, jewellery, clothing and photographs to upper floors or higher elevations.
- Fill bathtubs, sinks and plastic bottles with clean water. (Sanitize the sinks and tubs first by using bleach, rinse, then fill with clean water.)
- Bring outdoor possessions, such as lawn furniture, grills and refuse bins inside, or tie them down securely.
- Don't drive through a flooded area. If you are faced with a flooded road, turn around and go another way. More people drown in their cars than anywhere else!
- If your car stalls, abandon it immediately and climb to higher ground. Many deaths have resulted from attempts to move stalled cars.
- Don't walk through flooded areas. As little as 20cm depth of moving water can knock you off your feet. There may also be hidden flotsam and debris in the water.
- Stay away from downed power lines and electrical wires. Electrocution is another major source of deaths during floods as electric current passes easily through water.
- Look out for animals - especially snakes. Animals lose their homes in floods too. They may seek shelter in yours.
- I flood water starts to rise inside your house before you have evacuated, retreat to the second floor or the roof.
- Take disaster supplies with you – see the list above. Then wait for help.
- Don't try to swim to safety - wait for rescuers to come to you.
- If outdoors climb to high ground and stay there.
Flash floods develop quickly. They can occur anywhere - along rivers or creeks, in low water crossings or in a dry stream bed. They can occur during any month and at any time day or night, even when there hasn’t been much rain at your location, i.e. the water may have originated elsewhere! Flash floods often occur at night when it is difficult for people to find an escape route. They can be deceptive - flood waters are likely to be deeper and moving faster than you would perceive them to be.
- Avoid low water crossings.
- Us0 alternative routes to avoid flood prone areas.
- Leave your vehicle immediately if it stalls in flood waters.
- Move to higher ground if you can do so safely.
- Most cars and light trucks or SUVs may begin to float in as little as 30cm depth of water!
- Act quickly; rising waters make vehicle doors difficult to open.
If you are outside
- Everyone, especially children, should stay away from flooded streams, rivers, canals or drainage ditches.
- Swiftly flowing water can quickly sweep away even the strongest swimmers.
- Soggy banks can collapse, dumping you into floodwaters.
After a flood
Flood dangers do not end when the water begins to recede. Listen to a radio or television and don't return home until authorities indicate it is safe to do so. Remember to help your neighbours who may require special assistance – especially infants, elderly people and people with disabilities.
- If your home, apartment or business has suffered damage, call the insurance company or agent who handles your flood insurance policy right away to file a claim.
- Before entering a building, inspect foundations for cracks or other damage. Don't go in if there is any chance of the building collapsing.
- Upon entering the building don't use matches, cigarette lighters or any other open flames, since gas may be trapped inside. Instead, use a flashlight to light your way.
- Keep power off until an electrician has inspected your system for safety.
- Floodwaters pick up sewage and chemicals from roads, farms and factories. If your home has been flooded, protect your family's health by cleaning up your house right away. Throw out foods and medicines that may have met floodwater.
- Until local authorities proclaim your water supply to be safe, boil water for drinking and food preparation vigorously for five minutes before using.
- Be careful walking around. After a flood, steps and floors are often slippery with mud and covered with debris, including nails and broken glass.
- Take steps to reduce your risk of future floods. Make sure to follow local building codes and ordinances when rebuilding, and use flood-resistant materials and techniques to protect yourself and your property from future flood damage.
Inspecting utilities in a damaged home
Check for gas leaks:
If you smell gas or hear a blowing or hissing noise, open a window and quickly leave the building. Turn off the gas at the outside main valve if you can, and call the gas company from a neighbour's home. If you turn off the gas for any reason, it must be turned back on by a professional.
Look for electrical system damage:
If you see sparks or broken or frayed wires, or if you smell hot insulation, turn off the electricity at the main fuse box or circuit breaker. If you have to step in water to get to the fuse box or circuit breaker, call an electrician for advice.
Check for sewage and water line damage:
If you suspect sewage lines are damaged avoid using the toilets and call a plumber. If water pipes are damaged, contact the water department and avoid the water from taps. You can obtain safe water by melting ice cubes.