How can I stop floodwaters from entering my home?

Main Points

Tornadoes, hurricanes, and wildfires may be the most feared natural disasters for homeowners. However, flooding is the most frequent occurrence in the United States. Regardless of location—whether in low-lying woodlands near rivers or on higher suburban terrains—flooding can occur. This is because it doesn't require a specific set of weather conditions to take place. Factors like melting snow, breached dams or levees, excessive rainfall, and poor landscaping can all lead to flooding.

Flooding can occur almost anywhere, but some landscapes are more vulnerable than others. Areas that are highly susceptible to flooding, typically due to proximity to bodies of water, are known as floodplains. The likelihood of flooding in a floodplain is measured in terms of years, such as a 100-year floodplain. This refers to the probability of floods occurring in consecutive years, not the average interval between them. For instance, in a 100-year floodplain, there's a 1 percent chance of a flood happening the following year [source: Organization of American States]. Similarly, a 20-year floodplain has a 5 percent chance of flooding again.

Whether your home lies on a floodplain or not, a massive flood can cause severe damage. As floodwaters rise within the house, so does the extent of the destruction. The National Flood Insurance Program reports that even an inch (2.5 cm) of floodwater can result in $7,800 in repair costs. Warped paneling and flooring become detached from their foundations, while furniture and appliances have little chance of surviving undamaged. Over time, mildew develops in the damp environment.

In cases of rapid flash flooding, it may seem impossible to prepare for the rising waters. However, floods that develop more slowly, such as the one that struck Fargo, N.D., in the spring of 2009, allow for a bit more preparation. Yet, as the situation in Fargo showed, icy conditions may limit the ability to carry out emergency measures.

Elevating or relocating your house as a flood protection measure can be expensive and time-consuming. Alternatively, with minimal maintenance, proper landscaping, and a few buckets of waterproof sealant, you can transform your home into a fortress against floodwaters.

Flood Protection from the Outside

Before taking steps to prevent indoor flooding, walk around your house after a rainstorm. Observe where the largest puddles form in the yard and how far they are from the house. The closer water gathers to the foundation, the higher the risk of flooding.

A simple way to direct water away from your home is by keeping gutters clear. This also helps reduce the water pooling on your roof, which could cause long-term structural damage. If you don't have gutters, consider installing a drainage system around the house's perimeter [source: O'Neil].

Downspouts that channel water from gutters to the ground should be kept free of debris as well. The goal is for the pipes to direct rainwater at least 10 feet (3 meters) from the foundation to prevent it from soaking into the soil and reaching the structure [source: O'Neil].

Once the gutters and downspouts are ready, evaluate your yard's landscape. Does the yard slope gently away from the house, or does it sit at the bottom of a decline like a bowl? Especially if you reside in a floodplain, your lawn should have some grading to channel water away from the house. This involves adding soil around the foundation to create a downward slope. Check local regulations regarding regrading before starting any work.

For those with a green thumb, be mindful of your flower or vegetable garden's location. If you water a large garden plot regularly, ensure the excess water doesn't flow toward the house. You can prevent this by grading the garden area to optimize water drainage.

With the yard now set up for flood safety, it's time to focus on the interior.

Flood Protection from the Inside

The strength and volume of floodwaters are often powerful enough to carry away people, vehicles, and even collapse buildings. When the pressure exerted by floodwaters on the outside of a house exceeds the pressure inside, walls can buckle, and foundations can crumble. To prevent this, there are two main methods of protecting a house from flooding, based on its construction.

When considering methods to prevent floodwaters from entering a home, dry floodproofing is the most common solution that comes to mind. Dry floodproofing involves entirely blocking water from entering the house, typically by applying waterproof sealants or plastic sheeting to the foundation [source: Kane County Division of Environmental Management]. Additionally, doors and windows below the floodplain elevation must be sealed to further protect the house.

Dry floodproofing isn't suitable for every home, as hydrostatic pressure from rising water can cause severe external damage. Therefore, homes built on concrete slabs without basements or cellars are the ideal candidates for this method. Brick houses are better suited than wood-sided ones, as they can withstand greater pressure [source: Parker]. However, the Federal Emergency Management Agency (FEMA) states that most homes will succumb to flooding if the water reaches over 3 feet (0.9 meters).

Wet floodproofing, on the other hand, permits some surface water to enter the house. This might seem counterintuitive, but it can reduce overall damage by equalizing the hydrostatic pressure both inside and outside the house [source: FEMA]. This approach is ideal for homes with basements. Inside, appliances like washers, water heaters, and furnaces should be elevated above the expected flood level [source: Kane County Division of Environmental Management]. Concrete block walls and bare flooring minimize the loss of valuable items if floodwaters do enter.

Basement sump pumps can protect the foundation from water damage. Located in a sump pit, these pumps collect groundwater surrounding the house and direct it away through drainage pipes. In some areas, local regulations require homes to have sump pumps. In emergencies, external barriers can also prevent floodwaters from entering. Barriers such as cement flood walls or makeshift levees built with sandbags can effectively stop water from approaching the house. Vulnerable doors and windows can be shielded with plywood, metal, or thick plastic to offer additional protection.

Each year, floods destroy thousands of buildings, possessions, and irreplaceable items. With proper planning and preparation, however, your home doesn't have to be a casualty in this annual wave of loss.